Business Restructuring and Cost Reduction Plans (Segment Impacts) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2011		Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2012 Cost Reduction Plan [Member]	Sep. 30, 2009 Cost Reduction Plan [Member]	Sep. 30, 2012 Photovoltaic Market Actions [Member]		Sep. 30, 2012 Polyurethane Intermediates Business Actions [Member]		Sep. 30, 2012 Merchant Gases [Member] Cost Reduction Plan [Member]	Sep. 30, 2012 Tonnage Gases [Member] Cost Reduction Plan [Member]	Sep. 30, 2012 Electronics and Performance Materials [Member] Cost Reduction Plan [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Other Benefits															$ 80.8
Asset Impairments															6.0
Total	$ 240.6	[1]	$ 0	[1]	$ 86.8	[1]	$ 0	[1]	$ 327.4	[2]	$ 0	[2]	$ 0	[2]	$ 86.8	$ 298.2	$ 186.0	[3]	$ 54.6	[4]	$ 77.3	$ 3.8	$ 5.7

[1]   For additional information, see Note 4, Business Restructuring and Cost Reduction Plans.

[2] Information about how this charge related to the businesses at the segment level is discussed in Note 4, Business Restructuring and Cost Reduction Plans.

[3]   Other includes the write-down of inventory to its net realizable value, the write-down of accounts receivable, and expected losses on purchase commitments.

[4]   Charge is net of $32.7 in proceeds received in cash at closing for certain PUI assets and the rights to a supply contract.