Postretirement Health Care and Life Insurance Benefits - Assumptions Used to Determine the Benefit Obligations and Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract]
Increase (Decrease) in Obligation, Other Postretirement Benefits	$ (109.3)	$ (108.2)	$ (12.1)
Postretirement Health Care and Life Insurance Benefits
Weighted-average assumptions used to determine benefit obligations
Discount rate	5.70%	2.84%
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate	2.84%	2.55%	3.40%
Expected long-term return on plan assets (pretax)	5.75%	5.75%	7.00%
Postretirement Health Care and Life Insurance Benefits \| Maximum
Weighted-average assumptions used to determine net periodic benefit cost
Expected long-term return on plan assets (pretax)	5.75%
Pre-Medicare
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract]
Health care cost trend rate assumed for next year	7.00%	6.00%
Rate to which the cost trend is assumed to decline (the ultimate trend rate)	4.75%	4.75%
Post-Medicare
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract]
Health care cost trend rate assumed for next year	6.75%	5.75%
Rate to which the cost trend is assumed to decline (the ultimate trend rate)	4.75%	4.75%

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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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- Definition

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

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- Definition

Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

+ 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 (k)(3)
-URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e2919-114920

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- Definition

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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- Definition

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

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- Definition

Amount of increase (decrease) in obligation for other postretirement benefits. Includes, but is not limited to, defined benefit and defined contribution plans. Excludes pension benefits.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585

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