Acquisitions and Dispositions (Allocation Of Acquisition Costs) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Cash	$ 367	$ 576
Estimated fair value of deferred/contingent consideration	138	161
Total consideration	505	737
Allocation of purchase price:
Goodwill	15,775	$ 14,797	$ 15,517	$ 14,671
Current Fiscal Period Acquisitions
Business Acquisition [Line Items]
Cash	367
Estimated fair value of deferred/contingent consideration	138
Total consideration	505
Allocation of purchase price:
Cash and cash equivalents	4
Accounts receivable, net	30
Other current assets	1
Fixed assets, net	4
Other intangible assets	188
Goodwill	338
Total assets acquired	565
Current liabilities	23
Other liabilities	37
Total liabilities assumed	60
Net assets acquired	$ 505