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Supplemental Disclosures to the Consolidated Statements of Cash Flows (Narrative) (Details) - USD ($) $ in Millions | 6 Months Ended
--- | ---
Jun. 30, 2021 | Jun. 30, 2020
Supplemental Cash Flow Information [Abstract] |  |
Deferred and contingent consideration from prior years acquisition | $ 97 | $ 69
Deferred purchase consideration from prior years' acquisitions | 84 | 27
Contingent consideration from prior year's acquisitions | 13 | 42
Contingent consideration from prior year's dispositions | 71 |
Credit adjustment related to contingent consideration liabilities | 17 | 6
Payment of contingent consideration | 4 | 36
Adjustments related to contingent consideration receivable | 24 |
Proceeds from contingent consideration, prior period dispositions | 18 |
Non-cash issuance of common stock | 228 | 213
Stock-based compensation expense, equity awards | $ 176 | $ 147

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