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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2019	Apr. 24, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
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		91,286,923

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 72,778	$ 141,714
Short-term investments, available for sale	451,290	509,199
Accounts receivable	71,964	56,240
Inventory	13,010	10,864
Other current assets	24,150	19,760
Total current assets	633,192	737,777
Restricted cash	5,477	5,477
Property and equipment, net	36,661	33,869
Long-term investments, available for sale	176,689	216,028
Investment in restricted equity securities	56,400	0
Operating lease assets	49,304	0
Total assets	957,723	993,151
Current liabilities:
Accounts payable and accrued liabilities	68,280	86,377
Other current liabilities	3,723	1,856
Total current liabilities	72,003	88,233
Noncurrent operating lease liabilities	67,147	0
Convertible senior notes	393,435	388,496
Other long-term liabilities	15,863	10,231
Deferred rent	0	18,114
Deferred gain on sale of real estate	0	7,312
Total liabilities	548,448	512,386
Stockholders’ equity:
Preferred stock, $0.001 par value; 5,000 shares authorized; no shares issued and outstanding	0	0
Common stock, $0.001 par value; 220,000 shares authorized; issued and outstanding shares were 91,284 as of March 31, 2019 and 90,797 as of December 31, 2018	91	91
Additional paid-in capital	1,681,244	1,660,361
Accumulated other comprehensive loss	(233)	(1,932)
Accumulated deficit	(1,271,827)	(1,177,755)
Total stockholders’ equity	409,275	480,765
Total liabilities and stockholders’ equity	$ 957,723	$ 993,151

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2019	Dec. 31, 2018
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	91,284,000	90,797,000
Common stock, shares outstanding	91,284,000	90,797,000

Condensed Consolidated Statements of Operations And Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues:
Revenues	$ 138,403	$ 71,086
Operating expenses:
Cost of sales	1,129	950
Research and development	37,652	48,947
Acquired in-process research and development	113,081
Selling, general and administrative	87,538	58,636
Total operating expenses	239,400	108,533
Operating loss	(100,997)	(37,447)
Other (expense) income:
Interest expense	(7,853)	(7,504)
Unrealized gain on investment in restricted equity securities	1,680
Investment income and other, net	4,576	3,133
Total other expense, net	(1,597)	(4,371)
Loss before benefit from income taxes	(102,594)	(41,818)
Benefit from income taxes	(479)
Net loss	(102,115)	(41,818)
Unrealized gain (loss) on available-for-sale securities, net of tax	1,699	(1,847)
Comprehensive loss	$ (100,416)	$ (43,665)
Net loss per share, basic and diluted	$ (1.12)	$ (0.47)
Weighted average common shares outstanding, basic and diluted	91,056	89,526
Product sales, net
Revenues:
Revenues	$ 136,431	$ 71,086
Collaboration revenue
Revenues:
Revenues	$ 1,972

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash Flows from Operating Activities:
Net loss	$ (102,115)	$ (41,818)
Reconciliation of net loss to net cash used in operating activities:
Depreciation and amortization	1,566	786
Amortization of debt discount	4,598	4,265
Amortization of debt issuance costs	341	326
(Accretion) amortization of discounts/premiums on investments, net	(290)	512
Share-based compensation expense	15,764	19,879
Change in fair value of investment in restricted equity securities	(1,680)	0
Other	116	(229)
Change in operating assets and liabilities:
Accounts receivable	(15,724)	(13,497)
Inventory	(1,753)	(309)
Other current assets	(2,110)	(441)
Accounts payable and accrued liabilities	(16,567)	(7,870)
Other liabilities	5,363	(90)
Net cash used in operating activities	(112,491)	(38,486)
Cash Flows from Investing Activities:
Purchases of investments	(116,307)	(139,354)
Sales and maturities of investments	215,936	84,086
Investment in equity securities	(54,720)	0
Purchases of property and equipment	(3,939)	(1,800)
Proceeds from sales of property and equipment	4	18
Net cash provided by (used in) investing activities	40,974	(57,050)
Cash Flows from Financing Activities:
Issuance of common stock	2,581	16,135
Net cash provided by financing activities	2,581	16,135
Change in cash and cash equivalents and restricted cash	(68,936)	(79,401)
Cash and cash equivalents and restricted cash at beginning of the period	147,191	259,212
Cash and cash equivalents and restricted cash at end of the period	78,255	179,811
Supplemental Disclosure:
Non-cash capital expenditures	$ 615	$ 0

Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid in Capital	Accumulated Other Comprehensive (Loss) Gain	Accumulated Deficit
Begining balance at Dec. 31, 2017	$ 372,138	$ 89	$ 1,572,765	$ (1,850)	$ (1,198,866)
Begining balance (in shares) at Dec. 31, 2017		88,794
Net loss	(41,818)				(41,818)
Unrealized gain (loss) on available-for-sale investments, net of tax	(1,847)			(1,847)
Share-based compensation expense	19,879		19,879
Issuance of common stock for vested restricted stock units (in shares)		343
Issuance of common stock for stock option exercises	16,135	$ 1	16,134
Issuance of common stock for stock option exercises (in shares)		745
Ending balance at Mar. 31, 2018	364,487	$ 90	1,608,778	(3,697)	(1,240,684)
Ending balance (in shares) at Mar. 31, 2018		89,882
Begining balance at Dec. 31, 2018	480,765	$ 91	1,660,361	(1,932)	(1,177,755)
Begining balance (in shares) at Dec. 31, 2018		90,797
Net loss	(102,115)				(102,115)
Unrealized gain (loss) on available-for-sale investments, net of tax	1,699			1,699
Share-based compensation expense	15,764		15,764
Cumulative-effect adjustment to equity due to adoptionof ASU 2016-02 \| ASU 2016-02	8,043				8,043
Issuance of common stock for vested restricted stock units (in shares)		353
Issuance of common stock for stock option exercises	2,581		2,581
Issuance of common stock for stock option exercises (in shares)		95
Issuance of common stock for employee stock purchase plan	2,538		2,538
Issuance of common stock for employee stock purchase, (in shares)		39
Ending balance at Mar. 31, 2019	$ 409,275	$ 91	$ 1,681,244	$ (233)	$ (1,271,827)
Ending balance (in shares) at Mar. 31, 2019		91,284

Organization and Significant Accounting Policies

3 Months Ended

Mar. 31, 2019

Accounting Policies [Abstract]

Organization and Significant Accounting Policies

1. Organization and Significant Accounting Policies

Description of Business. Neurocrine Biosciences, Inc. (Neurocrine, we, our or us) is a neuroscience-focused, biopharmaceutical company with more than 25 years of experience discovering and developing life-changing treatments for people with serious, challenging and under-addressed neurological, endocrine, and psychiatric disorders. We specialize in targeting and interrupting disease-causing mechanisms involving the interconnected pathways of the nervous and endocrine systems.

