Revenue Accounted for 10% or More of Total Collaboration and License Revenues (Detail) - Customer Concentration Risk - Sales Revenue, Net	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Daiichi Sankyo, Inc ("Daiichi")
Concentration Risk [Line Items]
Concentration risk percentage	53.00%	31.00%	47.00%	37.00%
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")
Concentration Risk [Line Items]
Concentration risk percentage	14.00%	19.00%	15.00%	33.00%
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")
Concentration Risk [Line Items]
Concentration risk percentage	27.00%	41.00%	31.00%	24.00%