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Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2016	Oct. 31, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q3
Trading Symbol	ACAD
Entity Registrant Name	ACADIA PHARMACEUTICALS INC
Entity Central Index Key	0001070494
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		121,113,846

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Assets
Cash and cash equivalents	$ 153,679	$ 102,138
Investment securities, available-for-sale	435,180	112,994
Accounts receivable, net	3,839
Interest and other receivables	1,385	1,638
Inventory	4,301
Prepaid expenses and other current assets	5,106	2,219
Total current assets	603,490	218,989
Property and equipment, net	3,159	2,203
Intangible assets, net	7,385
Restricted cash	2,375	375
Other assets	975	329
Total assets	617,384	221,896
Liabilities and stockholders’ equity
Accounts payable	2,828	1,672
Accrued liabilities	34,445	20,230
Deferred revenue	1,876
Total current liabilities	39,149	21,902
Long-term liabilities	177	232
Total liabilities	39,326	22,134
Commitments and contingencies (Note 9)
Stockholders’ equity:
Preferred stock, $0.0001 par value; 5,000,000 shares authorized at September 30, 2016 and December 31, 2015; no shares issued and outstanding at September 30, 2016 and December 31, 2015
Common stock, $0.0001 par value; 225,000,000 shares authorized at September 30, 2016 and December 31, 2015; 121,107,222 shares and 101,938,702 shares issued and outstanding at September 30, 2016 and December 31, 2015, respectively	12	10
Additional paid-in capital	1,432,796	862,327
Accumulated deficit	(855,283)	(662,586)
Accumulated other comprehensive income	533	11
Total stockholders’ equity	578,058	199,762
Total liabilities and stockholders’ equity	$ 617,384	$ 221,896

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
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	$ 0.0001	$ 0.0001
Common stock, shares authorized	225,000,000	225,000,000
Common stock, shares issued	121,107,222	101,938,702
Common stock, shares outstanding	121,107,222	101,938,702

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenues
Product sales, net	$ 5,268		$ 5,365
Collaborative revenue		$ 39	4	$ 44
Total revenues	5,268	39	5,369	44
Operating expenses
Cost of product sales	845		1,371
License fees and royalties	475		723
Research and development	25,813	18,729	69,066	53,403
Selling, general and administrative	50,534	20,308	128,793	65,688
Total operating expenses	77,667	39,037	199,953	119,091
Loss from operations	(72,399)	(38,998)	(194,584)	(119,047)
Interest income, net	786	92	1,887	388
Net loss	$ (71,613)	$ (38,906)	$ (192,697)	$ (118,659)
Net loss per common share, basic and diluted	$ (0.61)	$ (0.39)	$ (1.69)	$ (1.18)
Weighted average common shares outstanding, basic and diluted	117,497	100,756	114,063	100,436

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (71,613)	$ (38,906)	$ (192,697)	$ (118,659)
Other comprehensive gain (loss):
Unrealized gain on investment securities	328	34	524	51
Foreign currency translation adjustments	(1)		(2)	3
Comprehensive loss	$ (71,286)	$ (38,872)	$ (192,175)	$ (118,605)

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities
Net loss	$ (192,697)	$ (118,659)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	39,847	31,292
Amortization of premiums and accretion of discounts on investment securities, available for sale	145	(1,902)
Amortization of intangible assets	615
Depreciation	583	519
Loss on disposal of assets	5
Changes in operating assets and liabilities:
Accounts receivable, net	(3,839)
Interest and other receivables	253	758
Inventory	(3,503)
Prepaid expenses and other current assets	(2,887)	(782)
Restricted cash	(2,000)
Other assets	(646)	(118)
Accounts payable	994	144
Accrued liabilities	14,090	1,571
Deferred revenue	1,876
Long-term liabilities	(55)	104
Net cash used in operating activities	(147,219)	(87,073)
Cash flows from investing activities
Purchases of investment securities	(592,868)	(215,926)
Maturities of investment securities	271,061	308,619
Intangible assets	(8,000)
Purchases of property and equipment	(1,257)	(1,848)
Net cash (used in) provided by investing activities	(331,064)	90,845
Cash flows from financing activities
Proceeds from issuance of common stock, net of issuance costs	515,506	5,170
Proceeds from settlement agreement	14,320
Net cash provided by financing activities	529,826	5,170
Effect of exchange rate changes on cash	(2)	3
Net increase in cash and cash equivalents	51,541	8,945
Cash and cash equivalents
Beginning of period	102,138	61,854
End of period	153,679	70,799
Supplemental disclosure of noncash information:
Property and equipment purchases in accounts payable and accrued liabilities	287	$ 186
Stock-based compensation capitalized in inventory	$ 798

Organization and Business	9 Months Ended
Organization and Business	Sep. 30, 2016
Accounting Policies [Abstract]
Organization and Business	1. Organization and Business ACADIA Pharmaceuticals Inc. (the “Company”), based in San Diego, California, is a biopharmaceutical company focused on the development and commercialization of innovative medicines to address unmet medical needs in central nervous system disorders. The Company was originally incorporated in Vermont in 1993 as Receptor Technologies, Inc. and reincorporated in Delaware in 1997. On April 29, 2016, the U.S. Food and Drug Administration (“FDA”) approved the Company’s first drug, NUPLAZID^® (pimavanserin), for the treatment of hallucinations and delusions associated with Parkinson’s disease psychosis. NUPLAZID became available for prescription in the United States on May 31, 2016.

