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Investment Securities - Securities With Unrealized Losses (Details) $ in Thousands | Sep. 30, 2021 USD ($)
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Debt Securities, Available-for-sale [Line Items] |
Available-for-sale, less than 12 months, estimated fair value | $ 3,659,613
Available-for-sale, less than 12 months, gross unrealized losses | (51,166)
Available-for-sale, 12 months or more, estimated fair value | 181,287
Available-for-sale, 12 months or more, gross unrealized losses | (5,955)
Available-for-sale, total, estimated fair value | 3,840,900
Available-for-sale, total, gross unrealized losses | (57,121)
U.S. Government agencies |
Debt Securities, Available-for-sale [Line Items] |
Available-for-sale, less than 12 months, estimated fair value | 190,275
Available-for-sale, less than 12 months, gross unrealized losses | (3,759)
Available-for-sale, 12 months or more, estimated fair value | 111,662
Available-for-sale, 12 months or more, gross unrealized losses | (3,946)
Available-for-sale, total, estimated fair value | 301,937
Available-for-sale, total, gross unrealized losses | (7,705)
Mortgage-backed securities |
Debt Securities, Available-for-sale [Line Items] |
Available-for-sale, less than 12 months, estimated fair value | 2,342,244
Available-for-sale, less than 12 months, gross unrealized losses | (27,380)
Available-for-sale, 12 months or more, estimated fair value | 46,253
Available-for-sale, 12 months or more, gross unrealized losses | (722)
Available-for-sale, total, estimated fair value | 2,388,497
Available-for-sale, total, gross unrealized losses | (28,102)
State and political subdivisions |
Debt Securities, Available-for-sale [Line Items] |
Available-for-sale, less than 12 months, estimated fair value | 969,120
Available-for-sale, less than 12 months, gross unrealized losses | (16,056)
Available-for-sale, 12 months or more, estimated fair value | 23,372
Available-for-sale, 12 months or more, gross unrealized losses | (1,287)
Available-for-sale, total, estimated fair value | 992,492
Available-for-sale, total, gross unrealized losses | (17,343)
Other securities |
Debt Securities, Available-for-sale [Line Items] |
Available-for-sale, less than 12 months, estimated fair value | 157,974
Available-for-sale, less than 12 months, gross unrealized losses | (3,971)
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 | 157,974
Available-for-sale, total, gross unrealized losses | $ (3,971)

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