Business Segment Information (Schedule of Segment Reporting Information) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015	Sep. 30, 2015
Segment Reporting Information [Line Items]
Sales	$ 2,271.2	$ 2,414.5	$ 4,627.0	$ 4,975.3
Operating income (loss)	513.3	376.9	1,023.9	809.2
Depreciation and amortization			464.8	468.8
Equity affiliates' income	32.5	33.0	66.2	76.1
Total assets	16,810.8		16,810.8		$ 17,334.5
Segment Total [Member]
Segment Reporting Information [Line Items]
Sales	2,271.2	2,414.5	4,627.0	4,975.3
Operating income (loss)	531.9	444.9	1,054.5	891.7
Depreciation and amortization	232.1	233.3	464.8	468.8
Equity affiliates' income	32.5	33.0	66.2	76.1
Total assets	16,790.4		16,790.4		16,440.9
Industrial Gases - Americas [Member]
Segment Reporting Information [Line Items]
Sales	797.9	890.4	1,634.0	1,893.4
Operating income (loss)	224.2	182.0	436.0	393.2
Depreciation and amortization	109.4	103.3	218.2	206.9
Equity affiliates' income	7.7	15.1	22.2	32.3
Total assets	5,899.2		5,899.2		5,774.9
Industrial Gases - EMEA [Member]
Segment Reporting Information [Line Items]
Sales	420.3	448.8	858.6	949.6
Operating income (loss)	89.4	71.0	181.1	152.3
Depreciation and amortization	48.3	47.6	95.0	98.7
Equity affiliates' income	7.2	8.0	14.8	18.3
Total assets	3,314.4		3,314.4		3,323.9
Industrial Gases - Asia [Member]
Segment Reporting Information [Line Items]
Sales	406.4	393.0	819.6	791.7
Operating income (loss)	104.4	84.7	221.1	175.2
Depreciation and amortization	48.5	50.3	100.2	99.9
Equity affiliates' income	17.4	9.4	29.1	24.0
Total assets	4,215.5		4,215.5		4,154.0
Industrial Gases - Global [Member]
Segment Reporting Information [Line Items]
Sales	86.6	67.1	190.9	126.1
Operating income (loss)	(10.9)	(7.9)	(30.2)	(25.8)
Depreciation and amortization	1.8	5.5	3.9	9.8
Equity affiliates' income	0.0	(0.2)	(0.5)	0.2
Total assets	278.6		278.6		370.5
Materials Technologies [Member]
Segment Reporting Information [Line Items]
Sales	494.3	533.3	984.3	1,057.3
Operating income (loss)	129.3	124.2	256.5	228.8
Depreciation and amortization	20.0	23.3	39.6	47.3
Equity affiliates' income	0.2	0.7	0.6	1.3
Total assets	1,735.1		1,735.1		1,741.9
Corporate and other [Member]
Segment Reporting Information [Line Items]
Sales	65.7	81.9	139.6	157.2
Operating income (loss)	(4.5)	(9.1)	(10.0)	(32.0)
Depreciation and amortization	4.1	3.3	7.9	6.2
Equity affiliates' income	0.0	$ 0.0	0.0	$ 0.0
Total assets	$ 1,347.6		$ 1,347.6		$ 1,075.7