Portola Pharmaceuticals (PTLA) 10-Q 6 Nov 13 2013 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2013	Oct. 31, 2013
Document Information [Line Items]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-13	'
Document Fiscal Year Focus	'2013	'
Document Fiscal Period Focus	'Q3	'
Trading Symbol	'PTLA	'
Entity Registrant Name	'PORTOLA PHARMACEUTICALS INC	'
Entity Central Index Key	'0001269021	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Non-accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	39,709,658

Condensed_Balance_Sheets

Condensed Balance Sheets (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
CURRENT ASSETS:	'	'
Cash and cash equivalents	$58,710	$53,613
Short-term investments	116,066	77,656
Receivables from collaborations	227	662
Prepaid expenses and other current assets	3,669	2,982
Total current assets	178,672	134,913
Property and equipment, net	2,428	2,861
Long-term investments	44,151	6,115
Other assets	116	2,112
TOTAL ASSETS	225,367	146,001
CURRENT LIABILITIES:	'	'
Accounts payable	1,517	4,840
Accrued compensation and employee benefits	1,863	1,860
Accrued and other liabilities	15,960	7,399
Deferred revenue – current portion	3,930	4,042
Convertible preferred stock warrant liability	'	683
Total current liabilities	23,270	18,824
Deferred revenue – noncurrent portion	3,337	'
Other long-term liabilities	811	1,466
TOTAL LIABILITIES	27,418	20,290
Commitments and contingencies	'	'
Convertible preferred stock, $0.001 par value. 0 and 243,258,300 shares authorized at September 30, 2013 and December 31, 2012; 0 shares and 24,026,797 shares issued and outstanding at September 30, 2013 and December 31, 2012	'	317,280
STOCKHOLDERS’ EQUITY (DEFICIT):	'	'
Preferred stock, $0.001 par value. 5,000,000 shares authorized at September 30, 2013; 0 issued and outstanding at September 30, 2013; 0 authorized, issued or outstanding at December 31, 2012	'	'
Common stock, $0.001 par value. 100,000,000 and 300,000,000 shares authorized; 35,229,352 and 1,385,508 shares issued and outstanding at September 30, 2013 and December 31, 2012	35	1
Additional paid-in capital	458,460	10,717
Accumulated deficit	-260,610	-202,320
Accumulated other comprehensive income (loss)	64	33
Total stockholders’ equity (deficit)	197,949	-191,569
TOTAL LIABILITIES, CONVERTIBLE PREFERRED STOCK, AND STOCKHOLDERS’ EQUITY	$225,367	$146,001

Condensed_Balance_Sheets_Paren

Condensed Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Convertible preferred stock, par value	$0.00	$0.00
Convertible preferred stock, shares authorized	0	243,258,300
Convertible preferred stock, shares issued	0	24,026,797
Convertible preferred stock, shares outstanding	0	24,026,797
Preferred stock, par value	$0.00	$0.00
Preferred stock, shares authorized	5,000,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	100,000,000	300,000,000
Common stock, shares issued	35,229,352	1,385,508
Common stock, shares outstanding	35,229,352	1,385,508

Condensed_Statements_of_Operat

Condensed Statements of Operations (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Collaboration and license revenue	$2,766	$738	$8,474	$70,084
Operating expenses:	'	'	'	'
Research and development	18,088	9,954	56,642	36,004
General and administrative	3,907	2,879	10,654	8,744
Total operating expenses	21,995	12,833	67,296	44,748
Income (loss) from operations	-19,229	-12,095	-58,822	25,336
Interest and other income (expense), net	679	607	532	-188
Net income (loss)	-18,550	-11,488	-58,290	25,148
Net income (loss) attributable to common stockholders:	'	'	'	'
Basic	-18,550	-11,488	-58,290	322
Diluted	($18,550)	($11,488)	($58,290)	$462
Shares used to compute net income (loss) per share attributable to common stockholders:	'	'	'	'
Basic	35,200,761	1,370,190	17,218,475	1,342,919
Diluted	35,200,761	1,370,190	17,218,475	1,976,618
Net income (loss) per share attributable to common stockholders:	'	'	'	'
Basic	($0.53)	($8.38)	($3.39)	$0.24
Diluted	($0.53)	($8.38)	($3.39)	$0.23

Condensed_Statements_of_Compre

Condensed Statements of Comprehensive Income (Loss) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Net income (loss)	($18,550)	($11,488)	($58,290)	$25,148
Other comprehensive income:	'	'	'	'
Unrealized gain on available-for-sale securities, net of tax	100	10	31	56
Total comprehensive income (loss)	($18,450)	($11,478)	($58,259)	$25,204

Condensed_Statements_of_Cash_F

Condensed Statements of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Operating activities	'	'
Net income (loss)	($58,290)	$25,148
Adjustments to reconcile net income (loss) to cash used in operating activities:	'	'
Depreciation and amortization	1,015	1,053
Amortization of premium on investment securities	1,523	1,018
Stock-based compensation expense	3,457	2,017
Revaluation of convertible preferred stock warrant liability	-24	-144
Unrealized (gain) loss on foreign currency forward contracts	-97	450
Changes in operating assets and liabilities:	'	'
Receivables from collaborations	435	-2,347
Prepaid expenses and other current assets	-540	-2,155
Other assets	361	-368
Accounts payable	-3,323	711
Accrued compensation and employee benefits	3	-918
Accrued and other liabilities	10,004	1,299
Deferred revenue	3,225	-69,468
Other long-term liabilities	-655	-620
Net cash used in operating activities	-42,906	-44,324
Investing activities	'	'
Purchases of property and equipment	-582	-362
Purchases of investments	-152,793	-133,073
Proceeds from sales of investments	6,644	42,767
Proceeds from maturities of investments	68,211	18,637
Net cash used in investing activities	-78,520	-72,031
Financing activities	'	'
Proceeds from initial public offering, net of underwriters discount	131,026	'
Payment of initial public offering costs	-5,025	'
Proceeds from issuance of common stock, including early exercise of stock options	522	292
Net cash provided by financing activities	126,523	292
Net increase (decrease) in cash and cash equivalents	5,097	-116,063
Cash and cash equivalents at beginning of period	53,613	170,323
Cash and cash equivalents at end of period	$58,710	$54,350

