Portola Pharmaceuticals (PTLA) 10-Q 9 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Oct. 26, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Trading Symbol	PTLA
Entity Registrant Name	PORTOLA PHARMACEUTICALS INC
Entity Central Index Key	1,269,021
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		65,251,532

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 344,021	$ 188,480
Short-term investments	225,107	130,291
Restricted cash (SRX Cardio)	170	178
Prepaid research and development	1,888	7,299
Prepaid expenses and other current assets	8,766	2,680
Total current assets	579,952	328,928
Property and equipment, net	5,614	6,143
Intangible assets	7,996	3,151
Long-term investments	28,625
Prepaid and other long-term assets	9,609	5,214
Total assets	631,796	343,436
Current liabilities:
Accounts payable	17,463	14,546
Accrued compensation and employee benefits	8,910	4,806
Accrued research and development	24,144	23,818
Accrued and other liabilities	4,065	1,696
Deferred revenue, current portion	15,187	20,798
Total current liabilities	69,769	65,664
Notes payable, long-term	52,505	49,815
Long term debt	52,388
Long term obligation to Collaborator	8,000	8,000
Deferred revenue, long-term	17,833	24,965
Other long-term liabilities	2,912	2,303
Total liabilities	203,407	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 September 30, 2017 and December 31, 2016; 65,217,575 shares and 56,544,218 shares issued and outstanding at September 30, 2017 and December 31, 2016, respectively	67	57
Additional paid-in capital	1,538,583	1,108,832
Accumulated deficit	(1,112,571)	(918,345)
Accumulated other comprehensive loss	(37)	(12)
Total Portola stockholders’ equity	426,042	190,532
Noncontrolling interest (SRX Cardio)	2,347	2,157
Total stockholders’ equity	428,389	192,689
Total liabilities and stockholders’ equity	$ 631,796	$ 343,436

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) (Unaudited) - $ / shares	Sep. 30, 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	65,217,575	56,544,218
Common stock, shares outstanding	65,217,575	56,544,218

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Collaboration and license revenue	$ 3,828	$ 9,322	$ 12,743	$ 21,811
Operating expenses:
Cost of sales	155		155
Research and development	55,273	87,209	135,210	190,822
Selling, general and administrative	28,856	13,556	64,206	45,374
Total operating expenses	84,284	100,765	199,571	236,196
Loss from operations	(80,456)	(91,443)	(186,828)	(214,385)
Interest and other income (expense), net	663	407	952	1,036
Interest expense	(3,148)		(8,243)
Net loss	(82,941)	(91,036)	(194,119)	(213,349)
Net loss (income) attributable to noncontrolling interest (SRX Cardio)	5	(1,853)	(190)	(1,853)
Net loss attributable to Portola	$ (82,936)	$ (92,889)	$ (194,309)	$ (215,202)
Net loss per share attributable to Portola common stockholders:
Basic and diluted	$ (1.41)	$ (1.64)	$ (3.38)	$ (3.81)
Shares used to compute net loss per share attributable to Portola common stockholders:
Basic and diluted	58,940,764	56,508,426	57,569,593	56,459,418

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (82,941)	$ (91,036)	$ (194,119)	$ (213,349)
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities, net of tax	33	(49)	(25)	194
Comprehensive loss	(82,908)	(91,085)	(194,144)	(213,155)
Comprehensive loss (income) attributable to noncontrolling interest (SRX Cardio)	5	(1,853)	(190)	(1,853)
Total comprehensive loss attributable to Portola	$ (82,903)	$ (92,938)	$ (194,334)	$ (215,008)

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating activities
Net loss	$ (194,119)	$ (213,349)
Adjustments to reconcile net loss to cash used in operating activities:
Depreciation and amortization	1,667	1,423
Net amortization/accretion on investment securities	217	962
Non-cash interest expense	8,244
Stock-based compensation expense	32,405	22,464
Remeasurement loss on embedded derivatives liabilities	657
Loss on assets disposal	50
Changes in operating assets and liabilities:
Receivables from collaborators		(4,000)
Prepaid research and development	5,411	1,401
Prepaid expenses and other current assets	(6,087)	(1,537)
Prepaid and other long-term assets	(4,395)	5,677
Accounts payable	3,426	(1,286)
Accrued compensation and employee benefits	4,104	(1,942)
Accrued research and development	326	(8,762)
Accrued and other liabilities	2,081	(249)
Deferred revenue	(12,743)	16,689
Other long-term liabilities	(657)	(565)
Net cash used in operating activities	(159,413)	(183,074)
Investing activities
Purchases of property and equipment	(1,542)	(1,564)
Decrease (increase) in restricted cash (SRX Cardio)	8	(1,589)
Purchase of intangible assets	(5,000)
Purchases of investments	(373,976)	(197,650)
Proceeds from maturities of investments	250,293	294,619
Net cash (used in) provided by investing activities	(130,217)	93,816
Financing activities
Proceeds from debt issuance, net	48,000
Proceeds from issuance of common stock, net	380,552
Payment of public offering cost	(387)	(242)
Debt issuance costs paid	(557)
Proceeds from issuance of common stock pursuant to equity award plans	17,563	1,673
Net cash provided by financing activities	445,171	1,431
Net increase/ (decrease) in cash and cash equivalents	155,541	(87,827)
Cash and cash equivalents at beginning of period	188,480	186,488
Cash and cash equivalents at end of period	$ 344,021	$ 98,661

