Investment Securities - Securities With Unrealized Losses (Details) $ in Thousands	Jun. 30, 2022 USD ($)
Debt Securities, Available-for-sale [Line Items]
Available-for-sale, less than 12 months, estimated fair value	$ 3,104,616
Available-for-sale, less than 12 months, gross unrealized losses	(255,386)
Available-for-sale, 12 months or more, estimated fair value	1,095,158
Available-for-sale, 12 months or more, gross unrealized losses	(134,651)
Available-for-sale, total, estimated fair value	4,199,774
Available-for-sale, total, gross unrealized losses	(390,037)
U.S. Treasury
Debt Securities, Available-for-sale [Line Items]
Available-for-sale, less than 12 months, estimated fair value	1,441
Available-for-sale, less than 12 months, gross unrealized losses	(6)
Available-for-sale, 12 months or more, estimated fair value	0
Available-for-sale, 12 months or more, gross unrealized losses	0
Available-for-sale, total, estimated fair value	1,441
Available-for-sale, total, gross unrealized losses	(6)
U.S. Government agencies
Debt Securities, Available-for-sale [Line Items]
Available-for-sale, less than 12 months, estimated fair value	110,444
Available-for-sale, less than 12 months, gross unrealized losses	(3,226)
Available-for-sale, 12 months or more, estimated fair value	50,341
Available-for-sale, 12 months or more, gross unrealized losses	(1,308)
Available-for-sale, total, estimated fair value	160,785
Available-for-sale, total, gross unrealized losses	(4,534)
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale, less than 12 months, estimated fair value	2,082,115
Available-for-sale, less than 12 months, gross unrealized losses	(125,904)
Available-for-sale, 12 months or more, estimated fair value	880,256
Available-for-sale, 12 months or more, gross unrealized losses	(60,685)
Available-for-sale, total, estimated fair value	2,962,371
Available-for-sale, total, gross unrealized losses	(186,589)
State and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Available-for-sale, less than 12 months, estimated fair value	714,786
Available-for-sale, less than 12 months, gross unrealized losses	(117,930)
Available-for-sale, 12 months or more, estimated fair value	150,324
Available-for-sale, 12 months or more, gross unrealized losses	(70,593)
Available-for-sale, total, estimated fair value	865,110
Available-for-sale, total, gross unrealized losses	(188,523)
Other securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale, less than 12 months, estimated fair value	195,830
Available-for-sale, less than 12 months, gross unrealized losses	(8,320)
Available-for-sale, 12 months or more, estimated fair value	14,237
Available-for-sale, 12 months or more, gross unrealized losses	(2,065)
Available-for-sale, total, estimated fair value	210,067
Available-for-sale, total, gross unrealized losses	$ (10,385)

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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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