Discontinued Operations (Schedule of Operating Results) (Details) - USD ($) $ in Millions			3 Months Ended			6 Months Ended
		Jan. 03, 2017	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2018	Mar. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (Loss) from Discontinued Operations, net of tax			$ 0.0	$ 1,825.6		$ (1.0)	$ 1,873.8
Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales							254.8
Cost of sales				6.3			191.9
Selling and administrative				2.1			22.7
Research and development							5.1
Other income (expense), net				0.3			0.2
Operating Income (Loss)							35.3
Equity affiliates’ income							0.3
Income (Loss) Before Taxes				(8.1)			35.6
Income tax benefit				(1.2)			(52.8)	[1]
Income (Loss) From Operations of Discontinued Operations, net of tax				(6.9)			88.4
Gain (Loss) on Disposal, net of tax				1,832.5			1,785.4
Income (Loss) from Discontinued Operations, net of tax			$ 0.0	1,825.6		$ (1.0)	1,873.8
Performance Materials Division (PMD) | Discontinued Operations, Held-for-sale or Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales							254.8
Cost of sales				3.3			182.3
Selling and administrative				2.1			22.5
Research and development							5.1
Other income (expense), net				0.7			0.3
Operating Income (Loss)							45.2
Equity affiliates’ income							0.3
Income (Loss) Before Taxes				(4.7)			45.5
Income tax benefit				(0.3)			(50.8)	[1]
Income (Loss) From Operations of Discontinued Operations, net of tax				(4.4)			96.3
Gain (Loss) on Disposal, net of tax		$ 1,833.0		1,832.5			1,832.5
Income (Loss) from Discontinued Operations, net of tax				1,828.1			1,928.8
Valuation allowance adjustment effect on income tax provision					$ 66.0
Energy-from-Waste (EfW) | Discontinued Operations, Held-for-sale or Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales	[2]						0.0
Cost of sales	[2]			3.0			9.6
Selling and administrative	[2]			0.0			0.2
Research and development	[2]						0.0
Other income (expense), net	[2]			(0.4)			(0.1)
Operating Income (Loss)	[2]						(9.9)
Equity affiliates’ income	[2]						0.0
Income (Loss) Before Taxes	[2]			(3.4)			(9.9)
Income tax benefit	[2]			(0.9)			(2.0)
Income (Loss) From Operations of Discontinued Operations, net of tax	[2]			(2.5)			(7.9)
Gain (Loss) on Disposal, net of tax	[2]			0.0			(47.1)
Income (Loss) from Discontinued Operations, net of tax	[2]			$ (2.5)			$ (55.0)

[1] As a result of the expected gain on the sale of PMD, we released valuation allowances related to capital loss and net operating loss carryforwards during the first quarter of 2017 that favorably impacted our income tax provision within discontinued operations by approximately $66.

[2] The loss from operations of discontinued operations for EfW primarily relates to land lease obligations, administrative costs, and costs incurred for project exit activities.