Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 21.0	$ 30.5
Accounts Receivable, after Allowance for Credit Loss, Current	96.7	91.9
Inventories	29.4	26.8
Taxes applicable to subsequent years	70.0	94.0
Regulatory assets, current	32.2	39.2
Income Taxes Receivable, Current	13.2	10.9
Prepayments and other current assets	7.7	3.9
Total current assets	270.2	297.2
Property, plant & equipment:
Property, plant & equipment	2,292.5	2,193.6
Less: Accumulated depreciation and amortization	(512.6)	(505.7)
Property, plant and equipment, net of depreciation	1,779.9	1,687.9
Construction work in process	163.1	197.1
Total net property, plant & equipment	1,943.0	1,885.0
Other non-current assets:
Regulatory assets, non-current	133.9	129.8
Intangible assets, net of amortization	77.1	70.1
Other non-current assets	42.9	40.3
Total other non-current assets	253.9	240.2
Total assets	2,467.1	2,422.4
Current liabilities:
Current portion of long-term debt	260.2	155.2
Accounts payable	110.5	129.5
Accrued taxes	94.3	88.4
Accrued interest	20.7	16.1
Contract with Customer, Liability, Current	23.7	16.7
Regulatory liabilities, current	29.5	40.4
Other current liabilities	23.2	20.9
Total current liabilities	562.1	467.2
Non-current liabilities:
Long-term debt	1,536.5	1,535.7
Deferred Tax Liabilities, Net	204.1	199.0
Taxes payable	47.1	94.5
Regulatory liabilities, non-current	196.4	198.7
Pension, retiree and other benefits	34.7	41.8
Other deferred credits	8.9	9.2
Total non-current liabilities	2,027.7	2,078.9
Commitments and contingencies
Common shareholder's equity:
Common stock	0.0	0.0
Other paid-in capital	2,601.3	2,601.3
Accumulated other comprehensive income	(2.6)	(2.4)
Retained Earnings (Accumulated Deficit)	(2,721.4)	(2,722.6)
Total common shareholder's equity	(122.7)	(123.7)
Total liabilities and shareholder's equity	$ 2,467.1	$ 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	$ 9.4	$ 19.7
Accounts Receivable, after Allowance for Credit Loss, Current	96.6	92.3
Inventories	29.4	26.8
Taxes applicable to subsequent years	69.9	93.9
Regulatory assets, current	32.2	39.2
Income Taxes Receivable, Current	29.4	29.6
Prepayments and other current assets	7.9	4.2
Total current assets	274.8	305.7
Property, plant & equipment:
Property, plant & equipment	2,845.9	2,752.7
Less: Accumulated depreciation and amortization	(1,088.3)	(1,086.5)
Property, plant and equipment, net of depreciation	1,757.6	1,666.2
Construction work in process	161.6	195.3
Total net property, plant & equipment	1,919.2	1,861.5
Other non-current assets:
Regulatory assets, non-current	133.9	129.8
Intangible assets, net of amortization	75.4	68.5
Other non-current assets	43.2	40.4
Total other non-current assets	252.5	238.7
Total assets	2,446.5	2,405.9
Current liabilities:
Current portion of long-term debt	230.2	120.2
Accounts payable	110.1	129.5
Accrued taxes	94.2	88.3
Accrued interest	8.3	3.4
Contract with Customer, Liability, Current	23.2	16.3
Regulatory liabilities, current	29.5	40.4
Other current liabilities	20.8	18.7
Total current liabilities	516.3	416.8
Non-current liabilities:
Long-term debt	712.8	712.5
Deferred Tax Liabilities, Net	197.7	194.9
Taxes payable	47.1	94.3
Regulatory liabilities, non-current	196.4	198.7
Pension, retiree and other benefits	34.7	41.8
Other deferred credits	4.9	5.1
Total non-current liabilities	1,193.6	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	760.5	773.6
Accumulated other comprehensive income	(26.7)	(26.8)
Retained Earnings (Accumulated Deficit)	2.4	(5.4)
Total common shareholder's equity	736.6	741.8
Total liabilities and shareholder's equity	$ 2,446.5	$ 2,405.9
Common Stock, Shares, Outstanding	41,172,173	41,172,173
Common Stock, Shares Authorized	50,000,000	50,000,000