Income Taxes - Reconciliation of Tax Expense at Effective Tax Rate (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Income Tax Expense, Continuing Operations Income Tax Reconciliation [Abstract]
Tax expense at the statutory tax rate	$ 82.3	$ 61.9	$ 70.7
Increase (decrease) in tax resulting from:
Tax-exempt interest income, net	(4.2)	(7.4)	(8.1)
State income tax, net of federal income tax benefit(2)	15.1	10.0	13.6
Other adjustments		0.6	0.3
Federal tax credits(3)		(0.3)	(0.2)
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount		2.5	2.0
Other, net(4)	(1.4)	1.2	1.0
Effective Income Tax Rate Reconciliation, Tax Credit, Amount	(2.2)
Effective Income Tax Rate Reconciliation, bank owned life insurance income	(3.3)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Amount	3.3
Total income tax expense	$ 89.6	$ 68.5	$ 79.3
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent	3.90%
Effective Income Tax Rate Reconciliation, Tax Credit, Percent	(0.30%)
Effective Income Tax Rate Reconciliation, Tax Exempt Income, Percent	(1.10%)
Effective Income Tax Rate Reconciliation, bank owned life insurance income, percent	(0.80%)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Percent	0.80%
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent	(0.50%)
Effective Income Tax Rate Reconciliation, Percent	23.00%