Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (Quoted Prices in Active Markets for Identical Assets (Level 1), Fair Value, Measurements, Recurring, USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value	$ 10,594
Equity Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value	$ 10,594