Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
CURRENT ASSETS:
Cash and cash equivalents	$ 41.0	$ 41.0
Accounts Receivable, after Allowance for Credit Loss, Current	101.4	92.5
Inventories	72.3	44.5
Taxes applicable to subsequent years	26.3	113.0
Regulatory assets, current	71.4	56.6
Income Taxes Receivable, Current	25.5	8.9
Prepayments and other current assets	14.3	6.6
Total current assets	352.2	363.1
Property, plant & equipment:
Property, plant & equipment	2,799.8	2,521.9
Less: Accumulated depreciation and amortization	(577.2)	(535.1)
Property, plant and equipment, net of depreciation	2,222.6	1,986.8
Construction work in process	269.5	234.2
Total net property, plant & equipment	2,492.1	2,221.0
Other non-current assets:
Regulatory assets, non-current	146.2	155.7
Intangible assets, net of amortization	162.4	114.0
Other non-current assets	47.6	52.4
Total other non-current assets	356.2	322.1
Total assets	3,200.5	2,906.2
Current liabilities:
Current portion of long-term debt	609.0	15.2
Accounts payable	123.5	163.9
Accrued taxes	114.6	101.6
Accrued interest	25.1	16.9
Contract with Customer, Liability, Current	22.1	12.7
Regulatory liabilities, current	15.8	18.0
Other current liabilities	35.2	22.6
Total current liabilities	945.3	350.9
Non-current liabilities:
Long-term debt	1,425.3	1,837.4
Deferred Tax Liabilities, Net	245.3	227.3
Taxes payable	0.4	113.4
Regulatory liabilities, non-current	172.2	182.1
Pension, retiree and other benefits	31.6	37.7
Other deferred credits	8.8	8.5
Total non-current liabilities	1,883.6	2,406.4
Commitments and contingencies
Common shareholder's equity:
Common stock	0.0	0.0
Other paid-in capital	3,040.5	2,840.4
Accumulated other comprehensive income	(5.1)	(4.6)
Retained Earnings (Accumulated Deficit)	(2,663.8)	(2,686.9)
Total common shareholder's equity	371.6	148.9
Total liabilities and shareholder's equity	$ 3,200.5	$ 2,906.2
Common Stock, Shares Authorized	1,500	1,500
Common stock, shares issued	1	1
Liabilities	$ 2,828.9	$ 2,757.3
Subsidiaries [Member]
CURRENT ASSETS:
Cash and cash equivalents	19.6	15.5
Accounts Receivable, after Allowance for Credit Loss, Current	101.1	93.1
Inventories	70.9	44.5
Taxes applicable to subsequent years	26.3	112.9
Regulatory assets, current	71.4	56.6
Income Taxes Receivable, Current	24.8	24.4
Prepayments and other current assets	16.1	8.1
Total current assets	330.2	355.1
Property, plant & equipment:
Property, plant & equipment	3,324.3	3,063.2
Less: Accumulated depreciation and amortization	(1,125.8)	(1,098.1)
Property, plant and equipment, net of depreciation	2,198.5	1,965.1
Construction work in process	268.4	230.8
Total net property, plant & equipment	2,466.9	2,195.9
Other non-current assets:
Regulatory assets, non-current	146.2	155.7
Intangible assets, net of amortization	160.4	111.4
Other non-current assets	46.5	52.9
Total other non-current assets	353.1	320.0
Total assets	3,150.2	2,871.0
Current liabilities:
Current portion of long-term debt	195.0	15.2
Accounts payable	122.4	163.8
Accrued taxes	114.5	101.4
Accrued interest	12.7	4.2
Contract with Customer, Liability, Current	22.1	12.7
Regulatory liabilities, current	15.8	18.0
Other current liabilities	32.2	20.2
Total current liabilities	514.7	335.5
Non-current liabilities:
Long-term debt	1,012.6	1,012.3
Deferred Tax Liabilities, Net	217.2	206.1
Taxes payable	0.4	113.4
Regulatory liabilities, non-current	172.2	182.1
Pension, retiree and other benefits	31.6	37.7
Other deferred credits	5.0	4.7
Total non-current liabilities	1,439.0	1,556.3
Commitments and contingencies
Par value common shares (in USD per share)	$ 0.01	$ 0.01
Common shareholder's equity:
Common stock	$ 0.4	$ 0.4
Other paid-in capital	1,177.5	977.4
Accumulated other comprehensive income	(26.7)	(27.9)
Retained Earnings (Accumulated Deficit)	45.3	29.3
Total common shareholder's equity	1,196.5	979.2
Total liabilities and shareholder's equity	$ 3,150.2	$ 2,871.0
Common Stock, Shares, Outstanding	41,172,173	41,172,173
Common Stock, Shares Authorized	50,000,000	50,000,000
Liabilities	$ 1,953.7	$ 1,891.8