License and Collaboration Agreements - Schedule of Revenue Recognized and Assets and Liabilities under Collaborative Arrangements (Detail) (License and Collaboration Agreements [Member], Sanofi [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
License and Collaboration Agreements [Member] | Sanofi [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment	$ 1,250	$ 1,250
Milestone payment	521	521
Development services	10,700	11,590
Manufacturing services and other	563	741
Total	13,034	14,102
Accounts receivable, billed	4,283		2,357
Accounts receivable, unbilled	7,513		3,417
Deferred revenues	$ 71,058		$ 73,392