Goodwill and Other Intangibles (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Goodwill acquired			$ 104	$ 338
Goodwill	$ 15,963	$ 15,775	15,963	15,775	$ 16,317	$ 15,517
Aggregate amortization expense	83	$ 89	174	$ 189
Risk and Insurance Services Segment
Segment Reporting Information [Line Items]
Goodwill acquired			104
Goodwill, expected tax deductible amount	85		85
Goodwill	12,300		12,300
Consulting Segment
Segment Reporting Information [Line Items]
Goodwill	$ 3,700		$ 3,700