Organization

Organization	9 Months Ended
	Sep. 30, 2013
Organization	'
	1. Organization
	Portola Pharmaceuticals, Inc. (the “Company” or “we” or “our” or “us”) is a biopharmaceutical company focused on the development and commercialization of novel therapeutics in the areas of thrombosis, other hematologic disorders and inflammation for patients who currently have limited or no approved treatment options. We were incorporated in September 2003 in Delaware. Our headquarters and operations are located in South San Francisco, California and we operate in one segment.
	Our two lead programs address the area of thrombosis, or blood clots. Our lead compound Betrixaban is a novel oral once-daily inhibitor of Factor Xa in Phase 3 development for extended duration prophylaxis, or preventive treatment, of a form of thrombosis known as venous thromboembolism, in acute medically ill patients. Our second lead development candidate (pINN) Andexanet alfa, formerly PRT4445, is a recombinant protein designed to reverse the anticoagulant activity in patients treated with a Factor Xa inhibitor who suffer an uncontrolled bleeding episode or undergo emergency surgery. Our third product candidate, PRT2070, is an orally available kinase inhibitor being developed for hematologic, or blood, cancers and inflammatory disorders. Our fourth program, PRT2607 and other selective Syk inhibitors, is being developed in partnership with Biogen Idec Inc.
	Initial Public Offering
	In May 2013, we closed our initial public offering (“IPO”) of 9,686,171 shares of our common stock, which included 1,263,413 shares of common stock issued pursuant to the over-allotment option granted to our underwriters. The public offering price of the shares sold in the offering was $14.50 per share. The total proceeds from the offering to us, net of underwriting discounts and commissions of approximately $9.4 million, were approximately $131.0 million. After deducting offering expenses payable by us of approximately $5.2 million, net proceeds to us were $125.8 million. Upon the closing of the IPO, all shares of convertible preferred stock then outstanding converted into 24,026,797 shares of common stock. In addition, all of our convertible preferred stock warrants were converted into warrants to purchase common stock.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2013
Summary of Significant Accounting Policies	'
	2. Summary of Significant Accounting Policies
	Basis of Presentation
	The accompanying unaudited condensed financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”), and following the requirements of the Securities and Exchange Commission (“SEC”) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These financial statements have been prepared on the same basis as the Company’s annual financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, that are necessary for a fair statement of the Company’s financial information. The results of operations for the nine months ended September 30, 2013 are not necessarily indicative of the results to be expected for the year ending December 31, 2013. The condensed balance sheet as of December 31, 2012 has been derived from audited financial statements at that date but does not include all of the information required by U.S. GAAP for complete financial statements.
	The accompanying condensed financial statements and related financial information should be read in conjunction with the audited financial statements and the related notes thereto for the year ended December 31, 2012 included in the Company’s Prospectus filed pursuant to Rule 424(b)(4) as filed on May 21, 2013 with the SEC.
	Reverse Stock Split
	On May 17, 2013, the Company effected a 1-for-10 reverse split of our preferred stock and common stock. Upon the effectiveness of the reverse stock split every 10 shares of outstanding preferred stock and common stock was decreased to one share of preferred stock or common stock, as applicable, the number of shares of common stock into which each outstanding option to purchase common stock is exercisable was proportionately decreased on a 1-for-10 basis, and the exercise price of each outstanding option to purchase common stock was proportionately increased on a 1-for-10 basis. All the shares numbers, share prices and exercise prices have been adjusted within the condensed financial statements, on a retroactive basis, to reflect the 1-for-10 reverse stock split.
	Use of Estimates
	The preparation of condensed financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities and the reported amounts of revenues and expenses in the condensed financial statements and the accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to revenue recognition, clinical trial accruals, fair value of assets and liabilities, income taxes and stock-based compensation. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results may differ from those estimates.
	Cash and Cash Equivalents
	Cash and cash equivalents consist of cash and other highly liquid investments with original maturities of three months or less from the date of purchase.
	Investments
	All investments have been classified as “available-for-sale” and are carried at estimated fair value as determined based upon quoted market prices or pricing models for similar securities. Management determines the appropriate classification of its investments in debt securities at the time of purchase and reevaluates such designation as of each balance sheet date. Unrealized gains and losses are excluded from earnings and were reported as a component of accumulated comprehensive income. Realized gains and losses and declines in fair value judged to be other than temporary, if any, on available-for-sale securities are included in interest and other income (expense), net. The cost of securities sold is based on the specific-identification method. Interest on marketable securities is included in interest and other income (expense), net.
	Customer Concentration
	Customers whose collaborative research and development revenue accounted for 10% or more of total revenues were as follows:
		Three Months Ended September 30,					Nine Months Ended September 30,
			2013		2012			2013		2012
	Novartis AG		—		100	%		—		100	%
	Bristol-Myers Squibb Company and Pfizer Inc.		28	%	—			46	%	—
	Bayer Pharma, AG and Janssen Pharmaceuticals, Inc.		37	%	—			41	%	—
	Daiichi Sankyo, Inc.		32	%	—			12	%	—
	Deferred Offering Costs
	Deferred offering costs, which primarily consist of direct incremental legal, accounting and printing fees incurred in the preparation of the IPO, were capitalized. The deferred offering costs were offset against IPO proceeds upon completion of the offering in May 2013. As of December 31, 2012, $1.6 million of deferred offering costs were capitalized in other assets on the balance sheets. There were no remaining amounts deferred at September 30, 2013 pertaining to the IPO.
	Revenue Recognition
	We generate revenue from collaboration and license agreements for the development and commercialization of our products. Collaboration and license agreements may include non-refundable upfront license fees, partial or complete reimbursement of research and development costs, contingent consideration payments based on the achievement of defined collaboration objectives and royalties on sales of commercialized products. Our performance obligations under our collaborations include the transfer of intellectual property rights (licenses), obligations to provide research and development services and related materials and obligations to participate on certain development and/or commercialization committees with the collaborators.
	Payments that are contingent upon achievement of a substantive milestone are recognized in their entirety in the period in which the milestone is achieved. Milestones are defined as an event that can only be achieved based on our performance and there is substantive uncertainty about whether the event will be achieved at the inception of the arrangement. Events that are contingent only on the passage of time or only on counterparty performance are not considered milestones subject to this guidance. Further, the amounts received must relate solely to prior performance, be reasonable relative to all of the deliverables and payment terms within the agreement and commensurate with our performance to achieve the milestone after commencement of the agreement.
	Amounts from sales of licenses are recognized as revenue, as licensing of intellectual property is one of our principal or major ongoing activities. Amounts received as funding of research and development activities are recognized as revenue if the collaboration arrangement involves the sale of our research or development services at amounts that exceed our cost. However, such funding is recognized as a reduction in research and development expense when we engage in a research and development project jointly with another entity, with both entities participating in project activities and sharing costs and potential benefits of the arrangement.
	Amounts related to research and development funding are recognized as the related services or activities are performed, in accordance with the contract terms. Payments may be made to or by us based on the number of full-time equivalent researchers assigned to the collaboration project and the related research and development expenses incurred.
	Foreign Currency Transactions and Hedging
	We have transactions denominated in foreign currencies, primarily the Euro, and, as a result, are exposed to changes in foreign currency exchange rates. We manage a portion of these cash flow exposures through the purchase of Euros and the use of foreign currency forward contracts. Our foreign currency forward contracts are not designated as hedges for accounting purposes. Gains or losses on foreign currency forward contracts are intended to offset gains or losses on the underlying net exposures in an effort to reduce the earnings and cash flow volatility resulting from fluctuating foreign currency exchange rates. Foreign currencies and our foreign currency forward contracts are marked to market at the end of each period and recorded as gains and losses in the condensed statements of operations.
	Our foreign exchange forward contracts expose us to credit risk to the extent that the counterparty, a major financial institution, is unable to meet the terms of the agreement. Our management does not expect material losses as a result of defaults by the counterparty.
	Net Income (Loss) per Share Attributable to Common Stockholders
	Basic and diluted net income (loss) per share attributable to common stockholders is calculated in conformity with the two-class method required for companies with participating securities. Under the two-class method, in periods when we have net income, basic net income attributable to common stockholders is determined by allocating undistributed earnings, calculated as net income less current period convertible preferred stock noncumulative dividends, between the common stock and the convertible preferred stock. In computing diluted net income attributable to common stockholders, undistributed earnings are re-allocated to reflect the potential impact of dilutive securities. Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding for the period. The diluted net income per share attributable to common stockholders is computed by giving effect to all potential dilutive common stock equivalents outstanding for the period. In periods when we have incurred a net loss, convertible preferred stock, options and warrants to purchase common stock and convertible preferred stock warrants are considered common stock equivalents but have been excluded from the calculation of diluted net loss per share attributable to common stockholders as their effect is antidilutive.

Fair_Value_Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2013
Fair Value Measurements	'
	3. Fair Value Measurements
	Financial assets and liabilities are recorded at fair value. The carrying amounts of certain of our financial instruments, including cash and cash equivalents, investments, receivables and accounts payable, approximate their fair value due to their short maturities. The accounting guidance for fair value provides a framework for measuring fair value, clarifies the definition of fair value, and expands disclosures regarding fair value measurements. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the reporting date. The accounting guidance establishes a three-tiered hierarchy, which prioritizes the inputs used in the valuation methodologies in measuring fair value as follows:
	Level 1 – Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date.
	Level 2 – Inputs (other than quoted market prices included in Level 1) are either directly or indirectly observable for the asset or liability through correlation with market data at the measurement date and for the duration of the instrument’s anticipated life.
	Level 3 – Inputs reflect management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. Consideration is given to the risk inherent in the valuation technique and the risk inherent in the inputs to the model.
	The following table sets forth the fair value of our financial assets and liabilities, allocated into Level 1, Level 2, and Level 3, that was measured on a recurring basis (in thousands):
		September 30, 2013
		Level 1				Level 2				Level 3			Total
	Financial Assets:
	Money market funds	$		54,930		$	—			$		—	$	54,930
	Corporate notes and commercial paper			—			103,065					—		103,065
	U.S. government agency securities			—			57,150					—		57,150
	Foreign currency forward contracts			—			266					—		266
	Total financial assets	$		54,930		$	160,481			$		—	$	215,411
		December 31, 2012
		Level 1				Level 2				Level 3			Total
	Financial Assets:
	Money market funds	$		43,303		$	—			$		—	$	43,303
	Corporate notes and commercial paper			—			64,425					—		64,425
	U.S. government agency securities			—			19,346					—		19,346
	Foreign currency forward contracts			—			51					—		51
	Total financial assets	$		43,303		$	83,822			$		—	$	127,125
	Financial Liabilities:
	Convertible preferred stock warrant liability	$		—		$	—			$		683	$	683
	We have elected to use the income approach to value the derivatives (foreign currency forward contracts), using observable Level 2 market expectations at the measurement date and standard valuation techniques to convert future amounts to a single present amount assuming that participants are motivated, but not compelled to transact. Level 2 inputs for the valuations are limited to quoted prices for similar assets or liabilities in active markets and inputs other than quoted prices that are observable for the asset or liability (specifically foreign currency spot and forward rates, and credit risk at commonly quoted intervals). Mid-market pricing is used as a practical expedient for fair value measurements. The fair value measurement of any asset or liability must reflect the non-performance risk of the entity and the counterparty to the transaction. Therefore, the impact of the counterparty’s creditworthiness, when in an asset position, and our creditworthiness, when in a liability position, has also been factored into the fair value measurement of the derivative instruments and did not have a material impact on the fair value of these derivative instruments. Both we and the counterparty are expected to continue to perform under the contractual terms of the instruments. There were no transfers between Level 1 and Level 2 during the periods presented.
	Our convertible preferred stock warrant liability was classified as a Level 3 liability. The fair values of the outstanding convertible preferred stock warrants were measured using the Black-Scholes option-pricing model. Inputs used to determine estimated fair value included the estimated fair value of the underlying convertible preferred stock at the valuation measurement date, the remaining contractual term of the warrants, risk-free interest rates, expected dividends and estimated volatility. The significant unobservable input used in the fair value measurement of the convertible preferred stock warrant liability was the fair value of the underlying convertible preferred stock at the valuation remeasurement date. Generally, increases (decreases) in the fair value of the underlying convertible preferred stock would result in a directionally similar impact to the fair value measurement. The preferred stock warrants were converted to common stock warrants upon the completion of the IPO and are no longer subject to remeasurement.
	The following table sets forth a summary of the changes in the estimated fair value of our convertible preferred stock warrants, which were measured at fair value on a recurring basis until their conversion to common stock warrants and related reclassification to additional paid-in capital (in thousands):
	Balance as of December 31, 2012	$		683
	Recognized gain upon final remeasurement			(24	)
	Reclassification of warrant liability to additional paid-in capital			(659	)
	Balance as of September 30, 2013	$		—
	The recognized gain was included in interest and other income (expense), net.
	The estimated fair value of the convertible preferred stock warrants was determined as of May 22, 2013, the date remeasurement was no longer applicable, and December 31, 2012 using the Black-Scholes option-pricing model using the following assumptions:
		May 22,						December 31,
		2013						2012
	Risk free interest rate		0.11 – 0.91		%				0.26 – 0.57		%
	Estimated term equal to the remaining contractual term		1.7 – 3.8 years						2.1 – 4.2 years
	Volatility		79		%				82		%
	Dividend yield		—						—

Financial_Instruments

Financial Instruments	9 Months Ended
	Sep. 30, 2013
Financial Instruments	'
	4. Financial Instruments
	Cash equivalents, and investments, all of which are classified as available-for-sale securities, consisted of the following (in thousands):
		September 30, 2013													December 31, 2012
		Cost			Unrealized			Unrealized				Estimated				Cost			Unrealized			Unrealized				Estimated
					Gains			Losses				Fair Value							Gains			Losses				Fair Value
	Money market funds	$	54,929	$		—	$		—		$		54,929	$			43,303	$		—	$		—		$		43,303
	Corporate notes and commercial paper		103,034			40			(7	)			103,067				64,403			25			(3	)			64,425
	U.S. government agency securities		57,119			34			(3	)			57,150				19,335			11			—				19,346
		$	215,082	$		74	$		(10	)	$		215,146	$			127,041	$		36	$		(3	)	$		127,074
	Classified as:
	Cash equivalents										$		54,929												$		43,303
	Short-term investments												116,066														77,656
	Long-term investments												44,151														6,115
	Total cash equivalents and investments										$		215,146												$		127,074
	At September 30, 2013 and December 31, 2012, the remaining contractual maturities of available-for-sale securities were less than two years. There have been no significant realized gains or losses on available-for-sale securities for the periods presented.

