Fair Value Measurements - Fair Value, Assets Measured on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Cash Equivalents [Member] | Carrying Amount [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total cash equivalents and investments	$ 1,267	$ 1,000
Certificates of Deposit [Member] | Carrying Amount [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total cash equivalents and investments	2,000
Short-Term Debt Securities [Member] | Carrying Amount [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total cash equivalents and investments	9,695
Long-Term Equity Securities [Member] | Carrying Amount [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total cash equivalents and investments	772
Level 1 [Member] | Cash Equivalents [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total cash equivalents and investments	1,267	1,000
Level 1 [Member] | Certificates of Deposit [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total cash equivalents and investments
Level 1 [Member] | Short-Term Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total cash equivalents and investments	9,695
Level 1 [Member] | Long-Term Equity Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total cash equivalents and investments	772
Level 2 [Member] | Cash Equivalents [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total cash equivalents and investments
Level 2 [Member] | Certificates of Deposit [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total cash equivalents and investments	2,000
Level 2 [Member] | Short-Term Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total cash equivalents and investments
Level 2 [Member] | Long-Term Equity Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total cash equivalents and investments
Fair Value, Inputs, Level 3 [Member] | Cash Equivalents [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total cash equivalents and investments
Fair Value, Inputs, Level 3 [Member] | Certificates of Deposit [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total cash equivalents and investments
Fair Value, Inputs, Level 3 [Member] | Short-Term Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total cash equivalents and investments
Fair Value, Inputs, Level 3 [Member] | Long-Term Equity Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total cash equivalents and investments