Stock-Based Compensation (Summary of Stock Awards Outstanding) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
RSU awards
Schedule Of Shares Awarded [Abstract]
Shares granted (in thousands)	498	571	649
Fair value (in millions)	$ 50	$ 51	$ 49
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding at beginning of period (in shares)	1,010
Granted (in shares)	498	571	649
Vested (in shares)	(532)
Forfeited (in shares)	(37)
Outstanding at end of period (in shares)	939	1,010
Stock awards expected to vest (in shares)	898
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Weighted average fair value at beginning of period (usd per share)	$ 83
Granted (usd per share)	100
Vested (usd per share)	82
Forfeited (usd per share)	92
Weighted average fair value at end of period (usd per share)	93	$ 83
Weighted average fair value of awards expected to vest (usd per share)	$ 93
Performance awards
Schedule Of Shares Awarded [Abstract]
Shares granted (in thousands)	319	320	372
Fair value (in millions)	$ 34	$ 27	$ 27
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding at beginning of period (in shares)	1,109
Granted (in shares)	319	320	372
Vested (in shares)	(448)
Forfeited (in shares)	(18)
Outstanding at end of period (in shares)	962	1,109
Stock awards expected to vest (in shares)	937
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Weighted average fair value at beginning of period (usd per share)	$ 80
Granted (usd per share)	105
Vested (usd per share)	81
Forfeited (usd per share)	88
Weighted average fair value at end of period (usd per share)	87	$ 80
Weighted average fair value of awards expected to vest (usd per share)	$ 87

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The number of equity-based payment instruments, excluding stock (or unit) options, that are expected to vest.

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No definition available.

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The weighted average fair value of expected to vest awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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Share Based Compensation Grants In Period Fair Value

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No definition available.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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