Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Cash flows from operating activities:
Net income	$ 15.6	$ 14.0
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	39.6	38.0
Deferred income taxes	(1.1)	4.6
Gain (Loss) on Disposition of Business, Including Discontinued Operation	(0.6)	0.0
Changes in certain assets and liabilities:
Accounts receivable, net	(13.6)	4.4
Inventories	(3.5)	(0.6)
Taxes applicable to subsequent years	42.7	39.2
Deferred regulatory costs, net	9.1	(9.8)
Prepayments and other current assets	(2.3)	(5.7)
Accounts payable	3.1	4.1
Accrued taxes payable / receivable	(46.0)	(57.5)
Accrued interest	0.6	(0.4)
Increase (Decrease) in Other Accrued Liabilities	12.9	(3.7)
Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits	(8.5)	(11.4)
Other	3.9	1.5
Net Cash Provided by (Used in) Operating Activities	51.9	16.7
Cash flows from investing activities:
Capital expenditures	(133.9)	(94.9)
Payments for (Proceeds from) Removal Costs	(8.1)	(9.2)
Other investing activities, net	(0.2)	(0.9)
Net cash used in investing activities	(142.2)	(105.0)
Cash flows from financing activities:
Payments of Deferred Finance Costs	(1.0)	(0.4)
Proceeds from Lines of Credit	130.0	80.0
Repayments of Lines of Credit	(145.0)	0.0
Proceeds from Issuance of Long-term Debt	140.0	0.0
Net cash provided by financing activities	124.0	79.6
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	33.7	(8.7)
Cash, cash equivalents, and restricted cash:
Restricted Cash and Cash Equivalents	60.4	16.8
Non-cash financing and investing activities:
Accruals for capital expenditures	26.6	15.8
Supplemental cash flow information:
Interest paid, net of amounts capitalized	28.7	29.6
Subsidiaries [Member]
Cash flows from operating activities:
Net income	24.2	26.9
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	38.9	37.2
Deferred income taxes	1.9	3.7
Gain (Loss) on Disposition of Business, Including Discontinued Operation	(0.6)	0.0
Changes in certain assets and liabilities:
Accounts receivable, net	(13.0)	5.3
Inventories	(3.5)	(0.6)
Taxes applicable to subsequent years	42.6	38.9
Deferred regulatory costs, net	9.1	(9.8)
Prepayments and other current assets	(3.0)	(6.7)
Accounts payable	2.5	2.6
Accrued taxes payable / receivable	(41.9)	(52.0)
Accrued interest	0.6	0.3
Increase (Decrease) in Other Accrued Liabilities	12.7	(3.8)
Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits	(8.5)	(11.4)
Other	4.5	2.0
Net Cash Provided by (Used in) Operating Activities	66.5	32.6
Cash flows from investing activities:
Capital expenditures	(133.5)	(94.0)
Payments for (Proceeds from) Removal Costs	(8.0)	(9.2)
Other investing activities, net	0.5	0.9
Net cash used in investing activities	(141.0)	(102.3)
Cash flows from financing activities:
Payments of Deferred Finance Costs	(1.0)	(0.2)
Proceeds from Lines of Credit	130.0	80.0
Repayments of Lines of Credit	(130.0)	0.0
Proceeds from Issuance of Long-term Debt	140.0	0.0
Net cash provided by financing activities	105.0	62.8
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	30.5	(6.9)
Cash, cash equivalents, and restricted cash:
Restricted Cash and Cash Equivalents	45.0	4.9
Non-cash financing and investing activities:
Accruals for capital expenditures	26.6	15.7
Supplemental cash flow information:
Interest paid, net of amounts capitalized	10.0	10.2
Payments of Dividends	$ (34.0)	$ (17.0)