Commitments - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended			9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 04, 2013	Sep. 30, 2013 Cambridge [Member] Option	Nov. 29, 2011 Cambridge [Member] sqft	Sep. 30, 2013 Standby Letter 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						561,000
Leasehold improvements						311,852
Total rent expense	241,000	218,000	838,000	433,000
Settlement agreement					$ 286,000