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v3.19.3

Segment Information (Selected Information And Details For MMC's Operating Segments) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018
Segment Reporting Information [Line Items] |  |  |  |
Revenue | $ 3,968 | $ 3,504 | $ 12,388 | $ 11,238
Operating Income (Loss) | 467 | 541 | 2,085 | 2,140
Equity method income | 3 | 4 | 10 | 14
Risk and Insurance Services Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Interest on fiduciary funds | 31 |  | 80 |
Operating Segments |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 3,991 | 3,519 | 12,461 | 11,277
Operating Income (Loss) | 535 | 584 | 2,342 | 2,286
Operating Segments | Risk and Insurance Services Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 2,206 | 1,863 | 7,203 | 6,303
Operating Income (Loss) | 218 | 293 | 1,468 | 1,481
Interest on fiduciary funds | 31 | 18 | 80 | 46
Equity method income | 10 | 4 | 16 | 10
Proceeds from divestiture of businesses |  | 51 |  | 51
Operating Segments | Consulting Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 1,785 | 1,656 | 5,258 | 4,974
Operating Income (Loss) | 317 | 291 | 874 | 805
Interest on fiduciary funds | 1 | 1 | 2 | 3
Equity method income |  | 4 | 10 | 12
Corporate/Eliminations |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | (23) | (15) | (73) | (39)
Operating Income (Loss) | (68) | (43) | (257) | (146)
Intersegment Eliminations | Risk and Insurance Services Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 3 | 4 | 7 | 5
Intersegment Eliminations | Consulting Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | $ 20 | $ 11 | $ 66 | $ 34

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