Fair Value of Derivatives Not Designated and Designated as Hedges (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Derivatives Fair Value [Line Items]
Derivatives assets	$ 10.6	$ 15.3
Not Designated as Hedging Instrument | Prepaid Expenses and Other Current Assets
Derivatives Fair Value [Line Items]
Derivatives assets	0.2	0.6
Not Designated as Hedging Instrument | Accrued Liabilities
Derivatives Fair Value [Line Items]
Derivatives liabilities	4.3	24.0
Designated as Hedging Instrument | Other Noncurrent Assets
Derivatives Fair Value [Line Items]
Derivatives assets	$ 10.4	$ 14.7