Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Summary of Cash, Cash Equivalents and Marketable Securities (Detail)

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Fair Value Measurements - Summary of Cash, Cash Equivalents and Marketable Securities (Detail) - USD ($)
$ in Thousands
Jun. 30, 2015
Dec. 31, 2014
Jun. 30, 2014
Dec. 31, 2013
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]        
Cash, amortized cost and estimated fair value $ 11,036      
Cash and cash equivalents, amortized cost and estimated fair value 48,001 $ 27,897 $ 40,614 $ 14,593
Restricted cash, amortized cost and estimated fair value 190      
Amortized Cost 12,189      
Gross Unrealized Losses (4)      
Estimated Fair Value 12,185      
Money market securities [Member]        
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]        
Cash equivalents, amortized cost and estimated fair value 36,965      
Restricted cash, amortized cost and estimated fair value 190      
Corporate bonds and commercial paper [Member]        
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]        
Amortized Cost 12,189      
Gross Unrealized Losses (4)      
Estimated Fair Value $ 12,185