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Investment Securities - Additional Information (Details) | 12 Months Ended
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Dec. 31, 2023 USD ($) security | Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($)
Summary of Investment Holdings [Line Items] |  |  |
Securities pledged to secure public and other funds, carrying value | $ 8,400,000,000 | $ 6,100,000,000 |
Transfers from available-for-sale to held-to-maturity | 127,600,000 | 148,900,000 |
Allowance for credit losses for available-for-sale debt securities | $ 0 | $ 0 |
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration] | Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest | Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest |
Allowance for securities held-to-maturity | $ (150,000) | $ (150,000) |
Accrued interest receivable | $ 50,300,000 | 50,900,000 |
Number of securities in security portfolio | security | 2,920 |  |
Number of securities in unrealized loss position | security | 2,588 |  |
Equity securities, at fair value | $ 80,372,000 | 52,507,000 |
(Losses) gains on equity securities | 21,500,000 | (4,900,000) | $ 200,000
Downward adjustments on equity securities without readily determinable fair value | 0 | 0 | 0
Impairments on equity securities without readily determinable fair value | 0 | 0 | $ 0
Other Assets |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Equity securities without readily determinable fair value | 449,300,000 | $ 396,800,000 |
Other Assets | Partnership Interest |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Equity securities without readily determinable fair value | 252,200,000 |  |
Other Assets | Initiatives in Low-to-Moderate Income Neighborhoods |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Equity securities without readily determinable fair value | 197,100,000 |  |
Indiana |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Investment securities issued by states and political subdivisions, market value | $ 600,900,000 |  |
State and political subdivision investment, equity percentage | 10.80% |  |
Percentage of municipal bonds rated A or better | 99.60% |  |
Percentage of non rated local interest bonds | 0.40% |  |

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