Restructuring Costs (Restructuring and Related Costs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 276	$ 301
Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring charges	49	62
Risk and Insurance Services
Restructuring Cost and Reserve [Line Items]
Restructuring charges	148	177
Consulting Segment
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 79	$ 62