Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Cash flows from operating activities:
Net income	$ 2.6	$ 1.2
Adjustments to reconcile net income to net cash provided by / (used in) operating activities:
Depreciation and amortization	22.6	19.8
Amortization of Debt Issuance Costs and Discounts	0.9	1.0
Deferred income taxes	5.7	3.7
Gain (Loss) on Disposition of Business, Including Discontinued Operation	1.3	0.0
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity	(1.8)	(1.4)
Changes in certain assets and liabilities:
Accounts receivable, net	(7.3)	(4.8)
Inventories	(7.5)	(2.5)
Taxes applicable to subsequent years	29.6	24.0
Current and non-current regulatory assets and liabilities	(0.2)	(11.4)
Prepayments and other current assets	(0.7)	(3.9)
Increase (Decrease) in Other Noncurrent Assets	2.3	(1.6)
Accounts payable	6.6	(8.9)
Accrued taxes payable / receivable	(53.2)	(43.8)
Accrued interest	8.9	4.6
Increase (Decrease) in Other Accrued Liabilities	6.9	9.3
Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits	(7.0)	(7.1)
Other	(0.2)	(0.3)
Net Cash Provided by (Used in) Operating Activities	9.5	(22.1)
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(174.6)	(89.4)
Payments for (Proceeds from) Removal Costs	(6.0)	(3.2)
Payments for (Proceeds from) Other Investing Activities	(0.7)	0.2
Net cash used in investing activities	(181.3)	(92.4)
Cash flows from financing activities:
Proceeds from Lines of Credit	185.0	115.0
Repayments of Lines of Credit	(30.0)	(10.0)
Net cash provided by financing activities	155.0	105.0
Cash, cash equivalents, and restricted cash:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	(16.8)	(9.5)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	24.3	21.1
Non-cash financing and investing activities:
Accruals for capital expenditures	55.2	36.4
Supplemental cash flow information:
Interest paid, net of amounts capitalized	11.1	12.9
Subsidiaries [Member]
Cash flows from operating activities:
Net income	9.4	9.6
Adjustments to reconcile net income to net cash provided by / (used in) operating activities:
Depreciation and amortization	22.1	19.4
Amortization of Debt Issuance Costs and Discounts	0.4	0.4
Deferred income taxes	2.3	1.3
Gain (Loss) on Disposition of Business, Including Discontinued Operation	1.1	0.0
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity	(1.8)	(1.4)
Changes in certain assets and liabilities:
Accounts receivable, net	(7.6)	(4.3)
Inventories	(7.0)	(2.5)
Taxes applicable to subsequent years	29.5	24.0
Current and non-current regulatory assets and liabilities	(0.2)	(11.4)
Prepayments and other current assets	0.6	(3.8)
Increase (Decrease) in Other Noncurrent Assets	2.3	(1.5)
Accounts payable	4.9	(9.4)
Accrued taxes payable / receivable	(49.0)	(41.2)
Accrued interest	9.2	4.8
Increase (Decrease) in Other Accrued Liabilities	7.0	9.2
Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits	(7.0)	(7.1)
Other	0.7	0.4
Net Cash Provided by (Used in) Operating Activities	16.9	(13.5)
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(173.1)	(88.8)
Payments for (Proceeds from) Removal Costs	(6.0)	(3.2)
Payments for (Proceeds from) Other Investing Activities	(0.7)	0.2
Net cash used in investing activities	(179.8)	(91.8)
Cash flows from financing activities:
Payments of Dividends	0.0	(15.0)
Proceeds from Lines of Credit	185.0	115.0
Repayments of Lines of Credit	(30.0)	(5.0)
Net cash provided by financing activities	155.0	95.0
Cash, cash equivalents, and restricted cash:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	(7.9)	(10.3)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	7.7	9.5
Non-cash financing and investing activities:
Accruals for capital expenditures	56.2	36.3
Supplemental cash flow information:
Interest paid, net of amounts capitalized	$ 1.9	$ 3.1