Other Income (Expense) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Components of other expense
Net loss on disposition of property	$ (0.6)	$ (0.5)	$ (1.0)
Interest income	9.5	9.8	7.8
Royalty income	2.5	3.3	2.3
Environmental charges	(5.2)	(13.5)	(9.3)
Other	3.5	6.6	(4.8)
Other income (expense)	9.7	5.7	(5.0)
Gain from favorable resolutions of certain intellectual property and commercial legal matters	$ 8.0	$ 19.2