Goodwill and Acquired Intangible Assets (Amortization Of Intangible Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of acquired intangible assets	$ 32,108	$ 33,198	$ 36,129
Cost of license and subscription	26,621	24,604	19,402
Total amortization expense	$ 58,729	$ 57,802	$ 55,531