Major Customers, Partnerships and Strategic Alliances - Agreement with Sigma-Aldrich Corporation - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended		1 Months Ended			3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Oct. 31, 2009 Sigma-Aldrich Corporation [Member]	Jul. 31, 2007 Sigma-Aldrich Corporation [Member]	Oct. 31, 2009 Sigma-Aldrich Corporation [Member] Upfront license fee [Member]	Sep. 30, 2014 Sigma-Aldrich Corporation [Member] License agreement terms [Member]	Sep. 30, 2013 Sigma-Aldrich Corporation [Member] License agreement terms [Member]	Sep. 30, 2014 Sigma-Aldrich Corporation [Member] License agreement terms [Member]	Sep. 30, 2013 Sigma-Aldrich Corporation [Member] License agreement terms [Member]	Oct. 31, 2009 Sigma-Aldrich Corporation [Member] License agreement terms [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research program to develop laboratory research reagents						3 years
Upfront license fee					$ 20,000,000		$ 15,100,000
Common stock, valued					4,900,000
Public offering, common stock shares issued					636,133
Royalty revenues expected to be received												5,000,000
Reduced royalty rate					10.50%
Funding available under the amended agreement					25,000,000
Collaboration agreement related costs and expenses	$ 16,290,000	$ 8,703,000	$ 41,753,000	$ 26,201,000				$ 0	$ 100,000	$ 100,000	$ 100,000