Disclosures About Fair Value of Financial Instruments - Statement of Changes in Level 3 Assets Measured at Fair Value on a Recurring Basis (Detail) - Significant Unobservable Inputs (Level 3) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Residential Mortgage Loan Commitments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 98	$ 301	$ 179	$ 200
Issuances	41	163	288	660
Net (increase) decrease in allowance for credit losses	(98)	(301)	(426)	(697)
Balance at end of period	41	$ 163	41	$ 163
Asset-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	106,919		142,885
Principal payments and premium amortization	(16,852)		(51,348)
Credit losses	158		(253)
Change in fair value recognized in OCI	(2,339)		(3,398)
Balance at end of period	$ 87,886		$ 87,886