Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Accrued Liabilities
Employee bonuses	$ 1,041	$ 938
Accrued clinical trial costs	1,908	1,507
Accrued professional fees and other	403	208
Total accrued liabilities	$ 3,352	$ 2,653