Neurocrine Biosciences (NBIX) 10-K 8 Feb 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Feb. 01, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Trading Symbol	NBIX
Entity Registrant Name	NEUROCRINE BIOSCIENCES INC
Entity Central Index Key	914,475
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		90,821,267
Entity Public Float			$ 7,461,776,662

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 141,714	$ 254,712
Short-term investments, available-for-sale	509,199	261,217
Accounts receivable	56,240	31,127
Inventory	10,864	1,024
Other current assets	19,760	6,839
Total current assets	737,777	554,919
Property and equipment, net	33,869	10,811
Long-term investments, available-for-sale	216,028	247,361
Restricted cash	5,477	4,500
Total assets	993,151	817,591
Current liabilities:
Accounts payable and accrued liabilities	86,377	53,520
Other current liabilities	1,856	906
Total current liabilities	88,233	54,426
Deferred gain on sale of real estate	7,312	8,043
Deferred revenue	10,231	10,231
Deferred rent	18,114	3,135
Convertible senior notes	388,496	369,618
Total liabilities	512,386	445,453
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized; no shares issued and outstanding	0	0
Common stock, $0.001 par value; 220,000,000 shares authorized; issued and outstanding shares were 90,797,087 and 88,793,903 at December 31, 2018 and 2017, respectively	91	89
Additional paid-in capital	1,660,361	1,572,765
Accumulated other comprehensive loss	(1,932)	(1,850)
Accumulated deficit	(1,177,755)	(1,198,866)
Total stockholders’ equity	480,765	372,138
Total liabilities and stockholders’ equity	$ 993,151	$ 817,591

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	220,000,000	220,000,000
Common stock, shares issued	90,797,087	88,793,903
Common stock, shares outstanding	90,797,087	88,793,903

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Revenues	$ 451,240	$ 161,626	$ 15,000
Operating expenses:
Cost of sales	$ 4,889	$ 1,254	$ 0
Type of Cost, Good or Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Research and development	$ 160,524	$ 121,827	$ 94,291
Sales, general and administrative	248,932	169,906	68,081
Total operating expenses	414,345	292,987	162,372
Income (loss) from operations	36,895	(131,361)	(147,372)
Other (expense) income:
Interest expense	(30,530)	(19,523)	0
Investment income and other, net	15,476	8,342	6,282
Total other (expense) income	(15,054)	(11,181)	6,282
Income (loss) before provision for income taxes	21,841	(142,542)	(141,090)
Provision for income taxes	730	0	0
Net income (loss)	$ 21,111	$ (142,542)	$ (141,090)
Net income (loss) per share:
Basic	$ 0.23	$ (1.62)	$ (1.63)
Diluted	$ 0.22	$ (1.62)	$ (1.63)
Shares used in the calculation of net income (loss) per share:
Weighted average common shares outstanding, basic	90,235	88,089	86,713
Weighted average common shares outstanding, diluted	95,386	88,089	86,713
Other comprehensive income (loss):
Net income (loss)	$ 21,111	$ (142,542)	$ (141,090)
Unrealized (loss) gain on available-for-sale securities	(82)	(1,532)	659
Comprehensive income (loss)	21,029	(144,074)	(140,431)
Product sales, net
Revenues:
Revenues	409,608	116,626	0
Collaboration revenue
Revenues:
Revenues	$ 41,632	$ 45,000	$ 15,000

Consolidated Statements of Stoc

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, 2015	$ 424,454	$ 86	$ 1,340,579	$ (977)	$ (915,234)
Begining balance (in shares) at Dec. 31, 2015		86,263
Net income (loss)	(141,090)	$ 0	0	0	(141,090)
Unrealized gains (losses) on available for sale investments	659	0	0	659	0
Share-based compensation expense	28,464	0	28,464	0	0
Issuance of common stock for vested restricted stock units	0	$ 0	0	0	0
Issuance of common stock for vested restricted stock units (in shares)		284
Issuance of common stock for stock option exercises	$ 2,390	$ 1	2,389	0	0
Issuance of common stock for stock option exercises (in shares)	341	336
Ending balance at Dec. 31, 2016	$ 314,877	$ 87	1,371,432	(318)	(1,056,324)
Ending balance (in shares) at Dec. 31, 2016		86,883
Net income (loss)	(142,542)	$ 0	0	0	(142,542)
Unrealized gains (losses) on available for sale investments	(1,532)	0	0	(1,532)	0
Share-based compensation expense	42,522	0	42,522	0	0
Issuance of common stock for vested restricted stock units	1	$ 1	0	0	0
Issuance of common stock for vested restricted stock units (in shares)		562
Issuance of common stock for stock option exercises	$ 13,864	$ 1	13,863	0	0
Issuance of common stock for stock option exercises (in shares)	1,353	1,349
Equity component of convertible debt, net of issuance costs	$ 144,948	$ 0	144,948	0	0
Ending balance at Dec. 31, 2017	372,138	$ 89	1,572,765	(1,850)	(1,198,866)
Ending balance (in shares) at Dec. 31, 2017		88,794
Net income (loss)	21,111	$ 0	0	0	21,111
Unrealized gains (losses) on available for sale investments	(82)	0	0	(82)	0
Share-based compensation expense	58,068	0	58,068	0	0
Issuance of common stock for vested restricted stock units	0	$ 0	0	0	0
Issuance of common stock for vested restricted stock units (in shares)		429
Issuance of common stock for stock option exercises	$ 29,530	$ 2	29,528	0	0
Issuance of common stock for stock option exercises (in shares)	1,592	1,574
Ending balance at Dec. 31, 2018	$ 480,765	$ 91	$ 1,660,361	$ (1,932)	$ (1,177,755)
Ending balance (in shares) at Dec. 31, 2018		90,797

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (loss)	$ 21,111	$ (142,542)	$ (141,090)
Reconciliation of net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	4,024	2,400	1,453
Amortization of debt discount	17,552	10,937	0
Amortization of debt issuance costs	1,326	848	0
Amortization of premiums on investments	1,449	1,756	3,520
Share-based compensation expense	58,068	42,522	28,464
Deferred rent	351	1,203	(294)
Gain on sales of assets, net	(760)	(2,104)	(3,431)
Cease-use expense	0	(544)	(584)
Change in operating assets and liabilities:
Accounts receivable	(25,113)	(31,127)	0
Inventory	(3,524)	(1,024)	0
Reimbursements for tenant improvements	8,701	0	0
Accounts payable and accrued liabilities	24,223	27,338	4,398
Other current assets and liabilities, net	(6,044)	(3,994)	1,383
Net cash provided by (used in) operating activities	101,364	(94,331)	(106,181)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of investments	(545,962)	(583,408)	(298,776)
Sales and maturities of investments	327,825	339,088	415,826
Purchases of property and equipment	(24,812)	(6,940)	(4,108)
Proceeds from sales of property and equipment	34	7	13
Net cash (used in) provided by investing activities	(242,915)	(251,253)	112,955
CASH FLOWS FROM FINANCING ACTIVITIES
Issuance of common stock	29,530	13,865	2,390
Proceeds from issuance of senior convertible notes, net	0	502,781	0
Net cash provided by financing activities	29,530	516,646	2,390
Net change in cash, cash equivalents, and restricted cash	(112,021)	171,062	9,164
Cash, cash equivalents, and restricted cash at beginning of the period	259,212	88,150	78,986
Cash, cash equivalents, and restricted cash at end of the period	147,191	259,212	88,150
SUPPLEMENTAL DISCLOSURES
Cash paid for interest	11,644	6,242	0
Non-cash capital expenditures	$ 2,318	$ 0	$ 0

ORGANIZATION AND SUMMARY OF SIG

ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	NOTE 1. ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Business Activities. Neurocrine Biosciences, Inc. (the Company or Neurocrine) was incorporated in California in 1992 and reincorporated in Delaware in 1996. Neurocrine Continental, Inc., is a Delaware corporation and a wholly owned subsidiary of the Company. The Company also has two wholly-owned Irish subsidiaries, Neurocrine Therapeutics, Ltd. and Neurocrine Europe, Ltd. both of which were formed in December 2014 and are inactive. The Company discovers, develops, and commercializes innovative and life-changing pharmaceuticals, in diseases with high unmet medical needs, through its novel research and development (R&D) platform, focused on neurological and endocrine related diseases and disorders. The Company discovered, developed, and markets INGREZZA ® ® Principles of Consolidation. The consolidated financial statements include the accounts of Neurocrine as well as its wholly owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. Use of Estimates. The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (GAAP) requires management to make estimates and assumptions that affect the amounts reported in the financial statements and the accompanying notes. Actual results could differ from those estimates. Industry Segment and Geographic Information. The Company operates in a single industry segment – the discovery, development, and marketing of pharmaceuticals for the treatment of neurological and endocrine based diseases and disorders. The Company had no foreign based operations during any of the years presented. Cash Equivalents. The Company considers all highly liquid investments that are readily convertible into cash and have an original maturity of three months or less at the time of purchase to be cash equivalents . Short-Term and Long-Term Investments Available-for-Sale. Certain investments are classified as available-for-sale and carried at fair value, with any unrealized gains and losses reported in other comprehensive loss. The amortized cost of investments in debt securities is adjusted for the amortization of premiums and accretion of discounts to maturity, which are included in investment income and other, net. The cost of investments in debt securities sold is based on the specific identification method. Realized gains and losses, interest and dividends, 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. Accounts Receivable. Accounts receivable are recorded net of customer allowances for prompt payment discounts, chargebacks, and any allowance for doubtful accounts. The Company estimates the allowance for doubtful accounts based on existing contractual payment terms, actual payment patterns of its customers, and individual customer circumstances. To date, an allowance for doubtful accounts has not been required. Fair Value of Financial Instruments. Certain financial instruments, including cash, cash equivalents, accounts receivable, accounts payable, and accrued liabilities are carried at cost, which the Company believes approximates fair value because of the short-term nature of these instruments. 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 is estimated utilizing market quotations from an over-the-counter trading market and approximated 119% and 128% of the face value of the 2024 Notes at December 31, 2018 and 2017, respectively. Inventory. Inventory is stated at the lower of cost or estimated net realizable value. The Company currently uses actual costing to determine the cost basis for its inventory. Inventory is valued on a first-in, first-out basis and consists primarily of third-party manufacturing costs. The Company capitalizes inventory costs associated with its products upon regulatory approval when, based on management’s judgment, future commercialization is considered probable and the future economic benefit is expected to be realized; otherwise, such costs are expensed. Prior to FDA approval of INGREZZA, all costs related to its manufacture were included in R&D expense in the period incurred. Historically, the Company’s physical inventory included active pharmaceutical ingredients produced prior to FDA approval of INGREZZA and accordingly had no cost basis as the cost associated with producing this material was expensed in the period incurred. Costs associated with the manufacture of bulk drug product, finished bottling, and other labeling activities that occurred post FDA approval of INGREZZA are included in the inventory value. The Company reduces its inventory to net realizable value for potential excess, dated, or obsolete inventory based on an analysis of forecasted demand compared to quantities on hand and any firm purchase orders, as well as product shelf life. To date, such reserves have not been significant. Property and Equipment. Property and equipment are stated at cost and depreciated over the estimated useful lives of the assets using the straight-line method. Equipment is depreciated over an average estimated useful life of 3 to 7 years. Leasehold improvements are depreciated over the shorter of their estimated useful lives or the remaining lease term. Depreciation expense was $4.0 million for 2018, $2.4 million for 2017, and $1.5 million for 2016. Impairment of Long-Lived Assets. The Company reviews long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable. If indicators of impairment exist, the Company assesses the recoverability of the affected long-lived assets by determining whether the carrying value of such assets can be recovered through undiscounted future operating cash flows. If the carrying amount is not recoverable, the Company measures the amount of any impairment by comparing the carrying value of the asset to the present value of the expected future cash flows associated with the use of the asset. Revenue Recognition. The Company recognizes revenue when the customer obtains control of the product in an amount that reflects the consideration the Company expects to receive from the customer in exchange for that product. To determine revenue recognition, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the Company satisfies the performance obligation. The Company only applies the five-step model to contracts when it is probable that the Company will collect the consideration it is entitled to in exchange for the good transferred to the customer. Once a contract is determined to be within the scope of Accounting Standards Codification 606, Revenue from Contracts with Customers (Topic 606), at contract inception, the Company assesses the goods promised within the contract to determine those that are performance obligations and assesses whether each promised good is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. Product Sales, Net. The Company’s product sales consist of sales of INGREZZA in the U.S. INGREZZA was approved by the FDA on April 11, 2017 and the Company commenced shipments of INGREZZA to specialty pharmacies (SPs) and a specialty distributor (SD) (collectively, customers) in April 2017. The SPs dispense product to a patient based on the fulfillment of a prescription and the SD sells product to closed-door pharmacies and government facilities. The Company’s agreements with the customers provide for transfer of title to the product at the time the product is delivered to the customers. In addition, except for limited circumstances, the customers have no right of product return. Product sales are recognized when the customers obtain control of the Company’s product, typically upon delivery to the customers. Revenue from product sales are recorded at the net sales price (transaction price), which includes an estimate of variable consideration for which reserves are established and which results from contractual discounts, returns, chargebacks, rebates, co-pay assistance, and other allowances relating to sales of the Company’s products. These reserves are based on the amounts earned or to be claimed on the related sales and are classified as reductions of accounts receivable (if the amounts are payable to the customers) or a current liability (if the amounts are payable to parties other than the customers). Where appropriate, these estimates take into consideration a range of possible outcomes that are probability-weighted for relevant factors such as the Company’s historical experience, current contractual and statutory requirements, specific known market events and trends, industry data, and forecasted customer buying and payment patterns. Overall, these reserves reflect the Company’s best estimates of the amount of consideration to which it is entitled based on the terms of the contract. The amount of variable consideration that is included in the transaction price may be constrained and is included in the net sales price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. Actual amounts of consideration ultimately received may differ from the Company’s estimates. If actual results in the future vary from the Company’s estimates, the Company will adjust these estimates, which would affect net product revenue and earnings in the period such variances become known. Shipping and handling costs related to the Company’s product sales are included in sales, general and administrative expenses. Collaborative and Other Revenue. The Company enters into collaboration and licensing agreements under which it licenses certain rights to its product candidates to third parties. The terms of these arrangements typically include payment to the Company of one or more of the following: non-refundable, up-front license fees; development, regulatory, and commercial milestone payments; payments for manufacturing supply services; and royalties on net sales of licensed products. As part of the accounting for these arrangements, the Company develops assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company uses key assumptions to determine the stand-alone selling price, which may include forecasted revenues, development timelines, reimbursement rates for personnel costs, discount rates, and probabilities of technical and regulatory success. Royalty Revenue : For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). Sales-based royalties for ORILISSA are calculated as a percentage of AbbVie net sales as defined in the Company’s agreement with AbbVie. Each quarterly period, sales-based royalties are recorded based on estimated quarterly net sales of ORILISSA. Differences between actual results and estimated amounts are adjusted for in the period in which they become known, which typically follows the quarterly period in which the estimate was made. Licenses of Intellectual Property : If the license to the Company’s intellectual property embedded within a collaboration and/or licensing arrangement is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from non-refundable, up-front fees allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The Company receives payments from its licensees based on billing schedules established in each agreement. Up-front payments and fees are recorded as deferred revenue upon receipt, or when due, and may require deferral of revenue recognition to a future period until the Company performs its obligations under these arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional. Milestone Payments : At the inception of each arrangement that includes development, commercialization, and regulatory milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. Performance milestone payments represent a form of variable consideration. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the Company’s control or that of the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The transaction price is then allocated to each performance obligation on a relative stand-alone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such development milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect milestone and license fees revenues and earnings in the period of adjustment. Manufacturing Supply Services : Arrangements that include a promise for future supply of drug substance or drug product for either clinical development or commercial supply at the licensee’s discretion are generally considered as options. The Company assesses if these options provide a material right to the licensee and if so, they are accounted for as separate performance obligations. Concentration of Credit Risk. The Company does not currently have any of its own manufacturing facilities, and therefore it depends on an outsourced manufacturing strategy for the production of INGREZZA for commercial use and for the production of its product candidates for clinical trials. The Company has contracts in place with one third-party manufacturer that is approved for the commercial production of INGREZZA’s capsules at 2 separate sites and one third-party manufacturer that is approved for the production of INGREZZA’s active pharmaceutical ingredient. Although there are potential sources of supply other than the Company’s existing suppliers, any new supplier would be required to qualify under applicable regulatory requirements. The Company has entered into distribution agreements with a limited number of SPs and SDs, and all of the Company’s product sales are to these customers. The Company’s 3 largest customers represented 93% of the Company’s product revenue for the year ended December 31, 2018 and 2017 and substantially all of the Company’s accounts receivable balance at December 31, 2018 and 2017. Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash, cash equivalents, investments, and accounts receivables. The Company established guidelines to limit its exposure to credit risk by placing investments with high credit quality financial institutions, diversifying its investment portfolio and placing investments with maturities that maintain safety and liquidity. Cost of Sales. Cost of sales includes third-party manufacturing, transportation, freight, and indirect overhead costs associated with the manufacture and distribution of INGREZZA, sales-based license costs on AbbVie net sales of ORILISSA, as defined in the Company’s agreement with AbbVie, and period costs resulting from certain inventory manufacturing services and variances and adjustment charges. A portion of the costs associated with the manufacture of INGREZZA sold to date was expensed as R&D prior to the FDA’s approval of INGREZZA and is therefore excluded from cost of sales during this period. Research and Development Expenses. R&D expenses consist primarily of salaries, payroll taxes, employee benefits, and share-based compensation charges for those individuals involved in ongoing research and development efforts; as well as scientific consulting fees, preclinical and clinical trial costs, R&D facilities costs, laboratory supply costs, and depreciation of scientific equipment. All such costs are charged to R&D expense as incurred. These expenses result from the Company’s independent R&D efforts, as well as efforts associated with collaborations, in-licenses, and third-party funded research arrangements. Advertising Expense. In connection with the FDA approval and commercial launch of INGREZZA in April 2017, the Company began to incur advertising costs, which are expensed when services are performed, or goods are delivered. The Company incurred advertising costs related to its marketed product, INGREZZA, of $20.5 million in 2018 and $10.1 million in 2017. Share-Based Compensation. The Company grants stock options to purchase its common stock to eligible employees and directors and also grants certain employees restricted stock units (RSUs) and performance-based restricted stock units (PRSUs). Additionally, the Company allows employees to participate in an employee stock purchase plan (ESPP). The Company estimates the fair value of stock options and shares to be issued under the ESPP using the Black-Scholes option-pricing model on the date of grant. Restricted stock units are valued based on the closing price of the Company’s common stock on the date of grant. The fair value of equity instruments expected to vest are recognized and amortized on a straight-line basis over the requisite service period of the award, which is generally 3 to 4 years; however, certain provisions in the Company’s equity compensation plans provide for shorter vesting periods under certain circumstances. The fair value of shares to be issued under the ESPP are recognized and amortized on a straight-line basis over the purchase period, which is generally 6 months. Additionally, the Company granted certain PRSUs that vest upon the achievement of certain pre-defined company-specific performance-based criteria. Expense related to these PRSUs is generally recognized ratably over the expected performance period once the pre-defined performance-based criteria for vesting becomes probable. Net Income (Loss) Per Share. Basic net income (loss) per share is computed using the weighted average number of common shares outstanding during the period. Diluted net income per share is computed using the weighted average number of common and potentially dilutive shares outstanding during the period, including the potentially dilutive shares resulting from the conversion of the 2024 Notes, and excluding the effect of stock options and restricted stock outstanding for periods when their effect is anti-dilutive, using the treasury stock method. Convertible debt instruments that may be settled entirely or partly in cash (such as the 2024 Notes) may, in certain circumstances where the borrower has the ability and intent to settle in cash, be accounted for under the treasury stock method. The Company issued the 2024 Notes with a combination settlement feature, which the Company has the ability and intent to use upon conversion of the notes, to settle the principal amount of debt for cash and the excess of the principal portion in shares of its common stock. As a result, of the approximately 6.8 million shares underlying the 2024 Notes, only the shares required to settle the excess of the principal portion would be considered dilutive under the treasury stock method. Further, approximately 0.3 million PRSUs have been excluded from the calculation of diluted net income per share as the performance condition has not been achieved. In loss periods, basic net loss per share and diluted net loss per share are identical because the otherwise dilutive potential common shares become anti-dilutive and are therefore excluded. Recently Adopted Accounting Pronouncements. In May 2014, the Financial Accounting Standards Board (FASB) issued Account Standards Update (ASU) No. 2014-09, “Revenue from Contracts with Customers (Topic 606)”, which supersedes all existing revenue recognition requirements, including most industry-specific guidance. This new standard amends the guidance for the recognition of revenue from contracts with customers to transfer goods and services. The FASB subsequently issued additional, clarifying standards to address issues arising from implementation of the new revenue recognition standard. The Company adopted this standard on January 1, 2018, using the modified retrospective method, and applied the standard only to contracts that were not completed prior to January 1, 2018. The adoption of the new revenue standard did not change the Company’s revenue recognition. As the Company did not identify any accounting changes that impacted the amount of reported revenues with respect to product revenues, or revenue from collaboration and license agreements, no adjustment to retained earnings was required upon adoption. In November 2016, the FASB issued ASU 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash”, which clarifies the presentation of restricted cash and restricted cash equivalents in the statements of cash flows. Under this ASU, restricted cash and restricted cash equivalents are included with cash and cash equivalents when reconciling the beginning and end-of-period total amounts presented on the statements of cash flows. This ASU is intended to reduce diversity in practice in the classification and presentation of changes in restricted cash on the statement of cash flows. This ASU requires that the statement of cash flows explain the change in total cash and equivalents and amounts generally described as restricted cash or restricted cash equivalents when reconciling the beginning and end-of-period total amounts. This ASU also requires a reconciliation between the total of cash and equivalents and restricted cash presented on the statement of cash flows and the cash and equivalents balance presented on the balance sheet. This amended guidance was retrospectively adopted on January 1, 2018 and requires that cash, cash equivalents, and restricted cash reported on the consolidated statements of cash flows now includes restricted cash of $5.5 million as of December 31, 2018 and $4.5 million as of December 31, 2017, as well as previously reported cash and cash equivalents. Recently Issued Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, “Leases (Topic 842)”, which requires lessees to recognize leases on the balance sheet and disclose key information about leasing arrangements. Topic 842 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. Topic 842 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. Topic 842 is effective for the Company beginning January 1, 2019, using a modified retrospective approach, with early adoption permitted. An entity may choose to use either the effective date or the beginning of the earliest comparative period presented in the financial statements as the date of initial application. The Company expects to adopt Topic 842 on January 1, 2019, using a modified retrospective approach, and to choose the effective date as the date of initial application. Consequently, financial information will not be updated, and the disclosures required under Topic 842 will not be provided for dates and periods prior to January 1, 2019. Topic 842 provides a number of optional practical expedients and accounting policy elections. The Company expects to elect 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. Further, the Company expects to elect accounting policies not to apply the recognition requirements under Topic 842 to any of the Company’s short-term leases, instead recognizing the lease payments in profit or loss on a straight-line basis over the lease term, and to account for each separate lease and associated nonlease components as a single lease component for all of its leases. The Company expects Topic 842 will have a material effect on its consolidated balance sheets. However, the Company does not expect Topic 842 will have a material effect on its consolidated statements of operations and comprehensive income (loss) or consolidated statements of cash flows. While the Company continues to assess all of the effects of adoption, the most significant effects relate to (1) the recognition of right-of-use (ROU) assets of approximately $49 million and lease liabilities of approximately $69 million, primarily resulting from leases of office and laboratory space; (2) the recognition of an existing deferred gain on a sale of real estate of approximately $8 million as a cumulative-effect adjustment to equity; (3) the derecognition of deferred rent of approximately $20 million for certain lease incentives received; and (4) significant new disclosure requirements. 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. This ASU does not apply to share-based payments used to effectively provide financing to the issuer or awards granted in conjunction with selling goods or services to customers as part of a contract accounted for under Topic 606. This update is effective for public business entities for fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. The Company does not expect this update will have a material impact on its consolidated financial statements and related disclosures.

