Gain (Loss) on Consolidation of Business

No definition available.

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- Definition

Interest income earned on both U.S. and foreign fiduciary funds held in trust.

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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- Definition

Amount of gain (loss) from sale and disposal of integrated set of activities and assets capable of being conducted and managed for purpose of providing return in form of dividend, lower cost, or other economic benefit to investor, owner, member and participant.

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- Definition

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

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Revenue (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Revenue	$ 5,382	$ 4,770	$ 17,182	$ 15,698
Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	5,396	4,789	17,227	15,745
Risk and Insurance Services \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	3,190	2,838	10,818	9,700
Fiduciary interest income	131	40	330	57
Loss on consolidation of business				(27)
Consulting \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	2,206	1,951	6,409	6,045
Marsh & Guy Carpenter \| Risk and Insurance Services \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	3,059	2,798	10,488	9,643
Marsh \| Operating Segments
Disaggregation of Revenue [Line Items]
Loss on consolidation of business				(27)
Marsh \| Risk and Insurance Services \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	2,700	2,470	8,482	7,794
Marsh \| Risk and Insurance Services \| Total International \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	1,137	1,019	3,848	3,531
Marsh \| Risk and Insurance Services \| EMEA \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	692	615	2,482	2,264
Marsh \| Risk and Insurance Services \| Asia Pacific \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	311	286	980	927
Marsh \| Risk and Insurance Services \| Latin America \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	134	118	386	340
Marsh \| Risk and Insurance Services \| U.S./Canada \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	1,563	1,451	4,634	4,263
Guy Carpenter \| Risk and Insurance Services \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	359	328	2,006	1,849
Mercer \| Consulting \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	1,425	1,284	4,143	4,016
Mercer \| Consulting \| Wealth \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	635	561	1,853	1,775
Mercer \| Consulting \| Health \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	496	451	1,559	1,562
Mercer \| Consulting \| Career \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	294	272	731	679
Oliver Wyman Group \| Operating Segments
Disaggregation of Revenue [Line Items]
Loss on consolidation of business				(12)
Oliver Wyman Group \| Consulting \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 781	$ 667	2,266	2,029
Small Individual Financial Advisory Business \| Operating Segments
Disaggregation of Revenue [Line Items]
Pre-tax gain (loss) on sale			$ (17)
Mercer U.S. Affinity Business \| Operating Segments
Disaggregation of Revenue [Line Items]
Pre-tax gain (loss) on sale				$ 112