Other Income, net - Details of Other Income, Net (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Other Income And Expenses [Abstract]
Interest income	$ 2.6	$ 2.8	$ 9.6	$ 9.3
Net foreign exchange transaction gains	0.6	0.4	4.7	3.0
Bank fee expense	(1.3)	(1.8)	(4.2)	(4.2)
Net gain/(loss) on disposals of business and property and equipment	0.2	(0.2)	(1.3)	3.6
Other, net	(0.9)	4.3	(3.1)	6.7
Other income, net	$ 1.2	$ 5.5	$ 5.7	$ 18.4