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Electric Operating Revenues - Narrative (Details) $ in Thousands | 3 Months Ended |  |  |
--- | --- | --- | --- | ---
Mar. 31, 2017 USD ($) | Mar. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Dec. 16, 2015 MW
PNM |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Alternative revenue programs | $ 1,100 |  |  |
Other electric operating revenue | 28,400 |  |  |
TNMP |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Alternative revenue programs | 3,500 |  |  |
Other electric operating revenue | $ 0 |  |  |
Customer contracts | PNM |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Accounts receivable |  | $ 58,700 | $ 62,900 |
Clean Air Act, SNCR | Palo Verde Nuclear Generating Station Unit 3 | PNM |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Number of megawatts nuclear generation (in megawatts) | MW |  |  |  | 134

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