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Document and Entity Information - shares	9 Months Ended
Sep. 30, 2018	Oct. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q3
Trading Symbol	NBIX
Entity Registrant Name	NEUROCRINE BIOSCIENCES INC
Entity Central Index Key	0000914475
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		90,682,182

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 195,734	$ 254,712
Short-term investments, available for sale	439,609	261,217
Accounts receivable	54,097	31,127
Inventory	6,054	1,024
Other current assets	18,900	6,839
Total current assets	714,394	554,919
Property and equipment, net	28,618	10,811
Long-term investments, available for sale	185,257	247,361
Restricted cash	5,477	4,500
Total assets	933,746	817,591
Current liabilities:
Accounts payable and accrued liabilities	72,022	53,520
Current portion of convertible senior notes	383,647	0
Other current liabilities	731	906
Total current liabilities	456,400	54,426
Deferred gain on sale of real estate	7,495	8,043
Deferred revenue	10,231	10,231
Deferred rent	12,107	3,135
Convertible senior notes	0	369,618
Total liabilities	486,233	445,453
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized; no shares issued and outstanding	0	0
Common stock, $0.001 par value; 220,000,000 shares authorized; issued and outstanding shares were 90,673,214 as of September 30, 2018 and 88,793,903 as of December 31, 2017	91	89
Additional paid-in capital	1,645,311	1,572,765
Accumulated other comprehensive loss	(2,056)	(1,850)
Accumulated deficit	(1,195,833)	(1,198,866)
Total stockholders’ equity	447,513	372,138
Total liabilities and stockholders’ equity	$ 933,746	$ 817,591

Condensed Consolidated Statements of Operations And Comprehensive Income (Loss) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues:
Revenues	$ 151,757	$ 60,774	$ 319,748	$ 67,109
Operating expenses:
Cost of sales	1,551	433	3,355	494
Research and development	35,482	22,463	121,417	96,213
Sales, general and administrative	60,401	43,873	179,952	113,597
Total operating expenses	97,434	66,769	304,724	210,304
Income (loss) from operations	54,323	(5,995)	15,024	(143,195)
Other (expense) income:
Interest expense	(7,672)	(7,337)	(22,767)	(12,104)
Investment income and other, net	4,113	2,207	10,776	5,863
Total other expense, net	(3,559)	(5,130)	(11,991)	(6,241)
Net income (loss)	$ 50,764	$ (11,125)	$ 3,033	$ (149,436)
Net income (loss) per common share:
Basic	$ 0.56	$ (0.13)	$ 0.03	$ (1.70)
Diluted	$ 0.52	$ (0.13)	$ 0.03	$ (1.70)
Shares used in the calculation of net income (loss) per common share:
Basic	90,555	88,325	90,064	87,894
Diluted	96,798	88,325	95,272	87,894
Other comprehensive income (loss):
Net income (loss)	$ 50,764	$ (11,125)	$ 3,033	$ (149,436)
Net unrealized gain (loss) on available-for-sale securities	753	179	(206)	(216)
Comprehensive income (loss)	51,517	(10,946)	2,827	(149,652)
Product sales, net
Revenues:
Revenues	111,291	45,774	279,282	52,109
Collaboration revenue
Revenues:
Revenues	$ 40,466	$ 15,000	$ 40,466	$ 15,000

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (loss)	$ 3,033	$ (149,436)
Reconciliation of net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	2,749	1,694
Amortization of debt discount	13,040	6,755
Amortization of debt issuance costs	989	526
Amortization of premiums on investments	1,436	1,202
Non-cash share-based compensation expense	44,800	29,070
Other	(482)	(1,261)
Change in operating assets and liabilities:
Accounts receivable	(22,970)	(29,818)
Inventory	(3,907)	(242)
Reimbursements for tenant improvements	3,657	0
Other current assets	(6,837)	(4,315)
Accounts payable and accrued liabilities	15,577	11,107
Other current liabilities	(175)	(188)
Net cash provided by (used in) operating activities	50,910	(134,906)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of investments	(329,289)	(444,538)
Sales and maturities of investments	211,402	257,235
Purchases of property and equipment	(18,802)	(4,563)
Proceeds from sales of property and equipment	30	7
Net cash used in investing activities	(136,659)	(191,859)
CASH FLOWS FROM FINANCING ACTIVITIES
Issuance of common stock	27,748	8,265
Proceeds from issuance of convertible senior notes, net	0	502,781
Net cash provided by financing activities	27,748	511,046
Net (decrease) increase in cash, cash equivalents and restricted cash	(58,001)	184,281
Cash, cash equivalents and restricted cash at beginning of the period	259,212	88,150
Cash, cash equivalents and restricted cash at end of the period	201,211	272,431
SUPPLEMENTAL DISCLOSURE
Cash paid for interest	5,822	0
Non-cash capital expenditures	$ 1,802	$ 0

ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES	9 Months Ended
ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES	Sep. 30, 2018
Accounting Policies [Abstract]
ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES	1. ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES Description of Business. Neurocrine Biosciences, Inc. (the Company or Neurocrine) was incorporated in California in 1992 and reincorporated in Delaware in 1996. The Company discovers, develops and commercializes innovative and life-changing pharmaceuticals, in diseases with high unmet medical needs, through its novel research and development (R&D) platform, focused on neurological and endocrine related disorders. The Company discovered, developed and markets INGREZZA^® (valbenazine), the first United States Food and Drug Administration (FDA)-approved product indicated for the treatment of adults with tardive dyskinesia (TD), a movement disorder. Discovered and developed through Phase II clinical trials by Neurocrine, ORILISSA^TM (elagolix), the first FDA-approved oral medication for the management of endometriosis associated with moderate to severe pain in over a decade, is marketed by AbbVie Inc. (AbbVie) as part of a collaboration to develop and commercialize elagolix for women’s health. Neurocrine’s clinical development programs include opicapone as an adjunctive therapy to levodopa/DOPA decarboxylase inhibitors in Parkinson's disease patients, elagolix for uterine fibroids with AbbVie, valbenazine for the treatment of Tourette syndrome, NBI-74788 for the treatment of congenital adrenal hyperplasia (CAH), a vesicular monoamine transporter 2 (VMAT2) inhibitor and first-in-class central nervous system (CNS) compound with potential use in the treatment of neurologic and psychiatric disorders. Basis of Presentation. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (GAAP) for interim financial information and with the instructions of the Securities and Exchange Commission (SEC) on Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and disclosures required by GAAP for complete financial statements. In the opinion of management, the condensed consolidated financial statements include all adjustments necessary, which are of a normal and recurring nature, for the fair presentation of the Company’s financial position and of the results of operations and cash flows for the periods presented. The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. These financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto for the year ended December 31, 2017 included in the Company’s Annual Report on Form 10-K filed with the SEC. The results of operations for the interim period shown in this report are not necessarily indicative of the results that may be expected for any other interim period or for the full year. The balance sheet at December 31, 2017, has been derived from the audited financial statements at that date, but does not include all of the information and footnotes required by GAAP for complete financial statements. Reclassifications. Certain amounts in prior year periods have been reclassified to conform with the presentation adopted in current year periods. Impact of Recently Issued Accounting Standards. In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-09, “Revenue from Contracts with Customers (Topic 606)”, which supersedes all existing revenue recognition requirements, including most industry-specific guidance. This new standard amends the guidance for the recognition of revenue from contracts with customers to transfer goods and services. The FASB subsequently issued additional, clarifying standards to address issues arising from implementation of the new revenue recognition standard. The Company adopted this new standard as of January 1, 2018, using the modified retrospective method. The adoption of the new revenue standard did not change the Company’s revenue recognition. As the Company did not identify any accounting changes that impacted the amount of reported revenues with respect to product revenues, or revenue from collaboration and license agreements, no adjustment to retained earnings was required upon adoption. See below for discussion of the Company’s revenue recognition policy. In February 2016, the FASB issued ASU 2016-02, “Leases”. This update amends the current accounting guidance for lease transactions. Under the new guidance, a lessee will be required to recognize both assets and liabilities for any leases in excess of twelve months. Additionally, certain qualitative and quantitative disclosures will also be required in the financial statements. The Company is required to adopt this new guidance beginning in 2019 and early adoption is permitted. As of September 30, 2018, the Company was in the process of analyzing its lease contracts and the potential impact the standard may have on its condensed consolidated financial statements and related disclosures. The Company is also in the process of evaluating potential changes to its controls to support lease accounting and the related disclosures under the new standard. Based on management’s preliminary analysis, the Company anticipates the adoption of this guidance will have a material impact on the Company’s Condensed Consolidated Balance Sheets due to the requirement to recognize lease right-of-use (ROU) assets and corresponding liabilities, primarily relating to leases of office space. In November 2016, the FASB issued ASU 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash”, which clarifies the presentation of restricted cash and restricted cash equivalents in the statements of cash flows. Under this ASU, restricted cash and restricted cash equivalents are included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts presented on the statements of cash flows. This ASU is intended to reduce diversity in practice in the classification and presentation of changes in restricted cash on the statement of cash flows. This ASU requires that the statement of cash flows explain the change in total cash and equivalents and amounts generally described as restricted cash or restricted cash equivalents when reconciling the beginning-of-period and end-of-period total amounts. This ASU also requires a reconciliation between the total of cash and equivalents and restricted cash presented on the statement of cash flows and the cash and equivalents balance presented on the balance sheet. This amended guidance was retrospectively adopted on January 1, 2018 and required that cash, cash equivalents and restricted cash reported on the Condensed Consolidated Statements of Cash Flows now includes restricted cash of $5.5 million and $4.6 million as of September 30, 2018 and 2017, respectively, as well as previously reported cash and cash equivalents. In June 2018, the FASB issued ASU 2018-07, “Compensation-Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting”, which expands the scope of Topic 718 to include share based payment transactions for acquiring goods and services from nonemployees and applies to all share-based payment transactions in which a grantor acquires goods or services to be used or consumed in a grantor’s own operations by issuing share-based payment awards. Topic 718 does not apply to share-based payments used to effectively provide (1) financing to the issuer or (2) awards granted in conjunction with selling goods or services to customers as part of a contract accounted for under Topic 606. This update is effective for public business entities for fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. The Company is evaluating the effect that this update will have on its condensed consolidated financial statements and related disclosures. Use of Estimates. The preparation of the condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and the accompanying notes. Estimates for revenues, cost of sales, inventory, and R&D expenses are evaluated on an ongoing basis and are based on historical experience or other relevant assumptions that management believes to be reasonable under the circumstances. Actual results could differ from those estimates. Inventory. Inventory is stated at the lower of cost or estimated net realizable value. The Company currently uses actual costing to determine the cost basis for its inventory. Inventory is valued on a first-in, first-out basis and consists primarily of third-party manufacturing costs. The Company capitalizes inventory costs associated with its products upon regulatory approval when, based on management’s judgment, future commercialization is considered probable and the future economic benefit is expected to be realized; otherwise, such costs are expensed. Prior to FDA approval of INGREZZA, all costs related to its manufacture were charged to R&D expense in the period incurred. Historically, the Company’s physical inventory included active pharmaceutical product (API) that had been produced prior to FDA approval of INGREZZA and accordingly had no cost basis as the cost associated with producing this material was expensed rather than capitalized in accordance with GAAP. Costs associated with the manufacture of bulk drug product, finished bottling, and other labeling activities that occurred post FDA approval are included in the inventory value at September 30, 2018 and December 31, 2017. The Company reduces its inventory to net realizable value for potential excess, dated, or obsolete inventory based on an analysis of forecasted demand compared to quantities on hand and any firm purchase orders, as well as product shelf life. To date, the Company has determined that such reserves are not required. Cost of Sales. Cost of sales includes third-party manufacturing, transportation, freight, and indirect overhead costs associated with the manufacture and distribution of INGREZZA, sales-based license costs on AbbVie net sales of ORILISSA, as defined in the agreement with the party to which the Company pays such costs, and period costs resulting from certain inventory manufacturing services, inventory adjustment charges, and manufacturing variances. A significant portion of the costs associated with the manufacture of INGREZZA sold to date was expensed as R&D prior to the FDA’s approval and is therefore excluded from cost of sales during this period. Accounts Receivable. Accounts receivable are recorded net of customer allowances for prompt payment discounts, chargebacks, and any allowance for doubtful accounts. The Company estimates the allowance for doubtful accounts based on actual payment patterns of its customers and individual customer circumstances. To date, the Company has determined that an allowance for doubtful accounts is not required. Research and Development Expenses. R&D expenses consist primarily of salaries, payroll taxes, employee benefits, and share-based compensation charges for those individuals involved in ongoing R&D efforts; as well as scientific contractor fees, development milestones from in-licensed collaboration agreements, preclinical and clinical trial costs, R&D facilities costs, laboratory supply costs, and depreciation of scientific equipment. All such costs are charged to R&D expense as incurred. These expenses result from the Company’s independent R&D efforts as well as efforts associated with collaborations, in-licenses, and third-party funded research arrangements. The Company reviews and accrues clinical trial expenses based on work performed, which relies on estimates of total costs incurred based on patient enrollment, completion of patient studies, and other events. The Company follows this method since reasonably dependable estimates of the costs applicable to various stages of a research agreement or clinical trial can be made. Accrued clinical costs are subject to revisions as trials progress. Revisions are charged to expense in the period in which the facts that give rise to the revision become known. Revenue Recognition. Effective January 1, 2018, the Company adopted Topic 606, using the modified retrospective method. As the Company did not identify any revenue recognition differences when comparing the revenue recognition criteria under Topic 606 to the requirements under previous criteria with respect to product revenues, or revenue from collaboration and license agreements, no cumulative effect adjustment to retained earnings was necessary upon adoption. See the Company’s Annual Report on Form 10-K filed with the SEC for the year ended December 31, 2017, for a detailed description of the Company’s accounting policy under Topic 605 which was effective for periods prior to January 1, 2018. Had the Company continued to account for revenue recognition under Topic 605, the Company’s revenues for the first three and nine months of 2018 would not have differed by a significant amount from those reported under Topic 606. Under Topic 606, the Company recognizes revenues when its customers (as defined below) obtain control of its products or services in an amount that reflects the consideration it expects to receive from its customers in exchange for those products or services. To determine revenue recognition, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the Company satisfies the performance obligation. The Company only applies the five-step model to contracts when it is probable that the Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of Topic 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. If the consideration promised under the contract includes a variable amount, the Company must estimate the consideration it expects to receive for transferring the good or service to the customer. There are two methods for determining the amount of variable consideration: (i) the expected value method, which is the sum of probability-weighted amounts in a range of possible consideration amounts, and (ii) the mostly likely amount method, which identifies the single most likely amount in a range of possible consideration amounts. Performance milestone payments represent a form of variable consideration. Product Sales, Net. The Company’s product sales consist of U.S. sales of INGREZZA. INGREZZA was approved by the FDA on April 11, 2017 and the Company commenced shipments of INGREZZA to select pharmacies (SPs) and a select distributor (SD), or collectively, its customers, in late April 2017. The SPs dispense product to a patient based on the fulfillment of a prescription and the SD sells product to government facilities, long-term care pharmacies, or in-patient hospital pharmacies. The Company’s agreements with the SPs and SD provide for transfer of title to the product at the time the product is delivered to the SP or SD. In addition, except for limited circumstances, the SPs and SD have no right of product return to the Company. Product sales are recognized when the customer obtains control of the Company’s product, typically upon delivery to the customer. Revenue from product sales is recorded at the net sales price (transaction price), which includes an estimate of variable consideration for which reserves are established and which results from contractual discounts, returns, chargebacks, rebates, co-pay assistance, and other allowances relating to the Company’s sales of its products. These reserves are based on the amounts earned or to be claimed on the related sales and are classified as reductions of accounts receivable (if the amount is payable to the customer) or a current liability (if the amount is payable to a party other than a customer). Where appropriate, these estimates take into consideration a range of possible outcomes that are probability-weighted for relevant factors such as the Company’s historical experience, current contractual and statutory requirements, specific known market events and trends, industry data, and forecasted customer buying and payment patterns. Overall, these reserves reflect the Company’s best estimates of the amount of consideration to which it is entitled based on the terms of the contract. The amount of variable consideration that is included in the transaction price may be constrained and is included in the net sales price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. Actual amounts of consideration ultimately received may differ from the Company’s estimates. If actual results in the future vary from the Company’s estimates, the Company will adjust these estimates, which would affect net product revenue and earnings in the period such variances become known. The following are the Company’s significant categories of sales discounts and allowances: Trade Discounts and Allowances: The Company generally provides customers with discounts that include prompt payment discounts, discounts for providing sales data, and other off-invoice discounts that are explicitly stated in the Company’s contracts and are recorded as a reduction of revenue in the period the related product revenue is recognized. Product Returns: The Company offers customers limited product return rights for damages and shipment errors provided it is within a very limited period after the original shipping date as set forth in the applicable individual distribution agreement. The Company does not allow product returns for product that has been dispensed to a patient or for drug expiration. The Company receives real-time shipping reports and inventory reports from the customers and has the ability to control the amount of product that is sold to the customers. Product returns to date have not been significant and the Company has not considered it necessary to record a reserve for product returns. Government Rebates: The Company is subject to discount obligations under state Medicaid programs and Medicare prescription drug coverage gap program. The Company estimates its Medicaid and Medicare prescription drug coverage gap rebates based upon a range of possible outcomes that are probability-weighted for the estimated payor mix. These reserves are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability that is included in accrued expenses on the Condensed Consolidated Balance Sheet. The Company’s liability for these rebates consists of invoices received for claims from prior quarters that have not been paid or for which an invoice has not yet been received, estimates of claims for the current quarter, and estimated future claims that will be made for product that has been recognized as revenue, but remains in the distribution channel inventories at the end of each reporting period. Provider Chargebacks and Discounts: Chargebacks for fees and discounts to providers represent the estimated obligations resulting from contractual commitments to sell products to qualified healthcare providers at prices lower than the list prices charged to customers who directly purchase the product from the Company. Customers charge the Company for the difference between what they pay for the product and the ultimate selling price to the qualified healthcare providers. These reserves are established in the same period that the related revenue is recognized, resulting in a reduction of product revenue and accounts receivable. Chargeback amounts are generally determined at the time of resale to the qualified healthcare provider by customers, and the Company generally issues credits for such amounts following the customer’s notification to the Company of the resale. Reserves for chargebacks consist of credits that the Company expects to issue for units that remain in the distribution channel inventories at each reporting period end that the Company expects will be sold to qualified healthcare providers. Co-Payment Assistance: The Company offers co-payment assistance to commercially insured patients meeting certain eligibility requirements. The calculation of the accrual for co-pay assistance is based on an estimate of claims and the cost per claim that the Company expects to receive associated with product that has been recognized as revenue, but remains in the distribution channel inventories at the end of each reporting period. Shipping and handling costs related to the Company’s product sales are included in selling, general and administrative expenses. Collaboration and Other Revenue. The Company enters into collaboration and licensing agreements that are within the scope of Topic 606, under which it licenses certain rights to its product candidates to third-parties. The terms of these arrangements typically include payment to the Company of one or more of the following: non-refundable, up-front license fees; development, regulatory and commercial milestone payments; payments for manufacturing supply services; and royalties on net sales of licensed products. In determining the appropriate amount of revenue to be recognized as the Company fulfills its obligations under each of its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. As part of the accounting for these arrangements, the Company must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company uses key assumptions to determine the stand-alone selling price, which may include forecasted revenues, development timelines, reimbursement rates for personnel costs, discount rates and probabilities of technical and regulatory success. Royalty Revenue: For arrangements that include sales-based royalties, including milestone payments based on the level of sales of licensed products, and where the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). Sales-based royalties for ORILISSA are calculated as a percentage of AbbVie net sales as defined in the Company’s agreement with AbbVie. Each quarterly period, sales-based royalties are recorded based on estimated quarterly net sales of ORILISSA. Differences between actual results and estimated amounts are adjusted for in the period in which they become known, which typically follows the quarterly period in which the estimate was made. Licenses of Intellectual Property: If the license to the Company’s intellectual property embedded within a collaboration and/or licensing arrangement is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from non-refundable, up-front fees allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The Company receives payments from its licensees based on billing schedules established in each agreement. Up-front payments and fees are recorded as deferred revenue upon receipt, or when due, and may require deferral of revenue recognition to a future period until the Company performs its obligations under these arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional. Milestone Payments: At the inception of each arrangement that includes development, commercialization and regulatory milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The transaction price is then allocated to each performance obligation on a relative stand-alone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such development milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect milestone and license fees revenues and earnings in the period of adjustment. Manufacturing Supply Services: Arrangements that include a promise for future supply of drug substance or drug product for either clinical development or commercial supply at the licensee’s discretion are generally considered as options. The Company assesses if these options provide a material right to the licensee and if so, they are accounted for as separate performance obligations.

