Quarterly report pursuant to Section 13 or 15(d)

Financial Instruments - Financial Instruments Measured on Recurring Basis (Detail)

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Financial Instruments - Financial Instruments Measured on Recurring Basis (Detail) (USD $)
In Thousands, unless otherwise specified
Jun. 30, 2014
Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, available-for-sale securities $ 60,468 $ 60,311
Money market funds [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, available-for-sale securities 208 406
Fair Value Measurements Recurring [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, available-for-sale securities 60,468 60,311
Fair Value Measurements Recurring [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | US Government Agencies Debt Securities [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, available-for-sale securities 23,464 26,537
Fair Value Measurements Recurring [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Corporate debt securities [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, available-for-sale securities 36,796 33,368
Fair Value Measurements Recurring [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Money market funds [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, available-for-sale securities 208 406
Fair Value Measurements Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, available-for-sale securities 208 406
Fair Value Measurements Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | US Government Agencies Debt Securities [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, available-for-sale securities 0 0
Fair Value Measurements Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate debt securities [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, available-for-sale securities 0 0
Fair Value Measurements Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Money market funds [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, available-for-sale securities 208 406
Fair Value Measurements Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, available-for-sale securities 60,260 59,905
Fair Value Measurements Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | US Government Agencies Debt Securities [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, available-for-sale securities 23,464 26,537
Fair Value Measurements Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate debt securities [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, available-for-sale securities 36,796 33,368
Fair Value Measurements Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Money market funds [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, available-for-sale securities 0 0
Fair Value Measurements Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, available-for-sale securities 0 0
Fair Value Measurements Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | US Government Agencies Debt Securities [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, available-for-sale securities 0 0
Fair Value Measurements Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Corporate debt securities [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, available-for-sale securities 0 0
Fair Value Measurements Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Money market funds [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, available-for-sale securities $ 0 $ 0