Derivative_Instruments

Derivative Instruments	9 Months Ended
	Sep. 30, 2013
Derivative Instruments	'
	5. Derivative Instruments
	We are exposed to foreign currency exchange rates related to our business operations. To reduce our risks related to these exposures, we utilize certain derivative instruments, namely foreign currency forward contracts. We do not use derivatives for speculative trading purposes.
	We enter into foreign currency forward contracts, none of which are designated as hedging transactions for accounting purposes, to reduce our exposure to foreign currency fluctuations of certain liabilities denominated in foreign currencies. These exposures are hedged on a quarterly basis. As of September 30, 2013 and December 31, 2012, we had foreign currency forward contracts with notional amounts of €9.5 million ($12.9 million based on the exchange rate as of September 30, 2013) and €16.8million ($22.2 million based on the exchange rate as of December 31, 2012), respectively, that were not designated as hedges. As of September 30, 2013, we recorded a derivative asset within prepaid expenses and other current assets and other long term assets of $239,000 and $27,000, respectively, related to these foreign currency forward contracts. As of December 31, 2012, we recorded a derivative asset within prepaid expenses and other current assets and other long-term assets of $30,000 and $21,000, respectively, related to these foreign currency forward contracts.
	We recorded an unrealized gain of $450,000 and an unrealized gain of $97,000 in interest and other income (expense), net on our condensed statements of operations related to these foreign currency forward contracts for the three and nine months ended September 30, 2013, respectively. During the three and nine months ended September 30, 2013, the Company settled foreign currency forward contracts and recognized a realized gain of $45,000 and $118,000, respectively, in interest and other income (expense), net. During the three and nine months ended September 30, 2012 we recognized an unrealized gain of $243,000 and an unrealized loss of $450,000, respectively, and no realized gains or losses.
	Our derivative financial instruments present certain market and counterparty risks. In general, the market risk related to these contracts is offset by corresponding gains and losses on the hedged transactions. The credit risk associated with these contracts is driven by changes in interest and currency exchange rates and, as a result, varies over time.

Balance_Sheet_Components

Balance Sheet Components	9 Months Ended
	Sep. 30, 2013
Balance Sheet Components	'
	6. Balance Sheet Components
	Accrued and other liabilities consist of the following (in thousands):
		September 30,		December 31,
		2013		2012
	Research and development related	$	14,407	$	4,217
	Legal and accounting fees		323		507
	Deferred rent		866		831
	Accrued offering costs		66		1,506
	Other		298		338
	Total accrued and other liabilities	$	15,960	$	7,399

Collaboration_and_License_Agre

Collaboration and License Agreements	9 Months Ended
	Sep. 30, 2013
Collaboration and License Agreements	'
	7. Collaboration and License Agreements
	Summary of Collaboration Related Revenue
	We have recognized revenue from our collaboration and license agreements as follows (in thousands):
		Three Months Ended September 30,					Nine Months Ended September 30,
		2013			2012			2013			2012
	Novartis:
	Recognition of upfront license fee	$	—	$		738	$		—	$		53,846
	Reimbursement of research and development expense		—			—			—			16,238
	Novartis total		—			738			—			70,084
	BMS and Pfizer:
	Recognition of research and development services		772			—			3,865			—
	BMS and Pfizer total		772			—			3,865			—
	Bayer and Janssen:
	Recognition of research and development services		1,028			—			3,466			—
	Bayer and Janssen total		1,028			—			3,466			—
	Lee’s:
	Recognition of research and development services		78			—			130			—
	Lee’s total		78			—			130			—
	Daiichi Sankyo:
	Recognition of research and development services		888			—			1,013			—
	Daiichi Sankyo total		888			—			1,013			—
	Total collaboration and license revenue	$	2,766	$		738	$		8,474	$		70,084
	Novartis AG (“Novartis”)
	In February 2009, we entered into a license agreement with Novartis to develop and commercialize Elinogrel. We estimated the term of our obligation to participate in the Joint Steering Committee and Joint Development Committee (collectively, the “Committees”) to extend through December 31, 2018. In April 2012, we and Novartis agreed to a plan to return all rights to Elinogrel to Portola and to terminate the exclusive worldwide license agreement effective July 1, 2012. In connection with this plan, the expected term of our obligation to participate in the Committees changed from December 31, 2018 to July 1, 2012. The change in term of the obligation to participate in the Committees was accounted for as a change in accounting estimate on a prospective basis effective April 1, 2012. All remaining deferred revenue was recognized as revenue through July 2012, as no further performance obligations remained upon termination. As of the time of termination, no milestones had been achieved and no royalties had been triggered under our agreement with Novartis.
	Biogen Idec, Inc. (“Biogen Idec”)
	In October 2011, we entered into an exclusive, worldwide license and collaboration agreement with Biogen Idec, under which Portola and Biogen Idec were to jointly develop and commercialize selective, novel oral Syk inhibitors for the treatment of autoimmune and inflammatory diseases.
	In November 2012, we elected to exercise our option under our agreement with Biogen Idec to convert the agreement to a fully out-licensed agreement. After such election, we relinquished our right to share profits from sales of products related to PRT2607 and other selective Syk inhibitors, but are entitled to receive royalties from sales of these products by Biogen Idec. We no longer have the responsibility to fund the program under the agreement. The out-licensed agreement now provides for future payments to us of up to approximately $370.0 million based on the occurrence of certain development and regulatory events. As all contingent consideration payments are based solely on the performance of Biogen Idec, the milestone method of accounting will not be applied to such amounts. Biogen Idec has elected to assume all future development work for Syk inhibitors, including the major indications, such as allergic asthma. This agreement will continue in force until either party terminates the agreement pursuant to the agreement or until the expiration of Biogen Idec’s royalty obligations pursuant to the agreement. Biogen Idec may terminate the agreement without cause upon 120 days’ notice. In such event, we would regain all development rights and Biogen Idec would have no further payment obligations pursuant to the agreement.
	During the three and nine months ended September 30, 2013 and 2012, we recorded a reduction in research and development expense of $227,000 and $721,000, and $1.0 million and $5.9 million, respectively, owed by Biogen Idec to us under the cost-sharing terms of the agreement.
	Bristol-Myers Squibb Company (“BMS”) and Pfizer Inc. (“Pfizer”)
	In October 2012, we entered into a three-way agreement with BMS and Pfizer to include subjects dosed with apixaban, their jointly owned product candidate, in one of our Phase 2 proof-of-concept studies of Andexanet alfa. We are responsible for the cost of conducting this clinical study. BMS and Pfizer will work closely with us on both development and regulatory aspects of Andexanet alfa in connection with our Phase 2 proof-of-concept studies to the extent such matters relate to apixaban. Pursuant to our agreement with BMS and Pfizer we are obligated to provide research and development services and participate on various committees. We originally estimated the period of performance of our obligations to extend through June 2013. In March 2013, we revised our estimated period of performance to be through July 2013. In June 2013, we revised our estimated period of performance to be through September 2013. In September 2013, we revised our estimated period of performance to be through October 2013. The effects of these changes in estimates were not significant.
	The total consideration under this agreement of $6.0 million is being recognized as revenue on a straight-line basis over the estimated performance period through October 2013.
	During the three and nine months ended September 30, 2013, we recognized $772,000 and $3.9 million in collaboration revenue, respectively. The deferred revenue balance as of September 30 2013 was $176,000.
	Lee’s Pharmaceutical (HK) Ltd (“Lee’s”)
	In January 2013, we entered into an agreement with Lee’s to jointly expand our Phase 3 APEX Study of Betrixaban into China. Under the terms of the agreement, Lee’s provided us with an upfront and non-refundable fee of $700,000 and will reimburse our costs in connection with the expansion of the APEX study into China. Lee’s will lead this study and the regulatory interactions with China’s State Food and Drug Administration. We granted Lee’s an exclusive option to negotiate for the exclusive commercial rights to Betrixaban in China, which may be exercised by Lee’s for 60 days after it receives the primary data analysis report from the Phase 3 APEX study.
	We identified the following deliverables under the agreement with Lee’s: 1) the granting of an exclusive option to negotiate for the exclusive commercial rights to Betrixaban in China, 2) the obligation to manufacture and supply product in support of the APEX study in China, 3) the obligation to participate in a joint working group, and 4) the delivery of the primary data analysis report from the APEX study. We considered the provisions of the multiple-element arrangement guidance in determining how to recognize the total consideration of the agreement. We determined that none of the deliverables have standalone value and therefore are accounted for as a single unit of accounting with the upfront fee recognized as revenue ratably over the estimated period of performance. Any reimbursements we may receive from Lee’s for the costs we incur in connection with this agreement are expected to be immaterial.
	During the three and nine months ended September 30, 2013, we recognized $78,000 and $130,000, respectively, of collaboration revenue. The deferred revenue balance as of September 30, 2013 was $570,000.
	Aciex Therapeutics, Inc. (“Aciex”)
	In February 2013, we entered into a license and collaboration agreement with Aciex pursuant to which we granted Aciex an exclusive license to co-develop and co-commercialize PRT2070 and certain related compounds for nonsystemic indications, such as the treatment and prevention of ophthalmological diseases by topical administration and allergic rhinitis by intranasal administration. Under the terms of this risk and cost sharing agreement, Portola and Aciex will each incur and report their own internal research and development costs. Further, third-party related development costs will be shared by Aciex and us 60% and 40%, respectively, until the end of the Phase 2 clinical study, and then equally afterwards. Also, we are entitled to receive either one-half of the profits, if any, generated by future sales of the products developed under the agreement, or royalty payments. Aciex has the primary responsibility for conducting the research and development activities under this agreement. We are obligated to provide assistance in accordance with the agreed upon development plan as well as participate on various committees. We can opt out of our obligation to share in the development costs at various points in time, the timing of which impacts future royalties we may receive based on product sales made by Aciex. All net costs we incur in connection with this agreement will be recognized as research and development expenses. We have not incurred any such costs during the three and nine months ended September 30, 2013 related to this agreement.
	Bayer Pharma, AG (“Bayer”) and Janssen Pharmaceuticals, Inc. (“Janssen”)
	In February 2013, we entered into a three-way agreement with Bayer and Janssen to include subjects dosed with rivaroxaban, their Factor Xa inhibitor product, in one of our Phase 2 proof-of-concept studies of Andexanet alfa. We are responsible for the cost of conducting this clinical study. Under the terms of the agreement, Bayer and Janssen have each provided us with an upfront and non-refundable fee of $2.5 million, for an aggregate fee of $5.0 million. The agreement also provides for additional non-refundable payments to us from Bayer and Janssen of $250,000 each for an aggregate of $500,000 following the delivery of the final written study report of our Phase 2 proof-of-concept studies of Andexanet alfa. Also, we are obligated to participate on a Joint Collaboration Committee (“JCC”) with Bayer and Janssen to oversee the collaboration activities under the agreement.
	We identified the following performance deliverables under the agreement: 1) the obligation to provide research and development services, which includes supplying Andexanet alfa and providing a final written report, and 2) the obligation to participate on the JCC. We considered the provisions of the multiple-element arrangement guidance in determining how to recognize the revenue associated with these two deliverables. We have accounted for the research and development services and our participation on the JCC as a single unit of accounting as neither deliverable has standalone value and both obligations will be delivered throughout the estimated period of performance. We originally estimated the period of performance to be through November 2013. In June 2013, we revised our estimated period of performance to be through January 2014. In September 2013, we revised our estimated period of performance to be through March 2014. The effect of this change was not significant. The total consideration under this agreement is being recognized as revenue ratably over the estimated performance period through March 2014.
	During the three and nine months ended September 30, 2013, we recognized $1.0 million and $3.5 million in collaboration revenue, respectively. The deferred revenue balance as of September 30, 2013 was $1.5 million.
	Daiichi Sankyo, Inc. (“Daiichi Sankyo”)
	In June 2013, we entered into an agreement with Daiichi Sankyo to include subjects dosed with edoxaban, their Factor Xa inhibitor product, in one of our Phase 2 proof-of-concept studies of Andexanet alfa. We are responsible for the cost of conducting this clinical study. Under the terms of the agreement, Daiichi Sankyo will provide us with an upfront fee of $6.0 million, $3.0 million of which is subject to refund should Daiichi Sankyo decide to terminate the agreement. We are obligated to participate on a JCC with Daiichi Sankyo to oversee the collaboration activities under the agreement.
	We identified the following performance deliverables under the agreement: 1) the obligation to provide research and development services, which includes supplying Andexanet alfa and providing a final written report, and 2) the obligation to participate on the JCC.
	We considered the provisions of the multiple-element arrangement guidance in determining how to recognize the revenue associated with these two deliverables. We have accounted for the research and development services and our participation on the JCC as a single unit of accounting as neither deliverable has standalone value and both obligations will be delivered throughout the estimated period of performance through May 2014. The total non-contingent consideration under this agreement of $3.0 million is being recognized as
	revenue ratably over the estimated non-contingent performance period through May 2014. The contingent consideration under this agreement of $3.0 million will be recognized after the contingency is resolved over the remaining performance period, which is currently estimated to begin in May 2014 and conclude in October 2014.
	During the three and nine months ended September 30, 2013, we recognized $888,000 and $1.0 million, respectively, in collaboration revenue associated with the non-contingent element of the arrangement. The contingent element of the arrangement of $3.0 million and the unearned portion of the non-contingent element of the arrangement of $2.0 million was recorded as deferred revenue as of September 30, 2013.

