Fair Value of Derivative and Other Financial Instruments - Narrative (Details)		1 Months Ended	3 Months Ended	12 Months Ended
	Apr. 17, 2023 MW	Jun. 30, 2022 MW	Dec. 31, 2023 USD ($) MW	Dec. 31, 2023 USD ($) MW	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($) MW power_purchase_agreement	May 31, 2022 MW	Jan. 01, 2018 MW
Debt Securities, Available-for-sale [Line Items]
Contractual Liability			$ 0	$ 0	$ 15,288,000
Existing Cash Collateral			0	0	0
Net Exposure			$ 0	0	13,087,000
Available for sale securities realized impairment losses				$ 19,100,000	(25,800,000)	$ 700,000
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						3
Number of purchase power agreement not considered derivatives | power_purchase_agreement						2
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
Amounts posted as cash collateral under margin arrangements			200,000	200,000	10,500,000
Obligations to return cash collateral					200,000
PNM | Commodity Contract | Designated as hedging instrument
Debt Securities, Available-for-sale [Line Items]
Derivative asset, fair value, gross liability			0	0
Derivative asset, fair value, gross asset			0	0
Other current assets			826,000	826,000	9,780,000
Current derivative liability			0	0	19,209,000
PNM | Fuel and purchased power costs | Commodity Contract | Designated as hedging instrument
Debt Securities, Available-for-sale [Line Items]
Other current assets			800,000	800,000	9,800,000
Current derivative liability			$ 0	$ 0	19,200,000
PNM | Portfolio One
Debt Securities, Available-for-sale [Line Items]
Number of megawatts available in purchase power agreement (in megawatts) | MW	420	85				85
PNM | Portfolio Two
Debt Securities, Available-for-sale [Line Items]
Number of megawatts available in purchase power agreement (in megawatts) | MW			40	375		40
PNM | Portfolio Three
Debt Securities, Available-for-sale [Line Items]
Number of megawatts available in purchase power agreement (in megawatts) | MW						150
PNM | Tri-State
Debt Securities, Available-for-sale [Line Items]
Power to be sold to third party (in megawatts) | MW			100	100
TNMP | Equity Securities | Pension Plan
Debt Securities, Available-for-sale [Line Items]
Investment allocation targets			16.00%	16.00%
TNMP | Alternative Investments | Pension Plan
Debt Securities, Available-for-sale [Line Items]
Investment allocation targets			14.00%	14.00%
TNMP | 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			$ 444,408,000	$ 444,408,000	417,476,000
Nuclear Decommissioning Trust | Measured on a recurring basis | PNM
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale			361,000,000	361,000,000	325,300,000
Mine Reclamation Trust | Measured on a recurring basis | PNM
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale			71,100,000	71,100,000	77,500,000
SJGS Decommissioning Trust | Measured on a recurring basis | PNM
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale			$ 12,300,000	$ 12,300,000	$ 14,700,000