Portola Pharmaceuticals (PTLA) 10-K 2 Mar 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Feb. 27, 2015	Jun. 30, 2014
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	FALSE
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Trading Symbol	PTLA
Entity Registrant Name	PORTOLA PHARMACEUTICALS INC
Entity Central Index Key	1269021
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$857.60
Entity Common Stock, Shares Outstanding		48,952,668

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:
Cash and cash equivalents	$57,514	$117,773
Short-term investments	251,759	150,892
Receivables from collaborations	57	309
Prepaid expenses and other current assets	5,747	3,733
Total current assets	315,077	272,707
Property and equipment, net	2,776	2,600
Long-term investments	83,030	50,371
Prepaid and other long-term assets	15,612	53
Total assets	416,495	325,731
Current liabilities:
Accounts payable	14,084	3,232
Accrued compensation and employee benefits	3,512	2,569
Accrued and other liabilities	13,966	17,796
Deferred revenue, current portion	9,569	1,958
Total current liabilities	41,131	25,555
Deferred revenue, long-term	27,016	3,253
Other long-term liabilities	546	588
Total liabilities	68,693	29,396
Stockholders’ equity:
Preferred stock, $0.001 par value, 5,000,000 shares authorized at December 31, 2014 and 2013; no shares issued and outstanding at December 31, 2014 and 2013;
Common stock, $0.001 par value, 100,000,000 shares authorized at December 31, 2014 and 2013; 48,766,806 shares and 40,915,130 shares issued and outstanding at December 31, 2014 and 2013, respectively	49	41
Additional paid-in capital	770,789	581,911
Accumulated deficit	-422,797	-285,672
Accumulated other comprehensive (loss) income	-239	55
Total stockholders’ equity	347,802	296,335
Total liabilities and stockholders’ equity	$416,495	$325,731

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Statement Of Financial Position [Abstract]
Preferred stock, par value	$0.00	$0.00
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	48,766,806	40,915,130
Common stock, shares outstanding	48,766,806	40,915,130

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement [Abstract]
Collaboration and license revenue	$9,625	$10,531	$72,042
Operating expenses:
Research and development	123,639	79,286	49,717
General and administrative	23,552	15,423	11,469
Total operating expenses	147,191	94,709	61,186
(Loss) income from operations	-137,566	-84,178	10,856
Interest and other income, net	441	826	510
Net (loss) income	-137,125	-83,352	11,366
Net (loss) income attributable to common stockholders:
Basic	-137,125	-83,352
Diluted	($137,125)	($83,352)
Net (loss) income per share attributable to common stockholders:
Basic	($3.19)	($3.65)
Diluted	($3.19)	($3.65)
Shares used to compute net (loss) income per share attributable to common stockholders:
Basic	42,977,463	22,842,443	1,350,939
Diluted	42,977,463	22,842,443	2,048,867

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (Loss) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement Of Income And Comprehensive Income [Abstract]
Net (loss) income	($137,125)	($83,352)	$11,366
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities, net of tax	-294	22	34
Total comprehensive income (loss)	($137,419)	($83,330)	$11,400

Consolidated_Statements_of_Con

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (USD $)	Total	IPO	Follow-on Offering	Convertible Preferred Stock	Common Stock	Common Stock	Common Stock	Additional Paid-in Capital	Additional Paid-in Capital	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
In Thousands, except Share data						IPO	Follow-on Offering		IPO	Follow-on Offering
Balance at beginning of year at Dec. 31, 2011	($206,105)			$317,280	$1			$7,581			($213,686)	($1)
Balance at beginning of year (in shares) at Dec. 31, 2011				24,026,797	1,279,732
Exercise of employee stock options for cash (in shares)					104,417
Exercise of employee stock options for cash	317							317
Lapse of repurchase rights related to common shares issued pursuant to early exercises (in shares)					1,359
Lapse of repurchase rights related to common shares issued pursuant to early exercises	10							10
Employee stock-based compensation expense	2,665							2,665
Compensation expense relating to stock options granted to consultants	144							144
Unrealized gain (loss) on available-for-sale securities, net of tax	34											34
Net (loss) income	11,366										11,366
Balance at end of the year at Dec. 31, 2012	-191,569			317,280	1			10,717			-202,320	33
Balance at end of the year (in shares) at Dec. 31, 2012				24,026,797	1,385,508
Exercise of employee stock options for cash (in shares)					403,468
Exercise of employee stock options for cash	2,529							2,529
Lapse of repurchase rights related to common shares issued pursuant to early exercises (in shares)					500
Lapse of repurchase rights related to common shares issued pursuant to early exercises	4							4
Conversion of preferred stock warrants to common stock warrants	659							659
Conversion of preferred stock to common stock (in shares)				-24,026,797	24,026,797
Conversion of preferred stock to common stock	317,280			-317,280	24			317,256
Issuance of stock (in shares)						9,686,171	5,412,686
Issuance of stock		125,872	119,975			11	5		125,861	119,970
Employee stock-based compensation expense	4,140							4,140
Compensation expense relating to stock options granted to consultants	775							775
Unrealized gain (loss) on available-for-sale securities, net of tax	22											22
Net (loss) income	-83,352										-83,352
Balance at end of the year at Dec. 31, 2013	296,335				41			581,911			-285,672	55
Balance at end of the year (in shares) at Dec. 31, 2013					40,915,130
Exercise of employee stock options for cash (in shares)	652,125				652,125
Exercise of employee stock options for cash	4,399				1			4,398
Lapse of repurchase rights related to common shares issued pursuant to early exercises (in shares)					500
Lapse of repurchase rights related to common shares issued pursuant to early exercises	4							4
Issuance of common stock upon cashless exercise of common stock warrants (shares)					40,314
Issuance of common stock upon cashless exercise of common stock warrants	0
Issuance of common stock pursuant to ESPP purchase (in shares)					28,737
Issuance of common stock pursuant to ESPP purchase	579							579
Issuance of stock (in shares)							7,130,000
Issuance of stock	174,621				7			174,614
Employee stock-based compensation expense	8,514							8,514
Compensation expense relating to stock options granted to consultants	769							769
Unrealized gain (loss) on available-for-sale securities, net of tax	-294											-294
Net (loss) income	-137,125										-137,125
Balance at end of the year at Dec. 31, 2014	$347,802				$49			$770,789			($422,797)	($239)
Balance at end of the year (in shares) at Dec. 31, 2014					48,766,806

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities
Net (loss) income	($137,125)	($83,352)	$11,366
Adjustments to reconcile net income (loss) to cash used in operating activities:
Depreciation and amortization	1,542	1,359	1,389
Amortization of premium on investment securities	3,703	2,333	1,469
Stock-based compensation expense	9,333	4,974	2,809
Revaluation of convertible preferred stock warrant liability		-24	-83
Unrealized (gain) loss on foreign currency forward contracts	114	-261	-51
Changes in operating assets and liabilities:
Receivables from collaborations	252	353	293
Prepaid expenses and other current assets	-2,128	-469	-2,481
Prepaid and other long-term assets	-15,559	396	-2,091
Accounts payable	10,763	-1,773	2,017
Accrued compensation and employee benefits	893	650	-980
Accrued and other liabilities	-3,826	11,908	3,375
Deferred revenue	31,374	1,169	-65,426
Other long-term liabilities	-42	-878	-831
Net cash used in operating activities	-100,706	-63,615	-49,225
Investing activities
Purchases of property and equipment	-1,629	-933	-362
Purchases of investments	-332,171	-219,813	-144,644
Proceeds from sales of investments	2,603	8,009	36,517
Proceeds from maturities of investments	192,045	92,001	40,687
Net cash used in investing activities	-139,152	-120,736	-67,802
Financing activities
Proceeds from public offering of common stock, net of underwriters discount	175,185	251,865
Payment of public offering costs	-564	-5,883
Proceeds from issuance of common stock, including early exercise of stock options	4,978	2,529	317
Net cash provided by financing activities	179,599	248,511	317
Net increase (decrease) in cash and cash equivalents	-60,259	64,160	-116,710
Cash and cash equivalents at beginning of year	117,773	53,613	170,323
Cash and cash equivalents at end of year	57,514	117,773	53,613
Supplemental disclosure of cash flow information
Income taxes paid			57
Noncash investing and financing activities:
Net change in accrued compensation and employee benefits related to ESPP	-51
Net change in accounts payable related to purchase of property and equipment	$89	$165

Organization

Organization	12 Months Ended
	Dec. 31, 2014
Organization Consolidation And Presentation Of Financial Statements [Abstract]
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 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, Cerdulatinib, formerly 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 and Other Offerings
	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.
	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 November 2013, the underwriters exercised their over-allotment option to purchase an additional 954,976 shares from us at the public offering price. The total proceeds from the offering and over-allotment option, net of underwriting discounts and commissions of approximately $7.7 million, were approximately $120.8 million. After deducting offering expenses of approximately $862,000, net proceeds to us were $119.9 million.
	In October 2014, we completed an underwritten public offering of 6,200,000 shares of our common stock at a public offering price of $26.00 per share. In addition, the underwriters exercised their over-allotment option to purchase an additional 930,000 shares from us at the public offering price of $26.00. The net proceeds from the offering to us including the over-allotment option, net of underwriting discounts and commissions of approximately $10.2 million were approximately $175.2 million. After deducting offering expenses of approximately $564,000, net proceeds to us were $174.6 million.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies
	Basis of Consolidation
	The accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”). The accompanying consolidated financial statements include the accounts of Portola and its wholly owned subsidiary as of December 31, 2014. Unless otherwise specified, references to the Company are references to Portola and its consolidated subsidiary. All intercompany transactions and balances have been eliminated upon consolidation.
	Use of Estimates
	The preparation of 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 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.
	Variable Interest Entities
	We review agreements we enter into with third party entities, pursuant to which we may have a variable interest in the entity, in order to determine if the entity is a variable interest entity (VIE). If the entity is a VIE, we assess whether or not we are the primary beneficiary of that entity. In determining whether we are the primary beneficiary of an entity, we apply a qualitative approach that determines whether we have both (1) the power to direct the economically significant activities of the entity and (2) the obligation to absorb losses of, or the right to receive benefits from, the entity that could potentially be significant to that entity. If we determine we are the primary beneficiary of a VIE, we consolidate the statements of operations and financial condition of the VIE into our consolidated financial statements. Our determination about whether we should consolidate such VIEs is made continuously as changes to existing relationships or future transactions may result in a consolidation or deconsolidation event.
	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 our 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 (loss). 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, net. The cost of securities sold is based on the specific-identification method. Interest on marketable securities is included in interest and other income, net.
	Fair Value Measurements
	Fair value accounting is applied for all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis (at least annually).
	Concentration of Risk
	Financial instruments that potentially subject us to concentrations of credit risk consist of cash, cash equivalents, receivables from collaborations and investments. Our investment policy limits investments to certain types of debt securities issued by the U.S. government, its agencies and institutions with investment-grade credit ratings and places restrictions on maturities and concentration by type and issuer. We are exposed to credit risk in the event of a default by the financial institutions holding our cash, cash equivalents and investments and issuers of investments to the extent recorded on the consolidated balance sheets.
	Receivables from collaborations are typically unsecured and are concentrated in the pharmaceutical industry. Accordingly, we may be exposed to credit risk generally associated with pharmaceutical companies or specific to our collaboration agreements. To date, we have not experienced any losses related to these receivables.
	Certain materials and key components that we utilize in our operations are obtained through single suppliers. Since the suppliers of key components and materials must be named in a new drug application (NDA) filed with the U.S. Food and Drug Administration (FDA) for a product, significant delays can occur if the qualification of a new supplier is required. If delivery of material from our suppliers were interrupted for any reason, we may be unable to supply any of our product candidates for clinical trials.
	Customer Concentration
	Customers that accounted for 10% or more of total revenues were as follows:
		Year Ended December 31,
		2014		2013		2012
	Bristol-Myers Squibb Company and Pfizer Inc.		16%		38%	–
	Bayer Pharma, AG and Janssen Pharmaceuticals, Inc.		37%		37%	–
	Daiichi Sankyo, Inc		45%		23%	–
	Novartis, AG	–		–			97%
	Property and Equipment
	Property and equipment are stated at cost and depreciated using the straight-line method over the estimated useful lives of the assets, ranging from two to five years. Leasehold improvements are amortized over the shorter of their estimated useful lives or the related lease term.
	Impairment of Long-Lived Assets
	We review long-lived assets, including property and equipment, for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition are less than its carrying amount. Impairment, if any, is assessed using discounted cash flows or other appropriate measures of fair value. Through December 31, 2014, there have been no such losses.
	Deferred Rent
	We recognize rent expense on a straight-line basis over the noncancelable term of our operating lease and, accordingly, record the difference between cash rent payments and the recognition of rent expense as a deferred rent liability. We also record lessor-funded lease incentives, such as reimbursable leasehold improvements, as a deferred rent liability, which is amortized as a reduction of rent expense over the noncancelable term of our operating lease.
	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 or partially 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 clinical drug supply, obligation to provide regulatory approval services and obligations to participate on certain development and/or commercialization committees with the collaborators. Upfront payments are recorded as deferred revenue in our consolidated balance sheet and are recognized as collaboration revenue over our estimated period of performance that is consistent with the terms of the research and development obligations contained in each collaboration agreement. We regularly review the estimated periods of performance related to our collaborations based on the progress made under each arrangement. Our estimates of our performance period may change over the course of the collaboration term. Such a change could have a material impact on the amount of revenue we record in future periods.
	Payments that are contingent upon achievement of a substantive milestone are recognized in their entirety in the period in which the milestone is achieved. A milestone is 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. Payments contingent upon achievement of events that are not considered substantive milestones are allocated to the respective arrangements unit of accounting when received and recognized as revenue based on the revenue recognition policy for that unit of accounting.
	Amounts from sales of licenses are recognized as revenue. Amounts received as funding of research and development or regulatory approval activities are recognized as revenue if the collaboration arrangement involves the sale of our research or development and regulatory approval 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 and regulatory approval 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.
	Research and Development
	Research and development costs are expensed as incurred and consist of salaries and benefits, lab supplies, materials and facility costs, as well as fees paid to other nonemployees and entities that conduct certain research and development activities on our behalf. Amounts incurred in connection with collaboration and license agreements are also included in research and development expense. Payments made prior to the receipt of goods or services to be used in research and development are capitalized until the goods are received or services are rendered.
	Clinical Trial Accruals
	Clinical trial costs are a component of research and development expenses. We accrue and expense clinical trial activities performed by third parties based upon actual work completed in accordance with agreements established with clinical research organizations and clinical sites. We determine the actual costs through monitoring patient enrollment and discussions with internal personnel and external service providers as to the progress or stage of completion of trials or services and the agreed-upon fee to be paid for such services. The Company has not experienced any material deviations between the accrued clinical trial expenses and actual clinical trial expenses.  However, actual services performed, number of patients enrolled and the rate of patient enrollment may vary from our estimates, resulting in adjustments to clinical trial expense in futures periods.
	Stock-Based Compensation
	Stock-based awards issued to employees, are recorded at fair value as of the grant date using the Black-Scholes option-pricing model and recognized as expense on a straight-line basis over the vesting period of the award. Because noncash stock compensation expense is based on awards ultimately expected to vest, it is reduced by an estimate for future forfeitures. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from estimates.
	Equity instruments issued to nonemployees, consisting of stock options granted to consultants, are valued using the Black-Scholes option-pricing model. Stock-based compensation expense for nonemployee services is subject to remeasurement as the underlying equity instruments vest and is recognized as an expense over the period during which services are received.
	Income Taxes
	We provide for income taxes under the asset and liability method. Current income tax expense or benefit represents the amount of income taxes expected to be payable or refundable for the current year. Deferred income tax assets and liabilities are determined based on differences between the consolidated financial statement reporting and tax bases of assets and liabilities and net operating loss and credit carryforwards, and are measured using the enacted tax rates and laws that will be in effect when such items are expected to reverse. Deferred income tax assets are reduced, as necessary, by a valuation allowance when management determines it is more likely than not that some or all of the tax benefits will not be realized. The recognition, derecognition and measurement of a tax position is based on management’s best judgment given the facts, circumstances and information available at the reporting date. Our policy is to recognize interest and penalties related to the underpayment of income taxes as a component of income tax expense or benefit. To date, there have been no interest or penalties charged in relation to the underpayment of income taxes.
	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 interest and other income, net in the consolidated 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.
	Recent Accounting Pronouncements
	In May 2014, the FASB, jointly with the International Accounting Standards Board, issued, issued ASU 2014-09, Revenue from Contracts with Customers. The standard's core principle is that a reporting entity will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In applying this new guidance to contracts within its scope, an entity will: (1) identify the contract(s) with a customer, (2) identify the performance obligation in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract, and (5) recognize revenue when (or as) the entity satisfies a performance obligation. Additionally, this new guidance will require significantly expanded revenue recognition disclosures. This guidance will become effective for us beginning in the first quarter of 2017. Early application is not permitted. Entities have the option of using either a full retrospective or a modified retrospective approach to adopt this new guidance. We are currently evaluating the impact of our pending adoption of this standard on our consolidated financial statements.

