Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating loss	$ 16,833	$ 85,382
Regulatory liabilities related to income taxes	90,461	98,371
Federal tax credit carryforwards	124,510	122,557
Regulatory disallowances	42,330	28,037
Regulatory liability SJGS retirement credits	28,797	0
Other	35,492	33,849
Total deferred tax assets	338,423	368,196
Deferred tax liabilities:
Depreciation and plant related	(738,078)	(801,022)
Investment tax credit	(95,046)	(96,227)
Regulatory assets related to income taxes	(80,643)	(77,013)
Pension	(41,141)	(40,651)
Regulatory asset for shutdown of SJGS Units 2 and 3	(22,454)	(24,048)
Regulatory asset SJGS energy transition property	(86,521)	(69,828)
Regulatory asset PVNGS investment	(20,503)	0
PVNGS trusts	(41,767)	(26,084)
Other	(57,550)	(56,154)
Total deferred tax liabilities	(1,183,703)	(1,191,027)
Net accumulated deferred income tax liabilities	(845,280)	(822,831)
PNM
Deferred tax assets:
Net operating loss	0	54,681
Regulatory liabilities related to income taxes	71,546	76,744
Federal tax credit carryforwards	80,586	84,902
Regulatory disallowances	42,330	28,037
Regulatory liability SJGS retirement credits	28,797	0
Other	35,993	33,079
Total deferred tax assets	259,252	277,443
Deferred tax liabilities:
Depreciation and plant related	(545,815)	(620,814)
Investment tax credit	(73,844)	(74,015)
Regulatory assets related to income taxes	(71,742)	(67,912)
Pension	(36,483)	(36,048)
Regulatory asset for shutdown of SJGS Units 2 and 3	(22,454)	(24,048)
Regulatory asset SJGS energy transition property	(86,521)	(69,828)
Regulatory asset PVNGS investment	(20,503)	0
PVNGS trusts	(41,767)	(26,084)
Other	(44,160)	(40,734)
Total deferred tax liabilities	(943,289)	(959,483)
Net accumulated deferred income tax liabilities	(684,037)	(682,040)
TNMP
Deferred tax assets:
Regulatory liabilities related to income taxes	18,915	21,627
Other	5,534	5,353
Total deferred tax assets	24,449	26,980
Deferred tax liabilities:
Depreciation and plant related	(179,483)	(166,230)
Regulatory assets related to income taxes	(8,901)	(9,213)
Loss on reacquired debt	(5,254)	(5,527)
Pension	(4,659)	(4,603)
AMS	(2,613)	(3,989)
Other	(2,287)	(2,055)
Total deferred tax liabilities	(203,197)	(191,617)
Net accumulated deferred income tax liabilities	$ (178,748)	$ (164,637)