Information Related to Effect of Derivative Instruments on Our Consolidated Condensed Statements of Income (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Derivative Instruments Gain Loss [Line Items]
Gain (loss) on derivatives	$ 1,545	$ 5,950
Commodity Derivatives
Derivative Instruments Gain Loss [Line Items]
Gain (loss) on derivatives	85	(7,161)
Other Comprehensive Income (Loss) | Foreign Currency Derivatives
Derivative Instruments Gain Loss [Line Items]
Gain (loss) on derivatives	1,293	(347)
Other Comprehensive Income (Loss) | Commodity Derivatives
Derivative Instruments Gain Loss [Line Items]
Gain (loss) on derivatives	296
Revaluation of Derivatives | Foreign Currency Derivatives
Derivative Instruments Gain Loss [Line Items]
Gain (loss) on derivatives		6,197
Cost of Sales | Foreign Currency Derivatives
Derivative Instruments Gain Loss [Line Items]
Gain (loss) on derivatives	35	(128)
Cost of Sales | Commodity Derivatives
Derivative Instruments Gain Loss [Line Items]
Gain (loss) on derivatives	(211)	(7,161)
Selling, General and Administrative Expense | Foreign Currency Derivatives
Derivative Instruments Gain Loss [Line Items]
Gain (loss) on derivatives	139	21
Foreign Currency (Loss) Gain | Foreign Currency Derivatives
Derivative Instruments Gain Loss [Line Items]
Gain (loss) on derivatives	$ 78	$ 207