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Stock Compensation - Additional Information (Detail) - USD ($)
$ in Millions
1 Months Ended 9 Months Ended
Jun. 30, 2014
Jun. 30, 2009
Jun. 30, 2008
Sep. 30, 2015
Sep. 30, 2014
Dec. 31, 1997
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock options, expiration period       10 years    
Stock Option Plan 2014            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares available for awards under the plan       9,473,048    
Employee Stock Purchase Plan            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Reserved common stock for issuance under the plan           500,000
Additional shares of common stock reserved 750,000 750,000 500,000      
Payroll withholding period for purchase of shares of common stock     3 months      
Shares of common stock issued under the plan       193,178 185,243  
Minimum | Employee Stock Purchase Plan            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Purchase price of common stock by employees     85.00%      
Stock options            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock options, expiration period       10 years    
Stock options | Minimum            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock options, vesting period       3 years    
Stock options | Maximum            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock options, vesting period       4 years    
Stock and stock units            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Total fair value of stock and stock unit awards vested       $ 9.2 $ 4.9  
Restricted shares or units            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Unrecognized compensation expense       $ 16.8    
Weighted average period of compensation cost expected to be recognized       1 year 7 months 6 days    
Performance share units | Maximum            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Percentage of Compensation Expense       60.00%