Restructuring - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended	9 Months Ended		121 Months Ended	1 Months Ended	3 Months Ended	9 Months Ended		121 Months Ended	1 Months Ended
	Apr. 03, 2013 Position	Jun. 30, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Aug. 30, 2013 Boston Office sqft	Sep. 30, 2013 Boston Office	Sep. 30, 2013 Boston Office	Sep. 30, 2012 Severance and Health Benefit Continuation Costs	Sep. 30, 2013 Severance and Health Benefit Continuation Costs	Apr. 03, 2013 Filled positions Position	Apr. 03, 2013 Unfilled positions Position
Restructuring Cost and Reserve [Line Items]
Total charges incurred related to workforce reduction		$ 1,700,000
Number of positions eliminated	65										40	25
Restructuring charges relating to severance and other									1,300,000	1,300,000
Area given for sublease						5,249
Loss on sublease							42,000	42,000
Remaining contractual obligation							367,000	367,000
Expected sublease revenue from subtenant							325,000	325,000
Loss on disposal of fixed assets			$ (194,000)	$ (48,000)	$ (251,000)		$ (194,000)	$ (194,000)