Organization

Organization	9 Months Ended
	Sep. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization	1. Organization Portola Pharmaceuticals, Inc. ® On June 23, 2017, we received marketing approval from the U.S. Food and Drug Administration, or FDA, for Bevyxxa ® 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 our 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	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Consolidation and Basis of Presentation The accompanying unaudited condensed consolidated financial statements include the amounts of Portola and its wholly-owned subsidiaries and a development partner that is a variable interest entity (a “VIE”) for which Portola is deemed, under applicable accounting guidance, to be the primary beneficiary as of September 30, 2017. The unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”), and follow the requirements of the Securities and Exchange Commission (“SEC”) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These condensed consolidated financial statements have been prepared on the same basis as our annual consolidated financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments that are necessary for a fair statement of our financial information. The results of operations for the three and nine months ended September 30, 2017 are not necessarily indicative of the results to be expected for the year ending December 31, 2017 or for any other interim period or for any other future year. The condensed consolidated balance sheet as of December 31, 2016 has been derived from the audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete financial statements. The accompanying unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2016 included in our Annual Report on Form 10-K filed on March 1, 2017 with the SEC. 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, 2016. Use of Estimates The preparation of condensed 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 condensed 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 including short-term and long-term classification, embedded derivative liabilities, interest expense, income taxes, in-process research and development, the consolidation of VIEs and deconsolidation of VIEs and stock-based compensation. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results may differ from those estimates. Variable Interest Entities We review agreements we enter into with third party entities, pursuant to which we may have a variable interest in that 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 operations and financial position of the VIE into our consolidated financial statements. Our determination as to 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 In-process research and development asset relates to our consolidated VIE and 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 product revenues 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. Intangible assets with finite useful lives are amortized over their estimated useful lives, on a straight-line basis, and are reviewed for impairment when facts or circumstances suggest that the carrying value of these assets may not be recoverable. See Note 7, “Asset Acquisition and License Agreements,” to these condensed consolidated financial statements for further information. Cash and Cash Equivalents Cash and cash equivalents consist of cash and other highly liquid investments with original maturities of three months or less from the date of purchase. Investments in Marketable Securities All investments in marketable securities have been classified as “available-for-sale” and are carried at estimated fair value as determined based upon quoted market prices or pricing models for similar securities. Management determines the appropriate classification of our investments in debt securities at the time of purchase and reevaluates such designation as of each balance sheet date. Unrealized gains and losses are excluded from earnings and were reported as a component of accumulated comprehensive income (loss). Realized gains and losses and declines in fair value judged to be other than temporary, if any, on available-for-sale securities are included in interest and other income, net. The cost of securities sold is based on the specific-identification method. Interest on marketable securities is included in interest and other income, net. Collaboration Collaboration customers who accounted for 10% or more of total collaboration and license revenues were as follows: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Daiichi Sankyo, Inc. 53 % 41 % 49 % 39 % Bayer Pharma, AG and Janssen Pharmaceuticals, Inc. 14 % 36 % 15 % 34 % Bristol-Myers Squibb Company and Pfizer Inc. 27 % 19 % 30 % 22 % 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 condensed 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. 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 classification of our debt and note payable liabilities. 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 the same as basic net loss per share attributable to Portola Common Stockholders, since the effects of potentially dilutive securities are antidilutive. Recent Accounting Pronouncements In May 2017, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“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 March 2016, the FASB issued ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers Revenue from Contracts with Customers Principal versus Agent Considerations Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients 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. Although we are still evaluating our contracts and assessing all the potential impacts of the standard, we anticipate the adoption may have a material impact on our condensed consolidated financial statements. Specifically, the timing of recognition for certain contingent payments from our collaborators may be impacted by the adoption of the new revenue standard. ASU No. 2014-09 differs from the current accounting standard in many respects, such as in the 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. In February 2016, the Financial Accounting Standards Board (FASB) issued ASU No. 2016-02, Leases (Topic 842), which amends the existing accounting standards for leases. The new standard requires lessees to record a right-of-use asset and a corresponding lease liability on the balance sheet (with the exception of short-term leases). For lessees, leases will continue to be classified as either operating or financing in the income statement. This ASU becomes effective for the Company in the first quarter of fiscal year 2019 and early adoption is permitted. This ASU is required to be applied with a modified retrospective approach and requires application of the new standard at the beginning of the earliest comparative period presented. The Company is currently evaluating the impact that ASU 2016-02 will have on its financial statements.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 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 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. 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 condensed 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 condensed 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) probability weighted net sales of andexanet alfa; 3) our risk adjusted discount rate that includes a company specific risk premium; 4) cost of debt; 5) volatility; 6) the probability of a change in control occurring during the term of the note; and 7) 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. In certain cases where there is limited activity or less transparency around inputs to valuation, securities are classified as Level 3. Our noncontrolling interest includes the fair value of the contingent milestone and royalty payments, which is valued based on Level 3 inputs. See Note 7, " ," The following table sets forth the fair value of our financial assets and liabilities, allocated into Level 1, Level 2 and Level 3, that were measured on a recurring basis (in thousands): September 30, 2017 Level 1 Level 2 Level 3 Total Financial Assets: Money market funds $ 107,888 $ — $ — $ 107,888 Corporate notes and commercial paper — 273,888 — 273,888 U.S. government agency securities — 180,652 — 180,652 Total financial assets $ 107,888 $ 454,540 $ — $ 562,428 Financial Liabilities: Embedded derivatives liabilities $ — $ — $ 1,512 $ 1,512 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. government agency securities — 55,936 — 55,936 Total financial assets $ 6,254 $ 189,035 $ — $ 195,289 Financial Liabilities: Embedded derivatives liabilities $ — $ — $ 246 $ 246 Level 3 liabilities are comprised of embedded derivatives liabilities as described in Note 8. The following table sets forth a summary of the changes in the estimated fair value of the Company’s embedded derivatives liabilities, which were measured at fair value on a recurring basis (in thousands): Balance as of December 31, 2016 $ 246 Issuance of embedded derivatives 609 Net increase in fair value included in other income (expense) 657 Balance as of September 30, 2017 $ 1,512 We estimate the fair values of our corporate notes and commercial paper and U.S 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. There were no transfers between any of the levels of the fair value hierarchy during the periods presented.

Financial Instruments

Financial Instruments	9 Months Ended
	Sep. 30, 2017
Investments Debt And Equity Securities [Abstract]
Financial Instruments	4. Financial Instruments Cash equivalents and investments, all of which are classified as available-for-sale securities, consisted of the following (in thousands): September 30, 2017 December 31, 2016 Estimated Estimated Unrealized Unrealized Fair Unrealized Unrealized Fair Cost Gain (Loss) Value Cost Gain (Loss) Value Money market funds $ 107,888 $ — $ — $ 107,888 $ 6,254 $ — $ — $ 6,254 Corporate notes and commercial paper 273,897 1 (10 ) 273,888 133,112 1 (14 ) $ 133,099 U.S. government agency securities 180,681 5 (34 ) 180,652 55,934 5 (3 ) $ 55,936 $ 562,466 $ 6 $ (44 ) $ 562,428 $ 195,300 $ 6 $ (17 ) $ 195,289 Classified as: Cash equivalents $ 308,696 $ 64,998 Short-term investments 225,107 130,291 Long-term investments 28,625 — Total cash equivalents and investments $ 562,428 $ 195,289 At September 30, 2017 , the remaining contractual maturities of available-for-sale securities were less than two years

