Variable Interest Entities (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($) MW	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) MW	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	Jan. 31, 2016 USD ($)
Results of Operations
Operating revenues	$ 554,551	$ 472,465	$ 1,345,798	$ 1,163,736
Operating expenses	402,822	324,660	1,076,700	897,043
Earnings attributable to non-controlling interest	4,229	3,553	11,643	11,222
Financial Position
Current assets	447,713		447,713		$ 377,479
Assets	8,256,070	7,742,112	8,256,070	7,742,112	7,939,854
Current liabilities	475,207		475,207		977,662
Owners’ equity – non-controlling interest	56,414		56,414		59,009
PNM
Results of Operations
Operating revenues	435,523	364,504	1,030,685	873,425
Operating expenses	320,960	247,964	831,305	673,697
Earnings attributable to non-controlling interest	4,229	3,553	11,643	11,222
Financial Position
Current assets	377,284		377,284		322,128
Assets	5,723,176		5,723,176		5,581,033
Current liabilities	357,122		357,122		594,332
Owners’ equity – non-controlling interest	56,414		56,414		59,009
PNM | Valencia
Variable Interest Entity [Line Items]
Payment for fixed costs	5,000	5,000	14,900	15,000
Payment for variable costs	700	300	$ 1,600	1,200
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	5,719	5,278	$ 16,425	16,126
Operating expenses	1,490	1,725	4,782	4,904
Earnings attributable to non-controlling interest	4,229	$ 3,553	11,643	$ 11,222
Financial Position
Current assets	3,981		3,981		3,911
Net property, plant, and equipment	53,617		53,617		55,744
Assets	57,598		57,598		59,655
Current liabilities	1,184		1,184		646
Owners’ equity – non-controlling interest	$ 56,414		$ 56,414		$ 59,009
PNM | Purchased through May 2028 | Valencia
Variable Interest Entity [Line Items]
Number of megawatts purchased (in megawatts) | MW	155		155
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