Reportable Segments Earnings from Equity Method Investments Included in Non-Operating Income and Expense (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Earnings from equity method investments	$ 2.1	$ 3.1	$ 6.7	$ 10.2
U.S. Markets
Segment Reporting Information [Line Items]
Earnings from equity method investments	0.8	0.8	2.0	2.0
International
Segment Reporting Information [Line Items]
Earnings from equity method investments	$ 1.4	$ 2.4	$ 4.7	$ 8.2