Fair_Value_Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
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, short-term investments, receivables from collaborations, prepaid expenses and other current assets and accounts payable, accrued compensation and employee benefits, accrued and other liabilities and deferred revenue, 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.
	A financial instrument’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. Where quoted prices are available in an active market, securities are classified as Level 1. We classify money market funds as Level 1. When quoted market prices are not available for the specific security, then we estimate fair value by using quoted prices for identical or similar instruments in markets that are not active and model-based valuation techniques for which all significant inputs are observable in the market or can be corroborated by observable market data for substantially the full term of the assets. Where applicable, these models project future cash flows and discount the future amounts to a present value using market-based observable inputs obtained from various third party data providers, including but not limited to, benchmark yields, interest rate curves, reported trades, broker/dealer quotes and market reference data. We classify our corporate notes, commercial paper, U.S. government agency securities and foreign currency forward contracts as Level 2. We have elected to use the income approach to value the 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.
	In certain cases where there is limited activity or less transparency around inputs to valuation, securities are classified as Level 3. Our convertible preferred stock warrant liability was classified as Level 3. The fair values of the 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 preferred stock at the valuation measurement date, the remaining contractual term of the warrants, risk-free interest rates, expected dividends and estimated volatility. Estimated volatility is based on the volatility of our peer group. We monitor the historical volatility of peer group companies on a quarterly basis and adjust our estimated volatility when significant changes in the peer group volatilities occur. The significant unobservable input used in the fair value measurement of the convertible preferred stock warrant liability is the fair value of the underlying preferred stock at the valuation remeasurement date. The preferred stock warrants were converted to common stock warrants upon the completion of the IPO and were no longer subject to remeasurement.
	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):
		December 31, 2014
		Level 1			Level 2		Level 3		Total
	Financial Assets:
	Money market funds	$	24,915		$	–	$	–	$	24,915
	Corporate notes and commercial paper		–			226,047		–		226,047
	U.S. government agency securities		–			120,169		–		120,169
	Total financial assets	$	24,915		$	346,216	$	–	$	371,131
		December 31, 2013
		Level 1			Level 2		Level 3		Total
	Financial Assets:
	Money market funds	$	57,296		$	–	$	–	$	57,296
	Corporate notes and commercial paper		–			182,472		–		182,472
	U.S. government agency securities		–			75,289		–		75,289
	Foreign currency forward contracts		–			372		–		372
	Total financial assets	$	57,296		$	258,133	$	–	$	315,429
	Level 3 liabilities include the convertible preferred stock warrant liability. 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 (in thousands):
	Balance as of December 31, 2011		766
	Recognized gain		(83	)
	Balance as of December 31, 2012		683
	Recognized gain		(24	)
	Reclassification of warrant liability to additional paid-in capital		(659	)
	Balance as of December 31, 2013	$	–
	The estimated fair value of the convertible preferred stock warrants outstanding through May 22, 2013, the date the remeasurement was no longer applicable, and the year ended December 31, 2012 was determined using the Black-Scholes option-pricing model using the following assumptions:
		May 22,			December 31,
		2013			2012
	Risk-free interest rate	0.1 - 0.9%			0.3 - 0.6%
	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	12 Months Ended
	Dec. 31, 2014
Investments Debt And Equity Securities [Abstract]
Financial Instruments	4. Financial Instruments
	Cash equivalents and short-term and long-term investments, all of which are classified as available-for-sale securities, consisted of the following (in thousands):
		December 31, 2014									December 31, 2013
									Estimated									Estimated
				Unrealized		Unrealized			Fair				Unrealized		Unrealized			Fair
		Cost		Gains		(Losses)			Value		Cost		Gains		(Losses)			Value
	Money market funds	$	24,915	$	–	$	–		$	24,915	$	57,296	$	–	$	–		$	57,296
	Corporate notes and commercial paper		226,209		8		(170	)		226,047		182,426		62		(16	)		182,472
	U.S. government agency securities		120,246		4		(81	)		120,169		75,278		23		(12	)		75,289
		$	371,370	$	12	$	(251	)	$	371,131	$	315,000	$	85	$	(28	)	$	315,057
	Classified as:
	Cash equivalents								$	36,341								$	113,794
	Short-term investments									251,759									150,892
	Long-term investments									83,030									50,371
	Total cash equivalents and investments								$	371,131								$	315,057
	At December 31, 2014, 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. Available-for-sale debt securities that were in a continuous loss position but were not deemed to be other than temporarily impaired were immaterial at both December 31, 2014 and 2013.

Derivative_Instruments

Derivative Instruments	12 Months Ended
	Dec. 31, 2014
Derivative Instruments And Hedging Activities Disclosure [Abstract]
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. We held no foreign currency forward contracts at December 31, 2014.  As of December 31, 2013, we had foreign currency forward contracts with notional amounts of €7.7 million ($10.6 million based on the exchange rate as of December 31, 2013). As of December 31, 2013, we recorded a derivative asset within prepaid expenses and other current assets of $372,000 related to these foreign currency forward contracts.
	For the years ended December 31, 2014 and 2013, we recorded an unrealized loss of $114,000 and an unrealized gain of $261,000 , respectively, in interest and other income, net on our consolidated statement of operations related to these foreign currency forward contracts. During the year ended December 31, 2014, we settled foreign currency forward contracts and recognized a realized loss of $258,000 in interest and other income (expense), net. During the year ended December 31, 2013, we settled foreign currency forward contracts and recognized a realized gain of $60,000 in interest and other income (expense), net.
	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	12 Months Ended
	Dec. 31, 2014
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	6. Balance Sheet Components
	Property and Equipment
	Property and equipment consists of the following (in thousands):
		December 31,
		2014			2013
	Computer equipment	$	734		$	618
	Capitalized software		674			463
	Equipment		4,852			3,690
	Leasehold improvements		4,217			3,988
			10,477			8,759
	Less accumulated depreciation and amortization		(7,701	)		(6,159	)
	Property and equipment, net	$	2,776		$	2,600
	Accrued and Other Liabilities
	Accrued and other liabilities consist of the following (in thousands):
		December 31,
		2014			2013
	Research and development related	$	12,545		$	16,110
	Legal and accounting fees		354			462
	Deferred rent		127			879
	Other		940			345
	Total accrued liabilities	$	13,966		$	17,796

