Property And Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Property, Plant and Equipment [Abstract]
Computer hardware and software	$ 267,928	$ 246,756
Furniture and fixtures	20,742	18,370
Leasehold improvements	43,769	38,005
Gross property and equipment	332,439	303,131
Accumulated depreciation and amortization	(265,326)	(237,969)
Net property and equipment	67,113	65,162	$ 67,783
Depreciation expense	$ 28,800	$ 28,900	$ 27,100