Retirement Benefits (Summary of Changes in the Fair Value of the Plans Level 3 Assets) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value of plan assets at end of year	$ 19,074
Other investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value of plan assets at beginning of year	716
Fair value of plan assets at end of year	791	$ 716
Corporate stocks
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value of plan assets at beginning of year	2,906
Fair value of plan assets at end of year	2,777	2,906
Significant Unobservable Inputs (Level 3)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value of plan assets at beginning of year	683	334
Purchases	20	17
Sales	(12)	(14)
Unrealized Gain/ (Loss)	25	72
Realized Gain/ (Loss)	1	1
Exchange Rate Impact	55	(9)
Transfers in/(out) and Other	2	282
Fair value of plan assets at end of year	774	683
Significant Unobservable Inputs (Level 3) \| Other investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value of plan assets at beginning of year	682
Purchases	20
Sales	(12)
Unrealized Gain/ (Loss)	25
Realized Gain/ (Loss)	1
Exchange Rate Impact	55
Transfers in/(out) and Other	2
Fair value of plan assets at end of year	773	682
Significant Unobservable Inputs (Level 3) \| Other investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value of plan assets at beginning of year	682	333
Purchases		17
Sales		(14)
Unrealized Gain/ (Loss)		72
Realized Gain/ (Loss)		1
Exchange Rate Impact		(9)
Transfers in/(out) and Other		282
Fair value of plan assets at end of year	771	682
Significant Unobservable Inputs (Level 3) \| Corporate stocks
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value of plan assets at beginning of year	1	1
Purchases	0	0
Sales	0	0
Unrealized Gain/ (Loss)	0	0
Realized Gain/ (Loss)	0	0
Exchange Rate Impact	0	0
Transfers in/(out) and Other	0	0
Fair value of plan assets at end of year	$ 1	$ 1

Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Recurring Basis Asset Translation Adjustment

No definition available.

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- Definition

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from actual return (loss) on assets sold.

+ References

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- Definition

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from actual return (loss) on assets still held.

+ References

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- Definition

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
-Section 50
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- Definition

Amount, measured using unobservable input, of decrease in plan asset of defined benefit plan from sale.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(02)(B)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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- Definition

Amount, measured using unobservable input, of increase in plan asset of defined benefit plan from purchase.

+ References

+ Details

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- Definition

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan, for assets transferred into (out of) Level 3 of fair value hierarchy. Includes, but is not limited to, transfer due to change in observability of significant inputs.

+ References

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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