Collaboration_and_License_Agre

Collaboration and License Agreements	12 Months Ended
	Dec. 31, 2014
Revenue Recognition [Abstract]
Collaboration and License Agreements	7. Collaboration and License Agreements
	Summary of Collaboration and License Revenue
	We have recognized revenue from our collaboration and license agreements as follows (in thousands):
		Year Ended December 31,
		2014		2013		2012
	Novartis:
	Recognition of upfront license fee	$	–	$	–	$	53,846
	Reimbursement of research and development expense		–		–		16,238
	Novartis total		–		–		70,084
	BMS and Pfizer:
	Recognition of research and development services		1,497		4,042		1,958
	BMS and Pfizer total		1,497		4,042		1,958
	Bayer and Janssen:
	Recognition of research and development services		3,598		3,876		–
	Bayer and Janssen total		3,598		3,876		–
	Lee’s:
	Recognition of research and development services		243		194		–
	Lee’s total		243		194		–
	Daiichi Sankyo:
	Recognition of research and development services		4,287		2,419		–
	Daiichi Sankyo total		4,287		2,419		–
	Total collaboration and license revenue	$	9,625	$	10,531	$	72,042
	Novartis Pharma A.G. (“Novartis”)
	In February 2009, we entered into an exclusive worldwide license agreement with Novartis to develop and commercialize Elinogrel, which was amended in December 2010 and terminated effective July 1, 2012. Under the terms of the license agreement, Novartis made an upfront cash payment to us of $75.0 million in exchange for an exclusive worldwide license to develop and commercialize Elinogrel. We were eligible to receive additional cash payments totaling up to $505.0 million upon achievement by Novartis of certain development, regulatory and commercialization milestones. We were obligated to participate on a Joint Steering Committee and a Joint Development Committee (collectively, the “Committees”) with Novartis through December 31, 2018, to oversee development activities related to Elinogrel, unless Novartis agreed to disband the Committees at an earlier date. Pursuant to the license agreement, Novartis was obligated to fund development and commercialization expenses for Elinogrel after January 1, 2009, except for the first $18.0 million of Phase 2 clinical trial costs and selected tasks, which we were obligated to fund.
	We identified the following performance obligations under the license agreement with Novartis: 1) the transfer of intellectual property rights (license), 2) the obligation to provide certain limited research and development services early during the term of the license agreement and 3) the obligation to participate on the Committees. We accounted for these deliverables as a single unit of accounting, as there was no objective and reliable evidence of the fair value of our undelivered performance obligation with respect to participation on the Committees. The amounts we received from Novartis for the upfront license fee and collaborative research efforts were recognized as collaboration revenue on a straight-line basis from the effective date of payment over the expected performance period.
	We estimated the term of our obligation to participate in 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. The change resulted in a $65.1 million increase in collaboration revenue due to the recognition of all remaining revenue that would have otherwise been recorded over the obligation period through December 31, 2018. Absent this acceleration, the net income for the year ended December 31, 2012 would have been lower by $65.1 million, resulting in a net loss of $53.7 million and net loss per share would have been $3.98 compared to net income per share of $0.00 as reported. As a result of terminating the agreement, all remaining deferred revenue was recognized immediately, 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, which was subsequently converted by its terms into a fully out-licensed agreement, under which Portola and Biogen Idec were to jointly develop and commercialize highly selective, novel oral Syk inhibitors for the treatment of autoimmune and inflammatory diseases, including rheumatoid arthritis, allergic asthma and systemic lupus erythematosus.
	We led the initial development effort for the Syk inhibitor program until commencement of the first Phase 2 clinical trial in late 2012. At that time, Biogen Idec assumed responsibility to lead the global development and commercialization efforts in major indications such as rheumatoid arthritis and allergic asthma. We had the option to elect to lead U.S. development and commercialization efforts for select smaller indications as well as discovery efforts for follow-on Syk inhibitors and retained an option to co-promote the drug alongside Biogen Idec in the United States in major indications. On a product-by-product basis, we had and exercised an option to opt out of our co-funding obligation of the development of such product. Pursuant to this option, we also relinquished our right to share profits from sales of such product(s), but are entitled to receive royalties from Biogen Idec’s sales of these products.
	Under the terms of the agreement, Biogen Idec provided us with a non-refundable upfront cash license fee of $36.0 million and paid $9.0 million for the purchase of 636,042 shares of our Series 1 convertible preferred stock at a premium of $1.1 million above the stock’s estimated fair value. In addition, we estimated that the agreement would provide $22.9 million for the partial reimbursement of certain research and development services and related committee participation and delivery of drug materials.
	We identified the following four non-contingent performance deliverables under the license agreement: 1) the transfer of intellectual property rights (license), 2) the obligation to provide research and development services, 3) the manufacture of drug material for development purposes, until commencement of the first Phase 2 clinical trial and 4) the obligation to participate on various committees. We have the right to opt out of any committees at any time after November 2013.
	We considered the provisions of the multiple-element arrangement guidance in determining whether the deliverables outlined above have standalone value. We believe that Biogen Idec has research and development expertise with compounds similar to those licensed under the agreement and has the ability to engage other third parties to develop these compounds allowing Biogen Idec to realize the value of the license without receiving any of the remaining deliverables. Additionally, under the agreement, Biogen Idec has the right to sublicense this license to third parties, substantially with all the same rights and responsibilities. Therefore, the research and development services, participation in committee activities and provision of drug materials are deemed to have standalone value as Biogen Idec could negotiate for and/or acquire these from other third parties. Although participation in committee activities and provision of drug materials have standalone value, they will be delivered and utilized as the research and development services are performed and have a similar pattern of performance. These three deliverables are combined as one unit of accounting. There are no rights of return under the agreement.
	The upfront license fee of $36.0 million, the premium on the purchase of our Series 1 convertible preferred stock of $1.1 million and research and development expense reimbursements of $22.9 million were allocated to the two separate units of accounting using the relative estimated selling price method.
	The arrangement consideration allocated to the license was recognized as collaboration and license revenue upon delivery in 2011. The amount allocated to the research and development services, materials and committee participation unit of accounting was being recognized over our estimated non-cancellable performance period of two years as a reduction to research and development expense. Under the terms of the agreement, we and Biogen Idec jointly shared development responsibilities prior to the conversion of this agreement into a fully out-licensed agreement, as if the two parties to the agreement incurred those costs directly.
	Based upon the relative estimated selling prices for the two units of accounting for the year ended December 31, 2011, we recognized collaboration revenue of $37.1 million and recorded a reduction in research and development expense for amounts owed by Biogen Idec to us under the cost-sharing terms of the agreement totaling $734,000.
	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. 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. As of December 31, 2014, no such termination event has occurred.
	In April 2014, we entered into an amendment to the Biogen Idec license and collaboration agreement under which Biogen Idec released one of the Syk kinase inhibitors to us for use in topical ophthalmic indications. Per the terms of the amendment, we will be required to pay $15.0 million upon the completion of certain commercial milestones and pay royalties on sales of products approved for these Syk kinase inhibitors. There was no accounting effect resulting from this amendment.
	During the years ended December 31, 2014, 2013 and 2012, we recorded a reduction in research and development expense of $210,000, $804,000 and $6.5 million, respectively, owed by Biogen Idec to us under the cost-sharing terms of the agreement.
	As of December 31, 2014, no milestone in the agreement had been achieved and no royalties had been triggered under this 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 the second quarter 2013. During 2013, we added more cohorts than originally planned as part of the original study design at the inception of our agreement and therefore revised our estimated period of performance to be through the fourth quarter of 2013. The effects of these changes in estimates were not significant.
	The total consideration under this agreement of $6.0 million was recognized as revenue on a straight-line basis over the estimated performance period through the fourth quarter of 2013. For the year ended December 31, 2013 and 2012, we recognized $4.0 and $2.0 million in collaboration revenue, respectively.
	In January 2014, we entered into a collaboration agreement with BMS and Pfizer to further study Andexanet alfa as a reversal agent for their jointly owned FDA approved oral Factor Xa inhibitor, apixaban, through Phase 3 studies. We initiated Phase 3 studies in the first half of 2014. We are responsible for the cost of conducting this clinical study. Pursuant to our agreement with BMS and Pfizer we are obligated to provide research, development and regulatory approval services and participate in the Joint Collaboration Committee (“JCC”) in exchange for a partially refundable upfront fee of $13.0 million and up to $12.0 million of contingent milestone payments due upon achievement of certain development and regulatory events. All consideration received and to be earned under this agreement is subject to a 50% refund contingent upon certain regulatory and/or clinical events.
	We concluded that the January 2014 and October 2012 contracts should each be accounted for as standalone agreements. We identified the following non-cancellable performance deliverables under the January 2014 agreement: 1) the obligation to provide research and development services, which include manufacturing and supplying Andexanet alfa and providing various reports, 2) the obligation to provide regulatory approval services, and 3) the obligation to participate on the JCC. We considered the provisions of the multiple-elements arrangement guidance in determining how to recognize the total agreement consideration. We determined that none of the deliverables have standalone value and all of these obligations will be delivered throughout the estimated period of performance and therefore are accounted for as a single unit of accounting. The non-contingent upfront consideration under this agreement of $6.5 million is being recognized on a straight-line basis over the estimated period of performance. In the third quarter of 2014, we revised the remaining estimated period of performance from the first quarter of 2017 to the first quarter of 2018 to reflect a modification to our clinical development and regulatory plans. The contingent upfront consideration of $6.5 million will be recognized if and when the refundable nature of these amounts lapses based upon the achievement of specified regulatory and/or clinical events.
	The contingent milestone payments under the January 2014 agreement are not considered substantive because a portion may be refunded upon certain events. The non-contingent portion of any milestone payments will be recognized as collaboration revenue on a straight-line basis from their receipt date thru the estimated remaining period of performance. The contingent portion of the milestone payments will be recognized upon receipt if and when the refundable nature of these amounts lapses based upon the achievement of specified regulatory and/or clinical events. None of these milestones had been earned or received at December 31, 2014.
	During the year ended December 31, 2014 we recognized $1.5 million in collaboration revenue under this agreement. The deferred revenue balance under this agreement as of December 31, 2014 was $11.5 million.
	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 on a straight-line basis over the estimated period of performance through the first quarter of 2016. Any reimbursements we may receive from Lee’s for the costs we incur in connection with this agreement have not been material.
	For the year ended December 31, 2014 and 2013, we recognized $243,000 and $194,000 of collaboration revenue under this agreement, respectively. The deferred revenue balance as of December 31, 2014 was $263,000.
	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 total consideration 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 the fourth quarter of 2013. During 2013, we added more cohorts than originally planned as part of the original study design at the inception of our agreement and therefore adjusted our period of performance to be through the fourth quarter of 2014. The total upfront consideration under this agreement was recognized as revenue on a straight-line basis over the performance period through the fourth quarter of 2014.
	For the year ended December 31 2014 and 2013, we recognized $1.1 million and $3.9 million in collaboration revenue, respectively. There was no deferred revenue balance under this agreement as of December 31, 2014.
	In January 2014, we entered into a three-way agreement with Bayer and Janssen to study the safety and efficacy of Andexanet alfa as a reversal agent to their oral Factor Xa inhibitor, rivaroxaban, in our Phase 3 studies. We are responsible for the cost of conducting this clinical study. Pursuant to our agreement with Bayer and Janssen we are obligated to provide research, development and regulatory services and to participate in a JCC in exchange for an upfront nonrefundable fee of $10.0 million, up to three contingent payments totaling $7.0 million which are payable upon achievement of certain events associated with scaling up our manufacturing process to support a commercial launch, and up to three payments totaling $8.0 million which are payable upon initiation of our Phase 3 study and regulatory approval of Andexanet alfa as a reversal agent to rivaroxaban by the FDA and European Medicines Agency (“EMA”).
	We identified the following non-cancellable performance deliverables under the agreement: 1) the obligation to provide research and development services, which include manufacturing and supplying Andexanet alfa and providing various reports, 2) the obligation to provide regulatory approval services, and 3) the obligation to participate on the JCC. 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; all of these obligations will be delivered throughout the estimated period of performance and therefore are accounted for as a single unit of accounting. The total upfront consideration under this agreement is being recognized as revenue on a straight-line basis over the estimated period of performance period. In the third quarter of 2014 we updated our estimated period of performance from the first quarter of 2017 to the first quarter of 2018 to reflect a modification to our clinical development and regulatory plans.
	We have determined all but one of the future contingent payments meet the definition of a milestone and that such milestones are substantive in that the consideration is 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. Accordingly, revenue for the achievement of these milestones will be recognized in the period when the milestone is achieved and collectability is reasonably assured. As of December 31, 2014, no amounts had been recognized as collaboration revenue for any of these milestones. The continent payment of $3.0 million not considered to be a substantive milestone was received in the third quarter of 2014 and is being recognized as collaboration revenue on a straight-line basis over the estimated remaining performance period through the first quarter of 2018.
	During the year ended December 31, 2014 we recognized $2.5 million in collaboration revenue under this agreement. The deferred revenue balance under this agreement as of December 31, 2014 was $10.5 million.
	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 Cerdulatinib (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. In April 2014, this agreement was amended to release all rights for Cerdulatinib to Portola. The collaboration is now focused on development of other related compounds for topical ophthalmic indications. There were no accounting consequences associated with the amendment. 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. During 2014 and 2013, no such costs have been incurred related to this agreement.
	In July 2014, Aciex was acquired by Nicox S.A. and the acquisition closed in October 2014. As of December 31, 2014, there has been no change to our agreement with Aciex.
	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 was 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. We originally estimated the non-contingent consideration under this agreement of $3.0 million would be recorded as revenue on a straight-line basis over the estimated non-contingent performance period through the second quarter of 2014. In December 2013, the JCC agreed to forego certain preclinical studies that were planned in the original study design at the inception of the agreement. As a result of this change, we updated our non-contingent performance period to be through the first quarter of 2014. The recognition of contingent consideration under this agreement of $3.0 million commenced upon resolution of the contingency in the first quarter of 2014 and was originally being recognized over the estimated performance period through the first quarter of 2015. During the fourth quarter of 2014 we decided to include edoxaban data in our initial BLA filing and thus updated the performance period associated with the contingent payment to be through the fourth quarter of 2015.
For the year ended December 31, 2014, we recognized $2.5 million in collaboration revenue associated with the contingent and the non-contingent element of the arrangement. For the year ended December 31, 2013, we recognized $2.4 million in collaboration revenue associated with the non-contingent element of the arrangement. The deferred revenue balance under this agreement as of December 31, 2014 was $1 million.
In July 2014, we entered into an agreement with Daiichi Sankyo to study the safety and efficacy of Andexanet alfa as a reversal agent to their oral Factor Xa inhibitor, edoxaban, in our Phase 3 and Phase 4 studies. We are responsible for the cost of conducting these clinical studies. Pursuant to our agreement with Daiichi Sankyo we are obligated to provide research, development and regulatory services and to participate in a JCC in exchange for an upfront nonrefundable fee of $15.0 million, up to two contingent payments totaling $5.0 million which are payable upon the initiation of our Phase 3 study and achievement of certain events associated with scaling up our manufacturing process to support a commercial launch, and up to four payments totaling $20.0 million which are payable upon acceptance of filing and regulatory approval of Andexanet alfa as a reversal agent to edoxaban by the FDA and EMA.
We identified the following non-cancellable performance deliverables under the agreement: 1) the obligation to provide research and development services, which include manufacturing and supplying Andexanet alfa and providing various reports, 2) the obligation to provide regulatory approval services, and 3) the obligation to participate on the JCC. 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; all of these obligations will be delivered throughout the estimated period of performance and therefore are accounted for as a single unit of accounting. The total upfront consideration under this agreement is being recognized as revenue on a straight-line basis over the estimated performance period through the third quarter of 2018.
We have determined all but one of the future contingent payments meet the definition of a milestone and that such milestones are substantive in that the consideration is reasonable relative to all of the deliverables and payment terms within the agreement are commensurate with our performance to achieve the milestone after commencement of the agreement. Accordingly, revenue for the achievement of these milestones will be recognized in the period when the milestone is achieved and collectability is reasonably assured. As of December 31, 2014, no amounts had been recognized as collaboration revenue for any of these milestones. Amounts for the continent payment not considered to be a substantive milestone will be deferred when received and recognized as collaboration revenue on a straight-line basis over the remaining estimated performance period.
During the year ended December 31, 2014 we recognized $1.8 million in collaboration revenue under this agreement. The deferred revenue balance under this agreement as of December 31, 2014 was $13.2 million.

Commercial_Supply_Agreements

Commercial Supply Agreements	12 Months Ended
	Dec. 31, 2014
Commitments And Contingencies Disclosure [Abstract]
Commercial Supply Agreements	8. Commercial Supply Agreement
	In July 2014, we entered into an agreement with CMC ICOS Biologics, Inc. (“CMC Biologics”), a subsidiary of CMC Biologics S.à.r.l., a privately-held contract manufacturing organization, pursuant to which CMC Biologics will manufacture clinical and commercial supply of Andexanet alfa.
	Under the agreement, we are required to purchase an aggregate fixed number of batches of Andexanet alfa from CMC Biologics beginning in 2015 through 2021. Total batch commitments under the agreement can be increased or decreased based on the achievement of milestones relating to the regulatory approval process for Andexanet alfa, expansion of existing manufacturing capacity and operational qualification of CMC Biologics’ manufacturing facilities. We made an upfront payment to CMC Biologics in the amount of $10.0 million in July 2014 and have made a reservation payment to CMC Biologics of $4.6 million in November 2014. Both payments will be credited against our future purchases of batches under the agreement.
	Total fixed commitments under the agreement for the purchases of clinical and commercial batches, not taking into account possible price and batch adjustments per the terms of the agreement, are approximately $293.9 million. Payments made under the agreement as of December 2014 amount to $2.6 million.
	The term of the agreement is seven years and may be early terminated by either party for the other party’s uncured material breach or insolvency. We may also terminate the agreement if CMC Biologics is unable to add additional manufacturing capacity on a timely basis, if certain manufacturing-related regulatory events do not occur before certain deadlines, or if the batch yield is below a certain threshold, in which case we are not obligated to pay CMC Biologics a termination payment and CMC Biologics will be obligated to refund the uncredited amounts of the upfront payment and reservation payment.
	In addition, we may terminate the agreement unilaterally if we discontinue the development and commercialization of Andexanet alfa for regulatory, safety, efficacy or other commercial reasons, or if the projected market demand or gross margin of Andexanet alfa is below a minimum threshold. The termination provisions will obligate us to pay CMC Biologics a termination fee between $16.0 million and $30.0 million, depending on the date of termination. The termination fee is highest from 2015 through 2017, and then decreases through 2021. Any remaining upfront payments or reservation payments we have made, not yet credited against the purchase of batches, at the time of termination will be applied against the termination fee.
	Under the lease accounting guidance, we determined that the agreement does not contain an embedded lease because the agreement does not convey the right to control the use of CMC Biologics’ facility. We based this determination on, among other factors, our right to physically access and/or operate CMC Biologics’ facility and one or more parties, other than us, and taking more than a minor amount of the output that will be produced or generated by the CMC Biologics facility during the term of our agreement.
	Under the consolidation guidance, we determined that CMC Biologics is a VIE, but that we are not CMC Biologics’ primary beneficiary and therefore consolidation of CMC Biologics by us is not required. We based this determination on, among other factors, the upfront and reservation payment being akin to a form of subordinated financing, the fixed pricing terms of the arrangement creating variability that is absorbed by us, and that we do not have the power to direct the activities that most significantly affect the economic performance of CMC Biologics.
	As of December 31, 2014, we have not provided financial, or other, support to CMC Biologics that was not previously contractually required. The upfront fees of $14.6 million recorded in prepaid expenses and other long-term assets and the batch initiation payments of $2.6 million recorded in prepaid expenses and other current assets in the consolidated balance sheets represents our maximum exposure to loss under this agreement at December 31, 2014. The upfront payment will be charged to research and development expense, or cost of sales, upon regulatory approval of Andexanet alfa, as batches are delivered over the term of the agreement. We are currently not able to quantify the exposure to losses associated with the fixed pricing terms of this agreement.

