Quarterly report pursuant to Section 13 or 15(d)

Recent Accounting Pronouncements (Cash and Restricted Cash) (Details)

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Recent Accounting Pronouncements (Cash and Restricted Cash) (Details) - USD ($)
$ in Millions
Sep. 30, 2018
Dec. 31, 2017
Sep. 30, 2017
Dec. 31, 2016
Recent Accounting Pronouncements        
Cash and cash equivalents $ 532 $ 903    
Restricted cash included in other current assets $ 7 $ 9    
Restricted Cash and Cash Equivalents, Asset, Statement of Financial Position [Extensible List] Other Assets, Current Other Assets, Current    
Total cash, cash equivalents and restricted cash in the condensed consolidated statement of cash flows $ 539 $ 912 $ 907 $ 836