Restructuring_Charge

Restructuring Charge	9 Months Ended
	Sep. 30, 2013
Restructuring Charge	'
	8. Restructuring Charge
	In November 2012, as part of our strategy to better align our capital resources with our clinical development plan, we reduced our workforce by 23 employees, 16 of whom were immediately terminated, five of whom were terminated on January 31, 2013, two of whom were terminated on April 30, 2013. The final restructuring charge of $698,000 includes severance and related costs associated with the termination of the employees. For the nine months ended September 30, 2013, we recorded a net restructuring charge of $79,000, of which $66,000 is included within research and development expense and $13,000 is included within general and administrative expense on our condensed statements of operations. During the nine months ended September 30, 2013, we paid $223,000 of severance costs. At December 31, 2012, the accrued restructuring liability, which is included within accrued and other liabilities on the balance sheet was $143,000. There were no remaining amounts accrued for the restructuring liability at September 30, 2013.

StockBased_Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2013
Stock-Based Compensation	'
	9. Stock-Based Compensation
	In January 2013, our Board of Directors adopted our 2013 Equity Incentive Plan, or the 2013 Plan, which became effective upon of the closing of our IPO in May 2013. As of September 30, 2013 there are 4,903,323 shares reserved under the 2013 Plan for the issuance of options and restricted stock.
	The estimated grant date fair values of the employee stock options were calculated using the Black Scholes valuation model, based on the following assumptions:
		Three Months Ended September 30,											Nine Months Ended September 30,
		2013						2012				2013						2012
	Risk-free interest rate		1.8			%			1.2		%			1.3		%			1.2		%
	Expected life		6.0 years						6.0 years					6.0 years					6.0 years
	Volatility		80			%			70		%			79		%			70		%
	Dividend yield		0			%			0		%			0		%			0		%
	The following table summarizes option activity under our 2003 Equity Incentive Plan and our 2013 Equity Incentive Plan and related information during the nine months ended September 30, 2013:
		Shares Available			Shares Subject to			Weighted-Average
		for Grant			Outstanding			Exercise Price Per
					Options			Share
	Balance at December 31, 2012		593,011			3,451,178		$	6.35
	Options authorized		150,000			—			—
	Options granted		(785,241	)		785,241			17.29
	Options exercised		—			(129,787	)		22.67
	Options cancelled		326,274			(326,274	)		7.81
	Balance at September 30, 2013		284,044			3,780,358		$	7.94
	The table below sets forth the functional classification of stock-based compensation expense, net of estimated forfeitures, for the periods presented (in thousands):
		Three Months Ended September 30,												Nine Months Ended September 30,
		2013							2012						2013						2012
	Research and development	$		787				$		353			$				1,732			$		1,102
	General and administrative			747						303							1,725					965
	Total stock-based compensation	$		1,534				$		656			$				3,457			$		2,067

Net_Income_Loss_per_Share_Attr

Net Income (Loss) per Share Attributable to Common Stockholders	9 Months Ended
	Sep. 30, 2013
Net Income (Loss) per Share Attributable to Common Stockholders	'
	10. Net Income (Loss) per Share Attributable to Common Stockholders
	The following outstanding shares of common stock equivalents were excluded from the computation of diluted net income (loss) per share attributable to common stockholders for the periods presented because including them would have been antidilutive:
		Three Months Ended September 30,							Nine Months Ended September 30,
		2013				2012			2013			2012
	Convertible preferred stock		—				24,026,797			—			24,026,797
	Common stock subject to repurchase		750				—			750			—
	Stock options to purchase common stock		3,780,358				1,678,800			3,780,358			1,605,305
	Preferred stock warrants		—				81,075			—			81,075
	Common stock warrants		82,575				1,500			82,575			1,500
	The following table sets forth the computation of our unaudited basic and diluted net income (loss) per share attributable to common stockholders (in thousands, except share and per share data):
		Three Months Ended September 30,													Nine Months Ended September 30,
		2013								2012						2013				2012
	Net income (loss)	$		(18,550	)			$			(11,488	)		$			(58,290	)	$		25,148
	Noncumulative dividends on convertible preferred stock			—							—						—				(19,065	)
	Undistributed earnings allocated to participating securities			—							—						—				(5,761	)
	Net income (loss) attributable to common stockholders, basic			(18,550	)						(11,488	)					(58,290	)			322
	Adjustment to undistributed earnings allocated to participating securities			—							—						—				140
	Net income (loss) attributable to common stockholders, diluted	$		(18,550	)			$			(11,488	)		$			(58,290	)	$		462
	Basic shares:
	Weighted average common shares outstanding			35,200,761							1,370,190						17,218,475				1,342,919
	Diluted shares:
	Weighted average common shares outstanding			35,200,761							1,370,190						17,218,475				1,342,919
	Weighted average effect of dilutive stock options			—							—						—				633,699
				35,200,761							1,370,190						17,218,475				1,976,618
	Net income (loss) per share attributable to common stockholders:
	Basic	$		(0.53	)			$			(8.38	)		$			(3.39	)	$		0.24
	Diluted	$		(0.53	)			$			(8.38	)		$			(3.39	)	$		0.23

Income_Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2013
Income Taxes	'
	11. Income Taxes
	For the nine months ended September 30, 2012, we did not record an income tax provision on pre-tax income because we incurred a current taxable loss for federal income tax purposes and had available tax credits to offset all state income tax. Tax credits were used in lieu of net operating losses because in 2012 California state law suspended their use. We maintain deferred tax assets that reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. These deferred tax assets include net operating loss carryforwards, research credits and capitalized research and development. Realization of deferred tax assets is dependent upon future earnings, if any, the timing and amount of which are uncertain based on our history of losses. Accordingly, our deferred tax assets have been fully offset by a valuation allowance. Utilization of operating losses and credits may be subject to substantial annual limitation due to ownership change provisions of the Internal Revenue Code of 1986, as amended and similar state provisions. The annual limitation may result in the expiration of net operating losses and credits before utilization.

