Loans Held for Investment and Loans Held for Investment at Fair Value - Summary of Loans Held for Investment (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses	$ (4,905)	$ (4,663)	$ (4,262)	$ (3,963)	$ (5,881)	$ (5,845)
Net Loans Held For Investment
Accounts Notes And Loans Receivable [Line Items]
Unpaid principal balance	3,088,950		2,498,466
Deferred loan origination costs	34,754		33,360
Total loans held for investment and loans held for investment at fair value, gross	3,123,704		2,531,826
Allowance for loan losses	(4,905)		(4,262)
Total loans held for investment and loans held for investment at fair value, net	3,118,799		2,527,564
Loans At Fair Value Held For Investment
Accounts Notes And Loans Receivable [Line Items]
Unpaid principal balance	1,308		1,332
Valuation adjustments on FVO loans	43		27
Total loans held for investment and loans held for investment at fair value, gross	1,351		1,359
Total loans held for investment and loans held for investment at fair value, net	1,351		1,359
Total Loans Held For Investment
Accounts Notes And Loans Receivable [Line Items]
Unpaid principal balance	3,090,258		2,499,798
Valuation adjustments on FVO loans	43		27
Deferred loan origination costs	34,754		33,360
Total loans held for investment and loans held for investment at fair value, gross	3,125,055		2,533,185
Allowance for loan losses	(4,905)		(4,262)
Total loans held for investment and loans held for investment at fair value, net	$ 3,120,150		$ 2,528,923