Leases, Licensed Technology and Other Commitments - Additional Information (Detail) ft² in Thousands, $ in Thousands	1 Months Ended					3 Months Ended
	Aug. 31, 2015 ft²	Mar. 31, 2015 renewal_option	Sep. 30, 2013 ft²	Jan. 31, 2013 ft² building	May. 31, 2012 ft²	Mar. 31, 2016 USD ($) ft² renewal_option	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)
Operating Lease Obligations [Line Items]
Future minimum annual rental payments under operating lease due, remainder of year						$ 12,900
Future minimum annual rental payments under operating lease due, year two						32,700
Future minimum annual rental payments under operating lease due, year three						38,200
Future minimum annual rental payments under operating lease due, year four						36,200
Property and equipment, gross						319,556		$ 296,666
Future minimum annual rental payments under operating lease due, year five						33,200
Future minimum annual rental payments under operating lease due, thereafter						328,600
Aggregate base salaries payable to officers, due in remainder of year						6,900
Aggregate base salaries payable to officers, due in year two						5,000
Aggregate base salaries payable to officers, due year three						5,000
Aggregate base salaries payable to officers, due year four						5,000
Construction in progress
Operating Lease Obligations [Line Items]
Property and equipment, gross						$ 267,113		$ 246,669
Lease Agreements
Operating Lease Obligations [Line Items]
Extended lease expiration date						2019-07
Area of office and laboratory (in square feet) | ft²						100
Number of consecutive renewal options | renewal_option						2
Operating lease renewal options, lease term in years						5 years
Operating lease, letters of credit outstanding						$ 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						5,200
Future minimum annual rental payments under operating lease due, year two						6,000
Future minimum annual rental payments under operating lease due, year three						6,100
Future minimum annual rental payments under operating lease due, year four						3,600
Operating lease rent expense						2,300	$ 1,900
Contingent rent expense						194	$ 199
Lease Agreements | Binney Street, Cambridge, Massachusetts
Operating Lease Obligations [Line Items]
Operating lease renewal options, lease term in years		5 years
Operating lease, letters of credit outstanding						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						6,500
Future minimum annual rental payments under operating lease due, year two						25,500
Future minimum annual rental payments under operating lease due, year three						31,000
Future minimum annual rental payments under operating lease due, year four						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
Facility lease obligation						248,600
Number of renewal options | renewal_option		3
Future minimum annual rental payments under operating lease due, year five						32,100
Future minimum annual rental payments under operating lease due, year six						32,700
Future minimum annual rental payments under operating lease due, thereafter						$ 292,600
Estimated year in which contract wil be complete						In the second half of 2016
Occupancy year				2015
Lease Agreements | Lausanne, Switzerland
Operating Lease Obligations [Line Items]
Operating lease term				10 years
Future minimum annual rental payments under operating lease due, remainder of year						$ 500
Future minimum annual rental payments under operating lease due, year two						1,100
Future minimum annual rental payments under operating lease due, year three						1,100
Future minimum annual rental payments under operating lease due, year four						1,100
Area of laboratory and office space under lease agreement (in square feet) | ft²				22
Future minimum annual rental payments under operating lease due, year five						1,100
Future minimum annual rental payments under operating lease due, thereafter						3,300
Occupancy year				2014
Number of lease years before optional extension and early termination can be exercised				5 years
Sublease Agreement | Binney Street, Cambridge, Massachusetts
Operating Lease Obligations [Line Items]
Operating lease term	10 years
Future minimum annual rental payments under operating lease due, remainder of year						5,300
Future minimum annual rental payments under operating lease due, year two						10,700
Future minimum annual rental payments under operating lease due, year three						10,900
Future minimum annual rental payments under operating lease due, year four						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
Future minimum annual rental payments under operating lease due, thereafter						$ 65,500
Estimated year in which contract wil be complete						In the third quarter of 2016