Portola Pharmaceuticals (PTLA) 10-K 29 Feb 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Feb. 22, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Trading Symbol	PTLA
Entity Registrant Name	PORTOLA PHARMACEUTICALS INC
Entity Central Index Key	1,269,021
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 1,260
Entity Common Stock, Shares Outstanding		56,362,311

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands		Dec. 31, 2015		Dec. 31, 2014
Current assets:
Cash and cash equivalents		$ 186,488	[1]	$ 57,514
Short-term investments		257,713	[1]	251,759
Restricted cash (Development Partner)	[1]	341
Receivables from collaborators		1,000	[1]	57
Prepaid research and development		16,976	[1]	1,686
Prepaid expenses and other current assets		3,059	[1]	4,061
Total current assets		465,577	[1]	315,077
Property and equipment, net		6,243	[1]	2,776
Intangible asset	[1]	3,151
Long-term investments		15,960	[1]	83,030
Prepaid and other long-term assets		11,993	[1]	15,612
Total assets		502,924	[1]	416,495
Current liabilities:
Accounts payable		10,279	[1]	14,084
Accrued compensation and employee benefits		5,459	[1]	3,512
Accrued research and development		24,195	[1]	12,545
Accrued and other liabilities		2,826	[1]	1,421
Deferred revenue, current portion		8,387	[1]	9,569
Total current liabilities		51,146	[1]	41,131
Deferred revenue, long-term		18,629	[1]	27,016
Other long-term liabilities		2,826	[1]	546
Total liabilities		$ 72,601	[1]	$ 68,693
Stockholders’ equity:
Preferred stock, $0.001 par value, 5,000,000 shares authorized; no shares issued and outstanding			[1]
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		$ 57	[1]	$ 49
Additional paid-in capital		1,076,791	[1]	770,789
Accumulated deficit		(649,302)	[1]	(422,797)
Accumulated other comprehensive income/(loss)		(150)	[1]	(239)
Total Portola stockholders’ equity		427,396	[1]	347,802
Noncontrolling interest (Development Partner)	[1]	2,927
Total stockholders' equity		430,323	[1]	347,802
Total liabilities and stockholders’ equity		$ 502,924	[1]	$ 416,495
[1]	Amounts include the assets and liabilities of a consolidated variable interest entity (“VIE”). Portola's interests and obligations with respect to the VIE's assets and liabilities are limited to those accorded to Portola in its agreement with the VIE. See Note 8, “Asset Acquisition and License Agreements,” to these consolidated financial statements.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	56,359,515	48,766,806
Common stock, shares outstanding	56,359,515	48,766,806

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
Collaboration and license revenue	$ 12,070,000	$ 9,625,000	$ 10,531,000
Operating expenses:
Research and development	200,376,000	123,639,000	79,286,000
Selling, general and administrative	38,869,000	23,552,000	15,423,000
Total operating expenses	239,245,000	147,191,000	94,709,000
Loss from operations	(227,175,000)	(137,566,000)	(84,178,000)
Interest and other income, net	305,000	441,000	826,000
Loss before taxes	(226,870,000)	(137,125,000)	(83,352,000)
Income tax benefit	365,000	0	0
Net loss	(226,505,000)	(137,125,000)	(83,352,000)
Net loss attributable to Portola	$ (226,505,000)	$ (137,125,000)	$ (83,352,000)
Net loss per share attributable to Portola common stockholders:
Basic and diluted	$ (4.36)	$ (3.19)	$ (3.65)
Shares used to compute net loss per share attributable to Portola common stockholders:
Basic and diluted	51,981,463	42,977,463	22,842,443

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (226,505)	$ (137,125)	$ (83,352)
Other comprehensive income:
Unrealized gain on available-for-sale securities, net of tax	89	(294)	22
Comprehensive loss	226,416	137,419	83,330
Total comprehensive loss attributable to Portola	$ (226,416)	$ (137,419)	$ (83,330)

Consolidated Statements of Conv

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands		Total		IPO	Follow-on Offering	Convertible Preferred Stock	Common Stock	Common StockIPO	Common StockFollow-on Offering	Additional Paid-In Capital	Additional Paid-In CapitalIPO	Additional Paid-In CapitalFollow-on Offering	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interest (Development Partner)
Balance at beginning of year at Dec. 31, 2012		$ (191,569)				$ 317,280	$ 1			$ 10,717			$ (202,320)	$ 33
Balance at beginning of year (in shares) at Dec. 31, 2012						24,026,797	1,385,508
Exercise of employee stock options for cash		2,529								2,529
Exercise of employee stock options for cash (in shares)							403,468
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 on available-for-sale securities, net of tax		22												22
Net loss		(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		4,399					$ 1			4,398
Exercise of employee stock options for cash (in shares)							652,125
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 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 on available-for-sale securities, net of tax		(294)												(294)
Net loss		(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
Balance at end of the year at Dec. 31, 2014		347,802
Exercise of employee stock options for cash		$ 11,111					$ 1			11,110
Exercise of employee stock options for cash (in shares)		1,095,486					1,095,486
Lapse of repurchase rights related to common shares issued pursuant to early exercises (in shares)							125
Issuance of common stock upon cashless exercise of common stock warrants (shares)							3,041
Issuance of common stock pursuant to ESPP purchase (in shares)							30,307
Issuance of common stock pursuant to ESPP purchase		$ 837					$ 1			836
Issuance of stock (in shares)								6,463,750
Issuance of stock				$ 271,096				$ 6			$ 271,090
Employee stock-based compensation expense		20,172								20,172
Compensation expense relating to stock options granted to consultants		2,794								2,794
Unrealized gain on available-for-sale securities, net of tax		89												89
Consolidation of variable interest entity		2,927													$ 2,927
Net loss		(226,505)											(226,505)
Balance at end of the year at Dec. 31, 2015	[1]	427,396
Balance at end of the year (in shares) at Dec. 31, 2015							56,359,515
Balance at end of the year at Dec. 31, 2015		$ 430,323	[1]				$ 57			$ 1,076,791			$ (649,302)	$ (150)	$ 2,927
[1]	Amounts include the assets and liabilities of a consolidated variable interest entity (“VIE”). Portola's interests and obligations with respect to the VIE's assets and liabilities are limited to those accorded to Portola in its agreement with the VIE. See Note 8, “Asset Acquisition and License Agreements,” to these consolidated financial statements.

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015		Dec. 31, 2014	Dec. 31, 2013
Operating activities
Net loss	$ (226,505)		$ (137,125)	$ (83,352)
Adjustments to reconcile net loss to cash used in operating activities:
Depreciation and amortization	1,311		1,542	1,359
Amortization of premium on investment securities	3,174		3,703	2,333
Stock-based compensation expense	22,858		9,333	4,974
Change in reserve for uncertain tax position	(365)
Revaluation of convertible preferred stock warrant liability				(24)
Unrealized (gain) loss on foreign currency forward contracts			114	(261)
Changes in operating assets and liabilities:
Receivables from collaborations	(943)		252	353
Prepaid research and development	(15,290)		(745)	718
Prepaid expenses and other current assets	1,001		(1,383)	(1,187)
Prepaid and other long-term assets	3,619		(15,559)	396
Accounts payable	(4,061)		10,763	(1,773)
Accrued compensation and employee benefits	2,054		893	650
Accrued research and development	11,650		(3,565)	12,742
Accrued and other liabilities	1,531		(261)	(834)
Deferred revenue	(9,569)		31,374	1,169
Other long-term liabilities	2,281		(42)	(878)
Net cash used in operating activities	(207,252)		(100,706)	(63,615)
Investing activities
Purchases of property and equipment	(4,746)		(1,629)	(933)
Increase in restricted cash (Development Partner)	(341)
Purchases of investments	(266,068)		(332,171)	(219,813)
Proceeds from sales of investments			2,603	8,009
Proceeds from maturities of investments	324,100		192,045	92,001
Net cash provided by/ (used in) investing activities	52,945		(139,152)	(120,736)
Financing activities
Proceeds from public offering of common stock, net of underwriters discount	272,216		175,185	251,865
Payment of public offering costs	(882)		(564)	(5,883)
Proceeds from issuance of common stock pursuant to equity award plans	11,948		4,978	2,529
Net cash provided by financing activities	283,282		179,599	248,511
Net increase (decrease) in cash and cash equivalents	128,974		(60,259)	64,160
Cash and cash equivalents at beginning of year	57,514		117,773	53,613
Cash and cash equivalents at end of year	186,488	[1]	57,514	117,773
Noncash investing and financing activities:
Net change in accrued offering cost	238
Net change in accounts payable related to purchase of property and equipment	$ 5		$ 89	$ 165
[1]	Amounts include the assets and liabilities of a consolidated variable interest entity (“VIE”). Portola's interests and obligations with respect to the VIE's assets and liabilities are limited to those accorded to Portola in its agreement with the VIE. See Note 8, “Asset Acquisition and License Agreements,” to these consolidated financial statements.

