Other Long-Term Liabilities (Details) $ in Thousands	1 Months Ended				6 Months Ended
	Nov. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jan. 31, 2014 USD ($)	Jan. 31, 2013 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($) ft²
Deferred Rent							$ 710	$ 398
Net Deferred Tax Liabilities related to IPR&D							28,054	28,054
Deferred Income from Sale of Tax Benefits							8,940	9,436
Accrued Lease Restructuring					$ 1,154		1,150	1,154
Long-Term Severance							181	539
Contingent Milestones							48,600	44,200
Deferred Revenue							3,729	3,749
Total							91,364	87,530
Less Current Portion							(5,538)	(4,826)
Long-Term Portion							85,826	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					1,150
Needham Expansion
Accrued Lease Restructuring					1,154		$ 1,150	$ 1,154
Expansion space (in square feet) | ft²								11,500
Accrued Lease Restructuring
Beginning Balance					1,154
Expense					267
Payments					(271)
Ending Balance					1,150
General and administrative | Branford, CT lease termination
Restructuring expense					$ 200