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v3.24.0.1

Segment Information (Selected Information and Details Of Operating Segment Revenue) (Details) - USD ($) $ in Millions | 1 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Oct. 31, 2023 | Mar. 31, 2022 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Segment Reporting Information [Line Items] |  |  |  |  |
Revenue |  |  | $ 22,736 | $ 20,720 | $ 19,820
Loss on consolidation of entity |  | $ 39 | 0 | 39 | 0
Fixed assets, net |  |  | 882 | 871 | 847
United States (a) |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Revenue |  |  | 10,924 | 10,215 | 9,343
Fixed assets, net |  |  | 468 | 473 | 484
United Kingdom (b) |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Revenue |  |  | 3,555 | 3,114 | 3,130
Fixed assets, net |  |  | 168 | 166 | 116
Other (c) |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Revenue |  |  | 8,319 | 7,455 | 7,401
Fixed assets, net |  |  | 246 | 232 | 247
Operating Segments |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Revenue |  |  | 22,798 | 20,784 | 19,874
Operating Segments | Risk and Insurance Services |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Revenue |  |  | 14,089 | 12,645 | 12,085
Pre-tax gain (loss) on sale |  |  |  |  | 50
Operating Segments | Risk and Insurance Services | RUSSIAN FEDERATION |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Loss on consolidation of entity |  |  |  | 27 |
Operating Segments | Consulting |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Revenue |  |  | 8,709 | 8,139 | 7,789
Operating Segments | Consulting | RUSSIAN FEDERATION |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Loss on consolidation of entity |  |  |  | 12 |
Corporate/Eliminations |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Revenue |  |  | (62) | (64) | (54)
Marsh | Operating Segments | Risk and Insurance Services |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Revenue |  |  | 11,657 | 10,585 | 10,214
Guy Carpenter | Risk and Insurance Services |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Gain from the settlement | $ (58) |  | (58) |  |
Guy Carpenter | Operating Segments | Risk and Insurance Services |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Revenue |  |  | 2,432 | 2,060 | 1,871
Mercer | Operating Segments | Consulting |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Revenue |  |  | 5,587 | 5,345 | 5,254
Oliver Wyman Group | Operating Segments | Consulting |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Revenue |  |  | 3,122 | 2,794 | 2,535
Small Individual Financial Advisory Business | Operating Segments | Consulting |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Pre-tax gain (loss) on sale |  |  | $ (17) |  |
Mercer U.S. Affinity Business | Operating Segments |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Pre-tax gain (loss) on sale |  |  |  |  | $ 50
Mercer U.S. Affinity Business | Operating Segments | Consulting |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Pre-tax gain (loss) on sale |  |  |  | $ 112 |

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