SIGNIFICANT COLLABORATIVE RESEA

SIGNIFICANT COLLABORATIVE RESEARCH AND DEVELOPMENT AGREEMENTS	12 Months Ended
	Dec. 31, 2018
Text Block [Abstract]
SIGNIFICANT COLLABORATIVE RESEARCH AND DEVELOPMENT AGREEMENTS	NOTE 2. SIGNIFICANT COLLABORATIVE RESEARCH AND DEVELOPMENT AGREEMENTS Mitsubishi Tanabe Pharma Corporation. During 2015, the Company entered into a collaboration and license agreement with Mitsubishi Tanabe Pharma Corporation (Mitsubishi Tanabe) for the development and commercialization of INGREZZA for movement disorders in Japan and other select Asian markets. Mitsubishi Tanabe made an up-front license fee of $30 million and has agreed to make payments up to $85 million in development and commercialization event-based payments, payments for the manufacture of pharmaceutical products, and royalties on product sales in select territories in Asia. Under the terms of the agreement, Mitsubishi Tanabe is responsible for all third-party development, marketing and commercialization costs in Japan and other select Asian markets and the Company would be entitled to a percentage of sales of INGREZZA in Japan and other select Asian markets for the longer of ten years or the life of the related patent rights. Further, the collaboration effort between the parties to advance INGREZZA towards commercialization in Japan and other select Asian markets is governed by joint steering and development committees with representatives from both parties. There are no performance, cancellation, termination, or refund provisions in the agreement that would have a material financial consequence to the Company. The Company does not directly control when event-based payments will be achieved or when royalty payments will begin. Mitsubishi Tanabe may terminate the agreement at its discretion upon 180 days written notice to the Company. In such event, all INGREZZA product rights for Japan and other select Asian markets would revert to the Company. The Company assessed this arrangement in accordance with Topic 606 and identified the following performance obligations: (i) INGREZZA technology license and existing know-how; and (ii) development activities to initiate a clinical trial of INGREZZA for Huntington’s chorea, at an estimated cost of approximately $12 million, should Mitsubishi Tanabe request. The Company has the option to participate on the joint steering committee, but since participation is at its option it was deemed to not be a performance obligation. The option for Mitsubishi Tanabe to engage the Company to manufacture and supply pharmaceutical products, not at a discount, was not considered a material right and therefore not a performance obligation. Based on these assessments, the Company identified the license and the development activities as the only performance obligations at the inception of the agreement, which were both deemed to be distinct. To evaluate the appropriate transaction price, the Company determined that the up-front amount constituted the entirety of the consideration to be included in the transaction price and to be allocated to the performance obligations based on the Company’s best estimate of their relative stand-alone selling prices. For the license, the stand-alone selling price was calculated using an income approach model and included the following key assumptions: the development timeline, revenue forecast, discount rate, and probabilities of technical and regulatory success. The relative selling price of the Company’s development activities to initiate a clinical trial of INGREZZA for Huntington’s chorea was based on an assessment of costs to perform the study, based upon a peer company analysis for similar studies. The Company believes a change in the assumptions used to determine its stand-alone selling price for the license most likely would not have a significant effect on the allocation of consideration received (or receivable) to the performance obligations. At execution, the transaction price included only the $30 million up-front consideration received. None of the development or regulatory milestones have been included in the transaction price, as all milestone amounts were fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including that achievement of the milestones is outside of its control and contingent upon success in future clinical trials and the licensee’s efforts. Any consideration related to sales-based milestones (including royalties) will be recognized when the related sales occur as they were determined to relate predominantly to the license granted to Mitsubishi Tanabe and therefore have also been excluded from the transaction price. The Company will re-evaluate the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. To date, the Company has recognized revenue under this agreement of $19.8 million associated with the delivery of a technology license and existing know-how, and $15 million in development event-based payments resulting from Mitsubishi Tanabe’s initiation of Phase II/III development of INGREZZA in tardive dyskinesia (TD) in Asia. In accordance with the Company’s continuing performance obligations, $10.2 million of the $30 million up-front payment is being deferred and recognized in future periods. Under the terms of the agreement, there is no general obligation to return the up-front payment for any non-contingent deliverable. No revenue was recognized under the Mitsubishi Tanabe agreement for 2018 or 2016. In 2017, the Company recognized $15 million in development event-based payments resulting from Mitsubishi Tanabe’s initiation of Phase II/III development of INGREZZA in TD in Asia. AbbVie. In June 2010, the Company announced an exclusive worldwide collaboration with AbbVie, to develop and commercialize elagolix and all next-generation gonadotropin-releasing factor (GnRH) antagonists (collectively, GnRH Compounds) for women’s and men’s health. AbbVie made an upfront payment of $75 million and has agreed to make additional development and regulatory event-based payments of up to $480 million, of which $115 million has been earned as of December 31, 2018, and up to an additional $50 million in commercial event-based payments. Under the terms of the agreement, AbbVie is responsible for all third-party development, marketing and commercialization costs. The Company will be entitled to a percentage of worldwide sales of GnRH Compounds for the longer of ten years or the life of the related patent rights. AbbVie may terminate the collaboration at its discretion upon 180 days written notice to the Company. In such event, the Company would be entitled to specified payments for ongoing clinical development and related activities and all GnRH Compound product rights would revert to the Company. The Company evaluated the terms of this agreement under Topic 606 and determined that there is one performance obligation, the exclusive worldwide license with rights to develop, manufacture, and commercialize elagolix. At execution, the transaction price included only the $75 million up-front consideration received. None of the development or regulatory milestones were included in the transaction price, as all milestone amounts were fully constrained. As part of the Company’s evaluation of the constraint, the Company considered numerous factors, including that achievement of the milestones is outside of its control and contingent upon success in future clinical trials and the licensee’s efforts. Any consideration related to sales-based milestones (including royalties) will be recognized when the related sales occur as they were determined to relate predominantly to the license granted to AbbVie and therefore have also been excluded from the transaction price. The Company will re-evaluate the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. On July 24, 2018, AbbVie received approval from the FDA for ORILISSA for the management of moderate to severe endometriosis pain in women, resulting in the achievement of a $40 million event-based milestone, which the Company recognized as revenue for 2018. The Company also recognized sales-based royalties on AbbVie net sales of ORILISSA of approximately $1.6 million for 2018. In 2017, event-based revenue of $30 million was recognized based on AbbVie’s new drug application (NDA) submission for elagolix in endometriosis being accepted by the FDA. In 2016, event-based revenue of $15 million was recognized related to AbbVie’s initiation of Phase III development of elagolix in uterine fibroids. BIAL – Portela & Ca, S.A. In February 2017, the Company 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 Parkinson’s disease, in the U.S. and Canada. The Company paid BIAL an upfront license fee of $30 million, which was expensed in 2017 as in-process R&D. During the first quarter of 2018, the FDA provided guidance on the regulatory path forward to support an NDA for opicapone for Parkinson’s Disease, in which the FDA did not request that the Company conduct an additional Phase III study, resulting in a $10 million event-based milestone payment to BIAL, which was expense as incurred. The Company may be required to pay up to an additional $105 million in milestone payments associated with the regulatory approval and net sales of opicapone. Prior to FDA approval of opicapone, the Company may also be required to pay up to an additional $10 million in milestones based on certain regulatory and clinical results and FDA acceptance of the Company’s NDA submission for opicapone. Upon commercialization of opicapone, the Company agreed to determine certain annual sales forecasts. In the event the Company fails to meet the minimum sales requirements for a particular year, it would be required to pay BIAL an amount equal to the difference between the actual net sales and minimum sales requirements for such year. In the event the Company fails to meet the minimum sales requirements for any two years, BIAL may terminate the agreement. Under the terms of the agreement, the Company is responsible for the management and cost of all opicapone development and commercialization activities in the U.S. and Canada. Further, unless terminated earlier, the agreement will continue on a licensed product-by-product and country-by-country basis until a generic product in respect of such licensed product under the agreement is sold in a country and sales of such generic product are greater than a specified percentage of total sales of such licensed product in such country. Upon the Company’s written request prior to the estimated expiration of the term in respect of a licensed product, the parties shall negotiate a good faith continuation of BIAL’s supply of such licensed product after the term. After the term, and if BIAL is not supplying a certain licensed product, the Company shall pay BIAL a trademark royalty based on the net sales of such licensed product. Either party may terminate the agreement earlier if the other party materially breaches the agreement and does not cure the breach within a specified notice period, or upon the other party’s insolvency. BIAL may terminate the agreement if the Company fails to use commercially reasonable efforts or to submit an NDA for a licensed product by a specified date or under certain circumstances involving a change of control of the Company. In certain circumstances where BIAL elects to terminate the agreement in connection with the Company’s change of control, BIAL shall pay the Company a termination fee. The Company may terminate the agreement at any time for any reason upon six months written notice to BIAL if prior to the first NDA approval in the U.S., and upon 9 months written notice to BIAL if such notice is given after the first NDA approval in the U.S. If the Company’s termination request occurs prior to the first NDA approval in the U.S., it shall pay BIAL a termination fee except under certain conditions specified in the agreement.

