Earnings per Share (Details) (USD $)
In Millions, except Per Share data, unless otherwise specified
3 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended
Sep. 30, 2012
Jun. 30, 2012
Mar. 31, 2012
Dec. 31, 2011
Sep. 30, 2011
Jun. 30, 2011
Mar. 31, 2011
Dec. 31, 2010
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2010
May 29, 2012
Restricted Stock Units (RSUs) [Member]
May 29, 2012
Stock Options [Member]
Sep. 30, 2012
Restricted Stock [Member]
Sep. 30, 2011
Restricted Stock [Member]
Sep. 30, 2010
Restricted Stock [Member]
Feb. 03, 2012
Restricted Stock [Member]
Sep. 30, 2012
Stock Appreciation Rights (SARs) [Member]
Sep. 30, 2011
Stock Appreciation Rights (SARs) [Member]
Sep. 30, 2010
Stock Appreciation Rights (SARs) [Member]
Sep. 07, 2012
Stock Appreciation Rights (SARs) [Member]
Feb. 03, 2012
Stock Appreciation Rights (SARs) [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]                                            
Equity Instruments Granted In Spinoff Transaction                                 0.1         0.3
Net Income (Loss) Attributable to Parent $ 10.8 $ 15.8 $ 10.5 $ 12.8 $ (479.6) $ 1.6 $ 29.1 $ 24.6 $ 49.9 $ (424.3) $ 92.0                      
Weighted Average Number of Shares Outstanding, Basic                 34.3 34.4 34.4                      
Incremental Common Shares Attributable to Share-based Payment Arrangements                 0.2 0 0     0.1 0 0   0.1 0 0    
Weighted Average Number of Shares Outstanding, Diluted                 34.5 34.4 34.4                      
Earnings Per Share, Basic $ 0.32 $ 0.46 $ 0.31 $ 0.37 $ (13.94) $ 0.05 $ 0.85 $ 0.72 $ 1.45 $ (12.33) $ 2.67                      
Earnings Per Share, Diluted $ 0.31 $ 0.46 $ 0.30 $ 0.37 $ (13.94) $ 0.05 $ 0.85 $ 0.72 $ 1.45 $ (12.33) $ 2.67                      
Shares, Issued                       0.4 1.8               0.1