Supplemental Disclosures to the Consolidated Statements of Cash Flows (Additional Information Concerning Acquisitions, Interest And Income Taxes Paid) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Supplemental Cash Flow Information [Abstract]
Assets acquired, excluding cash	$ 35	$ 577
Liabilities assumed	(4)	(76)
Contingent/deferred purchase consideration	(7)	(90)
Net cash outflow for current year acquisitions	24	411
Interest paid	80	62
Income taxes paid, net of refunds	$ 128	$ 100