Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Millions  | 
Mar. 31, 2020  | 
Dec. 31, 2019  | 
|---|---|---|
| Allowance for doubtful accounts | $ 132 | $ 123 | 
| Accumulated depreciation | $ 1,367 | $ 1,338 | 
| Common stock par value | $ 0.01 | $ 0.01 | 
| Common Stock, Shares Authorized | 1 | 1 | 
| X | ||||||||||
- Definition Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
- Definition Amount of allowance for credit loss on accounts receivable, classified as current. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
  | 
| X | ||||||||||
- Definition Face amount or stated value per share of common stock. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
- Definition The maximum number of common shares permitted to be issued by an entity's charter and bylaws. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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