Commitments and Contingencies - Additional Information (Details) $ in Thousands		1 Months Ended	6 Months Ended		12 Months Ended
		Dec. 31, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2012 USD ($)
Operating Leased Assets [Line Items]
Restricted cash		$ 169,763	$ 196,572
Restricted cash, current	[1]	52,470	60,584
Restricted cash, non-current	[1]	117,293	135,988
Grants receivable						$ 16,500
Deferred government grant obligation, current			1,000
Delaware grant obligation		9,212	9,431
PPA Entities
Operating Leased Assets [Line Items]
Restricted cash, current		4,698	1,296
Restricted cash, non-current		15,320	15,208
PPA Company 2 | PPA Entities
Operating Leased Assets [Line Items]
Restricted cash			107,400
Restricted cash, current		20,300	34,600
Restricted cash, non-current		88,400	72,800
PPA Company 3b | PPA Entities
Operating Leased Assets [Line Items]
Restricted cash					$ 20,000
Restricted cash, current		700	1,200
Restricted cash, non-current		$ 13,300	13,300
Pledged assets, term					7 years
Pledged assets, milestone percentage		0.33
Restricted cash released		$ 6,600
PPA Company 5
Operating Leased Assets [Line Items]
PPA expenses			$ 100	$ 5,700

[1] We have variable interest entities, which represent a portion of the consolidated balances recorded within these financial statement line items in the condensed consolidated balance sheets (see Note 11 - Portfolio Financings).