Share-Based Compensation - Schedule of Share-Based Compensation (Details) - USD ($) $ in Millions  | 
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2019  | 
Sep. 30, 2018  | 
Sep. 30, 2019  | 
Sep. 30, 2018  | 
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Total share-based compensation | $ 35 | $ 38 | $ 101 | $ 109 | 
| Capitalized share-based compensation | (2) | (7) | (7) | (20) | 
| Total share-based compensation expense | 33 | 31 | 94 | 89 | 
| Tax benefit associated with share-based compensation expense | 2 | 1 | 3 | 3 | 
| Equity Awards [Member] | ||||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Total share-based compensation | 33 | 25 | 94 | 64 | 
| Liability Awards [Member] | ||||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Total share-based compensation | $ 2 | $ 13 | $ 7 | $ 45 | 
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- Definition Amount of expense for award under share-based payment arrangement. Excludes amount capitalized. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Amount of cost capitalized for award under share-based payment arrangement. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Amount of tax benefit for recognition of expense of award under share-based payment arrangement. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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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. No definition available. 
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- Definition Amount of cost expensed and capitalized for award under share-based payment arrangement. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Details 
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- Details 
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