Supplemental Disclosures (Schedule of Supplemental Cash Flow Disclosures) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Supplemental Cash Flow Information [Abstract]
Assets acquired, excluding cash	$ 929	$ 8,655	$ 1,100
Liabilities assumed	(78)	(2,804)	(83)
Non-controlling interests assumed	0	(280)	0
Contingent and deferred purchase consideration	(183)	(66)	(133)
Net cash outflow for acquisitions	668	5,505	884
Interest paid	481	427	264
Income taxes paid, net of refunds	$ 673	$ 661	$ 632