Discontinued Operations (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Revenue	$ 0.5	$ 8.8	$ 1.4	$ 22.4
Disposal Group, Including Discontinued Operation, Operating and Other Expenses	(0.7)	(10.0)	(2.4)	(24.4)
Cash Provided by (Used in) Operating Activities, Discontinued Operations	0.2	(2.7)	(0.0)	3.6
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	1.5	3.7	15.4	6.1
Payments for Removal Costs			0.8	0.6
Cash Provided by (Used in) Investing Activities, Discontinued Operations	(0.4)	(0.6)	(0.8)	4.4
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax	0.0	4.5	0.0	4.5
Loss from discontinued operations before income taxes	(0.2)	(1.2)	(1.0)	(2.0)
Income tax expense / (benefit) from discontinued operations	0.0	0.7	(0.2)	0.5
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	(0.2)	2.6	(0.8)	2.0
Cash Provided by (Used in) Operating Activities, Discontinued Operations	0.2	(2.7)	(0.0)	3.6
Cash flows from investing activities for discontinued operations	(0.4)	(0.6)	(0.8)	4.4
Subsidiaries [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	$ 9.1	$ 15.5	30.6	$ 28.4
Conesville [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payments for Removal Costs			2.6
Conesville [Member] | Forecast [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payments for Removal Costs			$ 4.0