INVESTMENTS

INVESTMENTS	12 Months Ended
	Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
INVESTMENTS	NOTE 3. INVESTMENTS Available-for-sale securities are carried at fair value, with the unrealized gains and losses reported in comprehensive income (loss). The amortized cost of debt securities in this category is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion are included in investment income. Realized gains and losses and declines in value judged to be other-than-temporary, if any, on available-for-sale securities are included in investment income 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. Investments at December 31, 2018 and 2017 consisted of the following: December 31, (in thousands) 2018 2017 Commercial paper $ 94,572 $ 75,362 Corporate debt securities 544,978 414,815 Securities of government-sponsored entities 85,677 18,401 Total investments $ 725,227 $ 508,578 The following is a summary of investments classified as available-for-sale securities: (in thousands) Contractual Maturity (in years) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Aggregate Estimated Fair Value 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 December 31, 2017: Classified as current assets: Commercial paper Less than 1 $ 75,396 $ 1 $ (35 ) $ 75,362 Corporate debt securities Less than 1 178,776 — (400 ) 178,376 Securities of government-sponsored entities Less than 1 7,503 — (24 ) 7,479 Total short-term available-for-sale securities $ 261,675 $ 1 $ (459 ) $ 261,217 Classified as non-current assets: Corporate debt securities 1 to 2 $ 237,749 $ — $ (1,310 ) $ 236,439 Securities of government-sponsored entities 1 to 2 11,004 — (82 ) 10,922 Total long-term available-for-sale securities $ 248,753 $ — $ (1,392 ) $ 247,361 The following table presents gross unrealized losses and fair value for those available-for-sale investments that were in an unrealized loss position as of December 31, 2018 and 2017, 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 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 ) December 31, 2017: Commercial paper $ 62,602 $ (35 ) $ — $ — $ 62,602 $ (35 ) Corporate debt securities 386,728 (1,660 ) 28,087 (50 ) 414,815 (1,710 ) Securities of government-sponsored entities 10,922 (82 ) 7,479 (24 ) 18,401 (106 ) Total $ 460,252 $ (1,777 ) $ 35,566 $ (74 ) $ 495,818 $ (1,851 ) At each reporting date, the Company performs 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 the Company’s intent and ability to hold the investment until recovery of its amortized cost basis. The Company intends, and has the ability, to hold its investments in unrealized loss positions until their amortized cost basis has been recovered. Based on its evaluation, the Company determined that its unrealized losses were not other-than-temporary at December 31, 2018 and 2017.

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	NOTE 4. FAIR VALUE MEASUREMENTS Fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, a three-tier fair value hierarchy has been established, which prioritizes the inputs used in measuring fair value as follows: Level 1: Observable inputs such as quoted prices in active markets; Level 2: Inputs include quoted prices for similar instruments in active markets and/or quoted prices for identical or similar instruments in markets that are not active near the measurement date; and Level 3: Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions. The Company classifies cash equivalents and available-for-sale investments within Level 1 or Level 2. The fair value of the Company’s high-quality investment grade corporate debt securities is determined using proprietary valuation models and analytical tools. These valuation models and analytical tools use market pricing or prices for similar instruments that are both objective and publicly available, including matrix pricing or reported trades, benchmark yields, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids and/or offers. The Company did not reclassify any investments between levels in the fair value hierarchy during the years ended December 31, 2018 and 2017. The Company’s assets, which are measured at fair value on a recurring basis as of December 31, 2018 and 2017, were determined using the inputs described above: 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) 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, cash equivalents and restricted cash (147.2 ) (147.2 ) — — Total investments $ 725.2 $ — $ 725.2 $ — December 31, 2017: Classified as current assets: Cash and money market funds $ 170.2 $ 170.2 $ — $ — Commercial paper 159.9 — 159.9 — Securities of government-sponsored entities 7.5 — 7.5 — Corporate debt securities 178.4 — 178.4 — Subtotal 516.0 170.2 345.8 — Classified as long-term assets: Cash and money market funds 1.5 1.5 — — Certificates of deposit 3.0 3.0 — — Securities of government-sponsored entities 10.9 — 10.9 — Corporate debt securities 236.4 — 236.4 — Total 767.8 174.7 593.1 — Less cash, cash equivalents and restricted cash (259.2 ) (174.6 ) (84.6 ) — Total investments $ 508.6 $ 0.1 $ 508.5 $ — The fair value of the 2024 Notes, calculated utilizing market quotations from an over-the-counter trading market for these notes (Level 2), was approximately $616.1 million as of December 31, 2018 and $662.1 million as of December 31, 2017. Refer to Note 5 to the consolidated financial statements for more information on the 2024 Notes.

CONVERTIBLE SENIOR NOTES

CONVERTIBLE SENIOR NOTES	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
CONVERTIBLE SENIOR NOTES	NOTE 5. CONVERTIBLE SENIOR NOTES On May 2, 2017, the Company completed a private placement of $517.5 million in aggregate principal amount of 2.25% convertible senior notes due 2024 and entered into an indenture agreement that sets forth the details of all the terms and conditions of the 2024 Notes (2024 Indenture). The 2024 Notes accrue interest at a fixed rate of 2.25% per year, payable semiannually in arrears on May 15 and November 15 of each year, beginning on November 15, 2017. The 2024 Notes mature on May 15, 2024. The net proceeds from the issuance of the 2024 Notes were approximately $502.8 million, after deducting commissions and the offering expenses payable by the Company. Holders of the 2024 Notes may convert the 2024 Notes at any time prior to the close of business on the business day immediately preceding May 15, 2024, only under the following circumstances: (i) during any calendar quarter commencing after the calendar quarter ending on September 30, 2017 (and only during such calendar quarter), if the last reported sale price of the Company’s common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than 130% of the conversion price on each applicable trading day; (ii) during the 5 business-day period immediately after any 5 consecutive trading-day period (the measurement period) in which the trading price (as defined in the 2024 Indenture) per $1,000 principal amount of the 2024 Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of the Company’s common stock and the conversion rate on each such trading day; (iii) upon the occurrence of specified corporate events, including a merger or a sale of all or substantially all of the Company’s assets; or (iv) if the Company calls the 2024 Notes for redemption, until the close of business on the business day immediately preceding the redemption date. On or after January 15, 2024, until the close of business on the scheduled trading day immediately preceding May 15, 2024, holders may convert their 2024 Notes at any time. 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 (VWAP) for each of the 30 consecutive trading days during the observation period. For both the principal and excess conversion value, holders may receive cash, shares of the Company’s common stock or a combination of cash and shares of its common stock, at the Company’s option. It is the Company’s intent and policy to settle conversions through combination settlement, which essentially involves repayment of an amount of cash equal to the “principal portion” and delivery of the “share amount” in excess of the principal portion in shares of common stock or cash. In general, for each $1,000 in principal, the “principal portion” of cash upon settlement is defined as the lesser of $1,000, and the conversion value during the 25-day observation period as described in the indenture for the notes. The conversion value is the sum of the daily conversion value which is the product of the effective conversion rate divided by 25 days and the daily VWAP of the Company’s common stock. The “share amount” is the cumulative “daily share amount” during the observation period, which is calculated by dividing the daily VWAP into the difference between the daily conversion value (i.e., conversion rate x daily VWAP) and $1,000. The initial conversion rate for the 2024 Notes is 13.1711 shares of common stock per $1,000 principal amount, which is equivalent to an initial conversion price of approximately $75.92 per share of the Company’s common stock. At the initial conversion rate, settlement of the 2024 Notes for shares of the Company’s common stock would approximate 6.8 million shares. The conversion rate will be subject to adjustment in some events but will not be adjusted for any accrued and unpaid interest. The initial conversion price of the 2024 Notes represented a premium of approximately 42.5% to the closing sale price of $53.28 per share of the Company’s common stock on the Nasdaq Global Select Market on April 26, 2017, the date the Company priced the private offering of the 2024 Notes. In the event of conversion, holders would forgo all future interest payments, any unpaid accrued interest and the possibility of further stock price appreciation. Upon the receipt of conversion requests, the settlement of the 2024 Notes will be paid pursuant to the terms of the 2024 Indenture. In the event that all of the 2024 Notes are converted, the Company would be required to repay the $517.5 million in principal value and any conversion premium in any combination of cash and shares of its common stock (at the Company’s option). On or after, but not prior to May 15, 2021, the Company may redeem for cash all or part of the 2024 Notes if the last reported sale price (as defined in the 2024 Indenture) of its common stock has been at least 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading-day period ending on, and including, the trading day immediately before the date which the Company provides notice of redemption. The redemption price will equal the sum of (i) 100% of the principal amount of the 2024 Notes being redeemed, plus (ii) accrued and unpaid interest, including additional interest, if any, to, but excluding, the redemption date. No sinking fund is provided for the 2024 Notes. If the Company undergoes a fundamental change, as defined in the 2024 Indenture, subject to certain conditions, holders of the 2024 Notes may require the Company to repurchase for cash all or part of their 2024 Notes at a repurchase price equal to 100% of the principal amount of the 2024 Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date. In addition, if a ‘‘make-whole fundamental change’’ (as defined in the 2024 Indenture) occurs prior to January 15, 2024, the Company will, in certain circumstances, increase the conversion rate for a holder who elects to convert the 2024 Notes in connection with the make-whole fundamental change. The 2024 Notes are the Company’s general unsecured obligations that rank senior in right of payment to all of its indebtedness that is expressly subordinated in right of payment to the 2024 Notes, and equal in right of payment to the Company’s unsecured indebtedness. While the 2024 Notes are currently classified as long-term on the Company’s 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 the Company’s 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. As of December 31, 2018, the fair value of the 2024 Notes, which was estimated utilizing market quotations from an over-the-counter trading market, approximated 119% of their face value. An entity must separately account for the liability and equity components of convertible debt instruments (such as the 2024 Notes) that may be settled entirely or partially in cash upon conversion in a manner that reflects the issuer’s economic interest cost. The liability component of the instrument was valued in a manner that reflects the market interest rate for a similar nonconvertible instrument at the date of issuance. The initial carrying value of the liability component of $368.3 million was calculated using a 7.5% assumed borrowing rate. The equity component of $149.2 million, representing the conversion option, was determined by deducting the fair value of the liability component from the par value of the 2024 Notes and is recorded in additional paid-in capital on the consolidated balance sheet at the issuance date. That equity component is treated as a discount on the liability component of the 2024 Notes, which is amortized over the 7-year term of the 2024 Notes using the effective interest rate method. The equity component is not re-measured as long as it continues to meet the conditions for equity classification. The Company allocated the total transaction costs of approximately $14.7 million related to the issuance of the 2024 Notes to the liability and equity components of the 2024 Notes based on their relative values. Transaction costs attributable to the liability component are amortized to interest expense over the seven-year term of the 2024 Notes, and transaction costs attributable to the equity component are netted with the equity component in stockholders’ equity. The 2024 Notes do not contain any financial or operating covenants or any restrictions on the payment of dividends, the issuance of other indebtedness or the issuance or repurchase of securities by the Company. The 2024 Indenture contains customary events of default with respect to the 2024 Notes, including that upon certain events of default, 100% of the principal and accrued and unpaid interest on the 2024 Notes will automatically become due and payable. Convertible senior notes, net of discounts and deferred financing costs consisted of the following: December 31, (in thousands) 2018 2017 Principal $ 517,500 $ 517,500 Deferred financing costs (8,326 ) (9,652 ) Debt discount, net (120,678 ) (138,230 ) Net carrying amount $ 388,496 $ 369,618

OTHER BALANCE SHEET DETAILS

OTHER BALANCE SHEET DETAILS	12 Months Ended
	Dec. 31, 2018
Other Balance Sheet Details [Abstract]
OTHER BALANCE SHEET DETAILS	NOTE 6. OTHER BALANCE SHEET DETAILS Inventory consisted of the following: December 31, (in thousands) 2018 2017 Raw materials $ 7,855 $ — Work in process 2,208 491 Finished goods 801 533 Total inventory $ 10,864 $ 1,024 Property and equipment, net, consisted of the following: December 31, (in thousands) 2018 2017 Tenant improvements $ 19,857 $ 2,019 Furniture and fixtures 2,968 1,303 Scientific equipment 28,163 26,248 Computer equipment 11,152 8,821 62,140 38,391 Less accumulated depreciation (28,271 ) (27,580 ) Property and equipment, net $ 33,869 $ 10,811 Accounts payable and accrued liabilities consisted of the following: December 31, (in thousands) 2018 2017 Accrued employee related costs $ 27,341 $ 24,901 Accounts payable 13,801 5,648 Accrued development costs 7,069 4,799 Other accrued liabilities 38,166 18,172 Total accounts payable and accrued liabilities $ 86,377 $ 53,520

NET INCOME (LOSS) PER SHARE

NET INCOME (LOSS) PER SHARE	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
NET INCOME (LOSS) PER SHARE	NOTE 7. NET INCOME (LOSS) PER SHARE Net income (loss) per share was calculated as follows: Year Ended December 31, (in thousands, except per share data) 2018 2017 2016 Net income (loss) - basic and diluted $ 21,111 $ (142,542 ) $ (141,090 ) Weighted-average common shares outstanding: Basic 90,235 88,089 86,713 Effect of dilutive securities: Employee stock purchase program 11 — — Stock options 3,228 — — Restricted stock units 564 — — 2024 Notes 1,348 — — Diluted 95,386 88,089 86,713 Net income (loss) per share: Basic $ 0.23 $ (1.62 ) $ (1.63 ) Diluted $ 0.22 $ (1.62 ) $ (1.63 ) Shares which have been excluded from diluted per share amounts because their effect would have been anti-dilutive include the following: Year Ended December 31, (in thousands) 2018 2017 2016 Stock options and restricted stock units 887 7,436 6,995

