Portola Pharmaceuticals (PTLA) 10-K 1 Mar 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Feb. 21, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
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			$ 1,956.8
Entity Common Stock, Shares Outstanding		65,392,310

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 181,568	$ 188,480
Short-term investments	281,589	130,291
Restricted cash (SRX Cardio)	173	178
Receivables from collaborators	3,750
Inventory	1,099
Prepaid research and development	734	7,299
Prepaid expenses and other current assets	9,010	2,680
Total current assets	477,923	328,928
Property and equipment, net	5,217	6,143
Intangible assets	7,851	3,151
Long-term investments	71,076
Prepaid and other long-term assets	9,609	5,214
Total assets	571,676	343,436
Current liabilities:
Accounts payable	9,304	14,546
Accrued compensation and employee benefits	11,526	4,806
Accrued research and development	44,973	23,818
Accrued and other liabilities	3,552	1,696
Deferred revenue, current portion	11,169	20,798
Total current liabilities	80,524	65,664
Notes payable, long-term	50,565	49,815
Long term debt	54,251
Long term obligation to Collaborator	8,000	8,000
Deferred revenue, long-term	18,798	24,965
Other long-term liabilities	10,045	2,303
Total liabilities	222,183	150,747
Stockholders’ equity:
Preferred stock, $0.001 par value, 5,000,000 shares authorized; no shares issued and outstanding
Common stock, $0.001 par value, 100,000,000 shares authorized at December 31, 2017 and 2016; 65,296,643 shares and 56,544,218 shares issued and outstanding at December 31, 2017 and 2016, respectively	66	57
Additional paid-in capital	1,551,728	1,108,832
Accumulated deficit	(1,204,519)	(918,345)
Accumulated other comprehensive loss	(409)	(12)
Total Portola stockholders’ equity	346,866	190,532
Noncontrolling interest (SRX Cardio)	2,627	2,157
Total stockholders’ equity	349,493	192,689
Total liabilities and stockholders’ equity	$ 571,676	$ 343,436

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
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	65,296,643	56,544,218
Common stock, shares outstanding	65,296,643	56,544,218

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Collaboration and license revenue	$ 22,546,000	$ 35,504,000	$ 12,070,000
Operating expenses:
Cost of sales	415,000
Research and development	203,701,000	246,854,000	200,376,000
Selling, general and administrative	91,109,000	58,235,000	38,869,000
Total operating expenses	295,225,000	305,089,000	239,245,000
Loss from operations	(272,679,000)	(269,585,000)	(227,175,000)
Interest and other income (expense), net	(1,338,000)	1,533,000	305,000
Interest expense	(11,603,000)	(61,000)
Loss before taxes	(285,620,000)	(268,113,000)	(226,870,000)
Income tax benefit	0	0	365,000
Net loss	(285,620,000)	(268,113,000)	(226,505,000)
Net income attributable to noncontrolling interest (SRX Cardio)	(470,000)	(930,000)
Net loss attributable to Portola	$ (286,090,000)	$ (269,043,000)	$ (226,505,000)
Net loss per share attributable to Portola common stockholders:
Basic and diluted	$ (4.81)	$ (4.76)	$ (4.36)
Shares used to compute net loss per share attributable to Portola common stockholders:
Basic and diluted	59,508,156	56,480,647	51,981,463

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (285,620)	$ (268,113)	$ (226,505)
Other comprehensive income:
Unrealized gain (loss) on available-for-sale securities, net of tax	(397)	138	89
Comprehensive loss	(286,017)	(267,975)	(226,416)
Comprehensive income attributable to noncontrolling interest (SRX Cardio)	(470)	(930)
Total comprehensive loss attributable to Portola	$ (286,487)	$ (268,905)	$ (226,416)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	IPO	Common Stock	Common StockIPO	Additional Paid-In Capital	Additional Paid-In CapitalIPO	Accumulated Deficit	Accumulated Other Comprehensive Loss	Non-controlling Interest (SRX Cardio)
Balance at beginning of year at Dec. 31, 2014	$ 347,802		$ 49		$ 770,789		$ (422,797)	$ (239)
Balance at beginning of year (in shares) at Dec. 31, 2014			48,766,806
Exercise of employee stock options for cash	11,111		$ 1		11,110
Exercise of employee stock options for cash (in shares)			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	837		$ 1		836
Issuance of common stock pursuant to ESPP purchase (in shares)			30,307
Issuance of common stock in connection with public offering, net of underwriting discounts, commissions and issuance costs		$ 271,096		$ 6		$ 271,090
Issuance of stock (in shares)				6,463,750
Employee stock-based compensation expense	20,172				20,172
Compensation expense relating to stock options granted to consultants	2,794				2,794
Unrealized gain (loss) on available-for-sale securities, net of tax	89							89
Development Partner's non-controlling interest upon consolidation	2,927								$ 2,927
Net loss	(226,505)						(226,505)
Balance at end of the year at Dec. 31, 2015	430,323		$ 57		1,076,791		(649,302)	(150)	2,927
Balance at end of the year (in shares) at Dec. 31, 2015			56,359,515
Exercise of employee stock options for cash	401				401
Exercise of employee stock options for cash (in shares)			54,045
Issuance of common stock pursuant to ESPP purchase	1,278				1,278
Issuance of common stock pursuant to ESPP purchase (in shares)			62,293
Issuance of common stock pursuant to RSU and PSU release (in shares)			68,365
Employee stock-based compensation expense	30,285				30,285
Compensation expense relating to stock options granted to consultants	77				77
Unrealized gain (loss) on available-for-sale securities, net of tax	138							138
Net income attributable to non-controlling interest (SRX Cardio)	930								930
Dividends to non-controlling interest (SRX Cardio)'s shareholders	(1,700)								(1,700)
Net loss	(269,043)						(269,043)
Balance at end of the year at Dec. 31, 2016	192,689		$ 57		1,108,832		(918,345)	(12)	2,157
Balance at end of the year (in shares) at Dec. 31, 2016			56,544,218
Cumulative effect of a change in accounting principal					84		(84)
Exercise of employee stock options for cash	17,697		$ 1		17,696
Exercise of employee stock options for cash (in shares)			1,092,539
Issuance of common stock pursuant to ESPP purchase	1,945				1,945
Issuance of common stock pursuant to ESPP purchase (in shares)			85,170
Issuance of common stock pursuant to RSU and PSU release	1		$ 1
Issuance of common stock pursuant to RSU and PSU release (in shares)			272,256
Issuance of common stock in connection with public offering, net of underwriting discounts, commissions and issuance costs		$ 379,894		$ 7		$ 379,887
Issuance of stock (in shares)				7,302,500
Employee stock-based compensation expense	38,638				38,638
Compensation expense relating to stock options granted to consultants	4,646				4,646
Unrealized gain (loss) on available-for-sale securities, net of tax	(397)							(397)
Net income attributable to non-controlling interest (SRX Cardio)	470								470
Net loss	(286,090)						(286,090)
Balance at end of the year at Dec. 31, 2017	$ 349,493		$ 66		$ 1,551,728		$ (1,204,519)	$ (409)	$ 2,627
Balance at end of the year (in shares) at Dec. 31, 2017			65,296,683

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net loss	$ (285,620)	$ (268,113)	$ (226,505)
Adjustments to reconcile net loss to cash used in operating activities:
Depreciation and amortization	2,410	1,924	1,311
Net amortization/accretion on investment securities	(235)	1,113	3,174
Non-cash interest expense	11,603	61
Stock-based compensation expense	43,284	30,362	22,858
Remeasurement loss on embedded derivatives liabilities	4,562
Loss on assets disposal	52
Change in reserve for uncertain tax position			(365)
Changes in operating assets and liabilities:
Inventories	(1,099)
Receivables from collaborations	(3,750)	1,000	(943)
Prepaid research and development	6,565	9,677	(15,290)
Prepaid expenses and other current assets	(6,330)	378	1,001
Prepaid and other long-term assets	(4,395)	6,779	3,619
Accounts payable	(5,242)	4,308	(4,061)
Accrued compensation and employee benefits	6,720	(653)	2,054
Accrued research and development	21,155	(377)	11,650
Accrued and other liabilities	1,856	(892)	1,531
Deferred revenue	(15,796)	18,747	(9,569)
Other long-term liabilities	(865)	(769)	2,281
Net cash used in operating activities	(225,125)	(196,455)	(207,252)
Investing activities
Purchases of property and equipment	(1,236)	(1,864)	(4,746)
Decrease (increase) in restricted cash (SRX Cardio)	5	163	(341)
Purchase of intangible assets	(5,000)
Purchases of investments	(575,624)	(252,323)	(266,068)
Proceeds from maturities of investments	353,088	394,730	324,100
Net cash (used in) provided by investing activities	(228,767)	140,706	52,945
Financing activities
Proceeds from debt issuance, net	48,000
Proceeds from issuance of common stock, net	380,552		272,216
Debt issuance costs paid	(556)
Payment of public offering costs	(658)	(242)	(882)
Proceeds from issuance of common stock pursuant to equity award plans	19,642	1,683	11,948
Dividends to Noncontrolling interest (SRX Cardio)'s shareholders		(1,700)
Proceeds from long-term notes payable		50,000
Proceeds from long-term obligation to Collaborator		8,000
Net cash provided by financing activities	446,980	57,741	283,282
Net increase/(decrease) in cash and cash equivalents	(6,912)	1,992	128,974
Cash and cash equivalents at beginning of year	188,480	186,488	57,514
Cash and cash equivalents at end of year	$ 181,568	188,480	186,488
Noncash investing and financing activities:
Net change in accrued offering cost		$ (238)	238
Net change in accounts payable related to purchase of property and equipment			$ 5

Organization

Organization	12 Months Ended
	Dec. 31, 2017
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. On June 23, 2017, we received marketing approval from the U.S. Food and Drug Administration (“FDA”) for Bevyxxa® (betrixaban), an oral once-daily Public Offerings 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 the 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 the 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. In September 2017, we completed an underwritten public offering of 7,302,500 shares of our common stock, which included 952,500 shares of common stock issued pursuant to the over-allotment option granted to the underwriters, at a public offering price of $55.00 per share. The total proceeds from the offering and over-allotment, net of underwriting discounts and commissions of approximately $21.1 million, were approximately $380.6 million. After deducting offering expenses of approximately $0.7 million, net proceeds to us were approximately $379.9 million.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
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 SRX Cardio,LLC (“SRX Cardio’) 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, 2017. For the consolidated VIE, we record net income attributable to noncontrolling interests in our Consolidated Statements of Operations equal to the percentage of the economic or Reclassification Certain immaterial reclassifications have been made to prior period amounts to conform to current period presentation. This reclassification did not have an impact on our results of operations or financial condition as of December 31, 2017. 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 , carrying value of notes payable and long term debt, 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. Intangible Assets Intangible assets include an in-process research and development asset related to our consolidated VIE and a milestone payment made to Millennium Pharmaceuticals, Inc. (“Millennium) upon FDA approval of betrixaban. The in-process research and development asset is considered to be indefinite-lived until the completion or abandonment of the associated research and development efforts. If the project is completed, which generally occurs if and when regulatory approval to market a product is obtained, the carrying value of the related intangible asset is amortized as a part of cost of sales over the remaining estimated life of the asset beginning in the period in which the project is completed. If the asset becomes impaired or is abandoned, the carrying value of the related intangible asset is written down to its fair value and an impairment charge is taken in the period in which the impairment occurs. The in-process research and development asset is tested for impairment on an annual basis, and more frequently if indicators are present or changes in circumstances suggest that impairment may exist. Please refer to Note 8, “Asset Acquisition and License Agreements,” for further information. A milestone payment made pursuant to the regulatory approval of betrixaban in the United States is considered to be finite-lived and will be amortized on a straight-line basis over the remaining estimated patent life. The intangible asset with finite useful life is reviewed for impairment when facts or circumstances suggest that the carrying value of the asset may not be recoverable. 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. Inventories Inventories are stated at the lower of cost or estimated net realizable value, on a first-in, first-out, or FIFO, basis. We primarily use actual costs to determine our cost basis for inventories. Prior to the regulatory approval of our product candidates, we incur expenses for the manufacture of drug product that could potentially be available to support the commercial launch of our products. Until the first reporting period when regulatory approval has been received, we record all such costs as research and development expense. Beginning in the fourth quarter of 2017, we began to capitalize inventory costs associated with betrixaban when it was determined that the inventory had a probable future economic benefit. We periodically analyze our inventory levels, and write down inventory that has become obsolete, inventory that has a cost basis in excess of its estimated realizable value and inventory in excess of expected sales requirements as cost of sales. The determination of whether inventory costs will be realizable requires estimates by management and if actual market conditions are less favorable than projected by management, write-downs of inventory may be required which would be recorded as cost of sales in the consolidated statements of operations. The active pharmaceutical ingredient (API) in betrixaban is currently produced by a single supplier. As the API has undergone significant manufacturing specific to its intended purpose at the point it is purchased by us, we classify the API as work-in-process inventory. 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. Collaboration Customer Concentration Collaboration customers who accounted for 10% or more of total collaboration and license revenues were as follows: Year Ended December 31, 2017 2016 2015 Daiichi Sankyo, Inc. 33% 29% 38% Bayer Pharma, AG and Janssen Pharmaceuticals, Inc. 29% 27% 48% Dermavant Sciences GmbH 16% 25% – Bristol-Myers Squibb Company and Pfizer Inc. 22% 19% 13% 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. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition are less than its carrying amount. Impairment, if any, is assessed using discounted cash flows or other appropriate measures of fair value. Through December 31, 2017, there have been no such losses. Deferred Rent We recognize rent expense on a straight-line basis over the noncancelable term of our operating lease and, accordingly, record the difference between cash rent payments and the recognition of rent expense as a deferred rent liability. We also record lessor-funded lease incentives, such as reimbursable leasehold improvements, as a deferred rent liability, which is amortized as a reduction of rent expense over the noncancelable term of our operating lease. Revenue Recognition We generate revenue from collaboration and license agreements for the development and commercialization of our products. Collaboration and license agreements may include non-refundable or partially refundable upfront license fees, partial or complete reimbursement of research and development costs, contingent consideration payments based on the achievement of defined collaboration objectives and royalties on sales of commercialized products. Our performance obligations under our collaborations may include the transfer of intellectual property rights (licenses), obligations to provide research and development services and related clinical drug supply, obligations to provide regulatory approval services and obligations to participate on certain development and/or commercialization committees with the collaborators. If we determine that multiple deliverables exist, the consideration is allocated to one or more units of accounting based upon the best estimate of the selling price of each deliverable. The selling price used for each deliverable will be based on vendor-specific objective evidence, if available, third-party evidence if vendor-specific objective evidence is not available, or estimated selling price if neither vendor-specific or third-party evidence is available. In order to account for multiple element arrangements, we identify the deliverables at the inception of the arrangement and each deliverable within a multiple deliverable revenue arrangement is accounted for as a separate unit of accounting if both of the following criteria are met: (1) the delivered item or items have value to the customer on a standalone basis and (2) for an arrangement that includes a general right of return relative to the delivered items, delivery or performance of the undelivered items is considered probable and substantially in our control. A delivered item or items that do not qualify as a separate unit of accounting within the arrangement shall be combined with the other applicable undelivered items within the arrangement. For a combined unit of accounting, non-refundable upfront payments are recognized in a manner consistent with the final deliverable, which has generally been ratably over the period we provide research and development services. Amounts received in advance of performance are recorded as deferred revenue in our consolidated balance sheet and are recognized as collaboration revenue. 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 received from our collaboration and license agreements are recognized as revenue if the collaboration arrangement involves the sale of services associated with the development and commercialization of our products at amounts that exceed our cost. Under certain collaboration arrangements we receive reimbursement for a portion of our research and development costs. 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. Cost of Sales – Intangible Asset Amortization Cost of sales for intangible asset amortization consists of the amortization of a capitalized milestone payment made to Millennium Pharmaceuticals, Inc. (Millennium) upon FDA approval of betrixaban. The milestone payment is amortized on a straight-line basis over the estimated remaining patent life of betrixaban. 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 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. We have 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 performance stock options (“PSOs”), market-based performance stock units (“M-PSUs”) and performance-based stock units (“PSUs”). For stock option grants including PSOs, 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 and volatility that determine the stock options fair value. We are also required to make estimates as to the probability of achieving the specific performance criteria underlying the PSOs and PSUs. 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 and restricted stock units and performance stock units granted to employees that have converted to nonemployees, are valued using the Black-Scholes option-pricing model for stock options and period-end market price for restricted stock units and performance stock units. 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. Interest Expense Notes payable and long-term debt are eligible to be repaid based on royalties from our yet to be marketed product, andexanet alfa. The recognition of interest expense requires us to estimate the total amount of future royalty payments to be generated from product sales by jurisdiction over the life of the agreement. Consequently, we impute interest on the carrying value of the notes payable and long-term debt and record interest expense using an imputed effective interest rate. We reassess the expected royalty payments each reporting period and account for any changes through an adjustment to the effective interest rate on a prospective basis, with a corresponding impact to the reclassification of our debt and note payable liabilities. The assumptions used in determining the expected repayment term of the debt and amortization period of the issuance costs requires that we make estimates that could impact the short and long-term classification of these costs, as well as the period over which these costs will be amortized. 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 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. 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 March 2016, the Financial Accounting Standards Board, or the FASB, issued Accounting Standards Update, or ASU, No. 2016-09, Improvements to Employee Share-Based Payment Accounting In May 2017, the FASB issued ASU No. 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting. In January 2017, the FASB issued ASU No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which amends the existing accounting standards for leases. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606), which amends the existing accounting standards for revenue recognition. Subsequently, the FASB has issued the following standards related to ASU 2014-09: ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations; ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing; and ASU No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients. ASU 2016-08, ASU 2016-10 and ASU 2016-12 with ASU 2014-09 (collectively, the “new revenue standard”) is effective for annual and interim periods beginning after December 15, 2017 and early adoption is permitted. The new revenue standard permits two methods of adoption: retrospectively to each prior reporting period presented (full retrospective method), or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial application (the modified retrospective method). We plan to adopt the standard in the first quarter of 2018 using the modified retrospective method. Expected impacts from the adoption of this standard could differ upon the final adoption and implementation of the standard. In connection with the adoption of the standard, we have evaluated the primary terms of our collaborative arrangements, including the performance obligations under collaboration arrangements, the allocation of consideration under these agreements, the estimated variable considerations, and the pattern of recognition for each performance obligation under the new standard. The estimated effect of adopting ASU No. 2014-09 is principally the result of applying the new standard’s guidance in accounting for variable consideration, including milestone payments or contingent payments. Under our current accounting policy, we recognize contingent or milestone payments as revenue in the period that the payment-triggering event occurred or is achieved. However, under the new revenue standard, it is possible to start to recognize contingent or milestone payments before the payment-triggering event is completely achieved, subject to management’s assessment of whether it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. While we are still in the process of completing our adoption efforts, at a minimum, we preliminarily expect revenues we had historically deferred as a result of the payments being refundable to our collaboration partner upon the occurrence of certain events and milestones we deem to be probable of achievement, totaling approximately $15 million, to be recognized as an adjustment to accumulated deficit upon the recording of our transition adjustment in the first quarter of 2018. In addition, we are in the process of implementing several new internal controls, including controls to monitor the probability of achievement of contingent milestone payments and the pattern of performance of certain performance obligations.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
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, restricted cash, 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. Treasury bills 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. In certain cases where there is limited activity or less transparency around inputs to valuation, the related assets or liabilities are classified as Level 3. Our embedded derivative liabilities are measured at fair value using a Monte Carlo simulation model and are included as a component of other long-term liabilities on the consolidated balance sheets. The embedded derivative liabilities are subject to remeasurement at the end of each reporting period, with changes in fair value recognized as a component of interest and other income (expense), net, in our consolidated statements of operations. The assumptions used in the Monte Carlo simulation model include: 1) our estimates of both the probability and timing of regulatory approval of andexanet alfa by geographical region and other related events; 2) the probability weighted net sales of andexanet alfa; 3) our risk adjusted discount rate that includes a company specific risk premium; 4) our cost of debt; 5) volatility; 6) the probability of a change in control occurring during the term of the note; and 7) the probability of an event of default. The valuation of our embedded derivative liabilities is most sensitive to the probability of andexanet alfa achieving regulatory approval given the binary nature of such an approval event and the correlation to other assumptions included in the model. There were no transfers between Level 1, Level 2 and Level 3 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 (SRX Cardio) 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, 2017 Level 1 Level 2 Level 3 Total Financial Assets: Money market funds $ 31,836 $ – $ – $ 31,836 Corporate notes and commercial paper – 313,164 – 313,164 U.S. Treasury bills and government agency securities – 170,458 – 170,458 Total financial assets $ 31,836 $ 483,622 $ – $ 515,458 Financial Liabilities: Embedded derivative liabilities $ – $ – $ 8,854 $ 8,854 December 31, 2016 Level 1 Level 2 Level 3 Total Financial Assets: Money market funds $ 6,254 $ – $ – $ 6,254 Corporate notes and commercial paper – 133,099 – 133,099 U.S. Treasury bills and government agency securities – 55,936 – 55,936 Total financial assets $ 6,254 $ 189,035 $ – $ 195,289 Financial Liabilities: Embedded derivative liabilities $ – $ – $ 246 $ 246 Level 3 liabilities are comprised of embedded derivative liabilities as described in Note 9. We estimate the fair value of our corporate notes, commercial paper and U.S. Treasury bills and government agency securities by taking into consideration valuations obtained from third-party pricing services. The pricing services utilize industry standard valuation models, including both income- and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar securities, issuer credit spreads, benchmark securities, prepayment/default projections based on historical data, and other observable inputs.

