Basis of Presentation and Accounting Policies (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012	Mar. 31, 2011
Reconciled Basic and Diluted EPS
Net income	$ 167.8	$ 166.4	$ 351.1	$ 316.5
Less: Allocation to participating securities	(0.3)	(0.3)	(0.7)	(0.7)
Net income available to common shareowners	$ 167.5	$ 166.1	$ 350.4	$ 315.8
Basic weighted average outstanding shares	142.5	143.4	142.1	142.6
Effect of dilutive securities
Stock options	1.9	2.5	1.8	2.4
Performance shares	0.3	0.4	0.4	0.4
Diluted weighted average outstanding shares	144.7	146.3	144.3	145.4
Earnings per share:
Basic	$ 1.18	$ 1.16	$ 2.47	$ 2.21
Diluted	$ 1.16	$ 1.14	$ 2.43	$ 2.17