Subsequent_Events

Subsequent Events	9 Months Ended
	Sep. 30, 2013
Subsequent Events	'
	12. Subsequent Events
	In October 2013, we completed a follow-on offering of 6,366,513 shares of our common stock, which included 1,908,803 shares of common stock sold by certain existing stockholders, at a public offering price of $23.75 per share. In addition, the underwriters of the offering have been granted a 30-day option to purchase up to an additional 954,976 shares from us at the public offering price. This option to purchase additional shares is not yet exercised. The total proceeds from the offering to us, net of underwriting discounts and commissions of approximately $6.4     million and excluding the underwriters’ option, were approximately $99.5     million.  After deducting estimated offering expenses payable by us of approximately $800,000     , net proceeds to us were $98.7 million.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2013
Basis of Presentation	'
	Basis of Presentation
	The accompanying unaudited condensed financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”), and following the requirements of the Securities and Exchange Commission (“SEC”) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These financial statements have been prepared on the same basis as the Company’s annual financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, that are necessary for a fair statement of the Company’s financial information. The results of operations for the nine months ended September 30, 2013 are not necessarily indicative of the results to be expected for the year ending December 31, 2013. The condensed balance sheet as of December 31, 2012 has been derived from audited financial statements at that date but does not include all of the information required by U.S. GAAP for complete financial statements.
	The accompanying condensed financial statements and related financial information should be read in conjunction with the audited financial statements and the related notes thereto for the year ended December 31, 2012 included in the Company’s Prospectus filed pursuant to Rule 424(b)(4) as filed on May 21, 2013 with the SEC.
Reverse Stock Split	'
	Reverse Stock Split
	On May 17, 2013, the Company effected a 1-for-10 reverse split of our preferred stock and common stock. Upon the effectiveness of the reverse stock split every 10 shares of outstanding preferred stock and common stock was decreased to one share of preferred stock or common stock, as applicable, the number of shares of common stock into which each outstanding option to purchase common stock is exercisable was proportionately decreased on a 1-for-10 basis, and the exercise price of each outstanding option to purchase common stock was proportionately increased on a 1-for-10 basis. All the shares numbers, share prices and exercise prices have been adjusted within the condensed financial statements, on a retroactive basis, to reflect the 1-for-10 reverse stock split.
Use of Estimates	'
	Use of Estimates
	The preparation of condensed financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities and the reported amounts of revenues and expenses in the condensed financial statements and the accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to revenue recognition, clinical trial accruals, fair value of assets and liabilities, income taxes and stock-based compensation. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results may differ from those estimates.
Cash and Cash Equivalents	'
	Cash and Cash Equivalents
	Cash and cash equivalents consist of cash and other highly liquid investments with original maturities of three months or less from the date of purchase.
Investments	'
	Investments
	All investments have been classified as “available-for-sale” and are carried at estimated fair value as determined based upon quoted market prices or pricing models for similar securities. Management determines the appropriate classification of its investments in debt securities at the time of purchase and reevaluates such designation as of each balance sheet date. Unrealized gains and losses are excluded from earnings and were reported as a component of accumulated comprehensive income. Realized gains and losses and declines in fair value judged to be other than temporary, if any, on available-for-sale securities are included in interest and other income (expense), net. The cost of securities sold is based on the specific-identification method. Interest on marketable securities is included in interest and other income (expense), net.
Customer Concentration	'
	Customer Concentration
	Customers whose collaborative research and development revenue accounted for 10% or more of total revenues were as follows:
		Three Months Ended September 30,					Nine Months Ended September 30,
			2013		2012			2013		2012
	Novartis AG		—		100	%		—		100	%
	Bristol-Myers Squibb Company and Pfizer Inc.		28	%	—			46	%	—
	Bayer Pharma, AG and Janssen Pharmaceuticals, Inc.		37	%	—			41	%	—
	Daiichi Sankyo, Inc.		32	%	—			12	%	—
Deferred Offering Costs	'
	Deferred Offering Costs
	Deferred offering costs, which primarily consist of direct incremental legal, accounting and printing fees incurred in the preparation of the IPO, were capitalized. The deferred offering costs were offset against IPO proceeds upon completion of the offering in May 2013. As of December 31, 2012, $1.6 million of deferred offering costs were capitalized in other assets on the balance sheets. There were no remaining amounts deferred at September 30, 2013 pertaining to the IPO.
Revenue Recognition	'
	Revenue Recognition
	We generate revenue from collaboration and license agreements for the development and commercialization of our products. Collaboration and license agreements may include non-refundable upfront license fees, partial or complete reimbursement of research and development costs, contingent consideration payments based on the achievement of defined collaboration objectives and royalties on sales of commercialized products. Our performance obligations under our collaborations include the transfer of intellectual property rights (licenses), obligations to provide research and development services and related materials and obligations to participate on certain development and/or commercialization committees with the collaborators.
	Payments that are contingent upon achievement of a substantive milestone are recognized in their entirety in the period in which the milestone is achieved. Milestones are defined as an event that can only be achieved based on our performance and there is substantive uncertainty about whether the event will be achieved at the inception of the arrangement. Events that are contingent only on the passage of time or only on counterparty performance are not considered milestones subject to this guidance. Further, the amounts received must relate solely to prior performance, be reasonable relative to all of the deliverables and payment terms within the agreement and commensurate with our performance to achieve the milestone after commencement of the agreement.
	Amounts from sales of licenses are recognized as revenue, as licensing of intellectual property is one of our principal or major ongoing activities. Amounts received as funding of research and development activities are recognized as revenue if the collaboration arrangement involves the sale of our research or development services at amounts that exceed our cost. However, such funding is recognized as a reduction in research and development expense when we engage in a research and development project jointly with another entity, with both entities participating in project activities and sharing costs and potential benefits of the arrangement.
	Amounts related to research and development funding are recognized as the related services or activities are performed, in accordance with the contract terms. Payments may be made to or by us based on the number of full-time equivalent researchers assigned to the collaboration project and the related research and development expenses incurred.
Foreign Currency Transactions and Hedging	'
	Foreign Currency Transactions and Hedging
	We have transactions denominated in foreign currencies, primarily the Euro, and, as a result, are exposed to changes in foreign currency exchange rates. We manage a portion of these cash flow exposures through the purchase of Euros and the use of foreign currency forward contracts. Our foreign currency forward contracts are not designated as hedges for accounting purposes. Gains or losses on foreign currency forward contracts are intended to offset gains or losses on the underlying net exposures in an effort to reduce the earnings and cash flow volatility resulting from fluctuating foreign currency exchange rates. Foreign currencies and our foreign currency forward contracts are marked to market at the end of each period and recorded as gains and losses in the condensed statements of operations.
	Our foreign exchange forward contracts expose us to credit risk to the extent that the counterparty, a major financial institution, is unable to meet the terms of the agreement. Our management does not expect material losses as a result of defaults by the counterparty.
Net Income (Loss) per Share Attributable to Common Stockholders	'
	Net Income (Loss) per Share Attributable to Common Stockholders
	Basic and diluted net income (loss) per share attributable to common stockholders is calculated in conformity with the two-class method required for companies with participating securities. Under the two-class method, in periods when we have net income, basic net income attributable to common stockholders is determined by allocating undistributed earnings, calculated as net income less current period convertible preferred stock noncumulative dividends, between the common stock and the convertible preferred stock. In computing diluted net income attributable to common stockholders, undistributed earnings are re-allocated to reflect the potential impact of dilutive securities. Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding for the period. The diluted net income per share attributable to common stockholders is computed by giving effect to all potential dilutive common stock equivalents outstanding for the period. In periods when we have incurred a net loss, convertible preferred stock, options and warrants to purchase common stock and convertible preferred stock warrants are considered common stock equivalents but have been excluded from the calculation of diluted net loss per share attributable to common stockholders as their effect is antidilutive.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2013
Revenue Accounted for 10% or More of Total Revenues	'
	Customers whose collaborative research and development revenue accounted for 10% or more of total revenues were as follows:
		Three Months Ended September 30,					Nine Months Ended September 30,
			2013		2012			2013		2012
	Novartis AG		—		100	%		—		100	%
	Bristol-Myers Squibb Company and Pfizer Inc.		28	%	—			46	%	—
	Bayer Pharma, AG and Janssen Pharmaceuticals, Inc.		37	%	—			41	%	—
	Daiichi Sankyo, Inc.		32	%	—			12	%	—

