Goodwill and Other Intangibles (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Goodwill acquired			$ 139	$ 374
Goodwill	$ 15,576	$ 15,648	15,576	15,648	$ 16,317	$ 15,517
Aggregate amortization expense	84	$ 89	258	$ 278
Risk and Insurance Services
Segment Reporting Information [Line Items]
Goodwill acquired			92
Goodwill, expected tax deductible amount	92		92
Goodwill	12,000		12,000
Consulting
Segment Reporting Information [Line Items]
Goodwill acquired			25
Goodwill, expected tax deductible amount	25		25
Goodwill	$ 3,600		$ 3,600