Pension And Postretirement Benefits (Accumulated Benefit Obligations In Excess Of Plan Assets) (Details) - Supplemental Retirement Plans [Member] - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Supplemental retirement plan - projected benefit obligation	$ (2,344)	$ (2,378)
Supplemental retirement plan - Accumulated benefit obligation	(2,285)	(2,314)
Supplemental retirement plan - Fair value of plan assets	$ 0	$ 0

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- Definition

Amount of projected benefit obligation for defined benefit pension plan with accumulated benefit obligation in excess of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=77993564&loc=d3e4179-114921

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- Definition

Amount of benefit obligation for defined benefit plan with benefit obligation in excess of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2417-114920

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- Definition

Fair value of plan assets for defined benefit plan with benefit obligation in excess of plan assets.

+ References

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