Business Segment and Geographic Information (Reconciliation of Operating Income) (Details) - USD ($) $ 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
Segment Reporting Information [Line Items]
Business restructuring and cost reduction actions	$ (61.7)	[1]	$ (58.2)	[1]	$ (55.4)	[1]	$ (32.4)	[1]	$ (12.7)	[1]	$ 0.0	[1]	$ 0.0	[1]	$ 0.0	[1]	$ (207.7)	[1]	$ (12.7)	[1]	$ (231.6)
Pension settlement loss	(7.0)	[2]	(1.6)	[2]	(12.6)	[2]	0.0	[2]	(5.5)	[2]	0.0	[2]	0.0	[2]	0.0	[2]	(21.2)	[2]	(5.5)	[2]	(12.4)
Goodwill and intangible asset impairment charge									(310.1)	[3]	0.0	[3]	0.0	[3]	0.0	[3]	0.0		(310.1)	[3]	0.0
Business separation costs	(7.5)	[4]	0.0	[4]	0.0	[4]	0.0	[4]									(7.5)	[4]	0.0		0.0
Gain on previously held equity interest	0.0	[5]	0.0	[5]	0.0	[5]	17.9	[5]									17.9	[5]	0.0		0.0
Advisory costs																	0.0		0.0		(10.1)
Gain on land sales																	37.1		9.7		20.0
Operating Income	472.2		422.5		374.4		430.0		$ 144.1		$ 413.8		$ 384.7		$ 385.6		1,699.1		1,328.2		1,324.4
Segment Total [Member]
Segment Reporting Information [Line Items]
Operating Income																	1,884.0		1,656.5		1,566.1
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Business restructuring and cost reduction actions																	(207.7)		(12.7)		(231.6)
Pension settlement loss																	(21.2)		(5.5)		0.0
Goodwill and intangible asset impairment charge																	0.0		(310.1)		0.0
Business separation costs																	(7.5)		0.0		0.0
Gain on previously held equity interest																	17.9		0.0		0.0
Advisory costs																	0.0		0.0		(10.1)
Gain on land sales	$ 33.6	[6]	$ 0.0	[6]	$ 0.0	[6]	$ 0.0	[6]									$ 33.6	[6],[7]	$ 0.0	[7]	$ 0.0	[7]

[1] For additional information, see Note 5, Business Restructuring and Cost Reduction Actions.

[2] For additional information, see Note 16, Retirement Benefits.

[3] For additional information, see Note 10, Goodwill, and Note 11, Intangible Assets.

[4] For additional information, see Note 3, Materials Technologies Separation.

[5] For additional information, see Note 6, Business Combinations.

[6] The gain is reflected on the consolidated income statements in “Other income (expense), net.” For additional information, see Note 24, Supplemental Information.

[7] Reflected on the consolidated income statements in "Other income (expense), net."