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Commitments and Contingencies (Commitments and Contingencies Related to the Environment) (Details) (USD $) |  |  |  |  |  | 12 Months Ended |  |  |  |  |  |  |  |  | 0 Months Ended |  |  |  | 6 Months Ended |  |  |  |  |  | 6 Months Ended |  |  |
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Dec. 21, 2011 mw | Dec. 21, 2011 San Juan Generating Station [Member] | Oct. 31, 2012 Public Service Company of New Mexico [Member] San Juan Generating Station [Member] | Jun. 30, 2014 Public Service Company of New Mexico [Member] San Juan Generating Station Units 2 and 3 [Member] | Jun. 26, 2014 Public Service Company of New Mexico [Member] San Juan Generating Station Units 1 and 4 [Member] | Dec. 20, 2013 Public Service Company of New Mexico [Member] San Juan Generating Station Units 1 and 4 [Member] | Dec. 31, 2013 Public Service Company of New Mexico [Member] Nuclear Spent Fuel And Waste Disposal [Member] Palo Verde Nuclear Generating Station [Member] | Jun. 30, 2014 Public Service Company of New Mexico [Member] Nuclear Spent Fuel And Waste Disposal [Member] Palo Verde Nuclear Generating Station [Member] | Jun. 30, 2014 PNM Electric [Member] San Juan Generating Station Units 2 and 3 [Member] | Jun. 30, 2014 PNMR and PNM [Member] Palo Verde Nuclear Generating Station Unit 3 [Member] MW | Jun. 30, 2014 Other Deferred Credits [Member] Public Service Company of New Mexico [Member] Nuclear Spent Fuel And Waste Disposal [Member] Palo Verde Nuclear Generating Station [Member] | Dec. 31, 2013 Other Deferred Credits [Member] Public Service Company of New Mexico [Member] Nuclear Spent Fuel And Waste Disposal [Member] Palo Verde Nuclear Generating Station [Member] | Jun. 30, 2014 Clean Air Act related to Regional Haze [Member] state | Jun. 30, 2014 Clean Air Act Related to Post Combustion Controls [Member] Public Service Company of New Mexico [Member] Four Corners [Member] | Aug. 06, 2012 Clean Air Act Related to Post Combustion Controls [Member] Public Service Company of New Mexico [Member] Four Corners [Member] compliance_alternative | Jun. 30, 2014 Clean Air Act Related to Post Combustion Controls [Member] Public Service Company of New Mexico [Member] Four Corners Units 4 and 5 (Coal) [Member] | Dec. 20, 2013 Clean Air Act, SNCR [Member] Public Service Company of New Mexico [Member] San Juan Generating Station [Member] MW | Jun. 30, 2014 Clean Air Act, SNCR [Member] Public Service Company of New Mexico [Member] San Juan Generating Station Unit 3 [Member] | Dec. 20, 2013 Clean Air Act, SNCR [Member] Public Service Company of New Mexico [Member] San Juan Generating Station Unit 3 [Member] MW | Dec. 20, 2013 Clean Air Act, SNCR [Member] Public Service Company of New Mexico [Member] San Juan Generating Station Units 2 and 3 [Member] MW | Jun. 30, 2014 Clean Air Act, SNCR [Member] Public Service Company of New Mexico [Member] San Juan Generating Station Unit 4 [Member] | Jun. 26, 2014 Clean Air Act, SNCR [Member] Public Service Company of New Mexico [Member] San Juan Generating Station Unit 4 [Member] MW | Dec. 20, 2013 Clean Air Act, SNCR [Member] Public Service Company of New Mexico [Member] San Juan Generating Station Unit 4 [Member] MW | Dec. 20, 2013 Clean Air Act, SNCR [Member] PNMR and PNM [Member] Palo Verde Nuclear Generating Station Unit 3 [Member] MW | Jun. 30, 2014 Mercury Control [Member] Public Service Company of New Mexico [Member] San Juan Generating Station [Member] | Jun. 30, 2014 Environmental Protection Agency [Member] WildEarth Guardians filed an action to challenge EPA's rule in the Tenth Circuit [Member] San Juan Generating Station [Member] | Jun. 30, 2014 Environmental Protection Agency [Member] Clean Air Act Related to Post Combustion Controls [Member] Public Service Company of New Mexico [Member] Four Corners [Member] | Jun. 27, 2014 Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] Clean Air Act, SNCR [Member] Public Service Company of New Mexico [Member] San Juan Generating Station Unit 4 [Member] | Mar. 11, 2014 Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] Clean Air Act, SNCR [Member] Public Service Company of New Mexico [Member] San Juan Generating Station Unit 4 [Member] | Jan. 31, 2010 Minimum [Member] Public Service Company of New Mexico [Member] San Juan Generating Station And Four Corners [Member] opp | Oct. 31, 2012 Minimum [Member] Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] Clean Air Act, SCR [Member] [Member] Public Service Company of New Mexico [Member] San Juan Generating Station [Member] | Oct. 31, 2012 Minimum [Member] Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] Clean Air Act, SNCR [Member] Public Service Company of New Mexico [Member] San Juan Generating Station [Member] | Jan. 31, 2010 Maximum [Member] Public Service Company of New Mexico [Member] San Juan Generating Station And Four Corners [Member] opp | Jun. 30, 2014 Maximum [Member] Mercury Control [Member] Public Service Company of New Mexico [Member] San Juan Generating Station [Member] | Oct. 31, 2012 Maximum [Member] Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] Clean Air Act, SCR [Member] [Member] Public Service Company of New Mexico [Member] San Juan Generating Station [Member] | Oct. 31, 2012 Maximum [Member] Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] Clean Air Act, SNCR [Member] Public Service Company of New Mexico [Member] San Juan Generating Station [Member] | Dec. 20, 2013 Maximum [Member] Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] Clean Air Act, SNCR [Member] Public Service Company of New Mexico [Member] San Juan Generating Station Units 1 and 4 [Member] | Nov. 08, 2013 San Juan Generating Station [Member] National Ambient Air Quality Standards [Member] Public Service Company of New Mexico [Member]
