Revenue from Collaborators (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total net revenues from collaborators	$ 8,275	$ 18,642
Cubist
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total net revenues from collaborators		9,721
Takeda
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total net revenues from collaborators	5,493	5,493
Monsanto
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total net revenues from collaborators	1,410	1,410
MDCO
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total net revenues from collaborators	1,266	834
Other
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total net revenues from collaborators	$ 106	$ 1,184