Business Segments (Segment Financial Information) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Segment Reporting Information [Line Items]
External customer revenues	$ 240.1	$ 199.3
Intersegment revenues	0.0	0.0
Total revenues	240.1	199.3
Depreciation and amortization	19.8	19.5
Interest expense	18.1	15.5
Total assets	2,467.1		$ 2,422.4
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	2.3	11.7
Operating Segments [Member] | Utility [Member]
Segment Reporting Information [Line Items]
External customer revenues	237.7	196.8
Intersegment revenues	0.1	0.2
Total revenues	237.8	197.0
Depreciation and amortization	19.4	19.2
Interest expense	8.3	5.9
Total assets			2,405.9
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	10.9	19.6
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
External customer revenues	2.4	2.5
Intersegment revenues	0.9	0.9
Total revenues	3.3	3.4
Depreciation and amortization	0.4	0.3
Interest expense	9.8	9.6
Total assets	20.6		16.5
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(8.6)	(7.9)
Intersegment Eliminations
Segment Reporting Information [Line Items]
External customer revenues	0.0	0.0
Intersegment revenues	(1.0)	(1.1)
Total revenues	(1.0)	(1.1)
Depreciation and amortization	0.0	0.0
Interest expense	0.0	0.0
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	0.0	0.0
Subsidiaries [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	19.4	19.2
Interest expense	8.3	5.9
Total assets	2,446.5		$ 2,405.9
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	$ 10.9	$ 19.6