Other Assets and Liabilities - Summary of Components of Other Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020
Schedule Of Other Assets [Line Items]
Accrued interest receivable	$ 146,882			$ 86,101
Derivative assets	94,352			30,531
Loan portfolio payments held by servicer	4,204			77,624
Accounts receivable and other assets	2,529			572
Prepaid expenses	61			956
Debt securities held-to-maturity	0			78,083
CECL reserve	0	$ 0	$ 0	(70)	$ (280)	$ (122)	$ (889)	$ (1,723)
Debt securities held-to-maturity, net	0			78,013
Total	$ 248,028			273,797
2018 Single Asset Securitization
Schedule Of Other Assets [Line Items]
Total loan amount, securitized				$ 379,300