Basis of Presentation and Significant Accounting Policies	9 Months Ended
	Sep. 30, 2016
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies	2. Basis of Presentation and Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed consolidated financial statements of ACADIA Pharmaceuticals Inc. should be read in conjunction with the audited financial statements and notes thereto as of and for the year ended December 31, 2015 included in the Company’s Annual Report on Form 10-K (“Annual Report”) filed with the Securities and Exchange Commission (the “SEC”). The accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) for interim financial information and in accordance with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, since they are interim statements, the accompanying financial statements do not include all of the information and notes required by GAAP for complete financial statements. In the opinion of management, the accompanying financial statements reflect all adjustments (consisting of normal recurring adjustments) that are necessary for a fair statement of the financial position, results of operations and cash flows for the interim periods presented. Interim results are not necessarily indicative of results for a full year. The preparation of financial statements in conformity with 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. Accounts Receivable Accounts receivable are recorded net of customer allowances for prompt payment discounts, distribution fees, chargebacks, and 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, the Company has determined that an allowance for doubtful accounts is not required. Inventory Inventory, consisting of raw material and finished goods, is stated at the lower of cost or estimated net realizable value. The Company uses a combination of standard and actual costing methodologies to determine the cost basis for its inventories which approximates actual costs. Inventory is valued on a first-in, first-out basis and includes third-party manufacturing costs, freight, and indirect overhead 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 NUPLAZID, all costs related to the manufacturing of NUPLAZID were charged to research and development expense in the period incurred. At September 30, 2016 the Company had an immaterial amount of zero cost raw material that was available for use in the manufacturing of commercial product. The Company provides reserves for potentially excess, dated or obsolete inventory based on an analysis of forecasted demand compared to quantities on hand and any firm purchase orders, as well as product shelf life. To date, the Company has determined that a reserve for potentially excess, dated or obsolete inventory is not required. License Fees and Royalties The Company expenses amounts paid to acquire licenses associated with products under development when the ultimate recoverability of the amounts paid is uncertain and the technology has no alternative future use when acquired. Acquisitions of technology licenses are charged to expense or capitalized based upon management’s assessment regarding the ultimate recoverability of the amounts paid and the potential for alternative future use. The Company has determined that technological feasibility for its product candidates is reached when the requisite regulatory approvals are obtained to make the product available for sale. In connection with the FDA approval of NUPLAZID in April 2016, the Company made a one-time milestone payment of $8.0 million pursuant to its 2006 license agreement with the Ipsen Group in which the Company licensed certain intellectual property rights that complement its patent portfolio for its serotonin platform, including NUPLAZID. The Company has capitalized the $8.0 million payment as an intangible asset and is amortizing the asset on a straight-line basis over the estimated useful life of the licensed patents through the second half of 2021. The Company recorded amortization expense related to its intangible asset of $369,000 and $615,000 for the three and nine months ended September 30, 2016, respectively. As of September 30, 2016, estimated future amortization expense related to the Company’s intangible asset was $369,000 for the remainder of 2016, $1.5 million for each of 2017, 2018, 2019, and 2020, and $1.1 million thereafter. Royalty expense incurred in connection with the Company’s license agreement with the Ipsen Group, as disclosed in Note 9, Commitments and Contingencies, is recorded to license fees and royalties as revenue from product sales is recognized. Revenue Recognition Product Sales, Net The Company’s net product sales consist of U.S. sales of NUPLAZID and are recognized when (i) persuasive evidence of an arrangement exists, (ii) delivery has occurred and title to the product and associated risk of loss has passed to the customer, (iii) the price is fixed or determinable, and (iv) collectability is reasonably assured. NUPLAZID was approved by the FDA on April 29, 2016 and the Company commenced shipments of NUPLAZID to specialty pharmacies (“SPs”) and specialty distributors (“SDs”) in late May 2016. Through September 30, 2016, the Company has determined it does not have the necessary volume of activity to reasonably estimate certain sales allowances at the time title and risk of loss transfers to the SP or SD. Accordingly, the price is not considered fixed or determinable at that time. Therefore, the Company recognizes revenue once the SP has filled a patient’s prescription for NUPLAZID or the SD sells NUPLAZID. This approach is frequently referred to as the “sell-through” revenue recognition model. Under the sell-through approach, revenue is recognized when the SP dispenses product to a patient based on the fulfillment of a prescription or the SD sells product to a government facility, long-term care pharmacy or in-patient hospital pharmacy. As of September 30, 2016, the Company had a deferred revenue balance of $1.9 million, net of distribution fees, related to NUPLAZID product sales. The Company recognizes revenue from product sales net of allowances for distribution fees, rebates, chargebacks, and co-payment assistance.