Organization

Organization	12 Months Ended
	Dec. 31, 2015
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 Phase 3 programs address significant unmet medical needs in the area of thrombosis, or blood clots. Betrixaban, a U.S. Food and Drug Administration, or FDA, designated Fast-Track novel oral once-daily inhibitor of Factor Xa, or fXa, is in a Phase 3 clinical trial for extended duration prophylaxis, or preventive treatment, of a form of thrombosis known as venous thromboembolism, or VTE, in acute medically ill patients for 35 days of in-hospital and post-discharge use. Our second Phase 3 compound, Andexanet alfa, an FDA-designated breakthrough therapy and orphan drug, is a recombinant protein designed to reverse anticoagulant activity in patients treated with a fXa inhibitor. Our third product candidate, Cerdulatinib, is an orally available dual kinase inhibitor that inhibits spleen tyrosine kinase, or Syk, and janus kinases, or JAK, enzymes that regulate important signaling pathways. Cerdulatinib is being developed for hematologic, or blood, cancers and inflammatory disorders. We also have a program of highly selective Syk inhibitors, one of which is partnered with Ora, Inc., or Ora. 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. In March 2015, we completed an underwritten public offering of 2,870,000 shares of our Common Stock, which included 374,348 shares of Common Stock issued pursuant to the over-allotment option granted to our underwriters, at a public offering price of $40.00 per share. The net proceeds from the offering to us including the over-allotment option, net of underwriting discounts, commissions and offering expenses of approximately $358,000, were approximately $108.4 million. In December 2015, we completed an underwritten public offering of 3,593,750 shares of our Common Stock, which included 468,750 shares of Common Stock issued pursuant to the over-allotment option granted to our underwriters, at a public offering price of $48.00 per share. The net proceeds from the offering to us including the over-allotment option, net of underwriting discounts, commissions and offering expenses of approximately $765,000 were approximately $162.7 million.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
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 subsidiaries and a Development Partner that is a variable interest entity (a “VIE”) for which Portola is deemed, under applicable accounting guidance to be the primary beneficiary as of December 31, 2015. For the consolidated VIE, we record net loss attributable to noncontrolling interests in our Consolidated Statements of Operations equal to the percentage of the economic or ownership interest retained in such VIE by the respective noncontrolling parties. Reclassification Prepaid expenses and other current assets in the prior year Consolidated Balance Sheet of $5.7 million have been reclassified to $1.7 million and $4.0 million in Prepaid research and development and Prepaid expenses and other current assets, respectively, and Accrued and other liabilities in the prior year Consolidated Balance Sheet of $14.0 million has been reclassified to $12.6 million and $1.4 million in Accrued research and development and Accrued and other liabilities, respectively, to conform to current-period presentation. Corresponding changes in Changes in operating assets and liabilities within the Consolidated Statement of Cash Flows have been adjusted to conform to these reclassifications. Use of Estimates The preparation of consolidated 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 liabilities and the reported amounts of revenues and expenses in the consolidated 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, in-process research and development , the consolidation of VIEs and deconsolidation of VIEs 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 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. In-process Research and Development Asset In-process research and development asset relates to our consolidated VIE and are considered to be indefinite-lived until the completion or abandonment of the associated R&D efforts which generally occurs if and when regulatory approval to market a product is obtained, 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 in Marketable Securities All investments in marketable securities 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. 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 biologics drug application (BLA) or 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. Collaboration Customer Concentration Collaboration customers who accounted for 10% or more of total collaboration and license revenues were as follows: Year Ended December 31, 2015 2014 2013 Bayer Pharma, AG and Janssen Pharmaceuticals, Inc. 48% 37% 37% Daiichi Sankyo, Inc. 38% 45% 23% Bristol-Myers Squibb Company and Pfizer Inc. 13% 16% 38% 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 for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Specific potential indicators of impairment include a significant decrease in the fair value of an asset, a significant change in the extent or manner in which an asset is used or a significant physical change in an asset, a significant adverse change in legal factors or in the business climate that affects the value of an asset, an adverse action or assessment by the FDA or another regulator or a projection or forecast that demonstrates continuing losses associated with an income producing asset. 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 Employee stock-based compensation cost is measured at the grant date, based on the fair value of the award. The compensation cost is recognized as expense on a straight-line basis over the vesting period for options and restricted stock units (“RSUs”) and on an accelerated basis for market-based performance stock units (“M-PSUs”) and performance-based performance stock units (“PSUs”). For stock option grants, we use the Black-Scholes option pricing model to determine the fair value of stock options. This model requires us to make assumptions such as expected term, dividends, volatility and forfeiture rates that determine the stock options fair value. These key assumptions are based on peer companies compared to historical information and judgment regarding market factors and trends. If actual results are not consistent with our assumptions and judgments used in estimating these factors, we may be required to increase or decrease compensation expense, which could be material to its results of operations. For M-PSU awards, we use the Monte-Carlo option pricing model to determine the fair value of awards at the date of issue. The Monte-Carlo option-pricing model uses similar input assumptions as the Black-Scholes model; however, it further incorporates into the fair-value determination the possibility that the performance-based market condition may not be satisfied. Compensation costs related to awards with a market-based condition are recognized regardless of whether the market condition is ultimately satisfied. Compensation cost is not reversed if the achievement of the market condition does not occur. For RSUs and PSU awards, we base the fair value of awards on the closing market value of our common stock at the date of grant. 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 basis 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 financial transactions denominated in foreign currencies, primarily the Euro and British Pound, and, as a result, are exposed to changes in foreign currency exchange rates. We manage a portion of these cash flow exposures through purchasing and holding of Euros and British Pounds 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 currency deposits we hold are remeasured using period end spot rates. Foreign currency forward contracts are marked to market at the end of each period and recorded as gains and losses in the condensed consolidated statements of operations. We held no foreign currency forward contracts at December 31, 2015 or December 31, 2014. We recorded an unrealized loss of $114,000 in interest and other income (expense), net in our consolidated statements of operations related to foreign currency forward contracts for the year ended December 31, 2014. 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. Net Loss per Share Attributable to Portola Common Stockholders Basic net loss per share attributable to Portola Common Stockholders is calculated by dividing the net loss attributable to Portola Common Stockholders by the weighted-average number of shares of Common Stock outstanding for the period. Diluted net loss per share attributable to Portola Common Stockholders is computed by giving effect to all potential dilutive Common Stock equivalents outstanding for the period. Diluted net loss per share attributable to Portola Common Stockholders is the same as basic net loss per share attributable to Portola Common Stockholders, since the effects of potentially dilutive securities are antidilutive. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (the “FASB”), jointly with the International Accounting Standards Board, issued ASU 2014-09, Revenue from Contracts with Customers In February 2015, the Financial Accounting Standards Board (the “FASB”) issued ASU 2015-02, Consolidation: amendment to the consolidation analysis In November 2015, the Financial Accounting Standards Board (“FASB”) issued ASU 2015-17, Income Taxes (Topic740): Balance Sheet Classification of Deferred Taxes

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2015
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 research and development prepaid expenses and other current assets and accounts payable, accrued research and development, 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. Treasuries and government agency securities and foreign currency forward contracts as Level 2. 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. 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 noncontrolling interest (Development Partner) includes the fair value of the contingent milestone and royalty payments, which is valued based on Level 3 inputs. Please refer to Note 8, "Asset Acquisition and License Agreements," for further information. The following table sets forth the fair value of our financial assets and liabilities (excluding consolidated VIE’s cash), allocated into Level 1, Level 2 and Level 3, that was measured on a recurring basis (in thousands): December 31, 2015 Level 1 Level 2 Level 3 Total Financial Assets: Money market funds $ 22,074 $ – $ – $ 22,074 Corporate notes and commercial paper – 242,033 – 242,033 U.S. government agency securities – 180,876 – 180,876 Total financial assets $ 22,074 $ 422,909 $ – $ 444,983 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

Financial Instruments

Financial Instruments	12 Months Ended
	Dec. 31, 2015
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, 2015 December 31, 2014 Estimated Estimated Unrealized Unrealized Fair Unrealized Unrealized Fair Cost Gains (Losses) Value Cost Gains (Losses) Value Money market funds $ 22,074 $ – $ – $ 22,074 $ 24,915 $ – $ – $ 24,915 Corporate notes and commercial paper 242,089 3 (59 ) 242,033 226,209 8 (170 ) 226,047 U.S. government agency securities 180,970 1 (95 ) 180,876 120,246 4 (81 ) 120,169 $ 445,133 $ 4 $ (154 ) $ 444,983 $ 371,370 $ 12 $ (251 ) $ 371,131 Classified as: Cash equivalents $ 171,310 $ 36,341 Short-term investments 257,713 251,759 Long-term investments 15,960 83,030 Total cash equivalents and investments $ 444,983 $ 371,131 At December 31, 2015, 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, 2015 and 2014.

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Dec. 31, 2015
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	5. Balance Sheet Components Property and Equipment Property and equipment consists of the following (in thousands): December 31, 2015 2014 Computer equipment $ 960 $ 734 Capitalized software $ 865 674 Equipment $ 5,874 4,852 Leasehold improvements $ 7,529 4,217 15,228 10,477 Less accumulated depreciation and amortization (8,985 ) (7,701 ) Property and equipment, net $ 6,243 $ 2,776 Accrued and Other Liabilities Accrued and other liabilities consist of the following (in thousands): December 31, 2015 2014 Commercial related $ 783 $ – Legal and accounting fees 506 354 Deferred rent 721 127 Other 816 940 Total accrued liabilities $ 2,826 $ 1,421

Collaboration and License Agree

Collaboration and License Agreements	12 Months Ended
	Dec. 31, 2015
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Collaboration and License Agreements	6. 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, 2015 2014 2013 Bayer and Janssen $ 5,740 $ 3,598 $ 3,876 Daiichi Sankyo 4,578 4,287 2,419 BMS and Pfizer 1,540 1,497 4,042 Lee's Pharmaceutical 212 243 194 Total collaboration and license revenue $ 12,070 $ 9,625 $ 10,531 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 fXa 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, 2015, 2014 and 2013, we recognized $500,000, $1.1 million and $3.9 million in collaboration revenue, respectively. There was no deferred revenue balance under this agreement as of December 31, 2015 or 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 fXa 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. For the year ended December 31, 2015, we recognized $2.0 million in collaboration revenue associated with achievement of a milestone. As of December 31, 2014, no amounts had been recognized as collaboration revenue for any of these milestones. The contingent 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. All remaining contingent payments remained eligible for achievement as of December 31, 2015. During the years ended December 31, 2015 and 2014, we recognized $5.2 million and $2.5 million in collaboration revenue under this agreement, respectively. The deferred revenue balance under this agreement as of December 31, 2015 and 2014 was $7.2 million and $10.5 million, respectively. Daiichi Sankyo, Inc. (“Daiichi Sankyo”) In June 2013, we entered into an agreement with Daiichi Sankyo to include subjects dosed with edoxaban, their fXa 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 years ended December 31, 2015, 2014 and 2013, we recognized $1.0 million, $2.5 million and $2.4 million in collaboration revenue associated with the contingent and the non-contingent element of the arrangement, respectively. There was no deferred revenue balance under this agreement as of December 31, 2015. 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 fXa 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, 2015, no amounts had been recognized as collaboration revenue for any of these milestones. All of the contingent payments remain eligible for achievement as of December 31, 2015. 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 years ended December 31, 2015 and 2014 we recognized $3.5 million $1.8 million in collaboration revenue under this agreement, respectively. The deferred revenue balance under this agreement as of December 31, 2015 and 2014 was $9.7 million and $13.2 million, respectively. 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 we recognized $4.0 million in collaboration revenue. 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 fXa 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 five contingent payments totaling $12.0 million 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 payments had been received at December 31, 2015. Four of the contingent payments totaling $7.5 million remain eligible for payment as of December 31, 2015. During the years ended December 31, 2015 and 2014 we recognized $1.5 million and $1.5 million in collaboration revenue under this agreement, respectively. The deferred revenue balance under this agreement as of December 31, 2015 and 2014 was $8.4 million and $11.5 million, respectively. 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 agreed to reimburse our costs in connection with the expansion of the APEX study into China. Lee’s contracted to 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 years ended December 31, 2015, 2014 and 2013, we recognized $212,000, $243,000 and $194,000 in collaboration revenue under this agreement, respectively. The deferred revenue balance as of December 31, 2015 and 2014 was $52,000 and $263,000, respectively. Ora, Inc. (“Ora”) In May 2015, we entered into a license and collaboration agreement with Ora pursuant to which we granted Ora an exclusive license to co-develop and co-commercialize one of our specific Syk inhibitors, PRT2761. Ora has the primary responsibility for conducting the research and development and regulatory 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. Under the terms of this risk and cost sharing agreement, each party will incur its own share of development costs. Third-party related development costs will be shared by Ora and us at approximately 60% and 40%, respectively, until an End of Phase 2 meeting with the FDA, and equally thereafter. We are entitled to receive either 50% of the profits, if any, generated by future sales of the products developed under the agreement or royalty payments on such sales, should we opt out of the agreement. We may opt out of the agreement any time prior to 90 days after an End of Phase 2 meeting with the FDA. The timing of the exercise of our opt out rights would impact future royalties we would be entitled to receive from Ora. Each party may also buy out the rights and interests in the licensed compound by paying the greater of $6.0 million or two times the actual aggregate development cost incurred by both parties before or 90 days after an End of Phase 2 meeting with the FDA. All costs we incur in connection with this agreement will be recognized as research and development expenses. During the year ended December 31, 2015, costs of $206,000 have been incurred related to this agreement. Biogen Idec, Inc. (“Biogen Idec”) In October 2011, we entered into an exclusive, worldwide license and collaboration agreement with Biogen Idec to develop and commercialize selective, novel oral Syk inhibitors for the treatment of autoimmune and inflammatory diseases. In November 2012, we exercised our option to convert the agreement to a fully out-licensed agreement. After the election, we relinquished our right to share profits from sales of products related to PRT2607 and other selective Syk inhibitors, but were entitled to receive future payments up to approximately $370.0 million based on the occurrence of certain development and regulatory events for all licensed compounds. 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 and we would be required to pay Biogen Idec $15.0 million upon the completion of certain commercial milestones and pay royalties on sales of products approved for the Syk inhibitor. In May 2015, our agreement with Biogen Idec terminated in its entirety, effective July 2015. The effect of termination resulted in return to us of all compounds subject to the license and collaboration agreement and eliminated all potential future payments from and to Biogen Idec. We did not record any reduction to research and development expense pursuant to the agreement for the year ended December 31, 2015. During the years ended December 31, 2014 and 2013 we recorded reductions in research expense of $210,000 and $804,000 respectively. 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 2015, 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, 2015, there has been no change to our agreement with Aciex.

