Retirement Benefits - Schedule of Estimated Future Benefit Payments (Details) $ in Millions	Dec. 31, 2021 USD ($)
Pension Benefits
Expected Benefit Payments
2022	$ 104.7
2023	101.5
2024	98.1
2025	94.5
2026	90.7
Years 2027 - 2031	395.1
Medical and Life Insurance Benefits
Expected Benefit Payments
2022	2.7
2023	2.4
2024	2.1
2025	1.9
2026	1.7
Years 2027 - 2031	6.0
Gross Benefit Payments
2022	2.8
2023	2.5
2024	2.2
2025	2.0
2026	1.7
Years 2027 - 2031	6.1
Medicare D Subsidy
2022	0.1
2023	0.1
2024	0.1
2025	0.1
2026	0.0
Years 2027 - 2031	$ 0.1

Defined Benefit Plan, Expected Future Gross Benefit Payment

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Gross Projected Postretirement Benefits Payments Before Medicare Part D Subsidies Next Twelve Months

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Gross Projected Postretirement Benefits Payments Before Medicare Part D Subsidies Year Five

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Gross Projected Postretirement Benefits Payments Before Medicare Part D Subsidies Year Four

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Gross Projected Postretirement Benefits Payments Before Medicare Part D Subsidies Year Three

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Amount of benefit for defined benefit plan expected to be paid in five fiscal years after fifth fiscal year following current fiscal year.

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Amount of benefit for defined benefit plan expected to be paid in next fiscal year following current fiscal year.

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Amount of benefit for defined benefit plan expected to be paid in fifth fiscal year following current fiscal year.

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Amount of benefit for defined benefit plan expected to be paid in fourth fiscal year following current fiscal year.

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Amount of benefit for defined benefit plan expected to be paid in third fiscal year following current fiscal year.

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Amount of benefit for defined benefit plan expected to be paid in second fiscal year following current fiscal year.

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Amount of prescription drug subsidy receipt expected in third fiscal year following current fiscal year.

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