Goodwill and Other Intangibles (Narrative) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Indefinite-lived intangible assets	$ 0		$ 0		$ 0
Goodwill	16,621,000,000	$ 15,963,000,000	16,621,000,000	$ 15,963,000,000	$ 16,251,000,000	$ 16,317,000,000
Aggregate amortization expense	87,000,000	$ 83,000,000	172,000,000	$ 174,000,000
Risk and Insurance Services
Segment Reporting Information [Line Items]
Goodwill expected to be tax deductible	2,600,000		2,600,000
Goodwill	12,600,000,000		12,600,000,000
Consulting
Segment Reporting Information [Line Items]
Goodwill expected to be tax deductible	11,300,000		11,300,000
Goodwill	$ 4,000,000,000		$ 4,000,000,000