Restructuring Costs (Restructuring and Related Costs Incurred) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Restructuring Cost and Reserve [Line Items]
Total	$ 42	$ 53
Corporate
Restructuring Cost and Reserve [Line Items]
Total	9	12
Risk and Insurance Services
Restructuring Cost and Reserve [Line Items]
Total	22	32
Consulting
Restructuring Cost and Reserve [Line Items]
Total	$ 11	$ 9