Supplemental Disclosures to the Consolidated Statements of Cash Flows (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Supplemental Disclosure to the Consolidate Statements of Cash Flows [Line Items]
Deferred and contingent consideration from prior years acquisition	$ 97	$ 63
Contingent consideration from prior year's acquisitions	60	24
Net charge for adjustments related to acquisition related accounts	(8)	18
Payment of contingent consideration	5	26
Non-cash issuance of common stock	87	70
Stock-based compensation expense, equity awards	75	58
Effective income tax rate reconciliation, share-based compensation, excess tax benefit, amount	(48)
Adjustments to additional paid in capital, income tax benefit from share-based compensation		24
Excess tax benefit from share-based compensation, financing activities		24
Prior Fiscal Periods Acquisitions
Supplemental Disclosure to the Consolidate Statements of Cash Flows [Line Items]
Deferred purchase consideration from prior years' acquisitions	37	39
Contingent consideration from prior year's acquisitions	$ 65	$ 50