Commitments - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Cambridge [Member] Option	Nov. 29, 2012 Cambridge [Member] sqft	Jun. 30, 2013 Standby Letters of Credit [Member]
Operating Leased Assets [Line Items]
Lease Space for Laboratory and office space						26,150
Term of commercial lease					6 years 3 months
Lease extension option					5 years
Number of extension option					1
Standby letter of credit							$ 311,000
Deferred rent liability					325,000
Leasehold improvements					311,852
Total rent expense	$ 298,000	$ 114,000	$ 597,000	$ 215,000