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Acquisitions and Dispositions of Businesses - Completed Dispositions (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |
Gains (losses) on disposal of businesses | $ 13 | $ (6) | $ (16)
Disposal Group, Not Discontinued Operations |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |
Number of dispositions | 8 | 4 | 9
Amortization and Impairment of Intangible Assets |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |
Non-cash impairment charge of disposition |  |  | $ 380
Amortization and Impairment of Intangible Assets | Disposal Group, Held-for-sale |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |
Non-cash impairment charge of disposition |  | $ 176 |

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