Business Segments (Segment Financial Information) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Segment Reporting Information [Line Items]
Revenues	$ 209.2	$ 202.0	$ 435.6	$ 442.1
Depreciation and amortization	21.1	20.5	43.7	40.3
Interest expense	20.8	19.3	41.1	37.4
Total assets	3,133.7		3,133.7		$ 2,906.2
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	11.5	(10.6)	15.7	(8.3)
Revenue from external customers
Segment Reporting Information [Line Items]
Revenues	209.2	202.0	435.6	442.1
Intersegment revenue
Segment Reporting Information [Line Items]
Revenues	0.0	0.0	0.0	0.0
Utility [Member]
Segment Reporting Information [Line Items]
Revenues	206.9	199.7	431.2	437.5
Operating Segments [Member] | Utility [Member]
Segment Reporting Information [Line Items]
Revenues	206.9	199.7	431.2	437.5
Depreciation and amortization	20.7	20.2	42.8	39.6
Interest expense	11.7	9.7	22.9	18.0
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	18.9	(1.9)	30.6	9.0
Operating Segments [Member] | Utility [Member] | Revenue from external customers
Segment Reporting Information [Line Items]
Revenues	206.7	199.5	430.8	437.2
Operating Segments [Member] | Utility [Member] | Intersegment revenue
Segment Reporting Information [Line Items]
Revenues	0.2	0.2	0.4	0.3
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenues	3.8	3.3	7.3	6.6
Depreciation and amortization	0.4	0.3	0.9	0.7
Interest expense	9.1	9.6	18.2	19.4
Total assets	49.4		49.4		35.2
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(7.4)	(8.7)	(14.9)	(17.3)
Corporate, Non-Segment [Member] | Revenue from external customers
Segment Reporting Information [Line Items]
Revenues	2.5	2.5	4.8	4.9
Corporate, Non-Segment [Member] | Intersegment revenue
Segment Reporting Information [Line Items]
Revenues	1.3	0.8	2.5	1.7
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues	(1.5)	(1.0)	(2.9)	(2.0)
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)	(1.0)	(2.9)	(2.0)
Subsidiaries [Member]
Segment Reporting Information [Line Items]
Revenues	206.9	199.7	431.2	437.5
Depreciation and amortization	20.7	20.2	42.8	39.6
Interest expense	11.7	9.7	22.9	18.0
Total assets	3,084.3		3,084.3		$ 2,871.0
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	$ 18.9	$ (1.9)	$ 30.6	$ 9.0