Prepaid Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Prepaid Expenses
Prepaid clinical trial expense	$ 2,803	$ 1,678
Prepaid insurance	780	762
Other	107	42
Total prepaid expenses	3,690	2,482
Prepaid expenses, short-term and long-term
Prepaid expenses, short-term	3,690	804
Prepaid expenses, long-term		1,678
Total prepaid expenses	$ 3,690	$ 2,482