Business Segment Information (Schedule of Segment Reporting Information) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014	Sep. 30, 2014
Segment Reporting Information [Line Items]
Sales	$ 2,414.5us-gaap_SalesRevenueNet	$ 2,581.9us-gaap_SalesRevenueNet	$ 4,975.3us-gaap_SalesRevenueNet	$ 5,127.4us-gaap_SalesRevenueNet
Operating income (loss)	374.4us-gaap_OperatingIncomeLoss	384.7us-gaap_OperatingIncomeLoss	804.4us-gaap_OperatingIncomeLoss	770.3us-gaap_OperatingIncomeLoss
Depreciation and amortization			468.8	463.3
Equity affiliates' income (loss)	33.0	30.4	76.1	68.6
Total assets	17,493.8us-gaap_Assets		17,493.8us-gaap_Assets		17,779.1us-gaap_Assets
Segment Total [Member]
Segment Reporting Information [Line Items]
Sales	2,414.5	2,581.9	4,975.3	5,127.4
Operating income (loss)	442.4	384.7	886.9	770.3
Depreciation and amortization	233.3	229.1	468.8	463.3
Equity affiliates' income (loss)	33.0	30.4	76.1	68.6
Total assets	17,493.8		17,493.8		17,779.1
Industrial Gases - Americas [Member]
Segment Reporting Information [Line Items]
Sales	890.4	1,032.9	1,893.4	1,976.8
Operating income (loss)	182.0	169.6	393.2	354.1
Depreciation and amortization	103.3	99.4	206.9	203.4
Equity affiliates' income (loss)	15.1	12.6	32.3	30.2
Total assets	6,074.5		6,074.5		6,240.7
Industrial Gases - EMEA [Member]
Segment Reporting Information [Line Items]
Sales	448.8	542.7	949.6	1,092.6
Operating income (loss)	71.0	87.5	152.3	172.7
Depreciation and amortization	47.6	55.0	98.7	109.9
Equity affiliates' income (loss)	8.0	9.3	18.3	19.0
Total assets	3,131.6		3,131.6		3,521.0
Industrial Gases - Asia [Member]
Segment Reporting Information [Line Items]
Sales	393.0	365.7	791.7	761.0
Operating income (loss)	84.7	71.2	175.2	153.9
Depreciation and amortization	50.3	48.1	99.9	94.5
Equity affiliates' income (loss)	9.4	7.6	24.0	17.2
Total assets	4,174.3		4,174.3		4,045.6
Industrial Gases - Global [Member]
Segment Reporting Information [Line Items]
Sales	67.1	68.4	126.1	135.6
Operating income (loss)	(7.9)	(14.6)	(25.8)	(24.9)
Depreciation and amortization	5.5	1.6	9.8	3.3
Equity affiliates' income (loss)	(0.2)	0.3	0.2	1.0
Total assets	338.8		338.8		389.4
Materials Technologies [Member]
Segment Reporting Information [Line Items]
Sales	533.3	499.6	1,057.3	979.1
Operating income (loss)	124.2	93.8	228.8	158.1
Depreciation and amortization	23.3	22.7	47.3	47.2
Equity affiliates' income (loss)	0.7	0.6	1.3	1.2
Total assets	1,801.2		1,801.2		1,835.7
Energy-from-Waste [Member]
Segment Reporting Information [Line Items]
Sales	0	0	0	0
Operating income (loss)	(2.8)	(3.5)	(5.3)	(6.4)
Depreciation and amortization	0	0	0	0
Equity affiliates' income (loss)	0	0	0	0
Total assets	724.8		724.8		591.9
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Sales	81.9	72.6	157.2	182.3
Operating income (loss)	(8.8)	(19.3)	(31.5)	(37.2)
Depreciation and amortization	3.3	2.3	6.2	5.0
Equity affiliates' income (loss)	0	0	0	0
Total assets	$ 1,248.6		$ 1,248.6		$ 1,154.8

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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