Other Income (Expense), net - Details of Other Income (Expense), Net (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Other Income And Expenses [Abstract]
Interest and dividend income	$ 2.8	$ 4.3	$ 9.3	$ 10.8
Net foreign exchange transaction gains (losses)	0.4	(3.7)	3.0	(8.3)
Bank fee expense	(1.8)	(1.0)	(4.2)	(4.3)
Net gain on disposals of property and equipment and other	(0.2)		3.6
Other, net	4.3	4.9	6.7	7.6
Other income (expense), net	$ 5.5	$ 4.5	$ 18.4	$ 5.8