Goodwill and Acquired Intangible Assets (Narrative) (Details) $ in Millions	12 Months Ended
	Sep. 30, 2015 USD ($) segments	Sep. 30, 2014 USD ($)
Number of reportable segments | segments	2
Estimated aggregate future amortization expense for intangible assets, 2016	$ 49.9
Estimated aggregate future amortization expense for intangible assets, 2017	47.8
Estimated aggregate future amortization expense for intangible assets, 2018	46.1
Estimated aggregate future amortization expense for intangible assets, 2019	38.4
Estimated aggregate future amortization expense for intangible assets, 2020	35.4
Estimated aggregate future amortization expense for intangible assets, thereafter	73.7
Software Products [Member]
Goodwill and acquired intangible assets	1,297.9	$ 1,283.0
Services [Member]
Goodwill and acquired intangible assets	$ 62.4	$ 66.4