Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 60.3	$ 26.6
Accounts receivable, net	85.1	71.5
Accounts Receivable, Allowance for Credit Loss, Current	0.3	0.3
Inventories	17.9	14.4
Taxes applicable to subsequent years	40.5	83.1
Regulatory assets, current	37.2	24.5
Income Taxes Receivable, Current	6.1	2.7
Prepayments and other current assets	9.9	7.6
Total current assets	257.0	230.4
Property, plant & equipment:
Property, plant & equipment	2,103.9	1,990.4
Less: Accumulated depreciation and amortization	(489.4)	(464.0)
Property, plant and equipment, net of depreciation	1,614.5	1,526.4
Construction work in process	165.9	174.4
Total net property, plant & equipment	1,780.4	1,700.8
Other non-current assets:
Regulatory assets, non-current	166.8	176.8
Intangible assets, net of amortization	43.1	33.7
Other non-current assets	28.1	30.1
Total other non-current assets	238.0	240.6
Total assets	2,275.4	2,171.8
Current liabilities:
Current portion of long-term debt	50.2	65.2
Accounts payable	98.1	111.0
Accrued taxes	85.1	85.1
Accrued interest	15.9	15.3
Security deposits	29.6	15.0
Regulatory liabilities, current	31.0	14.6
Other current liabilities	15.3	17.1
Total current liabilities	325.2	323.3
Non-current liabilities:
Long-term debt	1,534.8	1,395.3
Deferred taxes	191.0	187.9
Taxes payable	40.9	83.6
Regulatory liabilities, non-current	224.7	229.3
Pension, retiree and other benefits	53.7	62.3
Other deferred credits	10.8	11.5
Total non-current liabilities	2,055.9	1,969.9
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	(4.7)	(4.8)
Retained Earnings (Accumulated Deficit)	(2,702.3)	(2,717.9)
Total common shareholder's equity	(105.7)	(121.4)
Total liabilities and shareholder's equity	$ 2,275.4	$ 2,171.8
Common Stock, Shares Authorized	1,500	1,500
Common stock, shares issued	1	1
Common Stock [Member]
Common shareholder's equity:
Total common shareholder's equity	$ 0.0	$ 0.0
Other Additional Capital [Member]
Common shareholder's equity:
Total common shareholder's equity	2,601.3	2,601.3
Subsidiaries [Member]
Current assets:
Cash and cash equivalents	44.9	14.4
Accounts receivable, net	84.8	71.9
Accounts Receivable, Allowance for Credit Loss, Current	0.3	0.3
Inventories	17.9	14.4
Taxes applicable to subsequent years	40.4	83.0
Regulatory assets, current	37.2	24.5
Income Taxes Receivable, Current	27.2	28.1
Prepayments and other current assets	11.2	8.0
Total current assets	263.6	244.3
Property, plant & equipment:
Property, plant & equipment	2,663.5	2,571.3
Less: Accumulated depreciation and amortization	(1,066.5)	(1,062.6)
Property, plant and equipment, net of depreciation	1,597.0	1,508.7
Construction work in process	161.7	170.5
Total net property, plant & equipment	1,758.7	1,679.2
Other non-current assets:
Regulatory assets, non-current	166.8	176.8
Intangible assets, net of amortization	41.8	32.4
Other non-current assets	28.4	29.9
Total other non-current assets	237.0	239.1
Total assets	2,259.3	2,162.6
Current liabilities:
Current portion of long-term debt	0.2	0.2
Accounts payable	97.9	111.5
Accrued taxes	85.1	85.1
Accrued interest	3.3	2.6
Security deposits	29.4	14.9
Regulatory liabilities, current	31.0	14.6
Other current liabilities	12.0	13.0
Total current liabilities	258.9	241.9
Non-current liabilities:
Long-term debt	712.6	574.1
Deferred taxes	189.8	183.4
Taxes payable	40.8	83.5
Regulatory liabilities, non-current	224.7	229.3
Pension, retiree and other benefits	53.7	62.3
Other deferred credits	5.3	5.9
Total non-current liabilities	1,226.9	1,138.5
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	803.5	822.5
Accumulated other comprehensive income	(30.4)	(31.8)
Retained Earnings (Accumulated Deficit)	0.0	(8.9)
Total common shareholder's equity	773.5	782.2
Total liabilities and shareholder's equity	$ 2,259.3	$ 2,162.6
Common Stock, Shares, Outstanding	41,172,173	41,172,173
Common Stock, Shares Authorized	50,000,000	50,000,000
Subsidiaries [Member] | Common Stock [Member]
Common shareholder's equity:
Total common shareholder's equity	$ 0.4
Subsidiaries [Member] | Other Additional Capital [Member]
Common shareholder's equity:
Total common shareholder's equity	$ 803.5