Business Segments (Segment Financial Information) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
External customer revenues	$ 184.2	$ 178.1	$ 393.2	$ 383.8
Intersegment revenues	0.0	0.0	0.0	0.0
Total revenues	184.2	178.1	393.2	383.8
Depreciation and amortization	18.0	20.3	36.4	39.1
Fuel Costs	4.3	3.6	7.8	8.1
Depreciation and amortization			13.9	41.6
Interest expense	21.7	24.0	45.4	51.8
Gain (Loss) on Extinguishment of Debt	(44.9)	(5.7)	(44.9)	(6.4)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(22.7)	(6.9)	(3.5)	(6.1)
Net income / (loss) from continuing operations	(16.8)	(5.4)	(0.3)	(4.5)
Discontinued operations, net of tax	0.7	8.9	26.3	24.9
Net income/ (loss)	(16.1)	3.5	26.0	20.4
Capital expenditures	29.1	23.4	63.4	50.7
Total assets	1,817.7		1,817.7		$ 1,883.1
Operating Segments [Member] | Utility [Member]
Segment Reporting Information [Line Items]
External customer revenues	177.4	168.6	378.5	364.4
Intersegment revenues	0.3	0.2	0.6	0.4
Total revenues	177.7	168.8	379.1	364.8
Depreciation and amortization	17.5	18.8	35.5	37.4
Interest expense	6.7	6.5	13.8	14.7
Gain (Loss) on Extinguishment of Debt	0.0		0.0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	36.0	17.1	71.1	36.4
Capital expenditures	28.5	19.9	62.2	44.5
Total assets	1,775.1		1,775.1		1,819.6
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
External customer revenues	6.8	9.5	14.7	19.4
Intersegment revenues	0.8	0.8	1.6	1.4
Total revenues	7.6	10.3	16.3	20.8
Depreciation and amortization	0.5	1.5	0.9	1.7
Interest expense	15.0	17.5	31.6	37.1
Gain (Loss) on Extinguishment of Debt	(44.9)		(44.9)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(58.7)	(24.0)	(74.6)	(42.5)
Capital expenditures	0.6	3.5	1.2	6.2
Total assets	42.6		42.6		63.5
Adjustments and Eliminations [Member]
Segment Reporting Information [Line Items]
External customer revenues	0.0	0.0	0.0	0.0
Intersegment revenues	(1.1)	(1.0)	(2.2)	(1.8)
Total revenues	(1.1)	(1.0)	(2.2)	(1.8)
Depreciation and amortization	0.0	0.0	0.0	0.0
Interest expense	0.0	0.0	0.0	0.0
Gain (Loss) on Extinguishment of Debt	0.0		0.0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	0.0	0.0	0.0	0.0
Capital expenditures	0.0	0.0	0.0	0.0
Subsidiaries [Member]
Segment Reporting Information [Line Items]
Gain (Loss) on Disposition of Business	0.0	0.0	0.0	(12.4)
Depreciation and amortization	17.5	18.8	35.5	37.4
Fuel Costs	0.5	0.7	1.4	1.6
Depreciation and amortization			35.5	37.4
Interest expense	6.7	6.5	13.8	14.7
Gain (Loss) on Extinguishment of Debt	0.0	(0.1)	0.0	(0.6)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	36.0	17.1	71.1	36.4
Net income/ (loss)	29.8	$ 15.0	58.8	$ 30.7
Total assets	$ 1,775.1		$ 1,775.1		$ 1,819.6