Collaboration and License Agree

Collaboration and License Agreements	9 Months Ended
	Sep. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Collaboration and License Agreements	5. Collaboration and License Agreements Summary of Collaboration-Related Revenue We have recognized revenue from our collaboration and license agreements as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 BMS and Pfizer $ 1,038 $ 1,798 $ 3,824 $ 4,785 Daiichi Sankyo 2,034 3,810 6,227 8,491 Bayer and Janssen 544 3,316 1,880 7,431 Bayer 212 398 812 1,052 Other — — — 52 Total collaboration and license revenue $ 3,828 $ 9,322 $ 12,743 $ 21,811 Bristol-Myers Squibb Company (“BMS”) and Pfizer Inc. (“Pfizer”) In 2014, we entered into an agreement with BMS and Pfizer to study andexanet alfa as a reversal agent to apixaban in our Phase 3 studies. As of September 30, 2017, we have no further milestone payments eligible for achievement under this agreement and continue to recognize the non-contingent payments received on a straight-line basis over the period of performance, which is estimated to be through the third quarter of 2018. In the second quarter of 2017, we updated our estimated period of performance from the first quarter of 2018 to the third quarter of 2018 to reflect a modification to our clinical development and regulatory plans. The effect of this change in estimate was not significant. During the three and nine months ended September 30, 2017 and 2016, we recognized $0.4 million and $1.4 million, and $0.6 million and $1.6 million in collaboration revenue under this agreement, respectively. The deferred revenue balance under this agreement as of September 30, 2017 was $9.8 million. In 2016, we entered into an agreement with BMS and Pfizer whereby they obtained exclusive rights to develop and commercialize andexanet alfa in Japan and we are responsible for certain research, development and manufacturing activities. As of September 30, 2017, we have milestone payments totaling up to $20.0 million that remain eligible for achievement upon certain regulatory events and up to $70.0 million which may be earned upon the achievement of specified annual net sales volumes in Japan in addition to royalties ranging from 5% to 15% on net sales of andexanet alfa in Japan. We continue to recognize non-contingent consideration received under the agreement on a straight-line basis over the period of performance, which is estimated to be 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. During the Daiichi Sankyo, Inc. (“Daiichi Sankyo”) In 2014, as amended in 2016, we entered into an agreement with Daiichi Sankyo to study andexanet alfa as a reversal agent to edoxaban. As of September 30, 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. We continue to recognize non-contingent consideration received under the agreement on a straight-line basis over the period of performance, which is estimated to be through the third quarter of 2018. The $8.0 million refundable portion of the upfront consideration is recorded as an obligation to collaborator and will be relieved as we make royalty payments or written off should we fail to commercialize andexanet alfa. During the three and nine months ended September 30, 2017 and 2016, we recognized $1.8 million and $5.4 million, and $3.4 million and $7.7 million in collaboration revenue under this agreement, respectively. The deferred revenue balance under this agreement as of September 30, 2017 was $7.2 million. In 2016 we entered into an agreement with Daiichi Sankyo associated with the pursuit of regulatory approval of andexanet alfa as a reversal agent to edoxaban in Japan. As of September 30, 2017, we have milestone payments totaling up to $10.0 million eligible for achievement upon initial and final regulatory approval of andexanet alfa as a reversal agent to edoxaban in Japan. We continue to recognize non-contingent consideration received under the agreement on a straight-line basis over the period of performance, which is estimated to be 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. During the three and nine months ended September 30, 2017 and 2016, we recognized $0.2 million and $0.9 million, and $0.4 million and $0.8 million in collaboration revenue under this agreement, respectively. The deferred revenue balance under this agreement as of September 30, 2017 was $2.9 million. Bayer Pharma, AG (“Bayer”) and Janssen Pharmaceuticals, Inc. (“Janssen”) In 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 September 30, 2017, we have milestone payments totaling up to $5.0 million that remain eligible for achievement upon the occurrence of certain events associated with scaling up our manufacturing process. We continue to recognize non-contingent consideration received under the agreement on a straight-line basis over the period of performance, which is estimated to be through the third quarter of 2018. In the second quarter of 2017 we updated our estimated period of performance from the first quarter of 2018 to the third quarter of 2018 to reflect a modification to our clinical development and regulatory plans. The effect of this change in estimate was not significant. During the three and nine months ended September 30, 2017 and 2016, we recognized $0.5 million and $1.9 million, and $3.3 million and $7.4 million in collaboration revenue, including milestone payments under this agreement, respectively. The deferred revenue balance under this agreement as of September 30, 2017 was $2.2 million. Bayer Pharma, AG (“Bayer”) In 2016, we entered into an agreement with Bayer associated with the pursuit of regulatory approval of andexanet alfa as a reversal agent to rivaroxaban in Japan. As of September 30, 2017, the $10.0 million milestone payment associated with regulatory approval of andexanet alfa as a reversal agent to rivaroxaban in Japan remains eligible for achievement. We continue to recognize non-contingent consideration received under the agreement on a straight-line basis over the period of performance, which is estimated to be 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. During the three and nine months ended September 30, 2017 and 2016, we recognized $0.2 million and $0.8 million, and $0.4 million and $1.1 million in collaboration revenue under this agreement, respectively. The deferred revenue balance under this agreement as of September 30, 2017 was $2.7 million.

Purchase Commitments

Purchase Commitments	9 Months Ended
	Sep. 30, 2017
Commitments And Contingencies Disclosure [Abstract]
Purchase Commitments	6. Purchase Commitments Commercial Supply Agreement In 2016, we entered into an Amended Restated Commercial Supply Agreement (“aCSA”) with CMC ICOS Biologics, Inc. (“CMC”), a subsidiary of AGC Asahi Glass, that amends and restates the terms of the original Commercial Supply Agreement. 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. We have made firm orders to manufacture 20 batches in 2017 and are required to make a non-refundable manufacturing reservation payment of $2.5 million for ten batches to be manufactured in 2018 contingent upon CMC’s successful delivery of services related to our BLA re-submission to the FDA. Pursuant to the terms of the aCSA, we received a $33.7 million credit, 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 through December 31, 2017. For the three and nine months ended September 30, 2017, the Company utilized $2.0 million and $7.3 million of these credits as a reduction of R&D expense to settle accounts payable and accrued liabilities related to specified services rendered by CMC. 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 September 30, 2017, we have not provided financial or other support to CMC that was not previously contractually required. We have recorded $0.5 million of accounts payable and $0.5 million of prepaid manufacturing services in our condensed consolidated balance sheet as of September 30, 2017. Our agreement with CMC does not require us to fund operations at CMC and therefore, we quantify our maximum exposure to loss as the aggregate value of prepaid manufacturing services as of September 30, 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 2016 we entered into a Manufacturing Agreement, as amended, with Hovione, Limited, (“Hovione”), pursuant to which Hovione will manufacture active pharmaceutical ingredient for betrixaban at commercial scale and perform process validation during the term of the agreement. As of September 30, 2017, we have recorded $2.7 million in prepaid expenses and other current assets and $9.6 million in prepaid and other long-term under the agreement, and will make up to $12.9 million of additional cancellable and non-cancellable payments throughout the term of the Agreement, ending June 2018.

