Goodwill and Other Intangibles (Narrative) (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024	Dec. 31, 2023
Segment Reporting Information [Line Items]
Goodwill, impairment loss			$ 0
Indefinite-lived intangible assets	$ 0		0
Goodwill	23,538,000,000	$ 17,314,000,000	$ 23,306,000,000	$ 17,231,000,000
Aggregate amortization expense	139,000,000	$ 90,000,000
Risk and Insurance Services
Segment Reporting Information [Line Items]
Goodwill	19,000,000,000.0
Consulting
Segment Reporting Information [Line Items]
Goodwill	$ 4,500,000,000