Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements - Summary of Cash and Cash Equivalents and Short Term Investments (Detail)

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Fair Value Measurements - Summary of Cash and Cash Equivalents and Short Term Investments (Detail) - USD ($)
$ in Thousands
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]        
Cash, amortized cost and estimated fair value $ 14,034 $ 16,481    
Cash and cash equivalents, amortized cost and estimated fair value 34,310 27,897 $ 14,593 $ 18,075
Restricted cash, amortized cost and estimated fair value 272      
Amortized Cost 20,885 19,179    
Gross Unrealized Gains   1    
Gross Unrealized Losses (9) (20)    
Estimated Fair Value 20,876 19,160    
Restricted cash, amortized cost and estimated fair value   251    
Money market securities [Member]        
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]        
Cash equivalents, amortized cost and estimated fair value 20,276 11,416    
Restricted cash, amortized cost and estimated fair value 272      
Restricted cash, amortized cost and estimated fair value   251    
Corporate bonds and commercial paper [Member]        
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]        
Amortized Cost 20,885 19,179    
Gross Unrealized Gains   1    
Gross Unrealized Losses (9) (20)    
Estimated Fair Value $ 20,876 $ 19,160