Acquisitions and Dispositions (Allocation Of Acquisition Costs) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Cash	$ 553	$ 640
Estimated fair value of deferred/contingent consideration	108	94
Total consideration	661	734
Allocation of purchase price:
Goodwill	9,435	$ 9,100	$ 9,089	$ 8,369
Current Fiscal Period Acquisitions
Business Acquisition [Line Items]
Cash	553
Estimated fair value of deferred/contingent consideration	108
Total consideration	661
Allocation of purchase price:
Cash and cash equivalents	17
Accounts receivable, net	25
Property, plant, and equipment	6
Other intangible assets	232
Goodwill	410
Other intangible assets	6
Total assets acquired	696
Current liabilities	17
Other liabilities	18
Total liabilities assumed	35
Net assets acquired	$ 661