Fair Value Measurements of Financial Assets and Liabilities (Detail) (Short Term Investments and Cash Equivalents, USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - Overnight Investments	$ 1,283	$ 3,190
Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - Overnight Investments
Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - Overnight Investments	$ 1,283	$ 3,190