Fair Value Measurements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Fair Value, Measurement Inputs, Disclosure [Line Items]
Derivative instrument maturity term (in months)	1 month
Notional amount of foreign exchange forward contracts	$ 409.0	$ 103.3
Foreign currency forward contracts, fair value net gain (loss)	0.7	(0.1)
Difference between carrying amount and fair value of long-term debt	6		37
Prepaid Expenses and Other Current Assets
Fair Value, Measurement Inputs, Disclosure [Line Items]
Foreign currency forward contract fair value, assets	0.9	0.2
Other Accrued Liabilities
Fair Value, Measurement Inputs, Disclosure [Line Items]
Foreign currency forward contract fair value, liabilities	0.2	0.3
Other Income Expense Net
Fair Value, Measurement Inputs, Disclosure [Line Items]
Gain on foreign exchange forward contracts	$ 2.3	$ 1.8