Supplemental Disclosures to the Consolidated Statements of Cash Flows (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Supplemental Cash Flow Information [Abstract]
Deferred and contingent consideration from prior years acquisition	$ 29	$ 70
Deferred purchase consideration from prior years' acquisitions	23	40
Contingent consideration from prior year's acquisitions	6	30
Net charge for adjustments related to acquisition related accounts	11	5
Payment of contingent consideration	29	10
Non-cash issuance of common stock	158	125
Stock-based compensation expense, equity awards	57	50
Proceeds from issuance of debt	6,462	$ 592
Interest income	25
Acquisition-related hedging payments	129
Right-of-use asset, noncash	1,700
Right-to-use liability, noncash	$ 1,900