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Commitments and Contingencies - The Clean Air Act (Details) $ in Millions |  |  | 9 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Oct. 01, 2014 USD ($) $ / kw MW | Dec. 20, 2013 USD ($) $ / kw MW | Sep. 30, 2015 T / yr state $ / kw MW | Aug. 13, 2015 MW | May. 19, 2015 MW | Jul. 31, 2014 MW | Jun. 26, 2014 MW | Oct. 31, 2012 USD ($)
Clean Air Act related to Regional Haze [Member] |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |
Public utilities, number of states to address regional haze (in states) | state |  |  | 50 |  |  |  |  |
Public utilities, potential to emit tons per year of visibility impairing pollution, maximum (in tons per year) | T / yr |  |  | 250 |  |  |  |  |
San Juan Generating Station [Member] | Public Service Company of New Mexico [Member] |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |
Jointly owned utility plant, proportionate ownership share |  |  |  |  |  |  |  | 46.30%
San Juan Generating Station [Member] | Public Service Company of New Mexico [Member] | Clean Air Act, SNCR [Member] |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |
Public utilities, overall reduction of ownership (in megawatts) |  | 340 |  |  |  |  |  |
San Juan Generating Station [Member] | Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] | Minimum [Member] | Public Service Company of New Mexico [Member] | Clean Air Act, SCR [Member] [Member] |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |
Estimated total capital cost if requirement occurred | $ |  |  |  |  |  |  |  | $ 824.0
San Juan Generating Station [Member] | Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] | Minimum [Member] | Public Service Company of New Mexico [Member] | Clean Air Act, SNCR [Member] |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |
Estimated installation capital costs | $ |  |  |  |  |  |  |  | 85.0
Estimated portion of total capital costs if requirement occurred | $ |  |  |  |  |  |  |  | 105.0
San Juan Generating Station [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, SCR [Member] [Member] |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |
Estimated total capital cost if requirement occurred | $ |  |  |  |  |  |  |  | 910.0
San Juan Generating Station [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 | $ |  |  |  |  |  |  |  | 90.0
Estimated portion of total capital costs if requirement occurred | $ |  |  |  |  |  |  |  | $ 110.0
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, requested time period to recover retired units NBV | 20 years | 20 years | 20 years |  |  |  |  |
Public utilities, newly identified replacement gas-fired generation, December 2013 (in megawatts) |  | 177 |  |  |  |  |  |
Public utilities, newly identified replacement solar generation, December 2013 (in megawatts) |  | 40 |  |  |  |  |  |
Public utilities, newly identified replacement gas-fired generation (in megawatts) |  |  | 187 |  |  |  |  |
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, 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) |  |  | 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) | 134 | 134 |  | 134 |  |  |  |
Public utilities, proposed value per kilowatt effective January 1, 2018 (in dollars per kilowatt) | $ / kw |  | 2,500 |  |  |  |  |  |
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 | $ | $ 90.6 | $ 82.0 |  |  |  |  |  |
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) | 132 | 78 | 132 | 65 | 132 | 132 | 132 |
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, ownership to be exchanged (in megawatts) |  | 78 |  |  |  |  |  |

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