Business Restructuring and Cost Reduction Plans (Carrying Amount of Accrual) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended		3 Months Ended						12 Months Ended	3 Months Ended			12 Months Ended		3 Months Ended						12 Months Ended	3 Months Ended					12 Months Ended		3 Months Ended
	Dec. 31, 2012	Sep. 30, 2012		Mar. 31, 2012 Cost Reduction Plan [Member]	Sep. 30, 2012 Photovoltaic Market Actions [Member]		Sep. 30, 2012 Polyurethane Intermediates Business Actions [Member]		Dec. 31, 2012 Severance And Other Benefits [Member]	Sep. 30, 2012 Severance And Other Benefits [Member]	Mar. 31, 2012 Severance And Other Benefits [Member] Cost Reduction Plan [Member]	Sep. 30, 2012 Severance And Other Benefits [Member] Polyurethane Intermediates Business Actions [Member]		Sep. 30, 2012 Asset Actions [Member]	Dec. 31, 2012 Asset Actions [Member]	Mar. 31, 2012 Asset Actions [Member] Cost Reduction Plan [Member]	Sep. 30, 2012 Asset Actions [Member] Photovoltaic Market Actions [Member]		Sep. 30, 2012 Asset Actions [Member] Polyurethane Intermediates Business Actions [Member]		Dec. 31, 2012 Contract Actions [Member]	Sep. 30, 2012 Contract Actions [Member]	Sep. 30, 2012 Contract Actions [Member] Photovoltaic Market Actions [Member]		Sep. 30, 2012 Contract Actions [Member] Polyurethane Intermediates Business Actions [Member]		Dec. 31, 2012 Other Costs [Member]	Sep. 30, 2012 Other Costs [Member]		Sep. 30, 2012 Other Costs [Member] Photovoltaic Market Actions [Member]		Sep. 30, 2012 Other Costs [Member] Polyurethane Intermediates Business Actions [Member]
Restructuring Cost and Reserve [Line Items]
2012 Charge		$ 327.4		$ 86.8	$ 186.0	[1]	$ 54.6	[2]		$ 83.5	$ 80.8	$ 2.7	[2]	$ 67.3		$ 6.0	$ 34.7	[1]	$ 26.6	[2]		$ 100.0	$ 93.5	[1]	$ 6.5	[2]		$ 76.6		$ 57.8	[1]	$ 18.8	[2]
Amount reflected in environmental liability		(9.0)	[3]																									(9.0)	[3]
Amount reflected in pension liability		(7.5)								(7.5)
Noncash expenses		(87.0)								(0.4)				(67.3)														(19.3)
Cash expenditures	(11.9)	(32.9)							(8.9)	(32.8)											(2.6)						(0.4)	(0.1)
Currency translation adjustment	0.6	(1.6)							0.6	(1.6)
Accrued Balance	$ 178.1	$ 189.4							$ 32.9	$ 41.2				$ 0	$ 0						$ 97.4	$ 100.0					$ 47.8	$ 48.2

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

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

[3] Reflected in accrual for environmental obligations. See Note 11, Commitments and Contingencies.