Retirement Plans (Schedule Of Pre-Tax Amounts Recognized In Accumulated Other Comprehensive Income/(Loss)) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Prior service (cost)/credit	$ 84	$ 95
Net actuarial loss	(1,903)	(1,605)
Total pre-tax amounts recognized in accumulated other comprehensive income/(loss)	(1,819)	(1,510)
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service (cost)/credit
Net actuarial loss	(1,805)	(1,501)
Total pre-tax amounts recognized in accumulated other comprehensive income/(loss)	(1,805)	(1,501)
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service (cost)/credit	84	95
Net actuarial loss	(98)	(104)
Total pre-tax amounts recognized in accumulated other comprehensive income/(loss)	$ (14)	$ (9)

Amount, before tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
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-Section 50
-Paragraph 1
-Subparagraph (j)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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- Definition

Amount, before tax, of accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

+ 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 (j)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669686-108580

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- Definition

Amount, before tax, of accumulated other comprehensive (income) loss for cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

+ References

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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

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