Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Accrued Liabilities.
Accrued compensation expenses	$ 3,326	$ 2,673
Accrued Genzyme co-promotion fees	1,845	3,309
Accrued other	2,194	1,869
Total accrued liabilities	$ 7,365	$ 7,851