Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Cash flows from operating activities:
Net income	$ 12.8	$ (4.0)
Adjustments to reconcile net income / (loss) to net cash provided by operating activities:
Depreciation and amortization	43.7	40.3
Amortization of Debt Issuance Costs and Discounts	1.7	1.9
Deferred income taxes	12.0	7.5
Gain (Loss) on Disposition of Business, Including Discontinued Operation	1.3	0.0
Public Utilities, Allowance for Funds Used During Construction, Additions	(4.0)	(2.5)
Changes in certain assets and liabilities:
Accounts receivable, net	(1.9)	11.3
Inventories	(13.1)	(9.3)
Taxes applicable to subsequent years	60.0	45.5
Current and non-current regulatory assets and liabilities	(9.5)	(26.4)
Prepayments and other current assets	(2.8)	(9.7)
Increase (Decrease) in Other Noncurrent Assets	8.7	7.1
Accounts payable	10.9	(9.5)
Accrued taxes payable / receivable	(63.7)	(39.0)
Accrued interest	6.0	1.2
Increase (Decrease) in Other Accrued Liabilities	7.0	(1.4)
Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits	(6.6)	(7.2)
Other	(0.1)	(0.2)
Net Cash Provided by (Used in) Operating Activities	62.4	5.6
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(289.1)	(175.8)
Payments for (Proceeds from) Removal Costs	(15.3)	(12.2)
Payments for (Proceeds from) Other Investing Activities	(0.6)	0.3
Net cash used in investing activities	(305.0)	(187.7)
Cash flows from financing activities:
Payments of Deferred Finance Costs	0.0	(0.3)
Proceeds from Lines of Credit	230.0	130.0
Repayments of Lines of Credit	(110.0)	(145.0)
Proceeds from Issuance of Long-term Debt	0.0	100.0
Net cash provided by financing activities	250.0	196.7
Cash, cash equivalents, and restricted cash:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	7.4	14.6
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	48.5	45.2
Non-cash financing and investing activities:
Accruals for capital expenditures	94.6	36.3
Supplemental cash flow information:
Interest paid, net of amounts capitalized	34.7	34.8
Proceeds from Contributions from Parent	130.0	112.0
Subsidiaries [Member]
Cash flows from operating activities:
Net income	24.5	9.2
Adjustments to reconcile net income / (loss) to net cash provided by operating activities:
Depreciation and amortization	42.8	39.6
Amortization of Debt Issuance Costs and Discounts	0.7	0.9
Deferred income taxes	6.1	(0.2)
Gain (Loss) on Disposition of Business, Including Discontinued Operation	1.1	0.0
Public Utilities, Allowance for Funds Used During Construction, Additions	(4.0)	(2.5)
Changes in certain assets and liabilities:
Accounts receivable, net	(0.6)	12.2
Inventories	(12.1)	(9.3)
Taxes applicable to subsequent years	59.9	45.5
Current and non-current regulatory assets and liabilities	(9.5)	(26.4)
Prepayments and other current assets	(1.4)	(12.3)
Increase (Decrease) in Other Noncurrent Assets	9.7	6.3
Accounts payable	11.1	(6.8)
Accrued taxes payable / receivable	(53.9)	(38.3)
Accrued interest	6.0	1.3
Increase (Decrease) in Other Accrued Liabilities	6.5	(1.7)
Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits	(6.6)	(7.2)
Other	1.4	0.5
Net Cash Provided by (Used in) Operating Activities	81.7	10.8
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(288.1)	(174.8)
Payments for (Proceeds from) Removal Costs	(15.3)	(12.2)
Payments for (Proceeds from) Other Investing Activities	(0.6)	0.2
Net cash used in investing activities	(304.0)	(186.8)
Cash flows from financing activities:
Payments of Dividends	(21.0)	(55.0)
Payments of Deferred Finance Costs	0.0	(0.3)
Proceeds from Lines of Credit	230.0	130.0
Repayments of Lines of Credit	(110.0)	(110.0)
Proceeds from Issuance of Long-term Debt	0.0	100.0
Net cash provided by financing activities	229.0	189.7
Cash, cash equivalents, and restricted cash:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	6.7	13.7
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	22.3	33.5
Non-cash financing and investing activities:
Accruals for capital expenditures	94.5	36.2
Supplemental cash flow information:
Interest paid, net of amounts capitalized	16.8	16.0
Proceeds from Contributions from Parent	$ 130.0	$ 125.0