Commercial Supply Agreement

Commercial Supply Agreement	12 Months Ended
	Dec. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Commercial Supply Agreement	7. 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 $276.1 million. Payments made for purchase of batches since inception of this agreement as of December 31, 2015 amount to $29.0 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 $5.0 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, 2015, we have not provided financial, or other, support to CMC Biologics that was not previously contractually required. The upfront and reservation payment of $14.6 million is recorded as $11.4 million in prepaid and other long-term assets and $2.9 million in prepaid research and development in the consolidated balance sheet, net of amortization. The unamortized payments made for purchases of batches of $13.0 million are recorded in prepaid research and development in the consolidated balance sheet. These assets represent our maximum exposure to loss under this agreement at December 31, 2015. The upfront payment will be charged to research and development expense, prior to regulatory approval of Andexanet alfa, as batches are delivered. We are currently not able to quantify the exposure to losses associated with the fixed pricing terms of this agreement.

Asset Acquisition and License A

Asset Acquisition and License Agreements	12 Months Ended
	Dec. 31, 2015
Research And Development [Abstract]
Asset Acquisition and License Agreements	8. Asset Acquisition and License Agreements Agreement with Early Development Stage Company (“Development Partner”) In December 2015, we entered into an agreement with an early development stage limited liability company to explore a novel approach to develop a drug in the field of hypercholesterolemia. We plan to advance the program in collaboration with the Development Partner through an agreed-upon development plan and are obligated to fund the development effort over the initial term of the arrangement expected to be through August 2016. At the time of entry into the agreement, we determined that the Development Partner was a variable interest entity and we held a variable interest in the Development Partner’s intellectual property assets and the related potential future product candidates these assets may produce. Due to the absence of other significant development programs at the Development Partner, we concluded that the variable interest was in the entity as a whole and not the intellectual property assets. Given the stage of development, we concluded that Development Partner was considered not to be a business as they lacked the processes required to generate outputs. As we are primarily funding and have the power to unilaterally amend the development plan during the initial term and thus control those activities most significant to the Development Partner, we concluded that we are the primary beneficiary of the Development Partner. Accordingly, the Development Partner is subject to consolidation and we have consolidated the financial statements of the Development Partner since inception of the agreement on December 1, 2015 by (a) eliminating all intercompany balances and transactions; (b) allocating loss attributable to the noncontrolling interest in the Development Partner to net loss attributable to noncontrolling interest in our consolidated statement of operations and reflecting noncontrolling interest on our consolidated balance sheet. Our interest in the Development Partner is limited to the development of the intellectual property asset. The upfront payment of $500,000 and the obligation to fund the development plan represent our maximum exposure to loss under the agreement. At the inception of the agreement, the identifiable assets, assumed liabilities and non-controlling interest of the Development Partner were recorded at their estimated fair value upon the initial consolidation of the Development Partner, including the intellectual property assets. We estimated the fair value of the intellectual property assets to be $3.2 million and the noncontrolling interest to be $2.9 million. The fair value were estimated using present-value models on potential contingent milestones and royalty payments, based on assumptions regarding the probability of achieving the development milestones, estimate of time to develop the drug candidate, estimates of future cash flows from potential product sales and assumptions regarding the appropriate discount rate. As of December 31, 2015 we have recorded $2.9 million as the estimated fair value of the Development Partner’s non-controlling interest, $3.2 million as the estimated fair value of In-process research and development and $341,000 of restricted cash in connection with the consolidation of the Development Partner. As of December 31, 2015, we have not provided financial or other support to the Development Partner that was not previously contracted or required. We recorded Development Partner’s cash as restricted cash because (a) we do not have any interest in or control over Development Partner 's cash and (b) the agreement does not provide for these assets to be used for the development of the intellectual property assets developed pursuant to this agreement. Also, as we are funding the development effort since inception of the arrangement, we have not allocated any net loss to the noncontrolling interest. 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 fXa 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 fXa 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.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. 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 7 amount to $33.2 million, $8.1 million and $685,000 in services to be performed in 2016, 2017 and 2018 respectively. Facility Leases We lease our corporate, laboratory and other facilities under an operating lease, which has been subject to several amendments necessary to secure additional space and extend the lease term through March 2020. These amendments provided for aggregate tenant improvement allowances of $6.3 million, which are amortized as a reduction to rent expense on a straight-line basis over the lease term. The facility lease agreement, as amended, provide for an early termination right effective March 2018 with nine months advance notice and a termination fee of $1.0 million. The facility lease agreement, as amended, contains scheduled rent increases over the lease 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, 2015, our future minimum commitments under our non-cancelable operating leases were as follows (in thousands): Year ending December 31: 2016 $ 2,525 2017 2,603 2018 2,683 2019 2,764 2020 696 Total $ 11,271 Rent expense was $1.7 million, $1.2 million and $803,000 for the years ended December 31, 2015, 2014 and 2013, 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, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Based Compensation	10. 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 the closing of our IPO in May 2013. As of December 31, 2015, we are authorized to issue 9,387,452 shares of common stock under the 2013 Plan. The 2013 Plan had 1,422,745 shares of common stock available for future issuance as of December 31, 2015, subject to automatic annual increases each January 1st and will continue through January 1, 2023. The automatic annual share increase is equal to 5 % of the total number of outstanding shares of our common stock on December 31st of the preceding fiscal year, unless the Board of Directors elects to forego or reduce such increase. 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 appreciation rights, restricted stock awards, restricted stock unit awards, performance stock awards, performance cash awards and other stock awards to employees, officers, directors and consultants. Stock Options 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. The following table summarizes stock option activity, under our 2013 Plan and related information: Shares Subject to Weighted- Outstanding Average Exercise Stock Options Price Per Share Balance at December 31, 2014 4,249,168 $ 14.77 Options granted 1,815,991 38.33 Options exercised (1,095,486 ) 10.14 Options canceled (238,190 ) 26.26 Balance at December 31, 2015 4,731,483 $ 24.19 Additional information related to the status of stock options at December 31, 2015, is as follows (aggregate intrinsic value in thousands): Weighted- Average Remaining Exercise Price Contractual Aggregate Shares Per Share Life Intrinsic Value Outstanding 4,731,483 $ 24.19 7.3 $ 128,996 Vested and expected to vest 4,543,051 $ 23.73 7.2 $ 125,964 Vested 2,341,265 $ 14.92 5.6 $ 85,533 The aggregate intrinsic values of stock options outstanding and exercisable, vested and expected to vest were calculated as the difference between the exercise price of the stock options and the fair value of our common stock as of December 31, 2015. The aggregate intrinsic value of stock options exercised was $35.9 million, $12.5 million and $6.3million for the years ended December 31, 2015, 2014 and 2013, respectively. The total estimated grant date fair value of stock options vested during the years ended December 31, 2015, 2014 and 2013 was $12.0 million, $9.0 million and $3.8 million, respectively. As of December 31, 2015, total unamortized employee and nonemployee stock-based compensation was $42.4 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 stock options granted during the years ended December 31, 2015, 2014 and 2013 was $22.84, $15.73 and $12.46 per share, respectively. Additional information regarding our stock options outstanding and vested and exercisable as of December 31, 2015 is summarized below: Stock Options Outstanding Stock Options Vested Weighted Average Weighted Number Weighted Number of Remaining Average of Average Stock Options Contractual Exercise Price Stock Options Exercise Price Exercise Prices Outstanding Life (Years) per Share Vested Per Share $3.30 - $5.10 495,133 2.4 $ 4.55 495,133 $ 4.55 $5.30 - $9.00 767,038 4.9 8.18 743,033 8.21 $9.50 - $22.16 483,519 7.3 15.29 321,529 14.88 $22.60-$25.00 330,676 7.9 23.95 162,964 23.95 $25.08-$25.08 523,124 8.0 25.08 251,396 25.08 $25.14-$29.19 522,962 8.7 27.57 170,511 27.83 $29.72-$29.72 542,160 8.8 29.72 127,311 29.72 $35.69-$44.39 578,896 9.0 40.82 53,971 42.84 $44.63 - $51.45 479,225 9.5 47.71 14,506 47.21 $52.74 - $52.74 8,750 9.6 52.74 911 52.74 4,731,483 7.3 $ 24.19 2,341,265 $ 14.92 Restricted stock units In January 2015, the Compensation Committee of our Board of Directors approved the commencement of granting restricted stock units to our employees. RSUs are share awards that entitle the holder to receive freely tradable shares of our Common Stock upon vesting. The RSUs cannot be transferred, and until they vest, the awards are subject to forfeiture if employment terminates prior to the release of the vesting restrictions. The RSUs, generally vest equal amounts on each of the first three year anniversaries of the grant date, provided the employee remains continuously employed with us. The fair value of the RSUs is equal to the closing price of our Common Stock on the grant date. The following table summarizes RSU activity, under our 2013 Plan and related information: Shares Subject to Weighted- Outstanding Average grant RSU's fair value per share Balance at December 31, 2014 – $ – RSUs granted 187,200 30.74 RSUs canceled (19,450 ) 29.72 Balance at December 31, 2015 167,750 $ 30.86 None of these RSUs vested in 2015. We recognized stock-based compensation expenses of $1.5 million in 2015 relating to these RSUs. As of December 31, 2015, there was $3.3 million of unrecognized compensation costs related to these RSUs, which is expected to be recognized over an estimated weighted-average period of 2.0 years. Performance stock units In January and June 2015, the Compensation Committee of our Board of Directors approved 165,000 M-PSU awards to our executive officers. Each M-PSU represents a contingent right to receive one share of our Common Stock upon achievement of market-based performance and subject to the recipient’s continued employment. At any time during the four years following the date of the grant, a portion of the M-PSUs will vest one year after the date the average closing price of our Common Stock on the NASDAQ Global Select Market is above $50.00 per share for 45 consecutive trading days, and the remaining portion of the grant will vest one year after the date the average closing price of our Common Stock is above $60.00 per share for 45 consecutive trading days. The estimated M-PSU expense is being recognized, on an accelerated basis over the estimated requisite service period, with no adjustments in the future periods based upon our actual Common Stock price. In June 2015, the Compensation Committee of our Board of Directors approved a program to award up to 69,625 PSUs to certain non-executive employees based on the achievement of goals related to the development of Andexanet alfa and Betrixaban. Each award represents a contingent right to receive one share of our Common Stock upon the achievement of certain performance conditions by pre-specified dates and the award recipient’s continued employment. During the third and fourth quarter of 2015, performance conditions were achieved and 40,496 PSUs were granted. The estimated expense associated with these awards is also being recognized, on an accelerated basis, over the vesting period. The following table summarizes PSU activity, under our 2013 Plan and related information: Shares Subject to Weighted- Outstanding Average grant PSU's fair value per share Balance at December 31, 2014 – $ – PSUs granted 40,496 49.99 M-PSUs granted 165,000 24.29 PSUs canceled (235 ) 49.44 Balance at December 31, 2015 205,261 $ 29.33 None of these PSUs vested in 2015. We recognized stock-based compensation expenses of $2.3 million in 2015 relating to these PSUs . As of December 31, 2015, there was $3.3 million of compensation costs related to these PSUs, which is expected to be recognized over an estimated weighted-average period of 1.4 years. Employee Stock Purchase Plan (“ESPP”) The Board of Directors adopted the 2013 ESPP, effective upon the completion of Portola’s initial public offering of its common stock. As of December 31, 2015, we reserved a total of 1,818,314 shares of common stock for issuance under the 2013 ESPP. The reserve for shares available under the ESPP automatically increases on January 1st each year, beginning in 2014, by an amount equal to 2 % of the total number of outstanding shares of our common stock on December 31 st Stock-Based Compensation Stock-based compensation expense, net of estimated forfeitures, is reflected in the consolidated statements of operations as follows (in thousands): Year Ended December 31, 2015 2014 2013 Research and development $ 11,653 $ 4,551 $ 2,295 Selling, general and administrative 11,205 4,782 2,679 Total stock-based compensation $ 22,858 $ 9,333 $ 4,974 Valuation Assumptions The Fair value of our stock options and purchase rights under our ESPP were 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 these awards: Year Ended December 31, 2015 2014 2013 Risk-free interest rate Stock options 1.54%-1.93% 1.81%-1.89% 1.43% ESPP 0.14% 0.08% – Expected term Stock options 6.0 years 6.0 years 6.0 years ESPP 0.5 years 0.5 years – Expected volatility Stock options 64% - 66% 69% - 80% 79% ESPP 62% 73% – Dividend yield Stock options – – – ESPP – – – The weighted-average fair value of the M-PSUs was determined using the Monte Carlo simulation models incorporating the following assumptions: Year December 31, 2015 PSUs Number of M-PSUs granted 165,000 Weighted-average grant date stock price $ 31.95 Weighted-average risk-free interest rate 1.13 % Weighted-average volatility 62 % Dividend yield – Weighted- average fair value per share of M-PSUs granted ($50 Vesting Hurdle) $ 24.22 Weighted- average fair value per share of M-PSUs granted ($60 Vesting Hurdle) $ 24.34 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, 66,041, 33,888 and 32,943 shares with average exercise prices of $40.85, $25.41 and $19.88 per share, respectively, during the years ended December 31, 2015, 2014 and 2013, respectively. These options vest upon grant or various terms up to four years. We recognized non-employees stock compensation expense of $2.79 million $769,000 and $775,000 during the years ended December 31, 2015, 2014 and 2013, 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.

