Supplemental Disclosures to the Consolidated Statements of Cash Flows (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Supplemental Disclosure to the Consolidate Statements of Cash Flows [Line Items]
Deferred and contingent consideration from prior years acquisition	$ 127	$ 96
Contingent consideration from prior year's acquisitions	80	43
Net charge for adjustments related to acquisition related accounts	(3)	5
Payment of contingent consideration	27	42
Non-cash issuance of common stock	88	71
Stock-based compensation expense, equity awards	111	84
Effective income tax rate reconciliation, share-based compensation, excess tax benefit, amount	(58)
Adjustments to additional paid in capital, income tax benefit from share-based compensation		30
Prior Fiscal Periods Acquisitions
Supplemental Disclosure to the Consolidate Statements of Cash Flows [Line Items]
Deferred purchase consideration from prior years' acquisitions	47	53
Contingent consideration from prior year's acquisitions	$ 107	$ 85