Financing - Short-term Debt and Liquidity (Details)			1 Months Ended
	Jul. 01, 2024 USD ($)	Apr. 01, 2024 USD ($) extension_option	Feb. 28, 2025 USD ($)	Aug. 30, 2024 USD ($)	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	May 20, 2022 USD ($)	May 13, 2022 USD ($)	Mar. 11, 2022 USD ($)
Short-term Debt [Line Items]
Letters of credit outstanding					$ 3,100,000
Short-term debt					244,500,000	$ 261,900,000
PNMR Development
Short-term Debt [Line Items]
Notes payable					0	0
ETBC 1 | Forecast
Short-term Debt [Line Items]
Scheduled payments			$ 3,400,000	$ 2,500,000
PNMR Revolving Credit Facility | WEB LOC Facility
Short-term Debt [Line Items]
Letters of credit outstanding					30,300,000
PNM
Short-term Debt [Line Items]
Letters of credit outstanding					0
Short-term debt					186,200,000	137,500,000
PNM | PNMR
Short-term Debt [Line Items]
Notes payable					2,300,000
PNM | Lines of credit
Short-term Debt [Line Items]
NMPRC approved credit facility							$ 40,000,000
TNMP
Short-term Debt [Line Items]
Letters of credit outstanding					0
Short-term debt					18,300,000	55,100,000
TNMP | PNMR
Short-term Debt [Line Items]
Notes payable					0
TNMP | TNMP 2024 Bond Purchase Agreement | Subsequent event | Unsecured Debt
Short-term Debt [Line Items]
Proceeds from issuance of unsecured debt	$ 128,000,000
PNMR Development | PNMR
Short-term Debt [Line Items]
Short-term debt					100,000	2,300,000
PNMR Development | PNMR Revolving Credit Facility
Short-term Debt [Line Items]
Short-term debt					40,000,000	$ 69,300,000
Revolving credit facility
Short-term Debt [Line Items]
Financing capacity					300,000,000
Revolving credit facility | PNM
Short-term Debt [Line Items]
Financing capacity					400,000,000
Revolving credit facility | TNMP
Short-term Debt [Line Items]
Financing capacity									$ 100,000,000
Revolving credit facility | TNMP | Subsequent event
Short-term Debt [Line Items]
Financing capacity		$ 200,000,000
Number of extensions | extension_option		2
Extension period		1 year
Revolving credit facility | TNMP | First mortgage bonds
Short-term Debt [Line Items]
Collateral amount								$ 100,000,000
Revolving credit facility | TNMP | First Mortgage Bonds Due 2029 | Subsequent event
Short-term Debt [Line Items]
Collateral amount		$ 200,000,000
Revolving credit facility | PNMR and PNM | Subsequent event
Short-term Debt [Line Items]
Number of extensions | extension_option		2
Extension period		1 year
Senior Unsecured Noted, Pollution Control Revenue Bonds | PNM | Pollution Control Revenue Bonds, Due June 2024
Short-term Debt [Line Items]
Financing capacity					198,000,000
Senior Unsecured Noted, Pollution Control Revenue Bonds | TNMP | FMB Notes Due July 2024
Short-term Debt [Line Items]
Financing capacity					$ 80,000,000