Quarterly report pursuant to Section 13 or 15(d)

Recent Accounting Pronouncements - Cash flow changes, reconciliation of components of cash (Details)

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Recent Accounting Pronouncements - Cash flow changes, reconciliation of components of cash (Details) - USD ($)
$ in Millions
Mar. 31, 2018
Dec. 31, 2017
Mar. 31, 2017
Dec. 31, 2016
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]        
Cash and cash equivalents $ 1,042 $ 1,029    
Restricted cash included in other current assets 27 8    
Restricted cash included in other assets 10 10    
Total cash and cash equivalents and restricted cash at end of period $ 1,079 $ 1,047 $ 1,081 $ 572