Variable Interest Entities (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) MW	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) MW	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Jan. 31, 2016 USD ($)
Results of Operations
Operating revenues	$ 357,649	$ 330,228	$ 691,271	$ 679,872
Operating expenses	286,499	423,843	572,383	736,764
Earnings attributable to non-controlling interest	3,940	3,499	7,669	6,328
Financial Position
Current assets	326,884		326,884		$ 294,010
Assets	7,574,467	7,048,667	7,574,467	7,048,667	7,298,774
Current liabilities	1,265,774		1,265,774		967,481
Owners’ equity – non-controlling interest	59,927		59,927		63,052
PNM
Results of Operations
Operating revenues	260,788	238,219	508,921	507,536
Operating expenses	211,204	354,196	425,733	599,221
Earnings attributable to non-controlling interest	3,940	3,499	7,669	6,328
Financial Position
Current assets	281,292		281,292		259,195
Assets	5,377,422		5,377,422		5,242,991
Current liabilities	447,508		447,508		593,236
Owners’ equity – non-controlling interest	59,927		59,927		63,052
PNM | Valencia
Variable Interest Entity [Line Items]
Payment for fixed costs	5,000	5,000	10,000	9,900
Payment for variable costs	500	200	$ 900	300
Long-term contract option to purchase, ownership percentage (up to)			50.00%
Long-term contract option to purchase, purchase price - percentage of adjusted NBV			50.00%
Long-term contract option to purchase, purchase price - percentage of FMV			50.00%
Results of Operations
Operating revenues	5,495	5,177	$ 10,848	10,129
Operating expenses	1,555	1,678	3,179	3,801
Earnings attributable to non-controlling interest	3,940	$ 3,499	7,669	$ 6,328
Financial Position
Current assets	3,393		3,393		5,094
Net property, plant, and equipment	57,163		57,163		58,581
Assets	60,556		60,556		63,675
Current liabilities	629		629		623
Owners’ equity – non-controlling interest	$ 59,927		$ 59,927		$ 63,052
PNM | Purchased through May 2028 | Valencia
Variable Interest Entity [Line Items]
Number of megawatts purchased (in megawatts) | MW	158		158
NM Capital | San Juan Generating Station | Coal supply
Variable Interest Entity [Line Items]
Cash used to support bank letter or credit arrangement	$ 30,300		$ 30,300			$ 30,300