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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, 2020 | Jun. 30, 2019 | Jun. 30, 2020 | Jun. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Loss | [1] | $ 8.1 | $ (29.4) | $ (125.4) | $ (46.6)
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income into Income Loss into Earnings |  | (1.3) | (1.2) | (2.5) | (1.9)
Amount of Gain (Loss) Recognized in Earnings Related to Amount Excluded from Effectiveness Testing |  | 0.5 | 0.4 | 0.7 | 0.8
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 | (25.8) | (108.1) | (46.7)
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income into Income 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] | 2.0 | (3.6) | (17.3) | 0.1
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income into Income Loss into Earnings |  | (0.1) | (0.1) | (0.5) | (0.2)
Amount of Gain (Loss) Recognized in Earnings Related to Amount Excluded from Effectiveness Testing |  | (0.1) | (0.2) | (0.3) | (0.4)
Compensation expense [Member] |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income into Income Loss into Earnings |  | (0.5) | (0.4) | (0.8) | (0.6)
Amount of Gain (Loss) Recognized in Earnings Related to Amount Excluded from Effectiveness Testing |  | 0.4 | 0.3 | 0.6 | 0.7
Operating expense [Member] |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income into Income Loss into Earnings |  | (0.4) | (0.4) | (0.6) | (0.5)
Amount of Gain (Loss) Recognized in Earnings Related to Amount Excluded from Effectiveness Testing |  | $ 0.2 | $ 0.3 | $ 0.4 | $ 0.5
[1] | For the three-month and six-month periods ended June 30, 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 $0.1 million and $0.4 million, respectively.

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