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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 | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Loss | [1] | $ (16.8) | $ 101.9
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Earnings |  | (6.8) | (3.1)
Amount of Gain (Loss) Recognized in Earnings Related to Amount Excluded from Effectiveness Testing |  | 1.4 | 3.0
Interest Rate Contracts [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Earnings |  | $ (1.2) | $ (1.1)
Derivative Instrument, Gain (Loss) Reclassified from AOCI into Income, Effective Portion, Statement of Income or Comprehensive Income [Extensible Enumeration] |  | Interest | Interest
Foreign Exchange Contracts [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Earnings |  | $ (2.0) | $ 1.3
Amount of Gain (Loss) Recognized in Earnings Related to Amount Excluded from Effectiveness Testing |  |  | $ (0.1)
Derivative Instrument, Gain (Loss) Reclassified from AOCI into Income, Effective Portion, Statement of Income or Comprehensive Income [Extensible Enumeration] |  | Total revenues | Total revenues
Interest expense [Member] | Interest Rate Contracts [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Loss | [1] | $ (6.1) | $ 63.9
Commission revenue [Member] | Foreign Exchange Contracts [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Loss | [1] | (10.7) | 38.0
Compensation expense [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Earnings |  | (2.2) | (1.9)
Amount of Gain (Loss) Recognized in Earnings Related to Amount Excluded from Effectiveness Testing |  | $ 0.8 | $ 1.8
Derivative Instrument, Gain (Loss) Reclassified from AOCI into Income, Effective Portion, Statement of Income or Comprehensive Income [Extensible Enumeration] |  | Compensation | Compensation
Operating expense [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Earnings |  | $ (1.4) | $ (1.4)
Amount of Gain (Loss) Recognized in Earnings Related to Amount Excluded from Effectiveness Testing |  | $ 0.6 | $ 1.3
Derivative Instrument, Gain (Loss) Reclassified from AOCI into Income, Effective Portion, Statement of Income or Comprehensive Income [Extensible Enumeration] |  | Operating | Operating
[1] | During 2024, the amount excluded from the assessment of hedge effectiveness for our foreign exchange contracts recognized in accumulated other comprehensive loss was a loss of $0.2 million.

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