Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 45.1	$ 30.5
Accounts Receivable, after Allowance for Credit Loss, Current	80.6	91.9
Inventories	36.1	26.8
Taxes applicable to subsequent years	48.5	94.0
Regulatory assets, current	31.0	39.2
Income Taxes Receivable, Current	9.3	10.9
Prepayments and other current assets	13.4	3.9
Total current assets	264.0	297.2
Property, plant & equipment:
Property, plant & equipment	2,355.1	2,193.6
Less: Accumulated depreciation and amortization	(510.5)	(505.7)
Property, plant and equipment, net of depreciation	1,844.6	1,687.9
Construction work in process	152.4	197.1
Total net property, plant & equipment	1,997.0	1,885.0
Other non-current assets:
Regulatory assets, non-current	134.5	129.8
Intangible assets, net of amortization	86.7	70.1
Other non-current assets	44.7	40.3
Total other non-current assets	265.9	240.2
Total assets	2,526.9	2,422.4
Current liabilities:
Current portion of long-term debt	140.2	155.2
Accounts payable	109.8	129.5
Accrued taxes	95.0	88.4
Accrued interest	17.3	16.1
Contract with Customer, Liability, Current	13.3	16.7
Regulatory liabilities, current	19.6	40.4
Other current liabilities	22.8	20.9
Total current liabilities	418.0	467.2
Non-current liabilities:
Long-term debt	1,636.8	1,535.7
Deferred Tax Liabilities, Net	209.4	199.0
Taxes payable	48.9	94.5
Regulatory liabilities, non-current	186.1	198.7
Pension, retiree and other benefits	34.6	41.8
Other deferred credits	9.0	9.2
Total non-current liabilities	2,124.8	2,078.9
Commitments and contingencies
Common shareholder's equity:
Common stock	0.0	0.0
Other paid-in capital	2,713.4	2,601.3
Accumulated other comprehensive income	(2.7)	(2.4)
Retained Earnings (Accumulated Deficit)	(2,726.6)	(2,722.6)
Total common shareholder's equity	(15.9)	(123.7)
Total liabilities and shareholder's equity	$ 2,526.9	$ 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	$ 33.4	$ 19.7
Accounts Receivable, after Allowance for Credit Loss, Current	80.2	92.3
Inventories	36.1	26.8
Taxes applicable to subsequent years	48.4	93.9
Regulatory assets, current	31.0	39.2
Income Taxes Receivable, Current	29.1	29.6
Prepayments and other current assets	16.4	4.2
Total current assets	274.6	305.7
Property, plant & equipment:
Property, plant & equipment	2,903.8	2,752.7
Less: Accumulated depreciation and amortization	(1,080.8)	(1,086.5)
Property, plant and equipment, net of depreciation	1,823.0	1,666.2
Construction work in process	149.9	195.3
Total net property, plant & equipment	1,972.9	1,861.5
Other non-current assets:
Regulatory assets, non-current	134.5	129.8
Intangible assets, net of amortization	84.9	68.5
Other non-current assets	45.1	40.4
Total other non-current assets	264.5	238.7
Total assets	2,512.0	2,405.9
Current liabilities:
Current portion of long-term debt	140.2	120.2
Accounts payable	112.5	129.5
Accrued taxes	95.5	88.3
Accrued interest	4.7	3.4
Contract with Customer, Liability, Current	13.0	16.3
Regulatory liabilities, current	19.6	40.4
Other current liabilities	20.2	18.7
Total current liabilities	405.7	416.8
Non-current liabilities:
Long-term debt	812.6	712.5
Deferred Tax Liabilities, Net	197.7	194.9
Taxes payable	48.9	94.3
Regulatory liabilities, non-current	186.1	198.7
Pension, retiree and other benefits	34.6	41.8
Other deferred credits	5.0	5.1
Total non-current liabilities	1,284.9	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	847.8	773.6
Accumulated other comprehensive income	(26.6)	(26.8)
Retained Earnings (Accumulated Deficit)	(0.2)	(5.4)
Total common shareholder's equity	821.4	741.8
Total liabilities and shareholder's equity	$ 2,512.0	$ 2,405.9
Common Stock, Shares, Outstanding	41,172,173	41,172,173
Common Stock, Shares Authorized	50,000,000	50,000,000