Other Income, net - Details of Other Income, Net (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Other Income And Expenses [Abstract]
Interest income	$ 3.4	$ 3.3	$ 7.0	$ 6.5
Net foreign exchange transaction gains	5.6	3.1	4.1	2.6
Bank fee expense	(1.5)	(1.3)	(2.9)	(2.4)
Net gain/(loss) on disposals of business and property and equipment	(0.4)	0.5	(1.5)	3.8
Other, net	(1.3)	1.4	(2.2)	2.4
Other income, net	$ 5.8	$ 7.0	$ 4.5	$ 12.9