Business Segment Information (Schedule of Segment Reporting Information) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Sep. 30, 2016
Segment Reporting Information [Line Items]
Sales	$ 1,882.5	$ 1,866.3
Operating Income (Loss)	328.1	372.5
Depreciation and amortization	206.1	214.7
Equity affiliates' income (loss)	38.0	33.3
Total assets	15,956.2		$ 18,028.6
Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales	1,882.5	1,866.3
Operating Income (Loss)	408.3	384.5
Depreciation and amortization	206.1	214.7
Equity affiliates' income (loss)	38.0	33.3
Total assets	15,096.0		16,060.1
Industrial Gases - Americas [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales	863.9	836.3
Operating Income (Loss)	223.8	211.6
Depreciation and amortization	111.8	109.0
Equity affiliates' income (loss)	14.7	14.5
Total assets	5,873.9		5,896.7
Industrial Gases - EMEA [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales	399.7	439.6
Operating Income (Loss)	88.0	92.3
Depreciation and amortization	42.2	46.8
Equity affiliates' income (loss)	9.5	7.6
Total assets	3,005.0		3,178.6
Industrial Gases - Asia [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales	438.3	414.6
Operating Income (Loss)	118.1	117.3
Depreciation and amortization	46.7	51.9
Equity affiliates' income (loss)	13.5	11.7
Total assets	4,098.0		4,232.7
Industrial Gases - Global [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales	147.9	104.3
Operating Income (Loss)	8.2	(19.3)
Depreciation and amortization	2.0	2.1
Equity affiliates' income (loss)	0.3	(0.5)
Total assets	268.5		367.6
Corporate and other [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales	32.7	71.5
Operating Income (Loss)	(29.8)	(17.4)
Depreciation and amortization	3.4	4.9
Equity affiliates' income (loss)	0.0	$ 0.0
Total assets	$ 1,850.6		$ 2,384.5