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v3.23.1

Intangible Assets - Changes in Carrying Amount of Goodwill (Detail) $ in Millions | 3 Months Ended
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Mar. 31, 2023 USD ($)
Goodwill [Line Items] |
Beginning Balance | $ 9,489.4
Goodwill acquired during the period | 181.2
Goodwill true-ups due to appraisals and other acquisition adjustments | 7.5
Foreign currency translation adjustments during the period | 25.1
Ending Balance | 9,703.2
Brokerage [Member] |
Goodwill [Line Items] |
Beginning Balance | 9,358.1
Goodwill acquired during the period | 181.2
Goodwill true-ups due to appraisals and other acquisition adjustments | 7.5
Foreign currency translation adjustments during the period | 25.0
Ending Balance | 9,571.8
Risk Management [Member] |
Goodwill [Line Items] |
Beginning Balance | 112.2
Ending Balance | 112.2
Corporate [Member] |
Goodwill [Line Items] |
Beginning Balance | 19.1
Foreign currency translation adjustments during the period | 0.1
Ending Balance | $ 19.2

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