Income Taxes - Reconciliation of Unrecognized Tax Benefits (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Reconciliation of Unrecognized Tax Benefits
Unrecognized tax benefits - beginning of year	$ 3.4	$ 2.9	$ 6.3
Additions for tax positions of the current year	0.7	0.7	0.5
Additions for tax positions taken in prior years	0	0	0.6
Settlements with tax authorities	(1.7)	(0.2)	(4.5)
Unrecognized tax benefits - end of year	$ 2.4	$ 3.4	$ 2.9