Derivative Financial Instruments (Detail) (Derivatives Designated as Hedges, USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Derivative [Line Items]
Asset Derivatives Fair Value	$ 17,260	$ 2,831
Liability Derivatives Fair Value	9,986	7,860
Accounts receivable-other
Derivative [Line Items]
Asset Derivatives Fair Value	9,524	2,765
Other assets
Derivative [Line Items]
Asset Derivatives Fair Value	7,736	66
Accounts payable
Derivative [Line Items]
Liability Derivatives Fair Value	8,344	6,891
Other liabilities
Derivative [Line Items]
Liability Derivatives Fair Value	$ 1,642	$ 969