Net Loss per Share Attributable

Net Loss per Share Attributable to Portola Common Stockholders	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Net (Loss) Income per Share Attributable to Common Stockholders	11. Net Loss per Share Attributable to Portola Common Stockholders The following outstanding shares of common stock equivalents were excluded from the computation of diluted net loss per share attributable to Portola common stockholders for the periods presented because including them would have been antidilutive: Year Ended December 31, 2015 2014 2013 Stock options to purchase Common Stock 4,731,483 4,249,168 3,708,773 Common stock warrants 1,500 6,240 82,575 Restricted stock units 167,750 – – Performance stock units 205,261 – –

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2015
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plan	12. 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 3% of employee salary, $2,000, and $500 per employee for the years ended December 31, 2015, 2014 and 2013, respectively. During the years ended December 31, 2015, 2014 and 2013, we recognized total expense of $525,000, $153, 000 and $59, 000, respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	13. Income Taxes The U.S. income tax provision (benefit) consists of the following (in thousands): Year Ended December 31, 2015 2014 Current: Federal $ – $ – State (365 ) – (365 ) – Deferred: Federal $ – $ – State – – – – Total provision (benefit) for income taxes $ (365 ) $ – We recorded an income tax benefit of $365,000 for the year ended December 31, 2015. We did not record a tax provision for the years ended December 31, 2014 and 2013. The effective tax rate of our provision for income taxes differs from the federal statutory rate as follows: Year Ended December 31, 2015 2014 2013 Federal statutory income tax rate 34.0 % 34.0 % 34.0 % State income taxes, net of federal benefit (6.6) 11.2 0.4 Federal and state research credits 2.5 2.7 3.4 Stock based compensation 0.0 (1.6 ) (0.2 ) FIN 48 release 0.2 0.0 0.0 Other 0.0 (0.1 ) (0.5 ) Change in valuation allowance (29.9 ) (46.2 ) (37.1 ) Total tax benefit 0.2 % 0.0 % 0.0 % The income tax benefit for the year ended December 31, 2015 is due to the release of uncertain tax positions reserve relating to state tax exposures, the statute of which expired during the current period. The components of U.S. deferred tax assets and (liabilities) are as follows (in thousands): December 31, 2015 2014 Deferred tax assets: Federal and state net operating loss carryforwards $ 207,898 $ 146,725 Federal and state research tax credit carryforwards 18,744 15,337 Deferred revenue 9,192 12,523 Stock options 10,197 3,776 Capitalized acquisition costs 974 1,322 Other 3,942 3,589 Net deferred tax assets before valuation allowance 250,947 183,272 Valuation allowance (250,947 ) (183,272 ) 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 approximately $67.0 million for the year ended December 31, 2015. The valuation allowance increased by approximately $64.0 million for the year ended December 31, 2014. As of December 31, 2015, we had net operating loss carryforwards for federal income tax purposes of approximately $612.0 million and federal research tax credits of approximately $18.0 million, which expire at various dates in the period from 2024 to 2035. We also have California net operating loss carryforwards of approximately $223.0 million which expire at various dates in the period from 2017 to 2035 and California research tax credits of approximately $5.0 million. Our federal and state net operating loss carryforwards as of December 31, 2015 include amounts resulting from exercises and sales of stock option awards to employees and non-employees. When we realize the tax benefit associated with these stock option exercises as a reduction to taxable income in our returns, we will account for the tax benefit as a credit to stockholders’ equity rather than as a reduction of our income tax provision in our consolidated financial statements. Based upon our stock option exercise history, such amounts were not material as of December 31, 2015. For the year ended December 31, 2015, the Company has written-off approximately $194.0 million of the 2013 and 2014 California net operating losses relating to the outcome of the California Supreme Court case of Gillette Company et al. v. Franchise Tax Board. We performed an analysis on annual limitation as a result of ownership changes that may have occurred through December 2015. Our analysis indicates that a change occurred during 2013. As a result of this change, our net operating loss and tax credit carryforwards will not be subject to limitation in total, but we may be subject to a limitation as it relates to the timing of utilization. However, due to a lack of historical earnings and uncertainties surrounding our ability to generate future taxable income to realize these tax assets, a full valuation allowance has been established to offset our deferred tax assets. The annual limitation may result in the expiration of net operating losses and credits before utilization. Uncertain Tax Positions We are subject to taxation in the United States. We have not been audited by the Internal Revenue Service or any state tax authority. We are no longer subject to audit by the Internal Revenue Service for income tax returns filed before 2013, and by the material state and local tax authorities for tax returns filed before 2012. However, carryforward tax attributes that were generated prior to these years may still be adjusted upon examination by tax authorities. A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): Year Ended December 31, 2015 2014 2013 Unrecognized tax benefits, beginning of period $ 2,906 $ 2,048 $ 1,435 Increases due to current period positions 1,091 858 619 Decreases due to current period positions – – – Decreases due to prior period positions (404 ) – (6 ) Decreases due to the lapse of statutes of limitations (365 ) – – Unrecognized tax benefits, end of period $ 3,228 $ 2,906 $ 2,048 The amount of unrecognized income tax benefits that, if recognized, would affect our effective tax rate was zero and $365,000 as of December 31, 2015 and December 31, 2014, respectively. If the $3.2 million and $2.9 million of unrecognized income tax benefits as of December 31, 2015 and 2014, respectively, is recognized, there would be no impact to the effective tax rate as any change will fully offset the valuation allowance.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2015
Related Party Transactions [Abstract]
Related Party Transactions	14. 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, 2015, 2014 and 2013, we recorded a reduction in research and development expense of $352,000, $594,000 and $816,000, respectively, related to amounts owed to us by Global Blood and MyoKardia under the Master Services Agreements. As of December 31, 2015 and 2014, receivables from these related parties in the amount of $19,000 and $40,000, respectively, are included in prepaid expenses and other current assets on the consolidated balance sheet.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2015
Subsequent Events [Abstract]
Subsequent Events	15. Subsequent Events In January 2016, we entered into an agreement with BMS and Pfizer to out license development and commercial rights to develop Andexanet alfa as an antidote for apixaban and other fXa inhibitors in Japan. Under the terms of the agreement we will receive an upfront payment of $15.0 million and are eligible to receive potential regulatory and sales-based milestone payments totaling up to $90.0 million, as well as double-digit royalties based on Andexanet alfa net sales in Japan. BMS and Pfizer will be responsible for all development and regulatory activities for Andexanet alfa in Japan and for commercializing the drug in Japan. Separately, in January 2016 we also entered into a clinical collaboration agreement with Bayer to include its fXa inhibitor, rivaroxaban, in this clinical development program in Japan. Under the terms of the Bayer agreement, we will receive an upfront payment of $5.0 million and are eligible to receive an additional milestone payment based on Japanese regulatory approval of Andexanet alfa as an antidote for rivaroxaban. Bayer will provide technical support as well as fund clinical studies of Andexanet alfa with rivaroxaban in Japan. Bayer received no commercial rights under this agreement.

Quarterly Financial Data (unaud

Quarterly Financial Data (unaudited)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data (unaudited)	16. Quarterly Financial Data (unaudited) 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. 2015 2014 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Collaboration and license revenue $ 2,359 $ 2,385 $ 2,912 $ 4,414 $ 2,372 $ 2,415 $ 2,427 $ 2,411 Operating expenses $ (48,863 ) $ (61,212 ) $ (58,476 ) $ (70,694 ) $ (33,396 ) $ (33,920 ) $ (38,204 ) $ (41,671 ) Net loss $ (46,913 ) $ (58,329 ) $ (55,158 ) $ (66,105 ) $ (30,726 ) $ (31,350 ) $ (35,793 ) $ (39,256 ) Net loss per share attributable to Portola common stockholders: Basic and diluted $ (0.95 ) $ (1.12 ) $ (1.05 ) $ (1.23 ) $ (0.75 ) $ (0.76 ) $ (0.86 ) $ (0.82 )