Our portfolio includes United States Food and Drug Administration (FDA)-approved treatments for tardive dyskinesia (TD) and endometriosis and clinical development programs in multiple therapeutic areas including Parkinson’s disease, congenital adrenal hyperplasia, and uterine fibroids. Our treatment for endometriosis and our product candidate for uterine fibroids are partnered with AbbVie, Inc. (AbbVie). In addition, in January 2019, we entered into a collaboration and license agreement with Voyager Therapeutics, Inc. (Voyager), focused on the development and commercialization of four programs using Voyager’s propriety gene therapy platform, including one clinical development program for advanced Parkinson’s disease patients, VY-AADC.

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 our 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 Neurocrine and our 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, 2018, included in our Annual Report on Form 10-K (2018 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 condensed consolidated balance sheet at December 31, 2018, has been derived from the audited financial statements as of that date, but does not include all of the information and footnotes required by GAAP for complete financial statements.

There were no significant changes to our significant accounting policies as disclosed in the 2018 Form 10-K.

Recently Adopted Accounting Pronouncements.

ASU 2016-02. In February 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2016-02, “Leases (Topic 842)”, which requires lessees to recognize leases on the balance sheet and disclose key information about leasing arrangements. ASU 2016-02 establishes a right-of-use (ROU) model that requires a lessee to recognize a ROU asset and lease liability on the balance sheet for all leases with a term longer than 12 months. ASU 2016-02 also requires disclosures to meet the objective of enabling users of financial statements to assess the amount, timing, and uncertainty of cash flows arising from leases. On January 1, 2019, we adopted ASU 2016-02 using the modified retrospective transition method. Under this transition method, we recognized and measured leases that existed at the application date in our condensed consolidated balance sheet as of January 1, 2019.

Arrangements that are determined to be operating leases at inception are included in operating lease assets, noncurrent operating lease liabilities, and other current liabilities in our condensed consolidated balance sheets.

ROU assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. Operating lease ROU assets and operating lease liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As none of our operating leases provide an implicit rate, we use our incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The operating lease ROU asset is adjusted for any prepaid or accrued lease payments and any lease incentives received. Operating lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term. We have lease agreements with lease and non-lease components, which we have elected to account for as a single lease component. Further, we have elected to recognize our short-term lease payments in profit or loss on a straight-line basis over the associated lease term and variable lease payments in the period in which the obligation for those payments is incurred. Short-term and variable lease payments were not material in the first quarter of 2019.

In connection with the adoption of ASU 2016-02, we elected the package of practical expedients requiring no reassessment of whether any expired or existing contracts are or contain leases, the lease classification of any expired or existing leases, or initial direct costs for any existing leases. We also made accounting policy elections not to apply the recognition requirements under ASU 2016-02 to any of our short-term leases and to account for each separate lease and associated nonlease components as a single lease component for all of our leases.

In preparation for implementation of ASU 2016-02, we finalized key accounting assessments and updated processes to appropriately recognize and present the associated financial information. Based on these efforts, the adoption of ASU 2016-02 resulted in the recognition of (1) ROU assets of $50.0 million and operating lease liabilities of $70.9 million, resulting from leases of office and laboratory space; (2) the derecognition of deferred rent of $20.9 million for certain lease incentives received; and (3) a cumulative-effect adjustment of $8.0 million to the opening balance of the accumulated deficit as of January 1, 2019, resulting from the recognition of an existing deferred gain on sale of real estate. The comparative prior period information continues to be reported under the accounting standards in effect during those periods. Further, we expect the adoption of ASU 2016-02 to be immaterial to our condensed consolidated statements of operations and comprehensive loss and statements of cash flows on an ongoing basis.

ASU 2018-07. 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. On January 1, 2019, we adopted ASU 2018-07 using the modified retrospective transition method with no impact on our condensed consolidated financial statements. Further, we expect the adoption of ASU 2018-07 to be immaterial to our condensed consolidated balance sheets, statements of operations and comprehensive loss, and statements of cash flows on an ongoing basis.

Significant Collaboration and Licensing Agreements

3 Months Ended

Mar. 31, 2019

Text Block [Abstract]

Significant Collaboration and Licensing Agreements

2. Significant Collaboration and Licensing Agreements

Voyager. In January 2019, we entered into a collaboration and license agreement with Voyager, a clinical-stage gene therapy company. The agreement is focused on the development and commercialization of four programs using Voyager’s proprietary gene therapy platform. The four programs consist of the VY-AADC program for Parkinson’s disease and VY-FXN program for Friedreich’s ataxia, and the rights to two programs to be determined by the parties in the future. The agreement became effective on March 11, 2019 (the date of closing), upon expiration of the applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended.

In connection with the agreement, we paid Voyager $115.0 million upfront and purchased $50.0 million of Voyager’s common stock at $11.9625 per share, representing approximately 4.2 million shares. Pursuant to the terms of the agreement, Voyager may also be entitled to an additional $1.7 billion in development, regulatory, and commercial milestones across the four programs, as well as royalties on net sales of any collaboration product.

Pursuant to development plans agreed to by us and Voyager, unless Voyager exercises its co-development and co-commercialization rights as provided for in the agreement, we will be responsible for all development costs. Further, upon the occurrence of a specified event for each program, we will assume responsibility for the development, manufacturing, and commercialization activities of such program.

We accounted for the transaction as an asset acquisition as the set of acquired assets did not constitute a business. Our equity investment in Voyager was recorded at a fair value of $54.7 million after considering Voyager’s stock price on the date of closing and certain lock-up and voting provisions applicable to the acquired shares. The remaining $113.1 million of the purchase price, which includes the applicable transaction costs, was expensed as in-process research and development (IPR&D) as the general lack of discernable future benefits at the time the costs were incurred indicated that the immediate recognition principle of expense recognition should apply.

We may terminate the agreement upon 180 days written notice to Voyager prior to the first commercial sale of any collaboration product or upon 1 year after the date of notice if such notice is provided after the first commercial sale of any collaboration product. Unless terminated earlier, the agreement will continue in effect until the expiration of the last to expire royalty term with respect to any collaboration product or the last expiration or termination of any exercised co-development and co-commercialization rights by Voyager as provided for in the agreement.

BIAL – Portela & Ca, S.A. In February 2017, we entered into an exclusive license agreement with BIAL – Portela & Ca, S.A. (BIAL) for the development and commercialization of opicapone for the treatment of human diseases and conditions, including as an adjunctive therapy to levodopa/DOPA decarboxylase inhibitors in adult Parkinson's disease patients, in the United States (U.S.) and Canada. We paid BIAL an upfront license fee of $30.0 million and have agreed to make additional regulatory event-based payments of up to $40.0 million, of which $10.0 million has been paid as of March 31, 2019, and up to an additional $75.0 million in commercial event-based payments.

Mitsubishi Tanabe Pharma Corporation. In March 2015, we entered into a collaboration and license agreement with Mitsubishi Tanabe Pharma Corporation (MTPC) for the development and commercialization of INGREZZA for movement disorders in Japan and other select Asian markets. MTPC made an upfront payment of $30.0 million and has agreed to make an additional $85.0 million in development and regulatory event-based payments, payments for the manufacture of pharmaceutical products, and royalties on product sales in select territories in Asia.

