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Derivatives and Hedging Activity - Summary of Amounts of Derivative Gains (Losses) Recognized In Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
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Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Loss | $ (32.8) | $ 13.8 | $ (26.5) | $ 7.1
Income (expense) related to fair value of derivative investments reclassified from accumulated other comprehensive earnings | (6.7) | (2.3) | (14.3) | (5.3)
Amount of Gain Recognized in Earnings Related to Amount Excluded from Effectiveness Testing | 0.0 | 0.3 | 0.2 | 1.2
Interest rate contracts |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Income (expense) related to fair value of derivative investments reclassified from accumulated other comprehensive earnings | (0.3) | (0.2) | (0.9) | (0.8)
Amount of Gain Recognized in Earnings Related to Amount Excluded from Effectiveness Testing | 0.0 | 0.0 | 0.0 | 0.0
Foreign exchange contracts |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Income (expense) related to fair value of derivative investments reclassified from accumulated other comprehensive earnings | (5.9) | (1.1) | (11.1) | (1.9)
Amount of Gain Recognized in Earnings Related to Amount Excluded from Effectiveness Testing | 0.0 | 0.0 | 0.0 | 0.0
Interest expense | Interest rate contracts |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Loss | (7.5) | (5.8) | (29.1) | (8.7)
Commission revenue | Foreign exchange contracts |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Loss | (25.3) | 19.6 | 2.6 | 15.8
Compensation expense |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Income (expense) related to fair value of derivative investments reclassified from accumulated other comprehensive earnings | (0.3) | (0.6) | (1.4) | (1.5)
Amount of Gain Recognized in Earnings Related to Amount Excluded from Effectiveness Testing | 0.0 | 0.2 | 0.1 | 0.7
Operating expense |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Income (expense) related to fair value of derivative investments reclassified from accumulated other comprehensive earnings | (0.2) | (0.4) | (0.9) | (1.1)
Amount of Gain Recognized in Earnings Related to Amount Excluded from Effectiveness Testing | $ 0.0 | $ 0.1 | $ 0.1 | $ 0.5

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