Leases - Additional Information (Detail) $ in Millions		1 Months Ended			3 Months Ended
	Sep. 26, 2003 ft² RenewalOption	May 31, 2015 ft² RenewalOption	Apr. 30, 2015 ft² RenewalOption	Mar. 31, 2015	Mar. 31, 2019 USD ($)
Operating Leased Assets [Line Items]
Net cash paid included in operating activities in cash flow | $					$ 7.1
Operating lease, weighted-average remaining lease term					13 years 10 months 24 days
Operating lease, weighted-average discount rate					8.20%
BMR-675 West Kendall Lease
Operating Leased Assets [Line Items]
Area of office and laboratory space held under lease | ft²			295,000
Lease term			15 years
Number of lease extension options | RenewalOption			2
Lease renewal options period			5 years
Lessee, operating lease, option to extend					with options to renew for two terms of five years each.
Lessee, operating lease, existence of option to terminate [true false]					true
Third Street Lease
Operating Leased Assets [Line Items]
Area of office and laboratory space held under lease | ft²	129,000
Number of lease extension options | RenewalOption	2
Lease renewal options period	5 years
Lessee, operating lease, option to extend					with an option to extend for two additional five-year terms
Lessee, operating lease, existence of option to terminate [true false]					true
Lease extended expiration date	Jan. 31, 2034
101 Main Street Lease
Operating Leased Assets [Line Items]
Area of office and laboratory space held under lease | ft²		72,000
Number of lease extension options | RenewalOption		1
Lessee, operating lease, option to extend					each with an option to renew for one five-year term.
Lessee, operating lease, existence of option to terminate [true false]					true
Lease extended expiration date		Jun. 30, 2021		Mar. 31, 2024
Operating lease renewal options period		5 years