Concentration of Credit Risk - Summary of Loan Portfolio by Loan Category Type (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Loans And Leases Receivable Disclosure [Line Items]
Loan Commitment	$ 5,318,297	$ 4,943,511
Unfunded Commitment	$ 488,916	$ 423,487
% Loan Commitment	100.00%	100.00%
Loan UPB	$ 4,833,535	$ 4,524,725
% of Loan UPB	100.00%	100.00%
Light Transitional
Loans And Leases Receivable Disclosure [Line Items]
Loan Commitment	$ 1,924,901	$ 1,937,644
Unfunded Commitment	$ 155,159	$ 173,518
% Loan Commitment	36.20%	39.20%
Loan UPB	$ 1,769,742	$ 1,764,126
% of Loan UPB	36.60%	39.00%
Moderate Transitional
Loans And Leases Receivable Disclosure [Line Items]
Loan Commitment	$ 1,987,642	$ 1,633,131
Unfunded Commitment	$ 308,682	$ 224,532
% Loan Commitment	37.40%	33.00%
Loan UPB	$ 1,680,654	$ 1,410,145
% of Loan UPB	34.80%	31.20%
Bridge
Loans And Leases Receivable Disclosure [Line Items]
Loan Commitment	$ 1,370,754	$ 1,337,736
Unfunded Commitment	$ 24,337	$ 22,953
% Loan Commitment	25.70%	27.10%
Loan UPB	$ 1,348,877	$ 1,317,938
% of Loan UPB	27.90%	29.10%
Construction
Loans And Leases Receivable Disclosure [Line Items]
Loan Commitment	$ 35,000	$ 35,000
Unfunded Commitment	$ 738	$ 2,484
% Loan Commitment	0.70%	0.70%
Loan UPB	$ 34,262	$ 32,516
% of Loan UPB	0.70%	0.70%