Condensed Consolidated Statements of Operations - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Revenues	$ 224.2	$ 262.1	$ 666.3	$ 652.3
OPERATING COSTS AND EXPENSES:
Utilities Operating Expense, Purchased Power	67.2	180.2	276.9	361.6
Operating expenses:
Operation and maintenance	56.6	48.8	170.7	132.7
Depreciation and amortization	20.6	20.0	60.9	59.6
Taxes other than income taxes	25.2	20.4	77.4	63.6
Gain (Loss) on Sale of Assets and Asset Impairment Charges, excluding Discontinued Operations	0.0	0.0	0.0	(0.6)
Costs and Expenses	169.6	269.4	585.9	616.9
OPERATING INCOME / (LOSS)	54.6	(7.3)	80.4	35.4
OTHER INCOME / (EXPENSE), NET:
Interest expense, net	(7.8)	(18.1)	(45.2)	(50.1)
Other Nonoperating Income (Expense)	1.4	1.6	4.7	2.0
Total other expense, net	(6.4)	(16.5)	(40.5)	(48.1)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	48.2	(23.8)	39.9	(12.7)
Income tax expense / (benefit)	9.6	(4.1)	5.3	(8.6)
NET INCOME / (LOSS)	38.6	(19.7)	34.6	(4.1)
Subsidiaries [Member]
Revenues	222.0	259.9	659.5	645.6
OPERATING COSTS AND EXPENSES:
Utilities Operating Expense, Purchased Power	67.2	179.8	276.4	360.6
Operating expenses:
Operation and maintenance	56.7	48.2	169.1	131.3
Depreciation and amortization	20.3	19.8	59.9	58.7
Taxes other than income taxes	25.2	20.4	77.3	63.4
Gain (Loss) on Sale of Assets and Asset Impairment Charges, excluding Discontinued Operations	0.0	0.0	0.0	(0.6)
Costs and Expenses	169.4	268.2	582.7	613.4
OPERATING INCOME / (LOSS)	52.6	(8.3)	76.8	32.2
OTHER INCOME / (EXPENSE), NET:
Interest expense, net	1.3	(8.4)	(16.7)	(21.1)
Other Nonoperating Income (Expense)	1.2	1.1	4.0	0.2
Total other expense, net	2.5	(7.3)	(12.7)	(20.9)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	55.1	(15.6)	64.1	11.3
Income tax expense / (benefit)	11.5	(5.5)	11.3	(2.8)
NET INCOME / (LOSS)	$ 43.6	$ (10.1)	$ 52.8	$ 14.1