Financial Instruments

Financial Instruments	12 Months Ended
	Dec. 31, 2017
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, 2017 December 31, 2016 Estimated Estimated Unrealized Unrealized Fair Unrealized Unrealized Fair Cost Gains (Losses) Value Cost Gains (Losses) Value Money market funds $ 31,836 $ – $ – $ 31,836 $ 6,254 $ – $ – $ 6,254 Corporate notes and commercial paper 313,307 2 (145 ) 313,164 133,112 1 (14 ) 133,099 U.S. Treasury bills and government agency securities 170,724 - (266 ) 170,458 55,934 5 (3 ) 55,936 $ 515,867 $ 2 $ (411 ) $ 515,458 $ 195,300 $ 6 $ (17 ) $ 195,289 Classified as: Cash equivalents $ 162,793 $ 64,998 Short-term investments 281,589 130,291 Long-term investments 71,076 – Total cash equivalents and Investments $ 515,458 $ 195,289 At December 31, 2017, 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, 2017 and 2016.

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Dec. 31, 2017
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	5. Balance Sheet Components Inventories Inventories as of December 31, 2017 consisted of the following (in thousands): December 31, 2017 December 31, 2016 Work in process $ 1,032 $ – Finished goods 67 – Total inventories $ 1,099 $ – We began capitalizing inventory during the year ended December 31, 2017 as a result of the FDA’s approval of betrixaban, as the related costs are expected to be recoverable through the commercialization of the product. As of December 31, 2017, prepaid expenses and other current assets on the Consolidated Balance Sheet include a prepayment of $2.3 million made to a manufacturer for the purchase of inventories which we expect to be converted to finished goods within the next twelve months. A prepayment of $9.6 million is classified as prepaid and other long-term assets as the production is expected after the next twelve months and the amount is deemed recoverable. No losses were incurred on valuation of inventories at lower of cost or market value or write-off of obsolete inventories during the year ended December 31, 2017. Property and Equipment Property and equipment consists of the following (in thousands): December 31, 2017 2016 Computer equipment $ 1,329 $ 1,207 Capitalized software 1,518 1,569 Equipment 6,973 6,747 Leasehold improvements 8,000 7,529 17,820 17,052 Less accumulated depreciation and amortization (12,603 ) (10,909 ) Property and equipment, net $ 5,217 $ 6,143

Collaboration and License Agree

Collaboration and License Agreements	12 Months Ended
	Dec. 31, 2017
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, 2017 2016 2015 BMS and Pfizer $ 4,862 $ 6,583 $ 1,540 Daiichi Sankyo 7,486 10,421 4,578 Bayer and Janssen 5,424 8,248 5,740 Bayer 1,024 1,450 – Dermavant 3,750 8,750 - Other - 52 212 Total collaboration and license revenue $ 22,546 $ 35,504 $ 12,070 Bristol-Myers Squibb Company (“BMS”) and Pfizer Inc. (“Pfizer”) In January 2014, we entered into an agreement with BMS and Pfizer to further study andexanet alfa as a reversal agent for their jointly-owned, FDA-approved oral Factor Xa inhibitor, apixaban, through Phase 3 studies. As of December 31, 2017, we have no further milestone payments eligible for achievement under this agreement During the years ended December 31, 2017, 2016 and 2015, we recognized $1.8 million, $2.2 million and $1.5 million, respectively, In February 2016, we entered into a collaboration and license agreement with BMS and Pfizer whereby BMS and Pfizer obtained exclusive rights to develop and commercialize andexanet alfa in Japan. BMS and Pfizer are responsible for all development, regulatory and commercial activities in Japan and we will reimburse BMS and Pfizer for expenses they incur for research and development activities specific to fXa inhibitors other than apixaban. Pursuant to this agreement, we are obligated to provide certain research and development activities outside of Japan, provide clinical drug supply and related manufacturing services and to participate on various committees in exchange for a non-refundable upfront fee of $15.0 million. We are also eligible to receive, contingent payments totaling up to $20.0 million which may be earned upon achievement of certain regulatory events and up to $70.0 million which may be earned upon achievement of specified annual net sales volumes in Japan. We are also entitled to receive royalties ranging from 5% to15% on net sales of andexanet alfa in Japan. We concluded that the January 2014 and February 2016 agreements should each be accounted for as standalone agreements. We identified the following non-cancellable performance deliverables under the February 2016 agreement: 1) grant of intellectual property license, 2) the obligation to provide research and development services, 3) the obligation to manufacture and provide clinical supply of andexanet alfa, and 4) the obligation to participate in various committees. The February 2016 agreement also contains an obligation to manufacture and provide commercial supply of andexanet alfa which we concluded was a contingent deliverable because andexanet alfa is not yet a commercially approved product and is currently subject to additional clinical studies prior to commercial approval in Japan. We considered the provisions of the multiple-elements arrangement guidance and determined that none of the deliverables have standalone value because of our required expertise associated with the manufacturing process of andexanet alfa and the interdependency of the remaining deliverables on the clinical supply of andexanet alfa. We evaluated the timing of delivery for each of the deliverables and concluded that our obligation to participate on the various committees would be the last delivered element under the arrangement and therefore would be the basis for revenue recognition for the combined unit of accounting. The total upfront consideration under this agreement is being recognized as collaboration revenue on a straight-line basis over the estimated performance period. In the second quarter of 2017, we updated our estimated period of performance from the first quarter of 2019 to the fourth quarter of 2020 to reflect a modification to our clinical development and regulatory plans. The effect of this change in estimate was not significant. We have determined that 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. As of December 31, 2017, no amounts had been recognized as collaboration revenue for any of these milestones and all the contingent payments remained eligible for achievement. During the years ended December 31, 2017 and 2016, we recognized $3.1 million and $4.4 million, respectively, in collaboration revenue under this agreement. The deferred revenue balance under this agreement as of December 31, 2017 and 2016 was $7.6 Daiichi Sankyo, Inc. (“Daiichi Sankyo”) 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 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. In October 2016, we amended this agreement to expedite the expansion of our Phase 4 trial in exchange for an upfront fee of $15.0 million, $8.0 million of which is payable back to Daiichi Sanko based solely on quarterly royalty payments of 1% of world-wide net sales of andexanet alfa. We are also eligible to receive up to three contingent payments totaling $10.0 million payable upon achieving specified clinical site activation and patient enrollment targets. Additionally, the $2.5 million contingent payment associated with scaling up our manufacturing process from the original agreement has been removed by this amendment. We concluded that the July 2014 agreement and the October 2016 amendment are linked and should be accounted as a combined agreement. We identified the following non-cancellable performance deliverables under the combined 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 combined 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 $7.0 million nonrefundable portion of the upfront payment received pursuant to the amendment is being recognized as revenue on a straight-line basis over the estimated period of performance through the second quarter of 2019. In the fourth quarter of 2017, we updated our estimated period of performance from the third quarter of 2018 to the second quarter of 2019 to reflect a modification to our clinical development and regulatory plans. The effect of this change in estimate was not significant. The $8.0 million refundable portion of the upfront consideration represents an obligation to collaborator and will be relieved as we make royalty payments or written off should we fail to commercialize andexanet alfa. We have determined all but one of the future contingent payments meets 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. We recognized zero and $5.0 million, respectively, as collaboration revenue associated with the achievement of milestones during the years ended December 31, 2017 and 2016. As of December 31, 2017, we have milestone payments totaling up to $12.5 million that remain eligible for achievement upon the occurrence of certain clinical events and patient enrollment targets. During the years ended December 31, 2017, 2016 and 2015, we recognized $6.4 million, $9.2 million and $3.5 million, respectively, in collaboration revenue under this agreement. The deferred revenue balance under this agreement as of December 31, 2017 and 2016 was $6.1 million and $12.6 million, respectively. In March 2016, we entered into an agreement with Daiichi Sankyo to perform an ethnic sensitivity study (“ESS-Study”) of Japanese ethnicity, perform any further studies requested by the Japanese regulatory authorities and to deliver services in connection with our collaboration agreement to commercialize andexanet alfa in Japan with BMS and Pfizer. Daiichi Sankyo will reimburse us for 33% of our costs and expenses incurred to conduct the ESS-Study and between 33% and 100% of costs and expenses we incur for other studies that involve edoxaban under the terms of the arrangement. Pursuant to our agreement with Daiichi Sankyo, we are obligated to provide research and development services, clinical drug supply and related manufacturing services, regulatory approval services and to participate in a JCC in exchange for an upfront nonrefundable fee of $5.0 million. We are eligible to receive, up to two contingent payments totaling $10.0 We concluded that the March 2016 agreement should be accounted for as a standalone agreement. We identified the following non-cancellable performance deliverables under the March 2016 agreement: 1) the obligation to provide research and development services 2) the obligation to provide regulatory approval services, 3) the obligation to manufacture and provide clinical supply of andexanet alfa, and 4) the obligation to participate in the JCC. We considered the provisions of the multiple-element arrangement guidance and determined that none of the deliverables have standalone value and accordingly will be accounted for as a single unit of accounting. The total upfront consideration received under this agreement is being recognized as collaboration revenue on a straight-line basis over the estimated performance period associated with our participation in the JCC. In the second quarter of 2017, we updated our estimated period of performance from the first quarter of 2019 to the fourth quarter of 2020 to reflect a modification to our clinical development and regulatory plans. The effect of this change in estimate was not significant. We have determined that 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 term within the agreement are commensurate with our performance to achieve the milestones after commencement of the agreement. As of December 31, 2017, no amounts had been recognized as collaboration revenue for any of these milestones and all the contingent payments remained eligible for achievement. D uring the years ended December 31, 2017 and 2016, we recognized $1.1 million and $1.3 million, respectively, in collaboration revenue under this agreement. The deferred revenue balance under this agreement as of December 31, 2017 and 2016 was $2.7 million and $3.7 million, respectively. 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. Bayer and Janssen paid us an upfront fee of $5.0 million and $0.5 million upon delivery of the final written study report. During the year ended December 31, 2015, we recognized $0.5 million in collaboration revenue under this agreement. There was no remaining deferred revenue balance under this agreement as of December 31, 2015. In January 2014, we entered into an agreement with Bayer and Janssen to study andexanet alfa as a reversal agent to rivaroxaban in our Phase 3 studies. As of December 31, 2017, we have a milestone payment of $2.0 million that remains eligible for achievement upon the occurrence of certain events associated with our manufacturing process. For the years ended December 31, 2017 and 2016, we recognized $3.0 D uring the years ended December 31, 2017, 2016 and 2015, we recognized $5.4 million, $8.2 million and $5.2 million, respectively, in collaboration revenue under this agreement. The deferred revenue balance under this agreement as of December 31, 2017 and 2016 was $1.6 million and $4.0 million, respectively. Bayer In February 2016, we entered into an agreement with Bayer to perform an ESS-Study of Japanese ethnicity, perform any further studies requested by the Japanese regulatory authorities and to deliver services, in connection with our collaboration agreement to commercialize andexanet alfa in Japan with BMS and Pfizer. Bayer will reimburse us 33% of our costs and expenses incurred to conduct the ESS-Study and between 33% and 100% of costs and expenses we incur for other studies that involve rivaroxaban under the terms of the arrangement. Pursuant to our agreement with Bayer we are obligated to provide research and development services, provide clinical drug supply and related manufacturing services, provide regulatory approval services and to participate in a JCC in exchange for an upfront nonrefundable fee of $5.0 million. We are also eligible to receive, one contingent payment of $10.0 million which is payable upon the initial regulatory approval for andexanet alfa for rivaroxaban in Japan. The $10.0 million contingent payment will be reduced to $7.0 million if Japanese regulatory approval is attained based only upon the ESS study results. We concluded that the January 2014 agreement with Bayer and Janssen and February 2016 agreement with Bayer should each be accounted for as standalone agreements. We identified the following non-cancellable performance deliverables under the February 2016 agreement: 1) the obligation to provide research and development services 2) the obligation to provide regulatory approval services, 3) the obligation to manufacture and provide clinical supply of andexanet alfa, and 4) the obligation to participate in the JCC. We considered the provisions of the multiple-element arrangement guidance and determined that none of the deliverables had standalone value and all of these obligations will be delivered throughout the estimated period of performance and accounted for as a single unit of accounting. The total upfront consideration under this agreement is being recognized as collaboration revenue on a straight-line basis over the estimated performance period through the fourth quarter of 2020. In the second quarter of 2017 we updated our estimated period of performance from the first quarter of 2019 to the fourth quarter of 2020 to reflect a modification to our clinical development and regulatory plans. The effect of this change in estimate was not significant. We have determined that the future contingent payment meets the definition of a milestone and that such milestone is 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. As of December 31, 2017, no amounts had been recognized as collaboration revenue for this milestone and the contingent payment remained eligible for achievement. D uring the years ended December 31, 2017 and 2016, we recognized $1.0 million and $1.5 million, respectively, in collaboration revenue under this agreement. The deferred revenue balance under this agreement as of December 31, 2017 and 2016 was $2.5 million and $3.5 million, respectively. Dermavant Sciences GmbH (“Dermavant”) In December 2016, we granted an exclusive, worldwide license to Dermavant to develop and commercialize cerdulatinib in topical formulation for all indications, excluding oncology, in exchange for a non-refundable upfront payment of $8.8 million and contingent development and regulatory milestones of $36.3 million and up to $100.0 million in commercial milestone payments based on worldwide annual net sales. Additionally, Dermavant is required to pay us a 9% royalty on worldwide net sales of all products commercialized under the agreement throughout the license term, which continues on a country-by-country basis until the later of the 10th anniversary of the first commercial sale or the expiration of the last valid patent. We identified the following non-contingent deliverables under the agreement, all of which had been satisfied as of December 31, 2016: 1) grant of an exclusive license to develop and commercialize cerdulatinib in topical formulation, excluding oncology During the years ended December 31, 2017 and 2016, Refer to Note 8 “Asset Acquisition and License Agreements” for discussion regarding sublicensing fees due to Astellas Pharma, Inc. (“Astellas”) resulting from this agreement. 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 years ended December 31, 2017 and 2016, costs of