Asset Acquisition and License A

Asset Acquisition and License Agreements	9 Months Ended
	Sep. 30, 2017
Research And Development [Abstract]
Asset Acquisition and License Agreements	7. Asset Acquisition and License Agreements SRX Cardio, LLC In 2016, we entered into an exclusive license agreement with SRX Cardio, LLC (“SRX Cardio”) to explore a novel approach to develop a drug in the field of hypercholesterolemia. We determined that SRX Cardio is, and as of September 30, 2017, continues to be, a variable interest entity that requires consolidation. Accordingly, we have consolidated the financial statements of SRX Cardio since inception of the agreement on December 1, 2015 by (a) eliminating all intercompany balances and transactions; and (b) allocating loss (income) attributable to the noncontrolling interest in SRX Cardio to net loss attributable to noncontrolling interest in our consolidated statement of operations and reflecting noncontrolling interest on our consolidated balance sheet. Our interest in SRX Cardio is limited to the development of the intellectual property asset. As of September 30, 2017, we have not provided financial or other support to SRX Cardio that was not previously contracted or required. We recorded SRX Cardio’s $0.2 million of cash as restricted cash 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. Millennium Pharmaceuticals, Inc. (“Millennium”) In August 2004, we entered into an agreement to license from Millennium certain exclusive rights to research, develop and commercialize certain compounds that inhibit Factor Xa, 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, during such time a tiered single-digit royalty rate will apply to net product sales. 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 new drug application, or 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 venous thromboembolism, triggering a $2.0 million milestone payment to Millennium which is recorded as a research and development expense in our 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 condensed consolidated balance sheet and will be amortized on a straight-line basis over the remaining estimated useful life. Amortization expenses were $0.2 million and $0.2 million for the three and nine months ended September 30, 2017. These amortization expenses were recorded as cost of sales. Should betrixaban receive regulatory approval in Europe, another $5.0 million will become payable for such approval event. An additional $23.0 million in milestone payments would become due if betrixaban was approved in the United States and Europe for other indications specified in the agreement.

Long-term Debt

Long-term Debt	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Long-term Debt	8. Long-term Debt Note Payable In December 2016, we entered into a supplemental funding support agreement with BMS and Pfizer whereby we received $50.0 million in exchange for two promissory notes totaling $65.0 million that become due in December 2024. The use of funds is restricted to development activities needed for regulatory approval of andexanet alfa by the FDA and European Medicines Agency (“EMA”) as provided for in the agreement. Pursuant to the terms of the agreement, we are required to pay down the note each quarter in an amount equal to 5% of net sales of andexanet alfa in the United States and European Union (“EU”). Should the initial regulatory approval of andexanet alfa in the USA 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 our company; 2) an event of default; and 3) termination 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. The carrying values of the notes payable at September 30, 2017 and December 31, 2016, including accrued interest of $2.6 million and $0.1 million, are $52.5 million and $49.8 million, respectively. We evaluated the features of the notes payable and determined that certain features which 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 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, as further described in Note 3 to the condensed consolidated financial statements. The aggregate fair value of the embedded derivatives at issuance date was $0.3 million included in other long-term liabilities. We will remeasure the embedded derivatives to fair value each reporting period until the repayment, termination or maturity of the long-term note payable. For the three and nine months ended September 30, 2017, we recognized a gain of $22,000 and $79,000, respectively, upon remeasurement of the embedded derivatives. The estimated fair value of the note payable at September 30, 2017 was $58.5 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 (the “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 the Company has 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 s 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 payments based upon the timing of initial regulatory approval 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 condensed consolidated financial statements. The Company 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 three and nine months ended September 30, 2017, we recognized a loss of $12,000 and $0.7 million upon remeasurement of the embedded derivatives. The effective interest rate as of September 30, 2017 was 18.5%. For the three and nine months ended September 30, 2017, accrued interest in the amount of $2.2 million and $5.6 million were 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 September 30, 2017 and are being amortized over the estimated term of the debt using the effective interest method. For the three and nine months ended September 30, 2017, we recognized interest expense, including amortization of the debt discount, related to the debt of $2.2 million and $5.6 million, respectively. 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 September 30, 2017 was $52.4 million, inclusive of accrued interest expense of $5.6 million and net of unamortized debt discount of $2.4 million. The estimated fair value of long-term debt at September 30, 2017 was $52.1 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.

Stock Based Compensation

Stock Based Compensation	9 Months Ended
	Sep. 30, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Based Compensation	9. Stock Based Compensation In January 2013, our Board of Directors adopted our 2013 Equity Incentive Plan (the “2013 Plan”), which became effective upon the closing of our initial public offering in May 2013. On January 1, 2017, the number of shares available for issuance under the 2013 Plan automatically increased by a number of shares equal to 5% of the total common stock outstanding at December 31, 2016. In September 2017, our Board of Directors adopted an Inducement Plan with 1,500,000 shares available for issuance to new employees entering into employment with Portola in accordance with NASDAQ Listing Rule 5635(c)(4) (the “2017 Plan”). As of September 30, 2017, there were 15,032,633 shares reserved under the 2013 Plan and 1,500,000 shares reserved under the 2017 Plan for the future issuance of equity awards. Stock Options The following table summarizes stock option activity under our 2013 Plan and 2017 Plan and related information during the nine months ended September 30, 2017: Shares Subject Weighted- Outstanding Average Exercise Options Price Per Share Balance at December 31, 2016 5,817,116 $ 25.26 Options granted 1,813,300 38.68 Options exercised (1,008,791 ) 15.37 Options canceled (200,522 ) 35.48 Balance at September 30, 2017 6,421,103 $ 30.28 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. As of September 30, 2017, 90,378 shares subject to outstanding PSOs were unvested and there was $0.3 million of unrecognized compensation costs relates to these PSOs. Management currently estimates the vesting of these PSOs to be probable of vesting and will be recognized over a weighted-average period of 0.41 years. The following table summarizes PSO activity under our 2013 Plan and related information during the nine months ended September 30, 2016: Shares Subject Weighted- Outstanding Average Exercise Options Price Per Share Balance at December 31, 2016 180,752 $ 23.76 Options granted — — Options exercised (4,635 ) — Options canceled — — Balance at September 30, 2017 176,117 $ 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 following table summarizes RSU activity, under our 2013 Plan and related information: Shares Subject to Weighted- Outstanding Average grant date RSUs fair value per share Balance at December 31, 2016 546,507 $ 28.38 RSUs granted 338,800 26.80 RSUs released (211,882 ) 28.26 RSUs canceled (35,653 ) 27.25 Balance at September 30, 2017 637,772 $ 27.65 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 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. related to andexanet alfa. The following table summarizes PSU activity, under our 2013 Plan and related information: Shares Subject to Weighted- Outstanding Average grant date PSUs fair value per share Balance at December 31, 2016 285,866 $ 29.24 PSUs granted 143,750 25.54 PSUs released (60,374 ) 35.97 PSUs canceled (52,281 ) 33.76 Balance at September 30, 2017 316,961 $ 25.53 The table below sets forth the functional classification of stock-based compensation expense, for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Research and development $ 4,155 $ 3,465 $ 14,974 $ 9,561 Selling, general and administrative 5,960 4,307 17,431 12,903 Total stock-based compensation $ 10,115 $ 7,772 $ 32,405 $ 22,464