SIGNIFICANT COLLABORATION AND LICENSING AGREEMENTS	9 Months Ended
SIGNIFICANT COLLABORATION AND LICENSING AGREEMENTS	Sep. 30, 2018
Text Block [Abstract]
SIGNIFICANT COLLABORATION AND LICENSING AGREEMENTS	2. SIGNIFICANT COLLABORATION AND LICENSING AGREEMENTS Mitsubishi Tanabe Pharma Corporation (Mitsubishi Tanabe). During 2015, the Company entered into a collaboration and license agreement with Mitsubishi Tanabe for the development and commercialization of INGREZZA for movement disorders in Japan and other select Asian markets. Mitsubishi Tanabe made an up-front license fee of $30 million and has agreed to make payments up to $85 million in development and commercialization event-based payments, payments for the manufacture of pharmaceutical products, and royalties on product sales in select territories in Asia. Under the terms of the agreement, Mitsubishi Tanabe is responsible for all third-party development, marketing and commercialization costs in Japan and other select Asian markets. The Company will be entitled to a percentage of sales of INGREZZA in Japan and other select Asian markets for the longer of ten years or the life of the related patent rights. Under the terms of the Company’s agreement with Mitsubishi Tanabe, the collaboration effort between the parties to advance INGREZZA towards commercialization in Japan and other select Asian markets is governed by a joint steering committee and joint development committee with representatives from both the Company and Mitsubishi Tanabe. There are no performance, cancellation, termination or refund provisions in the agreement that would have a material financial consequence to the Company. The Company does not directly control when event-based payments will be achieved or when royalty payments will begin. Mitsubishi Tanabe may terminate the agreement at its discretion upon 180 days’ written notice to the Company. In such event, all INGREZZA product rights for Japan and other select Asian markets would revert to the Company. The Company assessed this arrangement in accordance with Topic 606 and identified the following material promises under the agreement: (i) INGREZZA technology license and existing know-how; and (ii) development activities to initiate a clinical trial of INGREZZA for Huntington’s chorea, at an estimated cost of approximately $12 million, should Mitsubishi Tanabe request. The Company has the option to participate on the joint steering committee, but since participation is at the Company’s option it was deemed to not be a material promise. The option for Mitsubishi Tanabe to engage the Company to manufacture and supply pharmaceutical products, not at a discount, was not considered a material right and therefore not a material promise. Based on these assessments, the Company identified the license and the development activities as the only performance obligations at the inception of the agreement, which were both deemed to be distinct. Under the terms of the agreement, in order to evaluate the appropriate transaction price, the Company determined that the up-front amount constituted the entirety of the consideration to be included in the transaction price and to be allocated to the performance obligations based on the Company’s best estimate of their relative stand-alone selling prices. For the license, the stand-alone selling price was calculated using an income approach model and included the following key assumptions: the development timeline, revenue forecast, discount rate and probabilities of technical and regulatory success. The relative selling price of the Company’s development activities to initiate a clinical trial of INGREZZA for Huntington’s chorea was based on an assessment of costs to perform the study, based upon the peer company analysis for similar studies. The Company believes that a change in the assumptions used to determine its stand-alone selling price for the license most likely would not have a significant effect on the allocation of consideration received (or receivable) to the performance obligations. At execution, the transaction price included only the $30 million up-front consideration received. None of the development or regulatory milestones has been included in the transaction price, as all milestone amounts were fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of the milestones is outside the control of the Company and contingent upon success in future clinical trials and the licensee’s efforts. Any consideration related to sales-based milestones (including royalties) will be recognized when the related sales occur as they were determined to relate predominantly to the license granted to Mitsubishi Tanabe and therefore have also been excluded from the transaction price. The Company will re-evaluate the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. To date, the Company has recognized revenue under this agreement of $19.8 million associated with the delivery of a technology license and existing know-how, and $15 million in development event-based payments resulting from Mitsubishi Tanabe’s initiation of Phase II/III development of INGREZZA in TD in Asia. In accordance with our continuing performance obligations, $10.2 million of the $30 million up-front payment is being deferred and recognized in future periods. Under the terms of the agreement, there is no general obligation to return the up-front payment for any non-contingent deliverable. No revenue was recognized under the Mitsubishi Tanabe agreement for the three and nine months ended September 30, 2018. During the third quarter of 2017, Mitsubishi Tanabe initiated a pivotal trial of INGREZZA in Asia for the treatment of tardive dyskinesia which generated a $15 million milestone. AbbVie Inc. (AbbVie). In June 2010, the Company announced an exclusive worldwide collaboration with AbbVie, to develop and commercialize elagolix and all next-generation GnRH antagonists (collectively, GnRH Compounds) for women’s and men’s health. AbbVie made an upfront payment of $75 million and has agreed to make additional development and regulatory event-based payments of up to $480 million, of which $115 million has been earned as of September 30, 2018, and up to an additional $50 million in commercial event-based payments. Under the terms of the agreement, AbbVie is responsible for all third-party development, marketing and commercialization costs. The Company will be entitled to a percentage of worldwide sales of GnRH Compounds for the longer of ten years or the life of the related patent rights. AbbVie may terminate the collaboration at its discretion upon 180 days’ written notice to the Company. In such event, the Company would be entitled to specified payments for ongoing clinical development and related activities and all GnRH Compound product rights would revert to the Company. The Company has evaluated the terms of this agreement under Topic 606 and has determined that there is one performance obligation, the exclusive worldwide license with rights to develop, manufacture and commercialize elagolix. At execution, the transaction price included only the $75 million up-front consideration received. None of the development or regulatory milestones has been included in the transaction price, as all milestone amounts were fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of the milestones is outside the control of the Company and contingent upon success in future clinical trials and the licensee’s efforts. Any consideration related to sales-based milestones (including royalties) will be recognized when the related sales occur as they were determined to relate predominantly to the license granted to AbbVie and therefore have also been excluded from the transaction price. The Company will re-evaluate the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. On July 24, 2018, AbbVie received approval from the FDA for ORILISSA for the management of moderate to severe endometriosis pain in women, resulting in the achievement of a $40 million event-based milestone, which the Company recognized as revenue in the third quarter of 2018. During 2017, event-based revenue of $30 million was recognized based on AbbVie’s NDA submission for elagolix in endometriosis being accepted by the FDA. During 2016, event-based revenue of $15 million was recognized related to AbbVie’s initiation of Phase III development of elagolix in uterine fibroids. The Company also recognized sales-based royalties on AbbVie net sales of ORILISSA of $0.5 million in the third quarter of 2018. No revenue was recognized under the AbbVie agreement for the nine months ended September 30, 2017. BIAL – Portela & CA, S.A. (BIAL). In February 2017, the Company entered into an exclusive license agreement with BIAL for the development and commercialization of opicapone for the treatment of human diseases and conditions, including Parkinson’s disease, in the United States and Canada. Under the terms of the agreement, the Company is responsible for the management and cost of all opicapone development and commercialization activities in the United States and Canada. Under the terms of the agreement, the Company paid BIAL an upfront license fee of $30 million, which was expensed in the first quarter of 2017 as in-process research and development. In addition, during the first quarter of 2018, the FDA provided guidance on the regulatory path forward to support an NDA for opicapone for Parkinson’s Disease, in which the FDA did not request that the Company conduct an additional Phase III study, resulting in a $10 million event-based milestone payment to BIAL. The Company may also be required to pay up to an additional $105 million in milestone payments associated with the regulatory approval and net sales of products containing opicapone. Prior to FDA approval of opicapone, the Company may be required to pay up to an additional $10 million in milestones based on certain regulatory and clinical results and FDA acceptance of the Company’s NDA submission for opicapone. Upon commercialization of opicapone, the Company has agreed to determine certain annual sales forecasts. In the event that the Company fails to meet the minimum sales requirements for a particular year, the Company will be required to pay BIAL an amount corresponding to the difference between the actual net sales and the minimum sales requirements for such year, and if the Company fails to meet the minimum sales requirements for any two years, BIAL may terminate the agreement. The agreement, unless terminated earlier, will continue on a licensed product-by-licensed product and country-by-country basis until a generic product in respect of such licensed product under the agreement is sold in a country and sales of such generic product are greater than a specified percentage of total sales of such licensed product in such country. Upon the Company’s written request prior to the estimated expiration of the term in respect of a licensed product, the parties shall negotiate a good faith continuation of BIAL’s supply of such licensed product after the term. After the term, and if BIAL is not supplying a certain licensed product, the Company shall pay BIAL a trademark royalty based on the net sales of such licensed product. Either party may terminate the agreement earlier if the other party materially breaches the agreement and does not cure the breach within a specified notice period, or upon the other party’s insolvency. BIAL may terminate the agreement if the Company fails to use commercially reasonable efforts or fails to submit an NDA for a licensed product by a specified date or under certain circumstances involving a change of control of the Company. In certain circumstances where BIAL elects to terminate the agreement in connection with the Company’s change of control, BIAL shall pay the Company a termination fee. The Company may terminate the agreement at any time for any reason upon six months written notice to BIAL if prior to the first NDA approval in the United States, and upon nine months written notice to BIAL if such notice is given after the first NDA approval in the United States. If the Company’s termination request occurs prior to the first NDA approval in the United States, the Company will have to pay BIAL a termination fee except under certain conditions specified in the agreement.

INVESTMENTS

9 Months Ended

Sep. 30, 2018

Investments Schedule [Abstract]

INVESTMENTS

3. INVESTMENTS

Available-for-sale securities are carried at fair value, with the unrealized gains and losses reported in comprehensive income (loss). The amortized cost of debt securities in this category is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion are included in investment income. Realized gains and losses and declines in value judged to be other-than-temporary, if any, on available-for-sale securities are included in investment income or expense. The cost of securities sold is based on the specific identification method. Interest and dividends on securities classified as available-for-sale are included in investment income.

Investments consist of the following (in thousands):

	September 30, 2018		December 31, 2017
Commercial paper	$	42,465	$	75,362
Corporate debt securities		541,694		414,815
Securities of government sponsored entities		40,707		18,401
Total investments	$	624,866	$	508,578

The following is a summary of investments classified as available-for-sale securities (in thousands):

	Contractual Maturity (in years)	Amortized Cost		Gross Unrealized Gains⁽¹⁾		Gross Unrealized Losses⁽¹⁾			Aggregate Estimated Fair Value
September 30, 2018:
Classified as current assets:
Commercial paper	Less than 1	$	42,514	$	—	$	(49	)	$	42,465
Corporate debt securities	Less than 1		387,627		6		(1,407	)		386,226
Securities of government-sponsored entities	Less than 1		11,000		—		(82	)		10,918
Total short-term available-for-sale securities		$	441,141	$	6	$	(1,538	)	$	439,609
Classified as non-current assets:
Corporate debt securities	1 to 2	$	155,935	$	1	$	(468	)	$	155,468
Securities of government-sponsored entities	1 to 2		29,846		—		(57	)		29,789
Total long-term available-for-sale securities		$	185,781	$	1	$	(525	)	$	185,257
December 31, 2017:
Classified as current assets:
Commercial paper	Less than 1	$	75,396	$	1	$	(35	)	$	75,362
Corporate debt securities	Less than 1		178,776		—		(400	)		178,376
Securities of government-sponsored entities	Less than 1		7,503		—		(24	)		7,479
Total short-term available-for-sale securities		$	261,675	$	1	$	(459	)	$	261,217
Classified as non-current assets:
Corporate debt securities	1 to 2	$	237,749	$	—	$	(1,310	)	$	236,439
Securities of government-sponsored entities	1 to 2		11,004		—		(82	)		10,922
Total long-term available-for-sale securities		$	248,753	$	—	$	(1,392	)	$	247,361

(1)	Unrealized gains and losses are included in other comprehensive income (loss).

The following table presents gross unrealized losses and fair value for those available-for-sale investments that were in an unrealized loss position as of September 30, 2018 and December 31, 2017, aggregated by investment category and length of time that individual securities have been in a continuous loss position (in thousands):

	Less Than 12 Months					12 Months or Greater					Total
	Estimated Fair Value		Unrealized Losses			Estimated Fair Value		Unrealized Losses			Estimated Fair Value		Unrealized Losses
September 30, 2018:
Commercial paper	$	32,634	$	(49	)	$	—	$	—		$	32,634	$	(49	)
Corporate debt securities		317,733		(931	)		188,998		(944	)		506,731		(1,875	)
Securities of government-sponsored entities		29,789		(57	)		10,918		(82	)		40,707		(139	)
Total	$	380,156	$	(1,037	)	$	199,916	$	(1,026	)	$	580,072	$	(2,063	)
December 31, 2017:
Commercial paper	$	62,602	$	(35	)	$	—	$	—		$	62,602	$	(35	)
Corporate debt securities		386,728		(1,660	)		28,087		(50	)		414,815		(1,710	)
Securities of government-sponsored entities		10,922		(82	)		7,479		(24	)		18,401		(106	)
Total	$	460,252	$	(1,777	)	$	35,566	$	(74	)	$	495,818	$	(1,851	)

The primary objective of the Company’s investment portfolio is to enhance overall returns in an efficient manner while maintaining safety of principal, prudent levels of liquidity and acceptable levels of risk. The Company’s investment policy limits interest-bearing security investments to certain types of instruments issued by institutions with primarily investment grade credit ratings and places restrictions on maturities and concentration by asset class and issuer.

The Company reviews the available-for-sale investments for other-than-temporary declines in fair value below cost basis each quarter and whenever events or changes in circumstances indicate that the cost basis of an asset may not be recoverable. This evaluation is based on a number of factors, including the length of time and the extent to which the fair value has been below the cost basis and adverse conditions related specifically to the security, including any changes to the credit rating of the security, and the intent to sell, or whether the Company will more likely than not be required to sell the security before recovery of its amortized cost basis. The assessment of whether a security is other-than-temporarily impaired could change in the future due to new developments or changes in assumptions related to any particular security. As of September 30, 2018 and December 31, 2017, the Company believed the cost bases for available-for-sale investments were recoverable in all material respects.

FAIR VALUE MEASUREMENTS

9 Months Ended

Sep. 30, 2018

Fair Value Disclosures [Abstract]

FAIR VALUE MEASUREMENTS

4. FAIR VALUE MEASUREMENTS

Fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, a three-tier fair value hierarchy has been established, which prioritizes the inputs used in measuring fair value as follows:

Level 1:

Observable inputs such as quoted prices in active markets;

Level 2:

Inputs include quoted prices for similar instruments in active markets and/or quoted prices for identical or similar instruments in markets that are not active near the measurement date; and

Level 3:

Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions.

