Accumulated Other Comprehensive Loss - Components of Accumulated Other Comprehensive Loss (Detail) $ in Millions	3 Months Ended
Mar. 31, 2019 USD ($)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 1,615.5
Other comprehensive income (loss) before income taxes and reclassifications	34.1
Income tax expense	(2.7)
Reclassifications to earnings	2.6
Other comprehensive income	34.0
Ending balance	1,686.8
ASU 2018-02 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative-effect adjustment related to the adoption of ASU 2018-02 (Please refer to Note 2)	(27.1)
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(207.5)
Other comprehensive income (loss) before income taxes and reclassifications	12.3
Other comprehensive income	12.3
Ending balance	(195.2)
Unrealized Gain (Loss) from Invested Customer Trust Funds [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(18.3)
Other comprehensive income (loss) before income taxes and reclassifications	21.9
Income tax expense	(2.7)
Other comprehensive income	19.2
Ending balance	1.3
Unrealized Gain (Loss) from Invested Customer Trust Funds [Member] \| ASU 2018-02 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative-effect adjustment related to the adoption of ASU 2018-02 (Please refer to Note 2)	0.4
Pension Liability Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(150.1)
Other comprehensive income (loss) before income taxes and reclassifications	(0.1)
Reclassifications to earnings	2.6
Other comprehensive income	2.5
Ending balance	(175.1)
Pension Liability Adjustment [Member] \| ASU 2018-02 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative-effect adjustment related to the adoption of ASU 2018-02 (Please refer to Note 2)	(27.5)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(375.9)
Ending balance	(369.0)
Accumulated Other Comprehensive Income (Loss) [Member] \| ASU 2018-02 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative-effect adjustment related to the adoption of ASU 2018-02 (Please refer to Note 2)	$ (27.1)

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