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Income Taxes (Details) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Jun. 30, 2026 | Jun. 30, 2025 | Dec. 31, 2025
Income Tax Contingency [Line Items] |  |  |
Effective tax rate (as a percent) | 21.60% | 21.40% |
Combined federal and state statutory tax rate (as a percent) | 24.20% |  |
Valuation allowance | $ 5.0 |  | $ 5.0
First Niagara Bank, N.A. |  |  |
Income Tax Contingency [Line Items] |  |  |
Allocated bad debt deductions | 92.0 |  |
Key Corp |  |  |
Income Tax Contingency [Line Items] |  |  |
Unrecognized tax benefits | 3.0 |  |
Location, Statement of Financial Position, Balance [Axis]: us-gaap:OtherAssets |  |  |
Income Tax Contingency [Line Items] |  |  |
Net deferred tax assets | $ 1,200.0 |  | $ 1,200.0

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