Business Segment and Geographic Information (Schedule of Segment Reporting Information) (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]
Sales	$ 2,449.4	$ 2,470.2	$ 2,414.5	$ 2,560.8	$ 2,677.0	$ 2,634.6	$ 2,581.9	$ 2,545.5	$ 9,894.9	$ 10,439.0	$ 10,180.4
Operating income (loss)	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
Depreciation and amortization									936.4	956.9	907.0
Equity affiliates' income									154.5	151.4	167.8
Expenditures for long-lived assets									1,614.8	1,684.2	1,524.2
Investment in net assets of and advances to equity affiliates	1,265.7				1,257.9				1,265.7	1,257.9
Total assets	17,438.1				17,779.1				17,438.1	17,779.1
Segment Total [Member]
Segment Reporting Information [Line Items]
Sales									9,894.9	10,439.0	10,180.4
Operating income (loss)									1,884.0	1,656.5	1,566.1
Depreciation and amortization									936.4	956.9	907.0
Equity affiliates' income									154.5	151.4	167.8
Expenditures for long-lived assets									1,614.8	1,684.2	1,524.2
Investment in net assets of and advances to equity affiliates	1,265.7				1,257.9				1,265.7	1,257.9	1,195.5
Total assets	17,438.1				17,779.1				17,438.1	17,779.1	17,847.6
Industrial Gases - Americas [Member]
Segment Reporting Information [Line Items]
Sales									3,693.9	4,078.5	3,866.1
Operating income (loss)									808.4	762.6	776.7
Depreciation and amortization									416.9	414.4	409.8
Equity affiliates' income									64.6	60.9	70.9
Expenditures for long-lived assets									414.5	484.2	438.2
Investment in net assets of and advances to equity affiliates	249.7				234.3				249.7	234.3	195.9
Total assets	5,774.9				6,240.7				5,774.9	6,240.7	6,666.5
Industrial Gases - EMEA [Member]
Segment Reporting Information [Line Items]
Sales									1,864.9	2,150.7	2,102.8
Operating income (loss)									330.7	351.2	331.2
Depreciation and amortization									194.3	220.2	202.6
Equity affiliates' income									42.4	44.1	47.7
Expenditures for long-lived assets									215.6	239.1	216.4
Investment in net assets of and advances to equity affiliates	564.1				552.9				564.1	552.9	545.8
Total assets	3,323.9				3,521.0				3,323.9	3,521.0	3,694.7
Industrial Gases - Asia [Member]
Segment Reporting Information [Line Items]
Sales									1,637.5	1,527.0	1,613.9
Operating income (loss)									380.5	310.4	329.3
Depreciation and amortization									202.9	205.3	174.9
Equity affiliates' income									46.1	38.0	45.0
Expenditures for long-lived assets									402.5	430.3	389.5
Investment in net assets of and advances to equity affiliates	421.7				434.1				421.7	434.1	418.7
Total assets	4,154.0				4,045.6				4,154.0	4,045.6	3,766.6
Industrial Gases - Global [Member]
Segment Reporting Information [Line Items]
Sales									286.8	296.0	309.0
Operating income (loss)									(51.6)	(57.3)	(56.5)
Depreciation and amortization									16.5	7.1	5.5
Equity affiliates' income									(0.8)	5.8	1.4
Expenditures for long-lived assets									94.8	77.7	70.3
Investment in net assets of and advances to equity affiliates	14.3				18.8				14.3	18.8	17.5
Total assets	370.5				389.4				370.5	389.4	365.5
Materials Technologies [Member]
Segment Reporting Information [Line Items]
Sales									2,087.1	2,064.6	1,870.3
Operating income (loss)									476.7	379.0	279.5
Depreciation and amortization									92.8	99.1	107.7
Equity affiliates' income									2.2	2.6	2.8
Expenditures for long-lived assets									102.5	64.2	58.1
Investment in net assets of and advances to equity affiliates	15.9				17.8				15.9	17.8	17.6
Total assets	1,741.9				1,835.7				1,741.9	1,835.7	1,864.6
Energy-from-Waste [Member]
Segment Reporting Information [Line Items]
Sales									0.0	0.0	0.0
Operating income (loss)									(10.1)	(12.4)	(9.8)
Depreciation and amortization									0.0	0.0	0.0
Equity affiliates' income									0.0	0.0	0.0
Expenditures for long-lived assets									349.2	321.5	290.9
Investment in net assets of and advances to equity affiliates	0.0				0.0				0.0	0.0	0.0
Total assets	894.4				591.9				894.4	591.9	297.5
Corporate and other [Member]
Segment Reporting Information [Line Items]
Sales									324.7	322.2	418.3
Operating income (loss)									(50.6)	(77.0)	(84.3)
Depreciation and amortization									13.0	10.8	6.5
Equity affiliates' income									0.0	0.0	0.0
Expenditures for long-lived assets									35.7	67.2	60.8
Investment in net assets of and advances to equity affiliates	0.0				0.0				0.0	0.0	0.0
Total assets	$ 1,178.5				$ 1,154.8				$ 1,178.5	$ 1,154.8	$ 1,192.2