Share-Based Compensation - Narrative (Details) - USD ($) shares in Thousands, $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 84	$ 87	$ 286	$ 121
Unrecognized compensation cost	$ 343		$ 343
Weighted-average period unrecognized compensation cost will be recognized			2 years
Share-based awards, stock options, exercised (in shares)			2,195
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based awards, stock options, exercised (in shares)			2,200	3,300

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

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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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.

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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.

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Number of share options (or share units) exercised during the current period.

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