Acquisitions and Dispositions (Allocation Of Acquisition Costs) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Business Acquisition [Line Items]
Cash	$ 308	$ 11
Estimated fair value of deferred/contingent purchase consideration	51	4
Total consideration	359	15
Allocation of purchase price:
Goodwill	17,314	$ 16,300	$ 17,231	$ 16,251
Current Fiscal Period Acquisitions
Business Acquisition [Line Items]
Cash	308
Estimated fair value of deferred/contingent purchase consideration	51
Total consideration	359
Allocation of purchase price:
Cash and cash equivalents	2
Cash and cash equivalents held in a fiduciary capacity	5
Net receivables	35
Goodwill	216
Other intangible assets	115
Fixed assets, net	3
Right of use assets	1
Other assets	2
Total assets acquired	379
Current liabilities	6
Fiduciary liabilities	5
Other liabilities	9
Total liabilities assumed	20
Net assets acquired	$ 359