Commitments and Contingencies (Details) (USD $)		0 Months Ended	1 Months Ended		0 Months Ended	1 Months Ended
	Sep. 30, 2013	Jul. 27, 2007 830 Winter Street, Waltham, MA item sqft	Apr. 30, 2012 830 Winter Street, Waltham, MA sqft	Dec. 31, 2009 830 Winter Street, Waltham, MA sqft	Mar. 31, 2013 Norwood, MA sqft	Aug. 31, 2013 100 River Ridge Drive, Norwood, MA sqft
Operating leases
Area of space leased (in square feet)		89,000	7,310		43,850	7,507
Initial lease term period		12 years	3 years			5 years 2 months
Number of additional terms for which lease agreement can be extended		2
Additional term period for which lease agreement can be extended		5 years			5 years	5 years
Area of property covered under sublease agreement (in square feet)				14,100
Additional period for which sublease agreement can be extended				2 years
Minimum rental commitments under the non-cancelable operating lease agreements
2014 (nine months remaining)	$ 5,012,000
2015	6,780,000
2016	6,549,000
2017	6,624,000
2018	6,831,000
Thereafter	10,029,000
Total minimum lease payments	41,825,000
Total minimum rental payments from subleases	(781,000)
Total minimum lease payments, net	41,044,000
Purchase Obligations
Obligation to make payment to vendor for certain contractual services	1,200,000
Collaborations
Potential milestone payments receivable	2,000,000
Amount reimbursable by a third party	$ 1,400,000