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v3.25.1

Segment Information (Details of Operating Segment Revenue) (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2025 | Mar. 31, 2024
Segment Reporting Information [Line Items] |  |
Revenue | $ 7,061 | $ 6,473
Operating Segments |  |
Segment Reporting Information [Line Items] |  |
Revenue | 7,076 | 6,487
Operating Segments | Risk and Insurance Services |  |
Segment Reporting Information [Line Items] |  |
Revenue | 4,762 | 4,273
Operating Segments | Risk and Insurance Services | Marsh |  |
Segment Reporting Information [Line Items] |  |
Revenue | 3,520 | 3,081
Operating Segments | Risk and Insurance Services | Guy Carpenter |  |
Segment Reporting Information [Line Items] |  |
Revenue | 1,242 | 1,192
Operating Segments | Consulting |  |
Segment Reporting Information [Line Items] |  |
Revenue | 2,314 | 2,214
Operating Segments | Consulting | Mercer |  |
Segment Reporting Information [Line Items] |  |
Revenue | 1,496 | 1,425
Operating Segments | Consulting | Oliver Wyman Group |  |
Segment Reporting Information [Line Items] |  |
Revenue | 818 | 789
Corporate/Eliminations |  |
Segment Reporting Information [Line Items] |  |
Revenue | $ (15) | $ (14)

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