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v3.20.2

Segment Information (Selected Information And Details For MMC's Operating Segments) (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2020 | Jun. 30, 2019 | Jun. 30, 2020 | Jun. 30, 2019
Segment Reporting Information [Line Items] |  |  |  |
Revenue | $ 4,189 | $ 4,349 | $ 8,840 | $ 8,420
Operating Income (Loss) | 885 | 680 | 1,955 | 1,618
Risk and Insurance Services Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 2,603 | 2,574 | 5,514 | 4,997
Interest on fiduciary funds | 9 | 26 | 32 | 49
Consulting Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 1,616 | 1,800 | 3,378 | 3,473
Operating Segments |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 4,219 | 4,374 | 8,892 | 8,470
Operating Income (Loss) | 951 | 795 | 2,087 | 1,807
Operating Segments | Risk and Insurance Services Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 2,603 | 2,574 | 5,514 | 4,997
Operating Income (Loss) | 696 | 517 | 1,550 | 1,250
Interest on fiduciary funds | 9 | 26 | 32 | 49
Equity method income | 14 | 4 | 13 | 6
Operating Segments | Consulting Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 1,616 | 1,800 | 3,378 | 3,473
Operating Income (Loss) | 255 | 278 | 537 | 557
Interest on fiduciary funds | 1 | 1 | 1 | 2
Equity method income |  | 5 | 4 | 10
Corporate/Eliminations |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | (30) | (25) | (52) | (50)
Operating Income (Loss) | (66) | (115) | (132) | (189)
Intersegment Eliminations | Risk and Insurance Services Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 4 | 3 | 5 | 4
Intersegment Eliminations | Consulting Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | $ 26 | $ 22 | $ 47 | $ 46

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