Goodwill and Acquired Intangible Assets (Goodwill and Acquired Intangible Assets) (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Goodwill (not amortized), Net Book Value		$ 1,069,041	$ 1,012,527	$ 769,095
Intangible assets with finite lives (amortized), Gross Carrying Amount		679,552	684,015
Intangible assets with finite lives (amortized), Accumulated Amortization		388,251	347,142
Intangible assets with finite lives (amortized), Net Book Value		291,301	336,873
Total goodwill and acquired intangible assets		1,360,342	1,349,400
Purchased Software [Member]
Intangible assets with finite lives (amortized), Gross Carrying Amount	[1]	284,257	278,012
Intangible assets with finite lives (amortized), Accumulated Amortization	[1]	174,887	162,259
Intangible assets with finite lives (amortized), Net Book Value	[1]	$ 109,370	115,753
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]	349,938	360,530
Intangible assets with finite lives (amortized), Accumulated Amortization	[1]	174,017	147,469
Intangible assets with finite lives (amortized), Net Book Value	[1]	$ 175,921	213,061
Weighted average useful lives (in years)		10 years
Trademarks And Trade Names [Member]
Intangible assets with finite lives (amortized), Gross Carrying Amount	[1]	$ 18,534	18,479
Intangible assets with finite lives (amortized), Accumulated Amortization	[1]	12,759	10,964
Intangible assets with finite lives (amortized), Net Book Value	[1]	$ 5,775	7,515
Weighted average useful lives (in years)		10 years
Other [Member]
Intangible assets with finite lives (amortized), Gross Carrying Amount	[1]	$ 3,946	4,117
Intangible assets with finite lives (amortized), Accumulated Amortization	[1]	3,711	3,573
Intangible assets with finite lives (amortized), Net Book Value	[1]	$ 235	$ 544
Weighted average useful lives (in years)		3 years

[1] The weighted average useful lives of purchased 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.