Goodwill and Other Intangibles (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024	Dec. 31, 2023
Segment Reporting Information [Line Items]
Goodwill, impairment loss		$ 0
Indefinite-lived intangible assets	$ 0		$ 0		$ 0
Goodwill	23,949,000,000	18,235,000,000	23,949,000,000	$ 18,235,000,000	$ 23,306,000,000	$ 17,231,000,000
Aggregate amortization expense	133,000,000	$ 90,000,000	412,000,000	$ 269,000,000
Consulting
Segment Reporting Information [Line Items]
Goodwill expected to be tax deductible	30,000,000		30,000,000
Goodwill	4,700,000,000		4,700,000,000
Risk and Insurance Services
Segment Reporting Information [Line Items]
Goodwill expected to be tax deductible	14,000,000		14,000,000
Goodwill	$ 19,200,000,000		$ 19,200,000,000