Purchase Commitments

Purchase Commitments	12 Months Ended
	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Purchase Commitments	7. Purchase Commitments Commercial Supply Agreement (“CSA”) In July 2014, we entered into a CSA with AGC Biologics, formerly CMC ICOS Biologics, Inc. (“CMC”), a subsidiary of CMC Biologics S.à.r.l., a privately-held contract manufacturing organization, pursuant to which CMC will manufacture clinical and commercial supply of andexanet alfa. The terms of the CSA required us to purchase an aggregate fixed number of batches of andexanet alfa from CMC beginning in 2015 through 2021. The fixed commitment to purchase batches was divided between two manufacturing lines at CMC: (i) the 2,500 liter manufacturing line which has been used since inception of the program to supply clinical drug product, referred to as “Line A/B”; and (ii) the 6x2,000 liter manufacturing line referred to as “Line C” which was intended to satisfy the drug product requirements of our initial commercial launch. In February 2016, we filed a BLA based on the Line A/B manufacturing process and on August 17 2016, we received a Complete Response Letter (“CRL”) from the FDA that focused primarily on Line A/B manufacturing. Given the time and effort required to address the deficiencies raised in the CRL and re-submit the BLA, we made the decision to suspend manufacturing activities on Line C in order to focus on getting andexanet alfa approved using Line A/B. We recorded a charge of $27.3 million in research and development expense in the third quarter of 2016 due to this decision and related uncertainty about whether we would receive future benefits related to advance payments made for Line C manufacturing since inception of the CSA. In December 2016, we entered into an Amended Restated Commercial Supply Agreement (“aCSA”) with CMC that amends and restates the terms of the original CSA. Under the aCSA, CMC will continue to manufacture bulk drug substance for andexanet alfa under our first generation manufacturing process and will support other regulatory and manufacturing activities. The aCSA increases the number of batches to be manufactured on Line A/B, releases both parties from any obligations related to Line C, and details other services to be provided by CMC to support our regulatory applications in the United States and EU. Under the aCSA, the batch price is fixed at $1.0 million. Pursuant to the terms of the aCSA, we received a $33.7 million credit for amounts previously paid to CMC pursuant to the original 2014 agreement, which may be applied to either satisfy or partially offset specified amounts owed to CMC for services rendered under the aCSA, existing obligations/payables to CMC as of the execution date and future services to be rendered. For the year ended December 31, 2017, we utilized $8.0 The term of the aCSA is two years and may be earlier terminated by either party for the other party’s uncured material breach or insolvency. We may terminate the aCSA unilaterally if our applications for regulatory approval for andexanet alfa in the United States and EU are rejected, for any other safety, efficacy or commercial reasons that lead to the discontinuation, reduction in market demand or commercial infeasibility of andexanet alfa. Under the consolidation guidance, we determined that CMC is a VIE and we are not the primary beneficiary and therefore consolidation of CMC is not required. As of December 31, 2017, we have not provided financial or other support to CMC that was not previously contractually required. We have recorded $47,000 of accounts payable and $1.2 million of accrued research and development in the consolidated balance sheet as of December 31, 2017. The original CSA and aCSA does not require us to fund operations at CMC and therefore, historically we have quantified our maximum exposure to loss as the aggregate value of prepaid manufacturing services as of each reporting date. No such amounts were recorded as of the reporting date and thus we have no further financial exposure to losses at December 31, 2017. Further, we believe that our total exposure to losses associated with the fixed pricing terms of this agreement is de minimis given the cost per batch, number of batches and time frame over which the batches will be manufactured, pursuant to the amended agreement. Betrixaban Manufacturing Agreement In April 2016, we entered into a Manufacturing Agreement (“the Hovione Agreement”) with Hovione, Limited (“Hovione”), pursuant to which Hovione will manufacture active pharmaceutical ingredient (“API”) for betrixaban at commercial scale and perform process validation during the term of the agreement. As of December 31, 2017, we have recorded $2.3 million in prepaid expenses and other current assets and $9.6 million in prepaid and other long-term under the agreement, and to $10.8 million of additional payments throughout the term of the Hovione Agreement ending June 2019. Lonza Manufacturing Services Agreement In August 2017, we executed a Manufacturing Services Agreement with Lonza AG (“Lonza”) to develop a higher-capacity and lower cost process (“generation 2 process”) for andexanet alfa bulk drug substance. The manufacturing commitments included therein are contingent upon marketing approval by either the FDA or the EMA of andexanet alfa manufactured at the current Porrino facility under the generation 2 process and will remain in effect for a period of ten years. Additionally, the agreement provides Lonza with two separate rights to purchase shares of our common stock at a purchase price of one dollar per share, contingent upon certain events. The first purchase right will be earned by Lonza upon the approval of the generation 2 process and the commencement of process transfer activities to an additional, new facility in Switzerland. The second purchase right will be earned by Lonza upon the approval of the drug substance manufactured at the new facility and the number of shares will be determined based on the achievement of specified performance metrics at the new facility. The number of shares subject to the first and the second purchase right, each, will be the lesser of either the number of shares with an aggregate market value of $15 million based on a 20 day trailing market value average from the date the first or the second purchase right is earned by Lonza, or 500,000 shares. We measure the fair value of the equity instrument contingently issuable to Lonza by using the stock price and other measurement assumptions as of the earlier of the date at which either: (1) a commitment for performance by the counterparty has been reached; or (2) the counterparty’s performance is complete. We determined that Lonza does not have a performance commitment in this arrangement because there is no substantive disincentive for nonperformance. As such, our measurement date for the contingently issuable equity awards will be when the specified performance criteria have been achieved. Until such achievement, the contingently issuable equity awards will be measured at their then-current lowest aggregate fair value at each financial reporting date. As of December 31, 2017, the awards’ lowest aggregate fair value was zero.

Asset Acquisition and License A

Asset Acquisition and License Agreements	12 Months Ended
	Dec. 31, 2017
Research And Development [Abstract]
Asset Acquisition and License Agreements	8. Asset Acquisition and License Agreements SRX Cardio, LLC (“SRX Cardio”) In December 2015, we entered into an option agreement with SRX Cardio to explore a novel approach to develop a drug in the field of hypercholesterolemia. This agreement provided us an option to enter into an exclusive license agreement as well as responsibility to lead and fund the development effort during the option period. We made an upfront payment of $0.5 million. In September 2016, we exercised our right to enter into an exclusive license agreement. Pursuant to the terms of the agreement, we made an upfront payment of $2.2 million to acquire the license and are obligated to pay up to $152.5 million in research and development milestones related to the advancement of the program and royalties in the range of 2% to 6% of worldwide net sales. We may terminate the license agreement upon 90 days’ notice for convenience and the agreement may also be terminated by either party for a material breach by the other party. We determined that SRX Cardio is and continues to be a variable interest entity and that we hold a variable interest in SRX Cardio’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 SRX Cardio, we concluded that the variable interest was in the entity as a whole. Given the stage of development, we concluded that SRX Cardio is not considered a business as they lack the processes required to generate outputs. Further, because we control those activities most significant to SRX Cardio, we are considered to be the primary beneficiary of SRX Cardio. Accordingly, SRX Cardio is subject to consolidation and we have consolidated the financial statements of SRX Cardio by (a) eliminating all intercompany balances and transactions; and (b) allocating income or loss attributable to the noncontrolling interest in SRX Cardio to net income or loss attributable to noncontrolling interest in our consolidated statement of operations and reflecting noncontrolling interest on our consolidated balance sheet. Our interest in SRX Cardio is limited to the development of the intellectual property asset. The upfront payments of $0.5 million and $2.2 million and the obligation to fund the development plan represent our maximum exposure to loss under the agreement. We did not acquire any equity interest in SRX Cardio, any interest in SRX Cardio's cash and cash equivalents or any control over their activities that do not relate to the exclusive license agreement. SRX Cardio does not have any right to our assets except as provided in the exclusive license agreement . At the inception of the agreement, the identifiable assets, assumed liabilities and non-controlling interest of SRX Cardio were recorded at their estimated fair value upon the initial consolidation of SRX Cardio, including the in-process research and development intangible asset. We estimated the fair value of these indefinite lived intangible assets to be $3.2 million and the noncontrolling interest to be $2.9 million. The fair value was estimated using present-value models on potential contingent milestones and royalty payments (“contingent future 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, 2017, we have not provided financial or other support to SRX Cardio that was not previously contracted or required. We recorded SRX Cardio’s $173,000 and $178,000 of cash as restricted cash as of December 31, 2017 and 2016, respectively, because (a) we do not have any interest in or control over SRX Cardio'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. We recorded $470,000 as net income attributable to noncontrolling interest (SRX Cardio) on our consolidated statements of operations, reflecting a change in fair value of our contingent future payments liability to SRX Cardio as of December 31, 2017. Should the development program make substantive advancement, we expect to record increases in the fair value of the contingent milestone and royalty payments with a corresponding increase to net loss or decrease to net income attributable to Portola Shareholders. Millennium Pharmaceuticals, Inc. (“Millennium”) In 2004, we entered into an agreement to license from Millennium certain exclusive rights to research, develop and commercialize certain compounds that inhibit fXa, including betrixaban. The license agreement requires us to make license fee, milestone, royalty and sublicense sharing payments to Millennium as we develop, commercialize or sublicense betrixaban. The license agreement will continue in force, on a country-by-country basis, until the expiration of the relevant patents or ten years after the launch, whichever is later, or termination by either party pursuant to the agreement. This license agreement may be terminated by either party for the other party’s uncured material breach. In addition, we may terminate this agreement for convenience with 30 days’ advance written notice. Under the agreement, milestone payments are determined based on the indication included in our filing and become payable upon acceptance of our NDA and regulatory approval in the United States and Europe. In December 2016, the FDA accepted our NDA for betrixaban for extended-duration prophylaxis of VTE, triggering a $2.0 million milestone payment to Millennium which is recorded as a research and development expense in the consolidated statement of operations. In June 2017, betrixaban received regulatory approval in the United States, triggering a $5.0 million milestone payment to Millennium which is recorded as finite-lived intangible assets in our consolidated balance sheet and is being amortized to cost of sales on a straight-line basis over the remaining estimated patent life. Amortization expense was $300,000 for the year ended December 31, 2017. Should betrixaban receive approval in Europe, another $5.0 million will become payable by us. Future net product sales generated by us will be subject to a tier royalty ranging between 2% and 8%. A further $23.0 million in milestone payments would become due if betrixaban was approved for other indications specified in the agreement in the United States and Europe. Astellas Pharma, Inc. (“Astellas”) In 2010, we amended and restated the original license agreement with Astellas executed in August 2005. The amended and restated license agreement provides us certain exclusive rights to research, develop and commercialize Syk inhibitors. Pursuant to the agreement, we may be required to pay Astellas up to $71.5 million in milestone payments upon the achievement of certain regulatory, approval and sales events for each Syk inhibitor we develop. Additionally, 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. In December 2016, we out-licensed exclusive rights to cerdulatinib in topical formulation, excluding oncology, to Dermavant Sciences GmbH (“Dermavant”). Twenty percent of the milestone payments received from Dermavant are payable to Astellas. We recognized research and development expense in our consolidated statement of operations of $0.8 million and $1.8 million for the periods ended December 31, 2017 and 2016, respectively, associated with our payment obligation to Astellas.

