| Share-Based Compensation - Schedule of Share-Based Compensation (Details) - USD ($) $ in Millions | 12 Months Ended | ||
|---|---|---|---|
| Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Total share-based compensation | $ 116 | $ 140 | $ 137 | 
| Capitalized share-based compensation | (6) | (9) | (24) | 
| Total share-based compensation expense | 110 | 131 | 113 | 
| Tax benefit associated with share-based compensation expense | 23 | 14 | 6 | 
| Equity Awards [Member] | |||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Total share-based compensation | 114 | 131 | 89 | 
| Liability Awards [Member] | |||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Total share-based compensation | $ 2 | $ 9 | $ 48 | 
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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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