Earnings per share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share [Abstract]
Net earnings for basic and dilutive earnings per share	$ 107.9	$ 129.8
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Weighted-average shares - basic	62.5	61.8
Effect of dilutive securities:
Stock options	0.1	0.1
Restricted stock equivalents	0.5	0.7
Total dilutive securities	0.6	0.8
Weighted-average shares - diluted	63.1	62.6
Basic net earnings per share	$ 1.73	$ 2.10
Diluted net earnings per share	$ 1.71	$ 2.07
Antidilutive securities excluded from computation of EPS	0	0.4