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Supplemental Disclosures to the Consolidated Statements of Cash Flows (Narrative) (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2018 | Mar. 31, 2017
Supplemental Disclosure to the Consolidate Statements of Cash Flows [Line Items] |  |
Deferred and contingent consideration from prior years acquisition | $ 70 | $ 34
Contingent consideration from prior year's acquisitions | 30 | 8
Net charge for adjustments related to acquisition related accounts | 5 | (16)
Payment of contingent consideration | 10 | 4
Non-cash issuance of common stock | 125 | 85
Stock-based compensation expense, equity awards | 50 | 42
Prior Fiscal Periods Acquisitions |  |
Supplemental Disclosure to the Consolidate Statements of Cash Flows [Line Items] |  |
Deferred purchase consideration from prior years' acquisitions | 40 | 26
Contingent consideration from prior year's acquisitions | $ 40 | $ 12

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