Since inception of the agreement, we have recognized revenue of $19.8 million associated with the delivery of a technology license and existing know-how, and $15.0 million in development event-based payments resulting from MTPC’s initiation of Phase II/III clinical trials of INGREZZA in TD in Asia. In accordance with our continuing performance obligations, $10.2 million of the $30.0 million upfront payment is being deferred to be recognized in future periods. Under the terms of the agreement, there is no general obligation to return the upfront payment for any non-contingent deliverable.

AbbVie. In June 2010, we entered into an exclusive worldwide collaboration with AbbVie, to develop and commercialize elagolix and all next-generation gonadotropin-releasing factor antagonists for women’s and men’s health. AbbVie made an upfront payment of $75.0 million and has agreed to make additional development and regulatory event-based payments of up to $480.0 million, of which $115.0 million has been earned as of March 31, 2019, and up to an additional $50.0 million in commercial event-based payments.

Investments

3 Months Ended

Mar. 31, 2019

Investments Schedule [Abstract]

Investments

3. Investments

Available-for-sale securities are carried at fair value, with any unrealized gains and losses reported in comprehensive loss. The amortized cost of debt securities in this category is adjusted for the 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 and other, net. 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 and other, net. Further, investments in equity securities of certain companies that are subject to holding period restrictions longer than 1 year are carried at fair value, with any unrealized gains or losses reported in other expense, net.

Investments consist of the following:

(in thousands)	March 31, 2019		December 31, 2018
Commercial paper	$	97,490	$	94,572
Corporate debt securities		441,615		544,978
Securities of government sponsored entities		88,874		85,677
Restricted equity securities		56,400		—
Total investments	$	684,379	$	725,227

Investments classified as available-for-sale securities consist of the following:

(in thousands)	Contractual Maturity (in years)	Amortized Cost		Gross Unrealized Gains⁽¹⁾		Gross Unrealized Losses⁽¹⁾			Aggregate Estimated Fair Value
March 31, 2019:
Classified as current assets:
Commercial paper	Less than 1	$	97,517	$	14	$	(41	)	$	97,490
Corporate debt securities	Less than 1		308,363		79		(404	)		308,038
Securities of government-sponsored entities	Less than 1		45,718		65		(21	)		45,762
Total short-term available-for-sale securities		$	451,598	$	158	$	(466	)	$	451,290
Classified as non-current assets:
Corporate debt securities	1 to 2	$	133,179	$	438	$	(40	)		133,577
Securities of government-sponsored entities	1 to 2		42,868		244		—			43,112
Total long-term available-for-sale securities		$	176,047	$	682	$	(40	)	$	176,689
blank
December 31, 2018:
Classified as current assets:
Commercial paper	Less than 1	$	94,617	$	—	$	(45	)	$	94,572
Corporate debt securities	Less than 1		395,385		—		(1,598	)		393,787
Securities of government-sponsored entities	Less than 1		20,887		8		(55	)		20,840
Total short-term available-for-sale securities		$	510,889	$	8	$	(1,698	)	$	509,199
Classified as non-current assets:
Corporate debt securities	1 to 2	$	151,594	$	66	$	(469	)	$	151,191
Securities of government-sponsored entities	1 to 2		64,676		162		(1	)		64,837
Total long-term available-for-sale securities		$	216,270	$	228	$	(470	)	$	216,028

(1)	Unrealized gains and losses, net of tax, are included in other comprehensive loss.

The following table presents gross unrealized losses and fair value for those available-for-sale investments that were in an unrealized loss position, aggregated by investment category and length of time that individual securities have been in a continuous loss position:

	Less Than 12 Months					12 Months or Greater					Total
(in thousands)	Estimated Fair Value		Unrealized Losses			Estimated Fair Value		Unrealized Losses			Estimated Fair Value		Unrealized Losses
March 31, 2019:
Commercial paper	$	31,457	$	(41	)	$	—	$	—		$	31,457	$	(41	)
Corporate debt securities		63,323		(50	)		174,206		(394	)		237,529		(444	)
Securities of government-sponsored entities		—		—			10,979		(21	)		10,979		(21	)
Total	$	94,780	$	(91	)	$	185,185	$	(415	)	$	279,965	$	(506	)
blank
December 31, 2018:
Commercial paper	$	51,927	$	(45	)	$	—	$	—		$	51,927	$	(45	)
Corporate debt securities		274,696		(746	)		234,798		(1,321	)		509,494		(2,067	)
Securities of government-sponsored entities		4,999		(1	)		10,947		(55	)		15,946		(56	)
Total	$	331,622	$	(792	)	$	245,745	$	(1,376	)	$	577,367	$	(2,168	)

At each reporting date, we perform an evaluation of impairment to determine if any unrealized losses are other-than-temporary. Factors considered in determining whether a loss is other-than-temporary include the length of time and extent to which fair value has been less than the cost basis, the financial condition of the issuer, and our intent and ability to hold the investment until recovery of the amortized cost basis. We intend and have the ability to hold our investments in unrealized loss positions until their amortized cost basis has been recovered. Further, based on our evaluation, we determined that unrealized losses were not other-than-temporary at March 31, 2019 and December 31, 2018.

Fair Value Measurements

3 Months Ended

Mar. 31, 2019

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.

We classify our cash equivalents and available-for-sale investments within Level 1 or Level 2. The fair value of our investment grade corporate debt securities is determined using proprietary valuation models and analytical tools, which utilize market pricing or prices for similar instruments that are both objective and publicly available, such as matrix pricing or reported trades, benchmark yields, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, and offers.

The fair value of our investments in restricted equity securities is determined using an option pricing valuation model and classified as Level 3 within the fair value hierarchy. The most significant assumptions within the option pricing valuation model are the term of the restrictions and the stock price volatility, which is based upon the historical volatility of similar companies. Significant changes in any of those inputs in isolation would result in a significantly higher or lower fair value measurement.

The $517.5 million of 2.25% convertible senior notes due May 15, 2024 (2024 Notes) were recorded at the estimated value of a similar non-convertible instrument on the date of issuance and accretes to the face value of the 2024 Notes over their 7-year term. The fair value of the 2024 Notes, estimated utilizing market quotations from an over-the-counter trading market (Level 2), was $700.9 million as of March 31, 2019 and $616.1 million as of December 31, 2018. Refer to Note 7 for more information.

We did not reclassify any investments between levels in the fair value hierarchy during the first quarter of 2019 or 2018.

