Goodwill and Other Intangibles (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Goodwill	$ 16,300	$ 16,254	$ 16,251	$ 16,317
Aggregate amortization expense	85	$ 91
Risk and Insurance Services
Segment Reporting Information [Line Items]
Goodwill	12,500
Consulting
Segment Reporting Information [Line Items]
Goodwill	$ 3,800