Basis of Presentation and Accounting Policies (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Reconciled Basic and Diluted EPS
Net income	$ 185.2	$ 191.0	$ 168.0	$ 185.5	$ 201.3	$ 206.1	$ 206.0	$ 214.2	$ 729.7	$ 827.6	$ 826.8
Less: Allocation to participating securities									(0.7)	(0.7)	(1.1)
Net income available to common shareowners									$ 729.0	$ 826.9	$ 825.7
Basic weighted average outstanding shares									130.2	134.5	138.0
Effect of dilutive securities
Stock options									0.9	1.1	1.5
Performance shares									0.0	0.1	0.2
Diluted weighted average outstanding shares									131.1	135.7	139.7
Basic earnings per share:
Basic	$ 1.44	$ 1.47	$ 1.29	$ 1.41	$ 1.51	$ 1.53	$ 1.53	$ 1.58	$ 5.60	$ 6.15	$ 5.98
Diluted earnings per share:
Diluted	$ 1.43	$ 1.46	$ 1.28	$ 1.40	$ 1.50	$ 1.52	$ 1.51	$ 1.56	$ 5.56	$ 6.09	$ 5.91