Restructuring - Additional Information (Detail) $ in Thousands				12 Months Ended
	May. 22, 2015 USD ($)	Oct. 17, 2013 ft²	Aug. 30, 2013 ft²	Dec. 31, 2015 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2014 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring charges					$ 1,700
Loss on disposition of business					(800)
Loss on disposal of fixed assets					(600)
Loss on disposal of fixed assets					(585)
Expected sublease revenue from subtenant for next year				$ 962
Boston, MA
Restructuring Cost and Reserve [Line Items]
Area under sublease agreement | ft²			5,249
Loss on sublease					42
Remaining contractual obligation					367
Sublease revenue from subtenant	$ 105				325
Loss on disposal of fixed assets					(194)
Security deposits	$ 17			$ 127	20			$ 127
Date of sublease vacated for lease				2014-10
Operating lease expiration month and year	2016-08						2016-08
Expected sublease revenue from subtenant for next year				$ 44
New York, NY
Restructuring Cost and Reserve [Line Items]
Area under sublease agreement | ft²		7,259
Loss on sublease					729
Remaining contractual obligation					2,300
Sublease revenue from subtenant					1,600
Loss on disposal of fixed assets					(392)
Operating lease expiration month and year						2018-10
General and Administrative Expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges					600
Research and Development Expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges					$ 1,100