Other Income, Net - Schedule of Components of Other Income (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Securities earnings:
Dividends and interest			$ 2.8	$ 3.8
Securities transactions, net			0.1	(0.3)
Total	$ 0.9	$ 0.9	2.9	3.5
Currency transactions, net			1.2	3.2
Insurance recoveries				1.6
Infrastructure reimbursement			6.2	19.6
Gain on land and related sales			16.0	4.5
Other, net			1.6	1.5
Total	$ 13.1	$ 2.6	$ 27.9	$ 33.9