Net Loss per Share Attributable

Net Loss per Share Attributable to Portola Common Stockholders	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Net Loss per Share Attributable to Portola Common Stockholders	10. Net Loss per Share Attributable to Portola Common Stockholders Basic net loss per share attributable to Portola Common Stockholders has been computed by dividing the net loss attributable to Portola Common Stockholders by the weighted-average number of shares of Common Stock outstanding during the period. Diluted net loss per share attributable to Portola Common Stockholders is calculated by dividing net loss attributable to Portola Common Stockholders by the weighted average number of shares of Common Stock and potential dilutive securities outstanding during the period. The following common stock equivalent shares were excluded from the computation of diluted net loss per share attributable to Portola Common Stockholders for the three and nine months ended September 30, 2017 and 2016 because including them would have been anti-dilutive: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Stock options to purchase common stock 6,421,103 5,888,149 6,421,103 5,888,149 Performance stock options 176,117 271,122 176,117 271,122 Common stock warrants 1,500 1,500 1,500 1,500 Restricted stock units 637,772 559,077 637,772 559,077 Performance stock units 316,961 286,052 316,961 286,052 Employee stock purchase plan 7,759 10,019 7,759 10,019 Up to 1 million shares may be contingently issued, if certain performance conditions are met under an agreement with one of our contract manufacturers.

Summary of Significant Accoun17

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Consolidation and Basis of Presentation	Consolidation and Basis of Presentation The accompanying unaudited condensed consolidated financial statements include the amounts of Portola and its wholly-owned subsidiaries and a development partner that is a variable interest entity (a “VIE”) for which Portola is deemed, under applicable accounting guidance, to be the primary beneficiary as of September 30, 2017. The unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”), and follow the requirements of the Securities and Exchange Commission (“SEC”) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These condensed consolidated financial statements have been prepared on the same basis as our annual consolidated financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments that are necessary for a fair statement of our financial information. The results of operations for the three and nine months ended September 30, 2017 are not necessarily indicative of the results to be expected for the year ending December 31, 2017 or for any other interim period or for any other future year. The condensed consolidated balance sheet as of December 31, 2016 has been derived from the audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete financial statements. The accompanying unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2016 included in our Annual Report on Form 10-K filed on March 1, 2017 with the SEC.
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, 2016.
Use of Estimates	Use of Estimates The preparation of condensed 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 condensed 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 including short-term and long-term classification, embedded derivative liabilities, interest expense, income taxes, in-process research and development, the consolidation of VIEs and deconsolidation of VIEs and stock-based compensation. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results may differ from those estimates.
Variable Interest Entities	Variable Interest Entities We review agreements we enter into with third party entities, pursuant to which we may have a variable interest in that 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 operations and financial position of the VIE into our consolidated financial statements. Our determination as to 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 In-process research and development asset relates to our consolidated VIE and 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 product revenues 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. Intangible assets with finite useful lives are amortized over their estimated useful lives, on a straight-line basis, and are reviewed for impairment when facts or circumstances suggest that the carrying value of these assets may not be recoverable. See Note 7, “Asset Acquisition and License Agreements,” to these condensed consolidated financial statements for further information.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents consist of cash and other highly liquid investments with original maturities of three months or less from the date of purchase.
Investments in Marketable Securities	Investments in Marketable Securities All investments in marketable securities have been classified as “available-for-sale” and are carried at estimated fair value as determined based upon quoted market prices or pricing models for similar securities. Management determines the appropriate classification of our investments in debt securities at the time of purchase and reevaluates such designation as of each balance sheet date. Unrealized gains and losses are excluded from earnings and were reported as a component of accumulated comprehensive income (loss). Realized gains and losses and declines in fair value judged to be other than temporary, if any, on available-for-sale securities are included in interest and other income, net. The cost of securities sold is based on the specific-identification method. Interest on marketable securities is included in interest and other income, net.
Collaboration Customer Concentration	Collaboration Collaboration customers who accounted for 10% or more of total collaboration and license revenues were as follows: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Daiichi Sankyo, Inc. 53 % 41 % 49 % 39 % Bayer Pharma, AG and Janssen Pharmaceuticals, Inc. 14 % 36 % 15 % 34 % Bristol-Myers Squibb Company and Pfizer Inc. 27 % 19 % 30 % 22 %
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 condensed 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.
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 classification of our debt and note payable liabilities.
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 the same as basic net loss per share attributable to Portola Common Stockholders, since the effects of potentially dilutive securities are antidilutive.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2017, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“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 March 2016, the FASB issued ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers Revenue from Contracts with Customers Principal versus Agent Considerations Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients 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. Although we are still evaluating our contracts and assessing all the potential impacts of the standard, we anticipate the adoption may have a material impact on our condensed consolidated financial statements. Specifically, the timing of recognition for certain contingent payments from our collaborators may be impacted by the adoption of the new revenue standard. ASU No. 2014-09 differs from the current accounting standard in many respects, such as in the 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. In February 2016, the Financial Accounting Standards Board (FASB) issued ASU No. 2016-02, Leases (Topic 842), which amends the existing accounting standards for leases. The new standard requires lessees to record a right-of-use asset and a corresponding lease liability on the balance sheet (with the exception of short-term leases). For lessees, leases will continue to be classified as either operating or financing in the income statement. This ASU becomes effective for the Company in the first quarter of fiscal year 2019 and early adoption is permitted. This ASU is required to be applied with a modified retrospective approach and requires application of the new standard at the beginning of the earliest comparative period presented. The Company is currently evaluating the impact that ASU 2016-02 will have on its financial statements.

Summary of Significant Accoun18

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 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: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Daiichi Sankyo, Inc. 53 % 41 % 49 % 39 % Bayer Pharma, AG and Janssen Pharmaceuticals, Inc. 14 % 36 % 15 % 34 % Bristol-Myers Squibb Company and Pfizer Inc. 27 % 19 % 30 % 22 %

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 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, allocated into Level 1, Level 2 and Level 3, that were measured on a recurring basis (in thousands): September 30, 2017 Level 1 Level 2 Level 3 Total Financial Assets: Money market funds $ 107,888 $ — $ — $ 107,888 Corporate notes and commercial paper — 273,888 — 273,888 U.S. government agency securities — 180,652 — 180,652 Total financial assets $ 107,888 $ 454,540 $ — $ 562,428 Financial Liabilities: Embedded derivatives liabilities $ — $ — $ 1,512 $ 1,512 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. government agency securities — 55,936 — 55,936 Total financial assets $ 6,254 $ 189,035 $ — $ 195,289 Financial Liabilities: Embedded derivatives liabilities $ — $ — $ 246 $ 246
Summary of Changes in Estimated Fair Value of Embedded Derivatives Liabilities Measured on Recurring Basis	The following table sets forth a summary of the changes in the estimated fair value of the Company’s embedded derivatives liabilities, which were measured at fair value on a recurring basis (in thousands): Balance as of December 31, 2016 $ 246 Issuance of embedded derivatives 609 Net increase in fair value included in other income (expense) 657 Balance as of September 30, 2017 $ 1,512

