Summary of Derivative Financial Instruments (Detail) (Derivatives Designated as Hedges, USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Derivative [Line Items]
Asset Derivatives Fair Value	$ 5,902	$ 9,291
Liability Derivatives Fair Value	14,194	7,940
Accounts receivable-other
Derivative [Line Items]
Asset Derivatives Fair Value	5,350	6,066
Other assets
Derivative [Line Items]
Asset Derivatives Fair Value	552	3,225
Accounts payable
Derivative [Line Items]
Liability Derivatives Fair Value	11,535	2,207
Other liabilities
Derivative [Line Items]
Liability Derivatives Fair Value	$ 2,659	$ 5,733