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		6 Months Ended
		Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Privately Issued Mortgage-Backed Securities [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance			$ 16		$ 16
Total gains realized/unrealized:
Settlements			(16)		(16)
Other Assets and Other Liabilities [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance		$ (15,428)	13,757	$ 6,440	43,234
Total gains realized/unrealized:
Included in earnings	[1]	(6,609)	52,312	(25,309)	58,337
Transfers out of Level 3	[2]	(2,144)	(30,403)	(5,312)	(65,905)
Ending Balance		(24,181)	35,666	(24,181)	35,666
Changes in unrealized gains included in earnings related to assets still held at end of period	[1]	$ (8,441)	$ 37,300	$ 3,405	$ 35,492

[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.