Property and Equipment - Schedule of Property and Equipment, at Cost (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024
Property and equipment
Total	$ 1,141,600	$ 1,061,200
Accumulated depreciation and amortization	(725,400)	(706,800)
Property and equipment, net	416,164	354,377
Building and land
Property and equipment
Total	$ 10,500	10,100
Building and land \| Minimum
Property and equipment
Useful Lives (years)	10 years
Building and land \| Maximum
Property and equipment
Useful Lives (years)	45 years
Leasehold improvements
Property and equipment
Total	$ 275,000	299,300
Leasehold improvements \| Minimum
Property and equipment
Useful Lives (years)	1 year
Leasehold improvements \| Maximum
Property and equipment
Useful Lives (years)	20 years
Computer systems and equipment
Property and equipment
Total	$ 770,400	659,600
Computer systems and equipment \| Minimum
Property and equipment
Useful Lives (years)	3 years
Computer systems and equipment \| Maximum
Property and equipment
Useful Lives (years)	12 years
Furniture and fixtures
Property and equipment
Total	$ 85,700	$ 92,200
Furniture and fixtures \| Minimum
Property and equipment
Useful Lives (years)	3 years
Furniture and fixtures \| Maximum
Property and equipment
Useful Lives (years)	10 years

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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