Incentive Award Plan and Employee Stock Purchase Plan (Details) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended		3 Months Ended		9 Months Ended		0 Months Ended
	May 15, 2013	Mar. 04, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 2010 Employee Stock Purchase Plan (ESPP)	Mar. 30, 2013 2010 Employee Stock Purchase Plan (ESPP)	May 15, 2013 Performance Based Award installment	May 15, 2013 Restricted Stock Units (RSUs) installment	Mar. 04, 2013 Chief Executive Officer	Mar. 04, 2013 Chief Executive Officer Performance Based Award installment	Jun. 30, 2013 Other Executive Officers	Mar. 04, 2013 Other Executive Officers	Jun. 30, 2013 Other Executive Officers Performance Shares 2012 [Member]	Mar. 04, 2013 Other Executive Officers Performance Based Award	Jun. 30, 2013 Other Executive Officers Restricted Stock Units (RSUs) installment	Mar. 04, 2013 Other Executive Officers Restricted Stock Units (RSUs) installment	Jun. 30, 2013 Other Executive Officers Performance Shares 2013 [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments
Share-based awards, grant date fair market value	$ 2.6	$ 3.2									$ 1.0	$ 0.5	$ 0.9	$ 2.0	$ 0.3	$ 1.0	$ 0.5	$ 1.0	$ 0.1
Share-based awards, grants in period	99,900	143,182							59,942	39,958
Share-based awards, number of equal vesting components									12	8		3					3	3
Employee stock purchase plan shares issued during period							98,872	104,328
Allocated Share-based Compensation Expense			$ 4.2	$ 3.1	$ 10.2	$ 6.5