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Investment Securities - Available-for-Sale and Held-to-Maturity Investment Securities with Unrealized Losses by Aggregated Major Security Type and Length of Time in Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	$ 341,118	$ 1,126,895
Available-for-Sale, Less than 12 Months, Unrealized Losses	(1,136)	(12,668)
Available-for-Sale, 12 months or longer, Fair Value	4,885,808	5,218,733
Available-for-Sale, 12 months or longer, Unrealized Losses	(653,197)	(884,848)
Available-for-Sale, Fair Value	5,226,926	6,345,628
Available-for-Sale, Unrealized Losses	(654,333)	(897,516)
U.S. Treasury
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	0	3,977
Available-for-Sale, Less than 12 Months, Unrealized Losses	0	(26)
Available-for-Sale, 12 months or longer, Fair Value	184,175	177,691
Available-for-Sale, 12 months or longer, Unrealized Losses	(7,615)	(12,633)
Available-for-Sale, Fair Value	184,175	181,668
Available-for-Sale, Unrealized Losses	(7,615)	(12,659)
U.S. government-sponsored entities and agencies
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	79,916	98,280
Available-for-Sale, Less than 12 Months, Unrealized Losses	(78)	(1,713)
Available-for-Sale, 12 months or longer, Fair Value	1,173,044	1,144,618
Available-for-Sale, 12 months or longer, Unrealized Losses	(134,717)	(179,647)
Available-for-Sale, Fair Value	1,252,960	1,242,898
Available-for-Sale, Unrealized Losses	(134,795)	(181,360)
Mortgage-backed securities
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	252,875	857,440
Available-for-Sale, Less than 12 Months, Unrealized Losses	(953)	(9,172)
Available-for-Sale, 12 months or longer, Fair Value	3,157,476	3,406,350
Available-for-Sale, 12 months or longer, Unrealized Losses	(486,252)	(653,009)
Available-for-Sale, Fair Value	3,410,351	4,263,790
Available-for-Sale, Unrealized Losses	(487,205)	(662,181)
States and political subdivisions
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	6,561	133,906
Available-for-Sale, Less than 12 Months, Unrealized Losses	(17)	(1,462)
Available-for-Sale, 12 months or longer, Fair Value	234,389	279,121
Available-for-Sale, 12 months or longer, Unrealized Losses	(17,269)	(24,419)
Available-for-Sale, Fair Value	240,950	413,027
Available-for-Sale, Unrealized Losses	(17,286)	(25,881)
Pooled trust preferred securities
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	0	0
Available-for-Sale, Less than 12 Months, Unrealized Losses	0	0
Available-for-Sale, 12 months or longer, Fair Value	11,734	11,322
Available-for-Sale, 12 months or longer, Unrealized Losses	(2,085)	(2,485)
Available-for-Sale, Fair Value	11,734	11,322
Available-for-Sale, Unrealized Losses	(2,085)	(2,485)
Other securities
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	1,766	33,292
Available-for-Sale, Less than 12 Months, Unrealized Losses	(88)	(295)
Available-for-Sale, 12 months or longer, Fair Value	124,990	199,631
Available-for-Sale, 12 months or longer, Unrealized Losses	(5,259)	(12,655)
Available-for-Sale, Fair Value	126,756	232,923
Available-for-Sale, Unrealized Losses	$ (5,347)	$ (12,950)

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Amount, before tax, of unrealized loss 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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