Summary of Significant Accoun24

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
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 subsidiaries and a Development Partner that is a variable interest entity (a “VIE”) for which Portola is deemed, under applicable accounting guidance to be the primary beneficiary as of December 31, 2015. For the consolidated VIE, we record net loss attributable to noncontrolling interests in our Consolidated Statements of Operations equal to the percentage of the economic or ownership interest retained in such VIE by the respective noncontrolling parties.
Reclassification	Reclassification Prepaid expenses and other current assets in the prior year Consolidated Balance Sheet of $5.7 million have been reclassified to $1.7 million and $4.0 million in Prepaid research and development and Prepaid expenses and other current assets, respectively, and Accrued and other liabilities in the prior year Consolidated Balance Sheet of $14.0 million has been reclassified to $12.6 million and $1.4 million in Accrued research and development and Accrued and other liabilities, respectively, to conform to current-period presentation. Corresponding changes in Changes in operating assets and liabilities within the Consolidated Statement of Cash Flows have been adjusted to conform to these reclassifications.
Use of Estimates	Use of Estimates The preparation of consolidated 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 liabilities and the reported amounts of revenues and expenses in the consolidated 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, in-process research and development , the consolidation of VIEs and deconsolidation of VIEs
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 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.
In-process Research and Development Asset	In-process Research and Development Asset In-process research and development asset relates to our consolidated VIE and are considered to be indefinite-lived until the completion or abandonment of the associated R&D efforts which generally occurs if and when regulatory approval to market a product is obtained,
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 in Marketable Securities	Investments in Marketable Securities All investments in marketable securities 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.
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 biologics drug application (BLA) or 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. Collaboration Customer Concentration Collaboration customers who accounted for 10% or more of total collaboration and license revenues were as follows: Year Ended December 31, 2015 2014 2013 Bayer Pharma, AG and Janssen Pharmaceuticals, Inc. 48% 37% 37% Daiichi Sankyo, Inc. 38% 45% 23% Bristol-Myers Squibb Company and Pfizer Inc. 13% 16% 38%
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 for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Specific potential indicators of impairment include a significant decrease in the fair value of an asset, a significant change in the extent or manner in which an asset is used or a significant physical change in an asset, a significant adverse change in legal factors or in the business climate that affects the value of an asset, an adverse action or assessment by the FDA or another regulator or a projection or forecast that demonstrates continuing losses associated with an income producing asset.
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 expenses and related accruals 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 Employee stock-based compensation cost is measured at the grant date, based on the fair value of the award. The compensation cost is recognized as expense on a straight-line basis over the vesting period for options and restricted stock units (“RSUs”) and on an accelerated basis for market-based performance stock units (“M-PSUs”) and performance-based performance stock units (“PSUs”). For stock option grants, we use the Black-Scholes option pricing model to determine the fair value of stock options. This model requires us to make assumptions such as expected term, dividends, volatility and forfeiture rates that determine the stock options fair value. These key assumptions are based on peer companies compared to historical information and judgment regarding market factors and trends. If actual results are not consistent with our assumptions and judgments used in estimating these factors, we may be required to increase or decrease compensation expense, which could be material to its results of operations. For M-PSU awards, we use the Monte-Carlo option pricing model to determine the fair value of awards at the date of issue. The Monte-Carlo option-pricing model uses similar input assumptions as the Black-Scholes model; however, it further incorporates into the fair-value determination the possibility that the performance-based market condition may not be satisfied. Compensation costs related to awards with a market-based condition are recognized regardless of whether the market condition is ultimately satisfied. Compensation cost is not reversed if the achievement of the market condition does not occur. For RSUs and PSU awards, we base the fair value of awards on the closing market value of our common stock at the date of grant. 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 basis 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 financial transactions denominated in foreign currencies, primarily the Euro and British Pound, and, as a result, are exposed to changes in foreign currency exchange rates. We manage a portion of these cash flow exposures through purchasing and holding of Euros and British Pounds 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 currency deposits we hold are remeasured using period end spot rates. Foreign currency forward contracts are marked to market at the end of each period and recorded as gains and losses in the condensed consolidated statements of operations. We held no foreign currency forward contracts at December 31, 2015 or December 31, 2014. We recorded an unrealized loss of $114,000 in interest and other income (expense), net in our consolidated statements of operations related to foreign currency forward contracts for the year ended December 31, 2014. 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.
Net Loss per Share Attributable to Portola Common Stockholders	Net Loss per Share Attributable to Portola Common Stockholders Basic net loss per share attributable to Portola Common Stockholders is calculated by dividing the net loss attributable to Portola Common Stockholders by the weighted-average number of shares of Common Stock outstanding for the period. Diluted net loss per share attributable to Portola Common Stockholders is computed by giving effect to all potential dilutive Common Stock equivalents outstanding for the period. Diluted net loss per share attributable to Portola Common Stockholders is the same as basic net loss per share attributable to Portola Common Stockholders, since the effects of potentially dilutive securities are antidilutive.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (the “FASB”), jointly with the International Accounting Standards Board, issued ASU 2014-09, Revenue from Contracts with Customers In February 2015, the Financial Accounting Standards Board (the “FASB”) issued ASU 2015-02, Consolidation: amendment to the consolidation analysis In November 2015, the Financial Accounting Standards Board (“FASB”) issued ASU 2015-17, Income Taxes (Topic740): Balance Sheet Classification of Deferred Taxes

Summary of Significant Accoun25

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Percentage of Revenue from Significant Collaboration Customers	Collaboration customers who accounted for 10% or more of total collaboration and license revenues were as follows: Year Ended December 31, 2015 2014 2013 Bayer Pharma, AG and Janssen Pharmaceuticals, Inc. 48% 37% 37% Daiichi Sankyo, Inc. 38% 45% 23% Bristol-Myers Squibb Company and Pfizer Inc. 13% 16% 38%

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2015
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 (excluding consolidated VIE’s cash), allocated into Level 1, Level 2 and Level 3, that was measured on a recurring basis (in thousands): December 31, 2015 Level 1 Level 2 Level 3 Total Financial Assets: Money market funds $ 22,074 $ – $ – $ 22,074 Corporate notes and commercial paper – 242,033 – 242,033 U.S. government agency securities – 180,876 – 180,876 Total financial assets $ 22,074 $ 422,909 $ – $ 444,983 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

Financial Instruments (Tables)

Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2015
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, 2015 December 31, 2014 Estimated Estimated Unrealized Unrealized Fair Unrealized Unrealized Fair Cost Gains (Losses) Value Cost Gains (Losses) Value Money market funds $ 22,074 $ – $ – $ 22,074 $ 24,915 $ – $ – $ 24,915 Corporate notes and commercial paper 242,089 3 (59 ) 242,033 226,209 8 (170 ) 226,047 U.S. government agency securities 180,970 1 (95 ) 180,876 120,246 4 (81 ) 120,169 $ 445,133 $ 4 $ (154 ) $ 444,983 $ 371,370 $ 12 $ (251 ) $ 371,131 Classified as: Cash equivalents $ 171,310 $ 36,341 Short-term investments 257,713 251,759 Long-term investments 15,960 83,030 Total cash equivalents and investments $ 444,983 $ 371,131

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2015
Balance Sheet Related Disclosures [Abstract]
Property and Equipment	Property and equipment consists of the following (in thousands): December 31, 2015 2014 Computer equipment $ 960 $ 734 Capitalized software $ 865 674 Equipment $ 5,874 4,852 Leasehold improvements $ 7,529 4,217 15,228 10,477 Less accumulated depreciation and amortization (8,985 ) (7,701 ) Property and equipment, net $ 6,243 $ 2,776
Accrued Expenses	Accrued and other liabilities consist of the following (in thousands): December 31, 2015 2014 Commercial related $ 783 $ – Legal and accounting fees 506 354 Deferred rent 721 127 Other 816 940 Total accrued liabilities $ 2,826 $ 1,421

Collaboration and License Agr29

Collaboration and License Agreements (Tables)	12 Months Ended
	Dec. 31, 2015
Organization Consolidation And Presentation Of Financial Statements [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, 2015 2014 2013 Bayer and Janssen $ 5,740 $ 3,598 $ 3,876 Daiichi Sankyo 4,578 4,287 2,419 BMS and Pfizer 1,540 1,497 4,042 Lee's Pharmaceutical 212 243 194 Total collaboration and license revenue $ 12,070 $ 9,625 $ 10,531

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Future Minimum Commitments Under our Non-Cancelable Operating Leases	At December 31, 2015, our future minimum commitments under our non-cancelable operating leases were as follows (in thousands): Year ending December 31: 2016 $ 2,525 2017 2,603 2018 2,683 2019 2,764 2020 696 Total $ 11,271

Stock Based Compensation (Table

Stock Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Activity	The following table summarizes stock option activity, under our 2013 Plan and related information: Shares Subject to Weighted- Outstanding Average Exercise Stock Options Price Per Share Balance at December 31, 2014 4,249,168 $ 14.77 Options granted 1,815,991 38.33 Options exercised (1,095,486 ) 10.14 Options canceled (238,190 ) 26.26 Balance at December 31, 2015 4,731,483 $ 24.19
Additional Information Related to the Status of Stock Options	Additional information related to the status of stock options at December 31, 2015, is as follows (aggregate intrinsic value in thousands): Weighted- Average Remaining Exercise Price Contractual Aggregate Shares Per Share Life Intrinsic Value Outstanding 4,731,483 $ 24.19 7.3 $ 128,996 Vested and expected to vest 4,543,051 $ 23.73 7.2 $ 125,964 Vested 2,341,265 $ 14.92 5.6 $ 85,533
Stock Options Outstanding and Vested and Exercisable	Additional information regarding our stock options outstanding and vested and exercisable as of December 31, 2015 is summarized below: Stock Options Outstanding Stock Options Vested Weighted Average Weighted Number Weighted Number of Remaining Average of Average Stock Options Contractual Exercise Price Stock Options Exercise Price Exercise Prices Outstanding Life (Years) per Share Vested Per Share $3.30 - $5.10 495,133 2.4 $ 4.55 495,133 $ 4.55 $5.30 - $9.00 767,038 4.9 8.18 743,033 8.21 $9.50 - $22.16 483,519 7.3 15.29 321,529 14.88 $22.60-$25.00 330,676 7.9 23.95 162,964 23.95 $25.08-$25.08 523,124 8.0 25.08 251,396 25.08 $25.14-$29.19 522,962 8.7 27.57 170,511 27.83 $29.72-$29.72 542,160 8.8 29.72 127,311 29.72 $35.69-$44.39 578,896 9.0 40.82 53,971 42.84 $44.63 - $51.45 479,225 9.5 47.71 14,506 47.21 $52.74 - $52.74 8,750 9.6 52.74 911 52.74 4,731,483 7.3 $ 24.19 2,341,265 $ 14.92
Summary of RSU Activity	The following table summarizes RSU activity, under our 2013 Plan and related information: Shares Subject to Weighted- Outstanding Average grant RSU's fair value per share Balance at December 31, 2014 – $ – RSUs granted 187,200 30.74 RSUs canceled (19,450 ) 29.72 Balance at December 31, 2015 167,750 $ 30.86
Summary of PSU Activity	The following table summarizes PSU activity, under our 2013 Plan and related information: Shares Subject to Weighted- Outstanding Average grant PSU's fair value per share Balance at December 31, 2014 – $ – PSUs granted 40,496 49.99 M-PSUs granted 165,000 24.29 PSUs canceled (235 ) 49.44 Balance at December 31, 2015 205,261 $ 29.33
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, 2015 2014 2013 Research and development $ 11,653 $ 4,551 $ 2,295 Selling, general and administrative 11,205 4,782 2,679 Total stock-based compensation $ 22,858 $ 9,333 $ 4,974
Summary of Weighted-Average Assumptions of Fair Value Awards	The following table illustrates the weighted-average assumptions for the Black-Scholes option-pricing model used in determining the fair value of these awards: Year Ended December 31, 2015 2014 2013 Risk-free interest rate Stock options 1.54%-1.93% 1.81%-1.89% 1.43% ESPP 0.14% 0.08% – Expected term Stock options 6.0 years 6.0 years 6.0 years ESPP 0.5 years 0.5 years – Expected volatility Stock options 64% - 66% 69% - 80% 79% ESPP 62% 73% – Dividend yield Stock options – – – ESPP – – –
Assumptions used to Determine Weighted-Average Fair Value of M-Performance Stock Units	The weighted-average fair value of the M-PSUs was determined using the Monte Carlo simulation models incorporating the following assumptions: Year December 31, 2015 PSUs Number of M-PSUs granted 165,000 Weighted-average grant date stock price $ 31.95 Weighted-average risk-free interest rate 1.13 % Weighted-average volatility 62 % Dividend yield – Weighted- average fair value per share of M-PSUs granted ($50 Vesting Hurdle) $ 24.22 Weighted- average fair value per share of M-PSUs granted ($60 Vesting Hurdle) $ 24.34

Net Loss per Share Attributab32

Net Loss per Share Attributable to Portola Common Stockholders (Tables)	12 Months Ended
	Dec. 31, 2015
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 per share attributable to Portola common stockholders for the periods presented because including them would have been antidilutive: Year Ended December 31, 2015 2014 2013 Stock options to purchase Common Stock 4,731,483 4,249,168 3,708,773 Common stock warrants 1,500 6,240 82,575 Restricted stock units 167,750 – – Performance stock units 205,261 – –

