Major Customers, Partnerships and Strategic Alliances - Agreement with Sigma-Aldrich Corporation - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended		12 Months Ended
	Oct. 31, 2009	Jul. 31, 2007	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Common stock issued under license agreement				$ 93,796	$ 69,492
Research and development			$ 67,198	56,974	37,039
Sigma-Aldrich Corporation [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research program to develop laboratory research reagents		3 years
Upfront license fee	$ 20,000
Public offering, common stock shares issued	636,133
Reduced royalty rate	10.50%
Funding available under the amended agreement	$ 25,000
Sigma-Aldrich Corporation [Member] | Upfront license fee [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Upfront license fee	15,100
Common stock issued under license agreement	4,900
Sigma-Aldrich Corporation [Member] | License agreement terms [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Royalty revenues expected to be received	$ 5,000
Research and development			$ 400	$ 100	$ 200