Share-based Incentive Compensation Plans - Compensation Cost (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	$ 38	$ 36
Income tax benefit	19	1
After-tax share-based compensation expense	19	35
Restricted Stock Unit (RSU) awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	18	17
Performance Stock Unit (PSU) awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	18	17
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	$ 2	$ 2

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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