Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Accrued clinical trial costs	$ 11,224	$ 13,285
Accrued compensation	9,549	11,223
Accrued professional fees	4,706	3,936
Lease liabilities, current	3,456	2,825
Other accrued expenses	4,068	5,861
Total	$ 33,003	$ 37,130