Statement of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
OPERATING ACTIVITIES:
Net income	$ 135,059	$ 94,974
Adjustments to reconcile net cash provided (used) by operating activities:
Depreciation and amortization	83,852	85,659
Regulatory charges resulting from tax rate changes	0	17,637
Allowance for equity funds used during construction (equity AFUDC)	(2,085)	(1,853)
Changes in current assets and liabilities:
Trade and other accounts receivable	4,963	3,911
Affiliate receivables	280	109
Materials and supplies	137	58
Regulatory assets	(260)	(374)
Other current assets	189	(75)
Trade accounts payable	(173)	(890)
Affiliate payables	(3,032)	(2,513)
Regulatory liabilities	(125,502)	137,451
Other accrued liabilities	9,176	6,675
Other, including changes in long-term assets and liabilities:
Regulatory assets	(21,870)	(4,458)
Regulatory liabilities	(14,647)	(133,578)
Other, net	3,442	3,678
Net cash provided (used) by operating activities	69,529	206,411
FINANCING ACTIVITIES:
Cash distributions to parent	(134,800)	(108,000)
Net cash provided (used) by financing activities	(134,800)	(108,000)
Property, plant and equipment:
Capital expenditures	(77,263)	(60,637)
Contributions and advances for construction costs	3,445	10,042
Disposal of property, plant and equipment, net	(7,238)	(4,462)
Advances to affiliate, net	146,327	(43,354)
Net cash provided (used) by investing activities	65,271	(98,411)
Increase (decrease) in cash	0	0
Cash at beginning of period	0	0
Cash at end of period	0	0
Additional Cash Flow Elements and Supplemental Cash Flow Information [Abstract]
Increases to property, plant and equipment, exclusive of equity AFUDC	(98,340)	(73,267)
Changes in related accounts payable and accrued liabilities	21,077	12,630
Capital expenditures	$ (77,263)	$ (60,637)