Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Sep. 30, 2013	Sep. 30, 2012
Income tax
Estimated effective income tax rate (as a percent)	12.00%	(14.00%)	12.00%	(14.00%)
Income tax expense (benefit) for discrete items		$ 0.6
Net operating loss and capital carryforwards	74.5
Tax credit carryforwards	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
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