Acquisitions and Dispositions (Allocation Of Acquisition Costs) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Cash	$ 201	$ 142
Estimated fair value of deferred/contingent consideration	44	35
Total consideration	245	177
Allocation of purchase price:
Goodwill	14,412	$ 9,739	$ 14,671	$ 9,599
Current Fiscal Period Acquisitions
Business Acquisition [Line Items]
Cash	201
Estimated fair value of deferred/contingent consideration	44
Total consideration	245
Allocation of purchase price:
Cash and cash equivalents	1
Accounts receivable, net	9
Fixed assets, net	3
Other intangible assets	91
Goodwill	142
Other assets	4
Total assets acquired	250
Current liabilities	5
Total liabilities assumed	5
Net assets acquired	$ 245