Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Taxes [Line Items]
Federal income tax at statutory rates	$ 51,330	$ 43,670	$ 14,038
Amortization of accumulated investment tax credits	(1,247)	(890)	(522)
Amortization of excess deferred income tax	(24,484)	(30,723)	(37,799)
Flow-through of depreciation items	798	1,368	1,136
Earnings attributable to non-controlling interest in Valencia	(3,253)	(2,943)	(2,991)
State income tax, net of federal (benefit)	9,660	6,961	298
Allowance for equity funds used during construction	(2,776)	(2,363)	(1,990)
Regulatory recovery of prior year impairments of state net operating loss carryforward, including amortization	0	1,367	1,367
Tax benefit related to stock compensation awards	(788)	(392)	(795)
Non-deductible compensation	899	2,630	1,156
Transaction costs	848	0	0
Other	1,595	1,951	820
Total income taxes (benefit)	$ 32,582	$ 20,636	$ (25,282)
Effective tax rate	13.33%	9.92%	(37.82%)
Public Service Company of New Mexico
Income Taxes [Line Items]
Federal income tax at statutory rates	$ 41,696	$ 38,193	$ 6,187
Amortization of accumulated investment tax credits	(237)	(243)	(247)
Amortization of excess deferred income tax	(15,158)	(21,609)	(28,923)
Flow-through of depreciation items	689	1,279	1,077
Earnings attributable to non-controlling interest in Valencia	(3,253)	(2,943)	(2,991)
State income tax, net of federal (benefit)	7,609	7,111	92
Allowance for equity funds used during construction	(2,080)	(1,461)	(1,398)
Regulatory recovery of prior year impairments of state net operating loss carryforward, including amortization	0	1,367	1,367
Tax benefit related to stock compensation awards	(563)	(279)	(559)
Non-deductible compensation	547	1,554	683
Transaction costs	22	0	0
Other	(2,280)	(1,112)	(1,250)
Total income taxes (benefit)	$ 26,992	$ 21,857	$ (25,962)
Effective tax rate	13.59%	12.02%	(88.13%)
Texas-New Mexico Power Company
Income Taxes [Line Items]
Federal income tax at statutory rates	$ 15,076	$ 13,628	$ 12,778
Amortization of excess deferred income tax	(9,326)	(9,113)	(8,876)
State income tax, net of federal (benefit)	1,763	1,625	1,532
Tax benefit related to stock compensation awards	(224)	(112)	(236)
Non-deductible compensation	351	1,071	471
Transaction costs	(4)	0	0
Other	276	(791)	(623)
Total income taxes (benefit)	$ 7,912	$ 6,308	$ 5,046
Effective tax rate	11.02%	9.71%	8.29%