Retirement Plans (Amounts Deferred In AOCL) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Pension Benefits
Compensation And Retirement Disclosure Line Items
Net actuarial loss (gain)	$ 5,752	$ 5,276
Prior service (credit) cost	(93)	(73)
Total amount recognized in AOCI, pre-tax	5,659	5,203
Other Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Net actuarial loss (gain)	(12)	(9)
Prior service (credit) cost	12	12
Total amount recognized in AOCI, pre-tax	$ 0	$ 3

Compensation And Retirement Disclosure Line Items

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- Definition

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

+ References

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-Publisher FASB
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-Topic 220
-SubTopic 10
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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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
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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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
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