Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
CURRENT ASSETS:
Cash and cash equivalents	$ 49.3	$ 30.5
Accounts Receivable, after Allowance for Credit Loss, Current	85.1	91.9
Inventories	38.0	26.8
Taxes applicable to subsequent years	24.1	94.0
Regulatory assets, current	49.0	39.2
Income Taxes Receivable, Current	4.9	10.9
Prepayments and other current assets	9.4	3.9
Total current assets	259.8	297.2
Property, plant & equipment:
Property, plant & equipment	2,428.6	2,193.6
Less: Accumulated depreciation and amortization	(520.0)	(505.7)
Property, plant and equipment, net of depreciation	1,908.6	1,687.9
Construction work in process	175.8	197.1
Net property, plant & equipment	2,084.4	1,885.0
Other non-current assets:
Regulatory assets, non-current	160.2	129.8
Intangible assets, net of amortization	100.3	70.1
Other non-current assets	51.0	40.3
Total other non-current assets	311.5	240.2
Total assets	2,655.7	2,422.4
Current liabilities:
Current portion of long-term debt	120.2	155.2
Accounts payable	91.8	129.5
Accrued taxes	104.6	88.4
Accrued interest	22.9	16.1
Contract with Customer, Liability, Current	26.0	16.7
Regulatory liabilities, current	22.2	40.4
Other current liabilities	27.1	20.9
Total current liabilities	414.8	467.2
Non-current liabilities:
Long-term debt	1,637.3	1,535.7
Deferred Tax Liabilities, Net	223.8	199.0
Taxes payable	0.4	94.5
Regulatory liabilities, non-current	186.8	198.7
Pension, retiree and other benefits	34.7	41.8
Other deferred credits	8.4	9.2
Total non-current liabilities	2,091.4	2,078.9
Commitments and contingencies
Common shareholder's equity:
Common stock	0.0	0.0
Other paid-in capital	2,840.4	2,601.3
Accumulated other comprehensive income	(2.9)	(2.4)
Retained Earnings (Accumulated Deficit)	(2,688.0)	(2,722.6)
Total common shareholder's equity	149.5	(123.7)
Total liabilities and shareholder's equity	$ 2,655.7	$ 2,422.4
Common Stock, Shares Authorized	1,500	1,500
Common stock, shares issued	1	1
Subsidiaries [Member]
CURRENT ASSETS:
Cash and cash equivalents	$ 33.0	$ 19.7
Accounts Receivable, after Allowance for Credit Loss, Current	84.5	92.3
Inventories	38.0	26.8
Taxes applicable to subsequent years	24.1	93.9
Regulatory assets, current	49.0	39.2
Income Taxes Receivable, Current	28.9	29.6
Prepayments and other current assets	11.3	4.2
Total current assets	268.8	305.7
Property, plant & equipment:
Property, plant & equipment	2,972.9	2,752.7
Less: Accumulated depreciation and amortization	(1,086.1)	(1,086.5)
Property, plant and equipment, net of depreciation	1,886.8	1,666.2
Construction work in process	172.6	195.3
Net property, plant & equipment	2,059.4	1,861.5
Other non-current assets:
Regulatory assets, non-current	160.2	129.8
Intangible assets, net of amortization	98.4	68.5
Other non-current assets	51.2	40.4
Total other non-current assets	309.8	238.7
Total assets	2,638.0	2,405.9
Current liabilities:
Current portion of long-term debt	120.2	120.2
Accounts payable	91.1	129.5
Accrued taxes	104.4	88.3
Accrued interest	10.5	3.4
Contract with Customer, Liability, Current	25.9	16.3
Regulatory liabilities, current	22.2	40.4
Other current liabilities	24.4	18.7
Total current liabilities	398.7	416.8
Non-current liabilities:
Long-term debt	812.7	712.5
Deferred Tax Liabilities, Net	210.3	194.9
Taxes payable	0.4	94.3
Regulatory liabilities, non-current	186.8	198.7
Pension, retiree and other benefits	34.7	41.8
Other deferred credits	4.4	5.1
Total non-current liabilities	1,249.3	1,247.3
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	977.4	773.6
Accumulated other comprehensive income	(26.5)	(26.8)
Retained Earnings (Accumulated Deficit)	38.7	(5.4)
Total common shareholder's equity	990.0	741.8
Total liabilities and shareholder's equity	$ 2,638.0	$ 2,405.9
Common Stock, Shares, Outstanding	41,172,173	41,172,173
Common Stock, Shares Authorized	50,000,000	50,000,000