Postretirement Health Care and Life Insurance Benefits - Estimated Future Benefit Payments (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period (in years)	2 years 10 months 24 days	3 years 10 months 24 days
Postretirement Health Care and Life Insurance Benefits
Defined Benefit Plan Disclosure [Line Items]
2022	$ 28.9
2023	25.8
2024	24.3
2025	22.7
2026	20.8
Years 2027-2031	$ 81.5
Average remaining service period (in years)	14 years 2 months 12 days
Postretirement Health Care and Life Insurance Benefits \| Retirement Plan Amendment One
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period (in years)	3 years 10 months 24 days	4 years 10 months 24 days
Postretirement Health Care and Life Insurance Benefits \| Retirement Plan Amendment Two
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period (in years)	9 years 6 months	10 years 6 months

Defined Benefit Plan, Average Remaining Service Period

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- Definition

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

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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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