Goodwill and Other Intangibles (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Indefinite lived identified intangible assets	$ 0	$ 0
Goodwill	23,306,000,000	17,231,000,000	$ 16,251,000,000
Aggregate amortization expense	377,000,000	343,000,000	$ 338,000,000
Risk and Insurance Services
Segment Reporting Information [Line Items]
Goodwill expected to be tax deductible	1,800,000,000	230,000,000
Goodwill	18,800,000,000
Consulting Segment
Segment Reporting Information [Line Items]
Goodwill expected to be tax deductible	88,000,000	$ 12,000,000
Goodwill	$ 4,500,000,000