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Stock-based Compensation - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Feb. 09, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock-based compensation number of shares authorized     5,000,000
Stock-based compensation, increase number of additional shares to be effective upon its approval by shareholders 4,850,000    
Stock-based compensation number of shares available for awards 680,568,000    
Restricted Stock Awards [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Percentage of shares that will vest 100.00%    
Stock Options [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Non-qualified options granted expiration period 10 years    
Vesting period 3 years    
Allocated stock-based compensation expense $ 1.1 $ 1.0  
Unrecognized compensation cost related to unvested stock $ 8.1    
Unrecognized compensation cost related to unvested stock, expected weighted-average period of recognition 2 years 2 months 12 days    
Restricted Stock Units (RSUs) [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Allocated stock-based compensation expense $ 4.1 $ 2.4  
Unrecognized compensation cost related to unvested stock $ 22.3    
Unrecognized compensation cost related to unvested stock, expected weighted-average period of recognition 2 years 2 months 12 days    
Restricted Stock Units (RSUs) [Member] | Minimum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Percentage of shares that will vest 0.00%    
Restricted Stock Units (RSUs) [Member] | Maximum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Percentage of shares that will vest 200.00%