Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Accrued clinical trial costs	$ 10,735	$ 13,285
Accrued compensation	11,995	11,223
Accrued professional fees	10,090	3,936
Accrued royalties	12,957	0
Other accrued expenses	13,041	5,861
Accrued expenses and other current liabilities	$ 58,818	$ 34,305