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Stock-Based Compensation - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2016
Mar. 31, 2015
Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Award vesting terms Vesting terms ranging from three to five years and include 1) options that vest in one-fifth increments beginning on the grant date and continuing on each of the first four anniversaries of the grant date and 2) options that cliff-vest on the fifth anniversary of the grant date.    
Stock-based compensation expense $ 3,199 $ 3,901  
1996 Equity Incentive Plan [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Number of shares available for grant under Incentive Plan 2,278,515    
Restricted Stock [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Expiration date of options granted under equity incentive plan 10 years    
Term of director 1 year    
Restricted Stock [Member] | Percentage of awards vesting on grant date [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Percentage of awards vesting on grant date 50.00%    
Restricted Stock [Member] | Percentage of Awards Vesting On Last Day of Each Directors Term [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Percentage of awards vesting on grant date 50.00%    
2009 Employee Stock Purchase Plan [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Number of shares available for grant under Incentive Plan 327,750   279,589
Additional shares reserved under 2009 ESPP 82,084    
Common Class A [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
The Company granted options for an aggregate shares of its Class A common stock 9,000    
Common Class A [Member] | 1996 Equity Incentive Plan [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Shares reserved for issuance to directors and employees 15,500,000    
Common Class A [Member] | Restricted Stock [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Stock-based compensation expense $ 32    
Common Class A [Member] | 2009 Employee Stock Purchase Plan [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Additional shares reserved under 2009 ESPP 82,084    
Performance Based Compensation [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Compensation expense related to performance based compensation agreements $ 670    
Minimum [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Award vesting period 3 years    
Range of awards of target number of share 0.00%    
Maximum [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Award vesting period 5 years    
Range of awards of target number of share 100.00%