Investments, which were measured at fair value on a recurring basis using the inputs described above, consisted of the following:

	blank			Fair Value Measurements Using
(in millions)	Carrying Value			Quoted Prices in Active Markets for Identical Assets (Level 1)			Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
March 31, 2019:
Classified as current assets:
Cash and money market funds	$	72.8		$	72.8		$	—	$	—
Commercial paper		97.5			—			97.5		—
Securities of government-sponsored entities		45.8			—			45.8		—
Corporate debt securities		308.0			—			308.0		—
Subtotal		524.1			72.8			451.3		—
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		43.1			—			43.1		—
Corporate debt securities		133.6			—			133.6		—
Restricted equity securities		56.4			—			—		56.4
Total		762.7			78.3			628.0		56.4
Less cash and cash equivalents and restricted cash		(78.3	)		(78.3	)		—		—
Total investments	$	684.4		$	—		$	628.0	$	56.4
blank
December 31, 2018:
Classified as current assets:
Cash and money market funds	$	141.7		$	141.7		$	—	$	—
Commercial paper		94.6			—			94.6		—
Securities of government-sponsored entities		20.8			—			20.8		—
Corporate debt securities		393.8			—			393.8		—
Subtotal		650.9			141.7			509.2		—
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		64.8			—			64.8		—
Corporate debt securities		151.2			—			151.2		—
Total		872.4			147.2			725.2		—
Less cash and cash equivalents and restricted cash		(147.2	)		(147.2	)		—		—
Total investments	$	725.2		$	—		$	725.2	$	—

The following table presents a reconciliation of our investment in restricted equity securities measured at fair value on a quarterly basis using significant unobservable inputs (Level 3):

(in millions)
Balance at December 31, 2018	$	—
Investment in restricted equity securities		54.7
Unrealized gain recognized on restricted equity securities still held at March 31, 2019		1.7
Balance at March 31, 2019	$	56.4

- 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

Inventory

3 Months Ended

Mar. 31, 2019

Inventory Disclosure [Abstract]

Inventory

5. Inventory

Inventory consisted of the following:

(in thousands)	March 31, 2019		December 31, 2018
Raw materials	$	7,733	$	7,855
Work in process		4,458		2,208
Finished goods		819		801
Total inventory	$	13,010	$	10,864

Leases

3 Months Ended

Mar. 31, 2019

Leases [Abstract]

Leases

6. Leases

In December 2007, we closed the sale of our facility and associated real property for a purchase price of $109.0 million. Concurrent with the sale, we retired the entire $47.7 million in mortgage debt previously outstanding with respect to the facility and associated real property and received cash of $61.0 million, net of transaction costs and debt retirement. The ultimate result of this real estate sale was a net deferred gain of $39.1 million, of which the remaining balance was $8.0 million as of December 31, 2018, and which we recognized as a cumulative-effect adjustment to equity upon adoption of Topic 842 on January 1, 2019.

Upon the closing of the sale of the facility and associated real property, we entered into an agreement (original lease) whereby we leased back our corporate headquarters, comprised of two buildings located in San Diego, California, for an initial term of 12 years. In 2008 through 2011, we entered into a series of subsequent amendments to the original lease, whereby we vacated a building and continued to occupy one building.

In June 2017, we entered into an amendment to extend the current term of the original lease through December 31, 2029. Under the terms of the amendment, we will continue to pay base annual rent (subject to an annual fixed percentage increase), property taxes, and other normal and necessary expenses, such as utilities, repairs, and maintenance. Certain incentives were included in the lease, including $13.1 million in tenant improvement allowances and three months of rent abatement. In lieu of a cash security deposit, Wells Fargo Bank, N.A. (Wells Fargo) issued a $3.0 million letter of credit on our behalf, which is secured by a deposit of equal amount with the same bank. We have the right to extend the lease for 2 consecutive 10-year terms and a right of first offer for future rental of adjacent office space owned by the landlord. At commencement of the lease, we were not reasonably certain to exercise either of the two 10-year extension options contained within the lease. As such, these options were not recognized as part of the associated operating lease ROU asset or liability.

In May 2018, we entered into an agreement to lease 44,718 square feet of office space in San Diego, California, which commenced on July 1, 2018, for a term of 10 years and 10 months. Under the terms of the lease, we will pay base annual rent (subject to an annual fixed percentage increase), plus property taxes, and other normal and necessary expenses, such as utilities, repairs, and maintenance. Certain incentives were included in the lease, including $4.2 million in tenant improvement allowances and twelve months of rent abatement. In lieu of a cash security deposit, Wells Fargo issued a $1.0 million letter of credit on our behalf, which is secured by a deposit of equal amount with the same bank. We do not have the right to extend the lease or right of first offer for future rental of adjacent office space owned by the landlord.

In the first quarter of 2019, our operating lease cost was $1.9 million and cash paid for amounts included in the measurement of lease liabilities for operating cash flows from operating leases was $1.6 million. As of March 31, 2019, we reported operating lease ROU assets and operating lease liabilities of $49.3 million and $70.4 million, respectively. Further, as of March 31, 2019, our operating leases had a weighted average remaining lease term of 10.57 years and a weighted average discount rate of 6.65%.

At March 31, 2019, the minimum lease payments for our operating lease liabilities were as follows:

(in thousands)	Operating Leases
Year Ending December 31,
2019 (9 months remaining)	$	5,777
2020		8,399
2021		8,624
2022		8,888
2023		9,160
Thereafter		59,462
Total operating lease payments		100,310
Less accreted interest		(29,896	)
Total operating lease liabilities		70,414
Less current operating lease liabilities		(3,267	)
Noncurrent operating lease liabilities	$	67,147

Convertible Senior Notes

3 Months Ended

Mar. 31, 2019

Debt Disclosure [Abstract]

Convertible Senior Notes

7. Convertible Senior Notes

On May 2, 2017, we completed a private placement of $517.5 million in aggregate principal amount of 2.25% convertible senior notes due 2024 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 us.

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 our 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 our 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 our assets; or

(iv)

if we call 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.

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 our common stock or a combination of cash and shares of our common stock, at our option.

It is our 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 2024 Indenture. 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 our 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 our common stock. At the initial conversion rate, settlement of the 2024 Notes for shares of our 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 our common stock on the Nasdaq Global Select Market on April 26, 2017, the date that we 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, we would be required to repay the $517.5 million in principal value and any conversion premium in any combination of cash and shares of our common stock, at our option.

We may not redeem the 2024 Notes prior to May 15, 2021. On or after May 15, 2021, we may redeem for cash all or part of the 2024 Notes if the last reported sale price (as defined in the 2024 Indenture) of our 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 we provide 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 we undergo a fundamental change, as defined in the 2024 Indenture, subject to certain conditions, holders of the 2024 Notes may require us 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, we 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 our general unsecured obligations that rank senior in right of payment to all of our indebtedness that is expressly subordinated in right of payment to the 2024 Notes, and equal in right of payment to our unsecured indebtedness.

While the 2024 Notes are currently classified as long-term on our condensed consolidated balance sheets, the future convertibility and resulting balance sheet classification of this liability will be monitored at each quarterly reporting date and will be analyzed dependent upon market prices of our common stock during the prescribed measurement periods. In the event that the holders of the 2024 Notes have the election to convert the 2024 Notes at any time during the prescribed measurement period, the 2024 Notes would then be considered a current obligation and classified as such.

We are required to separately account for the liability and equity components of the 2024 Notes as they may be settled entirely or partially in cash upon conversion in a manner that reflects our 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 was 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.

We 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 us. 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.

