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Summary of Significant Accounting Policies - Consolidation and Property and Equipment - Additional Information (Detail) - USD ($)
12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Property and Equipment, Net [Line Items]      
Property Plant And Equipment Depreciation Methods straight-line method    
Immaterial impairment of long-lived assets There was an immaterial impairment of long-lived assets in fiscal years 2023 and 2022 There was an immaterial impairment of long-lived assets in fiscal years 2023 and 2022  
Impairment of long-lived assets     $ 0
Minimum [Member] | Building and Building Improvements [Member]      
Property and Equipment, Net [Line Items]      
Estimated useful life of assets 10 years    
Minimum [Member] | Furniture and Fixtures [Member]      
Property and Equipment, Net [Line Items]      
Estimated useful life of assets 5 years    
Minimum [Member] | Computer, Equipment And Software [Member]      
Property and Equipment, Net [Line Items]      
Estimated useful life of assets 4 years    
Maximum [Member] | Building and Building Improvements [Member]      
Property and Equipment, Net [Line Items]      
Estimated useful life of assets 30 years    
Maximum [Member] | Furniture and Fixtures [Member]      
Property and Equipment, Net [Line Items]      
Estimated useful life of assets 10 years    
Maximum [Member] | Computer, Equipment And Software [Member]      
Property and Equipment, Net [Line Items]      
Estimated useful life of assets 10 years