Business Segments (Segment Financial Information) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Segment Reporting Information [Line Items]
External customer revenues	$ 199.3	$ 175.2
Intersegment revenues	0.0	0.0
Total revenues	199.3	175.2
Depreciation and amortization	19.5	19.1
Interest expense	15.5	15.6
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	11.7	13.9
Total assets	2,189.7		$ 2,171.8
Operating Segments [Member] | Utility [Member]
Segment Reporting Information [Line Items]
External customer revenues	196.8	172.6
Intersegment revenues	0.2	0.2
Total revenues	197.0	172.8
Depreciation and amortization	19.2	18.7
Interest expense	5.9	6.0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	19.6	21.5
Total assets			2,162.6
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
External customer revenues	2.5	2.6
Intersegment revenues	0.9	0.9
Total revenues	3.4	3.5
Depreciation and amortization	0.3	0.4
Interest expense	9.6	9.6
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(7.9)	(7.6)
Total assets	14.0		9.2
Adjustments and Eliminations [Member]
Segment Reporting Information [Line Items]
External customer revenues	0.0	0.0
Intersegment revenues	(1.1)	(1.1)
Total revenues	(1.1)	(1.1)
Depreciation and amortization	0.0	0.0
Interest expense	0.0	0.0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	0.0	0.0
Subsidiaries [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	19.2	18.7
Interest expense	5.9	6.0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	19.6	$ 21.5
Total assets	$ 2,175.7		$ 2,162.6