The Company classifies its cash equivalents and available for sale investments within Level 1 or Level 2. The fair value of the Company’s investment grade corporate debt securities is determined using proprietary valuation models and analytical tools. These valuation models and analytical tools use market pricing or prices for similar instruments that are both objective and publicly available, including matrix pricing or reported trades, benchmark yields, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids and/or offers. The Company did not reclassify any investments between levels in the fair value hierarchy during the three and nine months ended September 30, 2018.

The Company’s assets which were measured at fair value on a recurring basis as of September 30, 2018 and December 31, 2017, were determined using the inputs described above and are as follows (in millions):

				Fair Value Measurements Using
	Carrying Value			Quoted Prices in Active Markets for Identical Assets (Level 1)			Significant Other Observable Inputs (Level 2)			Significant Unobservable Inputs (Level 3)
September 30, 2018:
Classified as current assets:
Cash and money market funds	$	195.7		$	195.7		$	—		$	—
Commercial paper		42.5			—			42.5			—
Securities of government-sponsored entities		10.9			—			10.9			—
Corporate debt securities		386.2			—			386.2			—
Subtotal		635.3			195.7			439.6			—
Classified as long-term assets:
Cash and money market funds		1.5			1.5			—			—
Certificates of deposit		4.0			4.0			—			—
Securities of government-sponsored entities		29.8			—			29.8			—
Corporate debt securities		155.5			—			155.5			—
Total		826.1			201.2			624.9			—
Less cash, cash equivalents and restricted cash		(201.2	)		(201.2	)		—			—
Total investments	$	624.9		$	—		$	624.9		$	—
December 31, 2017:
Classified as current assets:
Cash and money market funds	$	170.2		$	170.2		$	—		$	—
Commercial paper		159.9			—			159.9			—
Securities of government-sponsored entities		7.5			—			7.5			—
Corporate debt securities		178.4			—			178.4			—
Subtotal		516.0			170.2			345.8			—
Classified as long-term assets:
Cash and money market funds		1.5			1.5			—			—
Certificates of deposit		3.0			3.0			—			—
Securities of government-sponsored entities		10.9			—			10.9			—
Corporate debt securities		236.4			—			236.4			—
Total		767.8			174.7			593.1			—
Less cash, cash equivalents and restricted cash		(259.2	)		(174.6	)		(84.6	)		—
Total investments	$	508.6		$	0.1		$	508.5		$	—

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

CONVERTIBLE SENIOR NOTES

9 Months Ended

Sep. 30, 2018

Debt Disclosure [Abstract]

CONVERTIBLE SENIOR NOTES

6. CONVERTIBLE SENIOR NOTES

On May 2, 2017, the Company completed a private placement of $517.5 million in aggregate principal amount of 2.25% convertible senior notes due 2024 (2024 Notes) and entered into an indenture agreement (2024 Indenture) with respect to the 2024 Notes. The 2024 Notes accrue interest at a fixed rate of 2.25% per year, payable semiannually in arrears on May 15 and November 15 of each year, beginning on November 15, 2017. The 2024 Notes mature on May 15, 2024. The net proceeds from the issuance of the 2024 Notes were approximately $502.8 million, after deducting commissions and the offering expenses payable by the Company.

Holders of the 2024 Notes may convert the 2024 Notes at any time prior to the close of business on the business day immediately preceding May 15, 2024, only under the following circumstances:

(i)

during any calendar quarter commencing after the calendar quarter ending on September 30, 2017 (and only during such calendar quarter), if the last reported sale price of the Company’s common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than 130% of the conversion price on each applicable trading day;

(ii)

during the five business-day period immediately after any five consecutive trading-day period (the ‘‘measurement period’’) in which the trading price (as defined in the 2024 Indenture) per $1,000 principal amount of the 2024 Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of the Company’s common stock and the conversion rate on each such trading day;

(iii)

upon the occurrence of specified corporate events, including a merger or a sale of all or substantially all of the Company’s assets; or

(iv)

if the Company calls the 2024 Notes for redemption, until the close of business on the business day immediately preceding the redemption date.

On or after January 15, 2024, until the close of business on the scheduled trading day immediately preceding May 15, 2024, holders may convert their 2024 Notes at any time.

As the conditional conversion feature described under (i) above had been triggered as of September 30, 2018, holders of the 2024 Notes may convert the 2024 Notes at any time during the period beginning on October 1, 2018 and ending at the close of business on December 31, 2018. Accordingly, the 2024 Notes have been classified as a current liability on the Company’s Condensed Consolidated Balance Sheet as of September 30, 2018. The future conditional convertibility of the 2024 Notes will be monitored at each quarterly reporting date and analyzed dependent upon market prices of the Company’s common stock during the prescribed measurement periods.

Upon conversion, holders will receive the principal amount of their 2024 Notes and any excess conversion value, calculated based on the per share volume-weighted average price for each of the 30 consecutive trading days during the observation period (as more fully described in the 2024 Indenture). For both the principal and excess conversion value, holders may receive cash, shares of the Company’s common stock or a combination of cash and shares of the Company’s common stock, at the Company’s option.

It is the Company’s intent and policy to settle conversions through combination settlement, which essentially involves repayment of an amount of cash equal to the “principal portion” and delivery of the “share amount” in excess of the principal portion in shares of common stock or cash. In general, for each $1,000 in principal, the “principal portion” of cash upon settlement is defined as the lesser of $1,000, and the conversion value during the 25-day observation period as described in the indenture for the notes. The conversion value is the sum of the daily conversion value which is the product of the effective conversion rate divided by 25 days and the daily volume weighted average price (VWAP) of the Company’s common stock. The “share amount” is the cumulative “daily share amount” during the observation period, which is calculated by dividing the daily VWAP into the difference between the daily conversion value (i.e., conversion rate x daily VWAP) and $1,000.

The initial conversion rate for the 2024 Notes is 13.1711 shares of common stock per $1,000 principal amount, which is equivalent to an initial conversion price of approximately $75.92 per share of the Company’s common stock. At the initial conversion rate, settlement of the 2024 Notes for shares of the Company’s common stock would approximate 6.8 million shares. The conversion rate will be subject to adjustment in some events but will not be adjusted for any accrued and unpaid interest. The initial conversion price of the 2024 Notes represented a premium of approximately 42.5% to the closing sale price of $53.28 per share of the Company’s common stock on the NASDAQ Global Select Market on April 26, 2017, the date that the Company priced the private offering of the 2024 Notes.

In the event of conversion, holders would forgo all future interest payments, any unpaid accrued interest and the possibility of further stock price appreciation. Upon the receipt of conversion requests, the settlement of the 2024 Notes will be paid pursuant to the terms of the 2024 Indenture. In the event that all of the 2024 Notes are converted, the Company would be required to repay the $517.5 million in principal value and any conversion premium in any combination of cash and shares of its common stock (at the Company’s option).

Prior to May 15, 2021, the Company may not redeem the 2024 Notes. On or after May 15, 2021, the Company may redeem for cash all or part of the 2024 Notes if the last reported sale price (as defined in the 2024 Indenture) of the Company’s common stock has been at least 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading-day period ending on, and including, the trading day immediately before the date which the Company provides notice of redemption. The redemption price will equal the sum of (i) 100% of the principal amount of the 2024 Notes being redeemed, plus (ii) accrued and unpaid interest, including additional interest, if any, to, but excluding, the redemption date. No sinking fund is provided for the 2024 Notes.

If the Company undergoes a fundamental change, as defined in the 2024 Indenture, subject to certain conditions, holders of the 2024 Notes may require the Company to repurchase for cash all or part of their 2024 Notes at a repurchase price equal to 100% of the principal amount of the 2024 Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date. In addition, if a ‘‘make-whole fundamental change’’ (as defined in the 2024 Indenture) occurs prior to January 15, 2024, the Company will, in certain circumstances, increase the conversion rate for a holder who elects to convert its notes in connection with the make-whole fundamental change.

The 2024 Notes are the Company’s general unsecured obligations that rank senior in right of payment to all of its indebtedness that is expressly subordinated in right of payment to the 2024 Notes, and equal in right of payment to the Company’s unsecured indebtedness.

The fair value of the 2024 Notes is estimated utilizing market quotations from an over-the-counter trading market. As of September 30, 2018, the fair value approximated 171% of the face principal amount of the 2024 Notes.

Under current accounting guidance, an entity must separately account for the liability and equity components of convertible debt instruments (such as the 2024 Notes) that may be settled entirely or partially in cash upon conversion in a manner that reflects the issuer’s economic interest cost. The liability component of the instrument was valued in a manner that reflects the market interest rate for a similar nonconvertible instrument at the date of issuance. The initial carrying value of the liability component of $368.3 million was calculated using a 7.5% assumed borrowing rate. The equity component of $149.2 million, representing the conversion option, was determined by deducting the fair value of the liability component from the par value of the 2024 Notes and is recorded in additional paid-in capital on the consolidated balance sheet at the issuance date. That equity component is treated as a discount on the liability component of the 2024 Notes, which is amortized over the seven-year term of the 2024 Notes using the effective interest rate method. The equity component is not re-measured as long as it continues to meet the conditions for equity classification.

The Company allocated the total transaction costs of approximately $14.7 million related to the issuance of the 2024 Notes to the liability and equity components of the 2024 Notes based on their relative values. Transaction costs attributable to the liability component are amortized to interest expense over the seven-year term of the 2024 Notes, and transaction costs attributable to the equity component are netted with the equity component in stockholders’ equity.

The 2024 Notes do not contain any financial or operating covenants or any restrictions on the payment of dividends, the issuance of other indebtedness or the issuance or repurchase of securities by the Company. The 2024 Indenture contains customary events of default with respect to the 2024 Notes, including that upon certain events of default, 100% of the principal and accrued and unpaid interest on the 2024 Notes will automatically become due and payable.

Debt, net of discounts and deferred financing costs at September 30, 2018 and December 31, 2017, consisted of the following (in thousands):

	September 30, 2018			December 31, 2017
Principal	$	517,500		$	517,500
Deferred financing costs		(8,663	)		(9,652	)
Debt discount, net		(125,190	)		(138,230	)
Net carrying amount	$	383,647		$	369,618

NET INCOME (LOSS) PER SHARE

9 Months Ended

Sep. 30, 2018

Earnings Per Share [Abstract]

NET INCOME (LOSS) PER SHARE

7. NET INCOME (LOSS) PER SHARE

Basic net income per share is computed using the weighted average number of common shares outstanding during the period. Diluted net income per share is computed using the weighted average number of common and potentially dilutive shares outstanding during the period, including the potentially dilutive shares resulting from the conversion of the 2024 Notes, and excluding the effect of stock options and restricted stock outstanding for periods when their effect is anti-dilutive, using the treasury stock method.

Convertible debt instruments that may be settled entirely or partly in cash (such as the 2024 Notes) may, in certain circumstances where the borrower has the ability and intent to settle in cash, be accounted for under the treasury stock method. The Company issued the 2024 Notes with a combination settlement feature, which it has the ability and intent to use upon conversion of the notes, to settle the principal amount of debt for cash and the excess of the principal portion in shares of the Company’s common stock. As a result, of the approximately 6.8 million shares underlying the 2024 Notes, only the shares required to settle the excess of the principal portion would be considered dilutive under the treasury stock method. Further, approximately 0.3 million restricted stock units (RSUs) with performance-based vesting requirements (PRSUs) have been excluded from the calculation of diluted net income per share as the performance condition has not been achieved. In loss periods, basic net loss per share and diluted net loss per share are identical because the otherwise dilutive potential common shares become anti-dilutive and are therefore excluded.

