Stock-based Compensation Plans (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended		3 Months Ended	6 Months Ended	12 Months Ended		6 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013 Phantom Share Units (PSUs) [Member]	Mar. 31, 2014 Phantom Share Units (PSUs) [Member]	Dec. 31, 2013 Performance Shares [Member]	Mar. 31, 2014 Performance Shares [Member]	Sep. 30, 2013 Performance Shares [Member]	Mar. 31, 2014 Cash-settled Performance Shares [Member]	Mar. 31, 2014 Minimum [Member] Performance Shares [Member]	Mar. 31, 2014 Maximum [Member] Performance Shares [Member]
Performance Factor											0	2
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period					304,815		272,531
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Intrinsic Value, Amount Per Share								$ 9.50
Share-based compensation liability						$ 2.4				$ 2.8
Allocated Share-based Compensation Expense	2.0	3.3	6.1	5.6
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value								$ 8.52	$ 5.22
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	$ 7.8		$ 7.8
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,087,649	1,634,143	1,159,708	1,539,933