Acquisitions and Dispositions (Allocation Of Acquisition Costs) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Cash	$ 579	$ 5,859
Estimated fair value of deferred/contingent consideration	163	66
Total consideration	742	5,925
Allocation of purchase price:
Goodwill	15,034	$ 14,286	$ 14,671	$ 9,599
Current Fiscal Period Acquisitions
Business Acquisition [Line Items]
Cash	579
Estimated fair value of deferred/contingent consideration	163
Total consideration	742
Allocation of purchase price:
Cash and cash equivalents	20
Accounts receivable, net	27
Fixed assets, net	15
Other intangible assets	280
Goodwill	462
Other assets	11
Total assets acquired	815
Current liabilities	22
Other liabilities	51
Total liabilities assumed	73
Net assets acquired	$ 742