Notes Payable

Notes Payable	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Notes Payable	9. Notes Payable BMS and Pfizer Promissory Notes Pursuant to the terms of the agreement, we are required to pay down the Notes each quarter in an amount equal to 5% of net sales of andexanet alfa in the United States and the EU. Should the initial regulatory approval of andexanet alfa in the United States and EU not be achieved by January 1, 2019, one hundred percent of payments due to us under the Japan License agreement and fifty percent of all other andexanet alfa license fees and milestone payments received from third party collaborators will be applied to the notes payable. In addition, if the approval of andexanet alfa in the United States and EU is not achieved by January 1, 2019, we are able to reduce the repayment amount to $60.0 million if such amount is paid by December 31, 2021 and regardless of the timing of regulatory approval, we may reduce the repayment amount to $62.5 million if such amount is paid by December 31, 2023. Any unpaid amounts shall become immediately due upon: 1) a change of control of Portola; 2) an event of default; and 3) termination of the agreement for breach. We have the right to prepay the repayment amount at any time without any penalty. The accounting for such funding agreement requires us to make certain estimates and assumptions, including timing of andexanet alfa approval, timing of royalty payments due to BMS and Pfizer, the expected rate of return to BMS and Pfizer, the split between current and long-term portions of the obligation and accretion of related interest expense. The upfront cash receipt of $50.0 million is recorded as notes payable, long term at issuance. We are accruing for interest over the term of the related note at issuance. The carrying value of the Notes at December 31, 2017, including accrued interest of $4.2 million, is $50.6 million. The total carrying value of the Notes, including accrued interest, will be classified as long-term on the consolidated balance sheet until we receive regulatory approval of andexanet alfa or until amounts are contractually payable to BMS and Pfizer. We evaluated the features of the Notes and determined that certain features require acceleration of payments such as pursuant to a change of control or an event of default, as well as the terms that adjust the total amount of interest required to be paid based upon the timing of initial regulatory approval in the United States and EU. We determined that these features (embedded derivatives) require bifurcation and fair value recognition. We determined the fair value of each derivative using a Monte Carlo simulation model taking into account the probability of these events occurring and potential repayment amounts and timing of such payments that would result under various scenarios (see Note 3). We will remeasure the embedded derivatives to fair value each reporting period until the repayment, termination or maturity of the long-term note payable. The fair value of the embedded derivatives was not material at December 31, 2017. The estimated fair value of the Notes payable at December 31, 2017 was $55.5 million and the fair value was measured using Level 3 inputs. The estimated fair market value was calculated using a Monte Carlo simulation model with inputs consistent with those used in determining the embedded derivative values as described in Note 3. Royalty-based Financing In February 2017, we entered into a purchase and sale agreement, or (“Royalty Sales Agreement”) with HealthCare Royalty Partners and its affiliates. (“HCR”) whereby HCR acquired a royalty interest in future worldwide net sales of andexanet alfa. We received $50.0 million upon closing and are due to receive an additional $100.0 million if U.S. regulatory approval of andexanet alfa is received prior to October 2018. We are required to pay HCR a royalty of 2.0% based on tiered net worldwide sales of andexanet alfa. If the additional $100.0 million is received from HCR, the tiered royalty rate will increase to a range of 7.85% to 3.58%, as the applicable rate decreases starting at worldwide net sales levels above $150 million. Total royalty payments are capped at 195% of the funded amount, however, the royalty rates are subject to increase if the timing of marketing and manufacturing approvals from the FDA is not received before the dates within 2018 specified in the Royalty Sales Agreement. If andexanet alfa is not approved for commercial sale, we have no repayment obligations under this agreement. We have evaluated the terms of the Royalty Sales Agreement and concluded that the features of the funded amount are similar to those of a debt instrument. Accordingly, we have accounted for the transaction as long-term debt. As the repayment of the funded amount is contingent upon the sales volumes of andexanet alfa, the repayment term may be shortened or extended depending on the actual sales of andexanet alfa. The repayment period is commencing from the first commercial sale of andexanet alfa in any country and expiring on the date when HCR has received cash payments totaling an aggregate of 195% of the funded amounts. We evaluated the terms of the debt and determined that certain features, such as the increase in the repayment amount up to $125.0 million upon a change of control and the variability in the royalty rates based upon the timing of regulatory approvals in the United States and EU, are embedded derivatives that require bifurcation from the debt instrument and fair value recognition. We determined the fair value of each derivative using a Monte Carlo simulation model taking into account the probability of these events occurring and potential repayment amounts and timing of such payments that would result under various scenarios, as further described in Note 3 to these consolidated financial statements. We will remeasure the embedded derivatives to fair value each reporting period until the time the features lapse and/or termination of the Royalty Sales Agreement. For the year ended December 31, 2017, we recognized a loss of $6.2 million upon remeasurement of the embedded derivatives. The effective interest rate as of December 31, 2017 was 17.5%. For the year ended December 31, 2017, accrued interest in the amount of $7.4 million was added to the principal balance of the debt. In connection with the Royalty Sales Agreement, we paid HCR a fee of $2.0 million and incurred additional debt issuance costs totaling $0.6 million, which includes expenses that we paid on behalf of HCR and expenses incurred directly by us. Debt issuance costs have been netted against the debt as of December 31, 2017 and are being amortized over the estimated term of the debt using the effective interest method. For the year ended December 31, 2017, we recognized interest expense, including amortization of the debt discount, related to the debt of $7.4 million. The assumptions used in determining the expected repayment term of the debt and amortization period of the issuance costs requires that we make estimates that could impact the short and long-term classification of these costs, as well as the period over which these costs will be amortized. The carrying value of the debt as of December 31, 2017 was $54.3 million, inclusive of accrued interest expense of $7.4 million and net of unamortized debt discount of $2.3 million. The total carrying value of the debt, including accrued interest, will be classified as long-term on the consolidated balance sheet until we achieve regulatory approval of andexanet alfa. The estimated fair value of long-term debt at December 31, 2017 was $58.8 million and the fair value was measured using Level 3 inputs. The estimated fair market value was calculated using a Monte Carlo simulation model with inputs consistent with those used in determining the embedded derivative values as described in Note 3.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	10. 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 amount to $71.9 million, $4.0 million and $0.2 million for services to be performed in 2018, 2019 and 2020, 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, provides 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, 2017, our future minimum commitments under our non-cancelable operating leases were as follows (in thousands): Year ending December 31: 2018 3,026 2019 2,764 2020 696 Total $ 6,486 Rent expense was $1.8 million, $1.8 million and $1.7 million for the years ended December 31, 2017, 2016 and 2015, 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, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Based Compensation	11. 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, 2017, we are authorized to issue 15,032,633 shares of common stock under the 2013 Plan. The 2013 Plan had 3,735,201 shares of common stock available for future issuance as of December 31, 2017, 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 our 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 2017 to employees, officers, directors and consultants. In September 2017, our Board of Directors adopted an Inducement Plan (“2017 Plan”) with 1,500,000 shares authorized for issuance to new employees entering into employment with Portola in accordance with NASDAQ Listing Rule 5635(c)(5). The 2017 Plan had 864,600 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 activities under our 2013 Plan and 2017 Plan Shares Subject to Weighted- Outstanding Average Exercise Stock Options Price Per Share Balance at December 31, 2016 5,817,116 $ 25.26 Options granted 2,139,750 40.43 Options exercised (1,080,570 ) 16.11 Options canceled (361,758 ) 32.33 Balance at December 31, 2017 6,514,538 $ 31.36 Additional information related to the status of stock options at December 31, 2017, is as follows (aggregate intrinsic value in thousands): Weighted- Average Remaining Exercise Price Contractual Aggregate Shares Per Share Life Intrinsic Value Outstanding 6,514,538 $ 31.36 7.0 $ 120,071 Vested 3,629,244 $ 25.35 5.5 $ 84,886 The aggregate intrinsic values of stock options outstanding and vested 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, 2017. The aggregate intrinsic value of stock options exercised was $39.3 million, $1.0 million and $35.9 million for the years ended December 31, 2017, 2016 and 2015, respectively. The weighted-average grant date fair value of employee stock options granted during the years ended December 31, 2017, 2016 and 2015 was $24.08, $17.15 and $22.84 per share, respectively. The total estimated grant date fair value of stock options vested during the years ended December 31, 2017, 2016 and 2015 was $23.0 million, $20.8 million and $12.0 million, respectively. We recognized stock-based compensation expenses of $25.5 Performance Stock Options (“PSOs”) In May 2016, the Compensation Committee of our Board of Directors approved the commencement of granting performance stock option awards to our executive and senior officers. PSOs represent a contingent right to purchase our Common Stock upon achievement of specified conditions. The PSOs granted in May 2016 will vest upon the achievement of certain regulatory and manufacturing goals related to our lead programs. We recognized stock-based compensation expense of $2.3 million and $0.5 million in 2017 and 2016, respectively, relating to these PSOs. As of December 31, 2017, the stock-based compensation expense for these PSOs had been fully recognized. The following table summarizes PSO activities under our 2013 Plan and related information: Shares Subject to Weighted- Outstanding Average Exercise Stock Options Price Per Share Balance at December 31, 2016 180,752 $ 23.76 Options granted – – Options exercised (11,969 ) 23.76 Options canceled (4,000 ) 23.76 Balance at December 31, 2017 164,783 $ 23.76 Additional information related to the status of PSOs at December 31, 2017, is as follows (aggregate intrinsic value in thousands): Weighted- Average Remaining Exercise Price Contractual Aggregate Shares Per Share Life Intrinsic Value Outstanding 164,783 $ 23.76 7.9 $ 4,106 Vested 164,783 $ 23.76 7.9 $ 4,106 The aggregate intrinsic value of PSOs exercised was $0.4 million for the year ended December 31, 2017. The weighted-average grant date fair value of PSOs granted during the year ended December 31, 2017 was $23.76 Restricted stock units (“RSUs”) 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 in 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 activities under our 2013 Plan and 2017 Plan and related information: Shares Weighted- Subject to Average grant Outstanding date fair value RSU's per share Balance at December 31, 2016 546,507 $ 28.38 RSUs granted 343,800 27.15 RSUs released (211,882 ) 28.26 RSUs canceled (78,091 ) 27.19 Balance at December 31, 2017 600,334 $ 27.87 Additional information related to the status of RSUs at December 31, 2017, is as follows (aggregate intrinsic value in thousands): Remaining Contractual Aggregate Shares Life Intrinsic Value Outstanding 600,334 0.9 $ 29,224 The total grant date fair value and the total vest date fair value of RSUs vested during the years ended December 31, 2017 and 2016 was $6.0 million and $1.7 million, respectively. The weighted-average grant date fair value of RSUs granted during the years ended December 31, 2017, 2016 and 2015 was $27.15, $28.01 and $30.74 per share respectively. We recognized stock-based compensation expenses of $8.1 million, $5.3 million and $1.5 million in the years ended December 31, 2017, 2016 and 2015, respectively, relating to these RSUs. As of December 31, 2017, there was $9.8 million of unrecognized compensation costs related to these RSUs, which is expected to be recognized over an estimated weighted-average period of 1.5 years. Performance stock units In January 2015, the Compensation Committee of our Board of Directors approved the commencement of granting performance stock units to our employees. PSUs are share awards that entitle the holder to receive freely tradable shares of our Common Stock upon achievement of specified market or performance conditions. In January 2016, the Compensation Committee of our Board of Directors approved a program to award up to 102,906 PSUs to the management team based on the achievement of certain commercial and regulatory goals related to andexanet alfa and betrixaban, respectively. In January 2017, the Compensation Committee of our Board of Directors approved a program to award up to 143,750 PSUs to the management team based on the achievement of certain regulatory goals related to andexanet alfa. The following table summarizes PSU activities under our 2013 Plan and related information: Shares Weighted- Subject to Average grant Outstanding date fair value PSU's per share Balance at December 31, 2016 285,866 $ 29.24 PSUs granted 143,750 25.54 PSU's released (60,374 ) 35.97 PSUs canceled (64,488 ) 33.09 Balance at December 31, 2017 304,754 $ 25.34 Additional information related to the status of PSUs at December 31, 2017, is as follows (aggregate intrinsic value in thousands): Remaining Contractual Aggregate Shares Life Intrinsic Value Outstanding 304,754 1.0 $ 14,835 The total grant date fair value and the total vest date fair value of PSUs vested in 2017 was $2.1 million and $3.1 million, respectively. The total grant date fair value and the total vest date fair value of PSUs vested in 2016 was $0.7 million and $0.4 million, respectively. None of the PSUs vested in 2015. The weighted-average grant date fair value of PSUs granted during the years ended December 31, 2017, 2016 and 2015 was $25.54, $33.49 and $29.35 per share, respectively We recognized stock-based compensation expenses of $2.4 million, $2.5 million and $2.3 million in the years ended December 31, 2017, 2016 and 2015, respectively, relating to these PSUs . As of December 31, 2017, there was $18,000 of compensation costs related to these PSUs, which is expected to be recognized over an estimated weighted-average period of 1.0 year. Employee Stock Purchase Plan (“ESPP”) The Board of Directors adopted the 2013 ESPP, effective upon the completion of the initial public offering of our common stock. As of December 31, 2017, 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 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 50,000, 52,000 and 66,041 shares with average exercise prices of $38.14, $24.85 and $40.85 per share, respectively, during the years ended December 31, 2017, 2016, and 2015, respectively. These options vest upon grant or various terms up to four years. We recognized non-employees stock compensation expense of $3.9 million, less than $0.1 million and $2.8 million during the years ended December 31, 2017, 2016 and 2015 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. The compensation costs of these arrangements are subject to remeasurement over the vesting terms as earned. Stock-Based Compensation Stock-based compensation expense is reflected in the consolidated statements of operations as follows (in thousands): Year Ended December 31, 2017 2016 2015 Research and development $ 19,779 $ 12,905 $ 11,653 Selling, general and administrative 23,505 17,457 11,205 Total stock-based compensation $ 43,284 $ 30,362 $ 22,858 Valuation Assumptions The fair value of our stock options including performance 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, our estimate of expected volatility is based on the weighted average volatility of other companies with similar products under development, market, size and other factors and our volatility. 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, 2017 2016 2015 Risk-free interest rate Stock options 1.70%-2.27% 1.01%-2.10% 1.54%-1.93% Performance stock options – 1.34%-1.50% – ESPP 0.47%-1.10% 0.26%-0.50% 0.14% Expected term Stock options 5.0 -6.1 years 5.0 -6.1 years 6.0 years Performance stock options – 5.4 -6.4 years – ESPP 0.5 years 0.5 years 0.5 years Expected volatility Stock options 60%-65% 62% - 66% 64% - 66% Performance stock options – 65%-66% – ESPP 61%-80% 54%-99% 62% Dividend yield Stock options – – – Performance stock options – – – ESPP – – –

Net Loss per Share Attributable

Net Loss per Share Attributable to Portola Common Stockholders	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Net Loss per Share Attributable to Portola Common Stockholders	12. 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, 2017 2016 2015 Stock options to purchase Common Stock 6,514,538 5,817,116 4,731,483 Performance stock options 164,783 180,752 – Restricted stock units 600,334 546,507 167,750 Performance stock units 304,754 285,866 205,261 Employee stock purchase plan 32,325 37,368 15,606 Common stock warrants 1,500 1,500 1,500 Up to one million shares may be contingently issued, if certain performance conditions are met under an agreement with one of our contract manufacturers.

