Earnings Per Common Share (Details) (USD $) In Millions, except Share data	3 Months Ended								12 Months Ended
	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2009	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Earnings Per Common Share
Net income (loss) attributable to common shareholders	$ 63.5	$ 1.5	$ 33.1	$ 35.2	$ 50.7	$ 30.6	$ 24.2	$ 19.8	$ 133.3	$ 125.3	$ (405.0)
Average shares outstanding - Basic									63,164,000	62,934,000	62,581,000
Add potential effect of exercise of stock options and other unvested equity awards									735,000	805,000
Average shares outstanding - Diluted									63,899,000	63,739,000	62,581,000
Net Income (Loss) Attributable to Common Shareholders per Common Share - Basic	$ 1.01	$ 0.02	$ 0.53	$ 0.56	$ 0.80	$ 0.48	$ 0.38	$ 0.32	$ 2.11	$ 1.99	$ (6.47)
Net Income (Loss) Attributable to Common Shareholders per Common Share - Diluted	$ 1.01	$ 0.02	$ 0.52	$ 0.55	$ 0.79	$ 0.48	$ 0.38	$ 0.31	$ 2.09	$ 1.97	$ (6.47)
Anti-dilutive stock options excluded from the calculation of dilutive earnings per share									600,000	3,400,000	5,800,000