Property And Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Property, Plant and Equipment [Abstract]
Computer hardware and software	$ 324,765	$ 286,380
Furniture and fixtures	20,737	21,145
Leasehold improvements	47,272	47,658
Gross property and equipment	392,774	355,183
Accumulated depreciation and amortization	(312,161)	(291,583)
Net property and equipment	80,613	63,600	$ 67,113
Depreciation expense	$ 29,400	$ 28,000	$ 28,800