Securities - Schedule of Amortized Cost, Fair Value and Gross Unrealized Gains and Losses for Securities Held to Maturity (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Schedule Of Held To Maturity Securities [Line Items]
Amortized Cost	$ 5,837,706	$ 1,480,416
Gross Unrealized Gains	285	3,360
Gross Unrealized Losses	(758,185)	(41,385)
Held to Maturity, Fair value	5,079,806	1,442,391
Allowance for Credit Losses	(2,519)	(1,940)
Net Carrying Amount	5,835,187	1,478,476
U.S. Agencies [Member]
Schedule Of Held To Maturity Securities [Line Items]
Amortized Cost	123,062
Gross Unrealized Losses	(4,139)
Held to Maturity, Fair value	118,923
Net Carrying Amount	123,062
Mortgage-backed [Member]
Schedule Of Held To Maturity Securities [Line Items]
Amortized Cost	3,016,432	396,134
Gross Unrealized Gains		14
Gross Unrealized Losses	(380,177)	(2,431)
Held to Maturity, Fair value	2,636,255	393,717
Net Carrying Amount	3,016,432	396,134
State and political subdivisions [Member]
Schedule Of Held To Maturity Securities [Line Items]
Amortized Cost	2,698,212	1,084,282
Gross Unrealized Gains	285	3,346
Gross Unrealized Losses	(373,869)	(38,954)
Held to Maturity, Fair value	2,324,628	1,048,674
Allowance for Credit Losses	(2,519)	(1,940)
Net Carrying Amount	$ 2,695,693	$ 1,082,342