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v3.24.2

Segment Information (Selected Information and Details for MMC's Operating Segments) (Details) - USD ($) $ in Millions |  | 3 Months Ended | 6 Months Ended
--- | --- | --- | ---
Jan. 01, 2024 | Jun. 30, 2024 | Jun. 30, 2023 | Jun. 30, 2024 | Jun. 30, 2023
Segment Reporting Information [Line Items] |  |  |  |  |
Revenue |  | $ 6,221 | $ 5,876 | $ 12,694 | $ 11,800
Operating Income/(Loss) |  | 1,642 | 1,457 | 3,567 | 3,183
Discontinued Operations, Disposed of by Sale | U.S. Health And Benefits And U.K Pension Administration Businesses |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Net gain includes in revenue consolidated statements of income | $ 21 |  |  |  |
Total Segments |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Revenue |  | 6,238 | 5,894 | 12,725 | 11,831
Operating Income/(Loss) |  | 1,707 | 1,545 | 3,704 | 3,351
Total Segments | Discontinued Operations, Disposed of by Sale | U.S. Health And Benefits And U.K Pension Administration Businesses |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Net gain includes in revenue consolidated statements of income |  |  |  | 21 |
Total Segments | Risk and Insurance Services |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Revenue |  | 4,022 | 3,722 | 8,295 | 7,628
Operating Income/(Loss) |  | 1,297 | 1,157 | 2,862 | 2,552
Interest on fiduciary funds |  | 125 | 108 | 247 | 199
Equity method investment income (loss) |  | 10 | 12 | 10 | 11
Total Segments | Consulting |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Revenue |  | 2,216 | 2,172 | 4,430 | 4,203
Operating Income/(Loss) |  | 410 | 388 | 842 | 799
Corporate/Eliminations |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Revenue |  | (17) | (18) | (31) | (31)
Operating Income/(Loss) |  | (65) | (88) | (137) | (168)
Intersegment Eliminations | Risk and Insurance Services |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Revenue |  | 4 | 5 | 5 | 5
Intersegment Eliminations | Consulting |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Revenue |  | $ 13 | $ 13 | $ 26 | $ 26

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