Major Customers, Partnerships and Strategic Alliances - Agreement with Dow AgroSciences in Plant Agriculture - Additional Information (Detail) - Dow Agro Sciences [Member] - License agreement terms [Member] - USD ($)	1 Months Ended	12 Months Ended
	Oct. 31, 2005	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research program to develop laboratory research reagents	3 years
One-time license fee earned on exercise of option	$ 6,000,000
Royalty revenues	$ 2,300,000
Percentage of royalties to be received from sublicensing	25.00%
Previously agreed research, development and commercialization milestone payments, and royalties on sales of products	$ 4,000,000
Fee due	$ 25,300,000
Minimum license annual fees specific reckoning period	11 years
Collaboration agreement related costs and expenses		$ 0	$ 0	$ 400,000
Revenue attributable to research and development		$ 3,000,000	$ 3,000,000	$ 3,000,000
Minimum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Annual fees	$ 250,000
Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Annual fees	$ 3,000,000