Concentration of Credit Risk - Summary of Loans Held for Investment Portfolio by Loan Category Type (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Loans And Leases Receivable Disclosure [Line Items]
Loan commitment	$ 5,186,472	$ 5,411,944
Unfunded commitment	$ 470,869	$ 487,773
% of loan commitment	100.00%	100.00%
Outstanding principal	$ 4,710,161	$ 4,919,343
% of loan UPB	100.00%	100.00%
Moderate Transitional
Loans And Leases Receivable Disclosure [Line Items]
Loan commitment	$ 1,735,717	$ 1,950,739
Unfunded commitment	$ 270,443	$ 294,693
% of loan commitment	33.40%	36.10%
Outstanding principal	$ 1,466,446	$ 1,657,218
% of loan UPB	31.10%	33.70%
Bridge
Loans And Leases Receivable Disclosure [Line Items]
Loan commitment	$ 1,684,247	$ 1,646,895
Unfunded commitment	$ 49,873	$ 47,459
% of loan commitment	32.50%	30.40%
Outstanding principal	$ 1,627,760	$ 1,593,436
% of loan UPB	34.60%	32.40%
Light Transitional
Loans And Leases Receivable Disclosure [Line Items]
Loan commitment	$ 1,680,908	$ 1,779,310
Unfunded commitment	$ 128,953	$ 145,621
% of loan commitment	32.40%	32.90%
Outstanding principal	$ 1,551,955	$ 1,633,689
% of loan UPB	32.90%	33.20%
Construction
Loans And Leases Receivable Disclosure [Line Items]
Loan commitment	$ 85,600	$ 35,000
Unfunded commitment	$ 21,600	$ 0
% of loan commitment	1.70%	0.60%
Outstanding principal	$ 64,000	$ 35,000
% of loan UPB	1.40%	0.70%