DEBT - Non-Recourse U.S. SPV Facility (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Debt	$ 1,131,998	$ 819,661
Non-Recourse U.S. SPV facility | Line of Credit
Debt Instrument [Line Items]
Debt	44,900
Deferred financing costs	4,500
Non-Recourse U.S. SPV facility | Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Line of credit facility, borrowing capacity	$ 200,000
Commitment fee (as percent)	0.50%
Debt	$ 44,940	$ 43,586
Non-Recourse U.S. SPV facility | Revolving Credit Facility | Line of Credit | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread	6.25%