Goodwill and Intangible Assets (Schedule Of Intangible Assets Subject To Amortization) (Details) - USD ($) $ in Millions	6 Months Ended
	Mar. 31, 2017	Sep. 30, 2016
Finite-Lived Intangible Assets [Line Items]
Total intangible assets, Gross Carrying Amount	$ 230.3	$ 213.9
Total intangible assets, Accumulated Amortization	(162.4)	(146.9)
Total intangible assets, Net Carrying Amount	67.9	67.0
Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Indefinite-Lived Trademarks	1.6	1.6
Nonamortizing intangible assets, Gross Carrying Amount	$ 1.6	1.6
Customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period (Years)	5 years
Gross Carrying Amount	$ 78.5	78.5
Accumulated Amortization	(61.1)	(57.7)
Net Carrying Amount	$ 17.4	20.8
Developed technology and other [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period (Years)	5 years
Gross Carrying Amount	$ 150.2	133.8
Accumulated Amortization	(101.3)	(89.2)
Net Carrying Amount	$ 48.9	$ 44.6