Retirement Benefits (Assumptions Used To Determine Net Periodic Benefit Cost) (Details)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Discount rate at measurement date	3.50%	4.25%	3.50%
Expected return on plan assets	7.00%	7.00%	7.00%
Increase in future compensation	3.50%	3.50%	3.50%
Cash balance pension plan interest crediting rate	5.00%	5.00%	5.00%
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Discount rate at measurement date	3.50%	4.25%	3.50%
Expected return on plan assets	7.00%	7.00%	7.00%
Increase in future compensation	3.50%	3.50%	3.50%
Medical cost trend rate (initial)	5.00%	5.00%	5.00%
Medical cost trend rate (ultimate)	5.00%	5.00%	5.00%
Postretirement Health Coverage
Defined Benefit Plan Disclosure [Line Items]
Medical cost trend rate (initial)	3.00%
Medical cost trend rate (ultimate)	3.00%

Weighted-average interest crediting rate used to determine benefit obligation of defined benefit plan. Plan includes, but is not limited to, cash balance and other defined benefit plans with promised interest crediting rate.

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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.

+ References

+ Details

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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=118255775&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=118255775&loc=d3e2919-114920

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- Definition

Weighted average rate of compensation increase used to determine net periodic benefit cost of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan.

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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.

+ References

No definition available.

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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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+ Details

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- Definition

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

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