Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	$ 15.0	$ 126.5
Term deposits	6.8	413.7
Interest rate swaps	0.5
Total assets measured at fair value	22.3	540.2
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	15.0	126.5
Total assets measured at fair value	15.0	126.5
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Term deposits	6.8	413.7
Interest rate swaps	0.5
Total assets measured at fair value	$ 7.3	$ 413.7