Commercial Mortgage Loans, Held for Investment - Schedule of Commercial Mortgage Loans, Held for Investment Portfolio (Details) - Commercial Mortgage Receivable, Held-For-Investment - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2026	Dec. 31, 2025
Accounts, Notes, Loans and Financing Receivable [Line Items]
Par Value	$ 4,609,278	$ 4,435,511
Customer Concentration Risk \| Commercial mortgage loans, held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage	100.00%	100.00%
Geographic Concentration Risk \| Commercial mortgage loans, held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage	100.00%	100.00%
Southeast
Accounts, Notes, Loans and Financing Receivable [Line Items]
Par Value	$ 1,840,930	$ 1,832,831
Southeast \| Geographic Concentration Risk \| Commercial mortgage loans, held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage	39.80%	41.40%
Southwest
Accounts, Notes, Loans and Financing Receivable [Line Items]
Par Value	$ 1,496,133	$ 1,431,471
Southwest \| Geographic Concentration Risk \| Commercial mortgage loans, held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage	32.50%	32.30%
Mideast
Accounts, Notes, Loans and Financing Receivable [Line Items]
Par Value	$ 381,080	$ 348,750
Mideast \| Geographic Concentration Risk \| Commercial mortgage loans, held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage	8.30%	7.90%
Far West
Accounts, Notes, Loans and Financing Receivable [Line Items]
Par Value	$ 185,940	$ 239,874
Far West \| Geographic Concentration Risk \| Commercial mortgage loans, held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage	4.00%	5.40%
New England
Accounts, Notes, Loans and Financing Receivable [Line Items]
Par Value	$ 136,899	$ 125,982
New England \| Geographic Concentration Risk \| Commercial mortgage loans, held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage	3.00%	2.80%
Great Lakes
Accounts, Notes, Loans and Financing Receivable [Line Items]
Par Value	$ 128,674	$ 108,095
Great Lakes \| Geographic Concentration Risk \| Commercial mortgage loans, held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage	2.80%	2.40%
Rocky Mountain
Accounts, Notes, Loans and Financing Receivable [Line Items]
Par Value	$ 113,030	$ 76,180
Rocky Mountain \| Geographic Concentration Risk \| Commercial mortgage loans, held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage	2.50%	1.70%
Various
Accounts, Notes, Loans and Financing Receivable [Line Items]
Par Value	$ 326,592	$ 272,328
Various \| Geographic Concentration Risk \| Commercial mortgage loans, held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage	7.10%	6.10%
Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Par Value	$ 3,647,729	$ 3,434,672
Multifamily \| Customer Concentration Risk \| Commercial mortgage loans, held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage	79.30%	77.50%
Hospitality
Accounts, Notes, Loans and Financing Receivable [Line Items]
Par Value	$ 490,423	$ 515,144
Hospitality \| Customer Concentration Risk \| Commercial mortgage loans, held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage	10.60%	11.60%
Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Par Value	$ 272,910	$ 309,522
Industrial \| Customer Concentration Risk \| Commercial mortgage loans, held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage	5.90%	7.00%
Office
Accounts, Notes, Loans and Financing Receivable [Line Items]
Par Value	$ 57,112	$ 58,259
Office \| Customer Concentration Risk \| Commercial mortgage loans, held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage	1.20%	1.30%
Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Par Value	$ 1,986	$ 1,986
Retail \| Customer Concentration Risk \| Commercial mortgage loans, held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage	0.00%	0.00%
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Par Value	$ 139,118	$ 115,928
Other \| Customer Concentration Risk \| Commercial mortgage loans, held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage	3.00%	2.60%

Commercial Mortgage Loans, Held for Investment - Schedule of Commercial Mortgage Loans, Held for Investment Portfolio (Details) - Commercial Mortgage Receivable, Held-For-Investment - USD ($)
$ in Thousands