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
U.S. Income Tax Provision (Benefit)	The U.S. income tax provision (benefit) consists of the following (in thousands): Year Ended December 31, 2015 2014 Current: Federal $ – $ – State (365 ) – (365 ) – Deferred: Federal $ – $ – State – – – – Total provision (benefit) for income taxes $ (365 ) $ –
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 and 2013. The effective tax rate of our provision for income taxes differs from the federal statutory rate as follows: Year Ended December 31, 2015 2014 2013 Federal statutory income tax rate 34.0 % 34.0 % 34.0 % State income taxes, net of federal benefit (6.6) 11.2 0.4 Federal and state research credits 2.5 2.7 3.4 Stock based compensation 0.0 (1.6 ) (0.2 ) FIN 48 release 0.2 0.0 0.0 Other 0.0 (0.1 ) (0.5 ) Change in valuation allowance (29.9 ) (46.2 ) (37.1 ) Total tax benefit 0.2 % 0.0 % 0.0 %
Components of U.S. Deferred Tax Assets and (Liabilities)	The components of U.S. deferred tax assets and (liabilities) are as follows (in thousands): December 31, 2015 2014 Deferred tax assets: Federal and state net operating loss carryforwards $ 207,898 $ 146,725 Federal and state research tax credit carryforwards 18,744 15,337 Deferred revenue 9,192 12,523 Stock options 10,197 3,776 Capitalized acquisition costs 974 1,322 Other 3,942 3,589 Net deferred tax assets before valuation allowance 250,947 183,272 Valuation allowance (250,947 ) (183,272 ) 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, 2015 2014 2013 Unrecognized tax benefits, beginning of period $ 2,906 $ 2,048 $ 1,435 Increases due to current period positions 1,091 858 619 Decreases due to current period positions – – – Decreases due to prior period positions (404 ) – (6 ) Decreases due to the lapse of statutes of limitations (365 ) – – Unrecognized tax benefits, end of period $ 3,228 $ 2,906 $ 2,048

Quarterly Financial Data (una34

Quarterly Financial Data (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data (unaudited)	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. 2015 2014 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Collaboration and license revenue $ 2,359 $ 2,385 $ 2,912 $ 4,414 $ 2,372 $ 2,415 $ 2,427 $ 2,411 Operating expenses $ (48,863 ) $ (61,212 ) $ (58,476 ) $ (70,694 ) $ (33,396 ) $ (33,920 ) $ (38,204 ) $ (41,671 ) Net loss $ (46,913 ) $ (58,329 ) $ (55,158 ) $ (66,105 ) $ (30,726 ) $ (31,350 ) $ (35,793 ) $ (39,256 ) Net loss per share attributable to Portola common stockholders: Basic and diluted $ (0.95 ) $ (1.12 ) $ (1.05 ) $ (1.23 ) $ (0.75 ) $ (0.76 ) $ (0.86 ) $ (0.82 )

Organization - Additional Infor

Organization - Additional Information (Detail)	1 Months Ended						12 Months Ended
	Dec. 31, 2015USD ($)$ / sharesshares	Mar. 31, 2015USD ($)$ / sharesshares	Oct. 31, 2014USD ($)$ / sharesshares	Nov. 30, 2013USD ($)shares	Oct. 31, 2013$ / sharesshares	May. 31, 2013USD ($)$ / sharesshares	Dec. 31, 2015USD ($)Segment$ / shares	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Organization And Nature Of Business [Line Items]
Number of operating segment | Segment							1
Stock issued during the period | shares						9,686,171
Public offering price of the shares sold | $ / shares						$ 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	$ 272,216,000	$ 175,185,000	$ 251,865,000
Number of preferred stock converted into common stock | shares						24,026,797
Follow on offering price per share | $ / shares	$ 48	$ 40	$ 26		$ 23.75		$ 48
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
Proceeds from offering and over-allotment option, net	$ 162,700,000	$ 108,400,000
Underwriters Overallotment Option
Organization And Nature Of Business [Line Items]
Stock issued during the period | shares	468,750	374,348	930,000	954,976		1,263,413
Follow-on Offering
Organization And Nature Of Business [Line Items]
Stock issued during the period | shares	3,593,750	2,870,000	6,200,000		6,366,513
Offering expenses				$ 862,000
Stock Issued during period shares existing shareholder | shares					1,908,803
Underwriting discounts and commissions, net			$ 10,200,000	$ 7,700,000
Underwriting discounts, commissions and offering expenses, net	$ 765,000	$ 358,000

Summary of Significant Accoun36

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015		Dec. 31, 2014	Dec. 31, 2013
Summary Of Significant Accounting Policies [Line Items]
Prepaid expenses and other current assets	$ 3,059,000	[1]	$ 4,061,000
Prepaid research and development	16,976,000	[1]	1,686,000
Accrued and other liabilities	2,826,000	[1]	1,421,000
Accrued research and development	24,195,000	[1]	12,545,000
Impairment losses	0
Interest or penalties charged to the underpayment of income taxes	0
Foreign currency forward Contract	$ 0		0
Unrealized loss			(114,000)	$ 261,000
Realized loss			(258,000)
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
Prior-Period Reclassified Amount
Summary Of Significant Accounting Policies [Line Items]
Prepaid expenses and other current assets			5,700,000
Accrued and other liabilities			$ 14,000,000
[1]	Amounts include the assets and liabilities of a consolidated variable interest entity (“VIE”). Portola's interests and obligations with respect to the VIE's assets and liabilities are limited to those accorded to Portola in its agreement with the VIE. See Note 8, “Asset Acquisition and License Agreements,” to these consolidated financial statements.

Revenue Accounted for 10% or Mo

Revenue Accounted for 10% or More of Total Collaboration and License Revenues (Detail) - Customer Concentration Risk - Sales Revenue, Net	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")
Concentration Risk [Line Items]
Concentration risk percentage	48.00%	37.00%	37.00%
Daiichi Sankyo, Inc ("Daiichi")
Concentration Risk [Line Items]
Concentration risk percentage	38.00%	45.00%	23.00%
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")
Concentration Risk [Line Items]
Concentration risk percentage	13.00%	16.00%	38.00%

Fair Values Measurements - Addi

Fair Values Measurements - Additional Information (Detail) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
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

Fair Value of Financial Assets,

Fair Value of Financial Assets, and Liabilities, Allocated into Level 1, Level 2, and Level 3 Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financial Assets:
Total financial assets	$ 444,983	$ 371,131
Fair Value, Inputs, Level 1
Financial Assets:
Total financial assets	22,074	24,915
Fair Value, Inputs, Level 2
Financial Assets:
Total financial assets	422,909	346,216
Money market funds
Financial Assets:
Total financial assets	22,074	24,915
Money market funds | Fair Value, Inputs, Level 1
Financial Assets:
Total financial assets	22,074	24,915
Corporate notes and commercial paper
Financial Assets:
Total financial assets	242,033	226,047
Corporate notes and commercial paper | Fair Value, Inputs, Level 2
Financial Assets:
Total financial assets	242,033	226,047
U.S. government agency securities
Financial Assets:
Total financial assets	180,876	120,169
U.S. government agency securities | Fair Value, Inputs, Level 2
Financial Assets:
Total financial assets	$ 180,876	$ 120,169

Cash Equivalents and Investment

Cash Equivalents and Investments Classified as Available-for-sale Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Available For Sale Securities [Line Items]
Cost	$ 445,133	$ 371,370
Unrealized Gains	4	12
Unrealized (Losses)	(154)	(251)
Estimated Fair Value	444,983	371,131
Money market funds
Schedule Of Available For Sale Securities [Line Items]
Cost	22,074	24,915
Estimated Fair Value	22,074	24,915
Corporate notes and commercial paper
Schedule Of Available For Sale Securities [Line Items]
Cost	242,089	226,209
Unrealized Gains	3	8
Unrealized (Losses)	(59)	(170)
Estimated Fair Value	242,033	226,047
U.S. government agency securities
Schedule Of Available For Sale Securities [Line Items]
Cost	180,970	120,246
Unrealized Gains	1	4
Unrealized (Losses)	(95)	(81)
Estimated Fair Value	180,876	120,169
Cash equivalents
Schedule Of Available For Sale Securities [Line Items]
Estimated Fair Value	171,310	36,341
Short-term investments
Schedule Of Available For Sale Securities [Line Items]
Estimated Fair Value	257,713	251,759
Long-term investments
Schedule Of Available For Sale Securities [Line Items]
Estimated Fair Value	$ 15,960	$ 83,030

Financial Instruments - Additio

Financial Instruments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	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	$ 0

Property and Equipment (Detail)

Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2015		Dec. 31, 2014
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 15,228		$ 10,477
Less accumulated depreciation and amortization	(8,985)		(7,701)
Property and equipment, net	6,243	[1]	2,776
Computer equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	960		734
Capitalized software
Property Plant And Equipment [Line Items]
Property and equipment, gross	865		674
Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	5,874		4,852
Leasehold improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 7,529		$ 4,217
[1]	Amounts include the assets and liabilities of a consolidated variable interest entity (“VIE”). Portola's interests and obligations with respect to the VIE's assets and liabilities are limited to those accorded to Portola in its agreement with the VIE. See Note 8, “Asset Acquisition and License Agreements,” to these consolidated financial statements.

Accrued Expenses (Detail)

Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2015		Dec. 31, 2014
Payables And Accruals [Abstract]
Commercial related	$ 783
Legal and accounting fees	506		$ 354
Deferred rent	721		127
Other	816		940
Total accrued liabilities	$ 2,826	[1]	$ 1,421
[1]	Amounts include the assets and liabilities of a consolidated variable interest entity (“VIE”). Portola's interests and obligations with respect to the VIE's assets and liabilities are limited to those accorded to Portola in its agreement with the VIE. See Note 8, “Asset Acquisition and License Agreements,” to these consolidated financial statements.

Summary of Revenue from Collabo

Summary of Revenue from Collaboration and License Agreements (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	$ 4,414	$ 2,912	$ 2,385	$ 2,359	$ 2,411	$ 2,427	$ 2,415	$ 2,372	$ 12,070	$ 9,625	$ 10,531
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue									5,740	3,598	3,876
Daiichi Sankyo, Inc ("Daiichi")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue									4,578	4,287	2,419
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue									1,540	1,497	4,042
Lee’s Pharmaceutical (HK) Ltd (“Lee’s”)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue									$ 212	$ 243	$ 194

