Securities - Securities Available for Sale (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 7,207,331	$ 7,692,860
Gross Unrealized Gains	2,130	4,484
Gross Unrealized Losses	(668,070)	(628,731)
Fair Value	6,541,391	7,068,613
U.S. Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	809,561	1,308,689
Gross Unrealized Gains	155	254
Gross Unrealized Losses	(7,216)	(10,201)
Fair Value	802,500	1,298,742
U.S. Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	161,766	162,406
Gross Unrealized Gains	4	252
Gross Unrealized Losses	(2,748)	(2,937)
Fair Value	159,022	159,721
Mortgage-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,213,875	4,128,576
Gross Unrealized Gains	463	949
Gross Unrealized Losses	(540,155)	(508,740)
Fair Value	3,674,183	3,620,785
State and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,323,080	1,359,744
Gross Unrealized Gains	563	2,218
Gross Unrealized Losses	(89,723)	(74,987)
Fair Value	1,233,920	1,286,975
Corporates [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	357,878	382,069
Gross Unrealized Losses	(27,841)	(30,794)
Fair Value	330,037	351,275
Collateralized loan obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	341,171	351,376
Gross Unrealized Gains	945	811
Gross Unrealized Losses	(387)	(1,072)
Fair Value	$ 341,729	$ 351,115