Collaborations, Contracts and Licensing Agreements - Deferred Collaborations and Contracts Revenue (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Nov. 16, 2014	May. 10, 2010
Deferred Revenue Arrangement [Line Items]
Deferred revenue current portion	$ 868	$ 5,779
Deferred revenue long-term portion	213	9,937
Total deferred revenue	1,081	15,716
DoD
Deferred Revenue Arrangement [Line Items]
Deferred revenue current portion	15	313
Monsanto
Deferred Revenue Arrangement [Line Items]
Deferred revenue current portion	0	4,245
Deferred revenue long-term portion	0	8,666
BMS
Deferred Revenue Arrangement [Line Items]
Total deferred revenue				$ 3,000
Dicerna
Deferred Revenue Arrangement [Line Items]
Deferred revenue current portion	853	1,221
Deferred revenue long-term portion	$ 213	$ 1,271
Total deferred revenue			$ 2,500