Loans Held for Investment, net - Summary of Loans Held for Investment, Net (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2022	Dec. 31, 2021	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Impaired [Line Items]
Principal amount, financial assets	$ 3,925,535	$ 3,500,658
Loan carrying value	3,911,436	3,485,607
CECL reserve	(85,589)	(36,598)	$ (44,378)	$ (34,004)	$ (42,730)	$ (42,152)	$ (40,791)	$ (37,191)
Loans held for investment, net	3,825,847	3,449,009
Variable rate
Financing Receivable, Impaired [Line Items]
Principal amount, financial assets	3,826,230	3,395,022
Fixed rate
Financing Receivable, Impaired [Line Items]
Principal amount, financial assets	99,305	105,636
Commercial mortgage
Financing Receivable, Impaired [Line Items]
Principal amount, financial assets	3,925,535	3,500,658
Loan carrying value	3,911,436	3,485,607
Loans and preferred equity held for investment | Variable rate
Financing Receivable, Impaired [Line Items]
Loan carrying value	3,812,259	3,380,102
Loans and preferred equity held for investment | Fixed rate
Financing Receivable, Impaired [Line Items]
Loan carrying value	99,177	105,505
Loans and preferred equity held for investment | Commercial mortgage
Financing Receivable, Impaired [Line Items]
Loan carrying value	3,911,436	3,485,607
Senior loans | Variable rate
Financing Receivable, Impaired [Line Items]
Principal amount, financial assets	$ 2,170,777	$ 1,576,439
Weighted average coupon (in percentage)	6.80%	4.60%
Weighted average maturity in years	3 years 8 months 12 days	3 years 8 months 12 days
Senior loans | Loans and preferred equity held for investment | Variable rate
Financing Receivable, Impaired [Line Items]
Loan carrying value	$ 2,159,659	$ 1,564,940
Securitized loans | Variable rate
Financing Receivable, Impaired [Line Items]
Principal amount, financial assets	$ 1,643,453	$ 1,806,583
Weighted average coupon (in percentage)	6.20%	4.20%
Weighted average maturity in years	2 years 10 months 24 days	3 years 6 months
Securitized loans | Loans and preferred equity held for investment | Variable rate
Financing Receivable, Impaired [Line Items]
Loan carrying value	$ 1,640,480	$ 1,803,042
Mezzanine loans | Variable rate
Financing Receivable, Impaired [Line Items]
Principal amount, financial assets	$ 12,000	$ 12,000
Weighted average coupon (in percentage)	14.10%	11.50%
Weighted average maturity in years	0 years	8 months 12 days
Mezzanine loans | Fixed rate
Financing Receivable, Impaired [Line Items]
Principal amount, financial assets	$ 99,305	$ 105,636
Weighted average coupon (in percentage)	12.20%	12.40%
Weighted average maturity in years	2 years 10 months 24 days	3 years
Mezzanine loans | Loans and preferred equity held for investment | Variable rate
Financing Receivable, Impaired [Line Items]
Loan carrying value	$ 12,120	$ 12,120
Mezzanine loans | Loans and preferred equity held for investment | Fixed rate
Financing Receivable, Impaired [Line Items]
Loan carrying value	$ 99,177	$ 105,505