Supplemental Disclosures to the Consolidated Statements of Cash Flows (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Supplemental Disclosure to the Consolidate Statements of Cash Flows [Line Items]
Deferred and contingent consideration from prior years acquisition	$ 34	$ 39
Contingent consideration from prior year's acquisitions	8	14
Net charge for adjustments related to acquisition related accounts	(16)	5
Payment of contingent consideration	4	4
Non-cash issuance of common stock	85	67
Stock-based compensation expense, equity awards	28	20
Effective income tax rate reconciliation, share-based compensation, excess tax benefit, amount	44	18
Prior Fiscal Periods Acquisitions
Supplemental Disclosure to the Consolidate Statements of Cash Flows [Line Items]
Deferred purchase consideration from prior years' acquisitions	26	25
Contingent consideration from prior year's acquisitions	$ 12	$ 18