Acquisitions and Dispositions (Allocation of Acquisition Costs) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Business Acquisition [Line Items]
Cash	$ 1,100	$ 682
Estimated fair value of deferred/contingent purchase consideration	176	29
Total consideration	1,300	711
Allocation of purchase price:
Goodwill	18,235	$ 16,655	$ 17,231	$ 16,251
Current Fiscal Period Acquisitions
Business Acquisition [Line Items]
Cash	1,078
Estimated fair value of deferred/contingent purchase consideration	176
Total consideration	1,254
Allocation of purchase price:
Cash and cash equivalents	28
Cash and cash equivalents held in a fiduciary capacity	8
Net receivables	67
Other current assets	30
Goodwill	826
Other intangible assets	371
Fixed assets, net	5
Right of use assets	9
Other assets	2
Total assets acquired	1,346
Current liabilities	29
Fiduciary liabilities	8
Other liabilities	55
Total liabilities assumed	92
Net assets acquired	$ 1,254