Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)	12 Months Ended												0 Months Ended	39 Months Ended	0 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2014 Minimum [Member]	Sep. 30, 2014 Maximum [Member]	Sep. 30, 2014 Hardware [Member]	Sep. 30, 2014 Computer Software, Intangible Asset [Member]	Sep. 30, 2013 Computer Software, Intangible Asset [Member]	Sep. 30, 2012 Computer Software, Intangible Asset [Member]	Sep. 30, 2014 Computer Software, Intangible Asset [Member] Defense.net [Member]	Sep. 30, 2013 Computer Software, Intangible Asset [Member] Versafe [Member]	Sep. 30, 2012 Computer Software, Intangible Asset [Member] Traffix Systems [Member]	Jan. 22, 2014 October Twenty Six Two Thousand Ten Program [Member]	Jan. 20, 2014 October Twenty Six Two Thousand Ten Program [Member]	Nov. 20, 2014 Subsequent Event [Member]
Goodwill
Goodwill, Subsequent Recognition of Deferred Tax Asset	$ (6,116,000)
Other Assets
Acquired and developed technology and customer relationship assets estimated useful lives							5 years
Acquired technology in connection with the acquisitions										3,600,000	15,400,000	14,900,000
Amortization expense related to acquired technology	9,500,000	4,300,000	6,400,000				7,900,000	3,800,000	5,300,000
Revenue Recognition
Domestic accounts receivable terms of payment				30 days	45 days
International accounts receivable terms of payment				30 days	120 days
VSOE Percentage Which Constitutes Substantial Majority of Transactions Priced Within a Narrow Range	80.00%
Range of VSOE to median sales price	15.00%
Guarantees and Product Warranties
Standard product warranty period						1 year
Advertising
Advertising costs	3,600,000	2,800,000	1,800,000
Common Stock Repurchase
Common stock share repurchase program, amount authorized													500,000,000	1,100,000,000
Shares repurchased and retired															18,449,755
Shares repurchased and retired, average price per share															$ 82.41
Stock repurchase program, remaining amount															$ 279,600,000