Collaboration and License Agr45

Collaboration and License Agreements - Additional Information (Detail) - USD ($)	1 Months Ended						3 Months Ended								6 Months Ended	12 Months Ended			24 Months Ended
	Jul. 31, 2014	Apr. 30, 2014	Jan. 31, 2014	Feb. 28, 2013	Jan. 31, 2013	Nov. 30, 2012	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue							$ 4,414,000	$ 2,912,000	$ 2,385,000	$ 2,359,000	$ 2,411,000	$ 2,427,000	$ 2,415,000	$ 2,372,000		$ 12,070,000	$ 9,625,000	$ 10,531,000
Research and development																200,376,000	123,639,000	79,286,000
Bayer Pharma AG
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional non-refundable fee				$ 250,000
Upfront fee				2,500,000
Janssen Pharmaceuticals, Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional non-refundable fee				250,000
Upfront fee				2,500,000
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional non-refundable fee				500,000
Upfront fee			$ 10,000,000	$ 5,000,000
Collaboration and license revenue																5,740,000	3,598,000	3,876,000
Contingent payment receivable upon achievement			7,000,000
Milestone Payments of Development and Regulatory Event			8,000,000
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen") | February 2013 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue																500,000	1,100,000	3,900,000
Deferred revenue							0				0					0	0		$ 0
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen") | January 2014 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue																5,200,000	2,500,000
Deferred revenue							7,200,000				10,500,000					7,200,000	10,500,000		7,200,000
Contingent Payments Received																	3,000,000
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen") | January 2014 Agreement | Future Contingent Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue																2,000,000	0
Daiichi Sankyo, Inc ("Daiichi")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee	$ 15,000,000
Collaboration and license revenue																4,578,000	4,287,000	2,419,000
Deferred revenue							0				1,000,000					0	1,000,000		0
Contingent payment receivable upon achievement	5,000,000
Milestone Payments of Development and Regulatory Event	$ 20,000,000
Contingent and non-contingent consideration to be recognized after resolution of contingency																1,000,000	2,500,000	2,400,000
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
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
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue																3,500,000	1,800,000
Deferred revenue							9,700,000				13,200,000					9,700,000	13,200,000		9,700,000
Daiichi Sankyo, Inc ("Daiichi") | Collaborative Agreement to Study Safety and Efficacy of Andexanet Alfa | Future Contingent Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue																0
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee			13,000,000
Collaboration and license revenue																1,540,000	1,497,000	4,042,000
Contingent payment receivable upon achievement																7,500,000
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") | January 2014 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue																1,500,000	1,500,000
Deferred revenue							8,400,000				11,500,000					8,400,000	11,500,000		8,400,000
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | October 2012 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue																		4,000,000
Deferred revenue																		6,000,000
Lee’s Pharmaceutical (HK) Ltd (“Lee’s”)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee					$ 700,000
Collaboration and license revenue																212,000	243,000	194,000
Deferred revenue							$ 52,000				$ 263,000					$ 52,000	263,000		$ 52,000
Notice period for agreement termination					60 days
Ora, Inc. (“Ora”)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Notice period for agreement termination																90 days
Development costs, percent																60.00%
Percentage of profits entitle to receive under agreement																50.00%
Rights to buy compound interests and licensed agreements																Each party may also buy out the rights and interests in the licensed compound by paying the greater of $6.0 million or two times the actual aggregate development cost incurred by both parties before or 90 days after an End of Phase 2 meeting with the FDA.
Research and development																$ 206,000
Ora, Inc. (“Ora”) | PORTOLA PHARMACEUTICALS INC
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development costs, percent																40.00%
Biogen Idec
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License fee receivable upon occurrence of certain development and regulatory events						$ 370,000,000
Payments Upon the Completion of Certain Commercial Milestones		$ 15,000,000
Reduction in research and development expense																	210,000	804,000
Aciex Therapeutics, Inc. (“Aciex”)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development costs, percent																60.00%
Percentage of profits entitle to receive under agreement																50.00%
Research and development																$ 0	$ 0	$ 0
Aciex Therapeutics, Inc. (“Aciex”) | PORTOLA PHARMACEUTICALS INC
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development costs, percent																40.00%

Commercial Supply Agreement - A

Commercial Supply Agreement - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Jul. 31, 2014	Dec. 31, 2015		Dec. 31, 2014	Nov. 01, 2014
Long Term Purchase Commitment [Line Items]
Termination fees payment under obligation		$ 1,000,000
Prepaid and other long-term assets		11,993,000	[1]	$ 15,612,000
Prepaid research and development		16,976,000	[1]	$ 1,686,000
CMC ICOS Biologics Inc
Long Term Purchase Commitment [Line Items]
Commercial supply agreement upfront payment	$ 10,000,000
Commercial supply (manufacturing services) agreement reservation payment					$ 4,600,000
Commercial agreement fixed commitment amount	276,100,000
Payments made for purchases of batches related to commercial supply agreement		$ 29,000,000
Term of commercial supply agreement		7 years
Purchases of batches recorded in prepaid research and development		$ 13,000,000
CMC ICOS Biologics Inc | Upfront and Reservation Payment
Long Term Purchase Commitment [Line Items]
Prepaid expenses and other assets		14,600,000
Prepaid and other long-term assets		11,400,000
Prepaid research and development		$ 2,900,000
CMC ICOS Biologics Inc | Minimum
Long Term Purchase Commitment [Line Items]
Termination fees payment under obligation	5,000,000
CMC ICOS Biologics Inc | Maximum
Long Term Purchase Commitment [Line Items]
Termination fees payment under obligation	$ 30,000,000
[1]	Amounts include the assets and liabilities of a consolidated variable interest entity (“VIE”). Portola's interests and obligations with respect to the VIE's assets and liabilities are limited to those accorded to Portola in its agreement with the VIE. See Note 8, “Asset Acquisition and License Agreements,” to these consolidated financial statements.

Asset Acquisition and License47

Asset Acquisition and License Agreements - Additional Information (Detail) - USD ($)		1 Months Ended			12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Nov. 30, 2007	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2011	Dec. 01, 2015
Asset Acquisition [Line Items]
Restricted cash (Development Partner)	[1]	$ 341,000			$ 341,000
Research and development					$ 200,376,000	$ 123,639,000	$ 79,286,000
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
Development Partner
Asset Acquisition [Line Items]
Variable interest entity, Terms of arrangements					Accordingly, the Development Partner is subject to consolidation and we have consolidated the financial statements of the Development Partner since inception of the agreement on December 1, 2015 by (a) eliminating all intercompany balances and transactions; (b) allocating loss attributable to the noncontrolling interest in the Development Partner to net loss attributable to noncontrolling interest in our consolidated statement of operations and reflecting noncontrolling interest on our consolidated balance sheet.
Variable interest entity, Upfront payment		500,000
Intellectual property asset at fair value									$ 3,200,000
Noncontrolling interest in variable Interest entity		2,900,000			$ 2,900,000				$ 2,900,000
Research and development expense, In process		3,200,000
Restricted cash (Development Partner)		$ 341,000			341,000
Net loss attributable to noncontrolling interest (Development Partner)					$ 0
[1]	Amounts include the assets and liabilities of a consolidated variable interest entity (“VIE”). Portola's interests and obligations with respect to the VIE's assets and liabilities are limited to those accorded to Portola in its agreement with the VIE. See Note 8, “Asset Acquisition and License Agreements,” to these consolidated financial statements.

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Commitments And Contingencies Disclosure [Abstract]
Lease cancellation notice period	30 days
Commitment maturing in the next fiscal year	$ 33,200,000
Other commitment, due in second year	8,100,000
Other commitment, due in third year	$ 685,000
Lease term expiration date	Mar. 31, 2020
Tenant improvement allowance	$ 6,300,000
Early termination right effective date	Mar. 31, 2018
Early termination fees	$ 1,000,000
Rent expense	$ 1,700,000	$ 1,200,000	$ 803,000

Future Minimum Commitments Unde

Future Minimum Commitments Under our Non-Cancelable Operating Leases (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Commitments And Contingencies Disclosure [Abstract]
2,016	$ 2,525
2,017	2,603
2,018	2,683
2,019	2,764
2,020	696
Total	$ 11,271

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended			14 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2013	Jun. 30, 2015	Jan. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved, shares	1,422,745	1,422,745
Percentage increase in number of common stock outstanding		5.00%
Number of common stock shares reserved for issuance under the 2013 Employee Stock Purchase Plan	9,387,452	9,387,452
Term of stock options granted		10 years
Vesting period		4 years
Aggregate intrinsic value of stock options exercised		$ 35,900,000	$ 12,500,000		$ 6,300,000
Total estimated grant date fair value of stock options vested		12,000,000	$ 9,000,000	$ 3,800,000
Unamortized share based compensation expected to be recognized over the remaining vesting period	$ 42,400,000	$ 42,400,000
Unamortized share based compensation expected recognition period		2 years 9 months 18 days
Weighted-average per share fair value of employee stock options granted		$ 22.84	$ 15.73	$ 12.46
Stock-based compensation expense		$ 22,858,000	$ 9,333,000	$ 4,974,000
Share based compensation, options weighted average exercise price		$ 38.33
Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved, shares	1,759,270	1,759,270
Percentage increase in number of common stock outstanding		2.00%
Number of common stock shares reserved for issuance under the 2013 Employee Stock Purchase Plan	1,818,314	1,818,314
Exercise price of stock options granted as a minimum percentage of fair value of common stock		85.00%
Dividend yield		0.00%	0.00%	0.00%
Incentive Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise price of stock options granted as a minimum percentage of fair value of common stock		100.00%
Nonstatutory Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise price of stock options granted as a minimum percentage of fair value of common stock		85.00%
10% or more
Share Based Compensation Arrangement By Share Based Payment Award [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%
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		3 years
Unamortized share based compensation expected to be recognized over the remaining vesting period	$ 3,300,000	$ 3,300,000
Unamortized share based compensation expected recognition period		2 years
RSUs Vested during the year		0
Stock-based compensation expense		$ 1,500,000
Performance-based RSUs awarded based on achievement of development goals		187,200
Performance Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of common stock shares reserved for issuance under the 2013 Employee Stock Purchase Plan						165,000	165,000
Vesting period		4 years
Unamortized share based compensation expected to be recognized over the remaining vesting period	$ 3,300,000	$ 3,300,000
Unamortized share based compensation expected recognition period		1 year 4 months 24 days
RSUs Vested during the year		0
Stock-based compensation expense		$ 2,300,000
Number of common stock earned per share		1.00%
Vesting rights		At any time during the four years following the date of the grant, a portion of the M-PSUs will vest one year after the date the average closing price of our Common Stock on the NASDAQ Global Select Market is above $50.00 per share for 45 consecutive trading days, and the remaining portion of the grant will vest one year after the date the average closing price of our Common Stock is above $60.00 per share for 45 consecutive trading days
Consecutive trading period required to earn PSU		45 days
Performance-based RSUs awarded based on achievement of development goals	40,496	165,000
Dividend yield		0.00%
Performance Shares | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Performance-based RSUs awarded based on achievement of development goals, available for grant						69,625
Performance Shares | $50 Vesting Hurdle
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Minimum average market closing price to earn M-PSU		$ 50
Performance Shares | $60 Vesting Hurdle
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Minimum average market closing price to earn M-PSU		$ 60
Nonemployee Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		4 years
Share based compensation, options granted		66,041	33,888	32,943
Share based compensation, options weighted average exercise price		$ 40.85	$ 25.41	$ 19.88
Stock-based compensation		$ 2,790,000	$ 769,000	$ 775,000

Summary of Stock Option Activit

Summary of Stock Option Activity (Detail)	12 Months Ended
	Dec. 31, 2015$ / sharesshares
Shares Subject to Outstanding Stock Options
Beginning balance | shares	4,249,168
Options granted | shares	1,815,991
Options exercised | shares	(1,095,486)
Options canceled | shares	(238,190)
Ending balance | shares	4,731,483
Weighted-Average Exercise Price Per Share
Beginning balance | $ / shares	$ 14.77
Options granted | $ / shares	38.33
Options exercised | $ / shares	10.14
Options canceled | $ / shares	26.26
Ending balance | $ / shares	$ 24.19

Status of Stock Options (Detail

Status of Stock Options (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Shares
Outstanding	4,731,483	4,249,168
Vested and expected to vest	4,543,051
Vested	2,341,265	2,341,265
Weighted-Average Exercise Price Per Share
Outstanding	$ 24.19	$ 14.77
Vested and expected to vest	23.73
Vested	$ 14.92
Remaining Contractual Life
Outstanding	7 years 3 months 18 days
Vested and expected to vest	7 years 2 months 12 days
Vested	5 years 7 months 6 days
Aggregate Intrinsic Value
Outstanding	$ 128,996
Vested and expected to vest	125,964
Vested	$ 85,533

