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v3.19.2

Segment Information (Selected Information And Details For MMC's Operating Segments) (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Jun. 30, 2018
Segment Reporting Information [Line Items] |  |  |  |
Revenue | $ 4,349 | $ 3,734 | $ 8,420 | $ 7,734
Operating Income (Loss) | 680 | 691 | 1,618 | 1,599
Equity method income | 5 | 2 | 7 | 9
Risk and Insurance Services Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Interest on fiduciary funds | 26 |  | 49 |
Operating Segments |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 4,374 | 3,746 | 8,470 | 7,758
Operating Income (Loss) | 795 | 739 | 1,807 | 1,702
Operating Segments | Risk and Insurance Services Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 2,574 | 2,096 | 4,997 | 4,440
Operating Income (Loss) | 517 | 472 | 1,250 | 1,188
Interest on fiduciary funds | 26 | 15 | 49 | 28
Equity method income | 4 | 7 | 6 | 6
Operating Segments | Consulting Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 1,800 | 1,650 | 3,473 | 3,318
Operating Income (Loss) | 278 | 267 | 557 | 514
Interest on fiduciary funds | 1 | 1 | 2 | 2
Equity method income | 5 | 5 | 10 | 8
Corporate and Eliminations |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | (25) | (12) | (50) | (24)
Operating Income (Loss) | (115) | (48) | (189) | (103)
Intersegment Eliminations | Risk and Insurance Services Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 3 |  | 4 | 1
Intersegment Eliminations | Consulting Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | $ 22 | $ 12 | $ 46 | $ 23

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