Information Relate to Effect of Derivative Instruments on Our Consolidated Income Statements (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives	$ (1,265)	$ 1,984
Revaluation Of Derivatives | Foreign Currency Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives	(974)	1,087
Revaluation Of Derivatives | Currency Related Swap
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives	1,320	147
Revaluation Of Derivatives | Commodity derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives		126
Foreign Currency Gain (Loss) | Foreign Currency Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives	(291)	897
Interest Expense | Interest Rate Swap
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives	(1)	(28)
Other Comprehensive Income (Loss)
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives	$ 39	$ (33)