Securities - Schedule of Amortized Cost, Fair Value and Gross Unrealized Gains and Losses for Securities Held to Maturity (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Schedule Of Held To Maturity Securities [Line Items]
Amortized Cost	$ 4,602,232	$ 1,480,416
Gross Unrealized Gains	377	3,360
Gross Unrealized Losses	(209,154)	(41,385)
Held to Maturity, Fair value	4,393,455	1,442,391
Allowance for Credit Losses	(2,045)	(1,940)
Net Carrying Amount	4,600,187	1,478,476
U.S. Agencies [Member]
Schedule Of Held To Maturity Securities [Line Items]
Amortized Cost	6,000
Gross Unrealized Gains	4
Held to Maturity, Fair value	6,004
Net Carrying Amount	6,000
Mortgage-backed [Member]
Schedule Of Held To Maturity Securities [Line Items]
Amortized Cost	2,490,693	396,134
Gross Unrealized Gains	10	14
Gross Unrealized Losses	(66,501)	(2,431)
Held to Maturity, Fair value	2,424,202	393,717
Net Carrying Amount	2,490,693	396,134
State and political subdivisions [Member]
Schedule Of Held To Maturity Securities [Line Items]
Amortized Cost	2,105,539	1,084,282
Gross Unrealized Gains	363	3,346
Gross Unrealized Losses	(142,653)	(38,954)
Held to Maturity, Fair value	1,963,249	1,048,674
Allowance for Credit Losses	(2,045)	(1,940)
Net Carrying Amount	$ 2,103,494	$ 1,082,342