Securities - Securities Available for Sale (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 7,786,039	$ 7,692,860
Gross Unrealized Gains	2,637	4,484
Gross Unrealized Losses	(681,303)	(628,731)
Fair Value	7,107,373	7,068,613
U.S. Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	809,122	1,308,689
Gross Unrealized Gains	773	254
Gross Unrealized Losses	(6,825)	(10,201)
Fair Value	803,070	1,298,742
U.S. Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	661,737	162,406
Gross Unrealized Gains		252
Gross Unrealized Losses	(2,651)	(2,937)
Fair Value	659,086	159,721
Mortgage-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,315,860	4,128,576
Gross Unrealized Gains	812	949
Gross Unrealized Losses	(545,477)	(508,740)
Fair Value	3,771,195	3,620,785
State and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,315,005	1,359,744
Gross Unrealized Gains	110	2,218
Gross Unrealized Losses	(100,388)	(74,987)
Fair Value	1,214,727	1,286,975
Corporates [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	346,030	382,069
Gross Unrealized Losses	(25,675)	(30,794)
Fair Value	320,355	351,275
Collateralized loan obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	338,285	351,376
Gross Unrealized Gains	942	811
Gross Unrealized Losses	(287)	(1,072)
Fair Value	$ 338,940	$ 351,115