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	12 Months Ended	44 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jul. 31, 2007 Collaborative Arrangement	May 04, 2010 Collaborative Arrangement	May 04, 2010 Collaborative Arrangement	Dec. 31, 2010 License Agreement Terms	Dec. 31, 2013 License Agreement Terms	Dec. 31, 2013 License Agreement Terms Sarcoma
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%
Proceeds from license fees							50,000,000
Proceeds from regulatory or sales milestone payments									25,000,000
Service revenue	$ 27,000	$ 44,000	$ 111,000