COMMERCIAL MORTGAGE LOANS HELD-FOR-INVESTMENT Summary of Concentration of Credit Risk (Details) - Commercial loans held-for-investment	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Collateral Property Type
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk (as a percentage)	100.00%	100.00%
Commercial real estate portfolio segment | Geography
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk (as a percentage)	100.00%	100.00%
Commercial real estate portfolio segment | Multifamily | Collateral Property Type
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk (as a percentage)	92.00%	89.50%
Commercial real estate portfolio segment | Self-Storage | Collateral Property Type
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk (as a percentage)	5.20%	0.80%
Commercial real estate portfolio segment | Retail | Collateral Property Type
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk (as a percentage)	1.70%	6.40%
Commercial real estate portfolio segment | Office | Collateral Property Type
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk (as a percentage)	1.10%	3.30%
Commercial real estate portfolio segment | South | Geography
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk (as a percentage)	46.20%	36.50%
Commercial real estate portfolio segment | Southwest | Geography
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk (as a percentage)	27.50%	38.70%
Commercial real estate portfolio segment | West | Geography
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk (as a percentage)	13.90%	1.80%
Commercial real estate portfolio segment | Mid-Atlantic | Geography
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk (as a percentage)	7.90%	6.20%
Commercial real estate portfolio segment | Midwest | Geography
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk (as a percentage)	4.50%	16.80%