Selected Balance Sheet Information (Details 2) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accrued Expenses [Line Items]
Accrued clinical consulting services	$ 621	$ 658
Accrued vendor payments	376	193
Accrued manufacturing costs	55	661
Other accrued expenses	6	14
Total	$ 1,058	$ 1,526