Other Financial Information - Schedule of Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Other Financial Information [Abstract]
Accounts payable	$ 1,700	$ 4,272
Accrued clinical expenses	839	673
Accrued research and development costs	1,396	780
Accrued general and administrative expenses	1,298	1,029
Accrued other expense	709	1,786
Total accounts payable and accrued expenses	$ 5,942	$ 8,540