Net Loss Per Share	9 Months Ended
Net Loss Per Share	Sep. 30, 2016
Earnings Per Share [Abstract]
Net Loss Per Share	3. Net Loss Per Share Basic net loss per share is calculated by dividing the net loss by the weighted average number of common shares outstanding for the period, without consideration for common stock equivalents. Diluted net loss per share is computed by dividing the net loss by the weighted average number of common shares and common stock equivalents outstanding for the period determined using the treasury stock method. For purposes of this calculation, stock options, employee stock purchase rights, and warrants are considered to be common stock equivalents but are not included in the calculations of diluted net loss per share for the periods presented as their effect would be antidilutive. The Company incurred net losses for all periods presented and there were no reconciling items for potentially dilutive securities. More specifically, at September 30, 2016 and 2015, stock options, employee stock purchase rights, and warrants totaling approximately 14,463,000 shares and 12,309,000 shares, respectively, were excluded from the calculation of diluted net loss per share as their effect would have been anti-dilutive.

Stock-Based Compensation

9 Months Ended

Sep. 30, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

4. Stock-Based Compensation

The following table summarizes the total stock-based compensation expense included in the Company’s statements of operations for the periods presented (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2015		2016		2015
Cost of product sales	$	308	$	—	$	497	$	—
Research and development		4,319		3,938		13,495		9,139
Selling, general and administrative		9,382		5,327		25,855		22,153
	$	14,009	$	9,265	$	39,847	$	31,292

As of September 30, 2016, total unrecognized compensation cost related to stock options and purchase plan rights was approximately $134.9 million, which is expected to be recognized over a weighted-average period of 3.0 years.

During the three months ended March 31, 2016, the Company granted options to purchase an aggregate of 3,059,835 shares of its common stock in connection with annual option grants to eligible employees. These stock options vest over a four-year period from the date of grant and have a weighted average exercise price of $23.88 per share. Stock-based compensation expense for the nine months ended September 30, 2015 included a one-time $9.0 million charge related to the transition agreement with the Company’s former Chief Executive Officer in connection with his retirement from the Company in March 2015.

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

+ References + Details

Balance sheet Details

9 Months Ended

Sep. 30, 2016

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Balance Sheet Details

5. Balance Sheet Details

Inventory consisted of the following (in thousands):

	September 30, 2016		December 31, 2015
Finished goods	$	2,157	$	—
Raw material		2,144		—
	$	4,301	$	—

Accrued liabilities consisted of the following (in thousands):

	September 30, 2016		December 31, 2015
Accrued research and development services	$	9,866	$	8,805
Accrued compensation and benefits		11,921		5,722
Accrued consulting and professional fees		9,488		4,508
Other		3,170		1,195
	$	34,445	$	20,230

Investment Securities

9 Months Ended

Sep. 30, 2016

Investments Debt And Equity Securities [Abstract]

Investment Securities

6. Investment Securities

Investment securities, all classified as available-for-sale, consisted of the following (in thousands):

	September 30, 2016
	Amortized Cost		Unrealized Gains		Unrealized Losses			Estimated Fair Value
U.S. Treasury notes	$	53,947	$	32	$	—		$	53,979
Government sponsored enterprise securities		128,245		37		—			128,282
Corporate debt securities		68,664		—		(40	)		68,624
Commercial paper		183,802		493		—			184,295
	$	434,658	$	562	$	(40	)	$	435,180

	December 31, 2015
	Amortized Cost		Unrealized Gains		Unrealized Losses			Estimated Fair Value
U.S. Treasury notes	$	9,000	$	—	$	(1	)	$	8,999
Government sponsored enterprise securities		103,996		12		(13	)		103,995
	$	112,996	$	12	$	(14	)	$	112,994

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 September 30, 2016 and December 31, 2015. As of September 30, 2016 and December 31, 2015, all of the Company’s available-for-sale investment securities had contractual maturity dates of less than one year.

- Definition

The entire disclosure for investments in certain debt and equity securities.

