Quarterly report pursuant to Section 13 or 15(d)

Stock Based Compensation - Additional Information (Detail)

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Stock Based Compensation - Additional Information (Detail) (USD $)
 3 Months Ended 9 Months Ended 0 Months Ended 9 Months Ended
Sep. 30, 2014
Sep. 30, 2013
Sep. 30, 2014
Sep. 30, 2013
Sep. 30, 2014
Employee Stock-Based Compensation Expense
Sep. 30, 2014
2004 Equity Incentive Plan
May 15, 2014
2014 Equity Incentive Plan
Sep. 30, 2014
2014 Equity Incentive Plan
Sep. 30, 2014
2004 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Stock-based compensation expense $ 1,198,000 $ 1,231,000 $ 3,932,000 $ 3,556,000          
Unrecognized compensation cost related to unvested stock-based awards granted to employees under the stock option plans         11,500,000        
Unrecognized compensation cost related to unvested stock-based awards granted to employees under the stock option plans, period for recognition         2 years 7 months 6 days        
Non-employee stock-based compensation expense 17,000 36,000 73,000 100,000          
Additional shares authorized for issuance           1,250,000 6,626,157   100,000
Shares authorized for issuance under the 2014 Equity Incentive Plan             6,000,000    
Remaining shares available for issuance               4,425,554 180,904
Total intrinsic value of stock options exercised     200,000 500,000          
Cash received from stock option exercises     100,000 200,000          
Plan participants purchased shares                 154,992
Average purchase price under 2004 Employee Stock Purchase Plan                 $ 3.74
Cash proceeds                 $ 600,000