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2013
Summary of Financial Assets, and Liabilities, Allocated into Level 1, Level 2, and Level 3 Measured on Recurring Basis	'
	The following table sets forth the fair value of our financial assets and liabilities, allocated into Level 1, Level 2, and Level 3, that was measured on a recurring basis (in thousands):
		September 30, 2013
		Level 1				Level 2				Level 3			Total
	Financial Assets:
	Money market funds	$		54,930		$	—			$		—	$	54,930
	Corporate notes and commercial paper			—			103,065					—		103,065
	U.S. government agency securities			—			57,150					—		57,150
	Foreign currency forward contracts			—			266					—		266
	Total financial assets	$		54,930		$	160,481			$		—	$	215,411
		December 31, 2012
		Level 1				Level 2				Level 3			Total
	Financial Assets:
	Money market funds	$		43,303		$	—			$		—	$	43,303
	Corporate notes and commercial paper			—			64,425					—		64,425
	U.S. government agency securities			—			19,346					—		19,346
	Foreign currency forward contracts			—			51					—		51
	Total financial assets	$		43,303		$	83,822			$		—	$	127,125
	Financial Liabilities:
	Convertible preferred stock warrant liability	$		—		$	—			$		683	$	683
Summary of Changes in Estimated Fair Value	'
	The following table sets forth a summary of the changes in the estimated fair value of our convertible preferred stock warrants, which were measured at fair value on a recurring basis until their conversion to common stock warrants and related reclassification to additional paid-in capital (in thousands):
	Balance as of December 31, 2012	$		683
	Recognized gain upon final remeasurement			(24	)
	Reclassification of warrant liability to additional paid-in capital			(659	)
	Balance as of September 30, 2013	$		—
Estimated Fair Value of Convertible Preferred Stock Warrant determined Using Black-Sholes Option Pricing Model	'
	The estimated fair value of the convertible preferred stock warrants was determined as of May 22, 2013, the date remeasurement was no longer applicable, and December 31, 2012 using the Black-Scholes option-pricing model using the following assumptions:
		May 22,						December 31,
		2013						2012
	Risk free interest rate		0.11 – 0.91		%				0.26 – 0.57		%
	Estimated term equal to the remaining contractual term		1.7 – 3.8 years						2.1 – 4.2 years
	Volatility		79		%				82		%
	Dividend yield		—						—

Financial_Instruments_Tables

Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2013
Cash Equivalents and Investments Classified as Available-for-sale Securities	'
	Cash equivalents, and investments, all of which are classified as available-for-sale securities, consisted of the following (in thousands):
		September 30, 2013													December 31, 2012
		Cost			Unrealized			Unrealized				Estimated				Cost			Unrealized			Unrealized				Estimated
					Gains			Losses				Fair Value							Gains			Losses				Fair Value
	Money market funds	$	54,929	$		—	$		—		$		54,929	$			43,303	$		—	$		—		$		43,303
	Corporate notes and commercial paper		103,034			40			(7	)			103,067				64,403			25			(3	)			64,425
	U.S. government agency securities		57,119			34			(3	)			57,150				19,335			11			—				19,346
		$	215,082	$		74	$		(10	)	$		215,146	$			127,041	$		36	$		(3	)	$		127,074
	Classified as:
	Cash equivalents										$		54,929												$		43,303
	Short-term investments												116,066														77,656
	Long-term investments												44,151														6,115
	Total cash equivalents and investments										$		215,146												$		127,074

Balance_Sheet_Components_Table

Balance Sheet Components (Tables)	9 Months Ended
	Sep. 30, 2013
Accrued Expenses	'
	Accrued and other liabilities consist of the following (in thousands):
		September 30,		December 31,
		2013		2012
	Research and development related	$	14,407	$	4,217
	Legal and accounting fees		323		507
	Deferred rent		866		831
	Accrued offering costs		66		1,506
	Other		298		338
	Total accrued and other liabilities	$	15,960	$	7,399

Collaboration_and_License_Agre1

Collaboration and License Agreements (Tables)	9 Months Ended
	Sep. 30, 2013
Summary of Revenue from Collaboration and License Agreements	'
	We have recognized revenue from our collaboration and license agreements as follows (in thousands):
		Three Months Ended September 30,					Nine Months Ended September 30,
		2013			2012			2013			2012
	Novartis:
	Recognition of upfront license fee	$	—	$		738	$		—	$		53,846
	Reimbursement of research and development expense		—			—			—			16,238
	Novartis total		—			738			—			70,084
	BMS and Pfizer:
	Recognition of research and development services		772			—			3,865			—
	BMS and Pfizer total		772			—			3,865			—
	Bayer and Janssen:
	Recognition of research and development services		1,028			—			3,466			—
	Bayer and Janssen total		1,028			—			3,466			—
	Lee’s:
	Recognition of research and development services		78			—			130			—
	Lee’s total		78			—			130			—
	Daiichi Sankyo:
	Recognition of research and development services		888			—			1,013			—
	Daiichi Sankyo total		888			—			1,013			—
	Total collaboration and license revenue	$	2,766	$		738	$		8,474	$		70,084

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2013
Fair Values of Employee Stock Options	'
	The estimated grant date fair values of the employee stock options were calculated using the Black Scholes valuation model, based on the following assumptions:
		Three Months Ended September 30,											Nine Months Ended September 30,
		2013						2012				2013						2012
	Risk-free interest rate		1.8			%			1.2		%			1.3		%			1.2		%
	Expected life		6.0 years						6.0 years					6.0 years					6.0 years
	Volatility		80			%			70		%			79		%			70		%
	Dividend yield		0			%			0		%			0		%			0		%
Summary of Option Activities	'
	The following table summarizes option activity under our 2003 Equity Incentive Plan and our 2013 Equity Incentive Plan and related information during the nine months ended September 30, 2013:
		Shares Available			Shares Subject to			Weighted-Average
		for Grant			Outstanding			Exercise Price Per
					Options			Share
	Balance at December 31, 2012		593,011			3,451,178		$	6.35
	Options authorized		150,000			—			—
	Options granted		(785,241	)		785,241			17.29
	Options exercised		—			(129,787	)		22.67
	Options cancelled		326,274			(326,274	)		7.81
	Balance at September 30, 2013		284,044			3,780,358		$	7.94
Classification of Stock-Based Compensation Expense	'
	The table below sets forth the functional classification of stock-based compensation expense, net of estimated forfeitures, for the periods presented (in thousands):
		Three Months Ended September 30,												Nine Months Ended September 30,
		2013							2012						2013						2012
	Research and development	$		787				$		353			$				1,732			$		1,102
	General and administrative			747						303							1,725					965
	Total stock-based compensation	$		1,534				$		656			$				3,457			$		2,067

Net_Income_Loss_per_Share_Attr1

Net Income (Loss) per Share Attributable to Common Stockholders (Tables)	9 Months Ended
	Sep. 30, 2013
Outstanding Shares of Common Stock Equivalents Excluded from Computation of Diluted Net Loss	'
	The following outstanding shares of common stock equivalents were excluded from the computation of diluted net income (loss) per share attributable to common stockholders for the periods presented because including them would have been antidilutive:
		Three Months Ended September 30,							Nine Months Ended September 30,
		2013				2012			2013			2012
	Convertible preferred stock		—				24,026,797			—			24,026,797
	Common stock subject to repurchase		750				—			750			—
	Stock options to purchase common stock		3,780,358				1,678,800			3,780,358			1,605,305
	Preferred stock warrants		—				81,075			—			81,075
	Common stock warrants		82,575				1,500			82,575			1,500
Computation of Basic and Diluted Net Loss Per Share	'
	The following table sets forth the computation of our unaudited basic and diluted net income (loss) per share attributable to common stockholders (in thousands, except share and per share data):
		Three Months Ended September 30,													Nine Months Ended September 30,
		2013								2012						2013				2012
	Net income (loss)	$		(18,550	)			$			(11,488	)		$			(58,290	)	$		25,148
	Noncumulative dividends on convertible preferred stock			—							—						—				(19,065	)
	Undistributed earnings allocated to participating securities			—							—						—				(5,761	)
	Net income (loss) attributable to common stockholders, basic			(18,550	)						(11,488	)					(58,290	)			322
	Adjustment to undistributed earnings allocated to participating securities			—							—						—				140
	Net income (loss) attributable to common stockholders, diluted	$		(18,550	)			$			(11,488	)		$			(58,290	)	$		462
	Basic shares:
	Weighted average common shares outstanding			35,200,761							1,370,190						17,218,475				1,342,919
	Diluted shares:
	Weighted average common shares outstanding			35,200,761							1,370,190						17,218,475				1,342,919
	Weighted average effect of dilutive stock options			—							—						—				633,699
				35,200,761							1,370,190						17,218,475				1,976,618
	Net income (loss) per share attributable to common stockholders:
	Basic	$		(0.53	)			$			(8.38	)		$			(3.39	)	$		0.24
	Diluted	$		(0.53	)			$			(8.38	)		$			(3.39	)	$		0.23

Organization_Additional_Inform

Organization - Additional Information (Detail) (USD $)	1 Months Ended	9 Months Ended
	31-May-13	Sep. 30, 2013
		Segment
Organization And Nature Of Business [Line Items]	'	'
Number of operating segment	'	1
Common stock initial public offering	9,686,171	'
Public offering price of the shares sold	$14.50	'
Proceeds from initial public offering before offering costs	$131,000,000	'
Underwriting discounts and commissions	9,400,000	'
Offering expenses	5,200,000	'
Proceeds from initial public offering, net of underwriters discount	$125,800,000	$131,026,000
Number of preferred stock converted into common stock	24,026,797	'
Underwriters Overallotment Option	'	'
Organization And Nature Of Business [Line Items]	'	'
Common stock initial public offering	1,263,413	'

