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v3.21.2

Segment Information (Selected Information And Details For MMC's Operating Segments) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Segment Reporting Information [Line Items] |  |  |  |
Revenue | $ 4,583 | $ 3,968 | $ 14,683 | $ 12,808
Operating Income (Loss) | 740 | 540 | 3,326 | 2,495
Risk and Insurance Services Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 2,670 | 2,291 | 9,036 | 7,805
Interest on fiduciary funds | 4 | 8 | 12 | 40
Consulting Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 1,925 | 1,696 | 5,690 | 5,074
Operating Segments |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 4,595 | 3,987 | 14,726 | 12,879
Operating Income (Loss) | 807 | 611 | 3,522 | 2,698
Operating Segments | Risk and Insurance Services Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 2,670 | 2,291 | 9,036 | 7,805
Operating Income (Loss) | 403 | 333 | 2,413 | 1,883
Interest on fiduciary funds | 4 | 8 | 12 | 40
Equity method income (loss) | 8 | (6) | 25 | 7
Operating Segments | Consulting Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 1,925 | 1,696 | 5,690 | 5,074
Operating Income (Loss) | 404 | 278 | 1,109 | 815
Equity method income (loss) |  |  | 0 | 4
Corporate/Eliminations |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | (12) | (19) | (43) | (71)
Operating Income (Loss) | (67) | (71) | (196) | (203)
Intersegment Eliminations | Risk and Insurance Services Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue |  |  | 5 | 5
Intersegment Eliminations | Consulting Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | $ 11 | $ 19 | $ 38 | $ 66

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