Annual report pursuant to Section 13 and 15(d)

Equity-based Compensation - Additional Information (Detail)

v3.10.0.1
Equity-based Compensation - Additional Information (Detail) - USD ($)
1 Months Ended 12 Months Ended
Feb. 23, 2018
Mar. 07, 2017
Aug. 22, 2016
Jun. 30, 2018
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Sale of treasury stock           $ 638,000  
Proceeds from sale of stock options           $ 600,000.0  
Treasury shares issued (in dollars per share)           $ 3.64  
Increase in number of shares (in shares)         $ 98,009,000    
Additional Paid-in Capital              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Sale of treasury stock         (453,000)    
Increase in number of shares (in shares)         98,000,000    
Restricted Stock              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Shares granted (in shares) 126,000            
Weighted-average exercise price (in dollars per share) $ 0.04            
Proceeds from sale of shares $ 5,000            
Sale of treasury stock $ 500,000            
Grant date fair value of shares (in dollars per share) $ 7.78            
Compensation expense         1,000,000    
Unrecognized compensation expense         $ 0    
2017 Non-Plan Option              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Options outstanding (in shares)         74,592    
Options granted (in shares)   74,592          
Exercises in period, weighted average (in dollars per share)   $ 0.04          
Weighted average fair value of options (in dollars per share)   $ 5.52          
2017 Non-Plan Option | Options              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Unrecognized compensation expense         $ 400,000    
Award vesting rights, percentage   100.00%          
Share price (in dollars per share)         $ 5.56    
2016 Equity Incentive Plan              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Options outstanding (in shares)         0 0 189,050
Options granted (in shares)     252,000   0 0  
Exercises in period, weighted average (in dollars per share)     $ 3.37        
Weighted average fair value of options (in dollars per share)     $ 2.90        
Aggregate intrinsic value           $ 400,000  
Options outstanding (in shares)         0 0 189,000
2016 Equity Incentive Plan | Options              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Compensation expense         $ 0 $ 500,000  
Unrecognized compensation expense         $ 0 $ 0  
Share price (in dollars per share)         $ 4.97    
2010 non-plan stock option agreement options              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Options forfeited (in shares)           0  
Adjustments related to tax withholding for share-based compensation       $ 2,500,000      
2010 non-plan stock option agreement options | Additional Paid-in Capital              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Amount of repurchase price retained       $ 4,400,000      
Class B Common Stock | 2010 non-plan stock option agreement options              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Shares granted (in shares)         768,984    
Options granted (in shares)       768,984      
Exercises in period, weighted average (in dollars per share)       $ 5.70 $ 5.70    
Treasury shares issued (in dollars per share)       $ 3.64 $ 3.64    
Treasury stock acquired (in shares)       521,902      
Increase in number of shares (in shares)       $ 247,082      
Class A Common Stock              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Increase in number of shares (in shares)         $ 9,000    
Class A Common Stock | 2010 non-plan stock option agreement options              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share price (in dollars per share)       $ 13.17