+ References + Details

Fair Value Measurements

9 Months Ended

Sep. 30, 2016

Fair Value Disclosures [Abstract]

Fair Value Measurements

7. Fair Value Measurements

As of September 30, 2016, the Company held $586.4 million of cash equivalents and available-for-sale investment securities consisting of a money market fund, U.S. Treasury notes, and high quality, marketable debt instruments of corporations and government sponsored enterprises in accordance with the Company’s investment policy. The Company’s investment policy defines allowable investments and establishes guidelines relating to credit quality, diversification, and maturities of its investments to preserve principal and maintain liquidity. All investment securities have a credit rating of at least A3/A- or better, or P-1/A-1 or better, as determined by Moody’s Investors Service or Standard & Poor’s.

The Company’s cash equivalents and available-for-sale investment securities are classified within the fair value hierarchy as defined by authoritative guidance. The Company’s investment securities classified as Level 1 are valued using quoted market prices. The Company obtains the fair value of its Level 2 financial instruments from third party pricing services. The pricing services utilize industry standard valuation models whereby all significant inputs, including benchmark yields, reported trades, broker/dealer quotes, issuer spreads, bids, offers, or other market-related data, are observable. The Company validates the prices provided by the third-party pricing services by reviewing their pricing methods and matrices, and obtaining market values from other pricing sources. After completing the validation procedures, the Company did not adjust or override any fair value measurements provided by these pricing services as of September 30, 2016 and December 31, 2015.

The Company does not hold any securities classified as Level 3, which are securities valued using unobservable inputs. The Company has not transferred any investment securities between levels.

The fair value measurements of the Company’s cash equivalents and available-for-sale investment securities are identified in the following tables (in thousands):

			Fair Value Measurements at Reporting Date Using
	September 30, 2016		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Money market fund	$	93,769	$	93,769	$	—	$	—
U.S. Treasury notes		53,979		53,979		—		—
Government sponsored enterprise securities		151,764		—		151,764		—
Corporate debt securities		71,631		—		71,631		—
Commercial paper		215,264		—		215,264		—
	$	586,407	$	147,748	$	438,659	$	—

			Fair Value Measurements at Reporting Date Using
	December 31, 2015		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Money market fund	$	46,437	$	46,437	$	—	$	—
U.S. Treasury notes		8,999		8,999		—		—
Government sponsored enterprise securities		157,623		—		157,623		—
	$	213,059	$	55,436	$	157,623	$	—

- Definition

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

+ References + Details

Stockholders' Equity	9 Months Ended
Stockholders' Equity	Sep. 30, 2016
Equity [Abstract]
Stockholders' Equity	8. Stockholders’ Equity Public Offerings In August 2016, the Company raised net proceeds of approximately $215.9 million from the sale of 6,969,696 shares of its common stock in a follow-on public offering, including 909,090 shares sold pursuant to the exercise in full of the underwriters’ option to purchase additional shares. In January 2016, the Company raised net proceeds of approximately $281.6 million from the sale of 10,344,827 shares of its common stock in a follow-on public offering. In connection with the January 2016 offering, the Company entered into a registration rights agreement (the “Registration Rights Agreement”) with 667, L.P., Baker Brothers Life Sciences, L.P. and 14159, L.P. (the “Baker Entities”), all of which are existing stockholders of the Company and are affiliated with two of its directors, Julian C. Baker and Dr. Stephen R. Biggar. Under the Registration Rights Agreement, the Company agreed that, if the Baker Entities demand that the Company register their shares of its common stock, par value $0.0001 per share, for resale under the Securities Act of 1933, as amended (the “Securities Act”), the Company would be obligated to effect such registration. The Company’s registration obligations under the Registration Rights Agreement cover all shares of its common stock now held or later acquired by the Baker Entities (including approximately $75.0 million and $43.0 million of shares that the Baker Entities purchased at the public offering price in the January 2016 and August 2016 offerings, respectively), will continue in effect for up to 10 years, and include the Company’s obligation to facilitate certain underwritten public offerings of its common stock by the Baker Entities in the future. The Company has agreed to bear all expenses incurred by it in effecting any registration pursuant to the Registration Rights Agreement as well as the legal expenses of the Baker Entities of up to $50,000 per underwritten public offering effected pursuant to the Registration Rights Agreement. On April 1, 2016, pursuant to the Registration Rights Agreement, the Company filed a registration statement covering all shares owned by the Baker Entities as of March 31, 2016. Settlement Agreement Proceeds In April 2016, the Company received a payment of $14.3 million pursuant to a settlement agreement with prior 10% stockholders who sold shares of the Company’s stock in 2013 that may have resulted in short-swing profits by the stockholders pursuant to Section 16(b) of the Securities Exchange Act of 1934, as amended. The Company recognized these proceeds as a capital contribution from stockholders and reflected a corresponding increase to additional paid-in capital.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

