Leases, Licensed Technology and Other Commitments - Additional Information (Detail) ft² in Thousands, $ in Thousands	1 Months Ended					3 Months Ended		6 Months Ended
	Jul. 31, 2016 USD ($)	Aug. 31, 2015 ft²	Mar. 31, 2015 renewal_option	Sep. 30, 2013 ft²	May 31, 2012 ft²	Jun. 30, 2016 USD ($) ft² renewal_option	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) ft² renewal_option	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)	Jan. 31, 2013 ft² building
Operating Leased Assets [Line Items]
Future minimum annual rental payments under operating lease due, remainder of year						$ 7,700		$ 7,700
Future minimum annual rental payments under operating lease due, year two						31,500		31,500
Future minimum annual rental payments under operating lease due, year three						37,100		37,100
Future minimum annual rental payments under operating lease due, year four						35,100		35,100
Property and equipment, gross						345,422		345,422		$ 296,666
Future minimum annual rental payments under operating lease due, year five						32,100		32,100
Future minimum annual rental payments under operating lease due, thereafter						325,300		325,300
Aggregate base salaries payable to officers, due in remainder of year						4,400		4,400
Aggregate base salaries payable to officers, due in year two						4,800		4,800
Aggregate base salaries payable to officers, due year three						4,800		4,800
Aggregate base salaries payable to officers, due year four						$ 4,800		$ 4,800
Lease Agreements
Operating Leased Assets [Line Items]
Area of office and laboratory (in square feet) | ft²						100		100
Extended lease expiration date						2019-07
Number of consecutive renewal options | renewal_option						2		2
Operating lease renewal options, lease term in years								5 years
Operating lease, letters of credit outstanding						$ 1,400		$ 1,400
Operating lease term					3 years
Additional area of office space (in square feet) | ft²					26
Future minimum annual rental payments under operating lease due, remainder of year						3,300		3,300
Future minimum annual rental payments under operating lease due, year two						6,000		6,000
Future minimum annual rental payments under operating lease due, year three						6,100		6,100
Future minimum annual rental payments under operating lease due, year four						3,600		3,600
Operating lease rent expense						2,200	$ 2,600	4,500	$ 4,500
Contingent rent expense						176,000	$ 327,000	369,000	$ 539,000
Binney Street, Cambridge, Massachusetts | Lease Agreements
Operating Leased Assets [Line Items]
Operating lease renewal options, lease term in years			5 years
Operating lease, letters of credit outstanding						9,200		9,200
Operating lease term			15 years
Additional area of office space (in square feet) | ft²				142
Future minimum annual rental payments under operating lease due, remainder of year						4,400		4,400
Future minimum annual rental payments under operating lease due, year two						25,500		25,500
Future minimum annual rental payments under operating lease due, year three						31,000		31,000
Future minimum annual rental payments under operating lease due, year four						$ 31,500		31,500
Area of laboratory and office space under lease agreement (in square feet) | ft²				386							244
Number of units with all of the rentable space leased | building											1
Number of units available for operating lease | building											2
Occupancy year						2015
Facility lease obligation						$ 275,800		275,800
Number of renewal options | renewal_option			3
Future minimum annual rental payments under operating lease due, year five						32,100		32,100
Future minimum annual rental payments under operating lease due, year six						32,700		32,700
Future minimum annual rental payments under operating lease due, thereafter						$ 292,600		292,600
Estimated year in which contract wil be complete						In the second half of 2016
Binney Street, Cambridge, Massachusetts | Sublease Agreement
Operating Leased Assets [Line Items]
Operating lease term		10 years
Future minimum annual rental payments under operating lease due, remainder of year						$ 5,300		5,300
Future minimum annual rental payments under operating lease due, year two						10,700		10,700
Future minimum annual rental payments under operating lease due, year three						10,900		10,900
Future minimum annual rental payments under operating lease due, year four						11,100		11,100
Area of laboratory and office space under lease agreement (in square feet) | ft²		160
Future minimum annual rental payments under operating lease due, year five						11,300		11,300
Future minimum annual rental payments under operating lease due, thereafter						$ 65,500		65,500
Estimated year in which contract wil be complete						In the third quarter of 2016
Lausanne, Switzerland | Lease Agreements
Operating Leased Assets [Line Items]
Future minimum annual rental payments under operating lease due, year three						$ 1,100		1,100
Future minimum annual rental payments under operating lease due, year four						1,100		1,100
Future minimum annual rental payments under operating lease due, year five						1,100		1,100
Subsequent event | Lease Agreements
Operating Leased Assets [Line Items]
Payments for early lease termination	$ 1,700
Construction in progress
Operating Leased Assets [Line Items]
Property and equipment, gross						$ 292,683		$ 292,683		$ 246,669