Discontinued Operations (Schedule of Operating Results) (Details) - USD ($) $ in Millions			3 Months Ended			9 Months Ended
		Jan. 03, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2018	Jun. 30, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (Loss) from Discontinued Operations, net of tax			$ 43.2	$ (2.3)		$ 42.2	$ 1,871.5
Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales							254.8
Cost of sales							194.2
Selling and administrative							23.0
Research and development							5.1
Other income (expense), net							(0.6)
Operating Income (Loss)							31.9
Equity affiliates’ income							0.3
Income (Loss) Before Taxes							32.2
Income tax benefit	[1]						(53.9)
Income (Loss) From Operations of Discontinued Operations, net of tax							86.1
Gain (Loss) on Disposal, net of tax							1,785.4
Income (Loss) from Discontinued Operations, net of tax			$ 43.2	$ (2.3)		42.2	1,871.5
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							182.3
Selling and administrative							22.5
Research and development							5.1
Other income (expense), net							0.3
Operating Income (Loss)							45.2
Equity affiliates’ income							0.3
Income (Loss) Before Taxes							45.5
Income tax benefit	[1]						(50.8)
Income (Loss) From Operations of Discontinued Operations, net of tax							96.3
Gain (Loss) on Disposal, net of tax		$ 1,833.0					1,832.5
Income (Loss) from Discontinued Operations, net of tax							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							0.0
Cost of sales							11.9
Selling and administrative							0.5
Research and development							0.0
Other income (expense), net							(0.9)
Operating Income (Loss)							(13.3)
Equity affiliates’ income							0.0
Income (Loss) Before Taxes							(13.3)
Income tax benefit							(3.1)
Income (Loss) From Operations of Discontinued Operations, net of tax							(10.2)
Gain (Loss) on Disposal, net of tax							(47.1)
Income (Loss) from Discontinued Operations, net of tax						$ (1.0)	$ (57.3)

[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.