XML 73 R53.htm IDEA: XBRL DOCUMENT
v3.5.0.2

Commitments and Contingencies - The Clean Air Act (Details) |  |  |  | 3 Months Ended | 6 Months Ended | 12 Months Ended | 40 Months Ended |  |  |  |  |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Feb. 25, 2016 | Dec. 16, 2015 USD ($) MWh MW | Mar. 02, 2015 lb / MMBTU T | Jun. 30, 2016 USD ($) MW | Mar. 31, 2016 USD ($) | Jun. 30, 2015 USD ($) | Jun. 30, 2016 USD ($) MW | Jun. 30, 2015 USD ($) | Dec. 31, 2015 USD ($) | Jun. 30, 2016 USD ($) MW | Feb. 09, 2016 | Jan. 26, 2016 state | Oct. 01, 2015 parts_per_billion | Sep. 30, 2015 parts_per_billion | Jul. 31, 2015 MW | Dec. 30, 2013 lbsofnox / mmbtu | Aug. 06, 2012 compliance_alternative | Jan. 31, 2010 parts_per_billion | Jul. 31, 2005 T | Dec. 31, 1999 state
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory disallowances and restructuring costs |  |  |  | $ 0 |  | $ 1,529,000 | $ 774,000 | $ 1,744,000 |  |  |  |  |  |  |  |  |  |  |  |
Plant in service, held for future use, and to be abandoned |  |  |  | 6,774,773,000 |  |  | 6,774,773,000 |  | $ 6,307,261,000 | $ 6,774,773,000 |  |  |  |  |  |  |  |  |  |
Accumulated depreciation and amortization |  |  |  | 2,279,853,000 |  |  | 2,279,853,000 |  | 2,058,772,000 | 2,279,853,000 |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory disallowances and restructuring costs |  |  |  | 0 |  | $ 1,529,000 | 774,000 | $ 1,744,000 |  |  |  |  |  |  |  |  |  |  |  |
Plant in service, held for future use, and to be abandoned |  |  |  | 5,258,713,000 |  |  | 5,258,713,000 |  | 4,833,303,000 | 5,258,713,000 |  |  |  |  |  |  |  |  |  |
Accumulated depreciation and amortization |  |  |  | 1,765,392,000 |  |  | 1,765,392,000 |  | 1,569,549,000 | 1,765,392,000 |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | San Juan Generating Station Units 2 and 3 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Plant in service, held for future use, and to be abandoned |  |  |  | 471,500,000 |  |  | 471,500,000 |  |  | 471,500,000 |  |  |  |  |  |  |  |  |  |
Accumulated depreciation and amortization |  |  |  | 199,300,000 |  |  | 199,300,000 |  |  | 199,300,000 |  |  |  |  |  |  |  |  |  |
Net book value |  |  |  | 272,200,000 |  |  | 272,200,000 |  |  | 272,200,000 |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | San Juan Generating Station [Member] | Loss on long-term purchase commitment [Member] | Surface [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory disallowances and restructuring costs |  |  |  |  |  |  |  |  | $ 16,500,000 |  |  |  |  |  |  |  |  |  |  |
Loss contingency, estimate of possible loss |  |  |  | $ 96,700,000 |  |  | $ 96,700,000 |  |  | $ 96,700,000 |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | San Juan Generating Station And Four Corners [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proposed government standard emission limit (in ozone parts per million) | parts_per_billion |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 70 |  |
Government standard emission limit (in ozone parts per million) | parts_per_billion |  |  |  |  |  |  |  |  |  |  |  |  | 70 | 75 |  |  |  |  |  |
Public Service Company of New Mexico [Member] | San Juan Generating Station And Four Corners [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proposed government standard emission limit (in ozone parts per million) | parts_per_billion |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 60 |  |
PNMR and PNM [Member] | Palo Verde Nuclear Generating Station Unit 3 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatts | MW |  |  |  | 134 |  |  | 134 |  |  | 134 |  |  |  |  |  |  |  |  |  |
Clean Air Act related to Regional Haze [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of states to address regional haze (in states) | state |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50
Potential to emit tons per year of visibility impairing pollution (in tons, more than) | T |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 250 |
Clean Air Act, SNCR [Member] | San Juan Generating Station Unit 4 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Number of other owner |  |  |  | 8 |  |  | 8 |  |  | 8 |  |  |  |  |  |  |  |  |  |
Clean Air Act, SNCR [Member] | Public Service Company of New Mexico [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated costs to remain unrecovered |  | $ 20,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Clean Air Act, SNCR [Member] | Public Service Company of New Mexico [Member] | San Juan Generating Station Units 1 and 4 [Member] | Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total costs for equipment |  |  |  |  |  |  |  |  |  | $ 76,800,000 |  |  |  |  |  |  |  |  |  |
Clean Air Act, SNCR [Member] | Public Service Company of New Mexico [Member] | San Juan Generating Station Units 2 and 3 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Current ownership interest (in megawatts) | MW |  | 418 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Time period to recover retired units' remaining net book value |  | 20 years |  |  |  |  |  |  | 20 years |  |  |  |  |  |  |  |  |  |  |
