Restructuring - Additional Information (Detail) (USD $)	12 Months Ended			124 Months Ended	12 Months Ended	124 Months Ended	1 Months Ended	12 Months Ended	1 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2012 Severance and Health Benefit Continuation Costs	Dec. 31, 2013 Severance and Health Benefit Continuation Costs	Oct. 17, 2013 NEW YORK sqft	Dec. 31, 2013 NEW YORK	Aug. 30, 2013 Boston MA Office sqft	Dec. 31, 2013 Boston MA Office	Dec. 31, 2013 General and Administrative Expense	Dec. 31, 2013 Research and Development Expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 1,700,000				$ 1,300,000	$ 1,300,000					$ 600,000	$ 1,100,000
Loss on disposition of business	800,000
Loss on disposal of fixed assets	600,000
Area given for sublease							7,259		5,249
Loss on sublease								729,000		42,000
Remaining contractual obligation								2,300,000		367,000
Expected sublease revenue from subtenant								1,600,000		325,000
Loss on disposal of fixed assets	(585,000)	(48,000)	0	(641,000)				(392,000)		(194,000)
Security deposit									$ 20,000	$ 127,000