Quarterly report pursuant to Section 13 or 15(d)

Basis of Presentation (Details)

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Basis of Presentation (Details) - USD ($)
$ in Millions
1 Months Ended 3 Months Ended 9 Months Ended
Jun. 30, 2017
Sep. 30, 2018
Sep. 30, 2018
Sep. 30, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]        
Gain (loss) on dispositions, net (note 1)       $ (18)
Tax Act transition tax adjustment   $ 2 $ 2  
Buy Seasons | Disposed of by Sale        
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]        
Gain (loss) on dispositions, net (note 1) $ (18)      
Disposal Group Revenue       13
Disposal Group Net Earnings Loss       $ (1)