Investment Securities - Securities With Unrealized Losses (Details) $ in Thousands	Sep. 30, 2022 USD ($)
Debt Securities, Available-for-sale [Line Items]
Available-for-sale, less than 12 months, estimated fair value	$ 1,983,590
Available-for-sale, less than 12 months, gross unrealized losses	(172,554)
Available-for-sale, 12 months or more, estimated fair value	1,895,108
Available-for-sale, 12 months or more, gross unrealized losses	(374,429)
Available-for-sale, total, estimated fair value	3,878,698
Available-for-sale, total, gross unrealized losses	(546,983)
U.S. Treasury
Debt Securities, Available-for-sale [Line Items]
Available-for-sale, less than 12 months, estimated fair value	2,191
Available-for-sale, less than 12 months, gross unrealized losses	(59)
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	2,191
Available-for-sale, total, gross unrealized losses	(59)
U.S. Government agencies
Debt Securities, Available-for-sale [Line Items]
Available-for-sale, less than 12 months, estimated fair value	116,968
Available-for-sale, less than 12 months, gross unrealized losses	(5,120)
Available-for-sale, 12 months or more, estimated fair value	53,942
Available-for-sale, 12 months or more, gross unrealized losses	(2,334)
Available-for-sale, total, estimated fair value	170,910
Available-for-sale, total, gross unrealized losses	(7,454)
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale, less than 12 months, estimated fair value	1,115,220
Available-for-sale, less than 12 months, gross unrealized losses	(73,690)
Available-for-sale, 12 months or more, estimated fair value	1,545,776
Available-for-sale, 12 months or more, gross unrealized losses	(215,849)
Available-for-sale, total, estimated fair value	2,660,996
Available-for-sale, total, gross unrealized losses	(289,539)
State and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Available-for-sale, less than 12 months, estimated fair value	536,510
Available-for-sale, less than 12 months, gross unrealized losses	(79,426)
Available-for-sale, 12 months or more, estimated fair value	259,147
Available-for-sale, 12 months or more, gross unrealized losses	(152,665)
Available-for-sale, total, estimated fair value	795,657
Available-for-sale, total, gross unrealized losses	(232,091)
Other securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale, less than 12 months, estimated fair value	212,701
Available-for-sale, less than 12 months, gross unrealized losses	(14,259)
Available-for-sale, 12 months or more, estimated fair value	36,243
Available-for-sale, 12 months or more, gross unrealized losses	(3,581)
Available-for-sale, total, estimated fair value	248,944
Available-for-sale, total, gross unrealized losses	$ (17,840)

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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
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