Business Segments (Segment Financial Information) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Segment Reporting Information [Line Items]
Revenues	$ 224.2	$ 262.1	$ 666.3	$ 652.3
Depreciation and amortization	20.6	20.0	60.9	59.6
Interest expense	7.8	18.1	45.2	50.1
Total assets	2,655.7		2,655.7		$ 2,422.4
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	48.2	(23.8)	39.9	(12.7)
Utility [Member]
Segment Reporting Information [Line Items]
Revenues	222.0	259.9	659.5	645.6
Operating Segments [Member] | Utility [Member]
Segment Reporting Information [Line Items]
Revenues	222.0	259.9	659.5	645.6
Depreciation and amortization	20.3	19.8	59.9	58.7
Interest expense	(1.3)	8.4	16.7	21.1
Total assets					2,405.9
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	55.1	(15.6)	64.1	11.3
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenues	3.9	3.2	10.5	9.9
Depreciation and amortization	0.3	0.2	1.0	0.9
Interest expense	9.1	9.7	28.5	29.0
Total assets	17.7		17.7		16.5
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(6.9)	(8.2)	(24.2)	(24.0)
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues	(1.7)	(1.0)	(3.7)	(3.2)
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 Income Taxes, Noncontrolling Interest	0.0	0.0	0.0	0.0
Subsidiaries [Member]
Segment Reporting Information [Line Items]
Revenues	222.0	259.9	659.5	645.6
Depreciation and amortization	20.3	19.8	59.9	58.7
Interest expense	(1.3)	8.4	16.7	21.1
Total assets	2,638.0		2,638.0		$ 2,405.9
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	$ 55.1	$ (15.6)	$ 64.1	$ 11.3