Fair Value Measurements (Schedule of Nonrecurring Fair Value Measurements) (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017		Sep. 30, 2016
Long Lived Assets Held-for-sale [Line Items]
Equity method investment impairment charge			$ 0.0	$ 79.5		$ 0.0
Abdullah Hashim Industrial Gases & Equipment Co., Ltd.
Long Lived Assets Held-for-sale [Line Items]
Equity method investment impairment charge		$ 79.5		$ 79.5	[1]
Abdullah Hashim Industrial Gases & Equipment Co., Ltd. | Fair Value, Measurements, Nonrecurring
Long Lived Assets Held-for-sale [Line Items]
Investment in Equity Affiliate	[1]	68.5
Abdullah Hashim Industrial Gases & Equipment Co., Ltd. | Level 1 | Fair Value, Measurements, Nonrecurring
Long Lived Assets Held-for-sale [Line Items]
Investment in Equity Affiliate	[1]	0.0
Abdullah Hashim Industrial Gases & Equipment Co., Ltd. | Level 2 | Fair Value, Measurements, Nonrecurring
Long Lived Assets Held-for-sale [Line Items]
Investment in Equity Affiliate	[1]	0.0
Abdullah Hashim Industrial Gases & Equipment Co., Ltd. | Level 3 | Fair Value, Measurements, Nonrecurring
Long Lived Assets Held-for-sale [Line Items]
Investment in Equity Affiliate	[1]	$ 68.5

[1] In fiscal year 2017, we assessed the recoverability of the carrying value of our equity investment in AHG. We estimated the fair value of our investment using weighting of the results of the income and market approaches. An impairment loss was recognized for the difference between the carrying amount and the fair value of the investment as of 30 June 2017. There have been no events during fiscal year 2018 requiring reassessment of our investment. For additional information, see Note 8, Summarized Financial Information of Equity Affiliates.