Goodwill and Acquired Intangible Assets (Schedule Of Movements of Goodwill by Reportable Segment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Goodwill [Roll Forward]
Balance, beginning of period	$ 1,182,772	$ 1,169,813
Goodwill acquired	4,350	2,847
Foreign currency translation and other adjustments	(4,665)	10,112
Balance, end of period	1,182,457	1,182,772
Software Products [Member]
Goodwill [Roll Forward]
Balance, beginning of period	1,152,917	1,140,215
Goodwill acquired	4,350	2,847
Foreign currency translation and other adjustments	(4,547)	9,855
Balance, end of period	1,152,720	1,152,917
Professional Services [Member]
Goodwill [Roll Forward]
Balance, beginning of period	29,855	29,598
Goodwill acquired	0	0
Foreign currency translation and other adjustments	(118)	257
Balance, end of period	$ 29,737	$ 29,855