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2017
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plan	13. 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 for the years ended December 31, 2017, 2016 and 2015. During the years ended December 31, 2017, 2016 and 2015, we recognized total expense of $910,000, $819,000 and $525,000, respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	14. Income Taxes The income tax provision consists of the following (in thousands): Year Ended December 31, 2017 2016 Current: Federal $ – $ – State – – Foreign – – – - Deferred: Federal $ – $ – State – – Foreign – – – – Total provision for income taxes $ - $ - We did not record an income tax expense for the year ended December 31, 2017 and 2016. We recorded an income tax benefit of $0.4 million for the year ended December 31, 2015. The effective tax rate of our provision for income taxes differs from the federal statutory rate as follows: Year Ended December 31, 2017 2016 2015 Federal statutory income tax rate 34.0 % 34.0 % 34.0 % State income taxes, net of federal benefit 0.0 % 0.0 % -6.6 % Federal and state credits 8.9 % 9.5 % 2.5 % Excess tax benefit 8.6 % 0.0 % 0.0 % Stock based compensation 0.1 % -0.1 % 0.0 % FIN 48 release 0.0 % 0.0 % 0.2 % Other -0.1 % 0.1 % 0.0 % Tax impact due to tax rate reduction -47.7 % 0.0 % 0.0 % Change in valuation allowance 2.6 % -38.6 % -29.9 % Foreign Rate Differential -6.4 % -4.9 % 0.0 % Total tax benefit 0.0 % 0.0 % 0.2 % The components of U.S. deferred tax assets and (liabilities) are as follows (in thousands): December 31, 2017 2016 Deferred tax assets: Federal and state net operating loss carryforwards $ 203,897 $ 235,015 Federal and state research tax credit carryforwards 21,238 17,927 Federal Orphan Drug Credit 96,750 60,822 Deferred revenue 17,538 15,566 Stock options 15,995 18,734 Capitalized acquisition costs - 819 Other 7,529 16,298 Net deferred tax assets before valuation allowance 362,947 365,181 Valuation allowance (362,947 ) (365,181 ) Net deferred tax assets $ – $ – We received orphan designation and were eligible to claim a federal orphan drug credit starting in 2015 and reported the credit in 2017 and 2016. 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, we believe 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 decreased by approximately $2.2 million for the year ended December 31, 2017, which consists of $133.9 million increase offset by $136.1 million decrease due to the remeasurement of the ending deferred tax assets and liabilities at 21%. The valuation allowance increased by approximately $114.2 million for the year ended December 31, 2016. As of December 31, 2017, we had net operating loss carryforwards for federal income tax purposes of approximately $865 million and federal research tax credits of approximately $18 million and orphan drug credit of $114 million, which expire at various dates in the period from 2024 to 2037. We also have California net operating loss carry forwards of approximately $222 million which expire at various dates in the period from 2018 to 2032 and California research tax credits of approximately $8 million, which can be carried forward indefinitely. Our federal and state net operating loss carryforwards as of December 31, 2017 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 reduction of our income tax provision in our consolidated financial statements. Internal Revenue Code Section 382 limits the use of net operating loss and tax credit carryforwards in certain situations where changes occur in the stock ownership of a company. In the event that we had a change of ownership, utilization of the net operating loss and tax credit carryforwards may be limited under section 382. 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 2015, and by the material state and local tax authorities for tax returns filed before 2014. 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, 2017 2016 2015 Unrecognized tax benefits, beginning of period $ 13,865 $ 3,228 $ 2,906 Increases due to current period positions 7,046 6,919 1,091 Decreases due to current period positions – – – Increase due to prior period positions – 4,266 – Decreases due to prior period positions (181 ) (548 ) (404 ) Decreases due to the lapse of statutes of limitations – - (365 ) Unrecognized tax benefits, end of period $ 20,730 $ 13,865 $ 3,228 The amount of unrecognized income tax benefits that, if recognized, would affect our effective tax rate was $0 as of December 31, 2017 and December 31, 2016. If the $20.7 million and $13.9 million of unrecognized income tax benefits as of December 31, 2017 and 2016, respectively, is recognized, there would be no impact to the effective tax rate as any change will fully offset the valuation allowance. We do not expect that the unrecognized tax benefit will change within the next 12 months. We recognize interest and penalties related to unrecognized tax benefits within income tax expense. Accrued interest and penalties are included within the related tax liability line in the accompanying consolidated balance sheets. Due to our net operating losses, we have not accrued any interest or penalty for any of our uncertain tax benefits as of December 31, 2017 and 2016. On December 22, 2017 President Donald Trump signed into U.S. law the Tax Reform Act. ASC Topic 740, Accounting for Income Taxes, requires companies to recognize the effect of tax law changes in the period of enactment even though the effective date for most provisions is for tax years beginning after December 31, 2017, or in the case of certain other provisions of the law, January 1, 2018. As a result of Tax Reform Act, the U.S. statutory tax rate was lowered from 35% to 21%, effective on January 1, 2018. We are required to remeasure our U.S. deferred tax assets and liabilities to the new tax rate. We reduced our net deferred tax assets by $136.1 million as a provisional amount due to the remeasurement which was offset by a full valuation allowance, and therefore, it had no impact to our provision for income taxes for the year ended December 31, 2017. Given the significance of the legislation, the SEC staff issued Staff Accounting Bulletin ("SAB") No. 118 (SAB 118), which allows registrants to record provisional amounts during a one year “measurement period”. However, the measurement period is deemed to have ended earlier when the registrant has obtained, prepared, and analyzed the information necessary to finalize its accounting. During the measurement period, impacts of the law are expected to be recorded at the time a reasonable estimate for all or a portion of the effects can be made, and provisional amounts can be recognized and adjusted as information becomes available, prepared, or analyzed. Amounts recorded, where we consider accounting to be provisional for the year ended December 31, 2017, principally relate to the impact of corporate income tax rate reduction on the deferred tax assets, on the corresponding change of deferred tax assets’ valuation allowance, and limitations on deductibility of compensation paid to certain highly paid employees. The changes included in the Tax Reform Act are broad and complex. The final transition impacts of the Tax Reform Act may differ from the above estimate, possibly materially, due to, among other things, changes in interpretations of the Tax Reform Act, any legislative action to address questions that arise because of the Tax Reform Act, and changes in accounting standards for income taxes or related interpretations in response to the Tax Reform Act, or any updates or changes to estimates that we have utilized to calculate the transition impacts.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	15. 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, 2017, 2016, and 2015, we recorded a reduction in research and development expense of $292,000, $313,000, and $352,000, respectively, related to amounts owed to us by Global Blood under the Master Services Agreement. As of December 31, 2017 and 2016, receivables due from these related parties in the amount of $26,000 and $44,000, respectively, were included in prepaid expenses and other current assets on the consolidated balance sheet.

Quarterly Financial Data (unaud

Quarterly Financial Data (unaudited)	12 Months Ended
	Dec. 31, 2017
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. 2017 2016 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Collaboration and license revenue $ 5,128 $ 3,787 $ 3,828 $ 9,803 $ 8,258 $ 4,231 $ 9,322 $ 13,693 Operating expenses $ (45,666 ) $ (69,621 ) $ (84,284 ) $ (95,654 ) $ (73,564 ) $ (61,867 ) $ (100,765 ) $ (68,893 ) Net loss $ (41,764 ) $ (69,414 ) $ (82,941 ) $ (91,501 ) $ (64,974 ) $ (57,339 ) $ (91,036 ) $ (54,764 ) Net loss (income) attributable to noncontrolling interest (SRX Cardio) $ 45 $ (240 ) $ 5 $ (280 ) $ – $ – $ (1,853 ) $ 923 Net loss attributable to Portola $ (41,719 ) $ (69,654 ) $ (82,936 ) $ (91,781 ) $ (64,974 ) $ (57,339 ) $ (92,889 ) $ (53,841 ) Net loss per share attributable to Portola common stockholders: Basic and diluted $ (0.74 ) $ (1.22 ) $ (1.41 ) $ (1.41 ) $ (1.15 ) $ (1.02 ) $ (1.64 ) $ (0.95 )

Summary of Significant Accoun24

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
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 SRX Cardio,LLC (“SRX Cardio’) 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, 2017. For the consolidated VIE, we record net income attributable to noncontrolling interests in our Consolidated Statements of Operations equal to the percentage of the economic or
Reclassification	Reclassification Certain immaterial reclassifications have been made to prior period amounts to conform to current period presentation. This reclassification did not have an impact on our results of operations or financial condition as of December 31, 2017.
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 , carrying value of notes payable and long term debt, 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.
Intangible Assets	Intangible Assets Intangible assets include an in-process research and development asset related to our consolidated VIE and a milestone payment made to Millennium Pharmaceuticals, Inc. (“Millennium) upon FDA approval of betrixaban. The in-process research and development asset is considered to be indefinite-lived until the completion or abandonment of the associated research and development efforts. If the project is completed, which generally occurs if and when regulatory approval to market a product is obtained, the carrying value of the related intangible asset is amortized as a part of cost of sales over the remaining estimated life of the asset beginning in the period in which the project is completed. If the asset becomes impaired or is abandoned, the carrying value of the related intangible asset is written down to its fair value and an impairment charge is taken in the period in which the impairment occurs. The in-process research and development asset is tested for impairment on an annual basis, and more frequently if indicators are present or changes in circumstances suggest that impairment may exist. Please refer to Note 8, “Asset Acquisition and License Agreements,” for further information. A milestone payment made pursuant to the regulatory approval of betrixaban in the United States is considered to be finite-lived and will be amortized on a straight-line basis over the remaining estimated patent life. The intangible asset with finite useful life is reviewed for impairment when facts or circumstances suggest that the carrying value of the asset may not be recoverable.
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.
Inventories	Inventories Inventories are stated at the lower of cost or estimated net realizable value, on a first-in, first-out, or FIFO, basis. We primarily use actual costs to determine our cost basis for inventories. Prior to the regulatory approval of our product candidates, we incur expenses for the manufacture of drug product that could potentially be available to support the commercial launch of our products. Until the first reporting period when regulatory approval has been received, we record all such costs as research and development expense. Beginning in the fourth quarter of 2017, we began to capitalize inventory costs associated with betrixaban when it was determined that the inventory had a probable future economic benefit. We periodically analyze our inventory levels, and write down inventory that has become obsolete, inventory that has a cost basis in excess of its estimated realizable value and inventory in excess of expected sales requirements as cost of sales. The determination of whether inventory costs will be realizable requires estimates by management and if actual market conditions are less favorable than projected by management, write-downs of inventory may be required which would be recorded as cost of sales in the consolidated statements of operations. The active pharmaceutical ingredient (API) in betrixaban is currently produced by a single supplier. As the API has undergone significant manufacturing specific to its intended purpose at the point it is purchased by us, we classify the API as work-in-process inventory.
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. Collaboration Customer Concentration Collaboration customers who accounted for 10% or more of total collaboration and license revenues were as follows: Year Ended December 31, 2017 2016 2015 Daiichi Sankyo, Inc. 33% 29% 38% Bayer Pharma, AG and Janssen Pharmaceuticals, Inc. 29% 27% 48% Dermavant Sciences GmbH 16% 25% – Bristol-Myers Squibb Company and Pfizer Inc. 22% 19% 13%
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. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition are less than its carrying amount. Impairment, if any, is assessed using discounted cash flows or other appropriate measures of fair value. Through December 31, 2017, there have been no such losses.
Deferred Rent	Deferred Rent We recognize rent expense on a straight-line basis over the noncancelable term of our operating lease and, accordingly, record the difference between cash rent payments and the recognition of rent expense as a deferred rent liability. We also record lessor-funded lease incentives, such as reimbursable leasehold improvements, as a deferred rent liability, which is amortized as a reduction of rent expense over the noncancelable term of our operating lease.
Revenue Recognition	Revenue Recognition We generate revenue from collaboration and license agreements for the development and commercialization of our products. Collaboration and license agreements may include non-refundable or partially refundable upfront license fees, partial or complete reimbursement of research and development costs, contingent consideration payments based on the achievement of defined collaboration objectives and royalties on sales of commercialized products. Our performance obligations under our collaborations may include the transfer of intellectual property rights (licenses), obligations to provide research and development services and related clinical drug supply, obligations to provide regulatory approval services and obligations to participate on certain development and/or commercialization committees with the collaborators. If we determine that multiple deliverables exist, the consideration is allocated to one or more units of accounting based upon the best estimate of the selling price of each deliverable. The selling price used for each deliverable will be based on vendor-specific objective evidence, if available, third-party evidence if vendor-specific objective evidence is not available, or estimated selling price if neither vendor-specific or third-party evidence is available. In order to account for multiple element arrangements, we identify the deliverables at the inception of the arrangement and each deliverable within a multiple deliverable revenue arrangement is accounted for as a separate unit of accounting if both of the following criteria are met: (1) the delivered item or items have value to the customer on a standalone basis and (2) for an arrangement that includes a general right of return relative to the delivered items, delivery or performance of the undelivered items is considered probable and substantially in our control. A delivered item or items that do not qualify as a separate unit of accounting within the arrangement shall be combined with the other applicable undelivered items within the arrangement. For a combined unit of accounting, non-refundable upfront payments are recognized in a manner consistent with the final deliverable, which has generally been ratably over the period we provide research and development services. Amounts received in advance of performance are recorded as deferred revenue in our consolidated balance sheet and are recognized as collaboration revenue. 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 received from our collaboration and license agreements are recognized as revenue if the collaboration arrangement involves the sale of services associated with the development and commercialization of our products at amounts that exceed our cost. Under certain collaboration arrangements we receive reimbursement for a portion of our research and development costs. 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.
Cost of Sales – Intangible Asset Amortization	Cost of Sales – Intangible Asset Amortization Cost of sales for intangible asset amortization consists of the amortization of a capitalized milestone payment made to Millennium Pharmaceuticals, Inc. (Millennium) upon FDA approval of betrixaban. The milestone payment is amortized on a straight-line basis over the estimated remaining patent life of betrixaban.
Research and Development	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 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 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. We have 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 performance stock options (“PSOs”), market-based performance stock units (“M-PSUs”) and performance-based stock units (“PSUs”). For stock option grants including PSOs, 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 and volatility that determine the stock options fair value. We are also required to make estimates as to the probability of achieving the specific performance criteria underlying the PSOs and PSUs. 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 and restricted stock units and performance stock units granted to employees that have converted to nonemployees, are valued using the Black-Scholes option-pricing model for stock options and period-end market price for restricted stock units and performance stock units. 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.
Interest Expense	Interest Expense Notes payable and long-term debt are eligible to be repaid based on royalties from our yet to be marketed product, andexanet alfa. The recognition of interest expense requires us to estimate the total amount of future royalty payments to be generated from product sales by jurisdiction over the life of the agreement. Consequently, we impute interest on the carrying value of the notes payable and long-term debt and record interest expense using an imputed effective interest rate. We reassess the expected royalty payments each reporting period and account for any changes through an adjustment to the effective interest rate on a prospective basis, with a corresponding impact to the reclassification of our debt and note payable liabilities. The assumptions used in determining the expected repayment term of the debt and amortization period of the issuance costs requires that we make estimates that could impact the short and long-term classification of these costs, as well as the period over which these costs will be amortized.
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	Foreign Currency Transactions 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.
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 March 2016, the Financial Accounting Standards Board, or the FASB, issued Accounting Standards Update, or ASU, No. 2016-09, Improvements to Employee Share-Based Payment Accounting In May 2017, the FASB issued ASU No. 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting. In January 2017, the FASB issued ASU No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which amends the existing accounting standards for leases. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606), which amends the existing accounting standards for revenue recognition. Subsequently, the FASB has issued the following standards related to ASU 2014-09: ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations; ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing; and ASU No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients. ASU 2016-08, ASU 2016-10 and ASU 2016-12 with ASU 2014-09 (collectively, the “new revenue standard”) is effective for annual and interim periods beginning after December 15, 2017 and early adoption is permitted. The new revenue standard permits two methods of adoption: retrospectively to each prior reporting period presented (full retrospective method), or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial application (the modified retrospective method). We plan to adopt the standard in the first quarter of 2018 using the modified retrospective method. Expected impacts from the adoption of this standard could differ upon the final adoption and implementation of the standard. In connection with the adoption of the standard, we have evaluated the primary terms of our collaborative arrangements, including the performance obligations under collaboration arrangements, the allocation of consideration under these agreements, the estimated variable considerations, and the pattern of recognition for each performance obligation under the new standard. The estimated effect of adopting ASU No. 2014-09 is principally the result of applying the new standard’s guidance in accounting for variable consideration, including milestone payments or contingent payments. Under our current accounting policy, we recognize contingent or milestone payments as revenue in the period that the payment-triggering event occurred or is achieved. However, under the new revenue standard, it is possible to start to recognize contingent or milestone payments before the payment-triggering event is completely achieved, subject to management’s assessment of whether it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. While we are still in the process of completing our adoption efforts, at a minimum, we preliminarily expect revenues we had historically deferred as a result of the payments being refundable to our collaboration partner upon the occurrence of certain events and milestones we deem to be probable of achievement, totaling approximately $15 million, to be recognized as an adjustment to accumulated deficit upon the recording of our transition adjustment in the first quarter of 2018. In addition, we are in the process of implementing several new internal controls, including controls to monitor the probability of achievement of contingent milestone payments and the pattern of performance of certain performance obligations.

