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Commitments and Contingencies - Stipulation Filed with the NMPRC (Details) |  |  |  | 9 Months Ended |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Apr. 08, 2015 USD ($) MW | Oct. 01, 2014 USD ($) $ / kw MW | Dec. 20, 2013 USD ($) $ / kw MW | Sep. 30, 2015 USD ($) $ / kw MW | Aug. 13, 2015 USD ($) MWh MW | Jul. 31, 2015 MW | May. 19, 2015 MW | Jan. 15, 2015 MW | Jul. 31, 2014 MW | Jun. 26, 2014 MW
Public Service Company of New Mexico [Member] | Clean Air Act, SNCR [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Public Utilities, Estimated costs to remain unrecovered |  |  |  | $ 20,000,000 |  |  |  |  |  |
San Juan Generating Station Unit 4 [Member] | Public Service Company of New Mexico [Member] | Clean Air Act, SNCR [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Public utilities, additional ownership to be obtained (in megawatts) | MW |  | 132 | 78 | 132 | 65 |  | 132 |  | 132 | 132
Public Utilities, Estimated rate base value at 1/1/2018 |  | $ 26,000,000 |  |  | $ 0 |  |  |  |  |
Public utilities, ownership PNM has agreed not to obtain (in megawatts) | MW |  |  |  |  |  |  |  | 65 |  |
coal-fired generation in Megawatts | MW |  |  |  |  | 197 |  |  |  |  |
Public Utilities, Number of Megawatt-hours of Renewable Energy Certificates to be acquired and retired beginning Jan 2020 | MWh |  |  |  |  | 1 |  |  |  |  |
San Juan Generating Station Unit 4 [Member] | Public Service Company of New Mexico [Member] | Clean Air Act, SNCR Hearing Examiner Recommended Denial [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Public utilities, additional ownership to be obtained (in megawatts) | MW | 132 |  |  |  | 132 | 132 |  |  |  |
San Juan Generating Station Unit 4 [Member] | Maximum [Member] | Public Service Company of New Mexico [Member] | Clean Air Act, SNCR [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Public Utilities, Annual cost of Renewable Energy Credits |  |  |  |  | $ 7,000,000 |  |  |  |  |
San Juan Generating Station Unit 3 [Member] | Public Service Company of New Mexico [Member] | Clean Air Act, SNCR [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Public utilities, proposed reduction in carrying value |  | 26,000,000 |  |  |  |  |  |  |  |
Public utilities, estimated unrecoverable increase in operations and maintenance |  | 20,000,000 |  |  |  |  |  |  |  |
San Juan Generating Station Unit 3 [Member] | Maximum [Member] | Public Service Company of New Mexico [Member] | Clean Air Act, SNCR [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Public utilities, estimated pre-tax regulatory disallowance | $ 155,000,000 | 70,000,000 |  | $ 155,000,000 |  |  |  |  |  |
San Juan Generating Station Unit 3 [Member] | Minimum [Member] | Public Service Company of New Mexico [Member] | Clean Air Act, SNCR [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Public utilities, estimated pre-tax regulatory disallowance | 145,000,000 | $ 60,000,000 |  | 145,000,000 |  |  |  |  |  |
San Juan Generating Station Units 2 and 3 [Member] | Public Service Company of New Mexico [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Net book value |  |  |  | $ 279,000,000 |  |  |  |  |  |
San Juan Generating Station Units 2 and 3 [Member] | Public Service Company of New Mexico [Member] | Clean Air Act, SNCR [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Public Utilities, Current ownership interest, in Megawatts | MW |  |  |  | 418 |  |  |  |  |  |
Public utilities, recovery percentage of estimated undepreciated value at 12/31/17 |  | 50.00% |  | 50.00% |  |  |  |  |  |
Public Utilities, Recoverable portion, Estimated undepreciated value at 12/31/17 |  |  |  | $ 128,500,000 |  |  |  |  |  |
Public utilities, estimated undepreciated value at 12/31/17 | $ 128,500,000 | $ 231,000,000 |  | $ 257,000,000 |  |  |  |  |  |
Public utilities, requested time period to recover retired units NBV |  | 20 years | 20 years | 20 years |  |  |  |  |  |
Public utilities, write-off percentage of estimated undepreciated value at 12/31/17 | 50.00% | 50.00% |  |  |  |  |  |  |  |
Palo Verde Nuclear Generating Station Unit 3 [Member] | Public Service Company of New Mexico [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Net book value |  |  |  | $ 147,000,000 |  |  |  |  |  |
Palo Verde Nuclear Generating Station Unit 3 [Member] | Public Service Company of New Mexico [Member] | Clean Air Act, SNCR [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Public Utilities, Estimated rate base value at 1/1/2018 |  | $ 221,100,000 |  |  |  |  |  |  |  |
Public utilities, estimated undepreciated value at 12/31/17 |  |  |  | $ 150,000,000 |  |  |  |  |  |
Public utilities, proposed value per kilowatt effective January 1, 2018 (in dollars per kilowatt) | $ / kw |  | 1,650 |  | 1,118 |  |  |  |  |  |
Palo Verde Nuclear Generating Station Unit 3 [Member] | PNMR and PNM [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Public utilities, number of megawatts nuclear generation (in megawatts) | MW |  |  |  | 134 |  |  |  |  |  |
Palo Verde Nuclear Generating Station Unit 3 [Member] | PNMR and PNM [Member] | Clean Air Act, SNCR [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Public utilities, number of megawatts nuclear generation (in megawatts) | MW |  | 134 | 134 |  | 134 |  |  |  |  |
Public utilities, proposed value per kilowatt effective January 1, 2018 (in dollars per kilowatt) | $ / kw |  |  | 2,500 |  |  |  |  |  |  |
Public utilities, percentage capacity factor 7-year performance threshold |  | 75.00% |  |  |  |  |  |  |  |
Public utilities, period over which to measure capacity performance |  | 7 years |  |  |  |  |  |  |  |
San Juan Generating Station Units 1 and 4 [Member] | Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] | Maximum [Member] | Public Service Company of New Mexico [Member] | Clean Air Act, SNCR [Member] |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Estimated installation capital costs |  | $ 90,600,000 | $ 82,000,000 |  |  |  |  |  |  |

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