The 2024 Notes, net of discounts and deferred financing costs, consisted of the following:

(in thousands)	March 31, 2019			December 31, 2018
Principal	$	517,500		$	517,500
Deferred financing costs		(7,985	)		(8,326	)
Debt discount, net		(116,080	)		(120,678	)
Net carrying amount	$	393,435		$	388,496

Net Loss Per Share

3 Months Ended

Mar. 31, 2019

Earnings Per Share [Abstract]

Net Loss Per Share

8. Net Loss Per Share

Net loss per share was calculated as follows:

	Three Months Ended March 31,
(in thousands, except per share data)	2019			2018
Net loss - basic and diluted	$	(102,115	)	$	(41,818	)
Weighted-average common shares outstanding:
Basic and diluted		91,056			89,526
Net loss per share:
Basic and diluted	$	(1.12	)	$	(0.47	)

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.

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. We issued the 2024 Notes with a combination settlement feature, which we have the ability and intent to use upon conversion of the 2024 Notes, to settle the principal amount of debt for cash and the excess of the principal portion in shares of our 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 are considered under the treasury stock method.

Shares which have been excluded from diluted per share amounts because their effect would have been anti-dilutive consisted of the following:

Three Months Ended

March 31,

(in thousands)

2019

2018

Stock options, restricted stock and convertible senior notes

8,299

8,176

Organization and Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Description of Business	Description of Business. Neurocrine Biosciences, Inc. (Neurocrine, we, our or us) is a neuroscience-focused, biopharmaceutical company with more than 25 years of experience discovering and developing life-changing treatments for people with serious, challenging and under-addressed neurological, endocrine, and psychiatric disorders. We specialize in targeting and interrupting disease-causing mechanisms involving the interconnected pathways of the nervous and endocrine systems. Our portfolio includes United States Food and Drug Administration (FDA)-approved treatments for tardive dyskinesia (TD) and endometriosis and clinical development programs in multiple therapeutic areas including Parkinson’s disease, congenital adrenal hyperplasia, and uterine fibroids. Our treatment for endometriosis and our product candidate for uterine fibroids are partnered with AbbVie, Inc. (AbbVie). In addition, in January 2019, we entered into a collaboration and license agreement with Voyager Therapeutics, Inc. (Voyager), focused on the development and commercialization of four programs using Voyager’s propriety gene therapy platform, including one clinical development program for advanced Parkinson’s disease patients, VY-AADC.
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 our 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 Neurocrine and our 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, 2018, included in our Annual Report on Form 10-K (2018 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 condensed consolidated balance sheet at December 31, 2018, has been derived from the audited financial statements as of that date, but does not include all of the information and footnotes required by GAAP for complete financial statements. There were no significant changes to our significant accounting policies as disclosed in the 2018 Form 10-K.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements. ASU 2016-02. In February 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2016-02, “Leases (Topic 842)”, which requires lessees to recognize leases on the balance sheet and disclose key information about leasing arrangements. ASU 2016-02 establishes a right-of-use (ROU) model that requires a lessee to recognize a ROU asset and lease liability on the balance sheet for all leases with a term longer than 12 months. ASU 2016-02 also requires disclosures to meet the objective of enabling users of financial statements to assess the amount, timing, and uncertainty of cash flows arising from leases. On January 1, 2019, we adopted ASU 2016-02 using the modified retrospective transition method. Under this transition method, we recognized and measured leases that existed at the application date in our condensed consolidated balance sheet as of January 1, 2019. Arrangements that are determined to be operating leases at inception are included in operating lease assets, noncurrent operating lease liabilities, and other current liabilities in our condensed consolidated balance sheets. ROU assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. Operating lease ROU assets and operating lease liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As none of our operating leases provide an implicit rate, we use our incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The operating lease ROU asset is adjusted for any prepaid or accrued lease payments and any lease incentives received. Operating lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term. We have lease agreements with lease and non-lease components, which we have elected to account for as a single lease component. Further, we have elected to recognize our short-term lease payments in profit or loss on a straight-line basis over the associated lease term and variable lease payments in the period in which the obligation for those payments is incurred. Short-term and variable lease payments were not material in the first quarter of 2019. In connection with the adoption of ASU 2016-02, we elected the package of practical expedients requiring no reassessment of whether any expired or existing contracts are or contain leases, the lease classification of any expired or existing leases, or initial direct costs for any existing leases. We also made accounting policy elections not to apply the recognition requirements under ASU 2016-02 to any of our short-term leases and to account for each separate lease and associated nonlease components as a single lease component for all of our leases. In preparation for implementation of ASU 2016-02, we finalized key accounting assessments and updated processes to appropriately recognize and present the associated financial information. Based on these efforts, the adoption of ASU 2016-02 resulted in the recognition of (1) ROU assets of $50.0 million and operating lease liabilities of $70.9 million, resulting from leases of office and laboratory space; (2) the derecognition of deferred rent of $20.9 million for certain lease incentives received; and (3) a cumulative-effect adjustment of $8.0 million to the opening balance of the accumulated deficit as of January 1, 2019, resulting from the recognition of an existing deferred gain on sale of real estate. The comparative prior period information continues to be reported under the accounting standards in effect during those periods. Further, we expect the adoption of ASU 2016-02 to be immaterial to our condensed consolidated statements of operations and comprehensive loss and statements of cash flows on an ongoing basis. ASU 2018-07. 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. On January 1, 2019, we adopted ASU 2018-07 using the modified retrospective transition method with no impact on our condensed consolidated financial statements. Further, we expect the adoption of ASU 2018-07 to be immaterial to our condensed consolidated balance sheets, statements of operations and comprehensive loss, and statements of cash flows on an ongoing basis.

Investments (Tables)

3 Months Ended

Mar. 31, 2019

Investments Schedule [Abstract]

Investments

Investments consist of the following:

(in thousands)	March 31, 2019		December 31, 2018
Commercial paper	$	97,490	$	94,572
Corporate debt securities		441,615		544,978
Securities of government sponsored entities		88,874		85,677
Restricted equity securities		56,400		—
Total investments	$	684,379	$	725,227

Summary of Investments Classified as Available-For-Sale Securities

Investments classified as available-for-sale securities consist of the following:

(in thousands)	Contractual Maturity (in years)	Amortized Cost		Gross Unrealized Gains⁽¹⁾		Gross Unrealized Losses⁽¹⁾			Aggregate Estimated Fair Value
March 31, 2019:
Classified as current assets:
Commercial paper	Less than 1	$	97,517	$	14	$	(41	)	$	97,490
Corporate debt securities	Less than 1		308,363		79		(404	)		308,038
Securities of government-sponsored entities	Less than 1		45,718		65		(21	)		45,762
Total short-term available-for-sale securities		$	451,598	$	158	$	(466	)	$	451,290
Classified as non-current assets:
Corporate debt securities	1 to 2	$	133,179	$	438	$	(40	)		133,577
Securities of government-sponsored entities	1 to 2		42,868		244		—			43,112
Total long-term available-for-sale securities		$	176,047	$	682	$	(40	)	$	176,689
blank
December 31, 2018:
Classified as current assets:
Commercial paper	Less than 1	$	94,617	$	—	$	(45	)	$	94,572
Corporate debt securities	Less than 1		395,385		—		(1,598	)		393,787
Securities of government-sponsored entities	Less than 1		20,887		8		(55	)		20,840
Total short-term available-for-sale securities		$	510,889	$	8	$	(1,698	)	$	509,199
Classified as non-current assets:
Corporate debt securities	1 to 2	$	151,594	$	66	$	(469	)	$	151,191
Securities of government-sponsored entities	1 to 2		64,676		162		(1	)		64,837
Total long-term available-for-sale securities		$	216,270	$	228	$	(470	)	$	216,028

(1)	Unrealized gains and losses, net of tax, are included in other comprehensive loss.

