Retirement Benefits (Future Postretirement Health Care and Life Insurance Benefit Payments) (Details) - Postretirement Health Care And Life Insurance Benefit Plans [Member] $ in Thousands	Dec. 31, 2020 USD ($)
Pension Postretirement And Other Retirement Plans [Line Items]
Before Medicare Subsidy 2021	$ 1,046
Before Medicare Subsidy 2022	1,001
Before Medicare Subsidy 2023	957
Before Medicare Subsidy 2024	918
Before Medicare Subsidy 2025	867
Before Medicare Subsidy 2026-2030	3,733
After Medicare Subsidy, 2021	1,016
After Medicare Subsidy, 2022	971
After Medicare Subsidy, 2023	926
After Medicare Subsidy, 2024	889
After Medicare Subsidy, 2025	837
After Medicare Subsidy, 2026-2030	$ 3,595

Defined Benefit Plan Expected Future Benefit Payments After Medicare Subsidy Five Fiscal Years Thereafter

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- Definition

Defined Benefit Plan Expected Future Benefit Payments After Medicare Subsidy Next Twelve Months

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No definition available.

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- Definition

Defined Benefit Plan Expected Future Benefit Payments After Medicare Subsidy Year Five

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- Definition

Defined Benefit Plan Expected Future Benefit Payments After Medicare Subsidy Year Four

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No definition available.

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- Definition

Defined Benefit Plan Expected Future Benefit Payments After Medicare Subsidy Year Three

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No definition available.

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- Definition

Defined Benefit Plan Expected Future Benefit Payments After Medicare Subsidy Year Two

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- Definition

Pension Postretirement And Other Retirement Plans [Line Items]

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No definition available.

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- Definition

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=118255775&loc=d3e1928-114920

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- Definition

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

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- Definition

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

+ References

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- Definition

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

+ References

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- Definition

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

+ References

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- Definition

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

+ References

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