Outstanding Loans and Security Agreements - Schedule of Debt (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020	Aug. 31, 2020	May 01, 2020
Debt Instrument [Line Items]
Long-term debt, gross	$ 516,037,000	$ 527,054,000
Non-recourse debt	13,816,000	120,846,000
Non-recourse debt, non-current	490,380,000	270,053,000
Long-term Debt, Total	504,196,000	390,899,000
Unused borrowing capacity	759,000	968,000
10.25% Senior Secured Notes due March 2027
Debt Instrument [Line Items]
Interest rate percentage				10.25%
Letters of Credit | Letter of Credit due December 2021, Non-Recourse
Debt Instrument [Line Items]
Long-term debt, gross		0
Non-recourse debt		0
Non-recourse debt, non-current		0
Long-term Debt, Total		0
Unused borrowing capacity	$ 759,000	$ 968,000
Interest rate percentage	2.25%	2.25%
Notes | 10.25% Senior Secured Notes due March 2027
Debt Instrument [Line Items]
Long-term debt, gross	$ 70,000,000	$ 70,000,000
Non-recourse debt	6,034,000	0
Non-recourse debt, non-current	62,845,000	68,614,000
Long-term Debt, Total	$ 68,879,000	$ 68,614,000
Interest rate percentage	10.25%	10.25%
Senior secured notes | 2.5% Green Convertible Senior Notes due August 2025
Debt Instrument [Line Items]
Long-term debt, gross	$ 230,000,000	$ 230,000,000	$ 230,000,000
Non-recourse debt	0	0
Non-recourse debt, non-current	222,371,000	99,394,000
Long-term Debt, Total	$ 222,371,000	$ 99,394,000
Interest rate percentage	2.50%	2.50%	2.50%
Senior secured notes | Senior Secured Notes due March 2030, Non-Recourse
Debt Instrument [Line Items]
Long-term debt, gross	$ 75,016,000	$ 77,837,000
Non-recourse debt	4,467,000	3,882,000
Non-recourse debt, non-current	69,822,000	73,125,000
Long-term Debt, Total	$ 74,289,000	$ 77,007,000
Interest rate percentage	6.07%	6.07%
Recourse debt
Debt Instrument [Line Items]
Long-term debt, gross	$ 300,000,000	$ 300,000,000
Non-recourse debt	6,034,000	0
Non-recourse debt, non-current	285,216,000	168,008,000
Long-term Debt, Total	291,250,000	168,008,000
Term loan | Term Loan due September 2028, Non-Recourse
Debt Instrument [Line Items]
Long-term debt, gross	31,912,000	34,456,000
Non-recourse debt	3,315,000	2,826,000
Non-recourse debt, non-current	26,384,000	28,920,000
Long-term Debt, Total	$ 29,699,000	$ 31,746,000
Interest rate percentage	7.50%	7.50%
Term loan | Term Loan due December 2021, Non-Recourse
Debt Instrument [Line Items]
Long-term debt, gross	$ 109,109,000	$ 114,761,000
Non-recourse debt	0	114,138,000
Non-recourse debt, non-current	108,958,000	0
Long-term Debt, Total	$ 108,958,000	$ 114,138,000
Interest rate percentage	2.50%	2.50%
LIBOR margin (as a percentage)	2.50%	2.50%
Letters of Credit | Letter of Credit due December 2021, Non-Recourse
Debt Instrument [Line Items]
Long-term debt, gross	$ 0
Non-recourse debt	0
Non-recourse debt, non-current	0
Long-term Debt, Total	0
Non-recourse debt
Debt Instrument [Line Items]
Long-term debt, gross	216,037,000	$ 227,054,000
Non-recourse debt	7,782,000	120,846,000
Non-recourse debt, non-current	205,164,000	102,045,000
Long-term Debt, Total	212,946,000	222,891,000
Unused borrowing capacity	$ 759,000	$ 968,000