Asset_Acquisition_and_License_

Asset Acquisition and License Agreements	12 Months Ended
	Dec. 31, 2014
Research And Development [Abstract]
Asset Acquisition and License Agreements	9. Asset Acquisition and License Agreements
	Millennium Pharmaceuticals, Inc. (“Millennium”)
	In November 2003, we acquired patent rights and intellectual property to an ADP Receptor Antagonist Program (“ADP Program”) and a Platelet Biology Program from Millennium. We are obligated to pay royalties on sales of products developed in the ADP Program if product sales are ever achieved.
	In November 2007, we elected to continue our development of Betrixaban and the Factor Xa backup chemistry beyond December 1, 2007 and accordingly, paid $5.0 million in cash to Millennium, which was charged to research and development expense, as the rights had no alternative future use. We could owe Millennium up to $35.0 million upon the occurrence of specified events related to Betrixaban and royalties on sales of Factor Xa products, if such product sales are ever achieved.
	Astellas Pharma, Inc. (“Astellas”)
	In June 2005, we licensed certain rights to research, develop and commercialize Syk inhibitors, including Cerdulatinib, from Astellas.
	In 2011, under the terms of the license agreement and in connection with the Biogen Idec collaboration agreement to develop Syk, we paid $7.2 million in cash to Astellas, which was charged to research and development expense as the rights had no alternative future use.
	We may be required to pay Astellas up to $71.5 million upon the achievement of certain regulatory, approval and sales events for each Syk inhibitor we develop. In the event that we enter into an agreement with a third party to develop and commercialize Syk inhibitors, we would be required to pay Astellas 20% of any payments (excluding royalties) received under the collaboration. These payments would be creditable against the aforementioned milestone payments. In addition, we are required to pay Astellas royalties for worldwide sales for any commercial Syk inhibitor product.

Restructuring_Charge

Restructuring Charge	12 Months Ended
	Dec. 31, 2014
Restructuring And Related Activities [Abstract]
Restructuring Charge	10. 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, and 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 year ended December 31, 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 consolidated statements of operations. During the year ended December 31, 2013, we paid $223,000 of severance costs. There were no remaining amounts accrued for the restructuring liability at December 31, 2013.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2014
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	11. Commitments and Contingencies
	We conduct product research and development programs through a combination of internal and collaborative programs that include, among others, arrangements with universities, contract research organizations and clinical research sites. We have contractual arrangements with these organizations; however, these contracts are cancelable on 30 days’ notice and our obligations under these contracts are largely based on services performed with the exception of our contract manufacturers. Non-cancelable purchase commitments with contract manufacturing organizations exclusive of the commercial supply agreement disclosed in footnote 8 amount to $25.3 million and $2.6 million in services to be performed in 2015 and 2016, respectively.
	Facility Leases
	We lease our corporate, laboratory and other facilities under an operating lease, which was extended in May 2010 through March 31, 2015. The 2010 lease amendment provided for tenant improvement allowances of $3.2 million, which are amortized as a reduction to rent expense on a straight-line basis over the lease term. In March 2014, we signed an amendment to the 2010 lease agreement for additional space and to extend the lease term through March 2020. The 2014 lease amendment provided for a tenant improvement allowance of $1.8 million, which is being amortized as a reduction to rent expense on a straight-line basis over the lease term and an early termination right effective March 2018 with nine months advance notice. The facility lease agreement, as amended, contains scheduled rent increases over the lease term. Under the 2014 lease amendment, we have an option to extend the lease for an additional three-year term. The related rent expense for this lease is calculated on a straight-line basis, with the difference recorded as deferred rent.
	At December 31, 2014, our future minimum commitments under our non-cancelable operating leases were as follows (in thousands):
	Year ending December 31:
	2015	$	1,769
	2016		2,070
	2017		2,134
	2018		2,200
	2019		2,267
	Thereafter		571
	Total	$	11,011
	Rent expense was $1.2 million, $803,000 and $800,000 for the years ended December 31, 2014, 2013 and 2012, respectively.
	Guarantees and Indemnifications
	We indemnify each of our officers and directors for certain events or occurrences, subject to certain limits, while the officer or director is or was serving at our request in such capacity, as permitted under Delaware law and in accordance with our certificate of incorporation and bylaws. The term of the indemnification period lasts as long as an officer or director may be subject to any proceeding arising out of acts or omissions of such officer or director in such capacity.
	The maximum amount of potential future indemnification is unlimited; however, we currently hold director and officer liability insurance. This insurance allows the transfer of risk associated with our exposure and may enable us to recover a portion of any future amounts paid. We believe that the fair value of these indemnification obligations is minimal. Accordingly, we have not recognized any liabilities relating to these obligations for any period presented.

Stock_Based_Compensation

Stock Based Compensation	12 Months Ended
	Dec. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Based Compensation	12. Stock Based Compensation
	Equity Incentive Plan
	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. The 2013 Plan has 935,213 shares of common stock available for future issuance as of December 31, 2014, subject to automatic annual increases beginning on January 1, 2014 through January 1, 2023. Further, all remaining shares available under the 2003 Equity Incentive Plan, or the 2003 Plan, were transferred to the 2013 Plan upon adoption. The 2013 Plan provides for the granting of incentive stock options, nonstatutory stock options, stock bonuses and rights to acquire restricted stock to employees, officers, directors and consultants. Incentive stock options may be granted with exercise prices of not less than 100% of the estimated fair value of our common stock and nonstatutory stock options may be granted with an exercise price of not less than 85% of the estimated fair value of the common stock on the date of grant. Stock options granted to a stockholder owning more than 10% of our voting stock must have an exercise price of not less than 110% of the estimated fair value of the common stock on the date of grant. Stock options are generally granted with terms of up to ten years and vest over a period of four years.
	As of December 31, 2014, 6,949,108 shares of common stock were reserved under the 2013 Plan for the issuance of options and restricted stock.
	A summary of Portola’s stock option activity follows:
						Shares
						Subject to				Weighted-
		Shares Available				Outstanding				Average Exercise
		for Grant				Options				Price Per Share
	Balance at December 31, 2013		81,948				3,708,773			$	9.43
	Options authorized		2,045,785			–				–
	Options granted		(1,358,013	)			1,358,013				25.96
	Options exercised	–					(652,125	)			6.68
	Options canceled		165,493				(165,493	)			18.86
	Balance at December 31, 2014		935,213				4,249,168			$	14.77
	Additional information related to the status of options at December 31, 2014, is as follows (aggregate intrinsic value in thousands):
						Weighted-
						Average				Remaining
						Exercise Price				Contractual			Aggregate
		Shares				Per Share				Life			Intrinsic Value
	Outstanding		4,249,168			$	14.77				6.6		$	57,709
	Vested and expected to vest		4,106,671			$	14.47				6.6		$	57,009
	Vested		2,503,676			$	9.67				5.2		$	46,722
	The aggregate intrinsic values of options outstanding and exercisable, vested and expected to vest were calculated as the difference between the exercise price of the options and the fair value of our common stock as of December 31, 2014. The aggregate intrinsic value of options exercised was $12.5 million, $6.3 million and $451,000 for the years ended December 31, 2014, 2013 and 2012, respectively.
	The total estimated grant date fair value of options vested during the years ended December 31, 2014, 2013 and 2012 was $9.0 million, $3.8 million and $3.0 million, respectively.
	Additional information regarding our stock options outstanding and vested and exercisable as of December 31, 2014 is summarized below:
		Options Outstanding							Options Vested
				Weighted
				Average		Weighted			Number		Weighted
		Number of		Remaining		Average			of		Average
		Options		Contractual		Exercise Price			Options		Exercise Price
	Exercise Prices	Outstanding		Life (Years)		per Share			Vested		Per Share
	$1.00 - $5.10	945,481		2.8		$	4.21		945,481		$	4.21
	$5.30 -  $9.00	1,068,191		6			8.07		927,581			8.21
	$9.50 - $23.85	976,963		8.2			17.61		406,830			16.81
	$24.39 - $26.67	861,050		8.6			25.13		178,702			25.04
	$26.75 - $29.19	397,483		9.5			28.42		45,082			29.02
		4,249,168		6.6		$	14.77		2,503,676		$	9.67
	Stock-based compensation expense, net of estimated forfeitures, is reflected in the consolidated statements of operations as follows (in thousands):
		Year Ended December 31,
		2014				2013				2012
	Research and development	$	4,551			$	2,295			$	1,452
	General and administrative		4,782				2,679				1,357
	Total stock-based compensation	$	9,333			$	4,974			$	2,809
	As of December 31, 2014, total unamortized employee and nonemployee stock-based compensation was $21.8 million, which is expected to be recognized over the remaining estimated vesting period of 2.8 years. The weighted-average grant date fair value of employee options granted during the years ended December 31, 2014, 2013 and 2012 was $15.73, $12.46 and $5.90 per share, respectively.
	Valuation Assumptions
	The employee stock-based compensation expense was determined using the Black-Scholes option valuation model. Option valuation models require the input of subjective assumptions and these assumptions can vary over time. The risk-free rate is based on U.S. Treasury zero-coupon issues with remaining terms similar to the expected terms of the awards. The expected term of employee options granted is determined using the simplified method (based on the midpoint between the vesting date and the end of the contractual term). As sufficient trading history does not yet exist for our common stock, therefore our estimate of expected volatility is based on the volatility of other companies with similar products under development, market, size and other factors. To date, we have not declared or paid any cash dividends and do not have any plans to do so in the future. Therefore, we used an expected dividend yield of zero.
	The following table illustrates the weighted-average assumptions for the Black-Scholes option-pricing model used in determining the fair value of options granted to employees:
		Year Ended December 31,
		2014		2013				2012
	Risk-free interest rate	1.81% - 1.89%			1.43%				1.10%
	Expected life	6.0 years		6.0 years				6.0 years
	Expected volatility	69% - 80%			79%				72%
	Dividend yield	–		–				–
	Options Granted to Nonemployees
	We have granted options to purchase shares of common stock to consultants in exchange for services performed. We granted options to purchase 33,888, 32,943 and 6,380 shares with average exercise prices of $25.41, $19.88 and $7.00 per share, respectively, during the years ended December 31, 2014 2013 and 2012, respectively. These options vest upon grant or various terms up to four years. We recognized non-employees stock compensation expense of $769,000, $775,000 and $144,000  during the years ended December 31, 2014, 2013 and 2012, respectively. The fair value of non-employees’ options was measured using the Black-Scholes option-pricing model reflecting the same assumptions as applied to employee options in each of the reported years, other than the expected life assumption, which is assumed to be the remaining contractual life of the option.
	Employee Stock Purchase Plan
	The Board of Directors adopted the 2013 Employee Stock Purchase Plan, effective upon the completion of Portola’s initial public offering of its common stock. Portola reserved a total of 1,000,000 shares of common stock for issuance under the plan. Eligible employees may purchase common stock at 85 percent of the lesser of the fair market value of Portola’s common stock on the first or last day of the offering period. The reserve for shares available under the plan automatically increases on January 1st each year, beginning in 2014, by an amount equal to 2 percent of the total number of outstanding shares of our common stock on December 31st of the preceding fiscal year.
	The following table illustrates the weighted-average assumptions for the Black-Scholes option-pricing model used in determining the fair value of ESPP purchase rights granted to employees:
		Year Ended December 31,
		2014				2013
	Risk-free interest rate		0.08%				0.10%
	Expected life	0.5 years				0.4 years
	Expected volatility		73%				62%
Dividend yield	–				–

Net_Loss_Income_per_Share_Attr

Net (Loss) Income per Share Attributable to Common Stockholders	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Net Income (Loss) per Share Attributable to Common Stockholders	13. Net (Loss) Income per Share Attributable to Common Stockholders
	The following outstanding shares of common stock equivalents were excluded from the computation of diluted net (loss) income per share attributable to common stockholders for the periods presented because including them would have been antidilutive:
		Year Ended December 31,
		2014			2013			2012
	Convertible preferred stock	–			–				24,026,797
	Stock options to purchase common stock		4,249,168			3,708,773			1,653,298
	Convertible preferred stock warrants	–			–				81,075
	Common stock warrants		6,240			82,575			1,500
	The following table sets forth the computation of our basic and diluted net (loss) income per share attributable to common stockholders (in thousands, except share and per share data):
		Year Ended December 31,
		2104			2013			2012
	Net (loss) income	$	(137,125	)	$	(83,352	)	$	11,366
	Noncumulative dividends on convertible preferred stock	–			–				(11,366	)
	Net loss attributable to common stockholders, basic		(137,125	)		(83,352	)		–
	Adjustment to undistributed earnings allocated to participating securities	–			–			–
	Net loss attributable to common stockholders, diluted	$	(137,125	)	$	(83,352	)	$	–
	Shares used in computing net loss per share attributable to common stockholders, basic		42,977,463			22,842,443			1,350,939
	Dilutive effect of common stock options	–			–				697,928
	Shares used in computing net loss per share attributable to common stockholders, diluted		42,977,463			22,842,443			2,048,867
	Net loss per share attributable to common stockholders:
	Basic	$	(3.19	)	$	(3.65	)	$	–
	Diluted	$	(3.19	)	$	(3.65	)	$	–

