Summary of Financial Instruments Measured at Fair Value (Detail) (Income Statement Hedge, USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Dec. 31, 2011
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
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)