Revenue_Accounted_for_10_or_Mo

Revenue Accounted for 10% or More of Total Revenues (Detail)	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013
	Novartis AG ("Novartis")	Novartis AG ("Novartis")	Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")	Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")	Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")	Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")	Daiichi Sankyo, Inc ("Daiichi")	Daiichi Sankyo, Inc ("Daiichi")
Concentration Risk [Line Items]	'	'	'	'	'	'	'	'
Percentage of major customers revenue accounted for 10% or more of total revenues	100.00%	100.00%	28.00%	46.00%	37.00%	41.00%	32.00%	12.00%

Summary_of_Significant_Account3

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	1 Months Ended
In Millions, unless otherwise specified	17-May-13	Dec. 31, 2012	Sep. 30, 2013
			IPO
Summary Of Significant Accounting Policies [Line Items]	'	'	'
Reverse stock split ratio on preferred and common stock	0.1	'	'
Deferred offering costs capitalized	'	$1.60	$0

Summary_of_Financial_Assets_an

Summary of Financial Assets, and Liabilities, Allocated into Level 1, Level 2, and Level 3 Measured on Recurring Basis (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Financial Assets:	'	'
Total financial assets	$215,411	$127,125
Fair Value, Inputs, Level 1	'	'
Financial Assets:	'	'
Total financial assets	54,930	43,303
Fair Value, Inputs, Level 2	'	'
Financial Assets:	'	'
Total financial assets	160,481	83,822
Fair Value, Inputs, Level 3	'	'
Financial Assets:	'	'
Total financial assets	'	'
Money market funds	'	'
Financial Assets:	'	'
Fair value of financial assets measured on a recurring basis	54,930	43,303
Money market funds | Fair Value, Inputs, Level 1	'	'
Financial Assets:	'	'
Fair value of financial assets measured on a recurring basis	54,930	43,303
Money market funds | Fair Value, Inputs, Level 2	'	'
Financial Assets:	'	'
Fair value of financial assets measured on a recurring basis	'	'
Money market funds | Fair Value, Inputs, Level 3	'	'
Financial Assets:	'	'
Fair value of financial assets measured on a recurring basis	'	'
Corporate notes and commercial paper	'	'
Financial Assets:	'	'
Fair value of financial assets measured on a recurring basis	103,065	64,425
Corporate notes and commercial paper | Fair Value, Inputs, Level 1	'	'
Financial Assets:	'	'
Fair value of financial assets measured on a recurring basis	'	'
Corporate notes and commercial paper | Fair Value, Inputs, Level 2	'	'
Financial Assets:	'	'
Fair value of financial assets measured on a recurring basis	103,065	64,425
Corporate notes and commercial paper | Fair Value, Inputs, Level 3	'	'
Financial Assets:	'	'
Fair value of financial assets measured on a recurring basis	'	'
U.S. government agency securities	'	'
Financial Assets:	'	'
Fair value of financial assets measured on a recurring basis	57,150	19,346
U.S. government agency securities | Fair Value, Inputs, Level 1	'	'
Financial Assets:	'	'
Fair value of financial assets measured on a recurring basis	'	'
U.S. government agency securities | Fair Value, Inputs, Level 2	'	'
Financial Assets:	'	'
Fair value of financial assets measured on a recurring basis	57,150	19,346
U.S. government agency securities | Fair Value, Inputs, Level 3	'	'
Financial Assets:	'	'
Fair value of financial assets measured on a recurring basis	'	'
Foreign currency forward contracts	'	'
Financial Assets:	'	'
Fair value of financial assets measured on a recurring basis	266	51
Foreign currency forward contracts | Fair Value, Inputs, Level 1	'	'
Financial Assets:	'	'
Fair value of financial assets measured on a recurring basis	'	'
Foreign currency forward contracts | Fair Value, Inputs, Level 2	'	'
Financial Assets:	'	'
Fair value of financial assets measured on a recurring basis	266	51
Foreign currency forward contracts | Fair Value, Inputs, Level 3	'	'
Financial Assets:	'	'
Fair value of financial assets measured on a recurring basis	'	'
Convertible Preferred Stock	'	'
Financial Liabilities:	'	'
Fair value of financial liabilities measured on a recurring basis	'	683
Convertible Preferred Stock | Fair Value, Inputs, Level 1	'	'
Financial Liabilities:	'	'
Fair value of financial liabilities measured on a recurring basis	'	'
Convertible Preferred Stock | Fair Value, Inputs, Level 2	'	'
Financial Liabilities:	'	'
Fair value of financial liabilities measured on a recurring basis	'	'
Convertible Preferred Stock | Fair Value, Inputs, Level 3	'	'
Financial Liabilities:	'	'
Fair value of financial liabilities measured on a recurring basis	'	$683

Summary_of_Changes_in_Estimate

Summary of Changes in Estimated Fair Value (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013
Fair Value Inputs Assets Quantitative Information [Line Items]	'
Balance as of December 31, 2012	$683
Recognized gain upon final remeasurement	-24
Reclassification of warrant liability to additional paid-in capital	-659
Balance as of September 30, 2013	'

Estimated_Fair_Value_of_Conver

Estimated Fair Value of Convertible Preferred Stock Warrant determined Using Black-Sholes Option Pricing Model (Detail)	1 Months Ended	12 Months Ended
	22-May-13	Dec. 31, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'	'
Volatility	79.00%	8200.00%
Dividend yield	'	'
Minimum	'	'
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'	'
Risk free interest rate	0.11%	0.26%
Estimated term equal to the remaining contractual term	'1 year 8 months 12 days	'2 years 1 month 6 days
Maximum	'	'
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'	'
Risk free interest rate	0.91%	0.57%
Estimated term equal to the remaining contractual term	'3 years 9 months 18 days	'4 years 2 months 12 days

Cash_Equivalents_and_Investmen

Cash Equivalents and Investments Classified as Available-for-sale Securities (Detail) (USD $)	9 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Schedule Of Available For Sale Securities [Line Items]	'	'
Cost	$215,082	$127,041
Unrealized Gains	74	36
Unrealized Losses	-10	-3
Estimated Fair Value	215,146	127,074
Money market funds	'	'
Schedule Of Available For Sale Securities [Line Items]	'	'
Cost	54,929	43,303
Unrealized Gains	'	'
Unrealized Losses	'	'
Estimated Fair Value	54,929	43,303
Corporate notes and commercial paper	'	'
Schedule Of Available For Sale Securities [Line Items]	'	'
Cost	103,034	64,403
Unrealized Gains	40	25
Unrealized Losses	-7	-3
Estimated Fair Value	103,067	64,425
U.S. government agency securities	'	'
Schedule Of Available For Sale Securities [Line Items]	'	'
Cost	57,119	19,335
Unrealized Gains	34	11
Unrealized Losses	-3	'
Estimated Fair Value	57,150	19,346
Cash equivalents	'	'
Schedule Of Available For Sale Securities [Line Items]	'	'
Estimated Fair Value	54,929	43,303
Short-term investments	'	'
Schedule Of Available For Sale Securities [Line Items]	'	'
Estimated Fair Value	116,066	77,656
Long-term investments	'	'
Schedule Of Available For Sale Securities [Line Items]	'	'
Estimated Fair Value	$44,151	$6,115

Financial_Instruments_Addition

Financial Instruments - Additional Information (Detail) (USD $)	9 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Schedule Of Available For Sale Securities [Line Items]	'	'
Available-for-sale securities remaining contractual maturities	'2 years	'2 years
Available-for-sale Securities, Gross Realized Gain (Loss)	$0	$0

Derivative_Instruments_Additio

Derivative Instruments - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012
	USD ($)	USD ($)	USD ($)	USD ($)	EUR (€)	USD ($)	EUR (€)	Prepaid Expenses and Other Current Assets	Prepaid Expenses and Other Current Assets	Other Long Lived Assets	Other Long Lived Assets
								USD ($)	USD ($)	USD ($)	USD ($)
Derivatives Fair Value [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Foreign currency forward contracts, notional amount	$12,900,000	'	$12,900,000	'	€ 9,500,000	$22,200,000	€ 16,800,000	'	'	'	'
Derivative assets	'	'	'	'	'	'	'	239,000	30,000	27,000	21,000
Foreign currency forward contracts unrealized gain (loss)	450,000	243,000	97,000	-450,000	'	'	'	'	'	'	'
Foreign currency forward contracts realized gain (loss)	$45,000	$0	$118,000	$0	'	'	'	'	'	'	'

Accrued_Expenses_Detail

Accrued Expenses (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Accounts Payable And Accrued Liabilities [Line Items]	'	'
Research and development related	$14,407	$4,217
Legal and accounting fees	323	507
Deferred rent	866	831
Accrued offering costs	66	1,506
Other	298	338
Total accrued and other liabilities	$15,960	$7,399

Summary_of_Revenue_from_Collab

Summary of Revenue from Collaboration and License Agreements (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]	'	'	'	'
Collaboration and license revenue	$2,766	$738	$8,474	$70,084
Novartis AG ("Novartis")	'	'	'	'
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]	'	'	'	'
Collaboration and license revenue	'	738	'	70,084
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")	'	'	'	'
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]	'	'	'	'
Collaboration and license revenue	772	'	3,865	'
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")	'	'	'	'
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]	'	'	'	'
Collaboration and license revenue	1,028	'	3,466	'
Lee's Pharmaceutical (HK) Ltd ("Lee's")	'	'	'	'
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]	'	'	'	'
Collaboration and license revenue	78	'	130	'
Daiichi Sankyo, Inc ("Daiichi")	'	'	'	'
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]	'	'	'	'
Collaboration and license revenue	888	'	1,013	'
Licensing Agreements | Novartis AG ("Novartis")	'	'	'	'
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]	'	'	'	'
Collaboration and license revenue	'	738	'	53,846
Reimbursement of research and development expense	'	'	'	16,238
Licensing Agreements | Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")	'	'	'	'
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]	'	'	'	'
Collaboration and license revenue	772	'	3,865	'
Licensing Agreements | Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")	'	'	'	'
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]	'	'	'	'
Collaboration and license revenue	1,028	'	3,466	'
Licensing Agreements | Lee's Pharmaceutical (HK) Ltd ("Lee's")	'	'	'	'
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]	'	'	'	'
Collaboration and license revenue	78	'	130	'
Licensing Agreements | Daiichi Sankyo, Inc ("Daiichi")	'	'	'	'
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]	'	'	'	'
Collaboration and license revenue	$888	'	$1,013	'