Employee_Benefit_Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2014
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plan	14. Employee Benefit Plan
	We sponsor a 401(k) Plan, which stipulates that eligible employees can elect to contribute to the 401(k) Plan, subject to certain limitations of eligible compensation. We match employee contributions up to a maximum of $2,000, $500 and $500 per employee for the years ended December 31, 2014, 2013 and 2012, respectively. During the years ended December 31, 2014, 2013 and 2012, we recognized total expense of $153,000, $59,000 and $31,000, respectively.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Taxes	15. Income Taxes
	We did not record a tax provision for the years ended December 31, 2014, 2013 and 2012. The effective tax rate of our provision for income taxes differs from the federal statutory rate as follows:
		Year Ended December 31,
		2014			2013			2012
	Federal statutory income tax rate		34	%		34	%		34	%
	State income taxes, net of federal benefit		11.2			0.4			22.8
	Federal and state research credits		2.7			3.4			0.8
	Stock based compensation		(1.6	)		(0.2	)		0.4
	Other		(0.1	)		(0.5	)		(0.1	)
	Change in valuation allowance		(46.2	)		(37.1	)		(57.9	)
			0	%		0	%		0	%
	In 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 state law suspended their use. Our valuation allowance at December 31, 2014 and 2013 appropriately considers the balances of both net operating losses and deferred revenue.
	Significant components of our deferred tax assets are as follows (in thousands):
		December 31,
		2014			2013
	Deferred tax assets:
	Federal and state net operating loss carryforwards	$	146,725		$	102,478
	Federal and state research tax credit carryforwards		15,337			10,750
	Deferred revenue		12,523			1,755
	Stock options		3,776			2,895
	Capitalized acquisition costs		1,322			1,295
	Other		3,589			654
	Total deferred tax assets		183,272			119,827
	Valuation allowance		(183,272	)		(119,827	)
	Net deferred tax assets	$	–		$	–
	Realization of the deferred tax assets is dependent upon the generation of future taxable income, if any, the amount and timing of which are uncertain. Based on available objective evidence, including the fact that we have incurred significant losses in almost every year since our inception, management believes it is more likely than not that our deferred tax assets are not recognizable. Accordingly, deferred tax assets have been fully offset by a valuation allowance. The valuation allowance increased by $63.5 million for the year ended December 31, 2014. The valuation allowance increased by $30.7 million for the year ended December 31, 2013.
	As of December 31, 2014, we had net operating loss carryforwards for federal income tax purposes of approximately $364.4 million and federal research tax credits of approximately $15.2 million, which expire at various dates in the period from 2024 to 2034. We also have California net operating loss carry forwards of approximately $449.6 million which expire at various dates in the period from 2018 to 2034 and California research tax credits of $3.8 million. Utilization of the net operating loss carryforwards and credits will be subject to an annual limitation due to the ownership change limitations provided by 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.
	Uncertain Tax Positions
	We have not been audited by the Internal Revenue Service or any state tax authority. We are subject to taxation in the United States. Because of the net operating loss and research credit carryforwards, substantially all of our tax years, from 2003 through 2013, remain open to U.S. federal and California state tax examinations.
	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands):
		Year Ended December 31,
		2014			2013			2012
	Unrecognized tax benefits, beginning of period	$	2,048		$	1,435		$	1,344
	Gross increases - current period tax positions		858			619			91
	Gross decreases - tax position in prior period		–			(6	)		–
	Unrecognized tax benefits, end of period	$	2,906		$	2,048		$	1,435
	The amount of unrecognized income tax benefits that, if recognized, would affect our effective tax rate was $365,000 as of December 31, 2014 and 2013. If the $2.9 million and $2.0 million of unrecognized income tax benefits as of December 31, 2014 and 2013, respectively, is recognized, there would be no impact to the effective tax rate as any change will fully offset the valuation allowance. We believe that it is reasonably possible that a decrease of $365,000 in unrecognized tax benefits related to state exposures is necessary within the coming year as a result of a lapse of the state statute of limitations.

Related_Party_Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2014
Related Party Transactions [Abstract]
Related Party Transactions	16. Related Party Transactions
	Our former President and Chief Executive Officer, who is currently a member of our board of directors, is also a co-founder and member of the board of directors of Global Blood Therapeutics, Inc. (“Global Blood”), and a member of the board of directors of MyoKardia, Inc. (“MyoKardia”). In November 2012, we entered into Master Services Agreements with Global Blood and MyoKardia under which we provide certain consulting, preclinical, laboratory and clinical research related services to each of these companies. For the years ended December 31, 2014, 2013 and 2012, we recorded a reduction in research and development expense of $594,000, $816,000 and $57,000, respectively, related to owed to us by Global Blood and Myokardia under the Master Services Agreements.
	As of December 31, 2014 and 2013, receivables from these related parties in the amount of $40,000 and $394,000 , respectively, are included in prepaid expenses and other current assets on the consolidated balance sheet.

Subsequent_Events

Subsequent Events	12 Months Ended
	Dec. 31, 2014
Subsequent Events [Abstract]
Subsequent Events	17. Subsequent Events
	In January 2015, the Compensation Committee of the Board approved for Portola’s named executive officers performance stock unit (PSU) awards. Each PSU represents a contingent right to receive one share of the Company’s Common Stock. At any time over the four years following the date of grant, half of the shares subject to each PSU will be earned when the average closing price of Portola’s stock on the NASDAQ Global Select Market is above $50.00 per share for 45 consecutive trading days, and an additional half of the shares will be earned when the average closing price of Portola’s stock is above $60 per share for 45 consecutive trading days during such four year period.  Any shares earned will then vest on the one year anniversary of the date such shares were earned, subject to continuous service as of each such date.

Quarterly_Financial_Data

Quarterly Financial Data	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data	18. Quarterly Financial Data
	The following table presents certain unaudited quarterly financial information. This information has been prepared on the same basis as the audited consolidated financial statements and includes all adjustments (consisting only of normal recurring adjustments) necessary to present fairly the unaudited quarterly results of operations set forth herein.
		2014												2013
		Q1			Q2			Q3			Q4			Q1			Q2			Q3			Q4
	Collaboration and license revenue	$	2,372		$	2,415		$	2,427		$	2,411		$	3,108		$	2,601		$	2,766		$	2,056
	Operating expenses	$	(33,396	)	$	(33,920	)	$	(38,204	)	$	(41,671	)	$	(20,761	)	$	(24,541	)	$	(21,995	)	$	(27,412	)
	Net loss	$	(30,726	)	$	(31,350	)	$	(35,793	)	$	(39,256	)	$	(18,142	)	$	(21,598	)	$	(18,550	)	$	(25,062	)
	Net loss per share:
	Basic and diluted	$	(0.75	)	$	(0.76	)	$	(0.86	)	$	(0.82	)	$	(12.94	)	$	(1.47	)	$	(0.53	)	$	(0.63	)

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Basis of Consolidation	Basis of Consolidation
	The accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”). The accompanying consolidated financial statements include the accounts of Portola and its wholly owned subsidiary as of December 31, 2014. Unless otherwise specified, references to the Company are references to Portola and its consolidated subsidiary. All intercompany transactions and balances have been eliminated upon consolidation.
Use of Estimates	Use of Estimates
	The preparation of 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 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.
Variable Interest Entities	Variable Interest Entities
	We review agreements we enter into with third party entities, pursuant to which we may have a variable interest in the entity, in order to determine if the entity is a variable interest entity (VIE). If the entity is a VIE, we assess whether or not we are the primary beneficiary of that entity. In determining whether we are the primary beneficiary of an entity, we apply a qualitative approach that determines whether we have both (1) the power to direct the economically significant activities of the entity and (2) the obligation to absorb losses of, or the right to receive benefits from, the entity that could potentially be significant to that entity. If we determine we are the primary beneficiary of a VIE, we consolidate the statements of operations and financial condition of the VIE into our consolidated financial statements. Our determination about whether we should consolidate such VIEs is made continuously as changes to existing relationships or future transactions may result in a consolidation or deconsolidation event.
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 our 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 (loss). 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, net. The cost of securities sold is based on the specific-identification method. Interest on marketable securities is included in interest and other income, net.
Fair Value Measurements	Fair Value Measurements
	Fair value accounting is applied for all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis (at least annually).
Concentration of Risk	Concentration of Risk
	Financial instruments that potentially subject us to concentrations of credit risk consist of cash, cash equivalents, receivables from collaborations and investments. Our investment policy limits investments to certain types of debt securities issued by the U.S. government, its agencies and institutions with investment-grade credit ratings and places restrictions on maturities and concentration by type and issuer. We are exposed to credit risk in the event of a default by the financial institutions holding our cash, cash equivalents and investments and issuers of investments to the extent recorded on the consolidated balance sheets.
	Receivables from collaborations are typically unsecured and are concentrated in the pharmaceutical industry. Accordingly, we may be exposed to credit risk generally associated with pharmaceutical companies or specific to our collaboration agreements. To date, we have not experienced any losses related to these receivables.
	Certain materials and key components that we utilize in our operations are obtained through single suppliers. Since the suppliers of key components and materials must be named in a new drug application (NDA) filed with the U.S. Food and Drug Administration (FDA) for a product, significant delays can occur if the qualification of a new supplier is required. If delivery of material from our suppliers were interrupted for any reason, we may be unable to supply any of our product candidates for clinical trials.
	Customer Concentration
	Customers that accounted for 10% or more of total revenues were as follows:
		Year Ended December 31,
		2014		2013		2012
	Bristol-Myers Squibb Company and Pfizer Inc.		16%		38%	–
	Bayer Pharma, AG and Janssen Pharmaceuticals, Inc.		37%		37%	–
	Daiichi Sankyo, Inc		45%		23%	–
	Novartis, AG	–		–			97%
Property and Equipment	Property and Equipment
	Property and equipment are stated at cost and depreciated using the straight-line method over the estimated useful lives of the assets, ranging from two to five years. Leasehold improvements are amortized over the shorter of their estimated useful lives or the related lease term.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets
	We review long-lived assets, including property and equipment, for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition are less than its carrying amount. Impairment, if any, is assessed using discounted cash flows or other appropriate measures of fair value. Through December 31, 2014, there have been no such losses.
Deferred Rent	Deferred Rent
	We recognize rent expense on a straight-line basis over the noncancelable term of our operating lease and, accordingly, record the difference between cash rent payments and the recognition of rent expense as a deferred rent liability. We also record lessor-funded lease incentives, such as reimbursable leasehold improvements, as a deferred rent liability, which is amortized as a reduction of rent expense over the noncancelable term of our operating lease.
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 or partially 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 clinical drug supply, obligation to provide regulatory approval services and obligations to participate on certain development and/or commercialization committees with the collaborators. Upfront payments are recorded as deferred revenue in our consolidated balance sheet and are recognized as collaboration revenue over our estimated period of performance that is consistent with the terms of the research and development obligations contained in each collaboration agreement. We regularly review the estimated periods of performance related to our collaborations based on the progress made under each arrangement. Our estimates of our performance period may change over the course of the collaboration term. Such a change could have a material impact on the amount of revenue we record in future periods.
	Payments that are contingent upon achievement of a substantive milestone are recognized in their entirety in the period in which the milestone is achieved. A milestone is 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. Payments contingent upon achievement of events that are not considered substantive milestones are allocated to the respective arrangements unit of accounting when received and recognized as revenue based on the revenue recognition policy for that unit of accounting.
	Amounts from sales of licenses are recognized as revenue. Amounts received as funding of research and development or regulatory approval activities are recognized as revenue if the collaboration arrangement involves the sale of our research or development and regulatory approval 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 and regulatory approval 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.
Research and Development	Research and development and accrued research and development expenses
	Research and development costs are expensed as incurred and consist of salaries and benefits, lab supplies, materials and facility costs, as well as fees paid to other nonemployees and entities that conduct certain research and development activities on our behalf. Amounts incurred in connection with collaboration and license agreements are also included in research and development expense. Payments made prior to the receipt of goods or services to be used in research and development are capitalized until the goods or services are received.
Clinical Trial Expense	Clinical Trial Accruals
	Clinical trial costs are a component of research and development expenses. We accrue and expense clinical trial activities performed by third parties based upon actual work completed in accordance with agreements established with clinical research organizations and clinical sites. We determine the actual costs through monitoring patient enrollment and discussions with internal personnel and external service providers as to the progress or stage of completion of trials or services and the agreed-upon fee to be paid for such services. The Company has not experienced any material deviations between the accrued clinical trial expenses and actual clinical trial expenses.  However, actual services performed, number of patients enrolled and the rate of patient enrollment may vary from our estimates, resulting in adjustments to clinical trial expense in futures periods.
Stock-Based Compensation	Stock-Based Compensation
	Stock-based awards issued to employees, are recorded at fair value as of the grant date using the Black-Scholes option-pricing model and recognized as expense on a straight-line basis over the vesting period of the award. Because noncash stock compensation expense is based on awards ultimately expected to vest, it is reduced by an estimate for future forfeitures. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from estimates.
	Equity instruments issued to nonemployees, consisting of stock options granted to consultants, are valued using the Black-Scholes option-pricing model. Stock-based compensation expense for nonemployee services is subject to remeasurement as the underlying equity instruments vest and is recognized as an expense over the period during which services are received.
Income Taxes	Income Taxes
	We provide for income taxes under the asset and liability method. Current income tax expense or benefit represents the amount of income taxes expected to be payable or refundable for the current year. Deferred income tax assets and liabilities are determined based on differences between the consolidated financial statement reporting and tax bases of assets and liabilities and net operating loss and credit carryforwards, and are measured using the enacted tax rates and laws that will be in effect when such items are expected to reverse. Deferred income tax assets are reduced, as necessary, by a valuation allowance when management determines it is more likely than not that some or all of the tax benefits will not be realized. The recognition, derecognition and measurement of a tax position is based on management’s best judgment given the facts, circumstances and information available at the reporting date. Our policy is to recognize interest and penalties related to the underpayment of income taxes as a component of income tax expense or benefit. To date, there have been no interest or penalties charged in relation to the underpayment of income taxes.
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 interest and other income, net in the consolidated 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.
Recent Accounting Pronouncements	Recent Accounting Pronouncements
	In May 2014, the FASB, jointly with the International Accounting Standards Board, issued, issued ASU 2014-09, Revenue from Contracts with Customers. The standard's core principle is that a reporting entity will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In applying this new guidance to contracts within its scope, an entity will: (1) identify the contract(s) with a customer, (2) identify the performance obligation in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract, and (5) recognize revenue when (or as) the entity satisfies a performance obligation. Additionally, this new guidance will require significantly expanded revenue recognition disclosures. This guidance will become effective for us beginning in the first quarter of 2017. Early application is not permitted. Entities have the option of using either a full retrospective or a modified retrospective approach to adopt this new guidance. We are currently evaluating the impact of our pending adoption of this standard on our consolidated financial statements.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Percentage of Revenue from Significant Customers	Customers that accounted for 10% or more of total revenues were as follows:
		Year Ended December 31,
		2014		2013		2012
	Bristol-Myers Squibb Company and Pfizer Inc.		16%		38%	–
	Bayer Pharma, AG and Janssen Pharmaceuticals, Inc.		37%		37%	–
	Daiichi Sankyo, Inc		45%		23%	–
	Novartis, AG	–		–			97%

