Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accrued Liabilities, Current [Abstract]
Accrued compensation and related liabilities	$ 28,470	$ 8,941
Accrued contract payables, current	88,347	15,706
Accrued cash settled stock-based compensation	10,021	3,282
Other accrued expenses	16,195	10,804
Total accrued expenses	$ 143,033	$ 38,733