Derivative Financial Instruments - Impact of Derivative Instruments on Consolidated Statement of Operations (Detail) - Cash Flow Hedging [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion)	$ 7,736	$ (1,032)
Other Income, Net [Member]
Derivative [Line Items]
Amount of Gain (loss) Recognized in Statement of Operations on Derivatives (Ineffective Portion)	236	(272)
Net Sales [Member]
Derivative [Line Items]
Amount of Gain (loss) Reclassified from AOCI into Statement of Operations (Effective Portion)	2,001
Zero Cost Collars [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion)	4,692	(1,032)
Zero Cost Collars [Member] | Other Income, Net [Member]
Derivative [Line Items]
Amount of Gain (loss) Recognized in Statement of Operations on Derivatives (Ineffective Portion)	606	(272)
Zero Cost Collars [Member] | Net Sales [Member]
Derivative [Line Items]
Amount of Gain (loss) Reclassified from AOCI into Statement of Operations (Effective Portion)	1,501	$ (637)
Forward [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion)	3,044
Forward [Member] | Other Income, Net [Member]
Derivative [Line Items]
Amount of Gain (loss) Recognized in Statement of Operations on Derivatives (Ineffective Portion)	(370)
Forward [Member] | Net Sales [Member]
Derivative [Line Items]
Amount of Gain (loss) Reclassified from AOCI into Statement of Operations (Effective Portion)	$ 500