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, 2023	Dec. 31, 2022
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	$ 224,979	$ 4,465,728
Available-for-Sale, Less than 12 Months, Unrealized Losses	(1,476)	(480,166)
Available-for-Sale, 12 months or longer, Fair Value	5,742,885	1,992,246
Available-for-Sale, 12 months or longer, Unrealized Losses	(872,667)	(367,308)
Available-for-Sale, Fair Value	5,967,864	6,457,974
Available-for-Sale, Unrealized Losses	(874,143)	(847,474)
U.S. Treasury
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	8,937	130,967
Available-for-Sale, Less than 12 Months, Unrealized Losses	(42)	(3,264)
Available-for-Sale, 12 months or longer, Fair Value	191,027	66,992
Available-for-Sale, 12 months or longer, Unrealized Losses	(11,899)	(1,925)
Available-for-Sale, Fair Value	199,964	197,959
Available-for-Sale, Unrealized Losses	(11,941)	(5,189)
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	0	454,854
Available-for-Sale, Less than 12 Months, Unrealized Losses	0	(75,795)
Available-for-Sale, 12 months or longer, Fair Value	1,189,314	720,226
Available-for-Sale, 12 months or longer, Unrealized Losses	(192,717)	(93,453)
Available-for-Sale, Fair Value	1,189,314	1,175,080
Available-for-Sale, Unrealized Losses	(192,717)	(169,248)
Mortgage-backed securities
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	90,145	3,207,319
Available-for-Sale, Less than 12 Months, Unrealized Losses	(710)	(358,507)
Available-for-Sale, 12 months or longer, Fair Value	3,835,552	1,116,205
Available-for-Sale, 12 months or longer, Unrealized Losses	(621,142)	(258,921)
Available-for-Sale, Fair Value	3,925,697	4,323,524
Available-for-Sale, Unrealized Losses	(621,852)	(617,428)
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	86,865	414,813
Available-for-Sale, Less than 12 Months, Unrealized Losses	(495)	(25,555)
Available-for-Sale, 12 months or longer, Fair Value	259,767	2,703
Available-for-Sale, 12 months or longer, Unrealized Losses	(22,562)	(541)
Available-for-Sale, Fair Value	346,632	417,516
Available-for-Sale, Unrealized Losses	(23,057)	(26,096)
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	11,337	10,811
Available-for-Sale, 12 months or longer, Unrealized Losses	(2,460)	(2,972)
Available-for-Sale, Fair Value	11,337	10,811
Available-for-Sale, Unrealized Losses	(2,460)	(2,972)
Other securities
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-Sale, Less than 12 Months, Fair Value	39,032	257,775
Available-for-Sale, Less than 12 Months, Unrealized Losses	(229)	(17,045)
Available-for-Sale, 12 months or longer, Fair Value	255,888	75,309
Available-for-Sale, 12 months or longer, Unrealized Losses	(21,887)	(9,496)
Available-for-Sale, Fair Value	294,920	333,084
Available-for-Sale, Unrealized Losses	$ (22,116)	$ (26,541)