Retirement Benefits - Narrative - Plan Assumptions (Details) - Participant	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return on assets (percentage)	7.00%	7.00%	7.00%
Medical and Life Insurance Benefits
Defined Benefit Plan Disclosure [Line Items]
Initial healthcare trend rate (pre 65/post 65) (percentage)	6.25%	6.50%
Number of participants	65
Number of years until rate reaches ultimate trend rate	7 years
Ultimate healthcare trend rate (percentage)	4.50%	4.50%

Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Ultimate Health Care Cost Trend Rate

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- Definition

Defined Benefit Plan, Benefit Obligation, Health Care Cost Trend Rate Assumed, Next Fiscal Year

+ References

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- Definition

Defined Benefit Plan, Duration Until Rate Reaches Ultimate Trend Rate

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- Definition

Number Of Participants

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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

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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