Leases, Licensed Technology and Other Commitments - Additional Information (Detail) (USD $)	12 Months Ended										1 Months Ended		12 Months Ended		1 Months Ended	12 Months Ended				1 Months Ended	12 Months Ended
	Dec. 31, 2013 Employee	Dec. 31, 2013 Licensed Technology	Dec. 31, 2012 Licensed Technology	Dec. 31, 2011 Licensed Technology	Dec. 31, 2013 Licensed Technology Year 2014	Dec. 31, 2013 Licensed Technology Year 2015	Dec. 31, 2013 Licensed Technology Year 2016	Dec. 31, 2013 Licensed Technology Year 2017	Dec. 31, 2013 Licensed Technology Year 2018	Dec. 31, 2013 Licensed Technology Year 2019	Sep. 30, 2013 Lease Agreements Binney Street, Cambridge, Massachusetts sqft	Jan. 31, 2013 Lease Agreements Binney Street, Cambridge, Massachusetts sqft	Dec. 31, 2013 Lease Agreements Binney Street, Cambridge, Massachusetts RenewalOptions	Oct. 31, 2013 Lease Agreements Binney Street, Cambridge, Massachusetts	Jan. 31, 2013 Lease Agreements Lausanne Switzerland sqft	Dec. 31, 2013 Lease Agreements Lausanne Switzerland	Dec. 31, 2012 Lease Agreements Lausanne Switzerland	Dec. 31, 2011 Lease Agreements Lausanne Switzerland	Jun. 30, 2013 Lease Agreements Lausanne Switzerland	May 31, 2012 Lease Agreements Landsdowne and Sidney Streets, Cambridge Massachusetts sqft	Dec. 31, 2013 Lease Agreements Landsdowne and Sidney Streets, Cambridge Massachusetts RenewalOptions sqft
Lease Commitments And Contingencies [Line Items]
Area of office and laboratory in square foot																					100,000
Extended lease expiration date																					2019-07
Number of consecutive renewal options																					2
Operating lease renewal options, lease term in years																					5 years
Operating lease, letters of credit outstanding												$ 5,800,000		$ 9,200,000							$ 1,400,000
Operating lease term													15 years		10 years					3 years
Additional square feet of office space											142,000									26,000
Future minimum annual rental payments under operating lease due, year one													5,300,000			7,800,000			1,100,000		6,700,000
Future minimum annual rental payments under operating lease due, year two													8,400,000			12,600,000			1,100,000		6,200,000
Future minimum annual rental payments under operating lease due, year three													26,600,000			15,000,000			1,100,000		5,500,000
Future minimum annual rental payments under operating lease due, year four													30,400,000			33,300,000			1,100,000		5,600,000
Future minimum annual rental payments under operating lease due, year five													30,900,000			37,200,000			1,200,000		5,700,000
Future minimum annual rental payments under operating lease due, thereafter													347,100,000			387,300,000			5,900,000		3,300,000
Area of laboratory and office space under lease agreement											386,000	244,000			22,000
Year in which leased facility will be available for occupancy												2015			2014
Number of renewal options													3
Number of lease years after optional extension													5 years
Number of lease years before optional extension and early termination can be exercised															5 years
Operating lease rent expense																6,100,000	5,900,000	2,000,000
License fees paid		145,000	145,000	145,000
Future expected annual license fees					235,000	235,000	55,000	50,000	50,000	35,000
Number of officers under employment agreements	20
Aggregate base salaries payable to officers, due next year	$ 6,700,000