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

	Less Than 12 Months					12 Months or Greater					Total
(in thousands)	Estimated Fair Value		Unrealized Losses			Estimated Fair Value		Unrealized Losses			Estimated Fair Value		Unrealized Losses
March 31, 2019:
Commercial paper	$	31,457	$	(41	)	$	—	$	—		$	31,457	$	(41	)
Corporate debt securities		63,323		(50	)		174,206		(394	)		237,529		(444	)
Securities of government-sponsored entities		—		—			10,979		(21	)		10,979		(21	)
Total	$	94,780	$	(91	)	$	185,185	$	(415	)	$	279,965	$	(506	)
blank
December 31, 2018:
Commercial paper	$	51,927	$	(45	)	$	—	$	—		$	51,927	$	(45	)
Corporate debt securities		274,696		(746	)		234,798		(1,321	)		509,494		(2,067	)
Securities of government-sponsored entities		4,999		(1	)		10,947		(55	)		15,946		(56	)
Total	$	331,622	$	(792	)	$	245,745	$	(1,376	)	$	577,367	$	(2,168	)

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

Investments Measured at Fair Value on Recurring Basis

Investments, which were measured at fair value on a recurring basis using the inputs described above, consisted of the following:

	blank			Fair Value Measurements Using
(in millions)	Carrying Value			Quoted Prices in Active Markets for Identical Assets (Level 1)			Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
March 31, 2019:
Classified as current assets:
Cash and money market funds	$	72.8		$	72.8		$	—	$	—
Commercial paper		97.5			—			97.5		—
Securities of government-sponsored entities		45.8			—			45.8		—
Corporate debt securities		308.0			—			308.0		—
Subtotal		524.1			72.8			451.3		—
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		43.1			—			43.1		—
Corporate debt securities		133.6			—			133.6		—
Restricted equity securities		56.4			—			—		56.4
Total		762.7			78.3			628.0		56.4
Less cash and cash equivalents and restricted cash		(78.3	)		(78.3	)		—		—
Total investments	$	684.4		$	—		$	628.0	$	56.4
blank
December 31, 2018:
Classified as current assets:
Cash and money market funds	$	141.7		$	141.7		$	—	$	—
Commercial paper		94.6			—			94.6		—
Securities of government-sponsored entities		20.8			—			20.8		—
Corporate debt securities		393.8			—			393.8		—
Subtotal		650.9			141.7			509.2		—
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		64.8			—			64.8		—
Corporate debt securities		151.2			—			151.2		—
Total		872.4			147.2			725.2		—
Less cash and cash equivalents and restricted cash		(147.2	)		(147.2	)		—		—
Total investments	$	725.2		$	—		$	725.2	$	—

Reconciliation of Our Investment in Restricted Equity Securities Measured at Fair Value on Quarterly Basis Using Significant Unobservable Inputs (Level 3)

The following table presents a reconciliation of our investment in restricted equity securities measured at fair value on a quarterly basis using significant unobservable inputs (Level 3):

(in millions)
Balance at December 31, 2018	$	—
Investment in restricted equity securities		54.7
Unrealized gain recognized on restricted equity securities still held at March 31, 2019		1.7
Balance at March 31, 2019	$	56.4

Inventory (Tables)

3 Months Ended

Mar. 31, 2019

Inventory Disclosure [Abstract]

Summary of Inventory

Inventory consisted of the following:

(in thousands)	March 31, 2019		December 31, 2018
Raw materials	$	7,733	$	7,855
Work in process		4,458		2,208
Finished goods		819		801
Total inventory	$	13,010	$	10,864

Leases (Tables)

3 Months Ended

Mar. 31, 2019

Leases [Abstract]

Summary of Minimum Lease Payments for Operating Lease Liabilities

At March 31, 2019, the minimum lease payments for our operating lease liabilities were as follows:

(in thousands)	Operating Leases
Year Ending December 31,
2019 (9 months remaining)	$	5,777
2020		8,399
2021		8,624
2022		8,888
2023		9,160
Thereafter		59,462
Total operating lease payments		100,310
Less accreted interest		(29,896	)
Total operating lease liabilities		70,414
Less current operating lease liabilities		(3,267	)
Noncurrent operating lease liabilities	$	67,147

Convertible Senior Notes (Tables)

3 Months Ended

Mar. 31, 2019

Debt Disclosure [Abstract]

Summary of Notes Net of Discount and Deferred Financing Costs

The 2024 Notes, net of discounts and deferred financing costs, consisted of the following:

(in thousands)	March 31, 2019			December 31, 2018
Principal	$	517,500		$	517,500
Deferred financing costs		(7,985	)		(8,326	)
Debt discount, net		(116,080	)		(120,678	)
Net carrying amount	$	393,435		$	388,496

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28541-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21506-112644

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21521-112644

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21538-112644

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

Net Loss Per Share (Tables)

3 Months Ended

Mar. 31, 2019

Earnings Per Share [Abstract]

Schedule of Net Loss Per Share

Net loss per share was calculated as follows:

	Three Months Ended March 31,
(in thousands, except per share data)	2019			2018
Net loss - basic and diluted	$	(102,115	)	$	(41,818	)
Weighted-average common shares outstanding:
Basic and diluted		91,056			89,526
Net loss per share:
Basic and diluted	$	(1.12	)	$	(0.47	)

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 consisted of the following:

Three Months Ended

March 31,

(in thousands)

2019

2018

Stock options, restricted stock and convertible senior notes

8,299

8,176

Organization and Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	Jan. 01, 2019	Mar. 31, 2019	Dec. 31, 2018
Organization And Summary Of Significant Accounting Policies [Line Items]
Right-of-use (ROU) assets		$ 49,304	$ 0
Operating lease liabilities		$ 70,414
ASU 2016-02 (Topic 842)
Organization And Summary Of Significant Accounting Policies [Line Items]
Right-of-use (ROU) assets	$ 50,000
Operating lease liabilities	70,900
Derecognition of deferred rent for certain lease incentives received	20,900
Recognition of Deferred Gain on Sale of Real Estate \| ASU 2016-02 (Topic 842)
Organization And Summary Of Significant Accounting Policies [Line Items]
Deferred gain on sale of real estate as cumulative-effect adjustment to equity	$ 8,000

