Related Party Transactions (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Related Party Transaction [Line Items]
Accounts payable and accrued expenses - related parties	$ 0		$ 0		$ 2,517
General and administrative expenses	11,325	$ 1,408	20,127	$ 2,989
Equity Method Investee | Holtec International
Related Party Transaction [Line Items]
Accounts payable and accrued expenses - related parties	0		0		2,382
General and administrative expenses	$ 22,516	$ 217	$ 30,368	$ 995
Corporate Joint Venture | Hi-Power
Related Party Transaction [Line Items]
Due from related parties, current					278
Affiliated Entity | Consultant Fees
Related Party Transaction [Line Items]
Accounts payable and accrued expenses - related parties					$ 138