Derivative Financial Instruments (Detail) (Derivatives Designated as Hedges, USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Derivative [Line Items]
Asset Derivatives Fair Value	$ 3,582	$ 2,831
Liability Derivatives Fair Value	15,363	7,860
Accounts receivable-other
Derivative [Line Items]
Asset Derivatives Fair Value	3,582	2,765
Other assets
Derivative [Line Items]
Asset Derivatives Fair Value		66
Accounts payable
Derivative [Line Items]
Liability Derivatives Fair Value	8,177	6,891
Other liabilities
Derivative [Line Items]
Liability Derivatives Fair Value	$ 7,186	$ 969