Basis of Presentation and Accounting Policies (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Reconciled Basic and Diluted EPS
Net income	$ 201.3	$ 206.1	$ 206.0	$ 214.2	$ 248.7	$ 199.7	$ 180.3	$ 198.1	$ 827.6	$ 826.8	$ 756.3
Less: Allocation to participating securities									(0.7)	(1.1)	(1.1)
Net income available to common shareowners									$ 826.9	$ 825.7	$ 755.2
Basic weighted average outstanding shares									134.5	138.0	139.2
Effect of dilutive securities
Stock options									1.1	1.5	1.5
Performance shares									0.1	0.2	0.2
Diluted weighted average outstanding shares									135.7	139.7	140.9
Basic earnings per share:
Basic	$ 1.51	$ 1.53	$ 1.53	$ 1.58	$ 1.81	$ 1.44	$ 1.30	$ 1.43	$ 6.15	$ 5.98	$ 5.43
Diluted earnings per share:
Diluted	$ 1.50	$ 1.52	$ 1.51	$ 1.56	$ 1.79	$ 1.43	$ 1.28	$ 1.41	$ 6.09	$ 5.91	$ 5.36