Net income (loss) per share was calculated as follows (in thousands, except per share data):

	Three Months Ended September 30,					Nine Months Ended September 30,
	2018		2017			2018		2017
Net income (loss) - basic and diluted	$	50,764	$	(11,125	)	$	3,033	$	(149,436	)
Weighted-average common shares outstanding:
Basic		90,555		88,325			90,064		87,894
Effect of dilutive securities:
Employee stock purchase program		7		—			2		—
Stock options		3,352		—			3,322		—
Restricted stock		629		—			558		—
2024 Notes		2,255		—			1,326		—
Diluted		96,798		88,325			95,272		87,894
Net income (loss) per share:
Basic	$	0.56	$	(0.13	)	$	0.03	$	(1.70	)
Diluted	$	0.52	$	(0.13	)	$	0.03	$	(1.70	)

Shares which have been excluded from diluted per share amounts because their effect would have been anti-dilutive include the following (in thousands):

Three Months Ended

September 30,

Nine Months Ended

September 30,

2018

2017

2018

2017

Stock options and restricted stock

882

7,862

823

7,898

SHARE-BASED COMPENSATION

9 Months Ended

Sep. 30, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

SHARE-BASED COMPENSATION

8. SHARE-BASED COMPENSATION

The compensation expense related to the Company’s share-based compensation arrangements has been included in the Condensed Consolidated Statements of Comprehensive Income (Loss) as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
General and administrative	$	8,371	$	6,531	$	23,199	$	18,234
Research and development		4,699		3,672		21,601		10,836
Total share-based compensation expense	$	13,070	$	10,203	$	44,800	$	29,070

The fair value of equity instruments that vest based on continued employee service is recognized and amortized on a straight-line basis over the requisite service period. No expense is recognized for PRSUs until the performance condition is probable of being achieved. During the nine months ended September 30, 2018, the Company recorded a non-recurring share-based compensation charge of $7.7 million related to the modification of certain options and RSUs.

As of September 30, 2018, total unrecognized estimated compensation cost related to non-vested stock options and non-vested RSUs, that vest over a given service period, granted prior to that date was $60.7 million and $57.3 million, respectively, which is expected to be recognized over a weighted average period of approximately 2.5 and 2.2 years, respectively. Additionally, the Company has approximately 0.3 million PRSUs outstanding. As of September 30, 2018, total unrecognized estimated compensation cost related to these PRSUs was $19.7 million and will be recognized over the expected performance period once the achievement of performance conditions becomes probable.

During the nine months ended September 30, 2018 and 2017, stock options to purchase approximately 1.5 million and 1.0 million shares of the Company’s common stock were exercised, respectively. The cash received by the Company from stock option exercises during the nine months ended September 30, 2018 and 2017 was approximately $27.7 million and $8.3 million, respectively. The Company also issued approximately 0.4 million and 0.3 million shares of common stock pursuant to the vesting of RSUs during each of the nine months ended September 30, 2018 and 2017.

Stock Option Assumptions

The Company granted stock options to purchase approximately 1.0 million and 1.6 million shares of the Company’s common stock during the nine months ended September 30, 2018 and 2017, respectively. These stock options generally vest monthly over a four-year period. The exercise price of all stock options granted during the nine months ended September 30, 2018 and 2017 was equal to the closing price of the Company’s common stock on the date of grant. The estimated fair value of each stock option granted was determined on the date of grant using the Black-Scholes option-pricing model with the following weighted-average assumptions for the stock option grants:

	Three Months Ended September 30,		Nine Months Ended September 30,
	2018	2017	2018	2017
Risk-free interest rate	2.8%	1.8%	2.5%	2.0%
Expected volatility of common stock	53.7%	59.6%	59.9%	58.2%
Dividend yield	0.0%	0.0%	0.0%	0.0%
Expected option term	4.5 years	5.0 years	4.8 years	5.7 years

The Black-Scholes option-pricing model incorporates various and highly sensitive assumptions including expected volatility, expected term and interest rates. The expected volatility is based on the historical volatility of the Company’s common stock over the most recent period commensurate with the estimated expected term of the Company’s stock options. The expected option term is estimated based on historical experience as well as the status of the employee. For example, directors and officers have a longer expected option term than all other employees. The risk-free rate for periods within the contractual life of the option is based upon observed interest rates appropriate for the expected term of the Company’s employee stock options. The Company has never declared or paid dividends and has no plans to do so in the foreseeable future. For the nine months ended September 30, 2018 and 2017, share-based compensation expense related to stock options was $28.2 million and $18.7 million, respectively.

Restricted Stock Units

During the nine months ended September 30, 2018 and 2017, the Company granted approximately 0.5 million and 0.6 million RSUs, respectively, which vest annually over a four-year period. Additionally, the Company granted approximately 0.2 million PRSUs during the nine months ended September 30, 2018, which vest based on the achievement of pre-defined Company-specific performance criteria and expire approximately four to five years from the grant date. Expense recognition for PRSUs commences when attainment of the performance-based criteria is probable. The fair value of RSUs and PRSUs is estimated based on the closing sale price of the Company’s common stock on the date of grant. For the nine months ended September 30, 2018 and 2017, the aggregate share-based compensation expense related to RSUs and PRSUs was $16.5 million and $10.4 million, respectively.

ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Description of Business	Description of Business. Neurocrine Biosciences, Inc. (the Company or Neurocrine) was incorporated in California in 1992 and reincorporated in Delaware in 1996. The Company discovers, develops and commercializes innovative and life-changing pharmaceuticals, in diseases with high unmet medical needs, through its novel research and development (R&D) platform, focused on neurological and endocrine related disorders. The Company discovered, developed and markets INGREZZA^® (valbenazine), the first United States Food and Drug Administration (FDA)-approved product indicated for the treatment of adults with tardive dyskinesia (TD), a movement disorder. Discovered and developed through Phase II clinical trials by Neurocrine, ORILISSA^TM (elagolix), the first FDA-approved oral medication for the management of endometriosis associated with moderate to severe pain in over a decade, is marketed by AbbVie Inc. (AbbVie) as part of a collaboration to develop and commercialize elagolix for women’s health. Neurocrine’s clinical development programs include opicapone as an adjunctive therapy to levodopa/DOPA decarboxylase inhibitors in Parkinson's disease patients, elagolix for uterine fibroids with AbbVie, valbenazine for the treatment of Tourette syndrome, NBI-74788 for the treatment of congenital adrenal hyperplasia (CAH), a vesicular monoamine transporter 2 (VMAT2) inhibitor and first-in-class central nervous system (CNS) compound with potential use in the treatment of neurologic and psychiatric disorders.
Basis of Presentation	Basis of Presentation. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (GAAP) for interim financial information and with the instructions of the Securities and Exchange Commission (SEC) on Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and disclosures required by GAAP for complete financial statements. In the opinion of management, the condensed consolidated financial statements include all adjustments necessary, which are of a normal and recurring nature, for the fair presentation of the Company’s financial position and of the results of operations and cash flows for the periods presented. The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. These financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto for the year ended December 31, 2017 included in the Company’s Annual Report on Form 10-K filed with the SEC. The results of operations for the interim period shown in this report are not necessarily indicative of the results that may be expected for any other interim period or for the full year. The balance sheet at December 31, 2017, has been derived from the audited financial statements at that date, but does not include all of the information and footnotes required by GAAP for complete financial statements.
Reclassifications	Reclassifications. Certain amounts in prior year periods have been reclassified to conform with the presentation adopted in current year periods.
Impact of Recently Issued Accounting Standards	Impact of Recently Issued Accounting Standards. In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-09, “Revenue from Contracts with Customers (Topic 606)”, which supersedes all existing revenue recognition requirements, including most industry-specific guidance. This new standard amends the guidance for the recognition of revenue from contracts with customers to transfer goods and services. The FASB subsequently issued additional, clarifying standards to address issues arising from implementation of the new revenue recognition standard. The Company adopted this new standard as of January 1, 2018, using the modified retrospective method. The adoption of the new revenue standard did not change the Company’s revenue recognition. As the Company did not identify any accounting changes that impacted the amount of reported revenues with respect to product revenues, or revenue from collaboration and license agreements, no adjustment to retained earnings was required upon adoption. See below for discussion of the Company’s revenue recognition policy. In February 2016, the FASB issued ASU 2016-02, “Leases”. This update amends the current accounting guidance for lease transactions. Under the new guidance, a lessee will be required to recognize both assets and liabilities for any leases in excess of twelve months. Additionally, certain qualitative and quantitative disclosures will also be required in the financial statements. The Company is required to adopt this new guidance beginning in 2019 and early adoption is permitted. As of September 30, 2018, the Company was in the process of analyzing its lease contracts and the potential impact the standard may have on its condensed consolidated financial statements and related disclosures. The Company is also in the process of evaluating potential changes to its controls to support lease accounting and the related disclosures under the new standard. Based on management’s preliminary analysis, the Company anticipates the adoption of this guidance will have a material impact on the Company’s Condensed Consolidated Balance Sheets due to the requirement to recognize lease right-of-use (ROU) assets and corresponding liabilities, primarily relating to leases of office space. In November 2016, the FASB issued ASU 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash”, which clarifies the presentation of restricted cash and restricted cash equivalents in the statements of cash flows. Under this ASU, restricted cash and restricted cash equivalents are included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts presented on the statements of cash flows. This ASU is intended to reduce diversity in practice in the classification and presentation of changes in restricted cash on the statement of cash flows. This ASU requires that the statement of cash flows explain the change in total cash and equivalents and amounts generally described as restricted cash or restricted cash equivalents when reconciling the beginning-of-period and end-of-period total amounts. This ASU also requires a reconciliation between the total of cash and equivalents and restricted cash presented on the statement of cash flows and the cash and equivalents balance presented on the balance sheet. This amended guidance was retrospectively adopted on January 1, 2018 and required that cash, cash equivalents and restricted cash reported on the Condensed Consolidated Statements of Cash Flows now includes restricted cash of $5.5 million and $4.6 million as of September 30, 2018 and 2017, respectively, as well as previously reported cash and cash equivalents. In June 2018, the FASB issued ASU 2018-07, “Compensation-Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting”, which expands the scope of Topic 718 to include share based payment transactions for acquiring goods and services from nonemployees and applies to all share-based payment transactions in which a grantor acquires goods or services to be used or consumed in a grantor’s own operations by issuing share-based payment awards. Topic 718 does not apply to share-based payments used to effectively provide (1) financing to the issuer or (2) awards granted in conjunction with selling goods or services to customers as part of a contract accounted for under Topic 606. This update is effective for public business entities for fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. The Company is evaluating the effect that this update will have on its condensed consolidated financial statements and related disclosures.
Use of Estimates	Use of Estimates. The preparation of the condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and the accompanying notes. Estimates for revenues, cost of sales, inventory, and R&D expenses are evaluated on an ongoing basis and are based on historical experience or other relevant assumptions that management believes to be reasonable under the circumstances. Actual results could differ from those estimates.
Inventory	Inventory. Inventory is stated at the lower of cost or estimated net realizable value. The Company currently uses actual costing to determine the cost basis for its inventory. Inventory is valued on a first-in, first-out basis and consists primarily of third-party manufacturing costs. The Company capitalizes inventory costs associated with its products upon regulatory approval when, based on management’s judgment, future commercialization is considered probable and the future economic benefit is expected to be realized; otherwise, such costs are expensed. Prior to FDA approval of INGREZZA, all costs related to its manufacture were charged to R&D expense in the period incurred. Historically, the Company’s physical inventory included active pharmaceutical product (API) that had been produced prior to FDA approval of INGREZZA and accordingly had no cost basis as the cost associated with producing this material was expensed rather than capitalized in accordance with GAAP. Costs associated with the manufacture of bulk drug product, finished bottling, and other labeling activities that occurred post FDA approval are included in the inventory value at September 30, 2018 and December 31, 2017. The Company reduces its inventory to net realizable value for potential excess, dated, or obsolete inventory based on an analysis of forecasted demand compared to quantities on hand and any firm purchase orders, as well as product shelf life. To date, the Company has determined that such reserves are not required.
Cost of Sales	Cost of Sales. Cost of sales includes third-party manufacturing, transportation, freight, and indirect overhead costs associated with the manufacture and distribution of INGREZZA, sales-based license costs on AbbVie net sales of ORILISSA, as defined in the agreement with the party to which the Company pays such costs, and period costs resulting from certain inventory manufacturing services, inventory adjustment charges, and manufacturing variances. A significant portion of the costs associated with the manufacture of INGREZZA sold to date was expensed as R&D prior to the FDA’s approval and is therefore excluded from cost of sales during this period.
Accounts Receivable	Accounts Receivable. Accounts receivable are recorded net of customer allowances for prompt payment discounts, chargebacks, and any allowance for doubtful accounts. The Company estimates the allowance for doubtful accounts based on actual payment patterns of its customers and individual customer circumstances. To date, the Company has determined that an allowance for doubtful accounts is not required.
Research and Development Expenses	Research and Development Expenses. R&D expenses consist primarily of salaries, payroll taxes, employee benefits, and share-based compensation charges for those individuals involved in ongoing R&D efforts; as well as scientific contractor fees, development milestones from in-licensed collaboration agreements, preclinical and clinical trial costs, R&D facilities costs, laboratory supply costs, and depreciation of scientific equipment. All such costs are charged to R&D expense as incurred. These expenses result from the Company’s independent R&D efforts as well as efforts associated with collaborations, in-licenses, and third-party funded research arrangements. The Company reviews and accrues clinical trial expenses based on work performed, which relies on estimates of total costs incurred based on patient enrollment, completion of patient studies, and other events. The Company follows this method since reasonably dependable estimates of the costs applicable to various stages of a research agreement or clinical trial can be made. Accrued clinical costs are subject to revisions as trials progress. Revisions are charged to expense in the period in which the facts that give rise to the revision become known.
Revenue Recognition	Revenue Recognition. Effective January 1, 2018, the Company adopted Topic 606, using the modified retrospective method. As the Company did not identify any revenue recognition differences when comparing the revenue recognition criteria under Topic 606 to the requirements under previous criteria with respect to product revenues, or revenue from collaboration and license agreements, no cumulative effect adjustment to retained earnings was necessary upon adoption. See the Company’s Annual Report on Form 10-K filed with the SEC for the year ended December 31, 2017, for a detailed description of the Company’s accounting policy under Topic 605 which was effective for periods prior to January 1, 2018. Had the Company continued to account for revenue recognition under Topic 605, the Company’s revenues for the first three and nine months of 2018 would not have differed by a significant amount from those reported under Topic 606. Under Topic 606, the Company recognizes revenues when its customers (as defined below) obtain control of its products or services in an amount that reflects the consideration it expects to receive from its customers in exchange for those products or services. To determine revenue recognition, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the Company satisfies the performance obligation. The Company only applies the five-step model to contracts when it is probable that the Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of Topic 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. If the consideration promised under the contract includes a variable amount, the Company must estimate the consideration it expects to receive for transferring the good or service to the customer. There are two methods for determining the amount of variable consideration: (i) the expected value method, which is the sum of probability-weighted amounts in a range of possible consideration amounts, and (ii) the mostly likely amount method, which identifies the single most likely amount in a range of possible consideration amounts. Performance milestone payments represent a form of variable consideration.
Product Sales, Net	Product Sales, Net. The Company’s product sales consist of U.S. sales of INGREZZA. INGREZZA was approved by the FDA on April 11, 2017 and the Company commenced shipments of INGREZZA to select pharmacies (SPs) and a select distributor (SD), or collectively, its customers, in late April 2017. The SPs dispense product to a patient based on the fulfillment of a prescription and the SD sells product to government facilities, long-term care pharmacies, or in-patient hospital pharmacies. The Company’s agreements with the SPs and SD provide for transfer of title to the product at the time the product is delivered to the SP or SD. In addition, except for limited circumstances, the SPs and SD have no right of product return to the Company. Product sales are recognized when the customer obtains control of the Company’s product, typically upon delivery to the customer. Revenue from product sales is recorded at the net sales price (transaction price), which includes an estimate of variable consideration for which reserves are established and which results from contractual discounts, returns, chargebacks, rebates, co-pay assistance, and other allowances relating to the Company’s sales of its products. These reserves are based on the amounts earned or to be claimed on the related sales and are classified as reductions of accounts receivable (if the amount is payable to the customer) or a current liability (if the amount is payable to a party other than a customer). Where appropriate, these estimates take into consideration a range of possible outcomes that are probability-weighted for relevant factors such as the Company’s historical experience, current contractual and statutory requirements, specific known market events and trends, industry data, and forecasted customer buying and payment patterns. Overall, these reserves reflect the Company’s best estimates of the amount of consideration to which it is entitled based on the terms of the contract. The amount of variable consideration that is included in the transaction price may be constrained and is included in the net sales price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. Actual amounts of consideration ultimately received may differ from the Company’s estimates. If actual results in the future vary from the Company’s estimates, the Company will adjust these estimates, which would affect net product revenue and earnings in the period such variances become known. The following are the Company’s significant categories of sales discounts and allowances: Trade Discounts and Allowances: The Company generally provides customers with discounts that include prompt payment discounts, discounts for providing sales data, and other off-invoice discounts that are explicitly stated in the Company’s contracts and are recorded as a reduction of revenue in the period the related product revenue is recognized. Product Returns: The Company offers customers limited product return rights for damages and shipment errors provided it is within a very limited period after the original shipping date as set forth in the applicable individual distribution agreement. The Company does not allow product returns for product that has been dispensed to a patient or for drug expiration. The Company receives real-time shipping reports and inventory reports from the customers and has the ability to control the amount of product that is sold to the customers. Product returns to date have not been significant and the Company has not considered it necessary to record a reserve for product returns. Government Rebates: The Company is subject to discount obligations under state Medicaid programs and Medicare prescription drug coverage gap program. The Company estimates its Medicaid and Medicare prescription drug coverage gap rebates based upon a range of possible outcomes that are probability-weighted for the estimated payor mix. These reserves are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability that is included in accrued expenses on the Condensed Consolidated Balance Sheet. The Company’s liability for these rebates consists of invoices received for claims from prior quarters that have not been paid or for which an invoice has not yet been received, estimates of claims for the current quarter, and estimated future claims that will be made for product that has been recognized as revenue, but remains in the distribution channel inventories at the end of each reporting period. Provider Chargebacks and Discounts: Chargebacks for fees and discounts to providers represent the estimated obligations resulting from contractual commitments to sell products to qualified healthcare providers at prices lower than the list prices charged to customers who directly purchase the product from the Company. Customers charge the Company for the difference between what they pay for the product and the ultimate selling price to the qualified healthcare providers. These reserves are established in the same period that the related revenue is recognized, resulting in a reduction of product revenue and accounts receivable. Chargeback amounts are generally determined at the time of resale to the qualified healthcare provider by customers, and the Company generally issues credits for such amounts following the customer’s notification to the Company of the resale. Reserves for chargebacks consist of credits that the Company expects to issue for units that remain in the distribution channel inventories at each reporting period end that the Company expects will be sold to qualified healthcare providers. Co-Payment Assistance: The Company offers co-payment assistance to commercially insured patients meeting certain eligibility requirements. The calculation of the accrual for co-pay assistance is based on an estimate of claims and the cost per claim that the Company expects to receive associated with product that has been recognized as revenue, but remains in the distribution channel inventories at the end of each reporting period. Shipping and handling costs related to the Company’s product sales are included in selling, general and administrative expenses.
Collaboration and Other Revenue	Collaboration and Other Revenue. The Company enters into collaboration and licensing agreements that are within the scope of Topic 606, under which it licenses certain rights to its product candidates to third-parties. The terms of these arrangements typically include payment to the Company of one or more of the following: non-refundable, up-front license fees; development, regulatory and commercial milestone payments; payments for manufacturing supply services; and royalties on net sales of licensed products. In determining the appropriate amount of revenue to be recognized as the Company fulfills its obligations under each of its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. As part of the accounting for these arrangements, the Company must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company uses key assumptions to determine the stand-alone selling price, which may include forecasted revenues, development timelines, reimbursement rates for personnel costs, discount rates and probabilities of technical and regulatory success. Royalty Revenue: For arrangements that include sales-based royalties, including milestone payments based on the level of sales of licensed products, and where the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). Sales-based royalties for ORILISSA are calculated as a percentage of AbbVie net sales as defined in the Company’s agreement with AbbVie. Each quarterly period, sales-based royalties are recorded based on estimated quarterly net sales of ORILISSA. Differences between actual results and estimated amounts are adjusted for in the period in which they become known, which typically follows the quarterly period in which the estimate was made. Licenses of Intellectual Property: If the license to the Company’s intellectual property embedded within a collaboration and/or licensing arrangement is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from non-refundable, up-front fees allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The Company receives payments from its licensees based on billing schedules established in each agreement. Up-front payments and fees are recorded as deferred revenue upon receipt, or when due, and may require deferral of revenue recognition to a future period until the Company performs its obligations under these arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional. Milestone Payments: At the inception of each arrangement that includes development, commercialization and regulatory milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The transaction price is then allocated to each performance obligation on a relative stand-alone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such development milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect milestone and license fees revenues and earnings in the period of adjustment. Manufacturing Supply Services: Arrangements that include a promise for future supply of drug substance or drug product for either clinical development or commercial supply at the licensee’s discretion are generally considered as options. The Company assesses if these options provide a material right to the licensee and if so, they are accounted for as separate performance obligations.

INVESTMENTS (Tables)

9 Months Ended

Sep. 30, 2018

Investments Schedule [Abstract]

Investments

Investments consist of the following (in thousands):

	September 30, 2018		December 31, 2017
Commercial paper	$	42,465	$	75,362
Corporate debt securities		541,694		414,815
Securities of government sponsored entities		40,707		18,401
Total investments	$	624,866	$	508,578

Summary of Investments Classified as Available-For-Sale Securities

The following is a summary of investments classified as available-for-sale securities (in thousands):

	Contractual Maturity (in years)	Amortized Cost		Gross Unrealized Gains⁽¹⁾		Gross Unrealized Losses⁽¹⁾			Aggregate Estimated Fair Value
September 30, 2018:
Classified as current assets:
Commercial paper	Less than 1	$	42,514	$	—	$	(49	)	$	42,465
Corporate debt securities	Less than 1		387,627		6		(1,407	)		386,226
Securities of government-sponsored entities	Less than 1		11,000		—		(82	)		10,918
Total short-term available-for-sale securities		$	441,141	$	6	$	(1,538	)	$	439,609
Classified as non-current assets:
Corporate debt securities	1 to 2	$	155,935	$	1	$	(468	)	$	155,468
Securities of government-sponsored entities	1 to 2		29,846		—		(57	)		29,789
Total long-term available-for-sale securities		$	185,781	$	1	$	(525	)	$	185,257
December 31, 2017:
Classified as current assets:
Commercial paper	Less than 1	$	75,396	$	1	$	(35	)	$	75,362
Corporate debt securities	Less than 1		178,776		—		(400	)		178,376
Securities of government-sponsored entities	Less than 1		7,503		—		(24	)		7,479
Total short-term available-for-sale securities		$	261,675	$	1	$	(459	)	$	261,217
Classified as non-current assets:
Corporate debt securities	1 to 2	$	237,749	$	—	$	(1,310	)	$	236,439
Securities of government-sponsored entities	1 to 2		11,004		—		(82	)		10,922
Total long-term available-for-sale securities		$	248,753	$	—	$	(1,392	)	$	247,361

(1)	Unrealized gains and losses are included in other comprehensive income (loss).

