Investment Securities - Securities With Unrealized Losses (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Available-for-sale
Available-for-sale, less than 12 months, estimated fair value	$ 31,862
Available-for-sale, less than 12 months, gross unrealized losses	(2,991)
Available-for-sale, 12 months or more, estimated fair value	3,084,495
Available-for-sale, 12 months or more, gross unrealized losses	(354,795)
Available-for-sale, total, estimated fair value	3,116,357
Available-for-sale, total, gross unrealized losses	(357,786)
U.S. Treasury
Available-for-sale
Available-for-sale, less than 12 months, estimated fair value	0
Available-for-sale, less than 12 months, gross unrealized losses	0
Available-for-sale, 12 months or more, estimated fair value	2,254
Available-for-sale, 12 months or more, gross unrealized losses	(31)
Available-for-sale, total, estimated fair value	2,254
Available-for-sale, total, gross unrealized losses	(31)
U.S. Government agencies
Available-for-sale
Available-for-sale, less than 12 months, estimated fair value	8,614
Available-for-sale, less than 12 months, gross unrealized losses	(39)
Available-for-sale, 12 months or more, estimated fair value	59,732
Available-for-sale, 12 months or more, gross unrealized losses	(1,954)
Available-for-sale, total, estimated fair value	68,346
Available-for-sale, total, gross unrealized losses	(1,993)
Mortgage-backed securities
Available-for-sale
Available-for-sale, less than 12 months, estimated fair value	9,182
Available-for-sale, less than 12 months, gross unrealized losses	(135)
Available-for-sale, 12 months or more, estimated fair value	1,930,105
Available-for-sale, 12 months or more, gross unrealized losses	(198,218)
Available-for-sale, total, estimated fair value	1,939,287
Available-for-sale, total, gross unrealized losses	(198,353)
State and political subdivisions
Available-for-sale
Available-for-sale, less than 12 months, estimated fair value	3,050
Available-for-sale, less than 12 months, gross unrealized losses	(163)
Available-for-sale, 12 months or more, estimated fair value	869,379
Available-for-sale, 12 months or more, gross unrealized losses	(132,378)
Available-for-sale, total, estimated fair value	872,429
Available-for-sale, total, gross unrealized losses	(132,541)
Other securities
Available-for-sale
Available-for-sale, less than 12 months, estimated fair value	11,016
Available-for-sale, less than 12 months, gross unrealized losses	(2,654)
Available-for-sale, 12 months or more, estimated fair value	223,025
Available-for-sale, 12 months or more, gross unrealized losses	(22,214)
Available-for-sale, total, estimated fair value	234,041
Available-for-sale, total, gross unrealized losses	$ (24,868)

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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