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Impairments and Assets Held For Sale (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Segment Reporting Information [Line Items]      
Document Period End Date Dec. 31, 2019    
Income tax benefit $ (10) $ (13) $ (15)
Assets held for sale 25 36  
Depreciation and amortization 647 690 683
Gain on sale of assets $ (6) $ 16 $ (1)