Derivative Financial Instruments - Impact of Derivative Instruments on Consolidated Statement of Operations (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Derivative [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion)	$ 4,019	$ (16,289)	$ 3,374	$ (10,213)
Amount of Gain (Loss) Reclassified from AOCI into Statement of Income (Effective Portion)	(2,783)	1,536	(4,312)	11,478
Amount of Gain (Loss) Recognized in Statement of Income on Derivatives (Ineffective Portion and Amount Excluded from Effectiveness Testing)	695	(558)	1,481	(197)
Forward [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion)	2,338	(8,044)	1,953	(5,337)
Forward [Member] | Other income (expenses) - Others [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Statement of Income on Derivatives (Ineffective Portion and Amount Excluded from Effectiveness Testing)	619	171	1,132	435
Forward [Member] | Net sales [Member]
Derivative [Line Items]
Amount of Gain (Loss) Reclassified from AOCI into Statement of Income (Effective Portion)	(2,783)		(2,783)	10,771
Zero Cost Collars [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion)	1,681	(8,245)	1,421	(4,791)
Zero Cost Collars [Member] | Other income (expenses) - Others [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Statement of Income on Derivatives (Ineffective Portion and Amount Excluded from Effectiveness Testing)	76	(729)	349	(614)
Zero Cost Collars [Member] | Net sales [Member]
Derivative [Line Items]
Amount of Gain (Loss) Reclassified from AOCI into Statement of Income (Effective Portion)		1,536	(1,529)	1,536
Options [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion)				(85)
Options [Member] | Other income (expenses) - Others [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Statement of Income on Derivatives (Ineffective Portion and Amount Excluded from Effectiveness Testing)				(18)
Options [Member] | Net sales [Member]
Derivative [Line Items]
Amount of Gain (Loss) Reclassified from AOCI into Statement of Income (Effective Portion)				$ (829)