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Acquisitions and Dispositions (Allocation Of Acquisition Costs) (Details) - USD ($) $ in Millions | 9 Months Ended |  |
--- | --- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Dec. 31, 2020 | Dec. 31, 2019
Business Acquisition [Line Items] |  |  |  |
Cash | $ 405 | $ 579 |  |
Estimated fair value of deferred/contingent consideration | 141 | 163 |  |
Total consideration | 546 | 742 |  |
Allocation of purchase price: |  |  |  |
Goodwill | 15,648 | $ 15,034 | $ 15,517 | $ 14,671
Current Fiscal Period Acquisitions |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Cash | 405 |  |  |
Estimated fair value of deferred/contingent consideration | 141 |  |  |
Total consideration | 546 |  |  |
Allocation of purchase price: |  |  |  |
Cash and cash equivalents | 4 |  |  |
Accounts receivable, net | 32 |  |  |
Fixed assets, net | 5 |  |  |
Other intangible assets | 190 |  |  |
Goodwill | 374 |  |  |
Total assets acquired | 605 |  |  |
Current liabilities | 27 |  |  |
Other liabilities | 32 |  |  |
Total liabilities assumed | 59 |  |  |
Net assets acquired | $ 546 |  |  |

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