Supplemental Disclosures (Schedule of Supplemental Cash Flow Disclosures) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental Cash Flow Information [Abstract]
Assets acquired, excluding cash	$ 960	$ 1,327	$ 815
Liabilities assumed	(111)	(199)	(64)
Contingent/deferred purchase consideration	(36)	(176)	(197)
Net cash outflow for acquisitions	813	952	554
Interest paid	178	146	172
Income taxes paid, net of refunds	$ 642	$ 433	$ 426