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Related Party Transactions (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Related Party Transaction [Line Items]
Ownership percentage	50.00%		50.00%
Services billings: \| PNMR to PNM
Related Party Transaction [Line Items]
Amount of related party transaction	$ 24,204	$ 22,853	$ 70,848	$ 72,604
Services billings: \| PNMR to TNMP
Related Party Transaction [Line Items]
Amount of related party transaction	9,645	8,639	28,075	27,082
Services billings: \| PNM to TNMP
Related Party Transaction [Line Items]
Amount of related party transaction	106	97	295	286
Services billings: \| TNMP to PNMR
Related Party Transaction [Line Items]
Amount of related party transaction	35	35	106	106
Services billings: \| PNMR to NMRD
Related Party Transaction [Line Items]
Amount of related party transaction	74	68	199	163
Renewable energy purchases: \| PNM from NMRD
Related Party Transaction [Line Items]
Amount of related party transaction	3,723	757	7,646	2,331
Interconnection billings: \| PNM from NMRD
Related Party Transaction [Line Items]
Amount of related party transaction	0	0	350	0
Interconnection billings: \| PNM to PNMR
Related Party Transaction [Line Items]
Amount of related party transaction	0	0	0	0
Interest billings: \| PNMR to PNM
Related Party Transaction [Line Items]
Amount of related party transaction	0	1,004	6	2,909
Interest billings: \| PNMR to TNMP
Related Party Transaction [Line Items]
Amount of related party transaction	0	0	2	42
Interest billings: \| PNM to PNMR
Related Party Transaction [Line Items]
Amount of related party transaction	60	75	218	224
Income tax sharing payments: \| PNMR to PNM
Related Party Transaction [Line Items]
Amount of related party transaction	0	0	0	0
Income tax sharing payments: \| TNMP to PNMR
Related Party Transaction [Line Items]
Amount of related party transaction	$ 0	$ 0	$ 0	$ 0