Business Segments (Segment Financial Information) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Segment Reporting Information [Line Items]
Revenues	$ 227.5	$ 224.2	$ 663.1	$ 666.3
Depreciation and amortization	25.7	20.6	69.4	60.9
Interest expense	21.1	7.8	62.2	45.2
Total assets	3,200.5		3,200.5		$ 2,906.2
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	2.8	48.2	18.5	39.9
Revenue from external customers
Segment Reporting Information [Line Items]
Revenues	227.5	224.2	663.1	666.3
Intersegment revenue
Segment Reporting Information [Line Items]
Revenues	0.0	0.0	0.0	0.0
Utility [Member]
Segment Reporting Information [Line Items]
Revenues	225.4	222.0	656.6	659.5
Operating Segments [Member] | Utility [Member]
Segment Reporting Information [Line Items]
Revenues	225.4	222.0	656.6	659.5
Depreciation and amortization	25.2	20.3	68.0	59.9
Interest expense	11.8	(1.3)	34.7	16.7
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	10.6	55.1	41.2	64.1
Operating Segments [Member] | Utility [Member] | Revenue from external customers
Segment Reporting Information [Line Items]
Revenues	225.1	221.8	655.9	659.0
Operating Segments [Member] | Utility [Member] | Intersegment revenue
Segment Reporting Information [Line Items]
Revenues	0.3	0.2	0.7	0.5
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenues	3.6	3.9	10.9	10.5
Depreciation and amortization	0.5	0.3	1.4	1.0
Interest expense	9.3	9.1	27.5	28.5
Total assets	50.3		50.3		35.2
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(7.8)	(6.9)	(22.7)	(24.2)
Corporate, Non-Segment [Member] | Revenue from external customers
Segment Reporting Information [Line Items]
Revenues	2.4	2.4	7.2	7.3
Corporate, Non-Segment [Member] | Intersegment revenue
Segment Reporting Information [Line Items]
Revenues	1.2	1.5	3.7	3.2
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues	(1.5)	(1.7)	(4.4)	(3.7)
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
Intersegment Eliminations | Revenue from external customers
Segment Reporting Information [Line Items]
Revenues	0.0	0.0	0.0	0.0
Intersegment Eliminations | Intersegment revenue
Segment Reporting Information [Line Items]
Revenues	(1.5)	(1.7)	(4.4)	(3.7)
Subsidiaries [Member]
Segment Reporting Information [Line Items]
Revenues	225.4	222.0	656.6	659.5
Depreciation and amortization	25.2	20.3	68.0	59.9
Interest expense	11.8	(1.3)	34.7	16.7
Total assets	3,150.2		3,150.2		$ 2,871.0
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	$ 10.6	$ 55.1	$ 41.2	$ 64.1