Employee Retirement Plans (Changes in Fair Value of Level 3 Assets for Defined Benefit Plans) (Details) - Pension Benefits [Member] - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	$ 3,671	$ 3,239
Fair value of plan assets at end of year	4,173	3,671
United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	3,153	2,742
Fair value of plan assets at end of year	3,575	3,153
International [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	518	497
Fair value of plan assets at end of year	598	518
Private Equity Funds [Member] \| United States [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	64	82
Actual return on plan assets relating to assets still held at the reporting date	4
Transfers in and/or out of level 3	(17)	(18)
Fair value of plan assets at end of year	51	64
Real Estate [Member] \| United States [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	145	148
Actual return on plan assets relating to assets still held at the reporting date		2
Transfers in and/or out of level 3	(5)	(5)
Fair value of plan assets at end of year	140	145
Collateralized Mortgage Backed Securities [Member] \| International [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	21	22
Transfers in and/or out of level 3	(1)	(1)
Fair value of plan assets at end of year	20	21
Insurance Contracts [Member] \| International [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	2	2
Transfers in and/or out of level 3	1
Fair value of plan assets at end of year	$ 3	$ 2

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

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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

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

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-Publisher FASB
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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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