Collaboration_and_License_Agre2

Collaboration and License Agreements - Additional Information (Detail) (USD $)

3 Months Ended

9 Months Ended

1 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

1 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

1 Months Ended

3 Months Ended

9 Months Ended

6 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Nov. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Oct. 31, 2013

Sep. 30, 2013

Sep. 30, 2013

Jan. 31, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Feb. 01, 2013

Feb. 01, 2013

Feb. 01, 2013

Sep. 30, 2013

Sep. 30, 2013

Jun. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Biogen Idec

Biogen Idec

Biogen Idec

Biogen Idec

Biogen Idec

Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")

Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")

Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")

Lee's Pharmaceutical (HK) Ltd ("Lee's")

Lee's Pharmaceutical (HK) Ltd ("Lee's")

Lee's Pharmaceutical (HK) Ltd ("Lee's")

Aciex Therapeutics, Inc. (Aciex)

Aciex Therapeutics, Inc. (Aciex)

Bayer Pharma AG

Janssen Pharmaceuticals, Inc.

Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")

Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")

Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")

Daiichi Sankyo, Inc ("Daiichi")

Daiichi Sankyo, Inc ("Daiichi")

Daiichi Sankyo, Inc ("Daiichi")

Daiichi Sankyo, Inc ("Daiichi")

PORTOLA PHARMACEUTICALS INC

Collaborative Arrangement

Collaborative Arrangement

Collaborative Arrangement

Collaborative Arrangement

Collaborative Arrangement

Collaborative Arrangement

Collaborative Arrangement

Collaborative Arrangement

Research And Development Arrangement Contract To Perform For Others [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

License fee receivable upon occurrence of certain development and regulatory events

'

'

'

'

$370,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Notice period for agreement termination

'

'

'

'

'120 days

'

'

'

'

'

'

'

'60 days

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Reduction in research and development expense

'

'

'

'

'

227,000

1,000,000

721,000

5,900,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Deferred revenue

'

'

'

'

'

'

'

'

'

6,000,000

176,000

176,000

'

570,000

570,000

'

'

'

'

'

1,500,000

1,500,000

'

'

'

'

'

Collaboration revenue recognized

'

'

'

'

'

'

'

'

'

'

772,000

3,900,000

'

78,000

130,000

'

'

'

'

'

1,000,000

3,500,000

'

'

888,000

1,000,000

'

Upfront and non-refundable fee

'

'

'

'

'

'

'

'

'

'

'

'

700,000

'

'

'

'

2,500,000

2,500,000

5,000,000

'

'

'

'

'

'

'

Development costs, percent

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

60.00%

'

'

'

'

'

'

'

'

'

40.00%

Research and development

18,088,000

9,954,000

56,642,000

36,004,000

'

'

'

'

'

'

'

'

'

'

'

0

0

'

'

'

'

'

'

'

'

'

'

Additional non-refundable fee

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

250,000

250,000

500,000

'

'

'

'

'

'

'

Collaborative arrangement up front payment to be received

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

6,000,000

'

'

'

'

Upfront fee subject to refund

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

3,000,000

'

'

'

'

Contingent consideration of collaboration arrangement

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

3,000,000

3,000,000

'

Non-contingent consideration being recognized as revenue over estimated period of performance

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

3,000,000

'

2,000,000

'

Contingent consideration to be recognized after resolution of contingency

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$3,000,000

'

'

'

Restructuring_Charge_Additiona

Restructuring Charge - Additional Information (Detail) (USD $)	1 Months Ended			9 Months Ended	11 Months Ended
	Apr. 30, 2013	Jan. 31, 2013	Nov. 30, 2012	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2012
	Employee	Employee	Employee	Employee
Restructuring Cost And Reserve [Line Items]	'	'	'	'	'	'
Number of employees terminated	2	5	16	23	'	'
Net restructuring charge	'	'	'	$79,000	$698,000	'
Payment of Severance cost	'	'	'	223,000	'	'
Accrued restructuring liability	'	'	'	'	'	143,000
Research and Development Expense	'	'	'	'	'	'
Restructuring Cost And Reserve [Line Items]	'	'	'	'	'	'
Net restructuring charge	'	'	'	66,000	'	'
General and Administrative Expense	'	'	'	'	'	'
Restructuring Cost And Reserve [Line Items]	'	'	'	'	'	'
Net restructuring charge	'	'	'	$13,000	'	'

Fair_Values_of_Employee_Stock_

Fair Values of Employee Stock Options (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Share Based Compensation Arrangement Assumptions Used To Estimate Fair Values Of Share Options Granted [Line Items]	'	'	'	'
Risk-free interest rate	1.80%	1.20%	1.30%	1.20%
Expected life	'6 years	'6 years	'6 years	'6 years
Volatility	80.00%	70.00%	79.00%	70.00%
Dividend yield	0.00%	0.00%	0.00%	0.00%

Summary_of_Stock_Option_Activi

Summary of Stock Option Activity (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013
Shares Available for Grant	'
Balance at December 31, 2012	593,011
Options authorized	150,000
Options granted	-785,241
Options cancelled	326,274
Balance at September 30, 2013	284,044
Shares Subject to Outstanding Options	'
Balance at December 31, 2012	3,451,178
Options granted	785,241
Options exercised	-129,787
Options cancelled	-326,274
Balance at September 30, 2013	3,780,358
Weighted-Average Exercise Price Per Share	'
Balance at December 31, 2012	$6.35
Options granted	$17.29
Options exercised	$22.67
Options cancelled	$7.81
Balance at September 30, 2013	$7.94

Classification_of_StockBased_C

Classification of Stock-Based Compensation Expense (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]	'	'	'	'
Stock-based compensation	$1,534	$656	$3,457	$2,067
Research and Development Expense	'	'	'	'
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]	'	'	'	'
Stock-based compensation	787	353	1,732	1,102
General and Administrative Expense	'	'	'	'
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]	'	'	'	'
Stock-based compensation	$747	$303	$1,725	$965

StockBased_Compensation_Additi

Stock-Based Compensation - Additional Information (Detail)	Sep. 30, 2013
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]	'
Number of common stock shares reserved for issuance under the 2003 Equity Incentive Plan	4,903,323

Outstanding_Shares_of_Common_S

Outstanding Shares of Common Stock Excluded from Computation of Diluted Net Loss per Share (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Convertible Preferred Stock	'	'	'	'
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]	'	'	'	'
Common stock equivalents excluded from computation of diluted net loss per share	'	24,026,797	'	24,026,797
Common stock subject to repurchase	'	'	'	'
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]	'	'	'	'
Common stock equivalents excluded from computation of diluted net loss per share	750	'	750	'
Stock options to purchase common stock	'	'	'	'
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]	'	'	'	'
Common stock equivalents excluded from computation of diluted net loss per share	3,780,358	1,678,800	3,780,358	1,605,305
Preferred stock warrants	'	'	'	'
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]	'	'	'	'
Common stock equivalents excluded from computation of diluted net loss per share	'	81,075	'	81,075
Common stock warrants	'	'	'	'
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]	'	'	'	'
Common stock equivalents excluded from computation of diluted net loss per share	82,575	1,500	82,575	1,500

Computation_of_Basic_and_Dilut

Computation of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Schedule Of Earnings Per Share Basic And Diluted [Line Items]	'	'	'	'
Net income (loss)	($18,550)	($11,488)	($58,290)	$25,148
Noncumulative dividends on convertible preferred stock	'	'	'	-19,065
Undistributed earnings allocated to participating securities	'	'	'	-5,761
Net income (loss) attributable to common stockholders, basic	-18,550	-11,488	-58,290	322
Adjustment to undistributed earnings allocated to participating securities	'	'	'	140
Net income (loss) attributable to common stockholders, diluted	($18,550)	($11,488)	($58,290)	$462
Basic shares:	'	'	'	'
Weighted average common shares outstanding	35,200,761	1,370,190	17,218,475	1,342,919
Shares used to compute net income (loss) per share attributable to common stockholders:	'	'	'	'
Weighted average common shares outstanding	35,200,761	1,370,190	17,218,475	1,342,919
Weighted average effect of dilutive stock options	'	'	'	633,699
Weighted average number of shares outstanding, Diluted shares	35,200,761	1,370,190	17,218,475	1,976,618
Net income (loss) per share attributable to common stockholders:	'	'	'	'
Basic	($0.53)	($8.38)	($3.39)	$0.24
Diluted	($0.53)	($8.38)	($3.39)	$0.23

Subsequent_Events_Additional_I

Subsequent Events - Additional Information (Detail) (USD $)	1 Months Ended
	31-May-13	Oct. 31, 2013	Oct. 31, 2013
		Subsequent Event	Follow-on offering
			Subsequent Event
Subsequent Event [Line Items]	'	'	'
Common stock initial public offering	9,686,171	1,908,803	6,366,513
Common stock issued per share	'	$23.75	'
Number of days granted for purchase of additional shares	'	'30 days	'
Purchase of additional shares by underwriters	'	954,976	'
Underwriting discounts and commissions	$9,400,000	$6,400,000	'
Proceeds from public offering before offering costs	'	99,500,000	'
Offering expenses	5,200,000	800,000	'
Proceeds from public offering, net of underwriters discount	'	$98,700,000	'