Other Long-Term Liabilities (Details) $ in Thousands	1 Months Ended					3 Months Ended
	Mar. 31, 2017 USD ($)	Nov. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jan. 31, 2014 USD ($)	Jan. 31, 2013 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) ft²
Deferred Rent								$ 396	$ 398
Net Deferred Tax Liability related to IPR&D								28,054	28,054
Deferred Income from Sale of Tax Benefits								8,940	9,436
Accrued Lease Restructuring	$ 1,258					$ 1,154		1,258	1,154
Long-Term Severance								357	539
Contingent Milestones								47,600	44,200
Deferred Revenue								3,523	3,749
Total								90,128	87,530
Less Current Portion								(4,940)	(4,826)
Long-Term Portion								85,188	82,704
Amount at which New Jersey tax benefit agreed to be sold		$ 9,800	$ 1,900	$ 1,100	$ 800
Amount of sale of New Jersey tax benefit		$ 9,200	$ 1,800	$ 1,000	$ 800
Period for which base of operations must be maintained						5 years
Other income related to sale of tax benefits						$ 500	$ 600
Accrued lease restructuring
Beginning Balance						1,154
Ending Balance	1,258					1,258
Needham Expansion
Accrued Lease Restructuring	1,258					1,154		$ 1,258	$ 1,154
Expansion space (in square feet) | ft²									11,500
Accrued lease restructuring
Beginning Balance						1,154
Expense						184
Payments						(80)
Ending Balance	1,258					$ 1,258
General and administrative | Branford, CT lease termination
Restructuring expense	$ 200