Restructuring Costs (Restructuring and Related Costs Incurred) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Restructuring Cost and Reserve [Line Items]
Total	$ 65	$ 28	$ 118	$ 58
Corporate
Restructuring Cost and Reserve [Line Items]
Total	27	13	39	21
Risk and Insurance Services
Restructuring Cost and Reserve [Line Items]
Total	31	11	63	26
Consulting
Restructuring Cost and Reserve [Line Items]
Total	$ 7	$ 4	$ 16	$ 11