Summary of Notional Amounts of Outstanding Foreign Exchange Forwards, Cash Flow Hedging (Detail) In Millions, unless otherwise specified	Sep. 30, 2012 Foreign Currency Forward Contracts To Purchase U S Dollars With Euros USD ($)	Dec. 31, 2011 Foreign Currency Forward Contracts To Purchase U S Dollars With Euros USD ($)	Sep. 30, 2012 Foreign Currency Forward Contracts To Sell U S Dollars For Euros USD ($)	Dec. 31, 2011 Foreign Currency Forward Contracts To Sell U S Dollars For Euros USD ($)	Sep. 30, 2012 Foreign Currency Forward Contracts To Purchase U S Dollars With GBP USD ($)	Dec. 31, 2011 Foreign Currency Forward Contracts To Purchase U S Dollars With GBP USD ($)	Sep. 30, 2012 Foreign Currency Forward Contracts To Sell U S Dollars For GBP USD ($)	Dec. 31, 2011 Foreign Currency Forward Contracts To Sell U S Dollars For GBP USD ($)	Sep. 30, 2012 Foreign Currency Forward Contracts To Purchase U S Dollars With Other Foreign Currencies USD ($)	Dec. 31, 2011 Foreign Currency Forward Contracts To Purchase U S Dollars With Other Foreign Currencies USD ($)	Sep. 30, 2012 Foreign Currency Forward Contracts To Sell U S Dollars For Other Foreign Currencies USD ($)	Dec. 31, 2011 Foreign Currency Forward Contracts To Sell U S Dollars For Other Foreign Currencies USD ($)	Sep. 30, 2012 Foreign Currency Forward Contracts To Purchase Euros With Other Foreign Currencies EUR (€)	Dec. 31, 2011 Foreign Currency Forward Contracts To Purchase Euros With Other Foreign Currencies EUR (€)	Sep. 30, 2012 Foreign Currency Forward Contracts To Purchase Euros With GBP EUR (€)	Dec. 31, 2011 Foreign Currency Forward Contracts To Purchase Euros With GBP EUR (€)	Sep. 30, 2012 Foreign Currency Forward Contracts To Sell Euros For GBP EUR (€)	Dec. 31, 2011 Foreign Currency Forward Contracts To Sell Euros For GBP EUR (€)
Derivative [Line Items]
Contracts to purchase foreign currencies	$ 34.6	$ 27.5			$ 4.2	$ 2.4			$ 8.7	$ 3.2			€ 20.7	€ 13.6	€ 8.7	€ 1.6
Contracts to sell foreign currencies			$ 47.1	$ 47.7			$ 4.2	$ 17.6			$ 6.5	$ 7.6					€ 9.9	€ 7.2