Employee Retirement Benefits - Amounts Recognized in Balance Sheet and Other Comprehensive Income and Assumptions Used (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Pension
Amounts Recognized in Balance Sheet
Accrued liabilities	$ (0.3)	$ (0.1)
Other long-term liabilities	(21.1)	(11.9)
Net amount recognized	(21.4)	(12.0)
Amounts Recognized in Accumulated Other Comprehensive Loss
Net actuarial gain (loss)	(24.0)	(15.7)
Prior service credits	0.0	0.0
Net amount recognized	$ (24.0)	$ (15.7)
Weighted‑Average Assumptions Used to Determine Projected Benefit Obligations
Discount rate	5.40%	2.70%
Average rate of increase in compensation	0.00%	0.00%
Interest credit rate	3.80%	3.80%
Postretirement
Amounts Recognized in Balance Sheet
Accrued liabilities	$ (0.1)	$ (0.1)
Other long-term liabilities	(0.7)	(0.9)
Net amount recognized	(0.8)	(1.0)
Amounts Recognized in Accumulated Other Comprehensive Loss
Net actuarial gain (loss)	0.5	0.2
Prior service credits	(0.1)	0.0
Net amount recognized	$ 0.4	$ 0.2
Weighted‑Average Assumptions Used to Determine Projected Benefit Obligations
Discount rate	5.40%	2.70%
Average rate of increase in compensation	0.00%	0.00%
Interest credit rate	0.00%	0.00%
Initial healthcare cost trend rate	6.10%	5.60%
Ultimate healthcare cost trend rate	4.00%	4.00%

Amount, after tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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Amount, after tax, of accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

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Amount, after tax, of accumulated other comprehensive (income) loss for cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan.

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Weighted average rate increase of compensation, used to determine benefit obligation of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan.

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Weighted-average interest crediting rate used to determine benefit obligation of defined benefit plan. Plan includes, but is not limited to, cash balance and other defined benefit plans with promised interest crediting rate.

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Assumed rate, for next fiscal year, based on annual change in cost of health care cost benefits used to measure expected cost of benefits covered by defined benefit postretirement plan. Factors include, but are not limited to, estimate of health care inflation, change in health care utilization or delivery pattern, technological advances, and change in health status of participant. Excludes factors for change in composition of plan population by age and dependency status.

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Ultimate trend rate for health care cost for defined benefit postretirement plan.

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Amount of liability, recognized in statement of financial position, for defined benefit pension and other postretirement plans, classified as current.

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Amount of liability, recognized in statement of financial position, for defined benefit pension and other postretirement plans.

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Amount of liability, recognized in statement of financial position, for defined benefit pension and other postretirement plans, classified as noncurrent.

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