Earnings per share (Details) (USD $) In Millions, except Per Share data	3 Months Ended	9 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Earnings Per Share [Abstract]
Net earnings for basic and dilutive earnings per share	$ 65.9	$ 104.0	$ 215.4	$ 318.2
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Weighted-average shares for basic earnings per share	69.7	70.1	70.1	69.9
Effect of dilutive securities:
Stock options	0.2	0.3	0.2	0.3
Restricted stock equivalents	0.7	0.3	0.6	0.3
Total dilutive securities	0.9	0.6	0.8	0.6
Weighted-average shares for diluted earnings per share	70.6	70.7	70.9	70.5
Basic earnings per share	$ 0.95	$ 1.48	$ 3.07	$ 4.55
Diluted earnings per share	$ 0.94	$ 1.47	$ 3.04	$ 4.51
Antidilutive securities excluded from computation of EPS			0.7	1.3

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