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v3.23.1

Segment Information - Schedule of Segment Reporting Information by Segment (Detail) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2023 | Mar. 31, 2022 | Dec. 31, 2022
Segment Reporting Information [Line Items] |  |  |
Total revenues | $ 2,706.1 | $ 2,435.3 |
Earnings before income taxes | 605.8 | 537.7 |
Identifiable assets at March 31, 2023 and 2022 | 45,094.4 | 42,897.5 | $ 38,358.4
Operating Segments [Member] | Brokerage [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Total revenues | 2,375.2 | 2,122.6 |
Earnings before income taxes | 690.9 | 618.4 |
Identifiable assets at March 31, 2023 and 2022 | 40,919.9 | 39,237.3 |
Operating Segments [Member] | Risk Management [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Total revenues | 330.8 | 289.9 |
Earnings before income taxes | 45.5 | 32.3 |
Identifiable assets at March 31, 2023 and 2022 | 1,126.7 | 1,047.2 |
Operating Segments [Member] | Corporate [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Total revenues | 0.1 | 22.8 |
Earnings before income taxes | (130.6) | (113.0) |
Identifiable assets at March 31, 2023 and 2022 | $ 3,047.8 | $ 2,613.0 |

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- Definition Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. 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