Accounts Receivable Accounts Receivable (Activity in the Allowance for Doubtful Accounts) (Details) - USD ($) $ in Millions |
12 Months Ended | ||
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Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
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| Allowance for Doubtful Accounts Receivable [Roll Forward] | |||
| Balance beginning of year | $ 91 | $ 97 | $ 86 |
| Additions- charged to expense | 112 | 72 | 107 |
| Deductions- write-offs | (91) | (78) | (96) |
| Balance end of year | $ 112 | $ 91 | $ 97 |
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- Definition For an unclassified balance sheet, a valuation allowance for receivables due a company that are expected to be uncollectible. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. No definition available.
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- Definition Amount of direct write-downs of accounts receivable charged against the allowance. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Amount of expense related to write-down of receivables to the amount expected to be collected. Includes, but is not limited to, accounts receivable and notes receivable. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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