Securities - Securities Available for Sale (Detail) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 11,453,157	$ 8,407,676
Gross Unrealized Gains	41,165	4,823
Gross Unrealized Losses	(598,663)	(638,165)
Fair Value	10,895,659	7,774,334
U.S. Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,579,100	1,331,394
Gross Unrealized Gains	8,949	2,751
Gross Unrealized Losses	(2,870)	(8,072)
Fair Value	1,585,179	1,326,073
U.S. Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	107,559	129,246
Gross Unrealized Gains	340	126
Gross Unrealized Losses	(235)	(325)
Fair Value	107,664	129,047
Mortgage-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,413,094	4,945,548
Gross Unrealized Gains	17,073	339
Gross Unrealized Losses	(469,240)	(524,957)
Fair Value	5,960,927	4,420,930
State and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,530,711	1,309,126
Gross Unrealized Gains	14,329	487
Gross Unrealized Losses	(114,740)	(91,044)
Fair Value	2,430,300	1,218,569
Corporates [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	308,896	330,739
Gross Unrealized Gains	177	60
Gross Unrealized Losses	(10,612)	(13,629)
Fair Value	298,461	317,170
Collateralized loan obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	513,797	361,623
Gross Unrealized Gains	297	1,060
Gross Unrealized Losses	(966)	(138)
Fair Value	$ 513,128	$ 362,545