Derivative Financial Instruments - Fair Value of Outstanding Forward and Zero Cost Collar Recorded as Assets (Detail) (Derivative designated as hedging instruments [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Other current assets [Member] | Zero cost collars [Member]
Asset Derivatives:
Derivatives designated as hedging instruments, Asset	$ 4,912	$ 1,458
Derivative liabilities [Member] | Zero cost collars [Member]
Liabilities Derivatives:
Derivatives designated as hedging instruments, Liability		944	2,956
Derivative liabilities [Member] | Forward [Member]
Liabilities Derivatives:
Derivatives designated as hedging instruments, Liability			$ 6,801