Consolidated Statements of Cash Flows - TNMP - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash Flows From Operating Activities:
Net earnings	$ 106,879	$ 185,180	$ 211,847
Adjustments to reconcile net earnings to net cash flows from operating activities:
Depreciation and amortization	353,692	341,123	320,210
Deferred income tax expense (benefit)	(13,509)	24,533	30,747
Allowance for equity funds used during construction and other, net	(14,978)	(13,799)	(13,217)
Changes in certain assets and liabilities:
Accounts receivable and unbilled revenues	53,229	(73,099)	(25,924)
Materials, supplies, and fuel stock	(31,301)	(8,528)	1,356
Other current assets	(52,225)	17,159	1,838
Other assets	(25,820)	5,002	31,135
Accounts payable	(33,536)	47,568	10,640
Accrued interest and taxes	17,526	9,205	2,692
Other current liabilities	125,580	(28,516)	6,894
Other liabilities	4,963	(27,935)	(29,592)
Net cash flows from operating activities	551,171	567,284	547,873
Cash Flows From Investing Activities:
Additions to utility and non-utility plant	(1,075,812)	(912,557)	(935,016)
Net cash flows used in investing activities	(1,088,406)	(950,347)	(952,258)
Cash Flows From Financing Activities:
Revolving credit facilities borrowings (repayments), net	29,900	169,300	30,700
Long-term borrowings	1,358,096	558,000	1,816,345
Transmission interconnection and security deposit arrangements	49,807	96,550	80,558
Refunds paid under transmission interconnection arrangements	(21,124)	(107,397)	(10,195)
Dividends paid	(126,705)	(119,839)	(112,972)
Debt issuance costs and other, net	(9,836)	(5,564)	(6,306)
Net cash flows from financing activities	537,100	386,037	357,561
Change in Cash, Cash Equivalents, and Restricted Cash	(135)	2,974	(46,824)
Cash, Cash Equivalents, and Restricted Cash at Beginning of Year	4,078	1,104	47,928
Cash, Cash Equivalents, and Restricted Cash at End of Year	3,943	4,078	1,104
Supplemental Cash Flow Disclosures:
Interest paid, net of amounts capitalized	155,273	118,485	91,276
Income taxes paid (refunded), net	1,505	(1,011)	1,042
Supplemental schedule of noncash investing and financing activities:
(Increase) decrease in accrued plant additions	(23,002)	4,455	7,362
TNMP
Cash Flows From Operating Activities:
Net earnings	94,937	92,267	63,879
Adjustments to reconcile net earnings to net cash flows from operating activities:
Depreciation and amortization	113,854	99,165	91,331
Deferred income tax expense (benefit)	2,888	(4,556)	(253)
Allowance for equity funds used during construction and other, net	(5,145)	(4,477)	(3,291)
Changes in certain assets and liabilities:
Accounts receivable and unbilled revenues	1,916	(12,356)	(1,167)
Materials, supplies, and fuel stock	(5,620)	(3,723)	(1,175)
Other current assets	3,650	(264)	(6,132)
Other assets	3,109	3,834	6,989
Accounts payable	171	195	338
Accrued interest and taxes	2,886	14,667	(1,533)
Other current liabilities	(156)	11,952	620
Other liabilities	949	(1,757)	5,545
Net cash flows from operating activities	214,612	194,947	155,151
Cash Flows From Investing Activities:
Additions to utility and non-utility plant	(464,436)	(449,534)	(311,909)
Net cash flows used in investing activities	(464,436)	(449,534)	(311,909)
Cash Flows From Financing Activities:
Revolving credit facilities borrowings (repayments), net	18,400	36,300	400
Long-term borrowings	185,000	160,000	65,000
Transmission interconnection and security deposit arrangements	11,000	6,400	32,700
Refunds paid under transmission interconnection arrangements	(3,500)	(14,150)	(7,302)
Equity contribution from parent	40,900	68,000	52,000
Debt issuance costs and other, net	(1,976)	(1,963)	(840)
Net cash flows from financing activities	249,824	254,587	141,958
Change in Cash, Cash Equivalents, and Restricted Cash	0	0	(14,800)
Cash, Cash Equivalents, and Restricted Cash at Beginning of Year	0	0	14,800
Cash, Cash Equivalents, and Restricted Cash at End of Year	0	0	0
Supplemental Cash Flow Disclosures:
Interest paid, net of amounts capitalized	41,847	33,974	31,599
Income taxes paid (refunded), net	16,904	9,245	13,735
Supplemental schedule of noncash investing and financing activities:
(Increase) decrease in accrued plant additions	$ (17,297)	$ (9,131)	$ (9,131)