Summary of Significant Accoun25

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
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, 2017 2016 2015 Daiichi Sankyo, Inc. 33% 29% 38% Bayer Pharma, AG and Janssen Pharmaceuticals, Inc. 29% 27% 48% Dermavant Sciences GmbH 16% 25% – Bristol-Myers Squibb Company and Pfizer Inc. 22% 19% 13%

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
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, 2017 Level 1 Level 2 Level 3 Total Financial Assets: Money market funds $ 31,836 $ – $ – $ 31,836 Corporate notes and commercial paper – 313,164 – 313,164 U.S. Treasury bills and government agency securities – 170,458 – 170,458 Total financial assets $ 31,836 $ 483,622 $ – $ 515,458 Financial Liabilities: Embedded derivative liabilities $ – $ – $ 8,854 $ 8,854 December 31, 2016 Level 1 Level 2 Level 3 Total Financial Assets: Money market funds $ 6,254 $ – $ – $ 6,254 Corporate notes and commercial paper – 133,099 – 133,099 U.S. Treasury bills and government agency securities – 55,936 – 55,936 Total financial assets $ 6,254 $ 189,035 $ – $ 195,289 Financial Liabilities: Embedded derivative liabilities $ – $ – $ 246 $ 246

Financial Instruments (Tables)

Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Investments Debt And Equity Securities [Abstract]
Cash Equivalents and Short-term and Long-term 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, 2017 December 31, 2016 Estimated Estimated Unrealized Unrealized Fair Unrealized Unrealized Fair Cost Gains (Losses) Value Cost Gains (Losses) Value Money market funds $ 31,836 $ – $ – $ 31,836 $ 6,254 $ – $ – $ 6,254 Corporate notes and commercial paper 313,307 2 (145 ) 313,164 133,112 1 (14 ) 133,099 U.S. Treasury bills and government agency securities 170,724 - (266 ) 170,458 55,934 5 (3 ) 55,936 $ 515,867 $ 2 $ (411 ) $ 515,458 $ 195,300 $ 6 $ (17 ) $ 195,289 Classified as: Cash equivalents $ 162,793 $ 64,998 Short-term investments 281,589 130,291 Long-term investments 71,076 – Total cash equivalents and Investments $ 515,458 $ 195,289

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2017
Balance Sheet Related Disclosures [Abstract]
Inventories	Inventories as of December 31, 2017 consisted of the following (in thousands): December 31, 2017 December 31, 2016 Work in process $ 1,032 $ – Finished goods 67 – Total inventories $ 1,099 $ –
Property and Equipment	Property and equipment consists of the following (in thousands): December 31, 2017 2016 Computer equipment $ 1,329 $ 1,207 Capitalized software 1,518 1,569 Equipment 6,973 6,747 Leasehold improvements 8,000 7,529 17,820 17,052 Less accumulated depreciation and amortization (12,603 ) (10,909 ) Property and equipment, net $ 5,217 $ 6,143

Collaboration and License Agr29

Collaboration and License Agreements (Tables)	12 Months Ended
	Dec. 31, 2017
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, 2017 2016 2015 BMS and Pfizer $ 4,862 $ 6,583 $ 1,540 Daiichi Sankyo 7,486 10,421 4,578 Bayer and Janssen 5,424 8,248 5,740 Bayer 1,024 1,450 – Dermavant 3,750 8,750 - Other - 52 212 Total collaboration and license revenue $ 22,546 $ 35,504 $ 12,070

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Future Minimum Commitments Under our Non-Cancelable Operating Leases	At December 31, 2017, our future minimum commitments under our non-cancelable operating leases were as follows (in thousands): Year ending December 31: 2018 3,026 2019 2,764 2020 696 Total $ 6,486

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Activities	The following table summarizes stock option activities under our 2013 Plan and 2017 Plan Shares Subject to Weighted- Outstanding Average Exercise Stock Options Price Per Share Balance at December 31, 2016 5,817,116 $ 25.26 Options granted 2,139,750 40.43 Options exercised (1,080,570 ) 16.11 Options canceled (361,758 ) 32.33 Balance at December 31, 2017 6,514,538 $ 31.36
Additional Information Related to the Status of Stock Options	Additional information related to the status of stock options at December 31, 2017, is as follows (aggregate intrinsic value in thousands): Weighted- Average Remaining Exercise Price Contractual Aggregate Shares Per Share Life Intrinsic Value Outstanding 6,514,538 $ 31.36 7.0 $ 120,071 Vested 3,629,244 $ 25.35 5.5 $ 84,886
Summary of PSO Activities	The following table summarizes PSO activities under our 2013 Plan and related information: Shares Subject to Weighted- Outstanding Average Exercise Stock Options Price Per Share Balance at December 31, 2016 180,752 $ 23.76 Options granted – – Options exercised (11,969 ) 23.76 Options canceled (4,000 ) 23.76 Balance at December 31, 2017 164,783 $ 23.76
Additional Information Related to the Status of PSOs	Additional information related to the status of PSOs at December 31, 2017, is as follows (aggregate intrinsic value in thousands): Weighted- Average Remaining Exercise Price Contractual Aggregate Shares Per Share Life Intrinsic Value Outstanding 164,783 $ 23.76 7.9 $ 4,106 Vested 164,783 $ 23.76 7.9 $ 4,106
Summary of RSU Activities	The following table summarizes RSU activities under our 2013 Plan and 2017 Plan and related information: Shares Weighted- Subject to Average grant Outstanding date fair value RSU's per share Balance at December 31, 2016 546,507 $ 28.38 RSUs granted 343,800 27.15 RSUs released (211,882 ) 28.26 RSUs canceled (78,091 ) 27.19 Balance at December 31, 2017 600,334 $ 27.87
Additional Information Related to the Status of RSUs	Additional information related to the status of RSUs at December 31, 2017, is as follows (aggregate intrinsic value in thousands): Remaining Contractual Aggregate Shares Life Intrinsic Value Outstanding 600,334 0.9 $ 29,224
Summary of PSU Activities	The following table summarizes PSU activities under our 2013 Plan and related information: Shares Weighted- Subject to Average grant Outstanding date fair value PSU's per share Balance at December 31, 2016 285,866 $ 29.24 PSUs granted 143,750 25.54 PSU's released (60,374 ) 35.97 PSUs canceled (64,488 ) 33.09 Balance at December 31, 2017 304,754 $ 25.34
Additional Information Related to the Status of PSUs	Additional information related to the status of PSUs at December 31, 2017, is as follows (aggregate intrinsic value in thousands): Remaining Contractual Aggregate Shares Life Intrinsic Value Outstanding 304,754 1.0 $ 14,835
Classification of Stock-Based Compensation Expense	Stock-based compensation expense is reflected in the consolidated statements of operations as follows (in thousands): Year Ended December 31, 2017 2016 2015 Research and development $ 19,779 $ 12,905 $ 11,653 Selling, general and administrative 23,505 17,457 11,205 Total stock-based compensation $ 43,284 $ 30,362 $ 22,858
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, 2017 2016 2015 Risk-free interest rate Stock options 1.70%-2.27% 1.01%-2.10% 1.54%-1.93% Performance stock options – 1.34%-1.50% – ESPP 0.47%-1.10% 0.26%-0.50% 0.14% Expected term Stock options 5.0 -6.1 years 5.0 -6.1 years 6.0 years Performance stock options – 5.4 -6.4 years – ESPP 0.5 years 0.5 years 0.5 years Expected volatility Stock options 60%-65% 62% - 66% 64% - 66% Performance stock options – 65%-66% – ESPP 61%-80% 54%-99% 62% Dividend yield Stock options – – – Performance stock options – – – ESPP – – –

Net Loss per Share Attributab32

Net Loss per Share Attributable to Portola Common Stockholders (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Outstanding Shares of Common Stock Equivalents Excluded from Computation of Diluted Net Loss	The following outstanding shares of common stock equivalents were excluded from the computation of diluted net loss per share attributable to Portola common stockholders for the periods presented because including them would have been antidilutive: Year Ended December 31, 2017 2016 2015 Stock options to purchase Common Stock 6,514,538 5,817,116 4,731,483 Performance stock options 164,783 180,752 – Restricted stock units 600,334 546,507 167,750 Performance stock units 304,754 285,866 205,261 Employee stock purchase plan 32,325 37,368 15,606 Common stock warrants 1,500 1,500 1,500

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Tax Provision	The income tax provision consists of the following (in thousands): Year Ended December 31, 2017 2016 Current: Federal $ – $ – State – – Foreign – – – - Deferred: Federal $ – $ – State – – Foreign – – – – Total provision for income taxes $ - $ -
Reconciliation of Effective Tax Rate for the Provision for Income Taxes	The effective tax rate of our provision for income taxes differs from the federal statutory rate as follows: Year Ended December 31, 2017 2016 2015 Federal statutory income tax rate 34.0 % 34.0 % 34.0 % State income taxes, net of federal benefit 0.0 % 0.0 % -6.6 % Federal and state credits 8.9 % 9.5 % 2.5 % Excess tax benefit 8.6 % 0.0 % 0.0 % Stock based compensation 0.1 % -0.1 % 0.0 % FIN 48 release 0.0 % 0.0 % 0.2 % Other -0.1 % 0.1 % 0.0 % Tax impact due to tax rate reduction -47.7 % 0.0 % 0.0 % Change in valuation allowance 2.6 % -38.6 % -29.9 % Foreign Rate Differential -6.4 % -4.9 % 0.0 % Total tax benefit 0.0 % 0.0 % 0.2 %
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, 2017 2016 Deferred tax assets: Federal and state net operating loss carryforwards $ 203,897 $ 235,015 Federal and state research tax credit carryforwards 21,238 17,927 Federal Orphan Drug Credit 96,750 60,822 Deferred revenue 17,538 15,566 Stock options 15,995 18,734 Capitalized acquisition costs - 819 Other 7,529 16,298 Net deferred tax assets before valuation allowance 362,947 365,181 Valuation allowance (362,947 ) (365,181 ) 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, 2017 2016 2015 Unrecognized tax benefits, beginning of period $ 13,865 $ 3,228 $ 2,906 Increases due to current period positions 7,046 6,919 1,091 Decreases due to current period positions – – – Increase due to prior period positions – 4,266 – Decreases due to prior period positions (181 ) (548 ) (404 ) Decreases due to the lapse of statutes of limitations – - (365 ) Unrecognized tax benefits, end of period $ 20,730 $ 13,865 $ 3,228

Quarterly Financial Data (una34

Quarterly Financial Data (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
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. 2017 2016 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Collaboration and license revenue $ 5,128 $ 3,787 $ 3,828 $ 9,803 $ 8,258 $ 4,231 $ 9,322 $ 13,693 Operating expenses $ (45,666 ) $ (69,621 ) $ (84,284 ) $ (95,654 ) $ (73,564 ) $ (61,867 ) $ (100,765 ) $ (68,893 ) Net loss $ (41,764 ) $ (69,414 ) $ (82,941 ) $ (91,501 ) $ (64,974 ) $ (57,339 ) $ (91,036 ) $ (54,764 ) Net loss (income) attributable to noncontrolling interest (SRX Cardio) $ 45 $ (240 ) $ 5 $ (280 ) $ – $ – $ (1,853 ) $ 923 Net loss attributable to Portola $ (41,719 ) $ (69,654 ) $ (82,936 ) $ (91,781 ) $ (64,974 ) $ (57,339 ) $ (92,889 ) $ (53,841 ) Net loss per share attributable to Portola common stockholders: Basic and diluted $ (0.74 ) $ (1.22 ) $ (1.41 ) $ (1.41 ) $ (1.15 ) $ (1.02 ) $ (1.64 ) $ (0.95 )

Organization - Additional Infor

Organization - Additional Information (Detail)	1 Months Ended			12 Months Ended
	Sep. 30, 2017USD ($)$ / sharesshares	Dec. 31, 2015USD ($)$ / sharesshares	Mar. 31, 2015USD ($)$ / sharesshares	Dec. 31, 2017Segment
Organization And Nature Of Business [Line Items]
Number of operating segment | Segment				1
Follow on offering price per share | $ / shares	$ 55	$ 48	$ 40
Proceeds from offering and over-allotment option, net		$ 162,700,000	$ 108,400,000
Proceeds from offering and over-allotment option, gross	$ 380,600,000
Offering expenses	700,000
Proceeds from offering and over-allotment option, net	$ 379,900,000
Follow-on Offering
Organization And Nature Of Business [Line Items]
Stock issued during the period | shares	7,302,500	3,593,750	2,870,000
Underwriting discounts, commissions and offering expenses, net		$ 765,000	$ 358,000
Underwriting discounts and commissions, net	$ 21,100,000
Underwriters Overallotment Option
Organization And Nature Of Business [Line Items]
Stock issued during the period | shares	952,500	468,750	374,348

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, 2017	Dec. 31, 2016	Dec. 31, 2015
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")
Concentration Risk [Line Items]
Concentration risk percentage	29.00%	27.00%	48.00%
Daiichi Sankyo, Inc ("Daiichi")
Concentration Risk [Line Items]
Concentration risk percentage	33.00%	29.00%	38.00%
Dermavant Sciences GmbH ("Dermavant")
Concentration Risk [Line Items]
Concentration risk percentage	16.00%	25.00%
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")
Concentration Risk [Line Items]
Concentration risk percentage	22.00%	19.00%	13.00%

Summary of Significant Accoun37

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Summary Of Significant Accounting Policies [Line Items]
Impairment losses		$ 0
Interest or penalties charged to the underpayment of income taxes		0
ASU No. 2016-09
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect of differed tax assets		14,000,000
Cumulative effect of change in accounting principal		$ 84,000,000
ASU 2014-09 | Accumulated Deficit | Scenario Forecast
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect of change in accounting principal	$ 15,000,000
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

Fair Values Measurements - Addi

Fair Values Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
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 liabilities transfers from level 1 to level 2	0	0
Fair value liabilities transfers from level 2 to level 1	0	0
Fair value assets transfers into level 3	0	0
Fair value assets transfers out of level 3	0	0
Fair value liabilities transfers into level 3	0	0
Fair value liabilities transfers out of level 3	$ 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, 2017	Dec. 31, 2016
Financial Assets:
Total financial assets	$ 515,458	$ 195,289
Money market funds
Financial Assets:
Total financial assets	31,836	6,254
Corporate notes and commercial paper
Financial Assets:
Total financial assets	313,164	133,099
U.S. Treasury bills and government agency securities
Financial Assets:
Total financial assets	170,458	55,936
Embedded derivative liabilities
Financial Liabilities:
Total financial liabilities	8,854	246
Fair Value, Inputs, Level 1
Financial Assets:
Total financial assets	31,836	6,254
Fair Value, Inputs, Level 1 | Money market funds
Financial Assets:
Total financial assets	31,836	6,254
Fair Value, Inputs, Level 2
Financial Assets:
Total financial assets	483,622	189,035
Fair Value, Inputs, Level 2 | Corporate notes and commercial paper
Financial Assets:
Total financial assets	313,164	133,099
Fair Value, Inputs, Level 2 | U.S. Treasury bills and government agency securities
Financial Assets:
Total financial assets	170,458	55,936
Fair Value, Inputs, Level 3 | Embedded derivative liabilities
Financial Liabilities:
Total financial liabilities	$ 8,854	$ 246

Cash Equivalents and Short-term

Cash Equivalents and Short-term and Long-term Investments Classified as Available-for-sale Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Available For Sale Securities [Line Items]
Cost	$ 515,867	$ 195,300
Unrealized Gains	2	6
Unrealized (Losses)	(411)	(17)
Estimated Fair Value	515,458	195,289
Money market funds
Schedule Of Available For Sale Securities [Line Items]
Cost	31,836	6,254
Estimated Fair Value	31,836	6,254
Corporate notes and commercial paper
Schedule Of Available For Sale Securities [Line Items]
Cost	313,307	133,112
Unrealized Gains	2	1
Unrealized (Losses)	(145)	(14)
Estimated Fair Value	313,164	133,099
U.S. Treasury bills and government agency securities
Schedule Of Available For Sale Securities [Line Items]
Cost	170,724	55,934
Unrealized Gains		5
Unrealized (Losses)	(266)	(3)
Estimated Fair Value	170,458	55,936
Cash equivalents
Schedule Of Available For Sale Securities [Line Items]
Estimated Fair Value	162,793	64,998
Short-term investments
Schedule Of Available For Sale Securities [Line Items]
Estimated Fair Value	281,589	$ 130,291
Long-term investments
Schedule Of Available For Sale Securities [Line Items]
Estimated Fair Value	$ 71,076

Financial Instruments - Additio

Financial Instruments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017
Investments Debt And Equity Securities [Abstract]
Available-for-sale securities, contractual maturities	2 years

Inventories (Detail)

Inventories (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Inventory Disclosure [Abstract]
Work in process	$ 1,032
Finished goods	67
Total inventories	$ 1,099

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)
Inventory [Line Items]
Net losses incurred on valuation of inventories or write-off	$ 0
Prepaid Expenses and Other Current Assets
Inventory [Line Items]
Prepayment for purchase of inventory	2,300,000
Prepaid And Other Long-term Assets
Inventory [Line Items]
Prepayment for purchase of inventory	$ 9,600,000

Property and Equipment (Detail)

Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 17,820	$ 17,052
Less accumulated depreciation and amortization	(12,603)	(10,909)
Property and equipment, net	5,217	6,143
Computer equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,329	1,207
Capitalized software
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,518	1,569
Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	6,973	6,747
Leasehold improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 8,000	$ 7,529

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, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	$ 9,803	$ 3,828	$ 3,787	$ 5,128	$ 13,693	$ 9,322	$ 4,231	$ 8,258	$ 22,546	$ 35,504	$ 12,070
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue									5,424	8,248	5,740
Daiichi Sankyo, Inc ("Daiichi")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue									7,486	10,421	4,578
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue									4,862	6,583	1,540
Bayer Pharma AG
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue									1,024	1,450
Dermavant Sciences GmbH (“Dermavant”)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue									$ 3,750	8,750
Other
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue										$ 52	$ 212

