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Investment Securities (Narrative) (Details) |  | 3 Months Ended | 9 Months Ended |
--- | --- | --- | --- | ---
Dec. 13, 2024 USD ($) | Sep. 30, 2025 USD ($) Security | Sep. 30, 2024 USD ($) | Sep. 30, 2025 USD ($) Security | Sep. 30, 2024 USD ($) | Dec. 31, 2024 USD ($) Security
Schedule Of Investments [Line Items] |  |  |  |  |  |
Securities pledged as collateral |  | $ 939,700,000 |  | $ 939,700,000 |  | $ 828,800,000
Proceeds from Sale of Debt Securities, Available-for-Sale |  | $ 29,186,000 | $ 0 | $ 94,142,000 | $ 0 |
Proceeds from sales used to fund losses | $ 653,500,000 |  |  |  |  |
Pre-tax loss | 100,200,000 |  |  |  |  |
Number of security positions, unrealized loss position | Security |  | 52 |  | 52 |  | 76
Number of security positions, unrealized loss position for more than 12 months | Security |  | 37 |  | 37 |  | 37
Securities, 12 months or longer, Fair Value |  | $ 206,249,000 |  | $ 206,249,000 |  | $ 176,627,000
Securities, 12 months or longer, Unrealized Losses |  | $ 45,753,000 |  | $ 45,753,000 |  | $ 53,433,000
Number of security positions, unrealized loss position for less than 12 months | Security |  | 15 |  | 15 |  | 39
Securities, Less than 12 months, Fair Value |  | $ 148,933,000 |  | $ 148,933,000 |  | $ 681,223,000
Securities, Less than 12 months, Unrealized Losses |  | 2,684,000 |  | 2,684,000 |  | 9,046,000
Available for sale securities, allowance for credit loss |  | 0 |  | 0 |  | 0
Securities held to maturity, Amortized Cost |  | 87,627,000 |  | 87,627,000 |  | 116,003,000
Internally rated held-to-maturity securities |  | $ 4,700,000 |  | $ 4,700,000 |  | $ 3,400,000
Investment, Type [Extensible Enumeration] |  | Municipal Bonds [Member] |  | Municipal Bonds [Member] |  | Municipal Bonds [Member]
Investment securities, past due |  | $ 4,590,423,000 |  | $ 4,590,423,000 |  | $ 4,479,204,000
Higher-Yielding Agency Wrapped Investments [Member] |  |  |  |  |  |
Schedule Of Investments [Line Items] |  |  |  |  |  |
Net proceeds from sale of securities to purchase investment | $ 642,600,000 |  |  |  |  |
Total Past Due [Member] |  |  |  |  |  |
Schedule Of Investments [Line Items] |  |  |  |  |  |
Investment securities, past due |  | 19,222,000 |  | 19,222,000 |  | 22,030,000
Municipal Bonds [Member] |  |  |  |  |  |
Schedule Of Investments [Line Items] |  |  |  |  |  |
Securities held to maturity, Amortized Cost |  | 29,100,000 |  | 29,100,000 |  | 41,900,000
Available for Sale Securities [Member] |  |  |  |  |  |
Schedule Of Investments [Line Items] |  |  |  |  |  |
Accrued interest receivable |  | 3,500,000 |  | 3,500,000 |  | 3,400,000
Held To Maturity Investment Securities [Member] |  |  |  |  |  |
Schedule Of Investments [Line Items] |  |  |  |  |  |
Accrued interest receivable |  | 447,000 |  | 447,000 |  | 456,000
Held To Maturity Investment Securities [Member] | Total Past Due [Member] |  |  |  |  |  |
Schedule Of Investments [Line Items] |  |  |  |  |  |
Investment securities, past due |  | 0 |  | 0 |  | $ 0
Held To Maturity Investment Securities [Member] | Maximum [Member] |  |  |  |  |  |
Schedule Of Investments [Line Items] |  |  |  |  |  |
Provision for credit loss |  | $ 1,000 | $ 1,000 | $ 1,000 | $ 1,000 |

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