Annual report pursuant to Section 13 and 15(d)

Acquisitions and Dispositions (Details)

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Acquisitions and Dispositions (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]    
Gain (Loss) on Dispositions, Net $ (18)  
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 (18)  
Disposal Group, Including Discontinued Operation, Revenue 13 $ 52
Disposal Group Net Earnings Loss $ (2) $ (8)