Collaboration and License Agreements - Additional Information (Detail) - USD ($)	1 Months Ended						3 Months Ended		6 Months Ended
	Jul. 31, 2014	Apr. 30, 2014	Jan. 31, 2014	Feb. 28, 2013	Jan. 31, 2013	Nov. 30, 2012	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2013
Research And Development Arrangement Contract To Perform For Others [Line Items]
Collaboration and license revenue							$ 2,385,000	$ 2,415,000	$ 4,744,000	$ 4,786,000
Research and development							52,300,000	28,983,000	92,158,000	57,138,000
Biogen Idec
Research And Development Arrangement Contract To Perform For Others [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							0	86,000	0	164,000
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")
Research And Development Arrangement Contract To Perform For Others [Line Items]
Upfront fee			$ 13,000,000
Milestone Payments of Development and Regulatory Event			$ 12,000,000
Percentage of consideration received under agreement			50.00%
Non-contingent consideration being recognized as revenue over estimated period of performance									6,500,000
Contingent consideration to be recognized after resolution of contingency									6,500,000
Collaboration and license revenue							384,000	503,000	763,000	945,000
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | January 2014 Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Collaboration and license revenue							384,000	503,000	763,000	945,000
Deferred revenue							10,700,000		10,700,000
Lee’s Pharmaceutical (HK) Ltd (“Lee’s”)
Research And Development Arrangement Contract To Perform For Others [Line Items]
Upfront fee					$ 700,000
Collaboration and license revenue							52,000	63,000	104,000	125,000
Deferred revenue							158,000		$ 158,000
Notice period for agreement termination					60 days
Aciex Therapeutics, Inc. (“Aciex”)
Research And Development Arrangement Contract To Perform For Others [Line Items]
Development costs, percent									60.00%
Percentage of profits entitle to receive under agreement									50.00%
Research and development							0	0	$ 0	0
Aciex Therapeutics, Inc. (“Aciex”) | PORTOLA PHARMACEUTICALS INC
Research And Development Arrangement Contract To Perform For Others [Line Items]
Development costs, percent									40.00%
Bayer Pharma AG
Research And Development Arrangement Contract To Perform For Others [Line Items]
Upfront fee				$ 2,500,000
Additional non-refundable fee				250,000
Janssen Pharmaceuticals, Inc.
Research And Development Arrangement Contract To Perform For Others [Line Items]
Upfront fee				2,500,000
Additional non-refundable fee				250,000
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")
Research And Development Arrangement Contract To Perform For Others [Line Items]
Upfront fee			$ 10,000,000	5,000,000
Milestone Payments of Development and Regulatory Event			8,000,000
Collaboration and license revenue							807,000	1,194,000	$ 1,606,000	2,106,000
Additional non-refundable fee				$ 500,000
Contingent payment receivable upon achievement			$ 7,000,000
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen") | January 2014 Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Collaboration and license revenue							807,000	788,000	1,606,000	1,300,000
Deferred revenue							8,900,000		8,900,000
Contingent Payments Received									3,000,000
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen") | January 2014 Agreement | Future Contingent Payments
Research And Development Arrangement Contract To Perform For Others [Line Items]
Collaboration and license revenue									0
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen") | February 2013 Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Collaboration and license revenue								406,000		807,000
Deferred revenue							0		0
Daiichi Sankyo, Inc ("Daiichi")
Research And Development Arrangement Contract To Perform For Others [Line Items]
Upfront fee	$ 15,000,000
Milestone Payments of Development and Regulatory Event	20,000,000
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
Collaboration and license revenue							1,142,000	655,000	2,271,000	1,610,000
Contingent payment receivable upon achievement	$ 5,000,000
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
Research And Development Arrangement Contract To Perform For Others [Line Items]
Collaboration and license revenue							881,000		1,752,000
Deferred revenue							11,500,000		11,500,000
Daiichi Sankyo, Inc ("Daiichi") | Future Contingent Payments | Collaborative Agreement to Study Safety and Efficacy of Andexanet Alfa
Research And Development Arrangement Contract To Perform For Others [Line Items]
Collaboration and license revenue									0
Daiichi Sankyo, Inc ("Daiichi")
Research And Development Arrangement Contract To Perform For Others [Line Items]
Contingent consideration to be recognized after resolution of contingency							261,000	$ 519,000	655,000	$ 1,600,000
Deferred revenue							527,000		$ 527,000
Ora, Inc. (“Ora”)
Research And Development Arrangement Contract To Perform For Others [Line Items]
Notice period for agreement termination									90 days
Development costs, percent									60.00%
Percentage of profits entitle to receive under agreement									50.00%
Research and development							$ 0		$ 0
Rights to buy compound interests and licensed agreements									Each party may 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 on or before End of Phase 2 opt out point.
Ora, Inc. (“Ora”) | PORTOLA PHARMACEUTICALS INC
Research And Development Arrangement Contract To Perform For Others [Line Items]
Development costs, percent									40.00%