Fair Value of Financial Instruments - Fair Value of Gross Position of Derivative Contracts in Condensed Consolidated Balance Sheets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012 Accrued Liabilities [Member]	Jun. 30, 2013 Other Current Assets [Member]	Dec. 31, 2012 Designated as Hedging Instruments [Member] Accrued Liabilities [Member]	Dec. 31, 2012 Designated as Hedging Instruments [Member] Accrued Liabilities [Member] Gross Amounts Recognized [Member]	Dec. 31, 2012 Designated as Hedging Instruments [Member] Accrued Liabilities [Member] Gross Amounts Offset [Member]	Jun. 30, 2013 Designated as Hedging Instruments [Member] Other Current Assets [Member]	Jun. 30, 2013 Designated as Hedging Instruments [Member] Other Current Assets [Member] Gross Amounts Recognized [Member]	Jun. 30, 2013 Designated as Hedging Instruments [Member] Other Current Assets [Member] Gross Amounts Offset [Member]	Dec. 31, 2012 Not Designated as Hedging Instruments [Member] Accrued Liabilities [Member]	Dec. 31, 2012 Not Designated as Hedging Instruments [Member] Accrued Liabilities [Member] Gross Amounts Recognized [Member]	Jun. 30, 2013 Not Designated as Hedging Instruments [Member] Other Current Assets [Member]	Jun. 30, 2013 Not Designated as Hedging Instruments [Member] Other Current Assets [Member] Gross Amounts Recognized [Member]	Jun. 30, 2013 Not Designated as Hedging Instruments [Member] Other Current Assets [Member] Gross Amounts Offset [Member]
Derivatives, Fair Value [Line Items]
Derivatives (Assets)/ liabilities as hedging instruments	$ (1,265)	$ 3,104	$ (1,510)	$ (2,610)	$ 1,100	$ 3,492	$ 4,270	$ (778)	$ 245	$ 245	$ (388)	$ (443)	$ 55