Goodwill and Acquired Intangible Assets (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2012 segments	Sep. 30, 2012 Software Products Segment [Member]	Sep. 30, 2011 Software Products Segment [Member]	Sep. 30, 2012 Services Segment [Member]	Sep. 30, 2011 Services Segment [Member]
Number of reportable segments	2
Goodwill and acquired intangible assets		$ 768.1	$ 806.0	$ 28.1	$ 29.4
Estimated aggregate future amortization expense for intangible assets, 2013	36.0
Estimated aggregate future amortization expense for intangible assets, 2014	34.1
Estimated aggregate future amortization expense for intangible assets, 2015	30.6
Estimated aggregate future amortization expense for intangible assets, 2016	23.1
Estimated aggregate future amortization expense for intangible assets, 2017	19.5
Estimated aggregate future amortization expense for intangible assets, thereafter	$ 42.6