Goodwill and Acquired Intangible Assets (Goodwill and Acquired Intangible Assets) (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2016	Jul. 02, 2016	Sep. 30, 2015	Sep. 30, 2014
Goodwill (not amortized), Net Book Value		$ 1,169,813	$ 1,169,660	$ 1,069,041	$ 1,012,527
Intangible assets with finite lives (amortized), Gross Carrying Amount		756,132		679,552
Intangible assets with finite lives (amortized), Accumulated Amortization		445,827		388,251
Intangible assets with finite lives (amortized), Net Book Value		310,305		291,301
Total goodwill and acquired intangible assets		1,480,118		1,360,342
Purchased Software [Member]
Intangible assets with finite lives (amortized), Gross Carrying Amount	[1]	354,595		284,257
Intangible assets with finite lives (amortized), Accumulated Amortization	[1]	199,192		174,887
Intangible assets with finite lives (amortized), Net Book Value	[1]	$ 155,403		109,370
Weighted average useful lives (in years)		9 years
Capitalized Software [Member]
Intangible assets with finite lives (amortized), Gross Carrying Amount	[1]	$ 22,877		22,877
Intangible assets with finite lives (amortized), Accumulated Amortization	[1]	22,877		22,877
Intangible assets with finite lives (amortized), Net Book Value	[1]	0		0
Customer Lists [Member]
Intangible assets with finite lives (amortized), Gross Carrying Amount	[1]	355,698		349,938
Intangible assets with finite lives (amortized), Accumulated Amortization	[1]	206,515		174,017
Intangible assets with finite lives (amortized), Net Book Value	[1]	$ 149,183		175,921
Weighted average useful lives (in years)		10 years
Trademarks And Trade Names [Member]
Intangible assets with finite lives (amortized), Gross Carrying Amount	[1]	$ 19,007		18,534
Intangible assets with finite lives (amortized), Accumulated Amortization	[1]	13,323		12,759
Intangible assets with finite lives (amortized), Net Book Value	[1]	$ 5,684		5,775
Weighted average useful lives (in years)		10 years
Other [Member]
Intangible assets with finite lives (amortized), Gross Carrying Amount	[1]	$ 3,955		3,946
Intangible assets with finite lives (amortized), Accumulated Amortization	[1]	3,920		3,711
Intangible assets with finite lives (amortized), Net Book Value	[1]	$ 35		$ 235
Weighted average useful lives (in years)		3 years

[1] The weighted average useful lives of purchased software, capitalized software, customer lists and relationships, trademarks and trade names and other intangible assets with a remaining net book value are 9 years, 10 years, 10 years and 3 years, respectively.