Fair Value Measurements - Changes in Level 3 Assets and Liabilities Measured at Estimated Fair Value on Recurring Basis (Detail) - Fair Value Measurements, Recurring [Member] - Significant Unobservable Inputs (Level 3) [Member] - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Privately Issued Mortgage-Backed Securities [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance					$ 16
Total gains realized/unrealized:
Settlements					(16)
Other Assets and Other Liabilities [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance		$ (24,181)	$ 35,666	$ 6,440	43,234
Total gains realized/unrealized:
Included in earnings	[1]	(9,321)	44,152	(34,630)	102,489
Transfers out of Level 3	[2]	(14,804)	(59,673)	(20,116)	(125,578)
Ending Balance		(48,306)	20,145	(48,306)	20,145
Changes in unrealized gains included in earnings related to assets still held at end of period	[1]	$ (17,160)	$ 18,196	$ (48,108)	$ 21,722

[1] Reported as mortgage banking revenues in the consolidated statement of income and includes the fair value of commitment issuances and expirations.

[2] Transfers out of Level 3 consist of interest rate locks transferred to closed loans.