Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Summary of Marketable Securities (Detail)

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Fair Value Measurements - Summary of Marketable Securities (Detail) (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2013
Dec. 31, 2012
Sep. 30, 2012
Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Cash, amortized cost and estimated fair value $ 5,723      
Cash and cash equivalents, amortized cost and estimated fair value 12,950 18,075 11,362 28,517
Restricted cash, amortized cost and estimated fair value 314 314    
Corporate bonds and commercial paper [Member]
       
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Amortized Cost 33,829      
Gross Unrealized Gains 3      
Gross Unrealized Losses (5)      
Estimated Fair Value 33,827      
Total short-term investments [Member]
       
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Amortized Cost 33,829      
Gross Unrealized Gains 3      
Gross Unrealized Losses (5)      
Estimated Fair Value 33,827      
Money market securities [Member]
       
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Money market securities, amortized cost and estimated fair value 7,227      
Restricted cash, amortized cost and estimated fair value $ 314