Share-Based Compensation - Schedule of Unrecognized Compensation Cost (Details) $ in Millions  | 
12 Months Ended | 
|---|---|
| 
 Dec. 31, 2018  
USD ($) 
 | |
| Restricted Stock Share Awards [Member] | |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |
| Unrecognized compensation cost | $ 2 | 
| Recognized over a weighted average period | 4 months | 
| Restricted Share Unit And Performance Stock Unit Awards [Member] | |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |
| Unrecognized compensation cost | $ 136 | 
| Recognized over a weighted average period | 1 year 8 months | 
| Phantom Unit Awards [Member] | |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |
| Unrecognized compensation cost | $ 11 | 
| Recognized over a weighted average period | 1 year 5 months | 
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- Definition Unrecognized cost of unvested share-based compensation awards. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. 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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