SHARE-BASED COMPENSATION

SHARE-BASED COMPENSATION	12 Months Ended
	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
SHARE-BASED COMPENSATION	NOTE 8. SHARE-BASED COMPENSATION Share-Based Compensation Plans. In May 2011, the Company adopted the Neurocrine Biosciences, Inc. 2011 Equity Incentive Plan (the 2011 Plan) pursuant to which 19 million shares of Company’s common stock are authorized for issuance. The 2011 Plan provides for the grant of stock options that qualify as incentive stock options under Section 422 of the Internal Revenue Code of 1986, as amended (the Code), nonstatutory stock options, restricted stock awards, restricted stock unit awards (RSUs), stock appreciation rights, performance stock awards, performance-based restricted stock units (PRSUs) and other forms of equity compensation. In May 2018, the Company adopted the Neurocrine Biosciences, Inc. ESPP pursuant to which 300,000 shares of the Company’s common stock are authorized for issuance. No purchases have occurred under the ESPP during the year ended December 31, 2018. The Company also issues stock options and RSUs under the Neurocrine Biosciences, Inc. Inducement Plan (Inducement Plan) to certain employees. The Company granted 70,000 stock options and 20,000 RSUs pursuant to the Inducement Plan in 2018 and granted 410,000 stock options and 12,500 RSUs pursuant to the Inducement Plan in 2017. The Company did not grant any stock options or RSUs pursuant to the Inducement Plan during 2016. These stock option grants have a 4-year vesting period and the RSUs generally have vesting periods of 3 to 4 years. The Company currently has 245,162 in stock options and RSUs outstanding under this Inducement Plan. As of December 31, 2018, approximately 6.8 million shares of common stock remained available for the future grant of awards under the 2011 Plan. Only share awards made under the 2011 Plan that are subsequently cancelled due to forfeiture or expiration are returned to the share pool available for future grants. The Company issues new shares upon the exercise of stock options, the issuance of stock bonus awards, and the vesting of RSUs and PRSUs, and has 7.2 million shares of common stock reserved for such issuances as of December 31, 2018. Vesting Provisions of Share-Based Compensation. Stock options generally have terms from 7 to 10 years from the date of grant, and generally vest over a 3 to 4-year period. The maximum contractual term for all options granted from the 2011 Plan is 10 years. RSUs granted under the 2011 Plan generally have vesting periods of 4 years. PRSUs granted under the 2011 Plan vest based on the achievement of certain pre-defined Company-specific performance criteria and expire 4 to 5 years from the grant date. Share-Based Compensation. The compensation cost that has been included in the statement of comprehensive income (loss) for all share-based compensation arrangements is as follows: Year Ended December 31, (in thousands) 2018 2017 2016 Sales, general and administrative expense $ 31,847 $ 27,951 $ 16,770 Research and development expense 26,221 14,571 11,694 Share-based compensation expense $ 58,068 $ 42,522 $ 28,464 Stock Options. The exercise price of all stock options granted during the years ended December 31, 2018, 2017 and 2016 was equal to the closing price of the Company’s common stock on the date of grant. The estimated fair value of each stock option award granted was determined on the date of grant using the Black-Scholes option-pricing valuation model with the following weighted-average assumptions for option grants during the three years ended December 31, 2018: Year Ended December 31, (in thousands) 2018 2017 2016 Risk-free interest rate 2.5 % 2.0 % 1.4 % Expected volatility of common stock 59.5 % 58.0 % 60.0 % Dividend yield 0.0 % 0.0 % 0.0 % Expected option term 4.7 years 5.7 years 5.6 years The Company estimates the fair value of stock options using a Black-Scholes option-pricing model on the date of grant. The fair values of equity instruments are recognized and amortized on a straight-line basis over the requisite service period. The Black-Scholes option-pricing model incorporates various and highly sensitive assumptions including expected volatility, term, and interest rates. The expected volatility is based on the historical volatility of the Company’s common stock over the most recent period commensurate with the estimated expected term of the Company’s stock options. The expected option term is estimated based on historical experience as well as the status of the employee. For example, directors and officers have a longer expected option term than all other employees. The risk-free rate for periods within the contractual life of the option is based upon observed interest rates appropriate for the expected term of the Company’s employee stock options. The Company has never declared or paid dividends and has no plans to do so in the foreseeable future. The Company’s determination of fair value is affected by its stock price as well as a number of assumptions that require judgment. The weighted-average fair values of stock options granted during the years ended December 31, 2018, 2017 and 2016, estimated as of the grant date using the Black-Scholes option-pricing model, were $43.42, $25.11 and $21.49, respectively. A summary of the status of the Company’s stock options as of December 31, 2018, 2017 and 2016 and of changes in options outstanding under the plans during the three years ended December 31, 2018 is as follows: 2018 2017 2016 (in thousands, except weighted average data) Options Weighted Average Exercise Price Options Weighted Average Exercise Price Options Weighted Average Exercise Price Outstanding at January 1 6,356 $ 28.83 6,112 $ 20.01 5,507 $ 15.63 Granted 1,040 84.97 1,807 46.55 1,077 40.19 Exercised (1,592 ) 18.95 (1,353 ) 10.41 (341 ) 7.60 Canceled (58 ) 64.67 (210 ) 43.05 (131 ) 34.35 Outstanding at December 31 5,746 $ 41.38 6,356 $ 28.83 6,112 $ 20.01 Stock options outstanding at December 31, 2018 had a weighted average remaining contractual term of 6.7 years. For the year ended December 31, 2018, 2017 and 2016 share-based compensation expense related to stock options was $35.4 million, $28.2 million, and $18.4 million, respectively. As of December 31, 2018, there was Restricted Stock Units. The fair value of RSUs is based on the closing sale price of the Company’s common stock on the date of issuance. For the year ended December 31, 2018, 2017, and 2016, share-based compensation expense related to RSUs was $21.9 million, $13.9 million, and $8.3 million, respectively. As of December 31, 2018, there was approximately $51.6 million of unamortized compensation cost related to RSUs, which is expected to be recognized over a weighted average remaining vesting period of approximately 2.3 years. The total intrinsic value of RSUs converted into common shares during the years ended December 31, 2018, 2017, and 2016 was $35.5 million, $14.9 million, and $12.2 million, respectively. The RSUs, at the election of eligible employees, may be subject to deferred delivery arrangement. The total intrinsic value of RSUs outstanding at December 31, 2018 was $80.9 million based on the Company’s closing stock price on that date. A summary of the status of the Company’s RSUs as of December 31, 2018, 2017, and 2016 and of changes in RSUs outstanding under the plans for the three years ended December 31, 2018 is as follows: 2018 2017 2016 (in thousands, except weighted average data) Number of Units Weighted Average Grant Date Fair Value per Unit Number of Units Weighted Average Grant Date Fair Value per Unit Number of Units Weighted Average Grant Date Fair Value per Unit Outstanding at January 1 1,080 $ 40.30 883 $ 29.33 910 $ 24.23 Granted 540 85.29 588 47.21 326 36.73 Cancelled (58 ) 36.21 (41 ) 40.62 (69 ) 32.50 Converted into common shares (429 ) 59.23 (350 ) 24.19 (284 ) 20.71 Outstanding at December 31 1,133 $ 62.31 1,080 $ 40.30 883 $ 29.33 Performance-Based Restricted Stock Units. During each of the years ended December 31, 2018 and 2016, the Company granted approximately 0.2 million PRSUs that vest based on the achievement of certain pre-defined Company-specific performance criteria and expire approximately 4 to 5 years from the grant date. No PRSUs were granted during the year ended December 31, 2017. Additionally, 0.2 million PRSUs were earned during the year ended December 31, 2017. The fair value of PRSUs is estimated based on the closing sale price of the Company’s common stock on the date of grant. Expense recognition for PRSUs commences when attainment of the performance-based criteria is determined to be probable. During 2018, the Company recognized no expense related to PRSUs. During 2017 and 2016, the Company recognized approximately $0.4 million and $1.8 million, respectively, in expense related to PRSUs. At December 31, 2018, the total unrecognized estimated compensation expense related to PRSUs was $19.7 million and the total intrinsic value of PRSUs outstanding was $23.6 million based on the Company’s closing stock price on that date. The total intrinsic value of PRSUs converted into common shares was $8.8 million during the year ended December 31, 2017. No PRSUs were earned during the years ended December 31, 2018 or 2016. Employee Stock Purchase Plan. Under the ESPP, eligible employees may purchase shares of the Company’s common stock at a discount semi-annually based on a percentage of their annual compensation. The ESPP provides for the granting of up to 300,000 shares of the Company’s common stock to eligible employees. The discounted purchase price is equal to the lower of 85% of (i) the market value per share of the common stock on the first day of the offering period or (ii) the market value per share of common stock on the purchase date. Share-based compensation expense recognized under the ESPP was $0.8 million for the year ended December 31, 2018.

INCOME TAXES

INCOME TAXES	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
INCOME TAXES	NOTE 9. INCOME TAXES The components of the income tax expense for continuing operations are as follows: (in thousands) 2018 2017 2016 Current: Federal $ (100 ) $ — $ — State 830 — — Total income tax expense $ 730 $ — $ — The provision for income taxes on earnings subject to income taxes differs from the statutory federal rate at December 31, 2018, 2017 and 2016, due to the following: (in thousands) 2018 2017 2016 Federal income taxes at 21% for 2018 and 35% for 2017 and 2016 $ 4,587 $ (49,889 ) $ (49,383 ) State income tax, net of federal benefit 361 (4,013 ) 2 Tax effect on non-deductible expenses 446 433 (321 ) Share-based compensation expense (9,778 ) (19,589 ) (5,077 ) Officer compensation 915 2,163 — Change in tax rate (198 ) 154,415 — Expired tax attributes 13,874 2,998 6,708 Research credits (13,526 ) (5,596 ) (5,554 ) Change in valuation allowance 4,306 (79,966 ) 53,414 Other (257 ) (956 ) 211 $ 730 $ — $ — Significant components of the Company’s deferred tax assets and liabilities as of December 31, 2018 and 2017 are listed below. A valuation allowance of $335.2 million and $330.9 million at December 31, 2018 and 2017, respectively, has been recognized to offset net deferred tax assets as realization of such assets is uncertain. Amounts are shown as of December 31 as of each respective year: (in thousands) 2018 2017 Deferred tax assets: Net operating losses $ 223,800 $ 238,500 R&D credits 62,200 47,500 Capitalized R&D 34,800 47,500 Share-based compensation 17,300 14,600 Other 28,600 14,600 Total deferred tax assets 366,700 362,700 Deferred tax liabilities: Convertible senior notes (26,400 ) (31,300 ) Fixed assets (5,100 ) (500 ) Total deferred tax liabilities (31,500 ) (31,800 ) Net of deferred tax assets and liabilities 335,200 330,900 Valuation allowance (335,200 ) (330,900 ) Net deferred tax assets $ — $ — At December 31, 2018, the Company had federal and state income tax net operating loss carry forwards of approximately $1.0 billion and $398.0 million, respectively. The federal net operating losses will begin to expire in 2021, unless previously utilized. A portion of the California net operating loss carry forwards expired in 2018. The remaining California net operating losses will begin to expire in 2028 and the net operating losses related to other states will begin to expire in 2026. In addition, the Company has federal and California R&D tax credit carry forwards of $63.6 million and $41.6 million, respectively. A portion of the federal R&D tax credit carry forwards expired in 2018. The remaining federal R&D tax credits will continue to expire beginning in 2019, unless previously utilized. The California R&D tax credits carry forward indefinitely. Additionally, the future utilization of the Company’s net operating loss and R&D tax credit carry forwards to offset future taxable income may be subject to annual limitations, pursuant to Internal Revenue Code Sections 382 and 383, as a result of ownership changes that could result in the future. The Company has determined that no ownership changes have occurred through December 31, 2018. On December 22, 2017, the Tax Cuts and Jobs Act (TCJA) was enacted, reducing the corporate income tax rate from 35% to 21% effective on January 1, 2018. The carrying value of the Company's deferred tax assets is also determined by the enacted U.S. corporate income tax rate. Consequently, any changes in the U.S. corporate income tax rate have impacted the carrying value of the Company’s deferred tax assets. Under the new corporate income tax rate of 21%, deferred income taxes decreased, with a corresponding decrease to the valuation allowance. Therefore, the TCJA had no impact on the Company's 2017 earnings. As of December 31, 2018, the Company has completed its accounting of the tax effects from the enactment of the TCJA. Under the FASB's accounting guidance related to uncertain tax positions, among other things, the impact of an uncertain income tax position on the income tax return must be recognized at the largest amount that is more-likely-than-not to be sustained upon audit by the relevant taxing authority. An uncertain income tax position will not be recognized if it has less than a 50% likelihood of being sustained. Additionally, the FASB provides accounting guidance on derecognition, classification, interest and penalties, accounting in interim periods, disclosure, and transition. The Company’s policy is to recognize interest or penalties related to income tax matters in income tax expense. Interest and penalties related to income tax matters were not material for the years ended December 31, 2018 or 2017. The Company is subject to taxation in the U.S. and various state jurisdictions. The Company’s tax years for 2001 (federal) and 2008 (California) and forward are subject to examination by the U.S. and state tax authorities due to the carry forward of unutilized net operating losses and R&D tax credits. The following table summarizes the activity related to unrecognized tax benefits: (in thousands) 2018 2017 2016 Balance as of the beginning of the year $ 37,403 $ 34,112 $ 33,074 Increases related to prior year tax positions 6,103 — 260 Increases related to current year tax positions 11,726 3,291 2,211 Expiration of the statute of limitations for the assessment of taxes (457 ) — (1,433 ) Balance as of the end of the year $ 54,775 $ 37,403 $ 34,112 The Company, under authoritative guidance, excluded those deferred tax assets that are not more-likely-than-not to be sustained under the technical merits of the tax position. These unrecognized tax benefits totaled $11.7 million for current year tax positions, as reflected in the table above. As of December 31, 2018, the Company had $50.1 million of unrecognized tax benefits that, if recognized and realized, would affect the effective tax rate. In the next 12 months, the Company does not expect a significant change in its unrecognized tax benefits.

LEASES

LEASES	12 Months Ended
	Dec. 31, 2018
Leases [Abstract]
LEASES	NOTE 10. LEASES In December 2007, the Company closed the sale of its facility and associated real property for a purchase price of $109 million. Concurrent with the sale, the Company 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 Company recognized $0.7 million in 2018, $2.1 million in 2017, and $3.4 million in 2016. As of December 31, 2018, the remaining balance of the net deferred gain was approximately $7.3 million, which the Company expects to recognize as a cumulative-effect adjustment to equity upon adoption of Topic 842 on January 1, 2019. Refer to Note 1 to the consolidated financial statements for more information on the impact of adoption. Upon the closing of the sale of the facility and associated real property, the Company entered into an agreement (original lease) whereby it leased back the Company’s corporate headquarters, comprised of two buildings located in San Diego, California, for an initial term of 12 years. In 2008 through 2011, the Company entered into a series of subsequent amendments to the original lease, whereby the Company vacated a building and continued to occupy one building. In June 2017, the Company entered into an amendment to extend the current term of the original lease through December 31, 2029. Under the terms of the amendment, the Company reduced the base rental rate by approximately 8% and will continue to pay base annual rent (subject to an annual fixed percentage increase), plus a 3.5% annual management fee, property taxes, and other normal and necessary expenses, such as utilities, repairs, and maintenance. Certain incentives were included in the lease, including approximately $13.1 million in tenant improvement allowances, three months of rent abatement, and a reduction in the required security deposit amount from $4.7 million to $3.0 million. In lieu of a cash security deposit, Wells Fargo Bank, N.A. issued on the Company’s behalf a $3.0 million letter of credit, which is secured by a deposit of equal amount with the same bank. The Company has the right to extend the lease for 2 consecutive 10-year terms and right of first offer for future rental of adjacent office space owned by the landlord. In May 2018, the Company entered into an agreement to lease 44,718 square feet of office space, which commenced on July 1, 2018, for a term of 10 years and 10 months. Under the terms of the lease, the Company 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 approximately $4.2 million in tenant improvement allowances and twelve months of rent abatement. In lieu of a cash security deposit, Wells Fargo Bank, N.A. issued on the Company’s behalf a $1.0 million letter of credit, which is secured by a deposit of equal amount with the same bank. The Company does not have the right to extend the lease or right of first offer for future rental of adjacent office space owned by the landlord. The Company recognizes rent expense on a straight-line basis over the term of the associated lease. Accordingly, rent expense recognized in excess of rent paid is reflected as a liability in the Company’s consolidated balance sheets. Gross rent expense was approximately $6.9 million for 2018, $5.9 million for 2017, and $6.0 million for 2016.

