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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 | 6 Months Ended
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Jun. 30, 2021 | Jun. 30, 2020 | Jun. 30, 2021 | Jun. 30, 2020
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Loss | [1] | $ (46.1) | $ 8.1 | $ 28.0 | $ (125.4)
Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Earnings |  | (2.0) | (1.3) | (3.7) | (2.5)
Amount of Gain (Loss) Recognized in Earnings Related to Amount Excluded from Effectiveness Testing |  | 0.3 | 0.5 | 0.9 | 0.7
Interest expense [Member] | Interest Rate Contracts [Member] |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Loss | [1] | (41.7) | 6.1 | 34.1 | (108.1)
Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Earnings |  | (0.3) | (0.3) | (0.6) | (0.6)
Commission revenue [Member] | Foreign Exchange Contracts [Member] |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Loss | [1] | (4.4) | 2.0 | (6.1) | (17.3)
Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Earnings |  | (1.4) | (0.1) | (2.3) | (0.5)
Amount of Gain (Loss) Recognized in Earnings Related to Amount Excluded from Effectiveness Testing |  | (0.1) | (0.1) | (0.2) | (0.3)
Compensation expense [Member] |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |
Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Earnings |  | (0.2) | (0.5) | (0.5) | (0.8)
Amount of Gain (Loss) Recognized in Earnings Related to Amount Excluded from Effectiveness Testing |  | 0.2 | 0.4 | 0.6 | 0.6
Operating expense [Member] |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |
Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Earnings |  | (0.1) | (0.4) | (0.3) | (0.6)
Amount of Gain (Loss) Recognized in Earnings Related to Amount Excluded from Effectiveness Testing |  | $ 0.2 | $ 0.2 | $ 0.5 | $ 0.4
[1] | For the three and six-month periods ended June 30, 2021 and 2020, the amount excluded from the assessment of hedge effectiveness for our foreign exchange contracts recognized in accumulated other comprehensive loss was a loss of zero and $1.2 million, respectively.

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