Revenue Accounted for 10% or More of Total Collaboration and License Revenues (Detail) - Customer Concentration Risk - Sales Revenue, Net	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Daiichi Sankyo, Inc ("Daiichi")
Concentration Risk [Line Items]
Concentration risk percentage	40.00%	63.00%	45.00%	43.00%
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")
Concentration Risk [Line Items]
Concentration risk percentage	45.00%	28.00%	38.00%	39.00%
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")
Concentration Risk [Line Items]
Concentration risk percentage	13.00%	7.00%	15.00%	15.00%