Collaboration and License Agreements - Additional Information (Detail) - USD ($)	1 Months Ended						3 Months Ended				9 Months Ended		24 Months Ended
	Mar. 31, 2016	Feb. 29, 2016	Jul. 31, 2014	Jan. 31, 2014	Jun. 30, 2013	Feb. 28, 2013	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014	Jun. 30, 2014	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue							$ 9,322,000	$ 2,912,000			$ 21,811,000	$ 7,656,000
Research and development							87,209,000	48,405,000			190,822,000	140,563,000
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee				$ 13,000,000
Milestone Payments of Development and Regulatory Event				$ 12,000,000
Percentage of consideration received under agreement				50.00%
Non-contingent consideration being recognized as revenue over estimated period of performance											6,500,000
Contingent consideration to be recognized after resolution of contingency											6,500,000
Milestone payments of regulatory and clinical event							0				3,500,000
Contingent payment receivable upon achievement											3,000,000
Collaboration and license revenue							1,798,000	388,000			4,785,000	1,152,000
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | January 2014 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue							603,000	388,000			1,600,000	1,200,000
Deferred revenue							11,800,000				11,800,000
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | February 2016 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue							1,200,000				3,200,000
Deferred revenue							11,800,000				$ 11,800,000
Non-refundable upfront fee		$ 15,000,000
Contingent payment receivable upon achievement of regulatory events		20,000,000
Contingent payment receivable upon achievement of annual net sales volumes		70,000,000
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | February 2016 Agreement | Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of royalties entitle to receive under agreement											5.00%
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | February 2016 Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of royalties entitle to receive under agreement											15.00%
Daiichi Sankyo, Inc ("Daiichi")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee			$ 15,000,000
Milestone Payments of Development and Regulatory Event			20,000,000
Contingent consideration to be recognized after resolution of contingency													$ 3,000,000
Contingent payment receivable upon achievement			$ 5,000,000
Collaboration and license revenue							3,810,000	1,154,000			$ 8,491,000	3,424,000
Deferred revenue							0				0
Collaborative arrangement upfront payment to be received					$ 6,000,000
Upfront fee subject to refund					$ 3,000,000
Non-contingent consideration being recognized as collaboration revenue over estimated period of performance										$ 3,000,000
Contingent and non-contingent consideration to be recognized after resolution of contingency								264,000				782,000
Daiichi Sankyo, Inc ("Daiichi") | Collaborative Agreement to Study Safety and Efficacy of Andexanet Alfa
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue							3,400,000	890,000			7,700,000	2,600,000
Deferred revenue							7,100,000				7,100,000
Daiichi Sankyo, Inc ("Daiichi") | Collaborative Agreement to Study Safety and Efficacy of Andexanet Alfa | Future Contingent Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue							2,500,000				5,000,000
Daiichi Sankyo, Inc ("Daiichi") | March 2016 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue							410,000				840,000
Deferred revenue							4,200,000				4,200,000
Daiichi Sankyo, Inc ("Daiichi") | March 2016 Agreement | Future Contingent Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue											0
Daiichi Sankyo, Inc ("Daiichi") | March 2016 Agreement | ESS-Study
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reimbursement of costs and expenses percentage	33.00%
Daiichi Sankyo, Inc ("Daiichi") | March 2016 Agreement | Minimum | Edoxaban
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reimbursement of costs and expenses percentage	33.00%
Daiichi Sankyo, Inc ("Daiichi") | March 2016 Agreement | Maximum | Edoxaban
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reimbursement of costs and expenses percentage	100.00%
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee	$ 5,000,000			$ 10,000,000		$ 5,000,000
Milestone Payments of Development and Regulatory Event				8,000,000
Contingent payment receivable upon achievement	10,000,000			$ 7,000,000
Collaboration and license revenue							3,316,000	1,316,000			7,431,000	2,922,000
Reduced contingent payment receivable upon achievement	$ 7,000,000
Additional non-refundable fee						500,000
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen") | January 2014 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue							3,300,000	816,000			7,400,000	$ 2,400,000
Deferred revenue							4,900,000				4,900,000
Contingent Payments Received									$ 3,000,000
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen") | January 2014 Agreement | Future Contingent Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue							2,500,000				5,000,000
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen") | February 2013 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative Arrangement Payment Received								$ 500,000
Bayer Pharma AG
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee		5,000,000				2,500,000
Contingent payment receivable upon achievement		10,000,000
Collaboration and license revenue							398,000				1,052,000
Reduced contingent payment receivable upon achievement		$ 7,000,000
Additional non-refundable fee						250,000
Bayer Pharma AG | February 2016 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue							398,000				1,100,000
Deferred revenue							3,900,000				3,900,000
Bayer Pharma AG | February 2016 Agreement | Future Contingent Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue											$ 0
Bayer Pharma AG | February 2016 Agreement | ESS-Study
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reimbursement of costs and expenses percentage		33.00%
Bayer Pharma AG | February 2016 Agreement | Minimum | Rivaroxaban
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reimbursement of costs and expenses percentage		33.00%
Bayer Pharma AG | February 2016 Agreement | Maximum | Rivaroxaban
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reimbursement of costs and expenses percentage		100.00%
Janssen Pharmaceuticals, Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee						2,500,000
Additional non-refundable fee						$ 250,000
Ora, Inc. (“Ora”)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development costs, percent											60.00%
Percentage of profits entitle to receive under agreement											50.00%
Notice period for agreement termination											90 days
Rights to buy compound interests and licensed agreements											Each party may also buy out the rights and interests in the licensed compound by paying the greater of $6.0 million or two times the actual aggregate development cost incurred by both parties before or 90 days after an End of Phase 2 meeting with the FDA.
Research and development							$ 28,000				$ 467,000
Ora, Inc. (“Ora”) | PORTOLA PHARMACEUTICALS INC
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development costs, percent											40.00%