Other Assets and Liabilities - Summary of Components of Other Assets (Detail) - USD ($)	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Schedule Of Other Assets [Line Items]
Accrued interest receivable	$ 94,939,000	$ 86,101,000
Derivative assets	51,884,000	30,531,000
Loan portfolio payments held by servicer	23,034,000	77,624,000
Accounts receivable and other assets	2,153,000	572,000
Prepaid expenses	637,000	956,000
Debt securities held-to-maturity	0	78,083,000
CECL reserve	0	(70,000)	$ (889,000)	$ (1,723,000)
Debt securities held-to-maturity, net	0	78,013,000
Total	$ 172,647,000	273,797,000
2018 Single Asset Securitization
Schedule Of Other Assets [Line Items]
Total loan amount, securitized		$ 379,300,000