Significant Accounting Policies - Summary of Property and Equipment Balances and Estimated Useful Lives (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Property Plant And Equipment [Line Items]
Total property and equipment, gross	$ 1,009,738	$ 978,913
Accumulated depreciation and amortization	(694,709)	(659,285)
Total property and equipment, net	315,029	319,628	$ 308,357
Land
Property Plant And Equipment [Line Items]
Total property and equipment, gross	10,120	10,061
Buildings and building improvements
Property Plant And Equipment [Line Items]
Total property and equipment, gross	54,521	53,132
Leasehold improvements
Property Plant And Equipment [Line Items]
Total property and equipment, gross	304,404	281,195
Furniture, fixtures and equipment
Property Plant And Equipment [Line Items]
Total property and equipment, gross	$ 640,693	$ 634,525
Minimum | Buildings and building improvements
Property Plant And Equipment [Line Items]
Estimated useful lives	5 years
Minimum | Leasehold improvements
Property Plant And Equipment [Line Items]
Estimated useful lives	2 years
Minimum | Furniture, fixtures and equipment
Property Plant And Equipment [Line Items]
Estimated useful lives	2 years
Maximum | Buildings and building improvements
Property Plant And Equipment [Line Items]
Estimated useful lives	40 years
Maximum | Leasehold improvements
Property Plant And Equipment [Line Items]
Estimated useful lives	10 years
Maximum | Furniture, fixtures and equipment
Property Plant And Equipment [Line Items]
Estimated useful lives	10 years