Business Segment and Geographic Information (Schedule of Segment Reporting Information) (Details) - USD ($) $ 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
Segment Reporting Information [Line Items]
Sales	$ 2,463.0	$ 2,434.4	$ 2,271.2	$ 2,355.8	$ 2,449.4	$ 2,470.2	$ 2,414.5	$ 2,560.8	$ 9,524.4	$ 9,894.9	$ 10,439.0
Operating income (loss)	547.0	$ 535.1	$ 513.3	$ 510.6	474.3	$ 424.8	$ 376.9	$ 432.3	2,106.0	1,708.3	1,339.1
Depreciation and amortization									925.9	936.4	956.9
Equity affiliates' income									148.6	154.5	151.4
Expenditures for long-lived assets									1,055.8	1,265.6	1,362.7
Investment in net assets of and advances to equity affiliates	1,288.1				1,265.7				1,288.1	1,265.7
Total assets	18,055.3				17,334.5				18,055.3	17,334.5	17,668.3
Segment Total [Member]
Segment Reporting Information [Line Items]
Sales									9,524.4	9,894.9	10,439.0
Operating income (loss)									2,198.5	1,893.2	1,667.4
Depreciation and amortization									925.9	936.4	956.9
Equity affiliates' income									148.6	154.5	151.4
Expenditures for long-lived assets									1,055.8	1,265.6	1,362.7
Investment in net assets of and advances to equity affiliates	1,288.1				1,265.7				1,288.1	1,265.7	1,257.9
Total assets	18,035.9				16,440.9				18,035.9	16,440.9	17,076.9
Industrial Gases - Americas [Member]
Segment Reporting Information [Line Items]
Sales									3,343.6	3,693.9	4,078.5
Operating income (loss)									895.2	808.4	762.6
Depreciation and amortization									442.5	416.9	414.4
Equity affiliates' income									52.7	64.6	60.9
Expenditures for long-lived assets									406.6	414.5	484.2
Investment in net assets of and advances to equity affiliates	250.6				249.7				250.6	249.7	234.3
Total assets	5,889.2				5,774.9				5,889.2	5,774.9	6,240.7
Industrial Gases - EMEA [Member]
Segment Reporting Information [Line Items]
Sales									1,700.3	1,864.9	2,150.7
Operating income (loss)									382.8	330.7	351.2
Depreciation and amortization									185.7	194.3	220.2
Equity affiliates' income									36.5	42.4	44.1
Expenditures for long-lived assets									159.5	215.6	239.1
Investment in net assets of and advances to equity affiliates	580.5				564.1				580.5	564.1	552.9
Total assets	3,178.6				3,323.9				3,178.6	3,323.9	3,521.0
Industrial Gases - Asia [Member]
Segment Reporting Information [Line Items]
Sales									1,716.1	1,637.5	1,527.0
Operating income (loss)									449.1	380.5	310.4
Depreciation and amortization									197.1	202.9	205.3
Equity affiliates' income									57.8	46.1	38.0
Expenditures for long-lived assets									313.3	402.5	430.3
Investment in net assets of and advances to equity affiliates	442.5				421.7				442.5	421.7	434.1
Total assets	4,232.7				4,154.0				4,232.7	4,154.0	4,045.6
Industrial Gases - Global [Member]
Segment Reporting Information [Line Items]
Sales									498.8	286.8	296.0
Operating income (loss)									(21.3)	(51.6)	(57.3)
Depreciation and amortization									7.9	16.5	7.1
Equity affiliates' income									(0.1)	(0.8)	5.8
Expenditures for long-lived assets									6.0	94.8	77.7
Investment in net assets of and advances to equity affiliates	10.0				14.3				10.0	14.3	18.8
Total assets	367.6				370.5				367.6	370.5	389.4
Materials Technologies [Member]
Segment Reporting Information [Line Items]
Sales									2,019.5	2,087.1	2,064.6
Operating income (loss)									530.2	476.7	379.0
Depreciation and amortization									77.4	92.8	99.1
Equity affiliates' income									1.7	2.2	2.6
Expenditures for long-lived assets									147.9	102.5	64.2
Investment in net assets of and advances to equity affiliates	4.5				15.9				4.5	15.9	17.8
Total assets	1,787.0				1,741.9				1,787.0	1,741.9	1,835.7
Corporate and other [Member]
Segment Reporting Information [Line Items]
Sales									246.1	324.7	322.2
Operating income (loss)									(37.5)	(51.5)	(78.5)
Depreciation and amortization									15.3	13.0	10.8
Equity affiliates' income									0.0	0.0	0.0
Expenditures for long-lived assets									22.5	35.7	67.2
Investment in net assets of and advances to equity affiliates	0.0				0.0				0.0	0.0	0.0
Total assets	$ 2,580.8				$ 1,075.7				$ 2,580.8	$ 1,075.7	$ 1,044.5