Collaboration and License Agr46

Collaboration and License Agreements - Additional Information (Detail) - USD ($)	1 Months Ended							3 Months Ended									12 Months Ended
	Oct. 31, 2016	Mar. 31, 2016	Feb. 29, 2016	May 31, 2015	Jul. 31, 2014	Jan. 31, 2014	Feb. 28, 2013	Jun. 30, 2019	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue									$ 9,803,000	$ 3,828,000	$ 3,787,000	$ 5,128,000	$ 13,693,000	$ 9,322,000	$ 4,231,000	$ 8,258,000	$ 22,546,000	$ 35,504,000	$ 12,070,000
Research and development																	203,701,000	246,854,000	200,376,000
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee						$ 13,000,000
Milestone payments of development and regulatory event						$ 12,000,000
Percentage of consideration received under agreement						50.00%
Non-contingent consideration being recognized as revenue over estimated period of performance																	6,500,000
Contingent consideration to be recognized after resolution of contingency																	6,500,000
Collaboration and license revenue																	4,862,000	6,583,000	1,540,000
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | January 2014 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments eligible for achievement																	0
Collaboration and license revenue																	1,800,000	2,200,000	1,500,000
Deferred revenue									9,400,000				11,200,000				9,400,000	11,200,000
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | February 2016 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue																	3,100,000	4,400,000
Deferred revenue									7,600,000				10,600,000				7,600,000	10,600,000
Non-refundable upfront fee																		15,000,000
Contingent payment receivable upon achievement of regulatory events																		20,000,000
Contingent payment receivable upon achievement of annual net sales volumes																		70,000,000
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | February 2016 Agreement | 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") | February 2016 Agreement | Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of royalties entitle to receive under agreement																	5.00%
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | February 2016 Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of royalties entitle to receive under agreement																	15.00%
Daiichi Sankyo, Inc ("Daiichi")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue																	$ 7,486,000	10,421,000	4,578,000
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																	6,400,000	9,200,000	3,500,000
Deferred revenue									6,100,000				12,600,000				6,100,000	12,600,000
Daiichi Sankyo, Inc ("Daiichi") | Future Contingent Payments | Collaborative Agreement to Study Safety and Efficacy of Andexanet Alfa
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue																	0	5,000,000
Daiichi Sankyo, Inc ("Daiichi") | July 2014 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee					$ 15,000,000
Milestone payments of development and regulatory event					20,000,000
Contingent payment receivable upon achievement					$ 5,000,000
Contingent and non-contingent consideration to be recognized after resolution of contingency																	8,000,000
Milestone payments of regulatory clinical event and patient enrollment targets																	12,500,000
Daiichi Sankyo, Inc ("Daiichi") | July 2014 Agreement | Scenario Forecast
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Non-contingent consideration being recognized as revenue over estimated period of performance								$ 7,000,000
Daiichi Sankyo, Inc ("Daiichi") | October 2016 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee	$ 15,000,000
Milestone payments of development and regulatory event	$ 2,500,000
Percentage of consideration received under agreement	1.00%
Contingent payment receivable upon achievement of annual net sales volumes	$ 8,000,000
Contingent payment receivable upon achievement	$ 10,000,000
Daiichi Sankyo, Inc ("Daiichi") | March 2016 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee		$ 5,000,000
Collaboration and license revenue																	1,100,000	1,300,000
Deferred revenue									2,700,000				3,700,000				2,700,000	3,700,000
Contingent payment receivable upon achievement		10,000,000
Reduced contingent payment receivable upon achievement		$ 7,000,000
Daiichi Sankyo, Inc ("Daiichi") | March 2016 Agreement | ESS-Study
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reimbursement of costs and expenses percentage		33.00%
Daiichi Sankyo, Inc ("Daiichi") | March 2016 Agreement | Future Contingent Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue																	0
Daiichi Sankyo, Inc ("Daiichi") | March 2016 Agreement | Minimum | Edoxaban
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reimbursement of costs and expenses percentage		33.00%
Daiichi Sankyo, Inc ("Daiichi") | March 2016 Agreement | Maximum | Edoxaban
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reimbursement of costs and expenses percentage		100.00%
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee							$ 5,000,000
Collaboration and license revenue																	5,424,000	8,248,000	5,740,000
Additional non-refundable fee							$ 500,000
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen") | January 2014 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue																	5,400,000	8,200,000	5,200,000
Deferred revenue									1,600,000				4,000,000				1,600,000	4,000,000
Milestone payments eligible for achievement of certain events																				$ 2,000,000
Collaboration revenue associated with achievement of milestones																	3,000,000	5,000,000
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
Deferred revenue																			$ 0
Bayer
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue																	1,024,000	1,450,000
Bayer | February 2016 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee			$ 5,000,000
Collaboration and license revenue																	1,000,000	1,500,000
Deferred revenue									2,500,000				$ 3,500,000				2,500,000	3,500,000
Contingent payment receivable upon achievement			10,000,000
Reduced contingent payment receivable upon achievement			$ 7,000,000
Bayer | February 2016 Agreement | ESS-Study
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reimbursement of costs and expenses percentage			33.00%
Bayer | February 2016 Agreement | Future Contingent Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue																	0
Bayer | February 2016 Agreement | Minimum | Rivaroxaban
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reimbursement of costs and expenses percentage			33.00%
Bayer | February 2016 Agreement | Maximum | Rivaroxaban
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reimbursement of costs and expenses percentage			100.00%
Dermavant Sciences GmbH (“Dermavant”)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue																	$ 3,750,000	$ 8,750,000
Percentage of royalties entitle to receive under agreement																		9.00%
Upfront payment received																		$ 8,800,000
Contingent development and regulatory milestones to be received																		36,300,000
Commercial milestone payments on worldwide annual net sales to be received																		100,000,000
Regulatory milestone payment received									$ 3,800,000
Ora, Inc. (“Ora”)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development costs, percent				60.00%
Percentage of profits entitle to receive under agreement				50.00%
Notice period for agreement termination				90 days
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																	$ 1,495,000	$ 629,000
Ora, Inc. (“Ora”) | PORTOLA PHARMACEUTICALS INC
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development costs, percent				40.00%

Purchase Commitments - Addition

Purchase Commitments - Additional Information (Detail)	1 Months Ended		3 Months Ended	12 Months Ended
	Aug. 31, 2017USD ($)Right$ / sharesshares	Dec. 31, 2016USD ($)	Sep. 30, 2016USD ($)	Dec. 31, 2017USD ($)ManufacturingLinel	Sep. 30, 2017$ / shares	Dec. 31, 2015$ / shares	Mar. 31, 2015$ / shares
Long Term Purchase Commitment [Line Items]
Charge				$ 0
Accounts payables		$ 14,546,000		9,304,000
Accrued research and development		23,818,000		44,973,000
Prepaid expenses and other current assets		2,680,000		9,010,000
Prepaid and other long-term assets		5,214,000		9,609,000
Follow on offering price per share | $ / shares					$ 55	$ 48	$ 40
Lonza Manufacturing Services Agreement
Long Term Purchase Commitment [Line Items]
Term of manufacturing commitments	10 years
Contingently issuable equity awards aggregate fair value				$ 0
Lonza Manufacturing Services Agreement | Common Stock
Long Term Purchase Commitment [Line Items]
Number of separate rights to purchase shares of common stock | Right	2
Follow on offering price per share | $ / shares	$ 1
Average trading period from date of purchase right	20 days
Maximum | Lonza Manufacturing Services Agreement | Common Stock
Long Term Purchase Commitment [Line Items]
Aggregate market value of shares to be purchased under each right	$ 15,000,000
Number of shares to be purchased under each right | shares	500,000
CMC ICOS Biologics Inc
Long Term Purchase Commitment [Line Items]
Number of manufacturing lines | ManufacturingLine				2
Purchase commitment, description				Under the aCSA, the batch price is fixed at $1.0 million.
Commercial agreement fixed commitment amount		$ 1,000,000
Purchase obligation services received				$ 33,700,000
Reduction of R&D expenses associated with manufacture batches				8,000,000
Repayment of accounts payable and accrued liabilities				$ 5,700,000
Term of commercial supply agreement				2 years
Accounts payables				$ 47,000
Accrued research and development				$ 1,200,000
CMC ICOS Biologics Inc | Research and Development Expense
Long Term Purchase Commitment [Line Items]
Charge			$ 27,300,000
CMC ICOS Biologics Inc | Line A/B
Long Term Purchase Commitment [Line Items]
Purchase commitment, description				(i) the 2,500 liter manufacturing line which has been used since inception of the program to supply clinical drug product, referred to as “Line A/B”
Purchase commitment volume | l				2,500
CMC ICOS Biologics Inc | Line C
Long Term Purchase Commitment [Line Items]
Purchase commitment, description				(ii) the 6x2,000 liter manufacturing line referred to as “Line C” which was intended to satisfy the drug product requirements of our initial commercial launch.
Purchase commitment volume | l				12,000
Hovione, Limited
Long Term Purchase Commitment [Line Items]
Prepaid expenses and other current assets				$ 2,300,000
Prepaid and other long-term assets				9,600,000
Hovione, Limited | Maximum
Long Term Purchase Commitment [Line Items]
Cancellable additional purchase commitments				$ 10,800,000

Asset Acquisition and License48

Asset Acquisition and License Agreements - Additional Information (Detail) - USD ($)

1 Months Ended

3 Months Ended

12 Months Ended

Jun. 30, 2017

Dec. 31, 2016

Sep. 30, 2016

Dec. 31, 2015

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2016

Sep. 30, 2016

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Dec. 31, 2004

Dec. 31, 2010

Asset Acquisition [Line Items]

Restricted cash (SRX Cardio)

$ 178,000

$ 173,000

$ 178,000

$ 173,000

$ 178,000

Net income attributable to non-controlling interest (SRX Cardio)

280,000

$ (5,000)

$ 240,000

$ (45,000)

(923,000)

$ 1,853,000

470,000

930,000

Milestone payment on regulatory approval

5,000,000

Research and development expense

203,701,000

246,854,000

$ 200,376,000

Millennium

Asset Acquisition [Line Items]

Notice period for agreement termination

30 days

Millennium | United States

Asset Acquisition [Line Items]

Milestone payment on regulatory approval

$ 5,000,000

Additional milestone payable for other indications approved

23,000,000

23,000,000

Millennium | Europe

Asset Acquisition [Line Items]

Milestone payable for approval event

5,000,000

5,000,000

Additional milestone payable for other indications approved

23,000,000

23,000,000

Millennium | Research and Development Expense

Asset Acquisition [Line Items]

Milestone payment

2,000,000

Millennium | Cost of Sales | United States

Asset Acquisition [Line Items]

Finite-lived intangible assets, amortization expense

300,000

Astellas Pharma Inc

Asset Acquisition [Line Items]

Percentage required to pay for any payment received under collaboration excluding royalties

20.00%

Research and development expense

1,800,000

$ 800,000

Maximum | Millennium

Asset Acquisition [Line Items]

Percentage of royalty on product sales

8.00%

Maximum | Astellas Pharma Inc

Asset Acquisition [Line Items]

Milestone payable on occurrence of specified events

$ 71,500,000

Minimum | Millennium

Asset Acquisition [Line Items]

Percentage of royalty on product sales

2.00%

SRX Cardio

Asset Acquisition [Line Items]

Variable interest entity, Terms of arrangements

Accordingly, SRX Cardio is subject to consolidation and we have consolidated the financial statements of SRX Cardio by (a) eliminating all intercompany balances and transactions; and (b) allocating income or loss attributable to the noncontrolling interest in SRX Cardio to net income or 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

$ 2,200,000

$ 500,000

Fair value of indefinite lived intangible assets

3,200,000

$ 3,200,000

Noncontrolling interest in variable Interest entity

2,900,000

2,900,000

Restricted cash (SRX Cardio)

$ 178,000

$ 173,000

$ 178,000

173,000

$ 178,000

Increase in Fair Value of Contingent Future Payments

$ 476,000

SRX Cardio | License Agreement

Asset Acquisition [Line Items]

Notice period for agreement termination

90 days

SRX Cardio | License Agreement | Maximum

Asset Acquisition [Line Items]

Research and development milestone payment obligation

$ 152,500,000

$ 152,500,000

Percentage of royalties on worldwide net sales, obligated to pay

6.00%

SRX Cardio | License Agreement | Minimum

Asset Acquisition [Line Items]

Percentage of royalties on worldwide net sales, obligated to pay

2.00%

Notes Payable - Additional Info

Notes Payable - Additional Information (Detail)	1 Months Ended		12 Months Ended
	Feb. 28, 2017USD ($)	Dec. 31, 2016USD ($)PromissoryNote	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
Carrying value of Notes		$ 49,815,000	$ 50,565,000
Loss on remeasurement of embedded derivatives			4,562,000
Long-term debt			54,251,000
HealthCare Royalty Partners and its Affiliates (“HCR”) | Andexanet Alfa
Debt Instrument [Line Items]
Accrued interest expense			7,400,000
Amount received under royalty sales agreement	$ 50,000,000
Additional amount receivable upon U.S. regulatory approval	100,000,000
Loss on remeasurement of embedded derivatives			$ 6,200,000
Effective interest rate			17.50%
Debt instrument increase, accrued interest			$ 7,400,000
Royalty sales agreement fee			2,000,000
Additional debt issuance costs			600,000
Interest expense, including amortization of debt discount			7,400,000
Long-term debt			54,300,000
Outstanding debt, net of unamortized debt discount			2,300,000
HealthCare Royalty Partners and its Affiliates (“HCR”) | Andexanet Alfa | Maximum
Debt Instrument [Line Items]
Repayment amount	$ 125,000,000
HealthCare Royalty Partners and its Affiliates (“HCR”) | Andexanet Alfa | Scenario One
Debt Instrument [Line Items]
Percentage of royalty obligated to pay of net worldwide sales	2.00%
HealthCare Royalty Partners and its Affiliates (“HCR”) | Andexanet Alfa | Scenario Two
Debt Instrument [Line Items]
Target payment for royalty obligation	$ 100,000,000
HealthCare Royalty Partners and its Affiliates (“HCR”) | Andexanet Alfa | Scenario Two | Maximum
Debt Instrument [Line Items]
Percentage of royalty obligated to pay of net worldwide sales	7.85%
HealthCare Royalty Partners and its Affiliates (“HCR”) | Andexanet Alfa | Scenario Two | Minimum
Debt Instrument [Line Items]
Percentage of royalty obligated to pay of net worldwide sales	3.58%
HealthCare Royalty Partners and its Affiliates (“HCR”) | Andexanet Alfa | Scenario Three
Debt Instrument [Line Items]
Percentage of royalty obligated to pay of net worldwide sales	195.00%
HealthCare Royalty Partners and its Affiliates (“HCR”) | Andexanet Alfa | Scenario Three | Minimum
Debt Instrument [Line Items]
Target payment for royalty obligation	$ 150,000,000
HealthCare Royalty Partners and its Affiliates (“HCR”) | Andexanet Alfa | Fair Value, Inputs, Level 3
Debt Instrument [Line Items]
Estimated fair value of long-term debt			$ 58,800,000
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")
Debt Instrument [Line Items]
Debt instrument repayment terms, description			if the approval of andexanet alfa in the United States and EU is not achieved by January 1, 2019, we are able to reduce the repayment amount to $60.0 million if such amount is paid by December 31, 2021 and regardless of the timing of regulatory approval, we may reduce the repayment amount to $62.5 million if such amount is paid by December 31, 2023. Any unpaid amounts shall become immediately due upon: 1) a change of control of Portola; 2) an event of default; and 3) termination of the agreement for breach. We have the right to prepay the repayment amount at any time without any penalty.
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | Paid by December 31, 2021
Debt Instrument [Line Items]
Repayment amount		$ 60,000,000
Repayment date		Dec. 31, 2021
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | Paid by December 31, 2023
Debt Instrument [Line Items]
Repayment amount		$ 62,500,000
Repayment date		Dec. 31, 2023
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | Andexanet Alfa
Debt Instrument [Line Items]
Percentage of license fees and milestone payments converted to notes payable upon initial regulatory approval not achieved		50.00%
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | United States and EU
Debt Instrument [Line Items]
Initial regulatory approval date		Jan. 1, 2019
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | United States and EU | Andexanet Alfa
Debt Instrument [Line Items]
Percentage of net sales to be paid in each quarter		5.00%
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | Japan License Agreement
Debt Instrument [Line Items]
Percentage of payment receivable upon initial regulatory approval not achieved		100.00%
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | Promissory Notes
Debt Instrument [Line Items]
Proceeds from notes payable		$ 50,000,000
Number of debt instruments | PromissoryNote		2
Promissory notes, face amount		$ 65,000,000
Promissory notes due date		2024-12
Accrued interest expense			$ 4,200,000
Carrying value of Notes			50,600,000
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | Promissory Notes | Fair Value, Inputs, Level 3
Debt Instrument [Line Items]
Estimated fair value of Notes payable			$ 55,500,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Lease cancellation notice period	30 days
Commitment maturing in the next fiscal year	$ 71.9
Other commitment, due in second year	4
Other commitment, due in third year	$ 0.2
Lease term expiration date	Mar. 31, 2020
Tenant improvement allowance	$ 6.3
Early termination right effective date	Mar. 31, 2018
Early termination fees	$ 1
Rent expense	$ 1.8	$ 1.8	$ 1.7

