Business Segments (Segment Financial Information) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Segment Reporting Information [Line Items]
External customer revenues	$ 190.9	$ 148.1	$ 390.2	$ 323.3
Intersegment revenues	0.0	0.0	0.0	0.0
Total revenues	190.9	148.1	390.2	323.3
Depreciation and amortization	20.1	18.9	39.6	38.0
Interest expense	16.5	15.6	32.0	31.2
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(0.6)	1.5	11.1	15.4
Total assets	2,275.4		2,275.4		$ 2,171.8
Operating Segments [Member] | Utility [Member]
Segment Reporting Information [Line Items]
External customer revenues	188.5	145.7	385.3	318.3
Intersegment revenues	0.2	0.2	0.4	0.4
Total revenues	188.7	145.9	385.7	318.7
Depreciation and amortization	19.7	18.5	38.9	37.2
Interest expense	6.8	6.0	12.7	12.0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	7.3	9.1	26.9	30.6
Total assets					2,162.6
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
External customer revenues	2.4	2.4	4.9	5.0
Intersegment revenues	0.9	0.9	1.8	1.8
Total revenues	3.3	3.3	6.7	6.8
Depreciation and amortization	0.4	0.4	0.7	0.8
Interest expense	9.7	9.6	19.3	19.2
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(7.9)	(7.6)	(15.8)	(15.2)
Total assets	16.1		16.1		9.2
Adjustments and Eliminations [Member]
Segment Reporting Information [Line Items]
External customer revenues	0.0	0.0	0.0	0.0
Intersegment revenues	(1.1)	(1.1)	(2.2)	(2.2)
Total revenues	(1.1)	(1.1)	(2.2)	(2.2)
Depreciation and amortization	0.0	0.0	0.0	0.0
Interest expense	0.0	0.0	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
Subsidiaries [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	19.7	18.5	38.9	37.2
Interest expense	6.8	6.0	12.7	12.0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	7.3	$ 9.1	26.9	$ 30.6
Total assets	$ 2,259.3		$ 2,259.3		$ 2,162.6