Annual report pursuant to Section 13 and 15(d)

Equity-Based Compensation - Performance Stock Units (Details)

v3.23.3
Equity-Based Compensation - Performance Stock Units (Details)
$ in Millions
12 Months Ended
Sep. 30, 2023
USD ($)
shares
Sep. 30, 2022
USD ($)
shares
Sep. 30, 2021
shares
Sep. 30, 2020
shares
Performance Stock Units        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Granted (in shares) 92,423 131,341    
Vested (in shares) 65,024 98,505    
Aggregate grant date fair value of awards | $ $ 2.2      
Performance Stock Units | Minimum        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Percentage of final number of common stock issuable upon vesting of performance stock units 0      
Performance Stock Units | Maximum        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Percentage of final number of common stock issuable upon vesting of performance stock units 1.50      
Percentage increase (decrease) of awards granted due to total shareholder return ranking 0.15      
Performance Stock Units | Equity Incentive Plan | Class A Common Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Compensation expense recorded upon vesting of awards | $ $ 2.0 $ 1.0    
Unrecognized compensation expense at fiscal year-end | $ $ 2.1      
Restricted Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Granted (in shares) 210,412 256,167 510,733  
Vested (in shares) 76,963 134,481 207,706  
Forecasted unvested restricted shares of Class A common stock (in shares) 824,280 715,724 595,561 292,534
Restricted Stock | Class A Common Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Forecasted unvested restricted shares of Class A common stock (in shares) 163,529