Pension and Postretirement Plans - Amounts Recognized in Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Other noncurrent assets	$ (78.0)	$ (58.9)
Pension and postretirement benefit obligations	127.9	138.9
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Other noncurrent assets	(2.1)	0.0
Accrued payroll and benefits	1.5	1.5
Pension and postretirement benefit obligations	36.5	47.4
Total	35.9	48.9
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Prior service cost, net of tax of ($0.4), ($0.2)	0.0	0.0
Actuarial gain (loss), net of tax of ($0.8), ($1.6), $8.9, $10.2	5.8	(5.1)
Total	5.8	(5.1)
Actuarial gain (loss), tax	(0.8)	(1.6)
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Other noncurrent assets	0.0	0.0
Accrued payroll and benefits	7.9	8.1
Pension and postretirement benefit obligations	91.1	91.1
Total	99.0	99.2
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Prior service cost, net of tax of ($0.4), ($0.2)	(1.2)	(0.6)
Actuarial gain (loss), net of tax of ($0.8), ($1.6), $8.9, $10.2	28.6	32.8
Total	27.4	32.2
Prior service costs, tax	0.4	(0.2)
Actuarial gain (loss), tax	$ 8.9	$ 10.2