Business Segment and Geographic Information (Schedule of Income Information) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended																		12 Months Ended
	Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2012
Segment Reporting Information [Line Items]
Business restructuring and cost reduction actions	$ (12.7)	[1]	$ 0	[1]	$ 0	[1]	$ 0	[1]	$ (231.6)	[1]	$ 0	[1]	$ 0	[1]	$ 0	[1]			$ (12.7)	[1],[2]	$ (231.6)	[1],[2]	$ (327.4)	[1],[2]
Pension settlement loss	(5.5)	[3]	0	[3]	0	[3]	0	[3]	(7.9)	[3]	(4.5)	[3]	0	[3]	0	[3]			(5.5)	[3]	(12.4)	[3]	0	[3]
Goodwill and intangible asset impairment charge	(310.1)	[4]	0	[4]	0	[4]	0	[4]											(310.1)	[4]	0	[4]	0	[4]
Customer bankruptcy																	(9.8)	[5]	0		0		(9.8)
Advisory costs									(10.1)	[5]	0	[5]	0	[5]	0	[5]			0		(10.1)	[5]	0
Operating income	144.1		413.8		384.7		385.6		179.2		383.1		389.7		372.4				1,328.2		1,324.4		1,282.4
Depreciation and amortization																			956.9		907.0		840.8
Equity affiliates' income																			151.4		167.8		153.8
Segment Total [Member]
Segment Reporting Information [Line Items]
Operating income																			1,670.0		1,583.2		1,626.2
Depreciation and amortization																			956.1		906.0		839.9
Equity affiliates' income																			151.4		167.8		153.8
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Business restructuring and cost reduction actions																			(12.7)	[2]	(231.6)	[2]	(327.4)	[2]
Pension settlement loss																			(5.5)		(12.4)		0
Goodwill and intangible asset impairment charge																			(310.1)		0		0
Customer bankruptcy																			0		0		(9.8)
Advisory costs																			0		(10.1)		0
Other																			(13.5)		(4.7)		(6.6)
Other Non-Segment [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization																			0.8		1.0		0.9
Merchant Gases [Member]
Segment Reporting Information [Line Items]
Operating income																			671.6		680.5		644.0
Depreciation and amortization																			461.1		409.5		363.2
Equity affiliates' income																			140.1		145.0		137.1
Segments other than Merchant Gases [Member]
Segment Reporting Information [Line Items]
Equity affiliates' income																			11.3		22.8		16.7
Tonnage Gases [Member]
Segment Reporting Information [Line Items]
Operating income																			484.9		515.9		512.0
Depreciation and amortization																			310.8		314.8		320.4
Electronics and Performance Materials [Member]
Segment Reporting Information [Line Items]
Operating income																			425.3	[6]	321.3	[6]	425.6	[6]
Depreciation and amortization																			171.8		173.4		144.1
Equipment and Energy [Member]
Segment Reporting Information [Line Items]
Operating income																			88.2		65.5		44.6
Depreciation and amortization																			$ 12.4		$ 8.3		$ 12.2

[1] For additional information, see Note 4, Business Restructuring and Cost Reduction Actions.

[2] Information about how this charge related to the businesses at the segment level is discussed in Note 4, Business Restructuring and Cost Reduction Actions.

[3] For additional information, see Note 15, Retirement Benefits.

[4] For additional information, see Note 9, Goodwill and Note 10, Intangible Assets.

[5] For additional information, see Note 23, Supplemental Information.

[6] The gain on remeasuring our previously held equity interest in DA NanoMaterials is included in 2012. For additional information, see Note 5, Business Combinations.