Accrued and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Accrued Liabilities And Other Liabilities [Abstract]
Accrued compensation	$ 1,468	$ 1,270
Accrued contracted research and development costs	1,958	1,749
Accrued professional and consulting fees	553	480
Accrued other and other current liabilities	233	227
Total accrued and other current liabilities	$ 4,212	$ 3,726