Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 8,248	$ 13,492
Assets, Fair Value, Total	14,175	62,346
Liabilities, Fair Value, Total	8,223	1,679
Hedging contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value	5,927	48,854
Derivative Liabilities, Fair Value	8,223	1,679
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	8,248	13,492
Assets, Fair Value, Total	8,248	13,492
Liabilities, Fair Value, Total
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Hedging contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value
Derivative Liabilities, Fair Value
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities
Assets, Fair Value, Total	5,927	48,854
Liabilities, Fair Value, Total	8,223	1,679
Significant Other Observable Inputs (Level 2) [Member] | Hedging contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value	5,927	48,854
Derivative Liabilities, Fair Value	8,223	1,679
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities
Assets, Fair Value, Total
Liabilities, Fair Value, Total
Significant Unobservable Inputs (Level 3) [Member] | Hedging contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Fair Value
Derivative Liabilities, Fair Value