Summary of Financial Instruments Measured at Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Income Statement Hedge
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Valuation Technique	Market approach - Uses prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities
Income Statement Hedge | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments measured at fair value	(483)
Marketable Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Valuation Technique	Market approach - Uses prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities	Market approach - Uses prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities
Balance Sheet Hedge
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Valuation Technique	Market approach - Uses prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities