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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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