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-Name Accounting Standards Codification
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-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Preferred Stock
-URI http://asc.fasb.org/extlink&oid=6521494

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 16: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21564-112644

+ Details

Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 30, 2016
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. Commitments and Contingencies Royalty Payments Pursuant to the terms of its 2006 license agreement with the Ipsen Group, the Company is required to make royalty payments of two percent of net sales of NUPLAZID. Corporate Credit Card Program In connection with the Company’s credit card program, the Company established a letter of credit in April 2016 for $2.0 million, which has automatic annual extensions and is fully secured by restricted cash. Legal Proceedings In March 2015, following the Company’s announcement of the update to the timing of its planned NDA submission to the FDA for NUPLAZID and the subsequent decline of the price of its common stock, two putative securities class action complaints (captioned Rihn v. ACADIA Pharmaceuticals Inc., Case No. 15-cv-0575-BTM-DHB, and Wright v. ACADIA Pharmaceuticals Inc., Case No. 15-cv-0593- BTM-DHB) were filed in the U.S. District Court for the Southern District of California (the “Court”) against the Company and certain of its current and former officers. The complaints generally alleged that the defendants violated Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 by making materially false and misleading statements regarding the timing of the Company’s planned NDA submission to the FDA for NUPLAZID, thereby artificially inflating the price of its common stock. The complaints sought unspecified monetary damages and other relief. On April 10 and June 1, 2015, the Court entered orders deferring the defendants’ response to the Rihn and Wright complaints until after the Court appointed a lead plaintiff and assigned lead counsel. On May 12, 2015, several putative stockholders filed separate motions to consolidate the two actions and be appointed lead plaintiff. On September 8, 2015, the Court issued an order consolidating the two actions, appointing lead plaintiff, and assigning lead counsel. On November 16, 2015, lead plaintiff filed a consolidated complaint with the Court which, like the prior complaints, accused the defendants of making materially false and misleading statements regarding the anticipated timing of the Company’s planned NDA submission to the FDA for NUPLAZID. On January 15, 2016, the defendants filed a motion to dismiss the consolidated complaint. On September 19, 2016, the Court issued an order denying the motion to dismiss the consolidated complaint. On October 18, 2016, the Company filed a motion for reconsideration of the Court’s order denying the motion to dismiss. On October 21, 2016, the Company filed its answer to the consolidated complaint. The hearing on the Company’s motion for reconsideration is scheduled for December 16, 2016. The Company has assessed such legal proceedings, and given the unpredictability inherent in litigation, the Company cannot predict the outcome of these matters. At this time, the Company is unable to estimate possible losses or ranges of losses that may result from such legal proceedings, and it has not accrued any amounts in connection with such legal proceedings other than ongoing attorneys’ fees.

Recent Accounting Pronouncements	9 Months Ended
Recent Accounting Pronouncements	Sep. 30, 2016
New Accounting Pronouncements And Changes In Accounting Principles [Abstract]
Recent Accounting Pronouncements	10. Recent Accounting Pronouncements In June 2016, the Financial Accounting Standards Board (“FASB”) issued authoritative guidance related to accounting for credit losses on financial instruments that changes the impairment model for most financial assets and certain other instruments. For trade receivables and other instruments, entities will be required to use a new forward-looking expected loss model that generally will result in the earlier recognition of allowances for losses. For available-for-sale debt securities with unrealized losses, the losses will be recognized as allowances rather than as reductions in the amortized cost of the securities. This guidance is effective for annual reporting periods beginning after December 15, 2019, including interim periods within those years, with early adoption permitted only as of annual reporting periods beginning after December 15, 2018. The Company is currently evaluating the impact of the adoption of this guidance on the Company’s consolidated financial statements. In March, April, and May 2016, the FASB issued updates to its authoritative guidance for revenue from contracts with customers. The updates clarify certain aspects of the revenue guidance, including but not limited to, the implementation guidance on principal versus agent considerations, the licensing implementation guidance, identification of performance obligations, assessment of the collectability criterion, presentation of sales taxes and other similar taxes, and measurement of noncash consideration. The authoritative guidance for revenue from contracts with customers to which these updates apply is effective for annual reporting periods beginning after December 15, 2017, with early adoption permitted only as of annual reporting periods beginning after December 15, 2016. Companies may use either a full retrospective or a modified retrospective approach to adopt this guidance. The Company is continuing to evaluate which transition approach to use and its impact, if any, on its consolidated financial statements. In March 2016, the FASB issued authoritative guidance related to accounting for employee share-based compensation which is intended to simplify several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, classification on the statement of cash flows, and accounting for forfeitures. This guidance is effective for annual reporting periods beginning after December 15, 2016, including interim periods within those years. The Company is currently evaluating the impact of the adoption of this guidance on the Company’s consolidated financial statements. In February 2016, the FASB issued authoritative guidance related to accounting for leases. This accounting guidance will require a lessee to recognize a lease liability and a right-of-use asset for all leases with lease terms of more than 12 months. This guidance is effective for annual reporting periods beginning after December 15, 2018, including interim periods within those years, and early adoption is permitted. The Company is currently evaluating the impact of the adoption of this guidance on the Company’s consolidated financial statements. In August 2014, the FASB issued authoritative accounting guidance related to an entity’s ability to continue as a going concern. This guidance explicitly requires management to assess an entity’s ability to continue as a going concern, and to provide related footnote disclosures in certain circumstances. The new standard is effective for annual reporting periods ending after December 15, 2016, and for annual periods and interim periods thereafter, with early adoption permitted. The Company early adopted this guidance in the first quarter of 2016 with no impact to its consolidated financial statements or related disclosures.

