Goodwill and Other Intangibles (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Goodwill	$ 16,251	$ 16,317	$ 15,517
Aggregate amortization expense	338	365	$ 351
Risk and Insurance Services
Segment Reporting Information [Line Items]
Goodwill expected to be tax deductible	348	$ 96
Goodwill	12,500
Consulting Segment
Segment Reporting Information [Line Items]
Goodwill expected to be tax deductible	64
Goodwill	$ 3,800