Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Cash flows from operating activities:
Net income	$ 34.6	$ (4.1)
Adjustments to reconcile net income / (loss) to Net cash provided by operating activities:
Depreciation and amortization	60.9	59.6
Deferred income taxes	20.9	(10.7)
Gain (Loss) on Disposition of Business, Including Discontinued Operation	0.0	(0.6)
Changes in certain assets and liabilities:
Accounts receivable, net	6.8	(18.0)
Inventories	(11.2)	(6.5)
Taxes applicable to subsequent years	69.9	62.9
Current and non-current regulatory assets and liabilities	(67.8)	55.4
Prepayments and other current assets	(5.5)	(3.9)
Increase (Decrease) in Other Noncurrent Assets	3.7	5.9
Accounts payable	(36.4)	(5.7)
Accrued taxes payable / receivable	(71.9)	(77.8)
Accrued interest	6.8	5.1
Increase (Decrease) in Other Accrued Liabilities	15.5	0.6
Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits	(7.1)	(9.2)
Other	(2.3)	(1.0)
Net Cash Provided by (Used in) Operating Activities	16.9	52.0
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(286.0)	(193.0)
Payments for (Proceeds from) Removal Costs	(16.0)	(14.7)
Other investing activities, net	0.2	(0.1)
Net cash used in investing activities	(301.8)	(207.8)
Cash flows from financing activities:
Payments of Deferred Finance Costs	(0.3)	(1.5)
Proceeds from Lines of Credit	205.0	185.0
Repayments of Lines of Credit	(240.0)	(150.0)
Proceeds from Issuance of Long-term Debt	100.0	140.0
Net cash provided by financing activities	303.7	173.5
Cash, cash equivalents, and restricted cash:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	18.8	17.7
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	49.4	44.4
Non-cash financing and investing activities:
Accruals for capital expenditures	46.2	31.4
Supplemental cash flow information:
Interest paid, net of amounts capitalized	47.2	41.3
Proceeds from Contributions from Parent	239.0	0.0
Subsidiaries [Member]
Cash flows from operating activities:
Net income	52.8	14.1
Adjustments to reconcile net income / (loss) to Net cash provided by operating activities:
Depreciation and amortization	59.9	58.7
Deferred income taxes	11.3	(6.9)
Gain (Loss) on Disposition of Business, Including Discontinued Operation	0.0	(0.6)
Changes in certain assets and liabilities:
Accounts receivable, net	7.9	(17.7)
Inventories	(11.2)	(6.5)
Taxes applicable to subsequent years	69.8	62.8
Current and non-current regulatory assets and liabilities	(67.8)	55.4
Prepayments and other current assets	(7.1)	(4.5)
Increase (Decrease) in Other Noncurrent Assets	4.1	5.7
Accounts payable	(37.3)	(6.8)
Accrued taxes payable / receivable	(77.1)	(75.9)
Accrued interest	7.1	5.3
Increase (Decrease) in Other Accrued Liabilities	15.3	0.2
Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits	(7.1)	(9.2)
Other	(2.8)	(0.8)
Net Cash Provided by (Used in) Operating Activities	17.8	73.3
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(283.4)	(191.0)
Payments for (Proceeds from) Removal Costs	(16.0)	(14.5)
Other investing activities, net	0.2	0.4
Net cash used in investing activities	(299.2)	(205.1)
Cash flows from financing activities:
Payments of Dividends	(65.0)	(49.0)
Payments of Deferred Finance Costs	(0.3)	(1.0)
Proceeds from Lines of Credit	205.0	185.0
Repayments of Lines of Credit	(205.0)	(130.0)
Proceeds from Issuance of Long-term Debt	100.0	140.0
Net cash provided by financing activities	294.7	145.0
Cash, cash equivalents, and restricted cash:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	13.3	13.2
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	33.1	27.7
Non-cash financing and investing activities:
Accruals for capital expenditures	46.2	31.2
Supplemental cash flow information:
Interest paid, net of amounts capitalized	19.2	12.9
Proceeds from Contributions from Parent	$ 260.0	$ 0.0