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