Basis of Presentation and Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2016
Accounting Policies [Abstract]
Accounts Receivable	Accounts Receivable Accounts receivable are recorded net of customer allowances for prompt payment discounts, distribution fees, chargebacks, and 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, the Company has determined that an allowance for doubtful accounts is not required.
Inventory	Inventory Inventory, consisting of raw material and finished goods, is stated at the lower of cost or estimated net realizable value. The Company uses a combination of standard and actual costing methodologies to determine the cost basis for its inventories which approximates actual costs. Inventory is valued on a first-in, first-out basis and includes third-party manufacturing costs, freight, and indirect overhead 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 NUPLAZID, all costs related to the manufacturing of NUPLAZID were charged to research and development expense in the period incurred. At September 30, 2016 the Company had an immaterial amount of zero cost raw material that was available for use in the manufacturing of commercial product. The Company provides reserves for potentially excess, dated or obsolete inventory based on an analysis of forecasted demand compared to quantities on hand and any firm purchase orders, as well as product shelf life. To date, the Company has determined that a reserve for potentially excess, dated or obsolete inventory is not required.
License Fees and Royalties	License Fees and Royalties The Company expenses amounts paid to acquire licenses associated with products under development when the ultimate recoverability of the amounts paid is uncertain and the technology has no alternative future use when acquired. Acquisitions of technology licenses are charged to expense or capitalized based upon management’s assessment regarding the ultimate recoverability of the amounts paid and the potential for alternative future use. The Company has determined that technological feasibility for its product candidates is reached when the requisite regulatory approvals are obtained to make the product available for sale. In connection with the FDA approval of NUPLAZID in April 2016, the Company made a one-time milestone payment of $8.0 million pursuant to its 2006 license agreement with the Ipsen Group in which the Company licensed certain intellectual property rights that complement its patent portfolio for its serotonin platform, including NUPLAZID. The Company has capitalized the $8.0 million payment as an intangible asset and is amortizing the asset on a straight-line basis over the estimated useful life of the licensed patents through the second half of 2021. The Company recorded amortization expense related to its intangible asset of $369,000 and $615,000 for the three and nine months ended September 30, 2016, respectively. As of September 30, 2016, estimated future amortization expense related to the Company’s intangible asset was $369,000 for the remainder of 2016, $1.5 million for each of 2017, 2018, 2019, and 2020, and $1.1 million thereafter. Royalty expense incurred in connection with the Company’s license agreement with the Ipsen Group, as disclosed in Note 9, Commitments and Contingencies, is recorded to license fees and royalties as revenue from product sales is recognized.
Revenue Recognition	Revenue Recognition Product Sales, Net The Company’s net product sales consist of U.S. sales of NUPLAZID and are recognized when (i) persuasive evidence of an arrangement exists, (ii) delivery has occurred and title to the product and associated risk of loss has passed to the customer, (iii) the price is fixed or determinable, and (iv) collectability is reasonably assured. NUPLAZID was approved by the FDA on April 29, 2016 and the Company commenced shipments of NUPLAZID to specialty pharmacies (“SPs”) and specialty distributors (“SDs”) in late May 2016. Through September 30, 2016, the Company has determined it does not have the necessary volume of activity to reasonably estimate certain sales allowances at the time title and risk of loss transfers to the SP or SD. Accordingly, the price is not considered fixed or determinable at that time. Therefore, the Company recognizes revenue once the SP has filled a patient’s prescription for NUPLAZID or the SD sells NUPLAZID. This approach is frequently referred to as the “sell-through” revenue recognition model. Under the sell-through approach, revenue is recognized when the SP dispenses product to a patient based on the fulfillment of a prescription or the SD sells product to a government facility, long-term care pharmacy or in-patient hospital pharmacy. As of September 30, 2016, the Company had a deferred revenue balance of $1.9 million, net of distribution fees, related to NUPLAZID product sales. The Company recognizes revenue from product sales net of allowances for distribution fees, rebates, chargebacks, and co-payment assistance.

