Acquisitions and Dispositions (Allocation Of Acquisition Costs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Cash	$ 694	$ 5,861
Estimated fair value of deferred/contingent consideration	183	66	$ 133
Total consideration	877	5,927
Allocation of purchase price:
Goodwill	15,517	$ 14,671	$ 9,599
Current Fiscal Period Acquisitions
Business Acquisition [Line Items]
Cash	694
Estimated fair value of deferred/contingent consideration	183
Total consideration	877
Allocation of purchase price:
Cash and cash equivalents	26
Accounts receivable, net	29
Fixed assets, net	16
Other intangible assets	278
Goodwill	593
Other assets	13
Total assets acquired	955
Current liabilities	25
Other liabilities	53
Total liabilities assumed	78
Net assets acquired	$ 877