Stock-Based Compensation (Schedule of Unrecognized Compensation Costs and Amortization Periods) (Details) $ in Millions	12 Months Ended
Dec. 31, 2020 USD ($)
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award
Stock options	$ 15
Weighted-Average Service Years	1 year 3 months 18 days
Restricted share units
Share-based Compensation Arrangement by Share-based Payment Award
Total remaining unrecognized compensation costs, nonvested awards other than options	$ 12
Weighted-Average Service Years	1 year 6 months
Performance-based restricted share units
Share-based Compensation Arrangement by Share-based Payment Award
Total remaining unrecognized compensation costs, nonvested awards other than options	$ 82
Weighted-Average Service Years	1 year 9 months 18 days

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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