Stock-Based Compensation (Narrative) (Details) (USD $)	0 Months Ended	12 Months Ended												1 Months Ended				1 Months Ended	12 Months Ended			12 Months Ended
	Oct. 29, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2013 1998 Equity Incentive Plan [Member]	Sep. 30, 2013 2011 Employee Stock Purchase Plan [Member]	Sep. 30, 2013 2000 Equity Incentive Plan [Member]	Sep. 30, 2013 uRoam Acquisition Equity Incentive Plan [Member]	Jul. 31, 2003 uRoam Acquisition Equity Incentive Plan [Member]	Sep. 30, 2013 MagniFire Acquisition Equity Incentive Plan [Member]	Jul. 31, 2004 MagniFire Acquisition Equity Incentive Plan [Member]	Sep. 30, 2013 Acopia Plan [Member]	Sep. 30, 2007 Acopia Plan [Member]	Feb. 29, 2012 Traffix Plan [Member]	Sep. 30, 2013 Traffix Plan [Member]	Sep. 30, 2013 Traffix 2007 Plan [Member] [Member]	Mar. 31, 2013 Traffix 2007 Plan [Member] [Member]	Feb. 28, 2013 LineRate Acquisition Plan [Member]	Sep. 30, 2013 LineRate Acquisition Plan [Member]	Sep. 30, 2013 LineRate 2009 Plan [Member] [Member]	Mar. 31, 2013 LineRate 2009 Plan [Member] [Member]	Sep. 30, 2013 Versafe Acquisition Plan [Member]	Sep. 30, 2013 2005 Equity Incentive Plan [Member]	Sep. 30, 2013 Stock Options [Member]	Sep. 30, 2013 Restricted Stock Unit [Member]	Sep. 30, 2012 Restricted Stock Unit [Member]	Sep. 30, 2011 Restricted Stock Unit [Member]	Sep. 30, 2013 Minimum [Member] Restricted Stock Unit [Member]	Sep. 30, 2013 Maximum [Member] Restricted Stock Unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual equity awards program vesting period																									2 years	2 years	2 years	1 year	4 years
Restricted stock units vesting period in years																									2 years	2 years	2 years	1 year	4 years
Stock option expiration period from date of grant																								10 years
Vesting rate of stock options and awards upon certain changes in ownership control					50.00%		50.00%							50.00%				50.00%				50.00%	50.00%
Shares available for purchase under stock option plan					52,753		40,958	1,650		2,690		12,509				56,758				42,901
Common stock reserved for issuance						6,000,000	7,000,000		500,000		830,000		2,230,703	75,000			106,829	100,000			201,478	60,000	12,400,000
Percentage of base compensation for which employees can acquire shares of common stock						15.00%
Maximum shares allowed for purchase by employee in period						10,000
Maximum aggregate fair value of stock that an employee may purchase						$ 25,000
Share-based compensation award, offering period		6 months	6 months	6 months
Percentage of common stock lesser of the fair market value						85.00%
Stock units issued	1,467,871																								456,837
Outstanding stock units															33,693				100,000				926,035		926,035	1,717,444
Stock options issued during period		52,397																		52,397
Restricted stock units issued																			100,000				456,837
Shares available for award						1,014,179														3,574		60,000	2,135,162
Weighted average fair value of restricted stock units granted																									$ 86.69	$ 99.63	$ 94.99
Fair market value of restricted stock vested																									97,500,000	93,800,000	145,000,000
Total intrinsic value of options exercised		$ 9,800,000	$ 13,200,000	$ 15,200,000