RETIREMENT PLAN

RETIREMENT PLAN	12 Months Ended
	Dec. 31, 2018
Compensation And Retirement Disclosure [Abstract]
RETIREMENT PLAN	NOTE 11. RETIREMENT PLAN The Company has a 401(k) defined contribution savings plan (401(k) Plan). The 401(k) Plan is for the benefit of all qualifying employees and permits voluntary contributions by employees up to 60% of base salary limited by the IRS-imposed maximum. Employer contributions were $1.8 million, $1.1 million, and $0.6 million for the years ended December 31, 2018, 2017 and 2016, respectively.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	NOTE 12. COMMITMENTS AND CONTINGENCIES Product Liability. The Company’s business exposes it to liability risks from its potential drug products. A successful product liability claim or series of claims brought against the Company could result in payment of significant amounts of money and divert management’s attention from running the business. The Company may not be able to maintain insurance on acceptable terms, or the insurance may not provide adequate protection in the case of a product liability claim. To the extent that product liability insurance, if available, does not cover potential claims, the Company would be required to self-insure the risks associated with such claims. The Company believes that it carries reasonably adequate insurance for product liability claims. Licensing and Research Agreements. The Company entered into in-licensing agreements with various universities and research organizations, which are generally cancelable at the option of the Company with terms ranging from 0-180 days written notice. Under the terms of these agreements, the Company received licenses to research tools, know-how, and technology claimed in certain patents or patent applications. The Company is required to pay fees, milestones, and/or royalties on future sales of products employing the technology or falling under claims of a patent, and some of the agreements require minimum royalty payments. Some of the agreements also require the Company to pay expenses arising from the prosecution and maintenance of the patents covering the in-licensed technology. The Company continually reassesses the value of the license agreements and cancels them when research efforts are discontinued on these programs. As of December 31, 2018, the Company may be required to pay milestone payments of up to $1.0 billion over the lives of these agreements, in addition to royalties on sales of the affected products at rates ranging up to 6%. Due to the uncertainties of the development process, the timing and probability of the milestone and royalty payments cannot be accurately estimated. The Company is not aware of any proceedings or claims that it believes will have, individually or in the aggregate, a material adverse effect on its business, financial condition or results of operations.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	NOTE 13. SUBSEQUENT EVENTS On January 28, 2019, the Company entered into a collaboration and license agreement with a clinical-stage gene therapy company, Voyager Therapeutics, Inc., or Voyager. The collaboration is focused on the development and commercialization of four programs using Voyager’s proprietary gene therapy platforms. The four programs consist of Voyager’s VY-AADC program for Parkinson’s disease, Voyager’s VY-FXN01 program for Friedreich’s ataxia, as well as rights to two programs to be determined by the parties in the future. In connection with the agreement, the Company agreed to pay Voyager a $115 million upfront cash payment and entered into an agreement to purchase $50 million of Voyager’s common stock. Pursuant to development plans agreed to by the Company and Voyager, unless Voyager exercises the co-development and co-commercialization rights that are described below, the Company has agreed to be responsible for all development costs. Upon the occurrence of a specified event for each program, the Company has agreed to assume responsibility for development, manufacturing, and commercialization activities for such program. Additionally, Voyager may be entitled to earn up to $1.7 billion in development, regulatory, and commercial milestones across the four programs and royalties for net sales in and outside the U.S. Under the terms of the agreement, on a program-by-program basis, upon the achievement of milestones or metrics specified in the agreement for VY-AADC and VY-FXN01, Voyager will have the option to co-develop and co-commercialize such program with the Company in the U.S. under cost- and profit-sharing arrangements, and Voyager agrees to forfeit certain milestones and royalties related to such program for which Voyager has exercised its co-develop and co-commercialize option. The effectiveness of the agreement and the closing of the sale and issuance of the Voyager common stock described above are subject to certain conditions, including the expiration or termination of the applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, and other customary closing conditions.

SELECTED QUARTERLY FINANCIAL DA

SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED)	NOTE 14. SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) The following is a summary of the quarterly results of the Company for the years ended December 31, 2018 and 2017: (in thousands, except per share data) First Quarter Second Quarter Third Quarter Fourth Quarter 2018: Revenues $ 71,086 $ 96,905 $ 151,757 $ 131,492 Operating expenses $ 108,533 $ 98,757 $ 97,434 $ 109,621 Net (loss) income $ (41,818 ) $ (5,913 ) $ 50,764 $ 18,078 Net (loss) income per share: Basic $ (0.47 ) $ (0.07 ) $ 0.56 $ 0.20 Diluted $ (0.47 ) $ (0.07 ) $ 0.52 $ 0.19 Shares used in the calculation of net (loss) income per share: Basic 89,526 90,100 90,555 90,742 Diluted 89,526 90,100 96,798 95,724 2017: Revenues $ — $ 6,335 $ 60,774 $ 94,517 Operating expenses $ 79,932 $ 63,603 $ 66,769 $ 82,683 Net (loss) income $ (78,326 ) $ (59,985 ) $ (11,125 ) $ 6,894 Net (loss) income per share: Basic $ (0.90 ) $ (0.68 ) $ (0.13 ) $ 0.08 Diluted $ (0.90 ) $ (0.68 ) $ (0.13 ) $ 0.07 Shares used in the calculation of net (loss) income per share: Basic 87,283 88,063 88,325 88,665 Diluted 87,283 88,063 88,325 92,659

ORGANIZATION AND SUMMARY OF S_2

ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Business Activities	Business Activities. Neurocrine Biosciences, Inc. (the Company or Neurocrine) was incorporated in California in 1992 and reincorporated in Delaware in 1996. Neurocrine Continental, Inc., is a Delaware corporation and a wholly owned subsidiary of the Company. The Company also has two wholly-owned Irish subsidiaries, Neurocrine Therapeutics, Ltd. and Neurocrine Europe, Ltd. both of which were formed in December 2014 and are inactive. The Company discovers, develops, and commercializes innovative and life-changing pharmaceuticals, in diseases with high unmet medical needs, through its novel research and development (R&D) platform, focused on neurological and endocrine related diseases and disorders. The Company discovered, developed, and markets INGREZZA ® ®
Principles of Consolidation	Principles of Consolidation. The consolidated financial statements include the accounts of Neurocrine as well as its wholly owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation.
Use of Estimates	Use of Estimates. The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (GAAP) requires management to make estimates and assumptions that affect the amounts reported in the financial statements and the accompanying notes. Actual results could differ from those estimates.
Industry Segment and Geographic Information	Industry Segment and Geographic Information. The Company operates in a single industry segment – the discovery, development, and marketing of pharmaceuticals for the treatment of neurological and endocrine based diseases and disorders. The Company had no foreign based operations during any of the years presented.
Cash Equivalents	Cash Equivalents. The Company considers all highly liquid investments that are readily convertible into cash and have an original maturity of three months or less at the time of purchase to be cash equivalents .
Short-Term and Long-Term Investments Available-for-Sale	Short-Term and Long-Term Investments Available-for-Sale. Certain investments are classified as available-for-sale and carried at fair value, with any unrealized gains and losses reported in other comprehensive loss. The amortized cost of investments in debt securities is adjusted for the amortization of premiums and accretion of discounts to maturity, which are included in investment income and other, net. The cost of investments in debt securities sold is based on the specific identification method. Realized gains and losses, interest and dividends, 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.
Accounts Receivable	Accounts Receivable. Accounts receivable are recorded net of customer allowances for prompt payment discounts, chargebacks, and any allowance for doubtful accounts. The Company estimates the allowance for doubtful accounts based on existing contractual payment terms, actual payment patterns of its customers, and individual customer circumstances. To date, an allowance for doubtful accounts has not been required.
Fair Value of Financial Instruments	Fair Value of Financial Instruments. Certain financial instruments, including cash, cash equivalents, accounts receivable, accounts payable, and accrued liabilities are carried at cost, which the Company believes approximates fair value because of the short-term nature of these instruments. 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 is estimated utilizing market quotations from an over-the-counter trading market and approximated 119% and 128% of the face value of the 2024 Notes at December 31, 2018 and 2017, respectively.
Inventory	Inventory. Inventory is stated at the lower of cost or estimated net realizable value. The Company currently uses actual costing to determine the cost basis for its inventory. Inventory is valued on a first-in, first-out basis and consists primarily of third-party manufacturing costs. The Company capitalizes inventory costs associated with its products upon regulatory approval when, based on management’s judgment, future commercialization is considered probable and the future economic benefit is expected to be realized; otherwise, such costs are expensed. Prior to FDA approval of INGREZZA, all costs related to its manufacture were included in R&D expense in the period incurred. Historically, the Company’s physical inventory included active pharmaceutical ingredients produced prior to FDA approval of INGREZZA and accordingly had no cost basis as the cost associated with producing this material was expensed in the period incurred. Costs associated with the manufacture of bulk drug product, finished bottling, and other labeling activities that occurred post FDA approval of INGREZZA are included in the inventory value. The Company reduces its inventory to net realizable value for potential excess, dated, or obsolete inventory based on an analysis of forecasted demand compared to quantities on hand and any firm purchase orders, as well as product shelf life. To date, such reserves have not been significant.
Property and Equipment	Property and Equipment. Property and equipment are stated at cost and depreciated over the estimated useful lives of the assets using the straight-line method. Equipment is depreciated over an average estimated useful life of 3 to 7 years. Leasehold improvements are depreciated over the shorter of their estimated useful lives or the remaining lease term. Depreciation expense was $4.0 million for 2018, $2.4 million for 2017, and $1.5 million for 2016.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets. The Company reviews long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable. If indicators of impairment exist, the Company assesses the recoverability of the affected long-lived assets by determining whether the carrying value of such assets can be recovered through undiscounted future operating cash flows. If the carrying amount is not recoverable, the Company measures the amount of any impairment by comparing the carrying value of the asset to the present value of the expected future cash flows associated with the use of the asset.
Revenue Recognition	Revenue Recognition. The Company recognizes revenue when the customer obtains control of the product in an amount that reflects the consideration the Company expects to receive from the customer in exchange for that product. To determine revenue recognition, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the Company satisfies the performance obligation. The Company only applies the five-step model to contracts when it is probable that the Company will collect the consideration it is entitled to in exchange for the good transferred to the customer. Once a contract is determined to be within the scope of Accounting Standards Codification 606, Revenue from Contracts with Customers (Topic 606), at contract inception, the Company assesses the goods promised within the contract to determine those that are performance obligations and assesses whether each promised good is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. Product Sales, Net. The Company’s product sales consist of sales of INGREZZA in the U.S. INGREZZA was approved by the FDA on April 11, 2017 and the Company commenced shipments of INGREZZA to specialty pharmacies (SPs) and a specialty distributor (SD) (collectively, customers) in April 2017. The SPs dispense product to a patient based on the fulfillment of a prescription and the SD sells product to closed-door pharmacies and government facilities. The Company’s agreements with the customers provide for transfer of title to the product at the time the product is delivered to the customers. In addition, except for limited circumstances, the customers have no right of product return. Product sales are recognized when the customers obtain control of the Company’s product, typically upon delivery to the customers. Revenue from product sales are recorded at the net sales price (transaction price), which includes an estimate of variable consideration for which reserves are established and which results from contractual discounts, returns, chargebacks, rebates, co-pay assistance, and other allowances relating to sales of the Company’s products. These reserves are based on the amounts earned or to be claimed on the related sales and are classified as reductions of accounts receivable (if the amounts are payable to the customers) or a current liability (if the amounts are payable to parties other than the customers). Where appropriate, these estimates take into consideration a range of possible outcomes that are probability-weighted for relevant factors such as the Company’s historical experience, current contractual and statutory requirements, specific known market events and trends, industry data, and forecasted customer buying and payment patterns. Overall, these reserves reflect the Company’s best estimates of the amount of consideration to which it is entitled based on the terms of the contract. The amount of variable consideration that is included in the transaction price may be constrained and is included in the net sales price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. Actual amounts of consideration ultimately received may differ from the Company’s estimates. If actual results in the future vary from the Company’s estimates, the Company will adjust these estimates, which would affect net product revenue and earnings in the period such variances become known. Shipping and handling costs related to the Company’s product sales are included in sales, general and administrative expenses. Collaborative and Other Revenue. The Company enters into collaboration and licensing agreements under which it licenses certain rights to its product candidates to third parties. The terms of these arrangements typically include payment to the Company of one or more of the following: non-refundable, up-front license fees; development, regulatory, and commercial milestone payments; payments for manufacturing supply services; and royalties on net sales of licensed products. As part of the accounting for these arrangements, the Company develops assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company uses key assumptions to determine the stand-alone selling price, which may include forecasted revenues, development timelines, reimbursement rates for personnel costs, discount rates, and probabilities of technical and regulatory success. Royalty Revenue : For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). Sales-based royalties for ORILISSA are calculated as a percentage of AbbVie net sales as defined in the Company’s agreement with AbbVie. Each quarterly period, sales-based royalties are recorded based on estimated quarterly net sales of ORILISSA. Differences between actual results and estimated amounts are adjusted for in the period in which they become known, which typically follows the quarterly period in which the estimate was made. Licenses of Intellectual Property : If the license to the Company’s intellectual property embedded within a collaboration and/or licensing arrangement is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from non-refundable, up-front fees allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The Company receives payments from its licensees based on billing schedules established in each agreement. Up-front payments and fees are recorded as deferred revenue upon receipt, or when due, and may require deferral of revenue recognition to a future period until the Company performs its obligations under these arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional. Milestone Payments : At the inception of each arrangement that includes development, commercialization, and regulatory milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. Performance milestone payments represent a form of variable consideration. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the Company’s control or that of the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The transaction price is then allocated to each performance obligation on a relative stand-alone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such development milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect milestone and license fees revenues and earnings in the period of adjustment. Manufacturing Supply Services : Arrangements that include a promise for future supply of drug substance or drug product for either clinical development or commercial supply at the licensee’s discretion are generally considered as options. The Company assesses if these options provide a material right to the licensee and if so, they are accounted for as separate performance obligations.
Concentration of Credit Risk	Concentration of Credit Risk. The Company does not currently have any of its own manufacturing facilities, and therefore it depends on an outsourced manufacturing strategy for the production of INGREZZA for commercial use and for the production of its product candidates for clinical trials. The Company has contracts in place with one third-party manufacturer that is approved for the commercial production of INGREZZA’s capsules at 2 separate sites and one third-party manufacturer that is approved for the production of INGREZZA’s active pharmaceutical ingredient. Although there are potential sources of supply other than the Company’s existing suppliers, any new supplier would be required to qualify under applicable regulatory requirements. The Company has entered into distribution agreements with a limited number of SPs and SDs, and all of the Company’s product sales are to these customers. The Company’s 3 largest customers represented 93% of the Company’s product revenue for the year ended December 31, 2018 and 2017 and substantially all of the Company’s accounts receivable balance at December 31, 2018 and 2017. Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash, cash equivalents, investments, and accounts receivables. The Company established guidelines to limit its exposure to credit risk by placing investments with high credit quality financial institutions, diversifying its investment portfolio and placing investments with maturities that maintain safety and liquidity.
Cost of Sales	Cost of Sales. Cost of sales includes third-party manufacturing, transportation, freight, and indirect overhead costs associated with the manufacture and distribution of INGREZZA, sales-based license costs on AbbVie net sales of ORILISSA, as defined in the Company’s agreement with AbbVie, and period costs resulting from certain inventory manufacturing services and variances and adjustment charges. A portion of the costs associated with the manufacture of INGREZZA sold to date was expensed as R&D prior to the FDA’s approval of INGREZZA and is therefore excluded from cost of sales during this period.
Research and Development Expenses	Research and Development Expenses. R&D expenses consist primarily of salaries, payroll taxes, employee benefits, and share-based compensation charges for those individuals involved in ongoing research and development efforts; as well as scientific consulting fees, preclinical and clinical trial costs, R&D facilities costs, laboratory supply costs, and depreciation of scientific equipment. All such costs are charged to R&D expense as incurred. These expenses result from the Company’s independent R&D efforts, as well as efforts associated with collaborations, in-licenses, and third-party funded research arrangements.
Advertising Expense	Advertising Expense. In connection with the FDA approval and commercial launch of INGREZZA in April 2017, the Company began to incur advertising costs, which are expensed when services are performed, or goods are delivered. The Company incurred advertising costs related to its marketed product, INGREZZA, of $20.5 million in 2018 and $10.1 million in 2017.
Share-Based Compensation	Share-Based Compensation. The Company grants stock options to purchase its common stock to eligible employees and directors and also grants certain employees restricted stock units (RSUs) and performance-based restricted stock units (PRSUs). Additionally, the Company allows employees to participate in an employee stock purchase plan (ESPP). The Company estimates the fair value of stock options and shares to be issued under the ESPP using the Black-Scholes option-pricing model on the date of grant. Restricted stock units are valued based on the closing price of the Company’s common stock on the date of grant. The fair value of equity instruments expected to vest are recognized and amortized on a straight-line basis over the requisite service period of the award, which is generally 3 to 4 years; however, certain provisions in the Company’s equity compensation plans provide for shorter vesting periods under certain circumstances. The fair value of shares to be issued under the ESPP are recognized and amortized on a straight-line basis over the purchase period, which is generally 6 months. Additionally, the Company granted certain PRSUs that vest upon the achievement of certain pre-defined company-specific performance-based criteria. Expense related to these PRSUs is generally recognized ratably over the expected performance period once the pre-defined performance-based criteria for vesting becomes probable.
Net Income (Loss) Per Share	Net Income (Loss) Per Share. Basic net income (loss) per share is computed using the weighted average number of common shares outstanding during the period. Diluted net income per share is computed using the weighted average number of common and potentially dilutive shares outstanding during the period, including the potentially dilutive shares resulting from the conversion of the 2024 Notes, and excluding the effect of stock options and restricted stock outstanding for periods when their effect is anti-dilutive, using the treasury stock method. Convertible debt instruments that may be settled entirely or partly in cash (such as the 2024 Notes) may, in certain circumstances where the borrower has the ability and intent to settle in cash, be accounted for under the treasury stock method. The Company issued the 2024 Notes with a combination settlement feature, which the Company has the ability and intent to use upon conversion of the notes, to settle the principal amount of debt for cash and the excess of the principal portion in shares of its common stock. As a result, of the approximately 6.8 million shares underlying the 2024 Notes, only the shares required to settle the excess of the principal portion would be considered dilutive under the treasury stock method. Further, approximately 0.3 million PRSUs have been excluded from the calculation of diluted net income per share as the performance condition has not been achieved. In loss periods, basic net loss per share and diluted net loss per share are identical because the otherwise dilutive potential common shares become anti-dilutive and are therefore excluded.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements. In May 2014, the Financial Accounting Standards Board (FASB) issued Account Standards Update (ASU) No. 2014-09, “Revenue from Contracts with Customers (Topic 606)”, which supersedes all existing revenue recognition requirements, including most industry-specific guidance. This new standard amends the guidance for the recognition of revenue from contracts with customers to transfer goods and services. The FASB subsequently issued additional, clarifying standards to address issues arising from implementation of the new revenue recognition standard. The Company adopted this standard on January 1, 2018, using the modified retrospective method, and applied the standard only to contracts that were not completed prior to January 1, 2018. The adoption of the new revenue standard did not change the Company’s revenue recognition. As the Company did not identify any accounting changes that impacted the amount of reported revenues with respect to product revenues, or revenue from collaboration and license agreements, no adjustment to retained earnings was required upon adoption. In November 2016, the FASB issued ASU 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash”, which clarifies the presentation of restricted cash and restricted cash equivalents in the statements of cash flows. Under this ASU, restricted cash and restricted cash equivalents are included with cash and cash equivalents when reconciling the beginning and end-of-period total amounts presented on the statements of cash flows. This ASU is intended to reduce diversity in practice in the classification and presentation of changes in restricted cash on the statement of cash flows. This ASU requires that the statement of cash flows explain the change in total cash and equivalents and amounts generally described as restricted cash or restricted cash equivalents when reconciling the beginning and end-of-period total amounts. This ASU also requires a reconciliation between the total of cash and equivalents and restricted cash presented on the statement of cash flows and the cash and equivalents balance presented on the balance sheet. This amended guidance was retrospectively adopted on January 1, 2018 and requires that cash, cash equivalents, and restricted cash reported on the consolidated statements of cash flows now includes restricted cash of $5.5 million as of December 31, 2018 and $4.5 million as of December 31, 2017, as well as previously reported cash and cash equivalents.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, “Leases (Topic 842)”, which requires lessees to recognize leases on the balance sheet and disclose key information about leasing arrangements. Topic 842 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. Topic 842 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. Topic 842 is effective for the Company beginning January 1, 2019, using a modified retrospective approach, with early adoption permitted. An entity may choose to use either the effective date or the beginning of the earliest comparative period presented in the financial statements as the date of initial application. The Company expects to adopt Topic 842 on January 1, 2019, using a modified retrospective approach, and to choose the effective date as the date of initial application. Consequently, financial information will not be updated, and the disclosures required under Topic 842 will not be provided for dates and periods prior to January 1, 2019. Topic 842 provides a number of optional practical expedients and accounting policy elections. The Company expects to elect 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. Further, the Company expects to elect accounting policies not to apply the recognition requirements under Topic 842 to any of the Company’s short-term leases, instead recognizing the lease payments in profit or loss on a straight-line basis over the lease term, and to account for each separate lease and associated nonlease components as a single lease component for all of its leases. The Company expects Topic 842 will have a material effect on its consolidated balance sheets. However, the Company does not expect Topic 842 will have a material effect on its consolidated statements of operations and comprehensive income (loss) or consolidated statements of cash flows. While the Company continues to assess all of the effects of adoption, the most significant effects relate to (1) the recognition of right-of-use (ROU) assets of approximately $49 million and lease liabilities of approximately $69 million, primarily resulting from leases of office and laboratory space; (2) the recognition of an existing deferred gain on a sale of real estate of approximately $8 million as a cumulative-effect adjustment to equity; (3) the derecognition of deferred rent of approximately $20 million for certain lease incentives received; and (4) significant new disclosure requirements. 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. This ASU does not apply to share-based payments used to effectively provide financing to the issuer or awards granted in conjunction with selling goods or services to customers as part of a contract accounted for under Topic 606. This update is effective for public business entities for fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. The Company does not expect this update will have a material impact on its consolidated financial statements and related disclosures.