Financial Instruments (Tables)

Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2017
Investments Debt And Equity Securities [Abstract]
Cash Equivalents and Investments Classified as Available-for-sale Securities	Cash equivalents and investments, all of which are classified as available-for-sale securities, consisted of the following (in thousands): September 30, 2017 December 31, 2016 Estimated Estimated Unrealized Unrealized Fair Unrealized Unrealized Fair Cost Gain (Loss) Value Cost Gain (Loss) Value Money market funds $ 107,888 $ — $ — $ 107,888 $ 6,254 $ — $ — $ 6,254 Corporate notes and commercial paper 273,897 1 (10 ) 273,888 133,112 1 (14 ) $ 133,099 U.S. government agency securities 180,681 5 (34 ) 180,652 55,934 5 (3 ) $ 55,936 $ 562,466 $ 6 $ (44 ) $ 562,428 $ 195,300 $ 6 $ (17 ) $ 195,289 Classified as: Cash equivalents $ 308,696 $ 64,998 Short-term investments 225,107 130,291 Long-term investments 28,625 — Total cash equivalents and investments $ 562,428 $ 195,289

Collaboration and License Agr21

Collaboration and License Agreements (Tables)	9 Months Ended
	Sep. 30, 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): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 BMS and Pfizer $ 1,038 $ 1,798 $ 3,824 $ 4,785 Daiichi Sankyo 2,034 3,810 6,227 8,491 Bayer and Janssen 544 3,316 1,880 7,431 Bayer 212 398 812 1,052 Other — — — 52 Total collaboration and license revenue $ 3,828 $ 9,322 $ 12,743 $ 21,811

Stock Based Compensation (Table

Stock Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Activity	The following table summarizes stock option activity under our 2013 Plan and 2017 Plan and related information during the nine months ended September 30, 2017: Shares Subject Weighted- Outstanding Average Exercise Options Price Per Share Balance at December 31, 2016 5,817,116 $ 25.26 Options granted 1,813,300 38.68 Options exercised (1,008,791 ) 15.37 Options canceled (200,522 ) 35.48 Balance at September 30, 2017 6,421,103 $ 30.28
Summary of PSO Activity	The following table summarizes PSO activity under our 2013 Plan and related information during the nine months ended September 30, 2016: Shares Subject Weighted- Outstanding Average Exercise Options Price Per Share Balance at December 31, 2016 180,752 $ 23.76 Options granted — — Options exercised (4,635 ) — Options canceled — — Balance at September 30, 2017 176,117 $ 23.76
Summary of RSU Activity	The following table summarizes RSU activity, under our 2013 Plan and related information: Shares Subject to Weighted- Outstanding Average grant date RSUs fair value per share Balance at December 31, 2016 546,507 $ 28.38 RSUs granted 338,800 26.80 RSUs released (211,882 ) 28.26 RSUs canceled (35,653 ) 27.25 Balance at September 30, 2017 637,772 $ 27.65
Summary of PSU Activity	The following table summarizes PSU activity, under our 2013 Plan and related information: Shares Subject to Weighted- Outstanding Average grant date PSUs fair value per share Balance at December 31, 2016 285,866 $ 29.24 PSUs granted 143,750 25.54 PSUs released (60,374 ) 35.97 PSUs canceled (52,281 ) 33.76 Balance at September 30, 2017 316,961 $ 25.53
Classification of Stock-Based Compensation Expense	The table below sets forth the functional classification of stock-based compensation expense, for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Research and development $ 4,155 $ 3,465 $ 14,974 $ 9,561 Selling, general and administrative 5,960 4,307 17,431 12,903 Total stock-based compensation $ 10,115 $ 7,772 $ 32,405 $ 22,464

Net Loss per Share Attributab23

Net Loss per Share Attributable to Portola Common Stockholders (Tables)	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Common Stock Equivalent Shares Excluded from Computation of Diluted Net Loss	The following common stock equivalent shares were excluded from the computation of diluted net loss per share attributable to Portola Common Stockholders for the three and nine months ended September 30, 2017 and 2016 because including them would have been anti-dilutive: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Stock options to purchase common stock 6,421,103 5,888,149 6,421,103 5,888,149 Performance stock options 176,117 271,122 176,117 271,122 Common stock warrants 1,500 1,500 1,500 1,500 Restricted stock units 637,772 559,077 637,772 559,077 Performance stock units 316,961 286,052 316,961 286,052 Employee stock purchase plan 7,759 10,019 7,759 10,019

Organization - Additional Infor

Organization - Additional Information (Detail) $ / shares in Units, $ in Millions	1 Months Ended	9 Months Ended
	Sep. 30, 2017USD ($)$ / sharesshares	Sep. 30, 2017USD ($)Segment$ / shares
Organization And Nature Of Business [Line Items]
Number of operating segment | Segment		1
Follow on offering price per share | $ / shares	$ 55	$ 55
Proceeds from offering and over-allotment option, gross	$ 380.6
Offering expenses	0.7	$ 0.7
Proceeds from offering and over-allotment option, net	$ 379.9
Follow-on Offering
Organization And Nature Of Business [Line Items]
Stock issued during the period | shares	7,302,500
Underwriting discounts and commissions, net	$ 21.1
Underwriters Overallotment Option
Organization And Nature Of Business [Line Items]
Stock issued during the period | shares	952,500

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	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Daiichi Sankyo, Inc ("Daiichi")
Concentration Risk [Line Items]
Concentration risk percentage	53.00%	41.00%	49.00%	39.00%
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")
Concentration Risk [Line Items]
Concentration risk percentage	14.00%	36.00%	15.00%	34.00%
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")
Concentration Risk [Line Items]
Concentration risk percentage	27.00%	19.00%	30.00%	22.00%

Summary of Significant Accoun26

Summary of Significant Accounting Policies - Additional Information (Detail) $ in Millions	Sep. 30, 2017USD ($)
ASU No. 2016-09
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect of differed tax assets	$ 14

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	Sep. 30, 2017	Dec. 31, 2016
Financial Assets:
Total financial assets	$ 562,428	$ 195,289
Money market funds
Financial Assets:
Total financial assets	107,888	6,254
Corporate notes and commercial paper
Financial Assets:
Total financial assets	273,888	133,099
U.S. government agency securities
Financial Assets:
Total financial assets	180,652	55,936
Embedded derivative liabilities
Financial Liabilities:
Total financial liabilities	1,512	246
Fair Value, Inputs, Level 1
Financial Assets:
Total financial assets	107,888	6,254
Fair Value, Inputs, Level 1 | Money market funds
Financial Assets:
Total financial assets	107,888	6,254
Fair Value, Inputs, Level 2
Financial Assets:
Total financial assets	454,540	189,035
Fair Value, Inputs, Level 2 | Corporate notes and commercial paper
Financial Assets:
Total financial assets	273,888	133,099
Fair Value, Inputs, Level 2 | U.S. government agency securities
Financial Assets:
Total financial assets	180,652	55,936
Fair Value, Inputs, Level 3 | Embedded derivative liabilities
Financial Liabilities:
Total financial liabilities	$ 1,512	$ 246

