Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Assets	$ 21.3	[1]	$ 10.3	[1]
Derivative Liabilities	(15.1)	[1]	(18.8)	[1]
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Assets	21.3		10.3
Derivative Liabilities	(15.1)		(18.8)
Available-for-sale securities	20.2		20.0
Level 2 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Assets	21.3		10.3
Derivative Liabilities	(15.1)		(18.8)
Available-for-sale securities	$ 20.2		$ 20.0

[1] Consolidated balance sheet location: Asset: Other current and non-current assets Liability: Other current and non-current liabilities