Other Current Assets (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid expenses	$ 92.3	$ 84.1
Other investments	44.0	30.7
Income taxes receivable	22.5	19.0
Other receivables	19.1	15.2
Marketable securities (Note 2)	3.0	2.9
Contract assets	1.9	1.4
Deferred financing fees (Note 8)	0.5	0.5
Other	11.3	16.4
Total other current assets	$ 194.6	$ 170.2