Retirement Plans and Other Postretirement Benefits - Defined Benefit Plan and Supplemental Retirement Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan
Change in benefit obligation:
Projected benefit obligation at beginning of year	$ 22.2	$ 24.3	$ 24.8
Service cost	0.7	0.6	0.7
Interest cost	0.5	0.5	0.7
Plan amendments	0.0	0.0	0.0
Actuarial loss (gain)	(3.7)	(0.6)	1.0
Benefits paid	(2.5)	(2.6)	(1.5)
Settlements	0.0	0.0	(1.4)
Projected benefit obligation at end of year	17.2	22.2	24.3
Change in plan assets:
Fair value of plan assets at beginning of year	19.8	22.0	23.2
Actual return on plan assets	(3.2)	1.0	2.3
Employer contributions	0.0	0.0	0.0
Benefits paid	(2.5)	(2.6)	(1.5)
Expenses paid	(0.5)	(0.6)	(0.6)
Settlements		0.0	(1.4)
Fair value of plan assets at end of year	13.6	19.8	22.0
Funded status	(3.6)	(2.4)	(2.3)
Prepaid (accrued) benefit expense	4.1	4.9	5.5
Total amount recognized in Consolidated Balance Sheets, all in Other liabilities	(3.6)	(2.4)	(2.3)
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Prior service cost	0.0	0.0	0.0
Net actuarial loss	(7.9)	(7.3)	(7.8)
Total amount recognized in AOCI	(7.9)	(7.3)	(7.8)
Information for pension plans with an accumulated benefit obligation greater than plan assets:
Projected benefit obligation	17.2	22.2	24.3
Accumulated benefit obligation	17.2	22.2	24.3
Fair value of plan assets	13.6	19.8	22.0
Supplemental Defined Benefit Plans
Change in benefit obligation:
Projected benefit obligation at beginning of year	14.5	15.7	15.2
Service cost	0.0	0.0	0.0
Interest cost	0.3	0.3	0.5
Plan amendments	0.0	0.0	0.0
Actuarial loss (gain)	(2.1)	(0.2)	1.3
Benefits paid	(1.3)	(1.3)	(1.3)
Settlements	0.0	0.0	0.0
Projected benefit obligation at end of year	11.4	14.5	15.7
Change in plan assets:
Fair value of plan assets at beginning of year	0.0	0.0	0.0
Actual return on plan assets		0.0	0.0
Employer contributions	1.3	1.3	1.3
Benefits paid	(1.3)	(1.3)	(1.3)
Expenses paid	0.0	0.0	0.0
Settlements	0.0	0.0	0.0
Fair value of plan assets at end of year	0.0	0.0	0.0
Funded status	(11.4)	(14.5)	(15.7)
Prepaid (accrued) benefit expense	(8.1)	8.7	(9.3)
Total amount recognized in Consolidated Balance Sheets, all in Other liabilities	(11.4)	(14.5)	(15.7)
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Prior service cost	0.0	0.0	0.0
Net actuarial loss	(3.3)	(6.5)	(6.4)
Total amount recognized in AOCI	(3.3)	(6.5)	(6.4)
Information for pension plans with an accumulated benefit obligation greater than plan assets:
Projected benefit obligation	11.4	14.5	15.7
Accumulated benefit obligation	11.4	14.5	15.7
Fair value of plan assets	$ 0.0	$ 0.0	$ 0.0