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets and Liabilities 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):
		December 31, 2014
		Level 1			Level 2		Level 3		Total
	Financial Assets:
	Money market funds	$	24,915		$	–	$	–	$	24,915
	Corporate notes and commercial paper		–			226,047		–		226,047
	U.S. government agency securities		–			120,169		–		120,169
	Total financial assets	$	24,915		$	346,216	$	–	$	371,131
		December 31, 2013
		Level 1			Level 2		Level 3		Total
	Financial Assets:
	Money market funds	$	57,296		$	–	$	–	$	57,296
	Corporate notes and commercial paper		–			182,472		–		182,472
	U.S. government agency securities		–			75,289		–		75,289
	Foreign currency forward contracts		–			372		–		372
	Total financial assets	$	57,296		$	258,133	$	–	$	315,429
Change in Estimated Fair Value of Convertible Preferred Stock Warrants	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 (in thousands):
Change in Estimated Fair Value of Convertible Preferred Stock Warrants
	Balance as of December 31, 2011		766
	Recognized gain		(83	)
	Balance as of December 31, 2012		683
	Recognized gain		(24	)
	Reclassification of warrant liability to additional paid-in capital		(659	)
	Balance as of December 31, 2013	$	–
Black-Scholes Option-Pricing Model Assumptions to Estimate Fair Value of the Convertible Preferred Stock Warrants	The estimated fair value of the convertible preferred stock warrants outstanding through May 22, 2013, the date the remeasurement was no longer applicable, and the year ended December 31, 2012 was determined using the Black-Scholes option-pricing model using the following assumptions:
		May 22,			December 31,
		2013			2012
	Risk-free interest rate	0.1 - 0.9%			0.3 - 0.6%
	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)	12 Months Ended
	Dec. 31, 2014
Investments Debt And Equity Securities [Abstract]
Cash Equivalents and Investments Classified as Available-for-sale Securities	Cash equivalents and short-term and long-term investments, all of which are classified as available-for-sale securities, consisted of the following (in thousands):
		December 31, 2014									December 31, 2013
									Estimated									Estimated
				Unrealized		Unrealized			Fair				Unrealized		Unrealized			Fair
		Cost		Gains		(Losses)			Value		Cost		Gains		(Losses)			Value
	Money market funds	$	24,915	$	–	$	–		$	24,915	$	57,296	$	–	$	–		$	57,296
	Corporate notes and commercial paper		226,209		8		(170	)		226,047		182,426		62		(16	)		182,472
	U.S. government agency securities		120,246		4		(81	)		120,169		75,278		23		(12	)		75,289
		$	371,370	$	12	$	(251	)	$	371,131	$	315,000	$	85	$	(28	)	$	315,057
	Classified as:
	Cash equivalents								$	36,341								$	113,794
	Short-term investments									251,759									150,892
	Long-term investments									83,030									50,371
	Total cash equivalents and investments								$	371,131								$	315,057

Balance_Sheet_Components_Table

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2014
Balance Sheet Related Disclosures [Abstract]
Property and Equipment	Property and equipment consists of the following (in thousands):
		December 31,
		2014			2013
	Computer equipment	$	734		$	618
	Capitalized software		674			463
	Equipment		4,852			3,690
	Leasehold improvements		4,217			3,988
			10,477			8,759
	Less accumulated depreciation and amortization		(7,701	)		(6,159	)
	Property and equipment, net	$	2,776		$	2,600
Accrued Expenses	Accrued and other liabilities consist of the following (in thousands):
		December 31,
		2014			2013
	Research and development related	$	12,545		$	16,110
	Legal and accounting fees		354			462
	Deferred rent		127			879
	Other		940			345
	Total accrued liabilities	$	13,966		$	17,796

Collaboration_and_License_Agre1

Collaboration and License Agreements (Tables)	12 Months Ended
	Dec. 31, 2014
Revenue Recognition [Abstract]
Summary of Revenue from Collaboration and License Agreements	We have recognized revenue from our collaboration and license agreements as follows (in thousands):
		Year Ended December 31,
		2014		2013		2012
	Novartis:
	Recognition of upfront license fee	$	–	$	–	$	53,846
	Reimbursement of research and development expense		–		–		16,238
	Novartis total		–		–		70,084
	BMS and Pfizer:
	Recognition of research and development services		1,497		4,042		1,958
	BMS and Pfizer total		1,497		4,042		1,958
	Bayer and Janssen:
	Recognition of research and development services		3,598		3,876		–
	Bayer and Janssen total		3,598		3,876		–
	Lee’s:
	Recognition of research and development services		243		194		–
	Lee’s total		243		194		–
	Daiichi Sankyo:
	Recognition of research and development services		4,287		2,419		–
	Daiichi Sankyo total		4,287		2,419		–
	Total collaboration and license revenue	$	9,625	$	10,531	$	72,042

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments And Contingencies Disclosure [Abstract]
Future Minimum Commitments Under our Non-Cancelable Operating Leases	At December 31, 2014, our future minimum commitments under our non-cancelable operating leases were as follows (in thousands):
	Year ending December 31:
	2015	$	1,769
	2016		2,070
	2017		2,134
	2018		2,200
	2019		2,267
	Thereafter		571
	Total	$	11,011

Stock_Based_Compensation_Table

Stock Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2014
Summary of Option Activities	A summary of Portola’s stock option activity follows:
						Shares
						Subject to				Weighted-
		Shares Available				Outstanding				Average Exercise
		for Grant				Options				Price Per Share
	Balance at December 31, 2013		81,948				3,708,773			$	9.43
	Options authorized		2,045,785			–				–
	Options granted		(1,358,013	)			1,358,013				25.96
	Options exercised	–					(652,125	)			6.68
	Options canceled		165,493				(165,493	)			18.86
	Balance at December 31, 2014		935,213				4,249,168			$	14.77
Additional Information Related to the Status of Options	Additional information related to the status of options at December 31, 2014, is as follows (aggregate intrinsic value in thousands):
						Weighted-
						Average				Remaining
						Exercise Price				Contractual			Aggregate
		Shares				Per Share				Life			Intrinsic Value
	Outstanding		4,249,168			$	14.77				6.6		$	57,709
	Vested and expected to vest		4,106,671			$	14.47				6.6		$	57,009
	Vested		2,503,676			$	9.67				5.2		$	46,722
Stock Options Outstanding and Vested and Exercisable	Additional information regarding our stock options outstanding and vested and exercisable as of December 31, 2014 is summarized below:
		Options Outstanding							Options Vested
				Weighted
				Average		Weighted			Number		Weighted
		Number of		Remaining		Average			of		Average
		Options		Contractual		Exercise Price			Options		Exercise Price
	Exercise Prices	Outstanding		Life (Years)		per Share			Vested		Per Share
	$1.00 - $5.10	945,481		2.8		$	4.21		945,481		$	4.21
	$5.30 -  $9.00	1,068,191		6			8.07		927,581			8.21
	$9.50 - $23.85	976,963		8.2			17.61		406,830			16.81
	$24.39 - $26.67	861,050		8.6			25.13		178,702			25.04
	$26.75 - $29.19	397,483		9.5			28.42		45,082			29.02
		4,249,168		6.6		$	14.77		2,503,676		$	9.67
Classification of Stock-Based Compensation Expense	Stock-based compensation expense, net of estimated forfeitures, is reflected in the consolidated statements of operations as follows (in thousands):
		Year Ended December 31,
		2014				2013				2012
	Research and development	$	4,551			$	2,295			$	1,452
	General and administrative		4,782				2,679				1,357
	Total stock-based compensation	$	9,333			$	4,974			$	2,809
Employee Stock Option
Fair Values of Employee Stock Options	The following table illustrates the weighted-average assumptions for the Black-Scholes option-pricing model used in determining the fair value of options granted to employees:
		Year Ended December 31,
		2014		2013				2012
	Risk-free interest rate	1.81% - 1.89%			1.43%				1.10%
	Expected life	6.0 years		6.0 years				6.0 years
	Expected volatility	69% - 80%			79%				72%
	Dividend yield	–		–				–
Employee Stock Purchase Plan
Fair Values of Employee Stock Options	The following table illustrates the weighted-average assumptions for the Black-Scholes option-pricing model used in determining the fair value of ESPP purchase rights granted to employees:
		Year Ended December 31,
		2014				2013
	Risk-free interest rate		0.08%				0.10%
	Expected life	0.5 years				0.4 years
	Expected volatility		73%				62%
	Dividend yield	–				–

Net_Loss_Income_per_Share_Attr1

Net (Loss) Income per Share Attributable to Common Stockholders (Tables)	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Outstanding Shares of Common Stock Equivalents Excluded from Computation of Diluted Net Income Loss	The following outstanding shares of common stock equivalents were excluded from the computation of diluted net (loss) income per share attributable to common stockholders for the periods presented because including them would have been antidilutive:
		Year Ended December 31,
		2014		2013		2012
	Convertible preferred stock	–		–			24,026,797
	Stock options to purchase common stock		4,249,168		3,708,773		1,653,298
	Convertible preferred stock warrants	–		–			81,075
	Common stock warrants		6,240		82,575		1,500

Net_Income_Loss_per_Share_Attr

Net Income (Loss) per Share Attributable to Common Stockholders (Tables)	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net Income Loss Per Share	The following table sets forth the computation of our basic and diluted net (loss) income per share attributable to common stockholders (in thousands, except share and per share data):
		Year Ended December 31,
		2104			2013			2012
	Net (loss) income	$	(137,125	)	$	(83,352	)	$	11,366
	Noncumulative dividends on convertible preferred stock	–			–				(11,366	)
	Net loss attributable to common stockholders, basic		(137,125	)		(83,352	)		–
	Adjustment to undistributed earnings allocated to participating securities	–			–			–
	Net loss attributable to common stockholders, diluted	$	(137,125	)	$	(83,352	)	$	–
	Shares used in computing net loss per share attributable to common stockholders, basic		42,977,463			22,842,443			1,350,939
	Dilutive effect of common stock options	–			–				697,928
	Shares used in computing net loss per share attributable to common stockholders, diluted		42,977,463			22,842,443			2,048,867
	Net loss per share attributable to common stockholders:
	Basic	$	(3.19	)	$	(3.65	)	$	–
	Diluted	$	(3.19	)	$	(3.65	)	$	–

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Reconciliation of Effective Tax Rate for the Provision for Income Taxes	We did not record a tax provision for the years ended December 31, 2014, 2013 and 2012. The effective tax rate of our provision for income taxes differs from the federal statutory rate as follows:
		Year Ended December 31,
		2014			2013			2012
	Federal statutory income tax rate		34	%		34	%		34	%
	State income taxes, net of federal benefit		11.2			0.4			22.8
	Federal and state research credits		2.7			3.4			0.8
	Stock based compensation		(1.6	)		(0.2	)		0.4
	Other		(0.1	)		(0.5	)		(0.1	)
	Change in valuation allowance		(46.2	)		(37.1	)		(57.9	)
			0	%		0	%		0	%
Significant Components of Deferred Tax Assets	Significant components of our deferred tax assets are as follows (in thousands):
		December 31,
		2014			2013
	Deferred tax assets:
	Federal and state net operating loss carryforwards	$	146,725		$	102,478
	Federal and state research tax credit carryforwards		15,337			10,750
	Deferred revenue		12,523			1,755
	Stock options		3,776			2,895
	Capitalized acquisition costs		1,322			1,295
	Other		3,589			654
	Total deferred tax assets		183,272			119,827
	Valuation allowance		(183,272	)		(119,827	)
	Net deferred tax assets	$	–		$	–
Reconciliation of the Beginning and Ending Amount of Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands):
		Year Ended December 31,
		2014			2013			2012
	Unrecognized tax benefits, beginning of period	$	2,048		$	1,435		$	1,344
	Gross increases - current period tax positions		858			619			91
	Gross decreases - tax position in prior period		–			(6	)		–
	Unrecognized tax benefits, end of period	$	2,906		$	2,048		$	1,435

Quarterly_Financial_Data_Table

Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information	The following table presents certain unaudited quarterly financial information. This information has been prepared on the same basis as the audited consolidated financial statements and includes all adjustments (consisting only of normal recurring adjustments) necessary to present fairly the unaudited quarterly results of operations set forth herein.
		2014												2013
		Q1			Q2			Q3			Q4			Q1			Q2			Q3			Q4
	Collaboration and license revenue	$	2,372		$	2,415		$	2,427		$	2,411		$	3,108		$	2,601		$	2,766		$	2,056
	Operating expenses	$	(33,396	)	$	(33,920	)	$	(38,204	)	$	(41,671	)	$	(20,761	)	$	(24,541	)	$	(21,995	)	$	(27,412	)
	Net loss	$	(30,726	)	$	(31,350	)	$	(35,793	)	$	(39,256	)	$	(18,142	)	$	(21,598	)	$	(18,550	)	$	(25,062	)
	Net loss per share:
	Basic and diluted	$	(0.75	)	$	(0.76	)	$	(0.86	)	$	(0.82	)	$	(12.94	)	$	(1.47	)	$	(0.53	)	$	(0.63	)

