Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Accrued Expenses and Other Current Liabilities
Research costs - Nordic	$ 2,898	$ 11,536
Research costs - other	5,178	3,336
Payroll and employee benefits	3,330	1,659
Professional fees	3,546	1,304
Accrued interest on notes payable		234
Other		198
Total accrued expenses and other current liabilities	$ 14,952	$ 18,267