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Share-Based Compensation and Other Employee Benefit Plans - Additional Information (Details) - USD ($) shares in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Remaining shares available for issuance (in shares) | 3,100 |  |
Increase in number of shares authorized for issuance (in shares) | $ 38,200,000 | $ 32,300,000 | $ 27,900,000
Total income tax benefit, stock-based compensation cost | $ 9,400,000 | $ 7,900,000 | $ 6,900,000
Employer discretionary contribution, percent | 0.00% | 4.00% | 0.00%
Shares allocated to the employee stock ownership plan (in shares) | 800 | 900 |
Contribution expense under employee stock ownership plan | $ 25,000,000.0 | $ 34,800,000 | $ 20,300,000
Employer Matching Contribution Tranche One |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Defined contribution plans employee contribution percentage of eligible compensation matched by employer | 5.00% |  |
Contribution plan, employer matching contribution percentage | 100.00% |  |
Restricted Stock |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Unrecognized compensation expense | $ 29,700,000 |  |
Expected weighted-average period for cost recognition (in years) | 1 year 7 months 6 days |  |
Total fair value of shares vested | $ 29,900,000 | $ 16,600,000 | $ 15,100,000
Restricted Stock | Annually |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Share-based compensation awards, vesting period | 3 years |  |
Performance Shares or Units |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Share-based compensation awards, vesting period | 36 months |  |
Unrecognized compensation expense | $ 5,400,000 |  |
Expected weighted-average period for cost recognition (in years) | 1 year 2 months 12 days |  |
Stock Options | Old National Bancorp |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Incremental expense associated with conversion of stock awards | $ 0 |  |
Outside Director Stock Compensation Program | Amended and Restated 2008 Incentive Compensation Plan |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Shares issued (in shares) | 27 | 26 | 41

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