Discontinued Operations (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015	Sep. 30, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on disposal, net of tax	$ 846.6	$ 0.0	$ 846.6	$ 0.0
Plant and equipment, estimated net realizable value	20.0		20.0		$ 0.0
Energy-from-Waste [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on disposal, before-tax	945.7
Loss on disposal, net of tax	846.6
Plant and equipment, estimated net realizable value	20.0		20.0
Deferred tax assets, valuation allowance	58.0		58.0
Unrecognized tax benefits	7.9		$ 7.9
Energy-from-Waste [Member] | Asset Actions [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on disposal, before-tax	913.5
Energy-from-Waste [Member] | Contract Actions/other [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on disposal, before-tax	$ 32.2