Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Cash flows from operating activities:
Net income	$ (4.0)	$ 15.6
Adjustments to reconcile net income / (loss) to net cash from operating activities:
Depreciation and amortization	40.3	39.6
Deferred income taxes	7.5	(1.1)
Gain (Loss) on Disposition of Business, Including Discontinued Operation	0.0	(0.6)
Changes in certain assets and liabilities:
Accounts receivable, net	11.3	(13.6)
Inventories	(9.3)	(3.5)
Taxes applicable to subsequent years	45.5	42.7
Current and non-current regulatory assets and liabilities	(26.4)	9.1
Prepayments and other current assets	(9.7)	(2.3)
Accounts payable	(9.5)	3.1
Accrued taxes payable / receivable	(39.0)	(46.0)
Accrued interest	1.2	0.6
Increase (Decrease) in Other Accrued Liabilities	(1.4)	12.9
Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits	(7.2)	(8.5)
Other	6.3	3.9
Net Cash Provided by (Used in) Operating Activities	5.6	51.9
Cash flows from investing activities:
Capital expenditures	(175.8)	(133.9)
Payments for (Proceeds from) Removal Costs	(12.2)	(8.1)
Other investing activities, net	0.3	(0.2)
Net cash used in investing activities	(187.7)	(142.2)
Cash flows from financing activities:
Payments of Deferred Finance Costs	(0.3)	(1.0)
Proceeds from Lines of Credit	130.0	130.0
Repayments of Lines of Credit	(145.0)	(145.0)
Proceeds from Issuance of Long-term Debt	100.0	140.0
Net cash provided by financing activities	196.7	124.0
Cash, cash equivalents, and restricted cash:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	14.6	33.7
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	45.2	60.4
Non-cash financing and investing activities:
Accruals for capital expenditures	36.3	26.6
Supplemental cash flow information:
Interest paid, net of amounts capitalized	34.8	28.7
Proceeds from Contributions from Parent	112.0	0.0
Subsidiaries [Member]
Cash flows from operating activities:
Net income	9.2	24.2
Adjustments to reconcile net income / (loss) to net cash from operating activities:
Depreciation and amortization	39.6	38.9
Deferred income taxes	(0.2)	1.9
Gain (Loss) on Disposition of Business, Including Discontinued Operation	0.0	(0.6)
Changes in certain assets and liabilities:
Accounts receivable, net	12.2	(13.0)
Inventories	(9.3)	(3.5)
Taxes applicable to subsequent years	45.5	42.6
Current and non-current regulatory assets and liabilities	(26.4)	9.1
Prepayments and other current assets	(12.3)	(3.0)
Accounts payable	(6.8)	2.5
Accrued taxes payable / receivable	(38.3)	(41.9)
Accrued interest	1.3	0.6
Increase (Decrease) in Other Accrued Liabilities	(1.7)	12.7
Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits	(7.2)	(8.5)
Other	5.2	4.5
Net Cash Provided by (Used in) Operating Activities	10.8	66.5
Cash flows from investing activities:
Capital expenditures	(174.8)	(133.5)
Payments for (Proceeds from) Removal Costs	(12.2)	(8.0)
Other investing activities, net	0.2	0.5
Net cash used in investing activities	(186.8)	(141.0)
Cash flows from financing activities:
Payments of Dividends	(55.0)	(34.0)
Payments of Deferred Finance Costs	(0.3)	(1.0)
Proceeds from Lines of Credit	130.0	130.0
Repayments of Lines of Credit	(110.0)	(130.0)
Proceeds from Issuance of Long-term Debt	100.0	140.0
Net cash provided by financing activities	189.7	105.0
Cash, cash equivalents, and restricted cash:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	13.7	30.5
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	33.5	45.0
Non-cash financing and investing activities:
Accruals for capital expenditures	36.2	26.6
Supplemental cash flow information:
Interest paid, net of amounts capitalized	16.0	10.0
Proceeds from Contributions from Parent	$ 125.0	$ 0.0