Regulatory and Rate Matters - SJGS Abandonment Application (Details) $ in Millions		12 Months Ended
	Jul. 01, 2019 USD ($)	Dec. 31, 2021 USD ($) MW	Apr. 02, 2021 MW	Dec. 31, 2020 USD ($)	Nov. 13, 2020 MW	Sep. 28, 2020 USD ($)	Jul. 29, 2020 MW	Mar. 31, 2020 USD ($)	Feb. 21, 2020 USD ($)	May 31, 2019 MW
PNM Solar Direct
Public Utilities, General Disclosures [Line Items]
Solar distributed generation (in mw) | MW										50
Public Service Company of New Mexico
Public Utilities, General Disclosures [Line Items]
Solar distributed generation (in mw) | MW							650
Number of megawatts in battery storage facilities (in megawatts) | MW							300
Public Service Company of New Mexico | Replacement Resource Portfolio One
Public Utilities, General Disclosures [Line Items]
Solar distributed generation (in mw) | MW			150		200
Number of megawatts in battery storage facilities (in megawatts) | MW			40		100
Public Service Company of New Mexico | Replacement Resource Portfolio Two
Public Utilities, General Disclosures [Line Items]
Solar distributed generation (in mw) | MW					100
Number of megawatts in battery storage facilities (in megawatts) | MW			100		30
Public Service Company of New Mexico | Portfolio One
Public Utilities, General Disclosures [Line Items]
Number of megawatts available in purchase power agreement (in megawatts) | MW		85
Public Service Company of New Mexico | Portfolio Two
Public Utilities, General Disclosures [Line Items]
Number of megawatts available in purchase power agreement (in megawatts) | MW		150
Public Service Company of New Mexico | Portfolio Three
Public Utilities, General Disclosures [Line Items]
Number of megawatts available in purchase power agreement (in megawatts) | MW		40
San Juan Generating Station
Public Utilities, General Disclosures [Line Items]
Estimated costs of replacement resources						$ 8.1
San Juan Generating Station | Other deferred credits
Public Utilities, General Disclosures [Line Items]
Restructuring reserve		$ 36.9		$ 38.1
San Juan Generating Station | Employee Severance
Public Utilities, General Disclosures [Line Items]
Restructuring reserve								$ 9.4
San Juan Generating Station | Public Service Company of New Mexico
Public Utilities, General Disclosures [Line Items]
Request issuance of energy transition bonds	$ 361.0
Forecasted undepreciated investment		283.0							$ 361.0
Plant decommissioning and coal mine reclamation costs		28.6
Upfront financing costs		9.6
Severance costs		20.0
Proceeds from securitization bonds	$ 19.8
San Juan Generating Station | Public Service Company of New Mexico | Other deferred credits
Public Utilities, General Disclosures [Line Items]
Restructuring reserve		$ 36.0		$ 36.8
San Juan Generating Station | Public Service Company of New Mexico | Employee Severance
Public Utilities, General Disclosures [Line Items]
Restructuring reserve								8.1
San Juan Generating Station | Public Service Company of New Mexico | Other Restructuring
Public Utilities, General Disclosures [Line Items]
Restructuring reserve								8.9
San Juan Generating Station | Public Service Company of New Mexico | Economic Development and Workforce Training Costs
Public Utilities, General Disclosures [Line Items]
Restructuring reserve								$ 19.8