Regulatory and Rate Matters - SJGS, Fours Corners and PVNGS Leased Interest Abandonment Applications (Details) $ in Thousands								1 Months Ended	3 Months Ended	6 Months Ended	12 Months Ended
	Mar. 18, 2022 MW	Feb. 17, 2022 MW	Apr. 02, 2021 lease MW	Feb. 03, 2021	Jan. 08, 2021 USD ($)	Nov. 01, 2020 USD ($)	Jul. 01, 2019 USD ($)	Nov. 30, 2020 USD ($)	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($) MW power_purchase_agreement	Dec. 31, 2021 USD ($) power_purchase_agreement MW	Apr. 14, 2022 MW	Dec. 18, 2020 USD ($)	Nov. 13, 2020 MW	Sep. 28, 2020 USD ($)	Jul. 29, 2020 MW	Mar. 31, 2020 USD ($)	Feb. 21, 2020 USD ($)
Public Utilities, General Disclosures [Line Items]
Regulatory time frame for proposed PPAs and battery storage agreements			6 months
Number of purchase power agreements | power_purchase_agreement										3
Regulatory assets									$ 511,639	$ 514,258	$ 514,258
Regulatory liabilities									845,701	841,393	$ 841,393
COVID-19
Public Utilities, General Disclosures [Line Items]
Temporary mandatory moratorium on disconnection period				100 days
Disconnection transition period				90 days
PNM
Public Utilities, General Disclosures [Line Items]
Solar generation capacity (in megawatts) | MW																650
Number of megawatts in battery storage facilities (in megawatts) | MW																300
Number of purchase power agreements | power_purchase_agreement											3
Number of megawatts available in purchase power agreement (in megawatts) | MW	65	327
Number of leases under which lease term was extended | lease			5
Regulatory assets									426,177	428,981	$ 428,981
Regulatory liabilities									$ 651,495	653,830	653,830
PNM | Minimum
Public Utilities, General Disclosures [Line Items]
Reserve margin	20.70%	17.40%							0.90%
PNM | Maximum
Public Utilities, General Disclosures [Line Items]
Reserve margin	12.50%	9.80%							3.40%
PNM | Four Corners
Public Utilities, General Disclosures [Line Items]
Request issuance of energy transition bonds					$ 300,000
Forecasted undepreciated investment					272,000
Plant decommissioning and coal mine reclamation costs					4,600
Upfront financing costs					7,300
Proceeds from securitization bonds					$ 16,500
Payments for relief from obligations						$ 75,000		$ 15,000
Final payment for relief from obligations								60,000
Initial payment for relief from obligations								$ 15,000
PNM | Four Corners | PNM
Public Utilities, General Disclosures [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners						13.00%
PNM | COVID-19 | COVID-19 Costs Savings
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities									$ 900	900	900
PNM | Deferred COVID-19 Costs | COVID-19
Public Utilities, General Disclosures [Line Items]
Regulatory assets									6,800	$ 6,900	$ 6,900
PNM | NMPRC
Public Utilities, General Disclosures [Line Items]
Solar generation capacity, amount requested for approval to abandon (in megawatts) | MW			114
PNM | Leased Interest Termination on January 15, 2023
Public Utilities, General Disclosures [Line Items]
Number of leases under which lease term was extended | lease			4
PNM | Leased Interest Termination on January 15, 2023 | NMPRC
Public Utilities, General Disclosures [Line Items]
Solar generation capacity (in megawatts) | MW			104
PNM | Leased Interest Termination on January 15, 2024 | NMPRC
Public Utilities, General Disclosures [Line Items]
Solar generation capacity (in megawatts) | MW			10
PNM | Replacement Resource Portfolio One
Public Utilities, General Disclosures [Line Items]
Solar generation capacity (in megawatts) | MW			150											200
Number of megawatts in battery storage facilities (in megawatts) | MW			40											100
PNM | Replacement Resource Portfolio One | Subsequent event
Public Utilities, General Disclosures [Line Items]
Solar generation capacity (in megawatts) | MW												150
Number of megawatts in battery storage facilities (in megawatts) | MW												40
PNM | Replacement Resource Portfolio Two
Public Utilities, General Disclosures [Line Items]
Solar generation capacity (in megawatts) | MW														100
Number of megawatts in battery storage facilities (in megawatts) | MW			100											30
PNM | Replacement Resource Portfolio Two | Subsequent event
Public Utilities, General Disclosures [Line Items]
Number of megawatts in battery storage facilities (in megawatts) | MW												100
PNM | Replacement Resource Portfolio Three
Public Utilities, General Disclosures [Line Items]
Solar generation capacity (in megawatts) | MW			300
Number of megawatts in battery storage facilities (in megawatts) | MW			150
PNM | Replacement Resource Portfolio Three | Subsequent event
Public Utilities, General Disclosures [Line Items]
Solar generation capacity (in megawatts) | MW												300
Number of megawatts in battery storage facilities (in megawatts) | MW												150
PNM | Transportation Electrification Program
Public Utilities, General Disclosures [Line Items]
Expected budgeted expenditures													$ 8,400
Budget flexibility													25.00%
Budget portion dedicated to low and moderate income customers													25.00%
PNM | Portfolio One
Public Utilities, General Disclosures [Line Items]
Number of megawatts available in purchase power agreement (in megawatts) | MW										85	85
PNM | Portfolio Two
Public Utilities, General Disclosures [Line Items]
Number of megawatts available in purchase power agreement (in megawatts) | MW										150	150
PNM | Portfolio Three
Public Utilities, General Disclosures [Line Items]
Number of megawatts available in purchase power agreement (in megawatts) | MW										40	40
San Juan Generating Station
Public Utilities, General Disclosures [Line Items]
Severance costs									8,900
Estimated costs of replacement resources															$ 8,100
San Juan Generating Station | Other deferred credits
Public Utilities, General Disclosures [Line Items]
Restructuring reserve									36,800	$ 36,900	$ 36,900
San Juan Generating Station | Employee Severance
Public Utilities, General Disclosures [Line Items]
Restructuring reserve									27,700								$ 9,400
San Juan Generating Station | PNM
Public Utilities, General Disclosures [Line Items]
Request issuance of energy transition bonds							$ 361,000
Forecasted undepreciated investment							283,000											$ 361,000
Plant decommissioning and coal mine reclamation costs							28,600
Upfront financing costs							9,600
Severance costs							20,000
Proceeds from securitization bonds							$ 19,800
San Juan Generating Station | PNM | Other deferred credits
Public Utilities, General Disclosures [Line Items]
Restructuring reserve									35,900	$ 36,000	$ 36,000
San Juan Generating Station | PNM | Employee Severance
Public Utilities, General Disclosures [Line Items]
Restructuring reserve									$ 26,800								8,100
San Juan Generating Station | PNM | Other Restructuring
Public Utilities, General Disclosures [Line Items]
Restructuring reserve																	8,900
San Juan Generating Station | PNM | Economic Development and Workforce Training Costs
Public Utilities, General Disclosures [Line Items]
Restructuring reserve																	$ 19,800