Summary of Changes in Estimated

Summary of Changes in Estimated Fair Value of Embedded Derivatives Liabilities Measured on Recurring Basis (Detail) - Embedded derivative liabilities $ in Thousands	9 Months Ended
	Sep. 30, 2017USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance as of December 31, 2016	$ 246
Issuance of embedded derivatives	609
Net increase in fair value included in other income (expense)	657
Balance as of September 30, 2017	$ 1,512

Fair Values Measurements - Addi

Fair Values Measurements - Additional Information (Detail) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 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

Cash Equivalents and Investment

Cash Equivalents and Investments Classified as Available-for-sale Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule Of Available For Sale Securities [Line Items]
Cost	$ 562,466	$ 195,300
Unrealized Gains	6	6
Unrealized (Losses)	(44)	(17)
Estimated Fair Value	562,428	195,289
Money market funds
Schedule Of Available For Sale Securities [Line Items]
Cost	107,888	6,254
Estimated Fair Value	107,888	6,254
Corporate notes and commercial paper
Schedule Of Available For Sale Securities [Line Items]
Cost	273,897	133,112
Unrealized Gains	1	1
Unrealized (Losses)	(10)	(14)
Estimated Fair Value	273,888	133,099
U.S. government agency securities
Schedule Of Available For Sale Securities [Line Items]
Cost	180,681	55,934
Unrealized Gains	5	5
Unrealized (Losses)	(34)	(3)
Estimated Fair Value	180,652	55,936
Cash equivalents
Schedule Of Available For Sale Securities [Line Items]
Estimated Fair Value	308,696	64,998
Short-term investments
Schedule Of Available For Sale Securities [Line Items]
Estimated Fair Value	225,107	$ 130,291
Long-term investments
Schedule Of Available For Sale Securities [Line Items]
Estimated Fair Value	$ 28,625

Financial Instruments - Additio

Financial Instruments - Additional Information (Detail)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Investments Debt And Equity Securities [Abstract]
Available-for-sale securities, contractual maturities	2 years	1 year

Summary of Revenue from Collabo

Summary of Revenue from Collaboration and License Agreements (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	$ 3,828	$ 9,322	$ 12,743	$ 21,811
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	1,038	1,798	3,824	4,785
Daiichi Sankyo, Inc ("Daiichi")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	2,034	3,810	6,227	8,491
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	544	3,316	1,880	7,431
Bayer Pharma AG
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	$ 212	$ 398	$ 812	1,052
Other
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue				$ 52

Collaboration and License Agr33

Collaboration and License Agreements - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	$ 3,828,000	$ 9,322,000	$ 12,743,000	$ 21,811,000
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	1,038,000	1,798,000	3,824,000	4,785,000
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | 2014 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments eligible for achievement	0
Collaboration and license revenue	400,000	600,000	1,400,000	1,600,000
Deferred revenue	9,800,000		9,800,000
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | 2016 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	600,000	1,200,000	2,400,000	3,200,000
Deferred revenue	8,200,000		8,200,000
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | 2016 Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment receivable upon the achievement of certain regulatory events	20,000,000
Payment receivable upon the achievement of annual net sales volumes	$ 70,000,000
Percentage of royalties entitle to receive under agreement	15.00%
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | 2016 Agreement | Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of royalties entitle to receive under agreement	5.00%
Daiichi Sankyo, Inc ("Daiichi")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	$ 2,034,000	3,810,000	6,227,000	8,491,000
Daiichi Sankyo, Inc ("Daiichi") | 2014 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	1,800,000	3,400,000	5,400,000	7,700,000
Deferred revenue	7,200,000		7,200,000
Milestone payments of regulatory clinical event and patient enrollment targets			12,500,000
Contingent and non-contingent consideration to be recognized after resolution of contingency			8,000,000
Daiichi Sankyo, Inc ("Daiichi") | 2016 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	200,000	400,000	900,000	800,000
Deferred revenue	2,900,000		2,900,000
Daiichi Sankyo, Inc ("Daiichi") | 2016 Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments eligible for achievement of initial and final regulatory approval	10,000,000
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	544,000	3,316,000	1,880,000	7,431,000
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen") | 2014 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	500,000	3,300,000	1,900,000	7,400,000
Deferred revenue	2,200,000		2,200,000
Milestone payments eligible for achievement of certain events	5,000,000
Bayer Pharma AG
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	212,000	398,000	812,000	1,052,000
Bayer Pharma AG | 2016 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	200,000	$ 400,000	800,000	$ 1,100,000
Deferred revenue	$ 2,700,000		2,700,000
Milestone payment associated with regulatory approval			$ 10,000,000

Purchase Commitments - Addition

Purchase Commitments - Additional Information (Detail)	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2017USD ($)	Sep. 30, 2017USD ($)	Dec. 31, 2016USD ($)Batch
Long Term Purchase Commitment [Line Items]
Accounts payables	$ 17,463,000	$ 17,463,000	$ 14,546,000
Prepaid expenses and other current assets	8,766,000	8,766,000	2,680,000
Prepaid and other long-term assets	9,609,000	$ 9,609,000	$ 5,214,000
CMC ICOS Biologics Inc
Long Term Purchase Commitment [Line Items]
Number of batches to be manufactured, 2017 | Batch			20
Non-refundable manufacturing reservation payments committed			$ 2,500,000
Purchase commitment, description		We have made firm orders to manufacture 20 batches in 2017 and are required to make a non-refundable manufacturing reservation payment of $2.5 million for ten batches to be manufactured in 2018 contingent upon CMC’s successful delivery of services related to our BLA re-submission to the FDA
Number of batches to be manufactured, 2018 | Batch			10
Purchase obligation services received		$ 33,700,000
Repayment of accounts payable and accrued liabilities	2,000,000	7,300,000
Accounts payables	500,000	500,000
Prepaid manufacturing services	500,000	500,000
Hovione, Limited
Long Term Purchase Commitment [Line Items]
Prepaid expenses and other current assets	2,700,000	2,700,000
Prepaid and other long-term assets	$ 9,600,000	9,600,000
Hovione, Limited | Maximum
Long Term Purchase Commitment [Line Items]
Cancellable and non-cancellable additional purchase commitments		$ 12,900,000