Organization_Additional_Inform

Organization - Additional Information (Detail) (USD $)	1 Months Ended			12 Months Ended		1 Months Ended
	Oct. 31, 2014	Nov. 30, 2013	31-May-13	Dec. 31, 2014	Dec. 31, 2013	Oct. 31, 2013
				Segment
Organization And Nature Of Business [Line Items]
Number of operating segment				1
Stock issued during the period			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	564,000		5,200,000
Proceeds from initial public offering, net of underwriters discount			125,800,000	175,185,000	251,865,000
Number of preferred stock converted into common stock			24,026,797
Follow on offering price per share	$26					23.75
Proceeds from offering and over-allotment option, gross	175,200,000	120,800,000
Proceeds from offering and over-allotment option, net	174,600,000	119,900,000
Underwriters Overallotment Option
Organization And Nature Of Business [Line Items]
Stock issued during the period	930,000	954,976	1,263,413
Follow-on Offering
Organization And Nature Of Business [Line Items]
Stock issued during the period	6,200,000					6,366,513
Offering expenses		862,000
Stock Issued during period shares existing shareholder						1,908,803
Underwriting discounts and commissions, net	$10,200,000	$7,700,000

Revenue_Accounted_for_10_or_Mo

Revenue Accounted for 10% or More of Total Revenues (Detail) (Customer Concentration Risk, Sales Revenue, Net)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")
Concentration Risk [Line Items]
Concentration risk percentage	16.00%	38.00%
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")
Concentration Risk [Line Items]
Concentration risk percentage	37.00%	37.00%
Daiichi Sankyo, Inc ("Daiichi")
Concentration Risk [Line Items]
Concentration risk percentage	45.00%	23.00%
Novartis AG ("Novartis")
Concentration Risk [Line Items]
Concentration risk percentage			97.00%

Summary_of_Significant_Account3

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014
Summary Of Significant Accounting Policies [Line Items]
Impairment Losses	$0
Interest or penalties charged to the underpayment of income taxes	$0
Minimum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful lives	2 years
Maximum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful lives	5 years

Fair_Values_Measurements_Addit

Fair Values Measurements - Additional Information (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Fair Value Disclosures [Abstract]
Fair value assets transfers from level 1 to level 2	$0	$0
Fair value assets transfers from level 2 to level 1	$0	$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 $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Financial Assets:
Total financial assets	$371,131	$315,429
Fair Value, Inputs, Level 1
Financial Assets:
Total financial assets	24,915	57,296
Fair Value, Inputs, Level 2
Financial Assets:
Total financial assets	346,216	258,133
Money market funds
Financial Assets:
Total financial assets	24,915	57,296
Money market funds | Fair Value, Inputs, Level 1
Financial Assets:
Total financial assets	24,915	57,296
Corporate notes and commercial paper
Financial Assets:
Total financial assets	226,047	182,472
Corporate notes and commercial paper | Fair Value, Inputs, Level 2
Financial Assets:
Total financial assets	226,047	182,472
U.S. government agency securities
Financial Assets:
Total financial assets	120,169	75,289
U.S. government agency securities | Fair Value, Inputs, Level 2
Financial Assets:
Total financial assets	120,169	75,289
Foreign Exchange Forward
Financial Assets:
Total financial assets		372
Foreign Exchange Forward | Fair Value, Inputs, Level 2
Financial Assets:
Total financial assets		$372

Summary_of_Changes_in_the_Esti

Summary of Changes in the Estimated Fair Value of Convertible Preferred Stock Warrants (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Fair Value Disclosures [Abstract]
Beginning balance	$683	$766
Recognized gain	-24	-83
Ending balance		683
Reclassification of warrant liability to additional paid-in capital	($659)

BlackScholes_OptionPricing_Mod

Black-Scholes Option-Pricing Model Assumptions to Estimate Fair Value of the Convertible Preferred Stock Warrants (Detail)	5 Months Ended	12 Months Ended
	22-May-13	Dec. 31, 2012
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Volatility	79.00%	82.00%
Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Risk-free interest rate	0.10%	0.30%
Estimated term equal to the remaining contractual term	1 year 8 months 12 days	2 years 1 month 6 days
Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Risk-free interest rate	0.90%	0.60%
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 $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Schedule Of Available For Sale Securities [Line Items]
Cost	$371,370	$315,000
Unrealized Gains	12	85
Unrealized (Losses)	-251	-28
Estimated Fair Value	371,131	315,057
Money market funds
Schedule Of Available For Sale Securities [Line Items]
Cost	24,915	57,296
Estimated Fair Value	24,915	57,296
Corporate notes and commercial paper
Schedule Of Available For Sale Securities [Line Items]
Cost	226,209	182,426
Unrealized Gains	8	62
Unrealized (Losses)	-170	-16
Estimated Fair Value	226,047	182,472
U.S. government agency securities
Schedule Of Available For Sale Securities [Line Items]
Cost	120,246	75,278
Unrealized Gains	4	23
Unrealized (Losses)	-81	-12
Estimated Fair Value	120,169	75,289
Cash equivalents
Schedule Of Available For Sale Securities [Line Items]
Estimated Fair Value	36,341	113,794
Short-term investments
Schedule Of Available For Sale Securities [Line Items]
Estimated Fair Value	251,759	150,892
Long-term investments
Schedule Of Available For Sale Securities [Line Items]
Estimated Fair Value	$83,030	$50,371

Financial_Instruments_Addition

Financial Instruments - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014
Investments Debt And Equity Securities [Abstract]
Available For Sale Securities Contractual Maturity	2 years
Available-for-sale Securities, Gross Realized Gain (Loss)	$0

Derivative_Instruments_Additio

Derivative Instruments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2013
	USD ($)	USD ($)	USD ($)	EUR (€)	EUR (€)	Prepaid and Other Current Assets
						USD ($)
Derivatives Fair Value [Line Items]
Foreign currency forward contracts, notional amount		$10,600,000		€ 0	€ 7,700,000
Derivative Asset						372,000
Unrealized (gain) loss on foreign currency forward contracts	114,000	-261,000	-51,000
Foreign currency forward contracts recognized realized gain (loss)	$258,000	$60,000

Property_and_Equipment_Detail

Property and Equipment (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Property Plant And Equipment [Line Items]
Property and equipment, gross	$10,477	$8,759
Less accumulated depreciation and amortization	-7,701	-6,159
Property and equipment, net	2,776	2,600
Computer equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	734	618
Capitalized software
Property Plant And Equipment [Line Items]
Property and equipment, gross	674	463
Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	4,852	3,690
Leasehold improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	$4,217	$3,988

Accrued_Expenses_Detail

Accrued Expenses (Detail) (USD $)	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013	31-May-10
In Thousands, unless otherwise specified
Payables And Accruals [Abstract]
Research and development related	$12,545		$16,110
Legal and accounting fees	354		462
Deferred rent	127	1,800	879	3,200
Other	940		345
Total accrued liabilities	$13,966		$17,796

Summary_of_Revenue_from_Collab

Summary of Revenue from Collaboration and License Agreements (Detail) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	$2,411	$2,427	$2,415	$2,372	$2,056	$2,766	$2,601	$3,108	$9,625	$10,531	$72,042
Novartis AG ("Novartis")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue											70,084
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue									1,497	4,042	1,958
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen"), Collaborative arrangements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue									3,598	3,876
Lee’s Pharmaceutical (HK) Ltd (“Lee’s”)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue									243	194
Daiichi Sankyo, Inc ("Daiichi"), Collaborative arrangements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue									4,287	2,419
Licensing Agreements | Novartis AG ("Novartis")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue											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									1,497	4,042	1,958
Licensing Agreements | Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen"), Collaborative arrangements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue									3,598	3,876
Licensing Agreements | Lee’s Pharmaceutical (HK) Ltd (“Lee’s”)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue									243	194
Licensing Agreements | Daiichi Sankyo, Inc ("Daiichi"), Collaborative arrangements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue									$4,287	$2,419

Collaboration_and_License_Agre2

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

1 Months Ended

3 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

6 Months Ended

31-May-13

Dec. 31, 2014

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Apr. 30, 2012

Feb. 28, 2009

Apr. 30, 2014

Nov. 30, 2012

Oct. 31, 2011

Dec. 31, 2011

Jan. 31, 2014

Jan. 31, 2013

Feb. 28, 2013

Jul. 31, 2014

Jun. 30, 2013

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

Increase in collaborative revenue

$31,374,000

$1,169,000

($65,426,000)

Net (loss) income

-39,256,000

-35,793,000

-31,350,000

-30,726,000

-25,062,000

-18,550,000

-21,598,000

-18,142,000

-137,125,000

-83,352,000

11,366,000

Net income (loss) per share

($0.82)

($0.86)

($0.76)

($0.75)

($0.63)

($0.53)

($1.47)

($12.94)

Sale of stock, value

174,621,000

Stock issued during the period

9,686,171

Research and development

123,639,000

79,286,000

49,717,000

PORTOLA PHARMACEUTICALS INC

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

Development costs, percent

40.00%

Novartis AG ("Novartis")

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

Upfront fee

75,000,000

License fee receivable upon occurrence of certain development and regulatory events

505,000,000

Clinical trial costs company must fund

18,000,000

Increase in collaborative revenue

65,100,000

Net income (loss) per share

$0

Novartis AG ("Novartis") | Absent Collaboration Revenue Acceleration

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

Impact of scenario on net income

-65,100,000

Net (loss) income

53,700,000

Net income (loss) per share

($3.98)

Biogen Idec

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

Upfront fee

36,000,000

License fee receivable upon occurrence of certain development and regulatory events

370,000,000

Estimated partial reimbursement of research and development services

22,900,000

Performance period

2 years

Reduction in research and development expense

210,000

804,000

6,500,000

734,000

Notice period for agreement termination

120 days

Payments Upon the Completion of Certain Commercial Milestones

15,000,000

Biogen Idec | Convertible Preferred Stock

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

Sale of stock, value

9,000,000

Stock issued during the period

636,042

Premium on sale of stock

1,100,000

Biogen Idec | Collaborative Arrangement

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

Collaboration revenue recognized

37,100,000

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

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

Upfront fee

13,000,000

Milestone Payments of Development and Regulatory Event

12,000,000

Percentage of consideration received under agreement

50.00%

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

6,500,000

Contingent consideration to be recognized after resolution of contingency

6,500,000

Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | October 2012 Agreement

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

Deferred revenue

6,000,000

6,000,000

Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | January 2014 Agreement

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

Collaboration revenue recognized

1,500,000

Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | Collaborative Arrangement | October 2012 Agreement

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

Collaboration revenue recognized

4,000,000

2,000,000

Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | Collaborative Arrangement | January 2014 Agreement

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

Deferred revenue

11,500,000

11,500,000

Lee’s Pharmaceutical (HK) Ltd (“Lee’s”)

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

Upfront fee

700,000

Notice period for agreement termination

60 days

Deferred revenue

263,000

263,000

Lee’s Pharmaceutical (HK) Ltd (“Lee’s”) | Collaborative Arrangement

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

Collaboration revenue recognized

243,000

194,000

Bayer Pharma AG

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

Additional non-refundable fee

250,000

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

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

Upfront fee

10,000,000

Milestone Payments of Development and Regulatory Event

8,000,000

Additional non-refundable fee

500,000

Contingent payment receivable upon achievement

7,000,000

Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen") | January 2014 Agreement

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

Deferred revenue

10,500,000

10,500,000

Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen") | February 2013 Agreement

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

Deferred revenue

0

0

Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen") | Collaborative Arrangement | January 2014 Agreement

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

Collaboration revenue recognized

2,500,000

Contingent Payments Received

3,000,000

Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen") | Collaborative Arrangement | January 2014 Agreement | Future Contingent Payments

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

Collaboration revenue recognized

0

Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen") | Collaborative Arrangement | February 2013 Agreement

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

Collaboration revenue recognized

1,100,000

3,900,000

Janssen Pharmaceuticals, Inc.