Significant Collaboration and Licensing Agreements - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions	1 Months Ended				3 Months Ended
	Jan. 31, 2019	Feb. 28, 2017	Mar. 31, 2015	Jun. 30, 2010	Mar. 31, 2019	Dec. 31, 2018
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Equity investment fair value amount					$ 56,400	$ 0
Voyager Therapeutics \| Collaboration and License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front cash payable	$ 115,000
Collaborative agreement equity investment amount	$ 50,000
Share price	$ 11.9625
Equity investment fair value amount	$ 54,700
Collaboration termination notice period					180 days
Voyager Therapeutics \| Collaboration and License Agreement \| IPR&D
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative agreement remaining purchase price	$ 113,100
Voyager Therapeutics \| Collaboration and License Agreement \| Common Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Common stock issued for collaboration agreement	4.2
Voyager Therapeutics \| Collaboration and License Agreement \| Development, Regulatory and Commercial Milestone Payment
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential milestone payments	$ 1,700,000
B I A L
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front license fees		$ (30,000)
B I A L \| Development and Regulatory Milestone Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative agreement maximum additional payment to receive					$ 40,000
Collaborative agreement payment received					10,000
B I A L \| Commercial Milestone Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative agreement maximum additional payment to receive					75,000
Mitsubishi Tanabe
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front license fees			$ 30,000
Collaborative agreement maximum additional payment to receive			85,000
Revenues recognized under collaboration agreement			19,800
Deferred revenues under collaboration			10,200
Mitsubishi Tanabe \| Phase II/III Clinical Trials
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenues recognized under collaboration agreement			$ 15,000
AbbVie
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front license fees				$ 75,000
AbbVie \| Development and Regulatory Milestone Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative agreement maximum additional payment to receive					480,000
Collaborative agreement payment received					115,000
AbbVie \| Commercial Milestone Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative agreement maximum additional payment to receive					$ 50,000

Investments (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Schedule Of Investments [Line Items]
Investments	$ 684,379	$ 725,227
Investments	56,400	0
Commercial paper
Schedule Of Investments [Line Items]
Investments	97,490	94,572
Corporate debt securities
Schedule Of Investments [Line Items]
Investments	441,615	544,978
Securities of government-sponsored entities
Schedule Of Investments [Line Items]
Investments	88,874	85,677
Restricted equity securities
Schedule Of Investments [Line Items]
Investments	$ 56,400	$ 0

Summary of Investments Classified as Available-For-Sale Securities (Detail) - USD ($)
$ in Thousands

3 Months Ended

12 Months Ended

Mar. 31, 2019

Dec. 31, 2018

Schedule Of Available For Sale Securities [Line Items]

Aggregate Estimated Fair Value

$ 684,379

$ 725,227

Commercial paper

Schedule Of Available For Sale Securities [Line Items]

Aggregate Estimated Fair Value

97,490

94,572

Corporate debt securities

Schedule Of Available For Sale Securities [Line Items]

Aggregate Estimated Fair Value

441,615

544,978

Securities of government-sponsored entities

Schedule Of Available For Sale Securities [Line Items]

Aggregate Estimated Fair Value

88,874

85,677

Short-term investments

Schedule Of Available For Sale Securities [Line Items]

Amortized Cost

451,598

510,889

Gross Unrealized Gains

^[1]

158

Gross Unrealized Losses

^[1]

(466)

(1,698)

Aggregate Estimated Fair Value

451,290

509,199

Short-term investments | Commercial paper

Schedule Of Available For Sale Securities [Line Items]

Amortized Cost

97,517

94,617

Gross Unrealized Gains

^[1]

Gross Unrealized Losses

^[1]

(41)

(45)

Aggregate Estimated Fair Value

$ 97,490

$ 94,572

Short-term investments | Commercial paper | Maximum

Schedule Of Available For Sale Securities [Line Items]

Available for sale securities contractual maturity

1 year

Short-term investments | Corporate debt securities

Schedule Of Available For Sale Securities [Line Items]

Amortized Cost

$ 308,363

$ 395,385

Gross Unrealized Gains

^[1]

Gross Unrealized Losses

^[1]

(404)

(1,598)

Aggregate Estimated Fair Value

$ 308,038

$ 393,787

Short-term investments | Corporate debt securities | Maximum

Schedule Of Available For Sale Securities [Line Items]

Available for sale securities contractual maturity

1 year

Short-term investments | Securities of government-sponsored entities

Schedule Of Available For Sale Securities [Line Items]

Amortized Cost

$ 45,718

$ 20,887

Gross Unrealized Gains

^[1]

Gross Unrealized Losses

^[1]

(21)

(55)

Aggregate Estimated Fair Value

$ 45,762

$ 20,840

Short-term investments | Securities of government-sponsored entities | Maximum

Schedule Of Available For Sale Securities [Line Items]

Available for sale securities contractual maturity

1 year

Long-term investments

Schedule Of Available For Sale Securities [Line Items]

Amortized Cost

$ 176,047

$ 216,270

Gross Unrealized Gains

^[1]

682

228

Gross Unrealized Losses

^[1]

(40)

(470)

Aggregate Estimated Fair Value

176,689

216,028

Long-term investments | Corporate debt securities

Schedule Of Available For Sale Securities [Line Items]

Amortized Cost

133,179

151,594

Gross Unrealized Gains

^[1]

438

Gross Unrealized Losses

^[1]

(40)

(469)

Aggregate Estimated Fair Value

$ 133,577

$ 151,191

Long-term investments | Corporate debt securities | Minimum

Schedule Of Available For Sale Securities [Line Items]

Available for sale securities contractual maturity

1 year

Long-term investments | Corporate debt securities | Maximum

Schedule Of Available For Sale Securities [Line Items]

Available for sale securities contractual maturity

2 years

Long-term investments | Securities of government-sponsored entities

Schedule Of Available For Sale Securities [Line Items]

Amortized Cost

$ 42,868

$ 64,676

Gross Unrealized Gains

^[1]

244

162

Gross Unrealized Losses

^[1]

(1)

Aggregate Estimated Fair Value

$ 43,112

$ 64,837

Long-term investments | Securities of government-sponsored entities | Minimum

Schedule Of Available For Sale Securities [Line Items]

Available for sale securities contractual maturity

1 year

Long-term investments | Securities of government-sponsored entities | Maximum

Schedule Of Available For Sale Securities [Line Items]

Available for sale securities contractual maturity

2 years

[1]	Unrealized gains and losses, net of tax, are included in other comprehensive loss

Gross Unrealized Losses and Fair Value Available-For-Sale Investments in Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Estimated Fair Value	$ 94,780	$ 331,622
Less Than 12 Months, Unrealized Losses	(91)	(792)
12 Months or Greater, Estimated Fair Value	185,185	245,745
12 Months or Greater, Unrealized Losses	(415)	(1,376)
Total Estimated Fair Value	279,965	577,367
Total Unrealized Losses	(506)	(2,168)
Commercial paper
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Estimated Fair Value	31,457	51,927
Less Than 12 Months, Unrealized Losses	(41)	(45)
12 Months or Greater, Estimated Fair Value	0	0
12 Months or Greater, Unrealized Losses	0	0
Total Estimated Fair Value	31,457	51,927
Total Unrealized Losses	(41)	(45)
Corporate debt securities
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Estimated Fair Value	63,323	274,696
Less Than 12 Months, Unrealized Losses	(50)	(746)
12 Months or Greater, Estimated Fair Value	174,206	234,798
12 Months or Greater, Unrealized Losses	(394)	(1,321)
Total Estimated Fair Value	237,529	509,494
Total Unrealized Losses	(444)	(2,067)
Securities of government-sponsored entities
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Estimated Fair Value	0	4,999
Less Than 12 Months, Unrealized Losses	0	(1)
12 Months or Greater, Estimated Fair Value	10,979	10,947
12 Months or Greater, Unrealized Losses	(21)	(55)
Total Estimated Fair Value	10,979	15,946
Total Unrealized Losses	$ (21)	$ (56)

