COMMERCIAL MORTGAGE LOANS HELD-FOR-INVESTMENT - Summary of Concentration of Credit Risk (Details) - Commercial Loans Held-For-Investment - Commercial Real Estate Portfolio Segment	3 Months Ended	6 Months Ended
	Mar. 31, 2023	Jun. 30, 2022
Geography
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percent	100.00%	100.00%
Collateral Property Type
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percent	100.00%	100.00%
Multifamily | Collateral Property Type
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percent	89.70%	89.60%
Seniors Housing and Healthcare | Collateral Property Type
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percent	6.80%	6.40%
Self-Storage | Collateral Property Type
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percent	1.90%	1.80%
Retail | Collateral Property Type
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percent	1.60%	1.60%
Office | Collateral Property Type
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percent	0.00%	0.60%
South | Geography
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percent	45.30%	46.60%
Southwest | Geography
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percent	28.10%	26.70%
Mid-Atlantic | Geography
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percent	12.20%	12.40%
Midwest | Geography
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percent	7.80%	8.00%
West | Geography
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percent	6.60%	6.30%