INVESTMENTS (Tables)

INVESTMENTS (Tables)	12 Months Ended
	Dec. 31, 2018
Investments Schedule [Abstract]
Investments	Investments at December 31, 2018 and 2017 consisted of the following: December 31, (in thousands) 2018 2017 Commercial paper $ 94,572 $ 75,362 Corporate debt securities 544,978 414,815 Securities of government-sponsored entities 85,677 18,401 Total investments $ 725,227 $ 508,578
Summary of Investments Classified as Available-For-Sale Securities	The following is a summary of investments classified as available-for-sale securities: (in thousands) Contractual Maturity (in years) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Aggregate Estimated Fair Value 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 December 31, 2017: Classified as current assets: Commercial paper Less than 1 $ 75,396 $ 1 $ (35 ) $ 75,362 Corporate debt securities Less than 1 178,776 — (400 ) 178,376 Securities of government-sponsored entities Less than 1 7,503 — (24 ) 7,479 Total short-term available-for-sale securities $ 261,675 $ 1 $ (459 ) $ 261,217 Classified as non-current assets: Corporate debt securities 1 to 2 $ 237,749 $ — $ (1,310 ) $ 236,439 Securities of government-sponsored entities 1 to 2 11,004 — (82 ) 10,922 Total long-term available-for-sale securities $ 248,753 $ — $ (1,392 ) $ 247,361
Gross Unrealized Losses and Fair Value Available-For-Sale Investments in Unrealized Loss Position	The following table presents gross unrealized losses and fair value for those available-for-sale investments that were in an unrealized loss position as of December 31, 2018 and 2017, 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 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 ) December 31, 2017: Commercial paper $ 62,602 $ (35 ) $ — $ — $ 62,602 $ (35 ) Corporate debt securities 386,728 (1,660 ) 28,087 (50 ) 414,815 (1,710 ) Securities of government-sponsored entities 10,922 (82 ) 7,479 (24 ) 18,401 (106 ) Total $ 460,252 $ (1,777 ) $ 35,566 $ (74 ) $ 495,818 $ (1,851 ) At each reporting date, the Company performs 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 the Company’s intent and ability to hold the investment until recovery of its amortized cost basis. The Company intends, and has the ability, to hold its investments in unrealized loss positions until their amortized cost basis has been recovered. Based on its evaluation, the Company determined that its unrealized losses were not other-than-temporary at December 31, 2018 and 2017.

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Assets Measured at Fair Value on Recurring Basis	The Company’s assets, which are measured at fair value on a recurring basis as of December 31, 2018 and 2017, were determined using the inputs described above: 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) 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, cash equivalents and restricted cash (147.2 ) (147.2 ) — — Total investments $ 725.2 $ — $ 725.2 $ — December 31, 2017: Classified as current assets: Cash and money market funds $ 170.2 $ 170.2 $ — $ — Commercial paper 159.9 — 159.9 — Securities of government-sponsored entities 7.5 — 7.5 — Corporate debt securities 178.4 — 178.4 — Subtotal 516.0 170.2 345.8 — Classified as long-term assets: Cash and money market funds 1.5 1.5 — — Certificates of deposit 3.0 3.0 — — Securities of government-sponsored entities 10.9 — 10.9 — Corporate debt securities 236.4 — 236.4 — Total 767.8 174.7 593.1 — Less cash, cash equivalents and restricted cash (259.2 ) (174.6 ) (84.6 ) — Total investments $ 508.6 $ 0.1 $ 508.5 $ —

CONVERTIBLE SENIOR NOTES (Table

CONVERTIBLE SENIOR NOTES (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Convertible Senior Notes Net of Discounts and Deferred Financing Costs	Convertible senior notes, net of discounts and deferred financing costs consisted of the following: December 31, (in thousands) 2018 2017 Principal $ 517,500 $ 517,500 Deferred financing costs (8,326 ) (9,652 ) Debt discount, net (120,678 ) (138,230 ) Net carrying amount $ 388,496 $ 369,618

OTHER BALANCE SHEET DETAILS (Ta

OTHER BALANCE SHEET DETAILS (Tables)	12 Months Ended
	Dec. 31, 2018
Other Balance Sheet Details [Abstract]
Summary of Inventory	Inventory consisted of the following: December 31, (in thousands) 2018 2017 Raw materials $ 7,855 $ — Work in process 2,208 491 Finished goods 801 533 Total inventory $ 10,864 $ 1,024
Property and Equipment	Property and equipment, net, consisted of the following: December 31, (in thousands) 2018 2017 Tenant improvements $ 19,857 $ 2,019 Furniture and fixtures 2,968 1,303 Scientific equipment 28,163 26,248 Computer equipment 11,152 8,821 62,140 38,391 Less accumulated depreciation (28,271 ) (27,580 ) Property and equipment, net $ 33,869 $ 10,811
Accounts Payable and Accrued Liabilities	Accounts payable and accrued liabilities consisted of the following: December 31, (in thousands) 2018 2017 Accrued employee related costs $ 27,341 $ 24,901 Accounts payable 13,801 5,648 Accrued development costs 7,069 4,799 Other accrued liabilities 38,166 18,172 Total accounts payable and accrued liabilities $ 86,377 $ 53,520

NET INCOME (LOSS) PER SHARE (Ta

NET INCOME (LOSS) PER SHARE (Tables)	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Schedule of Net Income (Loss) Per Share	Net income (loss) per share was calculated as follows: Year Ended December 31, (in thousands, except per share data) 2018 2017 2016 Net income (loss) - basic and diluted $ 21,111 $ (142,542 ) $ (141,090 ) Weighted-average common shares outstanding: Basic 90,235 88,089 86,713 Effect of dilutive securities: Employee stock purchase program 11 — — Stock options 3,228 — — Restricted stock units 564 — — 2024 Notes 1,348 — — Diluted 95,386 88,089 86,713 Net income (loss) per share: Basic $ 0.23 $ (1.62 ) $ (1.63 ) Diluted $ 0.22 $ (1.62 ) $ (1.63 )
Schedule of Anti-Dilutive Shares Excluded from Diluted Per Share Amounts	Shares which have been excluded from diluted per share amounts because their effect would have been anti-dilutive include the following: Year Ended December 31, (in thousands) 2018 2017 2016 Stock options and restricted stock units 887 7,436 6,995

SHARE-BASED COMPENSATION (Table

SHARE-BASED COMPENSATION (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Compensation Cost Related to Share Based Compensation	Share-Based Compensation. The compensation cost that has been included in the statement of comprehensive income (loss) for all share-based compensation arrangements is as follows: Year Ended December 31, (in thousands) 2018 2017 2016 Sales, general and administrative expense $ 31,847 $ 27,951 $ 16,770 Research and development expense 26,221 14,571 11,694 Share-based compensation expense $ 58,068 $ 42,522 $ 28,464
Weighted-Average Assumptions for Stock Option Grants using Black-Scholes Option-Pricing Model	The estimated fair value of each stock option award granted was determined on the date of grant using the Black-Scholes option-pricing valuation model with the following weighted-average assumptions for option grants during the three years ended December 31, 2018: Year Ended December 31, (in thousands) 2018 2017 2016 Risk-free interest rate 2.5 % 2.0 % 1.4 % Expected volatility of common stock 59.5 % 58.0 % 60.0 % Dividend yield 0.0 % 0.0 % 0.0 % Expected option term 4.7 years 5.7 years 5.6 years
Summary and Changes in Stock Options Outstanding	A summary of the status of the Company’s stock options as of December 31, 2018, 2017 and 2016 and of changes in options outstanding under the plans during the three years ended December 31, 2018 is as follows: 2018 2017 2016 (in thousands, except weighted average data) Options Weighted Average Exercise Price Options Weighted Average Exercise Price Options Weighted Average Exercise Price Outstanding at January 1 6,356 $ 28.83 6,112 $ 20.01 5,507 $ 15.63 Granted 1,040 84.97 1,807 46.55 1,077 40.19 Exercised (1,592 ) 18.95 (1,353 ) 10.41 (341 ) 7.60 Canceled (58 ) 64.67 (210 ) 43.05 (131 ) 34.35 Outstanding at December 31 5,746 $ 41.38 6,356 $ 28.83 6,112 $ 20.01
Summary and Changes in Restricted Stock Units Outstanding	A summary of the status of the Company’s RSUs as of December 31, 2018, 2017, and 2016 and of changes in RSUs outstanding under the plans for the three years ended December 31, 2018 is as follows: 2018 2017 2016 (in thousands, except weighted average data) Number of Units Weighted Average Grant Date Fair Value per Unit Number of Units Weighted Average Grant Date Fair Value per Unit Number of Units Weighted Average Grant Date Fair Value per Unit Outstanding at January 1 1,080 $ 40.30 883 $ 29.33 910 $ 24.23 Granted 540 85.29 588 47.21 326 36.73 Cancelled (58 ) 36.21 (41 ) 40.62 (69 ) 32.50 Converted into common shares (429 ) 59.23 (350 ) 24.19 (284 ) 20.71 Outstanding at December 31 1,133 $ 62.31 1,080 $ 40.30 883 $ 29.33

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Components of Income Tax Expense for Continuing Operations	The components of the income tax expense for continuing operations are as follows: (in thousands) 2018 2017 2016 Current: Federal $ (100 ) $ — $ — State 830 — — Total income tax expense $ 730 $ — $ —
Provision for Income Taxes on Earnings Subject to Income Taxes Differs from Statutory Federal Rate	The provision for income taxes on earnings subject to income taxes differs from the statutory federal rate at December 31, 2018, 2017 and 2016, due to the following: (in thousands) 2018 2017 2016 Federal income taxes at 21% for 2018 and 35% for 2017 and 2016 $ 4,587 $ (49,889 ) $ (49,383 ) State income tax, net of federal benefit 361 (4,013 ) 2 Tax effect on non-deductible expenses 446 433 (321 ) Share-based compensation expense (9,778 ) (19,589 ) (5,077 ) Officer compensation 915 2,163 — Change in tax rate (198 ) 154,415 — Expired tax attributes 13,874 2,998 6,708 Research credits (13,526 ) (5,596 ) (5,554 ) Change in valuation allowance 4,306 (79,966 ) 53,414 Other (257 ) (956 ) 211 $ 730 $ — $ —
Components of Deferred Tax Assets	Amounts are shown as of December 31 as of each respective year: (in thousands) 2018 2017 Deferred tax assets: Net operating losses $ 223,800 $ 238,500 R&D credits 62,200 47,500 Capitalized R&D 34,800 47,500 Share-based compensation 17,300 14,600 Other 28,600 14,600 Total deferred tax assets 366,700 362,700 Deferred tax liabilities: Convertible senior notes (26,400 ) (31,300 ) Fixed assets (5,100 ) (500 ) Total deferred tax liabilities (31,500 ) (31,800 ) Net of deferred tax assets and liabilities 335,200 330,900 Valuation allowance (335,200 ) (330,900 ) Net deferred tax assets $ — $ —
Activity Related to Unrecognized Tax Benefits	The following table summarizes the activity related to unrecognized tax benefits: (in thousands) 2018 2017 2016 Balance as of the beginning of the year $ 37,403 $ 34,112 $ 33,074 Increases related to prior year tax positions 6,103 — 260 Increases related to current year tax positions 11,726 3,291 2,211 Expiration of the statute of limitations for the assessment of taxes (457 ) — (1,433 ) Balance as of the end of the year $ 54,775 $ 37,403 $ 34,112