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	May 02, 2017
Debt Instrument [Line Items]
Convertible senior notes principal amount	$ 517,500	$ 517,500
2.25% Convertible Senior Notes due 2024
Debt Instrument [Line Items]
Convertible senior notes principal amount			$ 517,500
Convertible senior notes interest percentage			2.25%
Convertible senior notes convertible latest date	May 15, 2024
Convertible senior notes	7 years
2.25% Convertible Senior Notes due 2024 \| Significant Other Observable Inputs (Level 2)
Debt Instrument [Line Items]
Debt instrument fair value	$ 700,900	$ 616,100

Reconciliation of Our Investment in Restricted Equity Securities Measured at Fair Value on Quarterly Basis Using Significant Unobservable Inputs (Level 3) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Jan. 31, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment in restricted equity securities	$ 56,400		$ 0
Balance at March 31, 2019	56,400		0
Restricted equity securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment in restricted equity securities	56,400		0
Balance at March 31, 2019	56,400		$ 0
Restricted equity securities \| Fair Value Measurements Recurring \| Significant Unobservable Inputs (Level 3) \| Long-term investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment in restricted equity securities	56,400	$ 54,700
Unrealized gain recognized on restricted equity securities still held at March 31, 2019	1,700
Balance at March 31, 2019	$ 56,400	$ 54,700

Inventory - Summary of Inventory (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Raw materials	$ 7,733	$ 7,855
Work in process	4,458	2,208
Finished goods	819	801
Total inventory	$ 13,010	$ 10,864

Leases - Additional Information (Detail) $ in Thousands	1 Months Ended	3 Months Ended
Leases - Additional Information (Detail) $ in Thousands	Dec. 31, 2007 USD ($) Building	Mar. 31, 2019 USD ($) Building RenewalOption	Dec. 31, 2018 USD ($)	May 31, 2018 USD ($) ft²	Jun. 30, 2017 USD ($)	Dec. 31, 2008 USD ($)
Leases [Line Items]
Sale of facility and associated real property	$ 109,000
Mortgage debt retired	47,700
Cash received net of transaction costs and debt retirement	$ 61,000
Net deferred gain on real estate sale			$ 8,000			$ 39,100
Leaseback transaction lease period	12 years
Number of building leased \| Building	2	1
Number of vacated buildings \| Building		1
Letter of credit					$ 3,000
Number of times to renew the lease contract \| RenewalOption		2
Lease extension period		10 years
Lease description		At commencement of the lease, we were not reasonably certain to exercise either of the two 10-year extension options contained within the lease.
Operating lease cost		$ 1,900
Cash paid for cashflows from operating lease		1,600
Operating lease right of use asset		49,304	$ 0
Operating lease, liability		$ 70,414
Operating lease, weighted average remaining lease term		10 years 6 months 25 days
Operating lease, weighted average discount rate, percent		6.65%
Amended Lease Term
Leases [Line Items]
Lease expiration date		Dec. 31, 2029
Tenant improvement allowances					$ 13,100
Lease Agreement
Leases [Line Items]
Tenant improvement allowances				$ 4,200
Office space area leased \| ft²				44,718
Lease term				10 years 10 months
Lease Agreement \| Letter of Credit
Leases [Line Items]
Lease security deposit				$ 1,000

Leases - Summary of Minimum Lease Payments for Operating Lease Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Leases [Abstract]
2019 (9 months remaining)	$ 5,777
2020	8,399
2021	8,624
2022	8,888
2023	9,160
Thereafter	59,462
Total operating lease payments	100,310
Less accreted interest	(29,896)
Total operating lease liabilities	70,414
Less current operating lease liabilities	(3,267)
Noncurrent operating lease liabilities	$ 67,147	$ 0

Convertible Senior Notes - Additional Information (Detail) $ / shares in Units, shares in Millions		3 Months Ended
	May 02, 2017 USD ($)	Mar. 31, 2019 USD ($) d $ / shares shares	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Convertible senior notes principal amount		$ 517,500,000	$ 517,500,000
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 our 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
Threshold common stock trading days \| d		20
Convertible senior notes redemption rate		100.00%
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%

Convertible Senior Notes - Debt Net of Discounts and Deferred Financing Costs (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt Disclosure [Abstract]
Principal	$ 517,500	$ 517,500
Deferred financing costs	(7,985)	(8,326)
Debt discount, net	(116,080)	(120,678)
Net carrying amount	$ 393,435	$ 388,496

Net Loss Per Share - Schedule of Net Ioss Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Net loss - basic and diluted	$ (102,115)	$ (41,818)
Weighted-average common shares outstanding:
Basic and diluted	91,056	89,526
Net loss per share:
Basic and diluted	$ (1.12)	$ (0.47)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Net Loss Per Share - Additional Information (Details) shares in Millions	3 Months Ended
	Mar. 31, 2019 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

Net Loss Per Share - Schedule of Anti-Dilutive Shares Excluded from Diluted Per Share Amounts (Detail) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Stock Options Restricted Stock and Convertible Senior Notes
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from diluted per share amounts	8,299	8,176

Investments Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	$ 684.4	$ 725.2
Short-term investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	524.1	650.9
Short-term investments \| Cash and money market fund
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	72.8	141.7
Short-term investments \| Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	97.5	94.6
Short-term investments \| Securities of government-sponsored entities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	45.8	20.8
Short-term investments \| Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	308.0	393.8
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	4.0
Long-term investments \| Securities of government-sponsored entities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	43.1	64.8
Long-term investments \| Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	133.6	151.2
Long-term investments \| Restricted equity securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	56.4
Investments Including Cash Equivalents And Restricted Cash
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	762.7	872.4
Cash and Cash Equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	78.3	147.2
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	0.0
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	72.8	141.7
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	72.8	141.7
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 \| Securities of government-sponsored entities \| 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	4.0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Long-term investments \| Securities of government-sponsored entities \| 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) \| Long-term investments \| Restricted equity 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
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	78.3	147.2
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	78.3	147.2
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	628.0	725.2
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	451.3	509.2
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	97.5	94.6
Significant Other Observable Inputs (Level 2) \| Short-term investments \| Securities of government-sponsored entities \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	45.8	20.8
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	308.0	393.8
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 \| Securities of government-sponsored entities \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	43.1	64.8
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	133.6	151.2
Significant Other Observable Inputs (Level 2) \| Long-term investments \| Restricted equity 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
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	628.0	725.2
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	0.0
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	56.4	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 \| Securities of government-sponsored entities \| 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 \| Securities of government-sponsored entities \| 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) \| Long-term investments \| Restricted equity 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	56.4	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	56.4	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