- Definition

Disclosure of accounting policy for trade and other accounts receivable, and finance, loan and lease receivables, including those classified as held for investment and held for sale. This disclosure may include (1) the basis at which such receivables are carried in the entity's statements of financial position (2) how the level of the valuation allowance for receivables is determined (3) when impairments, charge-offs or recoveries are recognized for such receivables (4) the treatment of origination fees and costs, including the amortization method for net deferred fees or costs (5) the treatment of any premiums or discounts or unearned income (6) the entity's income recognition policies for such receivables, including those that are impaired, past due or placed on nonaccrual status and (7) the treatment of foreclosures or repossessions (8) the nature and amount of any guarantees to repurchase receivables.

+ References + Details

Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock-based Compensation Expense Included in Statements of Operations

The following table summarizes the total stock-based compensation expense included in the Company’s statements of operations for the periods presented (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2015		2016		2015
Cost of product sales	$	308	$	—	$	497	$	—
Research and development		4,319		3,938		13,495		9,139
Selling, general and administrative		9,382		5,327		25,855		22,153
	$	14,009	$	9,265	$	39,847	$	31,292

Balance Sheet Details (Tables)

9 Months Ended

Sep. 30, 2016

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Schedule of Inventory

Inventory consisted of the following (in thousands):

	September 30, 2016		December 31, 2015
Finished goods	$	2,157	$	—
Raw material		2,144		—
	$	4,301	$	—

Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):

	September 30, 2016		December 31, 2015
Accrued research and development services	$	9,866	$	8,805
Accrued compensation and benefits		11,921		5,722
Accrued consulting and professional fees		9,488		4,508
Other		3,170		1,195
	$	34,445	$	20,230

Investment Securities (Tables)

9 Months Ended

Sep. 30, 2016

Investments Debt And Equity Securities [Abstract]

Investment Securities, All Classified as Available-for-Sale

Investment securities, all classified as available-for-sale, consisted of the following (in thousands):

	September 30, 2016
	Amortized Cost		Unrealized Gains		Unrealized Losses			Estimated Fair Value
U.S. Treasury notes	$	53,947	$	32	$	—		$	53,979
Government sponsored enterprise securities		128,245		37		—			128,282
Corporate debt securities		68,664		—		(40	)		68,624
Commercial paper		183,802		493		—			184,295
	$	434,658	$	562	$	(40	)	$	435,180

	December 31, 2015
	Amortized Cost		Unrealized Gains		Unrealized Losses			Estimated Fair Value
U.S. Treasury notes	$	9,000	$	—	$	(1	)	$	8,999
Government sponsored enterprise securities		103,996		12		(13	)		103,995
	$	112,996	$	12	$	(14	)	$	112,994

Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2016

Fair Value Disclosures [Abstract]

Fair Value Measurements of Cash Equivalents and Available-For-Sale Investment Securities

The fair value measurements of the Company’s cash equivalents and available-for-sale investment securities are identified in the following tables (in thousands):

			Fair Value Measurements at Reporting Date Using
	September 30, 2016		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Money market fund	$	93,769	$	93,769	$	—	$	—
U.S. Treasury notes		53,979		53,979		—		—
Government sponsored enterprise securities		151,764		—		151,764		—
Corporate debt securities		71,631		—		71,631		—
Commercial paper		215,264		—		215,264		—
	$	586,407	$	147,748	$	438,659	$	—

			Fair Value Measurements at Reporting Date Using
	December 31, 2015		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Money market fund	$	46,437	$	46,437	$	—	$	—
U.S. Treasury notes		8,999		8,999		—		—
Government sponsored enterprise securities		157,623		—		157,623		—
	$	213,059	$	55,436	$	157,623	$	—

Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended	9 Months Ended
	Apr. 30, 2016	Sep. 30, 2016	Sep. 30, 2016
Accounting Policies [Abstract]
One-time contingent regulatory milestone payment pursuant to agreement with Ipsen Group	$ 8,000,000
Finite-lived intangible assets, net	$ 8,000,000
Amortization of intangible assets		$ 369,000	$ 615,000
Estimated future amortization expense, remainder of 2016		369,000	369,000
Estimated future amortization expense, 2017		1,500,000	1,500,000
Estimated future amortization expense, 2018		1,500,000	1,500,000
Estimated future amortization expense, 2019		1,500,000	1,500,000
Estimated future amortization expense, 2020		1,500,000	1,500,000
Estimated future amortization expense, thereafter		1,100,000	1,100,000
Deferred revenue, net of distribution fees		$ 1,876,000	$ 1,876,000

Net Loss Per Share - Additional Information (Detail) - shares	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share [Abstract]
Anti-dilutive securities excluded from the calculation of diluted net loss per share	14,463,000	12,309,000

