Securities - Schedule of Fair Value and Amortized Cost of Available-for-sale and Held-to-maturity Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale, Amortized Cost	$ 2,541,107	$ 2,501,188
Available-for-sale, Gross Unrealized Gains	384	225
Available-for-sale, Gross Unrealized Losses	(295,419)	(307,084)
Available-for-sale, Estimated Fair Value	2,246,072	2,194,329
Held-to-maturity, Amortized Cost	1,152,906	1,199,527
Held-to-maturity, Gross Unrealized Gains	164	852
Held-to-maturity, Gross Unrealized Losses	(146,253)	(131,220)
Held-to-maturity securities, Fair value	1,006,817	1,069,159
Total debt securities, Amortized Cost	3,694,013	3,700,715
Total debt securities, Gross Unrealized Gains	548	1,077
Total debt securities, Gross Unrealized Losses	(441,672)	(438,304)
Total securities, Estimated Fair Value	3,252,889	3,263,488
US Treasury Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale, Amortized Cost	146,113
Available-for-sale, Gross Unrealized Gains	63
Available-for-sale, Gross Unrealized Losses	(63)
Available-for-sale, Estimated Fair Value	146,113
U.S. Government Sponsored Entities and Agencies [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale, Amortized Cost	224,944	238,676
Available-for-sale, Gross Unrealized Losses	(30,702)	(30,310)
Available-for-sale, Estimated Fair Value	194,242	208,366
Held-to-maturity, Amortized Cost	2,988	3,587
Held-to-maturity, Gross Unrealized Losses	(260)	(313)
Held-to-maturity securities, Fair value	2,728	3,274
Residential Mortgage-Backed Securities and Collateralized Mortgage Obligations of Government Sponsored Entities and Agencies [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale, Amortized Cost	1,850,284	1,897,511
Available-for-sale, Gross Unrealized Gains	245	47
Available-for-sale, Gross Unrealized Losses	(257,088)	(267,874)
Available-for-sale, Estimated Fair Value	1,593,441	1,629,684
Held-to-maturity, Amortized Cost	32,803	38,893
Held-to-maturity, Gross Unrealized Losses	(2,754)	(3,017)
Held-to-maturity securities, Fair value	30,049	35,876
Commercial Mortgage-Backed Securities and Collateralized Mortgage Obligations of Government Sponsored Entities and Agencies [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale, Amortized Cost	235,873	274,220
Available-for-sale, Gross Unrealized Gains	51	11
Available-for-sale, Gross Unrealized Losses	(4,142)	(5,924)
Available-for-sale, Estimated Fair Value	231,782	268,307
Obligations of State and Political Subdivisions [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale, Amortized Cost	71,919	78,819
Available-for-sale, Gross Unrealized Gains	25	167
Available-for-sale, Gross Unrealized Losses	(3,324)	(2,861)
Available-for-sale, Estimated Fair Value	68,620	76,125
Held-to-maturity, Amortized Cost	1,098,957	1,136,779
Held-to-maturity, Gross Unrealized Gains	164	852
Held-to-maturity, Gross Unrealized Losses	(143,130)	(127,518)
Held-to-maturity securities, Fair value	955,991	1,010,113
Corporate Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale, Amortized Cost	11,974	11,962
Available-for-sale, Gross Unrealized Losses	(100)	(115)
Available-for-sale, Estimated Fair Value	11,874	11,847
Held-to-maturity, Amortized Cost	18,158	20,268
Held-to-maturity, Gross Unrealized Losses	(109)	(372)
Held-to-maturity securities, Fair value	$ 18,049	$ 19,896

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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