Gross Unrealized Losses and Fair Value Available-For-Sale Investments in Unrealized Loss Position

	Less Than 12 Months					12 Months or Greater					Total
	Estimated Fair Value		Unrealized Losses			Estimated Fair Value		Unrealized Losses			Estimated Fair Value		Unrealized Losses
September 30, 2018:
Commercial paper	$	32,634	$	(49	)	$	—	$	—		$	32,634	$	(49	)
Corporate debt securities		317,733		(931	)		188,998		(944	)		506,731		(1,875	)
Securities of government-sponsored entities		29,789		(57	)		10,918		(82	)		40,707		(139	)
Total	$	380,156	$	(1,037	)	$	199,916	$	(1,026	)	$	580,072	$	(2,063	)
December 31, 2017:
Commercial paper	$	62,602	$	(35	)	$	—	$	—		$	62,602	$	(35	)
Corporate debt securities		386,728		(1,660	)		28,087		(50	)		414,815		(1,710	)
Securities of government-sponsored entities		10,922		(82	)		7,479		(24	)		18,401		(106	)
Total	$	460,252	$	(1,777	)	$	35,566	$	(74	)	$	495,818	$	(1,851	)

FAIR VALUE MEASUREMENTS (Tables)

9 Months Ended

Sep. 30, 2018

Fair Value Disclosures [Abstract]

Assets Measured at Fair Value on Recurring Basis

				Fair Value Measurements Using
	Carrying Value			Quoted Prices in Active Markets for Identical Assets (Level 1)			Significant Other Observable Inputs (Level 2)			Significant Unobservable Inputs (Level 3)
September 30, 2018:
Classified as current assets:
Cash and money market funds	$	195.7		$	195.7		$	—		$	—
Commercial paper		42.5			—			42.5			—
Securities of government-sponsored entities		10.9			—			10.9			—
Corporate debt securities		386.2			—			386.2			—
Subtotal		635.3			195.7			439.6			—
Classified as long-term assets:
Cash and money market funds		1.5			1.5			—			—
Certificates of deposit		4.0			4.0			—			—
Securities of government-sponsored entities		29.8			—			29.8			—
Corporate debt securities		155.5			—			155.5			—
Total		826.1			201.2			624.9			—
Less cash, cash equivalents and restricted cash		(201.2	)		(201.2	)		—			—
Total investments	$	624.9		$	—		$	624.9		$	—
December 31, 2017:
Classified as current assets:
Cash and money market funds	$	170.2		$	170.2		$	—		$	—
Commercial paper		159.9			—			159.9			—
Securities of government-sponsored entities		7.5			—			7.5			—
Corporate debt securities		178.4			—			178.4			—
Subtotal		516.0			170.2			345.8			—
Classified as long-term assets:
Cash and money market funds		1.5			1.5			—			—
Certificates of deposit		3.0			3.0			—			—
Securities of government-sponsored entities		10.9			—			10.9			—
Corporate debt securities		236.4			—			236.4			—
Total		767.8			174.7			593.1			—
Less cash, cash equivalents and restricted cash		(259.2	)		(174.6	)		(84.6	)		—
Total investments	$	508.6		$	0.1		$	508.5		$	—

NET INCOME (LOSS) PER SHARE (Tables)

9 Months Ended

Sep. 30, 2018

Earnings Per Share [Abstract]

Schedule of Net Income (Loss) Per Share

Net income (loss) per share was calculated as follows (in thousands, except per share data):

	Three Months Ended September 30,					Nine Months Ended September 30,
	2018		2017			2018		2017
Net income (loss) - basic and diluted	$	50,764	$	(11,125	)	$	3,033	$	(149,436	)
Weighted-average common shares outstanding:
Basic		90,555		88,325			90,064		87,894
Effect of dilutive securities:
Employee stock purchase program		7		—			2		—
Stock options		3,352		—			3,322		—
Restricted stock		629		—			558		—
2024 Notes		2,255		—			1,326		—
Diluted		96,798		88,325			95,272		87,894
Net income (loss) per share:
Basic	$	0.56	$	(0.13	)	$	0.03	$	(1.70	)
Diluted	$	0.52	$	(0.13	)	$	0.03	$	(1.70	)

Schedule of Anti-Dilutive Shares Excluded from Diluted Per Share Amounts

Shares which have been excluded from diluted per share amounts because their effect would have been anti-dilutive include the following (in thousands):

Three Months Ended

September 30,

Nine Months Ended

September 30,

2018

2017

2018

2017

Stock options and restricted stock

882

7,862

823

7,898

SHARE-BASED COMPENSATION (Tables)

9 Months Ended

Sep. 30, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Compensation Expenses Related to Share Based Compensation

	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
General and administrative	$	8,371	$	6,531	$	23,199	$	18,234
Research and development		4,699		3,672		21,601		10,836
Total share-based compensation expense	$	13,070	$	10,203	$	44,800	$	29,070

Weighted-Average Assumptions for Stock Option Grants using Black-Scholes Option-Pricing Model

The estimated fair value of each stock option granted was determined on the date of grant using the Black-Scholes option-pricing model with the following weighted-average assumptions for the stock option grants:

	Three Months Ended September 30,		Nine Months Ended September 30,
	2018	2017	2018	2017
Risk-free interest rate	2.8%	1.8%	2.5%	2.0%
Expected volatility of common stock	53.7%	59.6%	59.9%	58.2%
Dividend yield	0.0%	0.0%	0.0%	0.0%
Expected option term	4.5 years	5.0 years	4.8 years	5.7 years

Significant Collaboration and Licensing Agreements - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended			9 Months Ended		12 Months Ended
	Jun. 30, 2010	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jul. 24, 2018
Mitsubishi Tanabe
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front license fees									$ 30,000,000
Collaborative agreement maximum additional payment to receive									85,000,000
Patent rights period					The longer of ten years or the life of the related patent rights.
Collaborative arrangement right description					Under the terms of the Company’s agreement with Mitsubishi Tanabe, the collaboration effort between the parties to advance INGREZZA towards commercialization in Japan and other select Asian markets is governed by a joint steering committee and joint development committee with representatives from both the Company and Mitsubishi Tanabe. There are no performance, cancellation, termination or refund provisions in the agreement that would have a material financial consequence to the Company. The Company does not directly control when event-based payments will be achieved or when royalty payments will begin. Mitsubishi Tanabe may terminate the agreement at its discretion upon 180 days’ written notice to the Company. In such event, all INGREZZA product rights for Japan and other select Asian markets would revert to the Company.
Collaboration termination notice period					180 days
Revenues recognized under collaboration agreement		$ 0	$ 15,000,000		$ 0		$ 15,000,000		19,800,000
Deferred revenues under collaboration									$ 10,200,000
Mitsubishi Tanabe \| Topic 606
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Clinical trial cost					12,000,000
Up-front consideration received					$ 30,000,000
AbbVie
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front license fees	$ 75,000,000
Patent rights period					Ten years or the life of the related patent rights.
Collaborative arrangement right description					The Company will be entitled to a percentage of worldwide sales of GnRH Compounds for the longer of ten years or the life of the related patent rights.
Collaboration termination notice period					180 days
Revenues recognized under collaboration agreement						$ 0	$ 30,000,000	$ 15,000,000
Collaborative arrangement event-based payment amount										$ 40,000,000
Sales-based royalties		500,000
AbbVie \| Development and Regulatory Milestone Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative agreement maximum additional payment to receive		480,000,000			$ 480,000,000
Collaborative agreement payment received					115,000,000
AbbVie \| Commercial Milestone Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative agreement maximum additional payment to receive		50,000,000			50,000,000
AbbVie \| Topic 606
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front consideration received					$ 75,000
B I A L
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front license fees				$ (30,000,000)
License agreement date					Feb. 09, 2017
B I A L \| Event Based Milestones
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payables		10,000,000			$ 10,000,000
B I A L \| Regulatory Approval and Net Sales Milestones
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payables		105,000,000			105,000,000
B I A L \| Regulatory and Clinical Results and FDA Acceptance Milestones
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payables		$ 10,000,000			$ 10,000,000

Convertible Senior Notes - Additional Information (Detail) $ / shares in Units, shares in Millions		9 Months Ended
	May 02, 2017 USD ($)	Sep. 30, 2018 USD ($) d $ / shares shares	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Convertible senior notes principal amount		$ 517,500,000		$ 517,500,000
Proceeds from Senior Convertible Notes		$ 0	$ 502,781,000
2.25% Convertible Senior Notes due 2024
Debt Instrument [Line Items]
Convertible senior notes principal amount	$ 517,500,000
Convertible senior notes interest percentage	2.25%
Convertible senior notes interest rate	2.25%
Convertible senior notes convertible latest date		May 15, 2024
Proceeds from Senior Convertible Notes	$ 502,800,000
Threshold common stock trading days \| d		20
Threshold consecutive common stock trading days \| d		30
Threshold percentage of common stock price trigger		130.00%
Debt instrument conversion obligation number of consecutive business days after consecutive trading day period		5 days
Debt instrument conversion obligation period of consecutive trading days.		5 days
Principal amount on conversion rate		$ 1,000
Minimum percentage of common stock price trigger		98.00%
Debt instrument convertible trading days during observation period		30 days
Conversion Observation Period		25 days
Debt instrument conversion value description		The conversion value is the sum of the daily conversion value which is the product of the effective conversion rate divided by 25 days and the daily volume weighted average price (VWAP) of the Company’s common stock.
Debt instrument conversion share amount description		The “share amount” is the cumulative “daily share amount” during the observation period, which is calculated by dividing the daily VWAP into the difference between the daily conversion value (i.e., conversion rate x daily VWAP) and $1,000.
Convertible senior notes convertible in to shares		0.00131711
Convertible senior notes conversion price \| $ / shares		$ 75.92
Market Price of Common stock \| $ / shares		$ 53.28
Convertible senior note premium		42.50%
Shares issued to settle notes at initial conversion rate \| shares		6.8
Convertible senior notes redemption rate		100.00%
Fair value of convertible senior note as percentage of principal amount		171.00%
Convertible senior note carrying value of the liability component		$ 368,300,000
Convertible senior note assumed borrowing rate		7.50%
Convertible senior note carrying value of the equity component		$ 149,200,000
Convertible senior notes		7 years
Transaction cost related to issuance of convertible senior note		$ 14,700,000
Debt instrument events of default percentage of principal and accrued and unpaid interest due and payable upon default		100.00%

Net Income (Loss) Per Share - Schedule of Net Income (Loss) Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Net income (loss) - basic and diluted	$ 50,764	$ (11,125)	$ 3,033	$ (149,436)
Weighted-average common shares outstanding:
Basic	90,555,000	88,325,000	90,064,000	87,894,000
Effect of dilutive securities:
Employee stock purchase program	7,000	0	2,000	0
Stock options	3,352,000	0	3,322,000	0
Restricted stock	629,000	0	558,000	0
2024 Notes	2,255,000	0	1,326,000	0
Diluted	96,798,000	88,325,000	95,272,000	87,894,000
Net income (loss) per share:
Basic	$ 0.56	$ (0.13)	$ 0.03	$ (1.70)
Diluted	$ 0.52	$ (0.13)	$ 0.03	$ (1.70)

Share-Based Compensation - Additional Information (Detail) - USD ($) $ in Thousands, shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-recurring share-based compensation charge, recorded			$ 7,700
Stock option exercised			1.5	1.0
Cash received from stock option exercises			$ 27,700	$ 8,300
Common stock issued pursuant to the vesting of restricted stock units (RSUs)			0.4	0.3
Stock options granted			1.0	1.6
Share-based compensation expense	$ 13,070	$ 10,203	$ 44,800	$ 29,070
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost	60,700		$ 60,700
Stock vesting period			2 years 6 months
Stock vesting period			4 years	4 years
Share-based compensation expense			$ 28,200	$ 18,700
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost	57,300		$ 57,300
Stock vesting period			2 years 2 months 12 days
Stock vesting period			4 years	4 years
Share-based compensation expense			$ 16,500	$ 10,400
Restricted stock units granted			0.5	0.6
Performance-based RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost	$ 19,700		$ 19,700
RSU with performance-based vesting requirements outstanding	0.3		0.3
Restricted stock units granted			0.2
Performance-based RSUs \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock vesting period			4 years
Performance-based RSUs \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock vesting period			5 years

