Business Segment Information (Schedule of Segment Reporting Information) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Sep. 30, 2016
Segment Reporting Information [Line Items]
Sales	$ 1,980.1	$ 1,777.4	$ 3,862.6	$ 3,643.7
Operating income (loss)	391.2	371.6	719.3	744.1
Depreciation and amortization			417.9	428.6
Equity affiliates' income (loss)	34.2	32.3	72.2	65.6
Total assets	17,871.5		17,871.5		$ 18,028.6
Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales	1,980.1	1,777.4	3,862.6	3,643.7
Operating income (loss)	405.6	391.7	813.9	776.2
Depreciation and amortization	211.8	213.9	417.9	428.6
Equity affiliates' income (loss)	34.2	32.3	72.2	65.6
Total assets	17,861.7		17,861.7		16,060.1
Industrial Gases - Americas [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales	890.1	798.1	1,754.0	1,634.4
Operating income (loss)	224.5	223.5	448.3	435.1
Depreciation and amortization	116.0	109.8	227.8	218.8
Equity affiliates' income (loss)	13.0	7.7	27.7	22.2
Total assets	5,898.8		5,898.8		5,896.7
Industrial Gases - EMEA [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales	414.2	421.8	813.9	861.4
Operating income (loss)	86.5	90.0	174.5	182.3
Depreciation and amortization	41.6	48.2	83.8	95.0
Equity affiliates' income (loss)	8.3	7.2	17.8	14.8
Total assets	3,100.8		3,100.8		3,178.6
Industrial Gases - Asia [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales	435.9	407.9	874.2	822.5
Operating income (loss)	112.0	105.0	230.1	222.3
Depreciation and amortization	49.3	48.8	96.0	100.7
Equity affiliates' income (loss)	12.9	17.4	26.4	29.1
Total assets	4,248.1		4,248.1		4,232.7
Industrial Gases - Global [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales	216.5	86.6	364.4	190.9
Operating income (loss)	22.8	(10.8)	31.0	(30.1)
Depreciation and amortization	1.7	1.8	3.7	3.9
Equity affiliates' income (loss)	0.0	0.0	0.3	(0.5)
Total assets	328.9		328.9		367.6
Corporate and other [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales	23.4	63.0	56.1	134.5
Operating income (loss)	(40.2)	(16.0)	(70.0)	(33.4)
Depreciation and amortization	3.2	5.3	6.6	10.2
Equity affiliates' income (loss)	0.0	$ 0.0	0.0	$ 0.0
Total assets	$ 4,285.1		$ 4,285.1		$ 2,384.5