Income Taxes - Schedule of Income Tax Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Current:
Federal	$ 61.5	$ 38.1	$ 46.1
State	17.0	9.7	12.8
Total current	78.5	47.8	58.9
Deferred:
Federal	9.0	17.8	16.0
State	2.1	2.9	4.4
Total income tax expense	89.6	68.5	79.3
Operating Loss Carryforwards [Line Items]
Other adjustments		0.6	0.3
Federal tax credits(3)		(0.3)	(0.2)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Amount	3.3
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount		2.5	2.0
Total deferred	11.1	20.7	20.4
Tax expense at the statutory tax rate	82.3	61.9	70.7
State income tax, net of federal income tax benefit(2)	15.1	10.0	13.6
Provision for income tax	89.6	68.5	79.3
Tax-exempt interest income, net	(4.2)	(7.4)	(8.1)
Effective Income Tax Rate Reconciliation, bank owned life insurance income	$ (3.3)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Percent	0.80%
Other, net(4)	$ (1.4)	$ 1.2	$ 1.0
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent	(0.50%)
Effective Income Tax Rate Reconciliation, Percent	23.00%
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, Amount	$ (2.2)
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%)