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Revenue Recognition, Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2018 | Jun. 30, 2018 | Jun. 30, 2017 | Jan. 01, 2018
Revenue recognition [Line Items] |  |  |  |
Cumulative effect of accounting change | $ 174 | $ 174 |  |
Bad debts expense |  | $ 40 | $ 47 |
Revenue recognition, practical expedient |  | false |  |
Capitalized contract cost |  |  |  |
Capitalized contract cost related to commission fees | 133 | $ 133 |  |
Capitalized contract cost, amortization method |  | Capitalized commission fees are amortized based on the transfer of the goods or services to which the assets relate, typically the contract term which ranges from thirteen months to thirty months. |  |
Amortization of contract cost assets | 26 | $ 54 |  |
Impairment of capitalized contract cost | 0 | $ 0 |  |
Contract cost practical expedient |  | true |  |
Retained earnings |  |  |  |
Revenue recognition [Line Items] |  |  |  |
Cumulative effect of accounting change | 173 | $ 173 |  |
Revenue from contract with customer |  |  |  |
Revenue recognition [Line Items] |  |  |  |
Bad debts expense | $ 22 | $ 40 |  |
ASU 2014-09 | Retained earnings |  |  |  |
Revenue recognition [Line Items] |  |  |  |
Cumulative effect of accounting change |  |  |  | $ 173
ASU 2017-05 | Retained earnings |  |  |  |
Revenue recognition [Line Items] |  |  |  |
Cumulative effect of accounting change |  |  |  | $ 0

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- Definition Amount of amortization expense for asset recognized from cost incurred to obtain or fulfill contract with customer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 340 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=68051541&loc=SL49131252-203054 + Details
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- Definition Amount of impairment loss for asset recognized from cost incurred to obtain or fulfill contract with customer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 340 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=68051541&loc=SL49131252-203054 + Details
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- Definition Amount, after accumulated amortization and accumulated impairment loss, of asset recognized from cost incurred to obtain or fulfill contract with customer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 340 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=68051541&loc=SL49131252-203054 + Details
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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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130534-203044 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.5) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130543-203045 + Details
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