Other Income, Net - Schedule of Components of Other Income (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Securities earnings:
Dividends and interest			$ 23.5	$ 21.5
Securities transactions, net			12.6	0.1
Total	$ 19.3	$ 7.5	36.1	21.6
Currency transactions, net			4.2	(8.0)
Insurance recoveries	0.5	0.1	0.9	0.2
Infrastructure reimbursement			4.3	0.7
Gain on land sales			12.5
Other, net			1.8	1.2
Total	$ 20.1	$ 4.3	$ 59.8	$ 15.7