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	220,000,000	220,000,000
Common stock, shares issued	90,673,214	88,793,903
Common stock, shares outstanding	90,673,214	88,793,903

REAL ESTATE	9 Months Ended
REAL ESTATE	Sep. 30, 2018
Leases [Abstract]
REAL ESTATE	9. REAL ESTATE In connection with the sale-leaseback transaction of the Company’s facility in 2007, the Company recognized a net gain of $39.1 million which was deferred in accordance with authoritative guidance. The Company recognized $0.5 million and $1.9 million of the deferred gain during the nine months ended September 30, 2018 and 2017, respectively, and will recognize the remaining $8.2 million of the deferred gain on a straight-line basis over the remaining lease term which will expire at the end of 2029. During 2017, the Company entered into an amendment to extend the current term of the lease through for its current headquarters through December 31, 2029 (Term Amendment). Under the Term Amendment, the Company reduced its base rental rate by approximately 8% and will continue to pay base annual rent (subject to an annual fixed percentage increase), plus a 3.5% annual management fee, property taxes and other normal and necessary expenses associated with the lease such as utilities, repairs and maintenance. Certain incentives were included in the Term Amendment, including approximately $13.1 million in various tenant improvement allowances, three months of rent abatement, and a reduction in the required security deposit amount from $4.7 million to $3.0 million. In lieu of a cash security deposit, Wells Fargo Bank, N.A. (Wells Fargo) issued on the Company’s behalf a letter of credit in the amount of $3.0 million, which is secured by a deposit of equal amount with the same bank and is included in restricted cash on the Company’s Condensed Consolidated Balance Sheet. The Company also has the right to extend the lease for two consecutive ten-year terms as well as a right of first offer for future rental of adjacent office space owned by the landlord. In April 2018, the Company entered into a commercial lease agreement for the lease of 44,718 square feet of office space located directly behind the Company’s current headquarters. The term of such lease is 130 months (commenced on July 1, 2018). In lieu of a cash security deposit, the Company issued an approximately $1.0 million letter of credit at lease execution, which is secured by a deposit of equal amount and is included in restricted cash on the Company’s Condensed Consolidated Balance Sheet as of September 30, 2018. The Company is entitled to twelve months of base rent abatement and, as such, the base rent payments will commence in August 2019.

COMMITMENTS AND CONTINGENCIES	9 Months Ended
COMMITMENTS AND CONTINGENCIES	Sep. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	10. COMMITMENTS AND CONTINGENCIES From time to time, the Company may be subject to legal proceedings and claims in the ordinary course of business. On December 1, 2015, Icahn School of Medicine at Mount Sinai (Mount Sinai) filed a complaint against the Company in the United States District Court for the Southern District of New York: Icahn School of Medicine at Mount Sinai v. Neurocrine Biosciences, Inc., Case No. 1:15-cv-09414 (Mount Sinai Case). In the complaint, Mount Sinai alleged that the Company breached a license agreement with Mount Sinai dated August 27, 1999. In the third quarter of 2018, Mount Sinai and the Company reached agreement to dismiss the Mount Sinai Case in its entirety. The Company is not aware of any other proceedings or claims that it believes will have, individually or in the aggregate, a material adverse effect on its business, financial condition or results of operations.

Organization and Significant Accounting Policies - Additional Information (Detail) - USD ($)	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017	Sep. 30, 2017
Organization And Summary Of Significant Accounting Policies [Line Items]
Restricted cash	$ 5,477,000		$ 4,500,000
Topic 606
Organization And Summary Of Significant Accounting Policies [Line Items]
Adjustment to retained earnings		$ 0
ASU 2016-18
Organization And Summary Of Significant Accounting Policies [Line Items]
Restricted cash	$ 5,500,000			$ 4,600,000

Gross Unrealized Losses and Fair Value Available-For-Sale Investments in Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Estimated Fair Value	$ 380,156	$ 460,252
Less Than 12 Months, Unrealized Losses	(1,037)	(1,777)
12 Months or Greater, Estimated Fair Value	199,916	35,566
12 Months or Greater, Unrealized Losses	(1,026)	(74)
Total Estimated Fair Value	580,072	495,818
Total Unrealized Losses	(2,063)	(1,851)
Commercial paper
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Estimated Fair Value	32,634	62,602
Less Than 12 Months, Unrealized Losses	(49)	(35)
12 Months or Greater, Estimated Fair Value	0	0
12 Months or Greater, Unrealized Losses	0	0
Total Estimated Fair Value	32,634	62,602
Total Unrealized Losses	(49)	(35)
Corporate debt securities
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Estimated Fair Value	317,733	386,728
Less Than 12 Months, Unrealized Losses	(931)	(1,660)
12 Months or Greater, Estimated Fair Value	188,998	28,087
12 Months or Greater, Unrealized Losses	(944)	(50)
Total Estimated Fair Value	506,731	414,815
Total Unrealized Losses	(1,875)	(1,710)
Domestic and foreign government agencies debt securities
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Estimated Fair Value	29,789	10,922
Less Than 12 Months, Unrealized Losses	(57)	(82)
12 Months or Greater, Estimated Fair Value	10,918	7,479
12 Months or Greater, Unrealized Losses	(82)	(24)
Total Estimated Fair Value	40,707	18,401
Total Unrealized Losses	$ (139)	$ (106)

Investments (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule Of Investments [Line Items]
Investments	$ 624,866	$ 508,578
Commercial paper
Schedule Of Investments [Line Items]
Investments	42,465	75,362
Corporate debt securities
Schedule Of Investments [Line Items]
Investments	541,694	414,815
Domestic and foreign government agencies debt securities
Schedule Of Investments [Line Items]
Investments	$ 40,707	$ 18,401

Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	$ 624.9	$ 508.6
Short-term investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	635.3	516.0
Short-term investments \| Cash and money market fund
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	195.7	170.2
Short-term investments \| Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	42.5	159.9
Short-term investments \| Domestic and foreign government agencies debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	10.9	7.5
Short-term investments \| Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	386.2	178.4
Long-term investments \| Cash and money market fund
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	1.5	1.5
Long-term investments \| Certificates of deposit
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	4.0	3.0
Long-term investments \| Domestic and foreign government agencies debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	29.8	10.9
Long-term investments \| Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	155.5	236.4
Investments Including Cash Equivalents And Restricted Cash
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	826.1	767.8
Cash and Cash Equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	201.2	259.2
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0.0	0.1
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Short-term investments \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	195.7	170.2
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Short-term investments \| Cash and money market fund \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	195.7	170.2
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Short-term investments \| Commercial paper \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0.0	0.0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Short-term investments \| Domestic and foreign government agencies debt securities \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0.0	0.0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Short-term investments \| Corporate debt securities \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0.0	0.0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Long-term investments \| Cash and money market fund \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	1.5	1.5
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Long-term investments \| Certificates of deposit \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	4.0	3.0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Long-term investments \| Domestic and foreign government agencies debt securities \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0.0	0.0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Long-term investments \| Corporate debt securities \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0.0	0.0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Investments Including Cash Equivalents And Restricted Cash \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	201.2	174.7
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Cash and Cash Equivalents \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	201.2	174.6
Significant Other Observable Inputs (Level 2) \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	624.9	508.5
Significant Other Observable Inputs (Level 2) \| Short-term investments \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	439.6	345.8
Significant Other Observable Inputs (Level 2) \| Short-term investments \| Cash and money market fund \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0.0	0.0
Significant Other Observable Inputs (Level 2) \| Short-term investments \| Commercial paper \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	42.5	159.9
Significant Other Observable Inputs (Level 2) \| Short-term investments \| Domestic and foreign government agencies debt securities \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	10.9	7.5
Significant Other Observable Inputs (Level 2) \| Short-term investments \| Corporate debt securities \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	386.2	178.4
Significant Other Observable Inputs (Level 2) \| Long-term investments \| Cash and money market fund \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0.0	0.0
Significant Other Observable Inputs (Level 2) \| Long-term investments \| Certificates of deposit \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0.0	0.0
Significant Other Observable Inputs (Level 2) \| Long-term investments \| Domestic and foreign government agencies debt securities \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	29.8	10.9
Significant Other Observable Inputs (Level 2) \| Long-term investments \| Corporate debt securities \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	155.5	236.4
Significant Other Observable Inputs (Level 2) \| Investments Including Cash Equivalents And Restricted Cash \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	624.9	593.1
Significant Other Observable Inputs (Level 2) \| Cash and Cash Equivalents \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0.0	84.6
Significant Unobservable Inputs (Level 3) \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0.0	0.0
Significant Unobservable Inputs (Level 3) \| Short-term investments \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0.0	0.0
Significant Unobservable Inputs (Level 3) \| Short-term investments \| Cash and money market fund \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0.0	0.0
Significant Unobservable Inputs (Level 3) \| Short-term investments \| Commercial paper \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0.0	0.0
Significant Unobservable Inputs (Level 3) \| Short-term investments \| Domestic and foreign government agencies debt securities \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0.0	0.0
Significant Unobservable Inputs (Level 3) \| Short-term investments \| Corporate debt securities \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0.0	0.0
Significant Unobservable Inputs (Level 3) \| Long-term investments \| Cash and money market fund \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0.0	0.0
Significant Unobservable Inputs (Level 3) \| Long-term investments \| Certificates of deposit \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0.0	0.0
Significant Unobservable Inputs (Level 3) \| Long-term investments \| Domestic and foreign government agencies debt securities \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0.0	0.0
Significant Unobservable Inputs (Level 3) \| Long-term investments \| Corporate debt securities \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0.0	0.0
Significant Unobservable Inputs (Level 3) \| Investments Including Cash Equivalents And Restricted Cash \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0.0	0.0
Significant Unobservable Inputs (Level 3) \| Cash and Cash Equivalents \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	$ 0.0	$ 0.0

Inventory - Summary of Inventory (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Raw materials	$ 4,773	$ 0
Work in process	270	491
Finished goods	1,011	533
Total inventory	$ 6,054	$ 1,024

Convertible Senior Notes - Debt Net of Discounts and Deferred Financing Costs (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Disclosure [Abstract]
Principal	$ 517,500	$ 517,500
Deferred financing costs	(8,663)	(9,652)
Debt discount, net	(125,190)	(138,230)
Net carrying amount	383,647	0
Net carrying amount	$ 0	$ 369,618

Net Income (Loss) Per Share - Additional Information (Detail) shares in Millions	9 Months Ended
	Sep. 30, 2018 shares
2.25% Convertible Senior Notes due 2024
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Share equivalents excluded from computation of earnings per share	6.8
Performance-based RSUs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Share equivalents excluded from computation of earnings per share	0.3

Real Estate - Additional Information (Detail) $ in Millions	9 Months Ended		12 Months Ended
Real Estate - Additional Information (Detail) $ in Millions	Sep. 30, 2018 USD ($) RenewalOption	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)	Apr. 30, 2018 USD ($) ft²	Dec. 31, 2008 USD ($)
Real Estate Properties [Line Items]
Net deferred gain on real estate sale	$ 8.2				$ 39.1
Deferred gain recognized on real estate sale	$ 0.5	$ 1.9
Lease expiration year	2029
Percentage of management fee included in the base annual rent			3.50%
Lease security deposit			$ 4.7
Letter of credit			$ 3.0
Number of times to renew the lease contract \| RenewalOption	2
Lease extension period	10 years
Amended Lease Term
Real Estate Properties [Line Items]
Lease expiration date	Dec. 31, 2029
Percentage reduction in base rental			8.00%
Tenant improvement allowances			$ 13.1
Lease security deposit			$ 3.0
Commercial Lease Agreement
Real Estate Properties [Line Items]
Office space area leased \| ft²				44,718
Lease term				130 months
Commercial Lease Agreement \| Letter of Credit
Real Estate Properties [Line Items]
Lease security deposit				$ 1.0