FAIR VALUE MEASUREMENTS - Summary of Assets and Liabilities Measured and Not Measured at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Jul. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Aug. 31, 2018
Financial assets:
Restricted cash	$ 66,168		$ 54,765	$ 62,527
Financial liabilities:
Contingent consideration related to acquisition	$ 24,129		$ 0
Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate		7.50%
7.50% Senior Secured Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	7.50%
7.50% Senior Secured Notes | Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	7.50%	7.50%
8.25% Senior Secured Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	8.25%
8.25% Senior Secured Notes | Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	8.25%		8.25%		8.25%
Fair Value, Measurements, Recurring | Measurement period adjustments
Financial assets:
Cash Surrender Value of Life Insurance	$ 7,994		$ 7,140
Financial liabilities:
Non-qualified deferred compensation plan	4,945		4,690
Contingent consideration related to acquisition	24,129
Fair Value, Measurements, Recurring | Estimated Fair Value
Financial assets:
Cash Surrender Value of Life Insurance	7,994		7,140
Financial liabilities:
Non-qualified deferred compensation plan	4,945		4,690
Contingent consideration related to acquisition	24,129
Fair Value, Measurements, Recurring | Estimated Fair Value | Level 1
Financial assets:
Cash Surrender Value of Life Insurance	7,994		7,140
Financial liabilities:
Non-qualified deferred compensation plan	4,945		4,690
Contingent consideration related to acquisition	0
Fair Value, Measurements, Recurring | Estimated Fair Value | Level 2
Financial assets:
Cash Surrender Value of Life Insurance	0		0
Financial liabilities:
Non-qualified deferred compensation plan	0		0
Contingent consideration related to acquisition	0
Fair Value, Measurements, Recurring | Estimated Fair Value | Level 3
Financial assets:
Cash Surrender Value of Life Insurance	0		0
Financial liabilities:
Non-qualified deferred compensation plan	0		0
Contingent consideration related to acquisition	24,129
Fair Value, Measurements, Nonrecurring | Measurement period adjustments
Financial assets:
Cash and cash equivalents	205,785		213,343
Restricted cash	66,168		54,765
Loans receivable, net	809,813		467,560
Financial liabilities:
Liability for losses on CSO lender-owned consumer loans	7,007		7,228
Fair Value, Measurements, Nonrecurring | Measurement period adjustments | 7.50% Senior Secured Notes | Senior Notes
Financial liabilities:
Debt	734,533
Fair Value, Measurements, Nonrecurring | Measurement period adjustments | 8.25% Senior Secured Notes | Senior Notes
Financial liabilities:
Debt			680,000
Fair Value, Measurements, Nonrecurring | Measurement period adjustments | Non-Recourse U.S. SPV facility
Financial liabilities:
Debt	44,940		43,586
Fair Value, Measurements, Nonrecurring | Measurement period adjustments | Non-Recourse Canada SPV Facility
Financial liabilities:
Debt	96,821		96,075
Fair Value, Measurements, Nonrecurring | Measurement period adjustments | Non-Recourse Flexiti SPE Facility
Financial liabilities:
Debt	255,704
Fair Value, Measurements, Nonrecurring | Estimated Fair Value
Financial assets:
Cash and cash equivalents	205,785		213,343
Restricted cash	66,168		54,765
Loans receivable, net	809,813		467,560
Financial liabilities:
Liability for losses on CSO lender-owned consumer loans	7,007		7,228
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | 7.50% Senior Secured Notes | Senior Notes
Financial liabilities:
Debt	757,650
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | 8.25% Senior Secured Notes | Senior Notes
Financial liabilities:
Debt			646,000
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | Non-Recourse U.S. SPV facility
Financial liabilities:
Debt	49,456		49,456
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | Non-Recourse Canada SPV Facility
Financial liabilities:
Debt	97,818		97,971
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | Non-Recourse Flexiti SPE Facility
Financial liabilities:
Debt	259,940
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | Level 1
Financial assets:
Cash and cash equivalents	205,785		213,343
Restricted cash	66,168		54,765
Loans receivable, net	0		0
Financial liabilities:
Liability for losses on CSO lender-owned consumer loans	0		0
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | Level 1 | 7.50% Senior Secured Notes | Senior Notes
Financial liabilities:
Debt	0
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | Level 1 | 8.25% Senior Secured Notes | Senior Notes
Financial liabilities:
Debt			0
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | Level 1 | Non-Recourse U.S. SPV facility
Financial liabilities:
Debt	0		0
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | Level 1 | Non-Recourse Canada SPV Facility
Financial liabilities:
Debt	0		0
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | Level 1 | Non-Recourse Flexiti SPE Facility
Financial liabilities:
Debt	0
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | Level 2
Financial assets:
Cash and cash equivalents	0		0
Restricted cash	0		0
Loans receivable, net	0		0
Financial liabilities:
Liability for losses on CSO lender-owned consumer loans	0		0
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | Level 2 | 7.50% Senior Secured Notes | Senior Notes
Financial liabilities:
Debt	757,650
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | Level 2 | 8.25% Senior Secured Notes | Senior Notes
Financial liabilities:
Debt			646,000
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | Level 2 | Non-Recourse U.S. SPV facility
Financial liabilities:
Debt	0		0
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | Level 2 | Non-Recourse Canada SPV Facility
Financial liabilities:
Debt	0		0
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | Level 2 | Non-Recourse Flexiti SPE Facility
Financial liabilities:
Debt	0
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | Level 3
Financial assets:
Cash and cash equivalents	0		0
Restricted cash	0		0
Loans receivable, net	809,813		467,560
Financial liabilities:
Liability for losses on CSO lender-owned consumer loans	7,007		7,228
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | Level 3 | 7.50% Senior Secured Notes | Senior Notes
Financial liabilities:
Debt	0
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | Level 3 | 8.25% Senior Secured Notes | Senior Notes
Financial liabilities:
Debt			0
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | Level 3 | Non-Recourse U.S. SPV facility
Financial liabilities:
Debt	49,456		49,456
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | Level 3 | Non-Recourse Canada SPV Facility
Financial liabilities:
Debt	97,818		$ 97,971
Fair Value, Measurements, Nonrecurring | Estimated Fair Value | Level 3 | Non-Recourse Flexiti SPE Facility
Financial liabilities:
Debt	$ 259,940