Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Cash flows from operating activities:
Net income	$ 1.2	$ 15.4
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	19.8	19.5
Deferred income taxes	3.7	(0.4)
Gain (Loss) on Disposition of Business, Including Discontinued Operation	0.0	(0.6)
Changes in certain assets and liabilities:
Accounts receivable, net	(4.8)	(2.3)
Inventories	(2.5)	(3.0)
Taxes applicable to subsequent years	24.0	22.3
Current and non-current regulatory assets and liabilities	(11.4)	10.4
Accounts payable	(8.9)	(15.7)
Accrued taxes payable / receivable	(43.8)	(43.3)
Accrued interest	4.6	3.0
Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits	(7.1)	(8.0)
Other	3.1	2.5
Net Cash Provided by (Used in) Operating Activities	(22.1)	(0.2)
Cash flows from investing activities:
Capital expenditures	(89.4)	(64.4)
Payments for (Proceeds from) Removal Costs	(3.2)	(5.0)
Other investing activities, net	0.2	0.1
Net cash used in investing activities	(92.4)	(69.3)
Cash flows from financing activities:
Proceeds from Lines of Credit	115.0	95.0
Repayments of Lines of Credit	(10.0)	(20.0)
Net cash provided by financing activities	105.0	75.0
Cash, cash equivalents, and restricted cash:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	(9.5)	5.5
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	21.1	32.2
Non-cash financing and investing activities:
Accruals for capital expenditures	36.4	23.7
Supplemental cash flow information:
Interest paid, net of amounts capitalized	12.9	11.3
Subsidiaries [Member]
Cash flows from operating activities:
Net income	9.6	16.9
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	19.4	19.2
Deferred income taxes	1.3	2.0
Gain (Loss) on Disposition of Business, Including Discontinued Operation	0.0	(0.6)
Changes in certain assets and liabilities:
Accounts receivable, net	(4.3)	(1.7)
Inventories	(2.5)	(3.0)
Taxes applicable to subsequent years	24.0	22.3
Current and non-current regulatory assets and liabilities	(11.4)	10.4
Accounts payable	(9.4)	(16.7)
Accrued taxes payable / receivable	(41.2)	(38.8)
Accrued interest	4.8	3.3
Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits	(7.1)	(8.0)
Other	3.3	0.9
Net Cash Provided by (Used in) Operating Activities	(13.5)	6.2
Cash flows from investing activities:
Capital expenditures	(88.8)	(64.2)
Payments for (Proceeds from) Removal Costs	(3.2)	(5.0)
Other investing activities, net	0.2	0.5
Net cash used in investing activities	(91.8)	(68.7)
Cash flows from financing activities:
Payments of Dividends	(15.0)	(9.0)
Proceeds from Lines of Credit	115.0	95.0
Repayments of Lines of Credit	(5.0)	(20.0)
Net cash provided by financing activities	95.0	66.0
Cash, cash equivalents, and restricted cash:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	(10.3)	3.5
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	9.5	18.0
Non-cash financing and investing activities:
Accruals for capital expenditures	36.3	23.6
Supplemental cash flow information:
Interest paid, net of amounts capitalized	$ 3.1	$ 1.8