Fair Value of Derivative and Other Financial Instruments - Narrative (Details)				1 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended
	Mar. 18, 2022 MW	Feb. 17, 2022 MW	Nov. 15, 2015 power_purchase_agreement	Jun. 30, 2022 MW	Dec. 31, 2022 USD ($) MW	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($) power_purchase_agreement	Dec. 31, 2022 USD ($) MWh MW	Dec. 31, 2021 USD ($) MWh MW power_purchase_agreement	Dec. 31, 2020 USD ($)	May 31, 2022 MW	Jan. 01, 2018 MW
Debt Securities, Available-for-sale [Line Items]
Number of purchase power agreements | power_purchase_agreement							3
Contract in a net liability position					$ 15,300,000			$ 15,300,000
Cash collateral					0			0
Net exposure					$ 13,100,000			13,100,000
Available for sale securities realized impairment losses								$ (25,800,000)	$ 700,000	$ (3,200,000)
Minimum
Debt Securities, Available-for-sale [Line Items]
Investment allocation targets distribution period								10 years
Maximum
Debt Securities, Available-for-sale [Line Items]
Investment allocation targets distribution period								15 years
Equity Securities | Pension Plan
Debt Securities, Available-for-sale [Line Items]
Investment allocation targets					35.00%			35.00%
Alternative Investments | Pension Plan
Debt Securities, Available-for-sale [Line Items]
Investment allocation targets					15.00%			15.00%
Fixed income | Pension Plan
Debt Securities, Available-for-sale [Line Items]
Investment allocation targets					50.00%			50.00%
PNM
Debt Securities, Available-for-sale [Line Items]
Number of purchase power agreements | power_purchase_agreement			2						3
Number of megawatts available in purchase power agreement (in megawatts) | MW	65	327
Expected exposure to market risk (in megawatts) | MW					65			65				65
Power to be sold to third party (in megawatts) | MW					36			36			50	36
Amounts recognized for the legal right to reclaim cash collateral					$ 0		$ 0	$ 0	$ 0
Amounts posted as cash collateral under margin arrangements					10,500,000		500,000	10,500,000	500,000
Obligations to return cash collateral					200,000		900,000	$ 200,000	$ 900,000
Number Of Purchase Power Agreement Not Considered Derivatives | power_purchase_agreement									2
PNM | Natural Gas Cost | Unusual Weather
Debt Securities, Available-for-sale [Line Items]
Cost of energy and production costs						$ 20,000,000
PNM | Electricity, Purchased | Unusual Weather
Debt Securities, Available-for-sale [Line Items]
Cost of energy and production costs						$ 8,000,000
PNM | Commodity Contract | Fair Value Hedging
Debt Securities, Available-for-sale [Line Items]
Power-related contracts (MWh) | MWh								432,200	122,400
PNM | Commodity Contract | Designated as hedging instrument
Debt Securities, Available-for-sale [Line Items]
Derivative asset, fair value, gross liability					0		500,000	$ 0	$ 500,000
Derivative asset, fair value, gross asset					0		500,000	0	500,000
Other current assets					9,780,000		684,000	9,780,000	684,000
Current derivative liability					19,209,000		2,275,000	19,209,000	2,275,000
PNM | Fuel and purchased power costs | Commodity Contract | Designated as hedging instrument
Debt Securities, Available-for-sale [Line Items]
Other current assets					9,800,000		200,000	9,800,000	200,000
Current derivative liability					$ 19,200,000		1,800,000	$ 19,200,000	$ 1,800,000
PNM | Portfolio One
Debt Securities, Available-for-sale [Line Items]
Number of megawatts available in purchase power agreement (in megawatts) | MW				35	270			85	85
PNM | Portfolio Two
Debt Securities, Available-for-sale [Line Items]
Number of megawatts available in purchase power agreement (in megawatts) | MW				25				150	40
PNM | Portfolio Three
Debt Securities, Available-for-sale [Line Items]
Number of megawatts available in purchase power agreement (in megawatts) | MW					40			40	150
PNM | Tri-State
Debt Securities, Available-for-sale [Line Items]
Power to be sold to third party (in megawatts) | MW					100			100
Texas-New Mexico Power Company
Debt Securities, Available-for-sale [Line Items]
Cost of energy and production costs								$ 123,928,000	$ 113,067,000	$ 102,074,000
Texas-New Mexico Power Company | Equity Securities | Pension Plan
Debt Securities, Available-for-sale [Line Items]
Investment allocation targets					16.00%			16.00%
Texas-New Mexico Power Company | Alternative Investments | Pension Plan
Debt Securities, Available-for-sale [Line Items]
Investment allocation targets					14.00%			14.00%
Texas-New Mexico Power Company | Fixed income | Pension Plan
Debt Securities, Available-for-sale [Line Items]
Investment allocation targets					70.00%			70.00%
Measured on a recurring basis | PNM
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale					$ 417,476,000		463,126,000	$ 417,476,000	463,126,000
Nuclear Decommissioning Trust | Measured on a recurring basis | PNM
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale					325,300,000		394,500,000	325,300,000	394,500,000
Mine Reclamation Trust | Measured on a recurring basis | PNM
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale					77,500,000		68,600,000	77,500,000	68,600,000
SJGS Decommissioning Trust | Measured on a recurring basis | PNM
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale					$ 14,700,000		$ 0	$ 14,700,000	$ 0