SELECTED QUARTERLY FINANCIAL _2

SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Summary of Quarterly Results of Operations	The following is a summary of the quarterly results of the Company for the years ended December 31, 2018 and 2017: (in thousands, except per share data) First Quarter Second Quarter Third Quarter Fourth Quarter 2018: Revenues $ 71,086 $ 96,905 $ 151,757 $ 131,492 Operating expenses $ 108,533 $ 98,757 $ 97,434 $ 109,621 Net (loss) income $ (41,818 ) $ (5,913 ) $ 50,764 $ 18,078 Net (loss) income per share: Basic $ (0.47 ) $ (0.07 ) $ 0.56 $ 0.20 Diluted $ (0.47 ) $ (0.07 ) $ 0.52 $ 0.19 Shares used in the calculation of net (loss) income per share: Basic 89,526 90,100 90,555 90,742 Diluted 89,526 90,100 96,798 95,724 2017: Revenues $ — $ 6,335 $ 60,774 $ 94,517 Operating expenses $ 79,932 $ 63,603 $ 66,769 $ 82,683 Net (loss) income $ (78,326 ) $ (59,985 ) $ (11,125 ) $ 6,894 Net (loss) income per share: Basic $ (0.90 ) $ (0.68 ) $ (0.13 ) $ 0.08 Diluted $ (0.90 ) $ (0.68 ) $ (0.13 ) $ 0.07 Shares used in the calculation of net (loss) income per share: Basic 87,283 88,063 88,325 88,665 Diluted 87,283 88,063 88,325 92,659

Organization and Summary of S_3

Organization and Summary of Significant Accounting Policies - Additional Information (Detail) $ in Thousands, shares in Millions	May 02, 2017USD ($)	Dec. 31, 2018USD ($)SiteCustomershares	Dec. 31, 2017USD ($)Customer	Dec. 31, 2016USD ($)
Organization And Summary Of Significant Accounting Policies [Line Items]
Convertible senior notes principal amount		$ 517,500	$ 517,500
Depreciation		4,000	2,400	$ 1,500
Restricted cash		5,477	4,500
ASU 2016-18
Organization And Summary Of Significant Accounting Policies [Line Items]
Restricted cash		5,500	$ 4,500
ASU 2016-02 (Topic 842)
Organization And Summary Of Significant Accounting Policies [Line Items]
Right-of-use (ROU) assets		49,000
Lease liabilities		69,000
Derecognition of deferred rent for certain lease incentives received		20,000
ASU 2016-02 (Topic 842) | Recognition of Deferred Gain on Sale of Real Estate
Organization And Summary Of Significant Accounting Policies [Line Items]
Deferred gain on sale of real estate as cumulative-effect adjustment to equity		$ 8,000
Performance-based RSUs
Organization And Summary Of Significant Accounting Policies [Line Items]
Share equivalents excluded from computation of earnings per share | shares		0.3
ESPP
Organization And Summary Of Significant Accounting Policies [Line Items]
Purchase period		6 months
Customer Concentration Risk | Sales Revenue, Goods, Net
Organization And Summary Of Significant Accounting Policies [Line Items]
Number of customers | Customer		3	3
Percentage of product revenue		93.00%	93.00%
Customer Concentration Risk | Accounts Receivable
Organization And Summary Of Significant Accounting Policies [Line Items]
Number of customers | Customer		3	3
Ingrezza
Organization And Summary Of Significant Accounting Policies [Line Items]
Number of separate commercial production sites | Site		2
Advertising costs		$ 20,500	$ 10,100
Minimum
Organization And Summary Of Significant Accounting Policies [Line Items]
Average estimated useful life of equipment		3 years
Requisite service period of award		3 years
Maximum
Organization And Summary Of Significant Accounting Policies [Line Items]
Average estimated useful life of equipment		7 years
Requisite service period of award		4 years
2.25% Convertible Senior Notes due 2024
Organization And Summary Of Significant Accounting Policies [Line Items]
Convertible senior notes		7 years
Fair value of convertible senior note as percentage of principal amount		119.00%	128.00%
Convertible senior notes principal amount	$ 517,500
Convertible senior notes interest percentage	2.25%
Convertible senior notes interest rate	2.25%
Convertible senior notes convertible latest date		May 15, 2024
Share equivalents excluded from computation of earnings per share | shares		6.8

Significant Collaborative Res_2

Significant Collaborative Research and Development Agreements - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Jun. 30, 2010	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 31, 2018
Mitsubishi Tanabe
Collaborative Arrangements And Noncollaborative Arrangement Transactions [LineItems]
Up-front license fees					$ 30,000,000
Collaborative agreement maximum additional payment to receive					85,000,000
Patent rights period		The longer of ten years or the life of the related patent rights.
Collaborative arrangement right description		Under the terms of the agreement, Mitsubishi Tanabe is responsible for all third-party development, marketing and commercialization costs in Japan and other select Asian markets and the Company would be entitled to a percentage of sales of INGREZZA in Japan and other select Asian markets for the longer of ten years or the life of the related patent rights. Further, the collaboration effort between the parties to advance INGREZZA towards commercialization in Japan and other select Asian markets is governed by joint steering and development committees with representatives from both parties. There are no performance, cancellation, termination, or refund provisions in the agreement that would have a material financial consequence to the Company. The Company does not directly control when event-based payments will be achieved or when royalty payments will begin. Mitsubishi Tanabe may terminate the agreement at its discretion upon 180 days written notice to the Company. In such event, all INGREZZA product rights for Japan and other select Asian markets would revert to the Company.
Collaboration termination notice period		180 days
Revenues recognized under collaboration agreement		$ 0	$ 15,000,000	$ 0	19,800,000
Deferred revenues under collaboration					$ 10,200,000
Mitsubishi Tanabe | Topic 606
Collaborative Arrangements And Noncollaborative Arrangement Transactions [LineItems]
Clinical trial cost		12,000,000
Up-front consideration received		$ 30,000,000
AbbVie
Collaborative Arrangements And Noncollaborative Arrangement Transactions [LineItems]
Up-front license fees	$ 75,000,000
Patent rights period		Ten years or the life of the related patent rights.
Collaborative arrangement right description		The Company will be entitled to a percentage of worldwide sales of GnRH Compounds for the longer of ten years or the life of the related patent rights.
Collaboration termination notice period		180 days
Revenues recognized under collaboration agreement		$ 40,000,000	30,000,000	$ 15,000,000
Sales-based royalties		1,600,000
AbbVie | Development and Regulatory Milestone Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [LineItems]
Collaborative agreement maximum additional payment to receive		480,000,000
Collaborative agreement payment received		115,000,000
AbbVie | Commercial Milestone Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [LineItems]
Collaborative agreement maximum additional payment to receive		50,000,000
AbbVie | Topic 606
Collaborative Arrangements And Noncollaborative Arrangement Transactions [LineItems]
Up-front consideration received		$ 75,000,000
B I A L
Collaborative Arrangements And Noncollaborative Arrangement Transactions [LineItems]
Up-front license fees			$ (30,000,000)
License agreement date			Feb. 9, 2017
B I A L | Event Based Milestones
Collaborative Arrangements And Noncollaborative Arrangement Transactions [LineItems]
Milestone payables						$ 10,000,000
B I A L | Regulatory Approval and Net Sales Milestones
Collaborative Arrangements And Noncollaborative Arrangement Transactions [LineItems]
Milestone payables						105,000,000
B I A L | Regulatory and Clinical Results and FDA Acceptance Milestones
Collaborative Arrangements And Noncollaborative Arrangement Transactions [LineItems]
Milestone payables						$ 10,000,000

Investments (Detail)

Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Investments [Line Items]
Investments	$ 725,227	$ 508,578
Commercial paper
Schedule Of Investments [Line Items]
Investments	94,572	75,362
Corporate debt securities
Schedule Of Investments [Line Items]
Investments	544,978	414,815
Securities of government-sponsored entities
Schedule Of Investments [Line Items]
Investments	$ 85,677	$ 18,401

Summary of Investments Classifi

Summary of Investments Classified as Available-For-Sale Securities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Available For Sale Securities [Line Items]
Aggregate Estimated Fair Value	$ 725,227	$ 508,578
Commercial paper
Schedule Of Available For Sale Securities [Line Items]
Aggregate Estimated Fair Value	94,572	75,362
Corporate debt securities
Schedule Of Available For Sale Securities [Line Items]
Aggregate Estimated Fair Value	544,978	414,815
Securities of government-sponsored entities
Schedule Of Available For Sale Securities [Line Items]
Aggregate Estimated Fair Value	85,677	18,401
Short-term investments
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	510,889	261,675
Gross Unrealized Gains	8	1
Gross Unrealized Losses	(1,698)	(459)
Aggregate Estimated Fair Value	509,199	261,217
Short-term investments | Commercial paper
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	94,617	75,396
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(45)	(35)
Aggregate Estimated Fair Value	$ 94,572	$ 75,362
Short-term investments | Commercial paper | Maximum
Schedule Of Available For Sale Securities [Line Items]
Available for sale securities contractual maturity	1 year	1 year
Short-term investments | Corporate debt securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 395,385	$ 178,776
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1,598)	(400)
Aggregate Estimated Fair Value	$ 393,787	$ 178,376
Short-term investments | Corporate debt securities | Maximum
Schedule Of Available For Sale Securities [Line Items]
Available for sale securities contractual maturity	1 year	1 year
Short-term investments | Securities of government-sponsored entities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 20,887	$ 7,503
Gross Unrealized Gains	8	0
Gross Unrealized Losses	(55)	(24)
Aggregate Estimated Fair Value	$ 20,840	$ 7,479
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	1 year
Long-term investments
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 216,270	$ 248,753
Gross Unrealized Gains	228	0
Gross Unrealized Losses	(470)	(1,392)
Aggregate Estimated Fair Value	216,028	247,361
Long-term investments | Corporate debt securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	151,594	237,749
Gross Unrealized Gains	66	0
Gross Unrealized Losses	(469)	(1,310)
Aggregate Estimated Fair Value	$ 151,191	$ 236,439
Long-term investments | Corporate debt securities | Minimum
Schedule Of Available For Sale Securities [Line Items]
Available for sale securities contractual maturity	1 year	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	2 years
Long-term investments | Securities of government-sponsored entities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 64,676	$ 11,004
Gross Unrealized Gains	162	0
Gross Unrealized Losses	(1)	(82)
Aggregate Estimated Fair Value	$ 64,837	$ 10,922
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	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	2 years

Gross Unrealized Losses and Fai

Gross Unrealized Losses and Fair Value Available-For-Sale Investments in Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Estimated Fair Value	$ 331,622	$ 460,252
Less Than 12 Months, Unrealized Losses	(792)	(1,777)
12 Months or Greater, Estimated Fair Value	245,745	35,566
12 Months or Greater, Unrealized Losses	(1,376)	(74)
Total Estimated Fair Value	577,367	495,818
Total Unrealized Losses	(2,168)	(1,851)
Commercial paper
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Estimated Fair Value	51,927	62,602
Less Than 12 Months, Unrealized Losses	(45)	(35)
12 Months or Greater, Estimated Fair Value	0	0
12 Months or Greater, Unrealized Losses	0	0
Total Estimated Fair Value	51,927	62,602
Total Unrealized Losses	(45)	(35)
Corporate debt securities
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Estimated Fair Value	274,696	386,728
Less Than 12 Months, Unrealized Losses	(746)	(1,660)
12 Months or Greater, Estimated Fair Value	234,798	28,087
12 Months or Greater, Unrealized Losses	(1,321)	(50)
Total Estimated Fair Value	509,494	414,815
Total Unrealized Losses	(2,067)	(1,710)
Securities of government-sponsored entities
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Estimated Fair Value	4,999	10,922
Less Than 12 Months, Unrealized Losses	(1)	(82)
12 Months or Greater, Estimated Fair Value	10,947	7,479
12 Months or Greater, Unrealized Losses	(55)	(24)
Total Estimated Fair Value	15,946	18,401
Total Unrealized Losses	$ (56)	$ (106)

Assets Measured at Fair Value o

Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	$ 725.2	$ 508.6
Short-term investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	650.9	516
Short-term investments | Cash and money market fund
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	141.7	170.2
Short-term investments | Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	94.6	159.9
Short-term investments | Securities of government-sponsored entities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	20.8	7.5
Short-term investments | Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	393.8	178.4
Long-term investments | Cash and money market fund
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	1.5	1.5
Long-term investments | Certificates of deposit
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	4	3
Long-term investments | Securities of government-sponsored entities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	64.8	10.9
Long-term investments | Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	151.2	236.4
Investments Including Cash Equivalents And Restricted Cash
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	872.4	767.8
Cash and Cash Equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying Value	147.2	259.2
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0	0.1
Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term investments | Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	141.7	170.2
Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term investments | Cash and money market fund | Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	141.7	170.2
Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term investments | Commercial paper | Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0	0
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
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
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	3
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
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
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	147.2	174.7
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash and Cash Equivalents | Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	147.2	174.6
Significant Other Observable Inputs (Level 2) | Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	725.2	508.5
Significant Other Observable Inputs (Level 2) | Short-term investments | Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	509.2	345.8
Significant Other Observable Inputs (Level 2) | Short-term investments | Cash and money market fund | Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0	0
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	94.6	159.9
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	20.8	7.5
Significant Other Observable Inputs (Level 2) | Short-term investments | Corporate debt securities | Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	393.8	178.4
Significant Other Observable Inputs (Level 2) | Long-term investments | Cash and money market fund | Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0	0
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
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	64.8	10.9
Significant Other Observable Inputs (Level 2) | Long-term investments | Corporate debt securities | Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	151.2	236.4
Significant Other Observable Inputs (Level 2) | Investments Including Cash Equivalents And Restricted Cash | Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	725.2	593.1
Significant Other Observable Inputs (Level 2) | Cash and Cash Equivalents | Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0	84.6
Significant Unobservable Inputs (Level 3) | Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0	0
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
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
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
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
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
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
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
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
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
Significant Unobservable Inputs (Level 3) | Investments Including Cash Equivalents And Restricted Cash | Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of assets on recurring basis	0	0
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

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
2.25% Convertible Senior Notes due 2024 | Significant Other Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt instrument fair value	$ 616.1	$ 662.1

Convertible Senior Notes - Addi

Convertible Senior Notes - Additional Information (Detail) $ / shares in Units, shares in Millions	May 02, 2017USD ($)	Dec. 31, 2018USD ($)d$ / sharesshares	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Debt Instrument [Line Items]
Convertible senior notes principal amount		$ 517,500,000	$ 517,500,000
Proceeds from Senior Convertible Notes		$ 0	$ 502,781,000	$ 0
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 VWAP of the Company’s common stock.
Debt instrument conversion share amount description		The “share amount” is the cumulative “daily share amount” during the observation period, which is calculated by dividing the daily VWAP into the difference between the daily conversion value (i.e., conversion rate x daily VWAP) and $1,000.
Convertible senior notes convertible in to shares		0.00131711
Convertible senior notes conversion price | $ / shares		$ 75.92
Shares issued to settle notes at initial conversion rate | shares		6.8
Market Price of Common stock | $ / shares		$ 53.28
Convertible senior note premium		42.50%
Convertible senior notes redemption rate		100.00%
Fair value of convertible senior note as percentage of principal amount		119.00%	128.00%
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 - Conv

