Postretirement Benefits Other Than Pensions - Benefit Payments Net of Expected Medicare Part D Subsidy (Details) - Other Postretirement Benefit Plan, Defined Benefit $ in Millions	Dec. 31, 2020 USD ($)
Estimated Benefit Payments Excluding Medicare Part D Subsidy
2020	$ 1.3
2021	1.3
2022	1.3
2023	1.3
2024	1.2
2026-2030	4.6
Expected Medicare Part D Subsidy
2020	0.0
2021	0.0
2022	0.0
2023	0.0
2024	0.0
2026-2030	0.0
Net Estimated Benefit Payments
2020	1.3
2021	1.3
2022	1.3
2023	1.3
2024	1.2
2026-2030	$ 4.6

Defined Benefit Plan, Expected Future Benefit Payments Excluding Prescription Drug Subsidy Receipts, Next Twelve Months

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Defined Benefit Plan, Expected Future Benefit Payments Excluding Prescription Drug Subsidy Receipts, after Year Five

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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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