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 6 Months Ended 3 Months Ended 6 Months Ended 0 Months Ended 6 Months Ended
Jun. 30, 2014
Jun. 30, 2013
Jun. 30, 2014
Jun. 30, 2013
Jun. 30, 2014
Employee Stock-Based Compensation Expense
Jun. 30, 2013
Employee Stock-Based Compensation Expense
Jun. 30, 2014
Employee Stock-Based Compensation Expense
Jun. 30, 2013
Employee Stock-Based Compensation Expense
May 15, 2014
2004 Equity Incentive Plan
Jun. 30, 2014
2004 Equity Incentive Plan
Jun. 30, 2014
2004 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Stock-based compensation expense $ 1,468,000 $ 1,272,000 $ 2,734,000 $ 2,325,000 $ 1,500,000 $ 1,200,000 $ 2,700,000 $ 2,200,000      
Unrecognized compensation cost related to unvested stock-based awards granted to employees under the stock option plans         12,700,000   12,700,000        
Unrecognized compensation cost related to unvested stock-based awards granted to employees under the stock option plans, period for recognition             2 years 8 months 12 days        
Non-employee stock-based compensation expense 19,000 34,000 55,000 100,000              
Additional shares authorized for issuance                 6,626,157 1,250,000 100,000
Shares authorized for issuance under the 2014 Equity Incentive Plan                   6,000,000  
Remaining shares available for issuance                   4,446,294 261,834
Total intrinsic value of stock options exercised     200,000 400,000              
Cash received from stock option exercises     100,000 200,000              
Plan participants purchased shares                     74,062
Average purchase price under 2004 Employee Stock Purchase Plan                     $ 3.91
Cash proceeds                     $ 300,000