Customer Trust Fund - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Investments Debt And Equity Securities [Abstract]
Investment income from invested customer trust fund included in revenue	$ 19.6	$ 24.3

Investment Income From Invested Customer Trust Fund

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration