Income Taxes - Schedule of Deferred Income Tax Components (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Taxes [Line Items]
Net change in deferred income tax liability per above table	$ 22,449
Change in tax effects of income tax related regulatory assets and liabilities	(11,791)
Amortization of excess deferred income tax	(22,859)
Tax effect of mark-to-market adjustments	474
Tax effect of excess pension liability	(1,566)
Adjustment for uncertain income tax positions	(17)
Reclassification of unrecognized tax benefits	17
Other	(216)
Deferred income tax (benefit)	(13,509)	$ 24,533	$ 30,747
PNM
Income Taxes [Line Items]
Net change in deferred income tax liability per above table	1,997
Change in tax effects of income tax related regulatory assets and liabilities	(9,391)
Amortization of excess deferred income tax	(14,252)
Tax effect of mark-to-market adjustments	(1,099)
Tax effect of excess pension liability	(1,566)
Adjustment for uncertain income tax positions	(55)
Reclassification of unrecognized tax benefits	2,394
Deferred income tax (benefit)	(21,972)	29,487	27,120
TNMP
Income Taxes [Line Items]
Net change in deferred income tax liability per above table	14,111
Change in tax effects of income tax related regulatory assets and liabilities	(2,400)
Amortization of excess deferred income tax	(8,607)
Other	(216)
Deferred income tax (benefit)	$ 2,888	$ (4,556)	$ (253)