Selected Balance Sheet Information (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Other Current Assets [Line Items]
Prepaid clinical research organizations expense	$ 2,224	$ 1,677
Prepaid travel and conference expenses	397	295
Prepaid manufacturing expenses	330	0
Prepaid insurances	240	358
Other current assets	175	185
Total	$ 3,366	$ 2,515