DEBT - Schedule of Long Term Debt (Details) $ in Thousands, $ in Millions	Sep. 30, 2021 USD ($)	Sep. 30, 2021 CAD ($)	Jul. 31, 2021	Dec. 31, 2020 USD ($)	Aug. 31, 2018
Debt Instrument [Line Items]
Debt	$ 1,131,998			$ 819,661
7.50% Senior Secured Notes
Debt Instrument [Line Items]
Stated interest rate	7.50%	7.50%
8.25% Senior Secured Notes
Debt Instrument [Line Items]
Stated interest rate	8.25%	8.25%
Senior Notes
Debt Instrument [Line Items]
Stated interest rate			7.50%
Senior Notes | 7.50% Senior Secured Notes
Debt Instrument [Line Items]
Stated interest rate	7.50%	7.50%	7.50%
Debt	$ 734,533			$ 0
Senior Notes | 8.25% Senior Secured Notes
Debt Instrument [Line Items]
Stated interest rate	8.25%	8.25%		8.25%	8.25%
Debt	$ 0			$ 680,000
Line of Credit | Non-Recourse U.S. SPV facility
Debt Instrument [Line Items]
Debt	44,900
Line of Credit | Revolving Credit Facility | Non-Recourse U.S. SPV facility
Debt Instrument [Line Items]
Debt	44,940			43,586
Line of Credit | Revolving Credit Facility | Non-Recourse Canada SPV Facility
Debt Instrument [Line Items]
Debt	96,821	$ 96.8		96,075
Line of Credit | Revolving Credit Facility | Non-Recourse Flexiti SPE Facility
Debt Instrument [Line Items]
Debt	$ 255,704			$ 0