MORTGAGE LOAN RECEIVABLES - Activity in Loan Portfolio (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2020	Mar. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2020	Dec. 31, 2018
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Mortgage loans receivable, beginning balance		$ 3,482,929	$ 2,343,070	$ 3,358,861	$ 3,482,929
Origination of mortgage loan receivables			2,530,247	566,506	2,398,227
Purchases of mortgage loan receivables			63,600		9,934
Repayment of mortgage loan receivables			(1,059,979)	(961,236)	(1,532,346)
Proceeds from sales of mortgage loan receivables			(305,649)	(582,764)	(1,024,357)
Non-cash disposition of loans via foreclosure			(81,289)	(31,249)	(45,529)
Sale of loans, net	$ (1,571)		8,398	(1,571)	54,758
Transfer between held for investment and held for sale					0
Accretion/amortization of discount, premium and other fees			13,832	15,530	17,845
Mortgage loans receivable, ending balance	2,343,070		3,521,985	2,343,070	3,358,861
Allowance for credit losses	(41,507)		(31,752)	(41,507)		$ (11,600)
Release of asset-specific loan loss provision via foreclosure			1,150	2,500
Provision expense for current expected credit loss				(4,964)
Provision expense for current expected credit loss (impact to earnings)			8,605	(18,543)	(2,600)
Mortgage loans transferred but not considered sold, at amortized cost, outstanding face amount		15,400
Mortgage loans transferred but not considered sold, at amortized cost, book value		$ 15,500
Mortgage loans transferred but not considered sold, at amortized cost, remaining maturity		9 years 9 months 18 days
Total mortgage loans receivable
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Mortgage loans receivable, beginning balance		$ 3,318,390	2,354,059	3,257,036	3,318,390
Origination of mortgage loan receivables					1,452,049
Purchases of mortgage loan receivables					0
Repayment of mortgage loan receivables					(1,531,551)
Proceeds from sales of mortgage loan receivables					0
Non-cash disposition of loans via foreclosure					(45,529)
Sale of loans, net					0
Transfer between held for investment and held for sale					45,832
Accretion/amortization of discount, premium and other fees					17,845
Mortgage loans receivable, ending balance	2,354,059		3,553,737	2,354,059	3,257,036
Total mortgage loan receivables held for investment, net, at amortized cost
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Mortgage loans receivable, beginning balance		3,318,390	2,354,059	3,257,036	3,318,390
Origination of mortgage loan receivables			2,309,888	353,661	1,452,049
Purchases of mortgage loan receivables			63,600		0
Repayment of mortgage loan receivables			(1,059,796)	(960,832)	(1,531,551)
Proceeds from sales of mortgage loan receivables			(46,557)	(270,491)	0
Non-cash disposition of loans via foreclosure			(81,289)	(31,249)	(45,529)
Sale of loans, net			0	(9,596)	0
Transfer between held for investment and held for sale					45,832
Accretion/amortization of discount, premium and other fees			13,832	15,530	17,845
Mortgage loans receivable, ending balance	2,354,059		3,553,737	2,354,059	3,257,036
Allowance for credit losses	(41,507)		(31,752)	(41,507)	(20,500)		$ (17,900)
Release of asset-specific loan loss provision via foreclosure			1,150	2,500
Provision expense for current expected credit loss				(4,964)
Provision expense for current expected credit loss (impact to earnings)			8,605	(18,543)	(2,600)
Mortgage loan  receivables held for sale
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Mortgage loans receivable, beginning balance		$ 182,439	30,518	122,325	182,439
Origination of mortgage loan receivables			220,359	212,845	946,178
Purchases of mortgage loan receivables					9,934
Repayment of mortgage loan receivables			(183)	(404)	(795)
Proceeds from sales of mortgage loan receivables			(259,092)	(312,273)	(1,008,853)
Non-cash disposition of loans via foreclosure			0	0	0
Sale of loans, net			8,398	8,025	54,758
Transfer between held for investment and held for sale					(61,336)
Accretion/amortization of discount, premium and other fees			0	0	0
Mortgage loans receivable, ending balance	$ 30,518		$ 0	30,518	122,325
Mortgage loans transferred but not considered sold
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Mortgage loans receivable, beginning balance				$ 0
Proceeds from sales of mortgage loan receivables					(15,504)
Transfer between held for investment and held for sale					15,504
Mortgage loans receivable, ending balance					$ 0