Share-Based Compensation - Schedule of Share-Based Compensation (Details) - USD ($) $ in Millions  | 
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2018  | 
Dec. 31, 2017  | 
Dec. 31, 2016  | 
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Total share-based compensation | $ 137 | $ 114 | $ 117 | 
| Capitalized share-based compensation | (24) | (23) | (16) | 
| Total share-based compensation expense | 113 | 91 | 101 | 
| Tax benefit associated with share-based compensation expense | 6 | 5 | 0 | 
| Equity Awards [Member] | |||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Total share-based compensation | 89 | 34 | 41 | 
| Liability Awards [Member] | |||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Total share-based compensation | $ 48 | $ 80 | $ 76 | 
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- Definition Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Represents the compensation cost capitalized during the period arising from equity-based compensation arrangements (for example, shares of stock, units, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period. 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 capitalized and expensed compensation cost from equity-based compensation arrangements. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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