Summary of the Business and Significant Accounting Policies - Inventories/Depreciation and Amortization (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Public Utilities, Inventory [Line Items]
Inventory	$ 98,034	$ 66,733
Fuel Oil
Public Utilities, Inventory [Line Items]
Inventory	896	985
Materials and supplies
Public Utilities, Inventory [Line Items]
Inventory	97,138	65,748
PNM
Public Utilities, Inventory [Line Items]
Depreciation	158,956	163,162	$ 153,165
Inventory	81,572	55,890
PNM | Fuel Oil
Public Utilities, Inventory [Line Items]
Inventory	896	985
PNM | Materials and supplies
Public Utilities, Inventory [Line Items]
Inventory	$ 80,676	$ 54,905
PNM | Electric plant
Public Utilities, Inventory [Line Items]
Depreciation average rates used	2.67%	2.55%	2.48%
PNM | Common, intangible, and general plant
Public Utilities, Inventory [Line Items]
Depreciation average rates used	7.64%	7.83%	7.91%
TNMP
Public Utilities, Inventory [Line Items]
Depreciation average rates used	3.77%	3.72%	3.88%
Depreciation	$ 110,675	$ 96,131	$ 87,900
Inventory	16,462	10,843
TNMP | Fuel Oil
Public Utilities, Inventory [Line Items]
Inventory	0	0
TNMP | Materials and supplies
Public Utilities, Inventory [Line Items]
Inventory	$ 16,462	$ 10,843