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

Additional non-refundable fee

250,000

Aciex Therapeutics, Inc. (“Aciex”)

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

Development costs, percent

60.00%

Research and development

0

0

Daiichi Sankyo, Inc ("Daiichi")

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

Upfront fee

15,000,000

Milestone Payments of Development and Regulatory Event

20,000,000

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

3,000,000

Contingent consideration to be recognized after resolution of contingency

3,000,000

Contingent payment receivable upon achievement

5,000,000

Collaborative arrangement upfront payment to be received

6,000,000

Upfront fee subject to refund

3,000,000

Daiichi Sankyo, Inc ("Daiichi") | Collaborative Agreement to Study Safety and Efficacy of Andexanet Alfa

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

Deferred revenue

13,200,000

13,200,000

Daiichi Sankyo, Inc ("Daiichi") | Collaborative Agreement to Study Safety and Efficacy of Andexanet Alfa | Future Contingent Payments

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

Collaboration revenue recognized

0

Daiichi Sankyo, Inc ("Daiichi") | Collaborative Arrangement

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

Deferred revenue

1,000,000

1,000,000

Contingent consideration to be recognized after resolution of contingency

2,500,000

Daiichi Sankyo, Inc ("Daiichi") | Collaborative Arrangement | Collaborative Agreement to Study Safety and Efficacy of Andexanet Alfa

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

Collaboration revenue recognized

$1,800,000

Commercial_Supply_Agreements_A

Commercial Supply Agreements - Additional Information (Detail) (CMC ICOS Biologics Inc, USD $)	1 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Jul. 31, 2014	Dec. 31, 2014	Nov. 01, 2014
Long Term Purchase Commitment [Line Items]
Commercial supply agreement upfront payment	$10	$14.60
Commercial supply (manufacturing services) agreement reservation payment			4.6
Commercial agreement fixed commitment amount	293.9
Payments related to commercial supply agreement		2.6
Minimum
Long Term Purchase Commitment [Line Items]
Termination fees payment under obligation	16
Maximum
Long Term Purchase Commitment [Line Items]
Termination fees payment under obligation	$30

Asset_Acquisition_and_License_1

Asset Acquisition and License Agreements - Additional Information (Detail) (USD $)	12 Months Ended			1 Months Ended		12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Nov. 30, 2007	Dec. 31, 2014	Dec. 31, 2011
Asset Acquisition [Line Items]
Research and development	$123,639,000	$79,286,000	$49,717,000
Millennium
Asset Acquisition [Line Items]
License fees paid				5,000,000
Research and development				5,000,000
Millennium | Maximum
Asset Acquisition [Line Items]
Additional license fees payable on occurrence of specified events					35,000,000
Astellas Pharma Inc
Asset Acquisition [Line Items]
License fees paid						7,200,000
Research and development						7,200,000
Percentage required to pay for any payment received under collaboration excluding royalties	20.00%				20.00%
Astellas Pharma Inc | Maximum
Asset Acquisition [Line Items]
Additional license fees payable on occurrence of specified events					$71,500,000

Restructuring_Charge_Additiona

Restructuring Charge - Additional Information (Detail) (USD $)	1 Months Ended			12 Months Ended	14 Months Ended
	Apr. 30, 2013	Jan. 31, 2013	Nov. 30, 2012	Dec. 31, 2013	Dec. 31, 2013
	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				0	0
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

Commitments_and_Contingencies_1

Commitments and Contingencies - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended
	31-May-10	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2014
Commitments And Contingencies Disclosure [Abstract]
Lease cancellation notice period		30 days
Commitment maturing in the next fiscal year		$25,300,000
Other Commitment, Due in Second Year		2,600,000
Lease term expiration date		31-Mar-20
Tenant improvement allowance	3,200,000	127,000	879,000		1,800,000
Early termination right effective date		31-Mar-18
Term of optional lease extension	3 years
Rent expense		$1,200,000	$803,000	$800,000

Future_Minimum_Commitments_Und

Future Minimum Commitments Under our Non-Cancelable Operating Leases (Detail) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Commitments And Contingencies Disclosure [Abstract]
2015	$1,769
2016	2,070
2017	2,134
2018	2,200
2019	2,267
Thereafter	571
Total	$11,011

StockBased_Compensation_Additi

Stock-Based Compensation - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Common stock reserved, shares	935,213
Term of stock options granted		10 years
Vesting period of stock options	2 years 9 months 18 days	4 years
Number of common stock shares reserved for issuance under the 2013 Employee Stock Purchase Plan	6,949,108
Aggregate intrinsic value of options exercised	$12,500,000	$6,300,000	$451,000
Total estimated grant date fair value of options vested	9,000,000	3,800,000	3,000,000
Unamortized share based compensation expected to be recognized over the remaining vesting period	21,800,000
Weighted-average per share fair value of employee options granted	$15.73	$12.46	$5.90
Share based compensation, options weighted average exercise price	$25.96
Incentive Stock Options
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Exercise price of stock options granted as a minimum percentage of fair value of common stock		100.00%
Nonstatutory Stock Options
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Exercise price of stock options granted as a minimum percentage of fair value of common stock		85.00%
10% or more
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Exercise price of stock options granted as a minimum percentage of fair value of common stock		110.00%
Percentage of voting stock		10.00%
Nonemployee Stock Options
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Vesting period of stock options	4 years
Share based compensation, options granted	33,888	32,943	6,380
Share based compensation, options weighted average exercise price	$25.41	$19.88	$7
Stock-based compensation	$769,000	$775,000	$144,000
Employee Stock Purchase Plan
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Exercise price of stock options granted as a minimum percentage of fair value of common stock	85.00%
Number of common stock shares reserved for issuance under the 2013 Employee Stock Purchase Plan	1,000,000
Percentage increase in number of common stock outstanding	2.00%

Summary_of_Stock_Option_Activi

Summary of Stock Option Activity (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014
Shares Available for Grant
Beginning balance	81,948
Options authorized	2,045,785
Options granted	-1,358,013
Options canceled	165,493
Ending balance	935,213
Shares Subject to Outstanding Options
Beginning balance	3,708,773
Options granted	1,358,013
Options exercised	-652,125
Options canceled	-165,493
Ending balance	4,249,168
Weighted-Average Exercise Price Per Share
Beginning balance	$9.43
Options granted	$25.96
Options exercised	$6.68
Options canceled	$18.86
Ending balance	$14.77

Status_of_Options_Detail

Status of Options (Detail) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Shares
Outstanding	4,249,168	3,708,773
Vested and expected to vest	4,106,671
Vested	2,503,676
Weighted-Average Exercise Price Per Share
Outstanding	$14.77	$9.43
Vested and expected to vest	$14.47
Vested	$9.67
Remaining Contractual Life
Outstanding	6 years 7 months 6 days
Vested and expected to vest	6 years 7 months 6 days
Vested	5 years 2 months 12 days
Aggregate Intrinsic Value
Outstanding	$57,709
Vested and expected to vest	57,009
Vested	$46,722

Stock_Options_Outstanding_and_

Stock Options Outstanding and Vested and Exercisable (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Options Outstanding, Number of Options Outstanding	4,249,168	3,708,773
Outstanding	6 years 7 months 6 days
Outstanding	$14.77	$9.43
Options Vested, Number of Options Vested	2,503,676
Options Vested, Weighted Average Exercise Price Per Share	$9.67
$1.00 - $5.10
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices, Lower Limit	$1
Exercise Prices, Upper Limit	$5.10
Options Outstanding, Number of Options Outstanding	945,481
Outstanding	2 years 9 months 18 days
Outstanding	$4.21
Options Vested, Number of Options Vested	945,481
Options Vested, Weighted Average Exercise Price Per Share	$4.21
$5.30 - $9.00
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices, Lower Limit	$5.30
Exercise Prices, Upper Limit	$9
Options Outstanding, Number of Options Outstanding	1,068,191
Outstanding	6 years
Outstanding	$8.07
Options Vested, Number of Options Vested	927,581
Options Vested, Weighted Average Exercise Price Per Share	$8.21
$9.50 - $23.85
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices, Lower Limit	$9.50
Exercise Prices, Upper Limit	$23.85
Options Outstanding, Number of Options Outstanding	976,963
Outstanding	8 years 2 months 12 days
Outstanding	$17.61
Options Vested, Number of Options Vested	406,830
Options Vested, Weighted Average Exercise Price Per Share	$16.81
$24.39 - $26.67
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices, Lower Limit	$24.39
Exercise Prices, Upper Limit	$26.67
Options Outstanding, Number of Options Outstanding	861,050
Outstanding	8 years 7 months 6 days
Outstanding	$25.13
Options Vested, Number of Options Vested	178,702
Options Vested, Weighted Average Exercise Price Per Share	$25.04
$26.75 - $29.19
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices, Lower Limit	$26.75
Exercise Prices, Upper Limit	$29.19
Options Outstanding, Number of Options Outstanding	397,483
Outstanding	9 years 6 months
Outstanding	$28.42
Options Vested, Number of Options Vested	45,082
Options Vested, Weighted Average Exercise Price Per Share	$29.02

Classification_of_StockBased_C

Classification of Stock-Based Compensation Expense (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$9,333	$4,974	$2,809
Research and Development Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	4,551	2,295	1,452
General and Administrative Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$4,782	$2,679	$1,357

Fair_Values_of_Employee_Stock_

Fair Values of Employee Stock Options (Detail) (Employee Stock Option)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate		1.43%	1.10%
Risk-free interest rate, minimum	1.81%
Risk-free interest rate, maximum	1.89%
Expected life	6 years	6 years	6 years
Expected volatility		79.00%	72.00%
Expected volatility, minimum	69.00%
Expected volatility, maximum	80.00%

Fair_Value_of_ESPP_Purchase_Ri

Fair Value of ESPP Purchase Rights Granted (Detail) (Employee Stock Purchase Plan)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Employee Stock Purchase Plan
Share Based Compensation Arrangement Assumptions Used To Estimate Fair Values Of Share Options Granted [Line Items]
Risk-free interest rate	0.08%	0.10%
Expected life	6 months	4 months 24 days
Expected volatility	73.00%	62.00%

Outstanding_Shares_of_Common_S

Outstanding Shares of Common Stock Excluded from Computation of Diluted Net Loss per Share (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 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
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	4,249,168	3,708,773	1,653,298
Convertible 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
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	6,240	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								12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share [Abstract]
Net (loss) income	($39,256)	($35,793)	($31,350)	($30,726)	($25,062)	($18,550)	($21,598)	($18,142)	($137,125)	($83,352)	$11,366
Noncumulative dividends on convertible preferred stock											-11,366
Net loss attributable to common stockholders, basic									-137,125	-83,352
Net loss attributable to common stockholders, diluted									($137,125)	($83,352)
Shares used to compute net (loss) income per share attributable to common stockholders:
Weighted average common shares outstanding									42,977,463	22,842,443	1,350,939
Weighted average effect of dilutive stock options											697,928
Weighted average number of shares outstanding, diluted shares									42,977,463	22,842,443	2,048,867
Net loss per share attributable to common stockholders:
Basic									($3.19)	($3.65)
Diluted									($3.19)	($3.65)

Employee_Benefit_Plan_Addition

Employee Benefit Plan - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Compensation And Retirement Disclosure [Abstract]
Defined contribution plan maximum annual employer matching contribution per employee	$2,000	$500	$500
Employee benefit plans, contribution expense	$153,000	$59,000	$31,000

Reconciliation_of_Effective_Ta

Reconciliation of Effective Tax Rate for the Provision for Income Taxes (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Abstract]
Federal statutory income tax rate	34.00%	34.00%	34.00%
State income taxes, net of federal benefit	11.20%	0.40%	22.80%
Federal and state research credits	2.70%	3.40%	0.80%
Stock based compensation	-1.60%	-0.20%	0.40%
Other	-0.10%	-0.50%	-0.10%
Change in valuation allowance	-46.20%	-37.10%	-57.90%
Effective income tax rate	0.00%	0.00%	0.00%

Significant_Components_of_Defe

Significant Components of Deferred Tax Assets (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Deferred tax assets:
Federal and state net operating loss carryforwards	$146,725	$102,478
Federal and state research tax credit carryforwards	15,337	10,750
Deferred revenue	12,523	1,755
Stock options	3,776	2,895
Capitalized acquisition costs	1,322	1,295
Other	3,589	654
Total deferred tax assets	183,272	119,827
Valuation allowance	-183,272	-119,827
Net deferred tax assets	$0	$0

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax [Line Items]
Increase (Decrease) in valuation allowance	$63,500,000	$30,700,000
Unrecognized income tax benefits that, if recognized, would affect effective tax rate	365,000	365,000
Unrecognized income tax benefits	2,906,000	2,048,000	1,435,000	1,344,000
Unrecognized Tax Benefits, Period Increase (Decrease)	-365,000
Minimum
Income Tax [Line Items]
Federal research tax credits, expiration year	2024
Maximum
Income Tax [Line Items]
Federal research tax credits, expiration year	2034
Earliest Tax Year
Income Tax [Line Items]
Tax years remain open to examinations	2003
Latest Tax Year
Income Tax [Line Items]
Tax years remain open to examinations	2013
Federal
Income Tax [Line Items]
Net operating loss carryforwards	364,400,000
Federal | Research Tax Credit Carryforward
Income Tax [Line Items]
Tax credits carryforwards	15,200,000
California
Income Tax [Line Items]
Net operating loss carryforwards	449,600,000
California | Minimum
Income Tax [Line Items]
Net operating loss carryforwards, expiration year	2018
California | Maximum
Income Tax [Line Items]
Net operating loss carryforwards, expiration year	2034
California | Research Tax Credit Carryforward
Income Tax [Line Items]
Tax credits carryforwards	$3,800,000

Reconciliation_of_the_Beginnin

Reconciliation of the Beginning and Ending Amount of Unrecognized Tax Benefits (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation Of Unrecognized Tax Benefits Excluding Amounts Pertaining To Examined Tax Returns Roll Forward
Unrecognized tax benefits, beginning of period	$2,048	$1,435	$1,344
Gross increases - current period tax positions	858	619	91
Gross decreases - tax position in prior period		-6
Unrecognized tax benefits, end of period	$2,906	$2,048	$1,435

Related_Party_Transactions_Add

Related Party Transactions - Additional Information (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Related Party Transaction [Line Items]
Receivables from related parties	$40	$394
Chief Executive Officer | Master Services Agreement
Related Party Transaction [Line Items]
Reduction in research and development expense	$594	$816	$57

Subsequent_Events_Additional_I

Subsequent Events - Additional Information (Detail) (USD $)	12 Months Ended		1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Jan. 31, 2015
Subsequent Event [Line Items]
Vesting period of stock options	2 years 9 months 18 days	4 years
Subsequent
Subsequent Event [Line Items]
Vesting period of stock options			4 years
Executive officers (PSU) awards			The Compensation Committee of the Board approved for Portola’s named executive officers performance stock unit (PSU) awards. Each PSU represents a contingent right to receive one share of Issuer’s Common Stock
Subsequent | First Half Shares
Subsequent Event [Line Items]
Average closing price per share when market is above			50
Consecutive trading days			45 days
Subsequent | Additional Half Shares
Subsequent Event [Line Items]
Average closing price per share when market is above			60
Consecutive trading days			45 days

Quarterly_Financial_Informatio

Quarterly Financial Information (Detail) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Data [Abstract]
Collaboration and license revenue	$2,411	$2,427	$2,415	$2,372	$2,056	$2,766	$2,601	$3,108	$9,625	$10,531	$72,042
Operating expenses	-41,671	-38,204	-33,920	-33,396	-27,412	-21,995	-24,541	-20,761	-147,191	-94,709	-61,186
Net (loss) income	($39,256)	($35,793)	($31,350)	($30,726)	($25,062)	($18,550)	($21,598)	($18,142)	($137,125)	($83,352)	$11,366
Net loss per share:
Basic and diluted	($0.82)	($0.86)	($0.76)	($0.75)	($0.63)	($0.53)	($1.47)	($12.94)