Other Income, Net - Schedule of Components of Other Income (Detail) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Dec. 31, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Securities earnings:
Dividends and interest				$ 29.4	$ 26.7	$ 26.4
Securities transactions, net				0.1	0.5
Total				29.5	27.2	26.4
Insurance recoveries				0.4	0.4	3.7
Currency transactions, net				(7.5)	5.5	(0.1)
Disposal of property and equipment, net				(0.5)	(0.3)	(0.8)
Business interruption insurance proceeds	$ 0.9	$ 1.4	$ 2.0		4.3
Infrastructure reimbursement				1.0	0.6	0.2
Other, net				2.3	1.3	2.5
Total				$ 25.2	$ 39.0	$ 31.9