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Investment Securities - Additional Information (Details) | 9 Months Ended |
--- | --- | ---
Sep. 30, 2023 USD ($) Security | Dec. 31, 2022 USD ($) Securities Security
Schedule Of Available For Sale Securities [Line Items] |  |
Equity securities, at fair value | $ 3,932,000 | $ 311,000
Tax rate used to calculate tax-equivalent yields (in hundredths) | 21.00% |
Percentage investment book value exceeds stockholders' equity (in hundredths) | 10.00% |
Debt securities, available-for-sale, restricted | $ 860,000,000 | 770,000,000
Available-for-sale, 12 months or longer, Fair Value | 1,039,657,000 | 677,083,000
12 months or longer, unrealized losses | $ 250,785,000 | $ 143,282,000
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Number of securities in unrealized loss positions | Security | 40 | 16
Available-for-sale, 12 months or longer, Fair Value | $ 208,428,000 | $ 163,520,000
12 months or longer, unrealized losses | $ 33,681,000 | $ 28,914,000
Held-to-maturity, securities in unrealized loss positions, qualitative disclosure, number of positions | Securities |  | 0
Obligations of States and Political Subdivisions |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Number of securities in unrealized loss positions | Security | 235 | 36
Available-for-sale, 12 months or longer, Fair Value | $ 219,250,000 | $ 45,419,000
12 months or longer, unrealized losses | $ 72,090,000 | $ 16,624,000
Mortgage-backed Securities: GSE Residential |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Number of securities in unrealized loss positions | Security | 278 | 91
Available-for-sale, 12 months or longer, Fair Value | $ 555,338,000 | $ 461,446,000
12 months or longer, unrealized losses | $ 139,349,000 | $ 96,900,000
Other Securities |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Number of securities in unrealized loss positions | Security | 43 | 5
Available-for-sale, 12 months or longer, Fair Value | $ 56,641,000 | $ 6,698,000
12 months or longer, unrealized losses | $ 5,665,000 | $ 844,000

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