Collaboration and License Agreements - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	$ 5,128,000	$ 8,258,000
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	1,758,000	1,254,000
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	600,000	500,000
Deferred revenue	10,600,000
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | 2016 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	1,200,000	800,000
Deferred revenue	9,500,000
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	$ 2,181,000	3,385,000
Daiichi Sankyo, Inc ("Daiichi") | 2014 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	1,800,000	3,400,000
Deferred revenue	10,800,000
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	400,000
Deferred revenue	3,300,000
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	799,000	3,307,000
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen") | 2014 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	800,000	3,300,000
Deferred revenue	3,200,000
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	390,000	260,000
Bayer Pharma AG | 2016 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue	400,000	$ 300,000
Deferred revenue	3,200,000
Milestone payment associated with regulatory approval	$ 10,000,000