VARIABLE INTEREST ENTITIES - Carrying Amounts of Consolidated VIE Assets and Liabilities (Details) $ in Thousands	Sep. 30, 2021 USD ($) facility	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)
Assets
Restricted cash	$ 66,168	$ 54,765	$ 62,527
Loans receivable, net	809,813	467,560
Prepaid expenses and other	31,558	27,994
Deferred tax assets	7,850	0
Total Assets	1,592,123	1,182,986
Liabilities
Accounts payable and accrued liabilities	75,701	49,624
Deferred revenue	15,243	5,394
Accrued interest	11,106	20,123
Debt	1,131,998	819,661
Total Liabilities	$ 1,394,640	1,051,081
Variable Interest Entity
Variable Interest Entity [Line Items]
Number of credit facilities held | facility	3
Assets
Restricted cash	$ 42,214	31,994	$ 33,696
Loans receivable, net	649,192	306,302
Intercompany receivable	84,811	15,382
Prepaid expenses and other	0	388
Deferred tax assets	105	105
Total Assets	776,322	354,171
Liabilities
Accounts payable and accrued liabilities	6,840	34,055
Deferred revenue	110	136
Accrued interest	1,418	1,147
Debt	397,465	139,661
Total Liabilities	$ 405,833	$ 174,999