Summary by Quarter (Unaudited) (Details) - USD ($) $ / shares in Units, $ 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
Quarterly Financial Information Disclosure [Abstract]
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
Gross profit	752.3		753.8		714.9		729.8		744.6		715.9		664.3		679.6		2,950.8		2,804.4
Business restructuring and cost reduction actions	61.7	[1]	58.2	[1]	55.4	[1]	32.4	[1]	12.7	[1]	0.0	[1]	0.0	[1]	0.0	[1]	207.7	[1]	12.7	[1]	231.6
Pension settlement loss	7.0	[2]	1.6	[2]	12.6	[2]	0.0	[2]	5.5	[2]	0.0	[2]	0.0	[2]	0.0	[2]	21.2	[2]	5.5	[2]	12.4
Goodwill and intangible asset impairment charge									310.1	[3]	0.0	[3]	0.0	[3]	0.0	[3]	0.0		310.1	[3]	0.0
Business separation costs	7.5	[4]	0.0	[4]	0.0	[4]	0.0	[4]									7.5	[4]	0.0		0.0
Gain on previously held equity interest	0.0	[5]	0.0	[5]	0.0	[5]	17.9	[5]									17.9	[5]	0.0		0.0
Gain on land sales																	37.1		9.7		20.0
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
Loss on early retirement of debt	16.6	[6]	0.0	[6]	0.0	[6]	0.0	[6]									16.6	[6]	0.0		0.0
Net income	350.0		333.2		296.9		337.5		79.0		323.5		291.5		299.1		1,317.6		993.1		1,032.5
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest [Abstract]
Income from continuing operations attributable to Air Products	344.5		318.8		290.0		324.6		102.5		314.0		283.5		287.1		1,277.9		987.1		1,004.2
Income (Loss) from discontinued operations, net of tax, attributable to Air Products	0.0		0.0		0.0		0.0		1.5		0.0		0.0		3.1		0.0		4.6		(10.0)
Net Income Attributable to Air Products	$ 344.5		$ 318.8		$ 290.0		$ 324.6		$ 104.0		$ 314.0		$ 283.5		$ 290.2		$ 1,277.9		$ 991.7		$ 994.2
Basic Earnings Per Common Share Attributable to Air Products
Income from continuing operations	$ 1.6		$ 1.48		$ 1.35		$ 1.52		$ 0.48		$ 1.47		$ 1.33		$ 1.36		$ 5.95		$ 4.64		$ 4.79
Income (loss) from discontinued operations	0		0		0		0		0.01		0		0		0.01		0		0.02		(0.05)
Net Income Attributable to Air Products	1.6		1.48		1.35		1.52		0.49		1.47		1.33		1.37		5.95		4.66		4.74
Diluted Earnings Per Common Share Attributable to Air Products
Income from continuing operations	1.58		1.47		1.33		1.5		0.47		1.46		1.32		1.34		5.88		4.59		4.73
Income (loss) from discontinued operations	0		0		0		0		0.01		0		0		0.01		0		0.02		(0.05)
Net Income Attributable to Air Products	1.58		1.47		1.33		1.5		0.48		1.46		1.32		1.35		5.88		4.61		4.68
Dividends per common share	0.81		0.81		0.81		0.77		0.77		0.77		0.77		0.71		$ 3.2		$ 3.02		$ 2.77
Market Price Per Share High	148.56		153.93		158.2		149.61		137.45		131.48		124.4		113.99
Market Price Per Share Low	$ 123.66		$ 136.69		$ 137.07		$ 118.2		$ 126.82		$ 114.28		$ 102.73		$ 102.23
Segment Reconciling Items [Member]
Quarterly Financial Information Disclosure [Abstract]
Business restructuring and cost reduction actions																	$ 207.7		$ 12.7		$ 231.6
Pension settlement loss																	21.2		5.5		0.0
Goodwill and intangible asset impairment charge																	0.0		310.1		0.0
Business separation costs																	7.5		0.0		0.0
Gain on previously held equity interest																	17.9		0.0		0.0
Gain on land sales	$ 33.6	[7]	$ 0.0	[7]	$ 0.0	[7]	$ 0.0	[7]									$ 33.6	[7],[8]	$ 0.0	[8]	$ 0.0	[8]

[1] For additional information, see Note 5, Business Restructuring and Cost Reduction Actions.

[2] For additional information, see Note 16, Retirement Benefits.

[3] For additional information, see Note 10, Goodwill, and Note 11, Intangible Assets.

[4] For additional information, see Note 3, Materials Technologies Separation.

[5] For additional information, see Note 6, Business Combinations.

[6] For additional information, see Note 15, Debt.

[7] The gain is reflected on the consolidated income statements in “Other income (expense), net.” For additional information, see Note 24, Supplemental Information.

[8] Reflected on the consolidated income statements in "Other income (expense), net."