Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2013	Mar. 31, 2012	Sep. 30, 2013	Sep. 30, 2012
Income tax
Estimated effective income tax rate (as a percent)	14.00%	14.00%	(16.00%)	14.00%	(16.00%)
Income tax expense (benefit) for discrete items		$ 0	$ 0.6
Net operating loss carryforwards	85.7	85.7
Tax credit carryforwards	24.6	24.6
Minimum
Income tax
Operating loss carryforwards expiration date		2013
Tax credit carryforwards, expiration date		Sep. 30, 2014
Reasonably possible unrecognized income tax benefits primarily related to discontinued operations releasing within the next 12 months	2.0	2.0
Maximum
Income tax
Operating loss carryforwards expiration date		2033
Tax credit carryforwards, expiration date		Sep. 30, 2033
Reasonably possible unrecognized income tax benefits primarily related to discontinued operations releasing within the next 12 months	$ 3.5	$ 3.5