Stock-Based Compensation - Summary of Stock-based Compensation Expense Included in Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 14,009	$ 9,265	$ 39,847	$ 31,292
Cost of product sales
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	308		497
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	4,319	3,938	13,495	9,139
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 9,382	$ 5,327	$ 25,855	$ 22,153

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation costs	$ 134,900			$ 134,900
Weighted average period cost expected to be recognized				3 years
Stock-based compensation expense	$ 14,009		$ 9,265	$ 39,847	$ 31,292
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted during period in connection with annual option grant		3,059,835
Options vesting period		4 years
Options granted weighted average exercise price in connection with annual option grant		$ 23.88
Chief Executive Officer
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense				$ 9,000

Balance Sheet Details - Schedule of Inventory (Detail) $ in Thousands	Sep. 30, 2016 USD ($)
Inventory Disclosure [Abstract]
Finished goods	$ 2,157
Raw material	2,144
Inventory	$ 4,301

Balance Sheet Details - Accrued Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Payables And Accruals [Abstract]
Accrued research and development services	$ 9,866	$ 8,805
Accrued compensation and benefits	11,921	5,722
Accrued consulting and professional fees	9,488	4,508
Other	3,170	1,195
Accrued liabilities	$ 34,445	$ 20,230

Investment Securities, All Classified as Available-for-Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 434,658	$ 112,996
Unrealized Gains	562	12
Unrealized Losses	(40)	(14)
Estimated Fair Value	435,180	112,994
U.S. Treasury notes
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	53,947	9,000
Unrealized Gains	32
Unrealized Losses		(1)
Estimated Fair Value	53,979	8,999
Government sponsored enterprise securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	128,245	103,996
Unrealized Gains	37	12
Unrealized Losses		(13)
Estimated Fair Value	128,282	$ 103,995
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	68,664
Unrealized Losses	(40)
Estimated Fair Value	68,624
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	183,802
Unrealized Gains	493
Estimated Fair Value	$ 184,295

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Investment, fair value disclosure	$ 586,407	$ 213,059

- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(12))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Trading Securities
-URI http://asc.fasb.org/extlink&oid=6526789

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(5))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 35
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=27723805&loc=d3e24584-111560

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Available-for-Sale Securities
-URI http://asc.fasb.org/extlink&oid=6505594

+ Details

Fair Value Measurements of Cash Equivalents and Available-For-Sale Investment Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value disclosure	$ 586,407	$ 213,059
Money market fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value disclosure	93,769	46,437
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value disclosure	147,748	55,436
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Money market fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value disclosure	93,769	46,437
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value disclosure	438,659	157,623
U.S. Treasury notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value disclosure	53,979	8,999
U.S. Treasury notes \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value disclosure	53,979	8,999
Government sponsored enterprise securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value disclosure	151,764	157,623
Government sponsored enterprise securities \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value disclosure	151,764	$ 157,623
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value disclosure	71,631
Corporate debt securities \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value disclosure	71,631
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value disclosure	215,264
Commercial paper \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value disclosure	$ 215,264

- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

+ Details

Stockholders' Equity - Additional Information (Detail) - USD ($)	1 Months Ended			9 Months Ended
	Aug. 31, 2016	Apr. 30, 2016	Jan. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Class Of Stock [Line Items]
Net proceeds from sale of common stock	$ 215,900,000		$ 281,600,000	$ 515,506,000	$ 5,170,000
Share of common stock issued	6,969,696		10,344,827
Common stock, par value				$ 0.0001		$ 0.0001
Value of shares purchased by Baker Entities in public offerings				$ 12,000		$ 10,000
Payment received from stockholder pursuant to a settlement agreement related to short-swing profits		$ 14,300,000		$ 14,320,000
Prior stockholders percentage of equity holding		10.00%
Option To Purchase Additional Shares
Class Of Stock [Line Items]
Share of common stock issued	909,090
Registration Rights Agreement
Class Of Stock [Line Items]
Common stock, par value			$ 0.0001
Expiration period			10 years
Maximum amount of expense agreed to bear under the agreement			$ 50,000
Registration Rights Agreement \| Baker Brothers Life Sciences L.P.
Class Of Stock [Line Items]
Value of shares purchased by Baker Entities in public offerings	$ 43,000,000		$ 75,000,000

Commitments and Contingencies - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2016	Apr. 30, 2016	Dec. 31, 2015
Other Commitments [Line Items]
Restricted cash	$ 2,375,000		$ 375,000
Corporate Credit Card Program \| Letter of Credit [Member]
Other Commitments [Line Items]
Restricted cash		$ 2,000,000
Maximum
Other Commitments [Line Items]
Percentage of royalty payments obligation on net product sales	2.00%