Future Minimum Commitments Unde

Future Minimum Commitments Under our Non-Cancelable Operating Leases (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Commitments And Contingencies Disclosure [Abstract]
2,018	$ 3,026
2,019	2,764
2,020	696
Total	$ 6,486

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Jan. 31, 2017	Jan. 31, 2016
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	15,032,633
Percentage increase in number of common stock outstanding	5.00%
Term of stock options granted	10 years
Vesting period	4 years
Aggregate intrinsic value of stock options exercised	$ 39,300,000	$ 1,000,000	$ 35,900,000
Total estimated grant date fair value of stock options vested	$ 23,000,000	$ 20,800,000	$ 12,000,000
Weighted-average per share fair value of stock options granted	$ 24.08	$ 17.15	$ 22.84
Stock-based compensation expense	$ 43,284,000	$ 30,362,000	$ 22,858,000
Unamortized share based compensation expected to be recognized over the remaining vesting period	$ 62,200,000
Unamortized share based compensation expected recognition period	2 years 9 months 18 days
Employee stock purchase plan
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	1,818,314
Percentage increase in number of common stock outstanding	2.00%
Common stock reserved, shares	1,611,807
Exercise price of stock options granted as a minimum percentage of fair value of common stock	85.00%
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%
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 25,500,000	21,200,000	15,800,000
Performance Stock Options (PSOs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Aggregate intrinsic value of stock options exercised	400,000
Total estimated grant date fair value of stock options vested	$ 2,400,000	0
Weighted-average per share fair value of stock options granted	$ 23.76
Stock-based compensation expense	$ 2,300,000	500,000
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	3 years
Stock-based compensation expense	$ 8,100,000	5,300,000	$ 1,500,000
Unamortized share based compensation expected to be recognized over the remaining vesting period	$ 9,800,000
Unamortized share based compensation expected recognition period	1 year 6 months
Grant date of fair value	$ 6,000,000	1,700,000
Vested date of fair value	$ 6,000,000	$ 1,700,000
Weighted-average grant date of fair value	$ 27.15	$ 28.01	$ 30.74
Performance Stock Units (PSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 2,400,000	$ 2,500,000	$ 2,300,000
Unamortized share based compensation expected to be recognized over the remaining vesting period	$ 18,000
Unamortized share based compensation expected recognition period	1 year
Grant date of fair value	$ 2,100,000	700,000
Vested date of fair value	$ 3,100,000	$ 400,000
Weighted-average grant date of fair value	$ 25.54	$ 33.49	$ 29.35
PSUs Vested during the year			0
Dividend yield	0.00%
Performance Stock Units (PSUs) | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares available for issuance					143,750	102,906
Nonemployee Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	4 years
Share based compensation, options granted	50,000	52,000	66,041
Share based compensation, options weighted average exercise price	$ 38.14	$ 24.85	$ 40.85
Stock-based compensation	$ 3,900,000	$ 100,000	$ 2,800,000
2013 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved, shares	3,735,201
2013 Equity Incentive Plan | Performance Stock Units (PSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant date of fair value	$ 25.54
2017 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved, shares	864,600
Shares available for issuance				1,500,000

Summary of Stock Option Activit

Summary of Stock Option Activities (Detail) - Employee Stock Option - 2013 and 2017 Equity Incentive Plan	12 Months Ended
	Dec. 31, 2017$ / sharesshares
Shares Subject to Outstanding Stock Options
Beginning balance | shares	5,817,116
Options granted | shares	2,139,750
Options exercised | shares	(1,080,570)
Options canceled | shares	(361,758)
Ending balance | shares	6,514,538
Weighted-Average Exercise Price Per Share
Beginning balance | $ / shares	$ 25.26
Options granted | $ / shares	40.43
Options exercised | $ / shares	16.11
Options canceled | $ / shares	32.33
Ending balance | $ / shares	$ 31.36

Status of Stock Options (Detail

Status of Stock Options (Detail) - Employee Stock Option - 2013 and 2017 Equity Incentive Plan - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Shares
Outstanding	6,514,538	5,817,116
Vested	3,629,244
Weighted-Average Exercise Price Per Share
Outstanding	$ 31.36	$ 25.26
Vested	$ 25.35
Remaining Contractual Life
Outstanding	7 years
Vested	5 years 6 months
Aggregate Intrinsic Value
Outstanding	$ 120,071
Vested	$ 84,886

Summary of PSO Activities (Deta

Summary of PSO Activities (Detail) - Performance Stock Options (PSOs) - 2013 Equity Incentive Plan	12 Months Ended
	Dec. 31, 2017$ / sharesshares
Shares Subject to Outstanding Stock Options
Beginning balance | shares	180,752
Options exercised | shares	(11,969)
Options canceled | shares	(4,000)
Ending balance | shares	164,783
Weighted-Average Exercise Price Per Share
Beginning balance | $ / shares	$ 23.76
Options exercised | $ / shares	23.76
Options canceled | $ / shares	23.76
Ending balance | $ / shares	$ 23.76

Status of PSOs (Detail)

Status of PSOs (Detail) - Performance Stock Options (PSOs) - 2013 Equity Incentive Plan - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Shares
Outstanding	164,783	180,752
Vested	164,783
Weighted-Average Exercise Price Per Share
Outstanding	$ 23.76	$ 23.76
Vested	$ 23.76
Remaining Contractual Life
Outstanding	7 years 10 months 24 days
Vested	7 years 10 months 24 days
Aggregate Intrinsic Value
Outstanding	$ 4,106
Vested	$ 4,106

Summary of RSU Activities (Deta

Summary of RSU Activities (Detail) - Restricted Stock Units (RSUs) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Weighted-Average grant date fair value per share
RSUs granted	$ 27.15	$ 28.01	$ 30.74
2013 and 2017 Equity Incentive Plan
Shares Subject to Outstanding Options
Beginning balance	546,507
RSUs granted	343,800
RSUs released	(211,882)
RSUs canceled	(78,091)
Ending balance	600,334	546,507
Weighted-Average grant date fair value per share
Beginning balance	$ 28.38
RSUs granted	27.15
RSUs released	28.26
RSUs canceled	27.19
Ending balance	$ 27.87	$ 28.38

Status of RSUs (Detail)

Status of RSUs (Detail) - Restricted Stock Units (RSUs) - 2013 and 2017 Equity Incentive Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Shares
Outstanding	600,334	546,507
Remaining Contractual Life
Outstanding	10 months 24 days
Aggregate Intrinsic Value
Outstanding	$ 29,224

Summary of PSU Activities (Deta

Summary of PSU Activities (Detail) - Performance Stock Units (PSUs) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Weighted-Average grant date fair value per share
RSUs granted	$ 25.54	$ 33.49	$ 29.35
2013 Equity Incentive Plan
Shares Subject to Outstanding Options
Beginning balance	285,866
RSUs granted	143,750
RSUs released	(60,374)
RSUs canceled	(64,488)
Ending balance	304,754	285,866
Weighted-Average grant date fair value per share
Beginning balance	$ 29.24
RSUs granted	25.54
RSUs released	35.97
RSUs canceled	33.09
Ending balance	$ 25.34	$ 29.24

Status of PSUs (Detail)

Status of PSUs (Detail) - Performance Stock Units (PSUs) - 2013 Equity Incentive Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Shares
Outstanding	304,754	285,866
Remaining Contractual Life
Outstanding	1 year
Aggregate Intrinsic Value
Outstanding	$ 14,835

Classification of Stock-Based C

Classification of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 43,284	$ 30,362	$ 22,858
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	19,779	12,905	11,653
Selling, General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 23,505	$ 17,457	$ 11,205

Summary of Weighted-Average Ass

Summary of Weighted-Average Assumptions of Fair Value Awards (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee stock purchase plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate, minimum	0.47%	0.26%
Risk-free interest rate, maximum	1.10%	0.50%
Risk-free interest rate			0.14%
Expected term	6 months	6 months	6 months
Expected volatility, minimum	61.00%	54.00%
Expected volatility, maximum	80.00%	99.00%
Expected volatility			62.00%
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate, minimum	1.70%	1.01%	1.54%
Risk-free interest rate, maximum	2.27%	2.10%	1.93%
Expected term			6 years
Expected volatility, minimum	60.00%	62.00%	64.00%
Expected volatility, maximum	65.00%	66.00%	66.00%
Employee Stock Option | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term	5 years	5 years
Employee Stock Option | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term	6 years 1 month 6 days	6 years 1 month 6 days
Performance Stock Options (PSOs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate, minimum		1.34%
Risk-free interest rate, maximum		1.50%
Expected volatility, minimum		65.00%
Expected volatility, maximum		66.00%
Performance Stock Options (PSOs) | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term		5 years 4 months 24 days
Performance Stock Options (PSOs) | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term		6 years 4 months 24 days

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, 2017	Dec. 31, 2016	Dec. 31, 2015
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	6,514,538	5,817,116	4,731,483
Performance stock options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of diluted net loss per share	164,783	180,752
Restricted stock units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of diluted net loss per share	600,334	546,507	167,750
Performance stock units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of diluted net loss per share	304,754	285,866	205,261
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	1,500	1,500
Employee stock purchase plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of diluted net loss per share	32,325	37,368	15,606

Net Loss per Share Attributab64

Net Loss per Share Attributable to Portola Common Stockholders - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017shares
Maximum | Contingently issuable shares to contract manufacturer
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of diluted net loss per share	1,000,000

Employee Benefit Plan - Additio

Employee Benefit Plan - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Compensation And Retirement Disclosure [Abstract]
Defined contribution plan maximum employee contribution of employee salary	3.00%	3.00%	3.00%
Employee benefit plans, contribution expense	$ 910,000	$ 819,000	$ 525,000

Income Tax Provision (Detail)

Income Tax Provision (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred:
Total provision for income taxes	$ 0	$ 0	$ (365,000)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax [Line Items]
Total provision (benefit) for income taxes		$ 0	$ 0	$ (365,000)
Increase (Decrease) in valuation allowance		(2,200,000)	$ 114,200,000
Increase in net deferred tax assets		133,900,000
Reduction in net deferred tax assets due to reduction in U.S. statutory tax rate		$ 136,100,000
Effective income tax rate from remeasurement of deferred tax assets and liabilities		34.00%	34.00%	34.00%
Unrecognized income tax benefits that, if recognized, would affect effective tax rate		$ 0	$ 0
Unrecognized income tax benefits		20,730,000	13,865,000	$ 3,228,000	$ 2,906,000
Accrued interest or penalty related to uncertain tax benefits		0	$ 0
Federal
Income Tax [Line Items]
Net operating loss carryforwards		$ 865,000,000
Federal | Minimum
Income Tax [Line Items]
Net operating loss carryforwards, expiration year		2,024
Federal | Maximum
Income Tax [Line Items]
Net operating loss carryforwards, expiration year		2,037
Federal | Research Tax Credit Carryforward
Income Tax [Line Items]
Tax credits carryforwards		$ 18,000,000
Federal | Orphan Drug Credit
Income Tax [Line Items]
Tax credits carryforwards		114,000,000
California
Income Tax [Line Items]
Net operating loss carryforwards		$ 222,000,000
California | Minimum
Income Tax [Line Items]
Net operating loss carryforwards, expiration year		2,018
California | Maximum
Income Tax [Line Items]
Net operating loss carryforwards, expiration year		2,032
California | Research Tax Credit Carryforward
Income Tax [Line Items]
Tax credits carryforwards		$ 8,000,000
Scenario Forecast
Income Tax [Line Items]
Effective income tax rate from remeasurement of deferred tax assets and liabilities	21.00%

Reconciliation of Effective Tax

Reconciliation of Effective Tax Rate for the Provision for Income Taxes (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
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	0.00%	0.00%	(6.60%)
Federal and state credits	8.90%	9.50%	2.50%
Excess tax benefit	8.60%	0.00%	0.00%
Stock based compensation	0.10%	(0.10%)	0.00%
FIN 48 release	0.00%	0.00%	0.20%
Other	(0.10%)	0.10%	0.00%
Tax impact due to tax rate reduction	(47.70%)	0.00%	0.00%
Change in valuation allowance	2.60%	(38.60%)	(29.90%)
Foreign Rate Differential	(6.40%)	(4.90%)	0.00%
Total tax benefit	0.00%	0.00%	0.20%

Components of U.S. Deferred Tax

Components of U.S. Deferred Tax Assets and (liabilities) (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Federal and state net operating loss carryforwards	$ 203,897	$ 235,015
Federal and state research tax credit carryforwards	21,238	17,927
Federal Orphan Drug Credit	96,750	60,822
Deferred revenue	17,538	15,566
Stock options	15,995	18,734
Capitalized acquisition costs		819
Other	7,529	16,298
Net deferred tax assets before valuation allowance	362,947	365,181
Valuation allowance	$ (362,947)	$ (365,181)

Reconciliation of the Beginning

Reconciliation of the Beginning and Ending Amount of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation Of Unrecognized Tax Benefits Excluding Amounts Pertaining To Examined Tax Returns Roll Forward
Unrecognized tax benefits, beginning of period	$ 13,865	$ 3,228	$ 2,906
Increases due to current period positions	7,046	6,919	1,091
Increase due to prior period positions		4,266
Decreases due to prior period positions	(181)	(548)	(404)
Decreases due to the lapse of statutes of limitations			(365)
Unrecognized tax benefits, end of period	$ 20,730	$ 13,865	$ 3,228

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Receivables due from related parties	$ 26,000	$ 44,000
Chief Executive Officer | Master Services Agreement
Related Party Transaction [Line Items]
Reduction in research and development expense	$ 292,000	$ 313,000	$ 352,000

Quarterly Financial Information

Quarterly Financial Information (unaudited) (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Data [Abstract]
Collaboration and license revenue	$ 9,803	$ 3,828	$ 3,787	$ 5,128	$ 13,693	$ 9,322	$ 4,231	$ 8,258	$ 22,546	$ 35,504	$ 12,070
Operating expenses	(95,654)	(84,284)	(69,621)	(45,666)	(68,893)	(100,765)	(61,867)	(73,564)	(295,225)	(305,089)	(239,245)
Net loss	(91,501)	(82,941)	(69,414)	(41,764)	(54,764)	(91,036)	(57,339)	(64,974)	(285,620)	(268,113)	(226,505)
Net loss (income) attributable to noncontrolling interest (SRX Cardio)	(280)	5	(240)	45	923	(1,853)			(470)	(930)
Net loss attributable to Portola	$ (91,781)	$ (82,936)	$ (69,654)	$ (41,719)	$ (53,841)	$ (92,889)	$ (57,339)	$ (64,974)	$ (286,090)	$ (269,043)	$ (226,505)
Net loss per share attributable to Portola common stockholders:
Basic and diluted	$ (1.41)	$ (1.41)	$ (1.22)	$ (0.74)	$ (0.95)	$ (1.64)	$ (1.02)	$ (1.15)	$ (4.81)	$ (4.76)	$ (4.36)