Collaboration and License Agreements with Merck & Co., Inc. - Additional Information (Detail) (USD $)	12 Months Ended			1 Months Ended	4 Months Ended	35 Months Ended	8 Months Ended	32 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Jul. 31, 2007 Collaborative Arrangement	May 04, 2010 Collaborative Arrangement	May 04, 2010 Collaborative Arrangement	Dec. 31, 2010 License Agreement Terms	Dec. 31, 2012 License Agreement Terms	Dec. 31, 2012 License Agreement Terms Sarcoma	Dec. 31, 2012 License Agreement Terms Other Cancer
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of global development costs funded by each party in collaboration						50.00%
Proceeds from collaborators				$ 75,000,000	$ 12,800,000	$ 53,500,000
Percentage of costs funded in the license agreement								100.00%
Percentage of co-promotion by the company, maximum								20.00%
Proceeds from license fees							50,000,000
Potential milestone payments associated with the achievement of certain regulatory and sales objectives								514,000,000
Proceeds from regulatory or sales milestone payments									25,000,000
Potential additional milestone payments associated with potential regulatory approvals										289,000,000
Potential additional milestone payments associated with the achievement of certain sales thresholds								200,000,000
Recognition of deferred revenue			111,500,000
Service revenue	$ 44,000.0	$ 111,000.0	$ 4,500,000