COMMERCIAL MORTGAGE LOANS HELD-FOR-INVESTMENT - Summary of Concentration of Credit Risk (Details) - Commercial Loans Held-For-Investment - Commercial Real Estate Portfolio Segment	9 Months Ended	12 Months Ended
	Sep. 30, 2025	Dec. 31, 2024
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	89.60%	92.30%
Seniors Housing and Healthcare | Collateral Property Type
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percent	9.70%	7.10%
Self-Storage | Collateral Property Type
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percent	0.70%	0.60%
South | Geography
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percent	39.90%	36.60%
Southwest | Geography
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percent	29.60%	32.90%
Mid-Atlantic | Geography
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percent	20.50%	16.10%
Midwest | Geography
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percent	6.10%	7.70%
West | Geography
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percent	3.90%	6.70%