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingency, Estimate of Possible Loss |  |  |  |  |  |  |  | $ 58,000,000 |  |  |  |  |  | $ 80,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingency Accrual |  |  |  |  |  |  |  |  |  |  | 12,100,000 | 11,900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Annual Fee, Nuclear Waste Disposal |  |  |  |  |  |  | 3,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revised Annual Fee, Nuclear Waste Disposal |  |  |  |  |  |  | 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Number of States To Address Regional Haze |  |  |  |  |  |  |  |  |  |  |  |  | 50 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Potential to emit tons per year of visibility impairing pollution, maximum |  |  |  |  |  |  |  |  |  |  |  |  | 250 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Proposed Seeking Shorter Compliance Period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5 years |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Number of years after issuance of final determination to achieve compliance with requirements |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 years |  |  |  |  |  |  |  |  |  |  |
Estimated Total Capital Cost If Requirement Occurred |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 824,000,000 |  |  |  | 910,000,000 |  |  |
Estimated Installation Capital Costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 85,000,000 |  |  |  | 90,000,000 | 82,000,000 |
Estimated Portion of Total Capital Costs if Requirement Occured |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 105,000,000 |  |  |  | 110,000,000 |  |
Jointly Owned Utility Plant, Proportionate Ownership Share |  |  | 46.30% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net book value |  |  |  | 286,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Requested Time Period to Recover Retired Units NBV |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 20 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Expected NBV of Units at Retirement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 205,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Number of Megawatts Nuclear Generation |  |  |  |  |  |  |  |  |  | 134 |  |  |  |  |  |  |  |  |  |  |  |  |  | 134 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Proposed value per Kilowatt effective January 1, 2018 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2,500 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Additional Ownership To Be Obtained, in Megawatts |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 132 | 78 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Costs to obtain additional ownership |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Overall Reduction Of Ownership, in Megawatts |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 340 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Ownership To Be Exchanged, in Megawatts |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 78 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Jointly Owned Utility Plan, Proposed Proportionate Ownership Share |  |  |  |  | 59.00% | 52.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Newly Identified Replacement Gas-fired Generation, in Megawatts, December2013 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 177 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Newly Identified Replacement Solar Generation, in Megawatts, December2013 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 40 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
estimated cost of replacing gas fired peaking capacity due to retirement of SJGS units |  |  |  |  |  |  |  |  | 268,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of ownership held by exiting owners |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50.00% |  |  | 38.80% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Ownership Percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 13.00% |  | 50.00% |  |  | 38.50% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Requested Expenditure, Installation Capital Costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,900,000 |  |  |  |  |  |  |  |  |
Requested Additional Expenditure, Installation Capital Costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 6,400,000 |  |  |  |  |  |  |  |  |  |
Public Utilities, Number of Compliance alternatives |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Plant Requirement to Meet NOx emissions Limit |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.015 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Plant Requirement to Meet Opacity Limit, Percentage |  |  |  |  |  |  |  |  |  |  |  |  |  | 20.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Rule Imposes Opacity Limitation on Certain Fugitive Dust Emissions From Coal and Material Handling Operations |  |  |  |  |  |  |  |  |  |  |  |  |  | 20.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Revised SO2 Emissions Agreed Upon |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.1
Public Utilities, Government Standard Emission Limit |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.060 |  |  | 0.070 |  |  |  |  |
Current Annual Mercury Control Costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 700,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Contingent Estimated Annual Mercury Control Cost |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 6,600,000 |  |  |  |
Minimum Megawatt Capacity from Coal and Oil-Fired Electric Generating Units under Jurisdiction of the Mercury and Air Toxics Standards | 25 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mercury Removal Rate, Percentage |  | 99.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

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- Definition The proportionate share of interest (percent) in a jointly owned utility plant. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 10.C) -URI http://asc.fasb.org/extlink&oid=6500719&loc=d3e659983-123033 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 10 -Section C + Details
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