Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 13.8	$ 13.5
Assets, Fair Value, Total	57.1	62.4
Derivative Liabilities, Fair Value		(1.6)
Liabilities, Fair Value, Total	(2.3)	(1.6)
Hedging contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value	43.3	48.9
Derivative Liabilities, Fair Value	(2.3)
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	13.8	13.5
Assets, Fair Value, Total	13.8	13.5
Liabilities, Fair Value, Total
Quoted Prices in Active Markets for Identical Assets (Level 1) | Hedging contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value
Derivative Liabilities, Fair Value
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities
Assets, Fair Value, Total	43.3	48.9
Derivative Liabilities, Fair Value		(1.6)
Liabilities, Fair Value, Total	(2.3)	(1.6)
Significant Other Observable Inputs (Level 2) | Hedging contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value	43.3	48.9
Derivative Liabilities, Fair Value	(2.3)
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities
Assets, Fair Value, Total
Liabilities, Fair Value, Total
Significant Unobservable Inputs (Level 3) | Hedging contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value
Derivative Liabilities, Fair Value