Stock Options Outstanding and V

Stock Options Outstanding and Vested and Exercisable (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Stock Options Outstanding, Number of Stock Options Outstanding	4,731,483	4,249,168
Outstanding	7 years 3 months 18 days
Outstanding	$ 24.19	$ 14.77
Stock Options Vested, Number of Stock Options Vested	2,341,265	2,341,265
Stock Options Vested, Weighted Average Exercise Price Per Share	$ 14.92
$3.30 - $5.10
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices, Lower Limit	3.30
Exercise Prices, Upper Limit	$ 5.10
Stock Options Outstanding, Number of Stock Options Outstanding	495,133
Outstanding	2 years 4 months 24 days
Outstanding	$ 4.55
Stock Options Vested, Number of Stock Options Vested	495,133
Stock Options Vested, Weighted Average Exercise Price Per Share	$ 4.55
$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
Stock Options Outstanding, Number of Stock Options Outstanding	767,038
Outstanding	4 years 10 months 24 days
Outstanding	$ 8.18
Stock Options Vested, Number of Stock Options Vested	743,033
Stock Options Vested, Weighted Average Exercise Price Per Share	$ 8.21
$9.50 - $22.16
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices, Lower Limit	9.50
Exercise Prices, Upper Limit	$ 22.16
Stock Options Outstanding, Number of Stock Options Outstanding	483,519
Outstanding	7 years 3 months 18 days
Outstanding	$ 15.29
Stock Options Vested, Number of Stock Options Vested	321,529
Stock Options Vested, Weighted Average Exercise Price Per Share	$ 14.88
$22.60-$25.00
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices, Lower Limit	22.60
Exercise Prices, Upper Limit	$ 25
Stock Options Outstanding, Number of Stock Options Outstanding	330,676
Outstanding	7 years 10 months 24 days
Outstanding	$ 23.95
Stock Options Vested, Number of Stock Options Vested	162,964
Stock Options Vested, Weighted Average Exercise Price Per Share	$ 23.95
$25.08-$25.08
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices, Lower Limit	25.08
Exercise Prices, Upper Limit	$ 25.08
Stock Options Outstanding, Number of Stock Options Outstanding	523,124
Outstanding	8 years
Outstanding	$ 25.08
Stock Options Vested, Number of Stock Options Vested	251,396
Stock Options Vested, Weighted Average Exercise Price Per Share	$ 25.08
$25.14-$29.19
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices, Lower Limit	25.14
Exercise Prices, Upper Limit	$ 29.19
Stock Options Outstanding, Number of Stock Options Outstanding	522,962
Outstanding	8 years 8 months 12 days
Outstanding	$ 27.57
Stock Options Vested, Number of Stock Options Vested	170,511
Stock Options Vested, Weighted Average Exercise Price Per Share	$ 27.83
$29.72-$29.72
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices, Lower Limit	29.72
Exercise Prices, Upper Limit	$ 29.72
Stock Options Outstanding, Number of Stock Options Outstanding	542,160
Outstanding	8 years 9 months 18 days
Outstanding	$ 29.72
Stock Options Vested, Number of Stock Options Vested	127,311
Stock Options Vested, Weighted Average Exercise Price Per Share	$ 29.72
$35.69-$44.39
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices, Lower Limit	35.69
Exercise Prices, Upper Limit	$ 44.39
Stock Options Outstanding, Number of Stock Options Outstanding	578,896
Outstanding	9 years
Outstanding	$ 40.82
Stock Options Vested, Number of Stock Options Vested	53,971
Stock Options Vested, Weighted Average Exercise Price Per Share	$ 42.84
$44.63 - $51.45
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices, Lower Limit	44.63
Exercise Prices, Upper Limit	$ 51.45
Stock Options Outstanding, Number of Stock Options Outstanding	479,225
Outstanding	9 years 6 months
Outstanding	$ 47.71
Stock Options Vested, Number of Stock Options Vested	14,506
Stock Options Vested, Weighted Average Exercise Price Per Share	$ 47.21
$52.74 - $52.74
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices, Lower Limit	52.74
Exercise Prices, Upper Limit	$ 52.74
Stock Options Outstanding, Number of Stock Options Outstanding	8,750
Outstanding	9 years 7 months 6 days
Outstanding	$ 52.74
Stock Options Vested, Number of Stock Options Vested	911
Stock Options Vested, Weighted Average Exercise Price Per Share	$ 52.74

Summary of RSU Activity (Detail

Summary of RSU Activity (Detail) - Restricted Stock Units (RSUs)	12 Months Ended
	Dec. 31, 2015$ / sharesshares
Shares Subject to Outstanding Options
RSUs granted | shares	187,200
RSUs canceled | shares	(19,450)
Ending balance | shares	167,750
Weighted-Average Exercise Price Per Share
RSUs granted | $ / shares	$ 30.74
RSUs canceled | $ / shares	29.72
Ending balance | $ / shares	$ 30.86

Summary of PSU Activity (Detail

Summary of PSU Activity (Detail) - Performance Shares - $ / shares	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015
Shares Subject to Outstanding Options
RSUs granted	40,496	165,000
Weighted-Average Exercise Price Per Share
Ending balance	$ 31.95	$ 31.95
2013 Equity Incentive Plan
Shares Subject to Outstanding Options
RSUs granted		40,496
M-PSUs granted		165,000
RSUs canceled		(235)
Ending balance	205,261	205,261
Weighted-Average Exercise Price Per Share
RSUs granted		$ 49.99
M-PSUs granted		24.29
RSUs canceled		49.44
Ending balance	$ 29.33	$ 29.33

Classification of Stock-Based C

Classification of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 22,858	$ 9,333	$ 4,974
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	11,653	4,551	2,295
Selling, General and Administrative Expenses
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 11,205	$ 4,782	$ 2,679

Summary of Weighted-Average Ass

Summary of Weighted-Average Assumptions of Fair Value Awards (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate			1.43%
Risk-free interest rate, minimum	1.54%	1.81%
Risk-free interest rate, maximum	1.93%	1.89%
Expected term	6 years	6 years	6 years
Expected volatility			79.00%
Expected volatility, minimum	64.00%	69.00%
Expected volatility, maximum	66.00%	80.00%
Dividend yield	0.00%	0.00%	0.00%
Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	0.14%	0.08%
Expected term	6 months	6 months
Expected volatility	62.00%	73.00%
Dividend yield	0.00%	0.00%	0.00%

Weighted-Average Fair Value of

Weighted-Average Fair Value of M-Performance Stock Units (Detail) - Performance Shares	3 Months Ended	12 Months Ended
	Dec. 31, 2015$ / sharesshares	Dec. 31, 2015$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of M-PSUs granted | shares	40,496	165,000
Weighted-average grant date stock price	$ 31.95	$ 31.95
Weighted-average risk-free interest rate		1.13%
Weighted-average volatility		62.00%
Dividend yield		0.00%
$50 Vesting Hurdle
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted- average fair value per share of M-PSUs granted		$ 24.22
$60 Vesting Hurdle
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted- average fair value per share of M-PSUs granted		$ 24.34

Weighted-Average Fair Value o59

Weighted-Average Fair Value of M-Performance Stock Units (Parenthetical) (Detail) - Performance Shares	12 Months Ended
	Dec. 31, 2015$ / shares
$50 Vesting Hurdle
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Minimum average market closing price to earn M-PSU	$ 50
$60 Vesting Hurdle
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Minimum average market closing price to earn M-PSU	$ 60

Outstanding Shares of Common St

Outstanding Shares of Common Stock Excluded from Computation of Diluted Net Loss per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
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	4,731,483	4,249,168	3,708,773
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	1,500	6,240	82,575
Restricted Stock Units (RSUs)
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of diluted net loss per share	167,750
Performance Shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of diluted net loss per share	205,261

Employee Benefit Plan - Additio

Employee Benefit Plan - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Compensation And Retirement Disclosure [Abstract]
Defined contribution plan maximum employee contribution of employee salary	3.00%
Defined contribution plan maximum annual employer matching contribution per employee	$ 2,000	$ 500
Employee benefit plans, contribution expense	$ 525,000	$ 153,000	$ 59,000

U.S. Income Tax Provision (Bene

U.S. Income Tax Provision (Benefit) (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current:
State	$ (365,000)
Total current federal, state provision (benefit) for income tax	(365,000)
Deferred:
Total provision (benefit) for income taxes	$ (365,000)	$ 0	$ 0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax [Line Items]
Total provision (benefit) for income taxes	$ (365,000)	$ 0	$ 0
Increase (Decrease) in valuation allowance	67,000,000	64,000,000
Unrecognized income tax benefits that, if recognized, would affect effective tax rate	0	365,000,000
Unrecognized income tax benefits	3,228,000	$ 2,906,000	$ 2,048,000	$ 1,435,000
California Franchise Tax Board
Income Tax [Line Items]
Written off related to net operating losses	$ 194,000,000
Minimum
Income Tax [Line Items]
Federal research tax credits, expiration year	2,024
Maximum
Income Tax [Line Items]
Federal research tax credits, expiration year	2,035
Federal
Income Tax [Line Items]
Net operating loss carryforwards	$ 612,000,000
Federal | Research Tax Credit Carryforward
Income Tax [Line Items]
Tax credits carryforwards	18,000,000
California
Income Tax [Line Items]
Net operating loss carryforwards	$ 223,000,000
California | Minimum
Income Tax [Line Items]
Net operating loss carryforwards, expiration year	2,017
California | Maximum
Income Tax [Line Items]
Net operating loss carryforwards, expiration year	2,035
California | Research Tax Credit Carryforward
Income Tax [Line Items]
Tax credits carryforwards	$ 5,000,000

Reconciliation of Effective Tax

Reconciliation of Effective Tax Rate for the Provision for Income Taxes (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
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	(6.60%)	11.20%	0.40%
Federal and state research credits	2.50%	2.70%	3.40%
Stock based compensation	0.00%	(1.60%)	(0.20%)
FIN 48 release	0.20%	0.00%	0.00%
Other	0.00%	(0.10%)	(0.50%)
Change in valuation allowance	(29.90%)	(46.20%)	(37.10%)
Total tax benefit	0.20%	0.00%	0.00%

Components of U.S. Deferred Tax

Components of U.S. Deferred Tax Assets and (liabilities) (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Federal and state net operating loss carryforwards	$ 207,898	$ 146,725
Federal and state research tax credit carryforwards	18,744	15,337
Deferred revenue	9,192	12,523
Stock options	10,197	3,776
Capitalized acquisition costs	974	1,322
Other	3,942	3,589
Net deferred tax assets before valuation allowance	250,947	183,272
Valuation allowance	$ (250,947)	$ (183,272)

Reconciliation of the Beginning

Reconciliation of the Beginning and Ending Amount of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation Of Unrecognized Tax Benefits Excluding Amounts Pertaining To Examined Tax Returns Roll Forward
Unrecognized tax benefits, beginning of period	$ 2,906	$ 2,048	$ 1,435
Increases due to current period positions	1,091	858	619
Decreases due to prior period positions	(404)		(6)
Decreases due to the lapse of statutes of limitations	(365)
Unrecognized tax benefits, end of period	$ 3,228	$ 2,906	$ 2,048

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Related Party Transaction [Line Items]
Receivables from related parties	$ 19	$ 40
Chief Executive Officer | Master Services Agreement
Related Party Transaction [Line Items]
Reduction in research and development expense	$ 352	$ 594	$ 816

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - Subsequent $ in Millions	Jan. 31, 2016USD ($)
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")
Subsequent Event [Line Items]
Upfront payment receivable	$ 15
Potential regulatory and sales-based milestone payments receivable	90
Bayer Pharma AG
Subsequent Event [Line Items]
Upfront payment receivable	$ 5

Quarterly Financial Information

Quarterly Financial Information (unaudited) (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Data [Abstract]
Collaboration and license revenue	$ 4,414	$ 2,912	$ 2,385	$ 2,359	$ 2,411	$ 2,427	$ 2,415	$ 2,372	$ 12,070	$ 9,625	$ 10,531
Operating expenses	(70,694)	(58,476)	(61,212)	(48,863)	(41,671)	(38,204)	(33,920)	(33,396)	(239,245)	(147,191)	(94,709)
Net loss	$ (66,105)	$ (55,158)	$ (58,329)	$ (46,913)	$ (39,256)	$ (35,793)	$ (31,350)	$ (30,726)	$ (226,505)	$ (137,125)	$ (83,352)
Net loss per share attributable to Portola common stockholders:
Basic and diluted	$ (1.23)	$ (1.05)	$ (1.12)	$ (0.95)	$ (0.82)	$ (0.86)	$ (0.76)	$ (0.75)	$ (4.36)	$ (3.19)	$ (3.65)