Goodwill and Intangible Assets (Goodwill and Acquired Intangible Assets) (Details) - USD ($) $ in Thousands		3 Months Ended
		Dec. 31, 2016	Sep. 30, 2016
Goodwill (not amortized), Net Book Value		$ 1,159,492	$ 1,169,813
Intangible assets with finite lives (amortized), Gross Carrying Amount	[1]	746,151	756,132
Intangible assets with finite lives (amortized), Accumulated Amortization	[1]	452,424	445,827
Intangible assets with finite lives (amortized), Net Book Value	[1]	293,727	310,305
Intangible Assets, Net (Including Goodwill)		1,453,219	1,480,118
Purchased Software
Intangible assets with finite lives (amortized), Gross Carrying Amount		351,032	354,595
Intangible assets with finite lives (amortized), Accumulated Amortization		202,266	199,192
Intangible assets with finite lives (amortized), Net Book Value	[1]	$ 148,766	155,403
Acquired finite-lived intangible asset, weighted average useful life		9 years
Capitalized Software
Intangible assets with finite lives (amortized), Gross Carrying Amount		$ 22,877	22,877
Intangible assets with finite lives (amortized), Accumulated Amortization		22,877	22,877
Intangible assets with finite lives (amortized), Net Book Value	[1]	0	0
Customer Lists and Relationships
Intangible assets with finite lives (amortized), Gross Carrying Amount		349,593	355,698
Intangible assets with finite lives (amortized), Accumulated Amortization		210,132	206,515
Intangible assets with finite lives (amortized), Net Book Value	[1]	$ 139,461	149,183
Acquired finite-lived intangible asset, weighted average useful life		10 years
Trademarks and Trade Names
Intangible assets with finite lives (amortized), Gross Carrying Amount		$ 18,789	19,007
Intangible assets with finite lives (amortized), Accumulated Amortization		13,289	13,323
Intangible assets with finite lives (amortized), Net Book Value	[1]	$ 5,500	5,684
Acquired finite-lived intangible asset, weighted average useful life		10 years
Other
Intangible assets with finite lives (amortized), Gross Carrying Amount		$ 3,860	3,955
Intangible assets with finite lives (amortized), Accumulated Amortization		3,860	3,920
Intangible assets with finite lives (amortized), Net Book Value	[1]	$ 0	$ 35
Acquired finite-lived intangible asset, weighted average useful life		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.