Securities - Schedule of Amortized Cost, Fair Value and Gross Unrealized Gains and Losses for Securities Held to Maturity (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Schedule Of Held To Maturity Securities [Line Items]
Amortized Cost	$ 5,709,541	$ 1,480,416
Gross Unrealized Gains	808	3,360
Gross Unrealized Losses	(464,898)	(41,385)
Held to Maturity, Fair value	5,245,451	1,442,391
Allowance for Credit Losses	(2,259)	(1,940)
Net Carrying Amount	5,707,282	1,478,476
U.S. Agencies [Member]
Schedule Of Held To Maturity Securities [Line Items]
Amortized Cost	123,033
Gross Unrealized Losses	(1,177)
Held to Maturity, Fair value	121,856
Net Carrying Amount	123,033
Mortgage-backed [Member]
Schedule Of Held To Maturity Securities [Line Items]
Amortized Cost	3,088,814	396,134
Gross Unrealized Gains	160	14
Gross Unrealized Losses	(212,959)	(2,431)
Held to Maturity, Fair value	2,876,015	393,717
Net Carrying Amount	3,088,814	396,134
State and political subdivisions [Member]
Schedule Of Held To Maturity Securities [Line Items]
Amortized Cost	2,497,694	1,084,282
Gross Unrealized Gains	648	3,346
Gross Unrealized Losses	(250,762)	(38,954)
Held to Maturity, Fair value	2,247,580	1,048,674
Allowance for Credit Losses	(2,259)	(1,940)
Net Carrying Amount	$ 2,495,435	$ 1,082,342