Asset Acquisition and License35

Asset Acquisition and License Agreements - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended			3 Months Ended		9 Months Ended
	Jun. 30, 2017	Dec. 31, 2016	Aug. 31, 2004	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Asset Acquisition [Line Items]
Restricted cash (SRX Cardio)		$ 178		$ 170		$ 170
Net income (loss) attributable to Non Controlling interest (SRX Cardio)				(5)	$ 1,853	190	$ 1,853
Milestone payment on regulatory approval						5,000
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
Additional milestone payable for other indications approved				23,000		23,000
Millennium | Europe
Asset Acquisition [Line Items]
Milestone payable for approval event				5,000		5,000
Additional milestone payable for other indications approved				23,000		23,000
Millennium | Research and Development Expense
Asset Acquisition [Line Items]
Milestone payment		$ 2,000
Millennium | Cost of Sales | United States
Asset Acquisition [Line Items]
Finite-lived intangible assets, amortization expenses				200		$ 200
SRX Cardio
Asset Acquisition [Line Items]
Variable interest entity, Terms of arrangements						Accordingly, we have consolidated the financial statements of SRX Cardio since inception of the agreement on December 1, 2015 by (a) eliminating all intercompany balances and transactions; and (b) allocating loss (income) attributable to the noncontrolling interest in SRX Cardio to net loss attributable to noncontrolling interest in our consolidated statement of operations and reflecting noncontrolling interest on our consolidated balance sheet.
Restricted cash (SRX Cardio)				$ 200		$ 200

Long-term Debt - Additional Inf

Long-term Debt - Additional Information (Detail)	1 Months Ended		3 Months Ended	9 Months Ended
	Feb. 28, 2017USD ($)	Dec. 31, 2016USD ($)PromissoryNote	Sep. 30, 2017USD ($)	Sep. 30, 2017USD ($)
Debt Instrument [Line Items]
Carrying value of notes payable		$ 49,815,000	$ 52,505,000	$ 52,505,000
Loss on remeasurement of embedded derivatives				657,000
Long-term debt			52,388,000	52,388,000
HealthCare Royalty Partners and its Affiliates (“HCR”) | Andexanet Alfa
Debt Instrument [Line Items]
Accrued interest expense			5,600,000	5,600,000
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			$ 12,000	$ 700,000
Effective interest rate			18.50%	18.50%
Debt instrument increase, accrued interest			$ 2,200,000	$ 5,600,000
Royalty sales agreement fee			2,000,000	2,000,000
Additional debt issuance costs				600,000
Interest expense, including amortization of debt discount			2,200,000	5,600,000
Long-term debt			52,400,000	52,400,000
Outstanding debt, net of unamortized debt discount			2,400,000	2,400,000
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			52,100,000	$ 52,100,000
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 USA 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) our change of control; 2) event of default; and 3) termination 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 European Union
Debt Instrument [Line Items]
Initial regulatory approval date		Jan. 1, 2019
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | United States and European Union | 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		$ 100,000	2,600,000	$ 2,600,000
Carrying value of notes payable		49,800,000	52,500,000	52,500,000
Embedded derivative liabilities		$ 300,000
Gain on remeasurement of embedded derivatives			22,000	79,000
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			$ 58,500,000	$ 58,500,000

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Jan. 31, 2017	Jan. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage increase in number of common stock outstanding		5.00%
Performance Stock Options (PSOs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares outstanding unvested	90,378
Unamortized share based compensation expected to be recognized over the remaining vesting period	$ 0.3
Unamortized share based compensation expected recognition period	4 months 28 days
Performance Stock Units (PSUs) | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares available for issuance			143,750	102,906
Inducement Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares available for issuance	1,500,000
2013 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved, shares	15,032,633
2017 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved, shares	1,500,000

Summary of Stock Option Activit

Summary of Stock Option Activity (Detail) - Employee Stock Option - 2013 and 2017 Equity Incentive Plan	9 Months Ended
	Sep. 30, 2017$ / sharesshares
Shares Subject to Outstanding Stock Options
Beginning balance | shares	5,817,116
Options granted | shares	1,813,300
Options exercised | shares	(1,008,791)
Options canceled | shares	(200,522)
Ending balance | shares	6,421,103
Weighted-Average Exercise Price Per Share
Beginning balance | $ / shares	$ 25.26
Options granted | $ / shares	38.68
Options exercised | $ / shares	15.37
Options canceled | $ / shares	35.48
Ending balance | $ / shares	$ 30.28

Summary of PSO Activity (Detail

Summary of PSO Activity (Detail) - Performance Stock Options (PSOs) - 2013 Equity Incentive Plan	9 Months Ended
	Sep. 30, 2017$ / sharesshares
Shares Subject to Outstanding Stock Options
Beginning balance	180,752
Options exercised	(4,635)
Ending balance	176,117
Weighted-Average Exercise Price Per Share
Beginning balance | $ / shares	$ 23.76
Ending balance | $ / shares	$ 23.76

Summary of RSU Activity (Detail

Summary of RSU Activity (Detail) - Restricted Stock Units (RSUs) - 2013 Equity Incentive Plan	9 Months Ended
	Sep. 30, 2017$ / sharesshares
Shares Subject to Outstanding Options
Beginning balance | shares	546,507
RSUs granted | shares	338,800
RSUs released | shares	(211,882)
RSUs canceled | shares	(35,653)
Ending balance | shares	637,772
Weighted-Average grant date fair value per share
Beginning balance | $ / shares	$ 28.38
RSUs granted | $ / shares	26.80
RSUs released | $ / shares	28.26
RSUs canceled | $ / shares	27.25
Ending balance | $ / shares	$ 27.65

Summary of PSU Activity (Detail

Summary of PSU Activity (Detail) - Performance Stock Units (PSUs) - 2013 Equity Incentive Plan	9 Months Ended
	Sep. 30, 2017$ / sharesshares
Shares Subject to Outstanding Options
Beginning balance | shares	285,866
RSUs granted | shares	143,750
RSUs released | shares	(60,374)
RSUs canceled | shares	(52,281)
Ending balance | shares	316,961
Weighted-Average grant date fair value per share
Beginning balance | $ / shares	$ 29.24
RSUs granted | $ / shares	25.54
RSUs released | $ / shares	35.97
RSUs canceled | $ / shares	33.76
Ending balance | $ / shares	$ 25.53

Classification of Stock-Based C

Classification of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 10,115	$ 7,772	$ 32,405	$ 22,464
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	4,155	3,465	14,974	9,561
Selling, General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 5,960	$ 4,307	$ 17,431	$ 12,903

Common Stock Equivalent Shares

Common Stock Equivalent Shares Excluded from Computation of Diluted Net Loss per Share (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
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	6,421,103	5,888,149	6,421,103	5,888,149
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	176,117	271,122	176,117	271,122
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	1,500
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	637,772	559,077	637,772	559,077
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	316,961	286,052	316,961	286,052
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	7,759	10,019	7,759	10,019

Net Loss per Share Attributab44

Net Loss per Share Attributable to Portola Common Stockholders - Additional Information (Detail)	9 Months Ended
	Sep. 30, 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