Convertible Senior Notes - Convertible Senior Notes, Net of Discounts and Deferred Financing Costs (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Disclosure [Abstract]
Principal	$ 517,500	$ 517,500
Deferred financing costs	(8,326)	(9,652)
Debt discount, net	(120,678)	(138,230)
Net carrying amount	$ 388,496	$ 369,618

Other Balance Sheet Details - S

Other Balance Sheet Details - Summary of Inventory (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Other Balance Sheet Details [Abstract]
Raw materials	$ 7,855	$ 0
Work in process	2,208	491
Finished goods	801	533
Total inventory	$ 10,864	$ 1,024

Other Balance Sheet Details - P

Other Balance Sheet Details - Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment	$ 62,140	$ 38,391
Less accumulated depreciation	(28,271)	(27,580)
Property and equipment, net	33,869	10,811
Tenant improvements
Property, Plant and Equipment [Line Items]
Property and equipment	19,857	2,019
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment	2,968	1,303
Scientific equipment
Property, Plant and Equipment [Line Items]
Property and equipment	28,163	26,248
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment	$ 11,152	$ 8,821

Other Balance Sheet Details - A

Other Balance Sheet Details - Accounts Payable and Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Other Balance Sheet Details [Abstract]
Accrued employee related costs	$ 27,341	$ 24,901
Accounts payable	13,801	5,648
Accrued development costs	7,069	4,799
Other accrued liabilities	38,166	18,172
Total accounts payable and accrued liabilities	$ 86,377	$ 53,520

Net Income (Loss) Per Share - S

Net Income (Loss) Per Share - Schedule of Net Income (Loss) Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Net income (loss) - basic and diluted	$ 18,078	$ 50,764	$ (5,913)	$ (41,818)	$ 6,894	$ (11,125)	$ (59,985)	$ (78,326)	$ 21,111	$ (142,542)	$ (141,090)
Weighted-average common shares outstanding:
Basic	90,742,000	90,555,000	90,100,000	89,526,000	88,665,000	88,325,000	88,063,000	87,283,000	90,235,000	88,089,000	86,713,000
Effect of dilutive securities:
Employee stock purchase program									11,000	0	0
Stock options									3,228,000	0	0
Restricted stock units									564,000	0	0
2024 Notes									1,348,000	0	0
Diluted	95,724,000	96,798,000	90,100,000	89,526,000	92,659,000	88,325,000	88,063,000	87,283,000	95,386,000	88,089,000	86,713,000
Net income (loss) per share:
Basic	$ 0.20	$ 0.56	$ (0.07)	$ (0.47)	$ 0.08	$ (0.13)	$ (0.68)	$ (0.90)	$ 0.23	$ (1.62)	$ (1.63)
Diluted	$ 0.19	$ 0.52	$ (0.07)	$ (0.47)	$ 0.07	$ (0.13)	$ (0.68)	$ (0.90)	$ 0.22	$ (1.62)	$ (1.63)

Net Income (Loss) Per Share -_2

Net Income (Loss) Per Share - Schedule of Anti-Dilutive Shares Excluded from Diluted Per Share Amounts (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock Options and Restricted Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from diluted per share amounts	887	7,436	6,995

Share-Based Compensation - Addi

Share-Based Compensation - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	May 31, 2018	Dec. 31, 2015	May 31, 2011
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options granted	1,040,000	1,807,000	1,077,000
Stock options outstanding	5,746,000	6,356,000	6,112,000		5,507,000
Number of common stock available for future grant	6,800,000
Weighted-average fair values of stock options granted	$ 43.42	$ 25.11	$ 21.49
Weighted average remaining contractual term for stock options outstanding	6 years 8 months 12 days
Share-based compensation expense	$ 58,068,000	$ 42,522,000	$ 28,464,000
Number of stock options exercisable	3,900,000
Stock options exercisable, weighted average exercise price	$ 31.07
Stock options exercisable, weighted-average remaining contractual term	5 years 10 months 24 days
Stock options exercised in period intrinsic value	$ 117,000,000	61,400,000	13,200,000
Stock options intrinsic value of options outstanding	186,300,000
Stock options intrinsic value of options exercisable	158,200,000
Cash received from stock option exercises	$ 29,500,000	$ 13,900,000	$ 2,400,000
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation, term	3 years
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation, term	4 years
Share-based compensation, contractual term	10 years
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock units granted	540,000	588,000	326,000
Share-based compensation expense	$ 21,900,000	$ 13,900,000	$ 8,300,000
Unrecognized compensation cost	$ 51,600,000
Stock vesting period	2 years 3 months 18 days
Total intrinsic value vested in period	$ 35,500,000	14,900,000	12,200,000
Intrinsic value outstanding	$ 80,900,000
Restricted Stock Units (RSUs) | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock vesting period	4 years
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	$ 35,400,000	$ 28,200,000	$ 18,400,000
Unrecognized compensation cost	$ 55,400,000
Stock vesting period	2 years 3 months 18 days
Stock Options | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock vesting period	3 years
Share-based compensation, term	7 years
Stock Options | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock vesting period	4 years
Share-based compensation, term	10 years
Performance-based RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock units granted	200,000	0	200,000
Share-based compensation expense	$ 0	$ 400,000	$ 1,800,000
Unrecognized compensation cost	19,700,000
Intrinsic value outstanding	$ 23,600,000
Performance restricted stock units earned during period	0	200,000	0
Performance-based RSUs | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock vesting period	4 years
Performance-based RSUs | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock vesting period	5 years
Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options granted	70,000	410,000	0
Stock vesting period	4 years	4 years
Stock options outstanding	245,162
Employees | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock units granted	20,000	12,500	0
RSUs outstanding	245,162
Employees | Restricted Stock Units (RSUs) | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock vesting period	3 years	3 years
Employees | Restricted Stock Units (RSUs) | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock vesting period	4 years	4 years
ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of common stock authorized for issuance	300,000			300,000
Number of shares purchased	0
Share-based compensation expense	$ 800,000
ESPP | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Discounted purchase price percentage of common stock authorized for issuance	85.00%
2011 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of common stock authorized for issuance						19,000,000
Share Based Compensation Arrangement Award
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of common stock authorized for issuance	7,200,000
PRSUs Converted into Common Shares | Performance-based RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Intrinsic value outstanding		$ 8,800,000

Compensation Cost Related to Sh

Compensation Cost Related to Share-Based Compensation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	$ 58,068	$ 42,522	$ 28,464
Sales, General and Administrative Expense
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	31,847	27,951	16,770
Research and Development Expense
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	$ 26,221	$ 14,571	$ 11,694

Weighted-Average Assumptions fo

Weighted-Average Assumptions for Stock Option Grants using Black-Scholes Option-Pricing Model (Detail) - Stock Options	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	2.50%	2.00%	1.40%
Expected volatility of common stock	59.50%	58.00%	60.00%
Dividend yield	0.00%	0.00%	0.00%
Expected option term	4 years 8 months 12 days	5 years 8 months 12 days	5 years 7 months 6 days

Summary and Changes in Stock Op

Summary and Changes in Stock Options Outstanding (Detail) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Shares
Outstanding, Beginning Balance	6,356	6,112	5,507
Granted	1,040	1,807	1,077
Exercised	(1,592)	(1,353)	(341)
Canceled	(58)	(210)	(131)
Outstanding, Ending Balance	5,746	6,356	6,112
Weighted average exercise price
Outstanding, Beginning Balance	$ 28.83	$ 20.01	$ 15.63
Granted	84.97	46.55	40.19
Exercised	18.95	10.41	7.60
Canceled	64.67	43.05	34.35
Outstanding, Ending Balance	$ 41.38	$ 28.83	$ 20.01

Summary and Changes in Restrict

Summary and Changes in Restricted Stock Units Outstanding (Detail) - Restricted Stock Units (RSUs) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restricted stock units
Outstanding, Beginning Balance	1,080	883	910
Granted	540	588	326
Cancelled	(58)	(41)	(69)
Converted into common shares	(429)	(350)	(284)
Outstanding Ending Balance	1,133	1,080	883
Weighted average grant date fair value
Outstanding Beginning Balance	$ 40.30	$ 29.33	$ 24.23
Granted	85.29	47.21	36.73
Cancelled	36.21	40.62	32.50
Converted into common shares	59.23	24.19	20.71
Outstanding Ending Balance	$ 62.31	$ 40.30	$ 29.33

Components of Income Tax Expens

Components of Income Tax Expense for Continuing Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal	$ (100)	$ 0	$ 0
State	830	0	0
Total income tax expense	$ 730	$ 0	$ 0

Provision for Income Taxes on E

Provision for Income Taxes on Earnings Subject to Income Taxes Differs from Statutory Federal Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Federal income taxes at 21% for 2018 and 35% for 2017 and 2016	$ 4,587	$ (49,889)	$ (49,383)
State income tax, net of federal benefit	361	(4,013)	2
Tax effect on non-deductible expenses	446	433	(321)
Share-based compensation expense	(9,778)	(19,589)	(5,077)
Officer compensation	915	2,163	0
Change in tax rate	(198)	154,415	0
Expired tax attributes	13,874	2,998	6,708
Research credits	(13,526)	(5,596)	(5,554)
Change in valuation allowance	4,306	(79,966)	53,414
Other	(257)	(956)	211
Income Tax Expense (Benefit), Total	$ 730	$ 0	$ 0

Provision for Income Taxes on_2

Provision for Income Taxes on Earnings Subject to Income Taxes Differs from Statutory Federal Rate (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Federal income taxes, rate	21.00%	35.00%	35.00%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Line Items]
Deferred tax assets, valuation allowance	$ 335,200	$ 330,900
Research and development tax credit carry forwards	$ 62,200	$ 47,500
Corporate tax rate	21.00%	35.00%	35.00%
Percentage of uncertain tax positions likelihood of being sustained	50.00%
Increases related to current year tax positions	$ 11,726	$ 3,291	$ 2,211
Unrecognized tax benefits that would affect effective tax rate	50,100
Federal
Income Taxes [Line Items]
Operating loss carry forward, net	$ 1,000,000
Operating loss carry forward beginning expiration year	2,021
Research and development tax credit carry forwards	$ 63,600
Federal | R&D
Income Taxes [Line Items]
Tax credit carry forwards beginning expiration year	2,018
State and Local Jurisdiction
Income Taxes [Line Items]
Operating loss carry forward, net	$ 398,000
Research and development tax credit carry forwards	$ 41,600
State and Local Jurisdiction | California
Income Taxes [Line Items]
Operating loss carry forward beginning expiration year	2,028
State and Local Jurisdiction | Other States
Income Taxes [Line Items]
Operating loss carry forward beginning expiration year	2,026

Components of Deferred Tax Asse

Components of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating losses	$ 223,800	$ 238,500
R&D credits	62,200	47,500
Capitalized R&D	34,800	47,500
Share-based compensation	17,300	14,600
Other	28,600	14,600
Total deferred tax assets	366,700	362,700
Deferred tax liabilities:
Convertible senior notes	(26,400)	(31,300)
Fixed assets	(5,100)	(500)
Total deferred tax liabilities	(31,500)	(31,800)
Net of deferred tax assets and liabilities	335,200	330,900
Valuation allowance	(335,200)	(330,900)
Net deferred tax assets	$ 0	$ 0

Activity Related to Unrecognize

Activity Related to Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Unrecognized tax benefit beginning Balance	$ 37,403	$ 34,112	$ 33,074
Increases related to prior year tax positions	6,103	0	260
Increases related to current year tax positions	11,726	3,291	2,211
Expiration of the statute of limitations for the assessment of taxes	(457)	0	(1,433)
Unrecognized tax benefit ending Balance	$ 54,775	$ 37,403	$ 34,112

Leases - Additional Information

Leases - Additional Information (Detail) $ in Millions	1 Months Ended		12 Months Ended
	Jun. 30, 2017USD ($)	Dec. 31, 2007USD ($)Building	Dec. 31, 2018USD ($)BuildingRenewalOption	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	May 31, 2018USD ($)ft²	Dec. 31, 2008USD ($)
Leases [Line Items]
Sale of facility and associated real property		$ 109
Mortgage debt retired		47.7
Cash received net of transaction costs and debt retirement		$ 61
Net deferred gain on real estate sale			$ 7.3				$ 39.1
Deferred gain recognized on real estate sale			$ 0.7	$ 2.1	$ 3.4
Leaseback transaction lease period		12 years
Number of building leased | Building		2	1
Number of vacated buildings | Building			1
Percentage of management fee included in the base annual rent	3.50%
Lease security deposit	$ 4.7
Letter of credit	$ 3
Number of times to renew the lease contract | RenewalOption			2
Lease extension period			10 years
Rent expense			$ 6.9	$ 5.9	$ 6
Amended Lease Term
Leases [Line Items]
Lease expiration date			Dec. 31, 2029
Percentage reduction in base rental	8.00%
Tenant improvement allowances	$ 13.1
Lease security deposit	$ 3
Lease Agreement
Leases [Line Items]
Tenant improvement allowances						$ 4.2
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

Retirement Plan - Additional In

Retirement Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Compensation And Retirement Disclosure [Abstract]
Defined contribution plan, maximum employee contribution percentage	60.00%
Defined contribution plan, employer contribution amount	$ 1.8	$ 1.1	$ 0.6

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Billions	12 Months Ended
	Dec. 31, 2018USD ($)
Minimum
Commitment And Contingencies [Line Items]
Lease cancellation, notice period	0 days
Maximum
Commitment And Contingencies [Line Items]
Lease cancellation, notice period	180 days
Milestone payables	$ 1
Royalty, rate	6.00%

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - USD ($)	Jan. 28, 2019	Dec. 31, 2018
Maximum
Subsequent Event [Line Items]
Milestone payables		$ 1,000,000,000
Voyager Therapeutics | Collaboration and License Agreement
Subsequent Event [Line Items]
Collaborative arrangement right description		Under the terms of the agreement, on a program-by-program basis, upon the achievement of milestones or metrics specified in the agreement for VY-AADC and VY-FXN01, Voyager will have the option to co-develop and co-commercialize such program with the Company in the U.S. under cost- and profit-sharing arrangements, and Voyager agrees to forfeit certain milestones and royalties related to such program for which Voyager has exercised its co-develop and co-commercialize option.
Voyager Therapeutics | Subsequent Event | Collaboration and License Agreement
Subsequent Event [Line Items]
Up-front cash payable	$ 115,000,000
Collaborative agreement equity investment amount	50,000,000
Voyager Therapeutics | Subsequent Event | Collaboration and License Agreement | Development, Regulatory and Commercial Milestone Payment | Maximum
Subsequent Event [Line Items]
Milestone payables	$ 1,700,000,000

Summary of Quarterly Results of

Summary of Quarterly Results of Operations (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 131,492	$ 151,757	$ 96,905	$ 71,086	$ 94,517	$ 60,774	$ 6,335	$ 0	$ 451,240	$ 161,626	$ 15,000
Operating expenses	109,621	97,434	98,757	108,533	82,683	66,769	63,603	79,932	414,345	292,987	162,372
Net (loss) income	$ 18,078	$ 50,764	$ (5,913)	$ (41,818)	$ 6,894	$ (11,125)	$ (59,985)	$ (78,326)	$ 21,111	$ (142,542)	$ (141,090)
Net (loss) income per share:
Basic	$ 0.20	$ 0.56	$ (0.07)	$ (0.47)	$ 0.08	$ (0.13)	$ (0.68)	$ (0.90)	$ 0.23	$ (1.62)	$ (1.63)
Diluted	$ 0.19	$ 0.52	$ (0.07)	$ (0.47)	$ 0.07	$ (0.13)	$ (0.68)	$ (0.90)	$ 0.22	$ (1.62)	$ (1.63)
Shares used in the calculation of net income (loss) per share:
Basic	90,742	90,555	90,100	89,526	88,665	88,325	88,063	87,283	90,235	88,089	86,713
Diluted	95,724	96,798	90,100	89,526	92,659	88,325	88,063	87,283	95,386	88,089	86,713