Commitments and Contingencies - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) Lease	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) Lease	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($) ft²	Dec. 31, 2013 USD ($)
150 Second Street [Member]
Long-term Purchase Commitment [Line Items]
Number of facility leases | Lease	2		2
Security deposit of lease agreement	$ 864,000		$ 864,000			$ 1,725,000
Rent expense associated with the lease	634,000	$ 1,069,000	$ 1,901,000	$ 2,806,000
150 Second Street [Member] | Second Amendment [Member]
Long-term Purchase Commitment [Line Items]
Tenant improvements					$ 1,020,500
Additional space for lease | ft²					8,164
Lease commencement date			2014-11
150 Second Street [Member] | Lease One [Member]
Long-term Purchase Commitment [Line Items]
Lease expected term			1 year
Lease expiration date			2013-10
150 Second Street [Member] | Lease Two [Member]
Long-term Purchase Commitment [Line Items]
Lease expected term			8 years
Lease rent waiver period			10 months 15 days
Value of rent obligations			$ 3,300,000
Tenant improvements	9,239,000		$ 9,239,000
One Kendall Square [Member]
Long-term Purchase Commitment [Line Items]
Lease expected term			7 years 6 months
Rent abatement	1,841,000		$ 1,841,000
Ten Canal Park Lease [Member]
Long-term Purchase Commitment [Line Items]
Security deposit of lease agreement	1,037,000		1,037,000
Rent expense associated with the lease	377,000		$ 876,000
Lease expiration date			Aug. 31, 2020
Lease rent per month			$ 172,850
Landlord for tenant improvements to the premises			1,995,550
Security deposit on submission of evidence to landlord for capital contribution	$ 530,550		$ 530,550