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Consolidated Balance Sheets (Parentheticals) - USD ($)
$ in Millions
Mar. 31, 2019
Dec. 31, 2018
Allowance for doubtful accounts $ 114 $ 112
Accumulated depreciation $ 1,348 $ 1,281
Common stock par value $ 0.01 $ 0.01
Common Stock, Shares Authorized 1 1