Recovery percentage of estimated undepreciated value at 12/31/17 |  | 50.00% |  | 50.00% |  |  | 50.00% |  | 50.00% | 50.00% |  |  |  |  |  |  |  |  |  |
Estimated undepreciated value at 12/31/17 |  |  |  |  |  |  |  |  | $ 255,300,000 |  |  |  |  |  |  |  |  |  |  |
Regulatory disallowances and restructuring costs |  |  |  |  |  |  |  |  | 127,600,000 |  |  |  |  |  |  |  |  |  |  |
Expense reflected in regulatory disallowances and restructuring costs |  |  |  |  | $ 800,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Accumulated plant write-off, disallowance |  |  |  | $ 128,200,000 |  |  | $ 128,200,000 |  |  | $ 128,200,000 |  |  |  |  |  |  |  |  |  |
Net carrying value of utility plant |  |  |  | 144,000,000 |  |  | 144,000,000 |  |  | 144,000,000 |  |  |  |  |  |  |  |  |  |
Clean Air Act, SNCR [Member] | Public Service Company of New Mexico [Member] | San Juan Generating Station Units 2 and 3 [Member] | Increase in coal mine decommissioning liability [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory disallowances and restructuring costs |  |  |  |  |  |  |  |  | $ 165,700,000 |  |  |  |  |  |  |  |  |  |  |
Clean Air Act, SNCR [Member] | Public Service Company of New Mexico [Member] | San Juan Generating Station Unit 4 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Additional ownership to be obtained (in megawatts) | MW |  | 65 |  |  |  |  |  |  |  |  |  |  |  |  | 132 |  |  |  |  |
Estimated rate base value |  | $ 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Coal-fired generation (in megawatts) | MW |  | 197 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatt hours of Renewable Energy Certificates to be acquired and retired (in megawatt hours) | MWh |  | 1 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Clean Air Act, SNCR [Member] | Public Service Company of New Mexico [Member] | San Juan Generating Station Unit 4 [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Annual cost of Renewable Energy Credits |  | $ 7,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Clean Air Act, SNCR [Member] | Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station Unit 3 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated undepreciated value at 12/31/17 |  | $ 150,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Clean Air Act, SNCR [Member] | PNMR and PNM [Member] | Palo Verde Nuclear Generating Station Unit 3 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatts | MW |  | 134 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Clean Air Act, SNCR [Member] | PNMR Development [Member] | San Juan Generating Station Unit 4 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Expense for cost, obligation to reimburse |  |  |  |  | $ 600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Potential acquisition of ownership (in megawatts) | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 65 |  |  |  |  |
Clean Air Act, SNCR Hearing Examiner Recommended Denial [Member] | Public Service Company of New Mexico [Member] | San Juan Generating Station Unit 4 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Additional ownership to be obtained (in megawatts) | MW |  | 132 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Clean Air Act, Post-2022 Coal Supply future rate case [Member] | Public Service Company of New Mexico [Member] | San Juan Generating Station Unit 4 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Period of time agreed to by all parties to settle rate case |  | 6 months |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Clean Air Act Related to Post Combustion Controls [Member] | Public Service Company of New Mexico [Member] | Four Corners [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of compliance alternatives | compliance_alternative |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |
Plant requirement to meet NOx emissions limit (in pounds of NOx per MMBTU) | lbsofnox / mmbtu |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.015 |  |  |  |
Plant requirement to meet opacity limit |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 20.00% |  |  |  |
Rule imposes opacity limitation on certain fugitive dust emissions from coal and material handling operations |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 20.00% |  |  |  |
Loss contingency, estimate of possible loss |  |  |  | $ 91,100,000 |  |  | $ 91,100,000 |  |  | $ 91,100,000 |  |  |  |  |  |  |  |  |  |
Clean Air Act Related to Post Combustion Controls [Member] | Public Service Company of New Mexico [Member] | Four Corners Units 4 and 5 (Coal) [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 13.00% |  |  |  |
Clean Power Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Period of potential extension to meet environmental targets |  |  |  |  |  |  | 2 years |  |  |  |  |  |  |  |  |  |  |  |  |
Number of states that filed a petition against the Clean Power Plan | state |  |  |  |  |  |  |  |  |  |  |  | 29 |  |  |  |  |  |  |  |
Proposed percentage reduction in CO2 emissions, stayed by the USSC |  |  |  |  |  |  |  |  |  |  | 32.00% |  |  |  |  |  |  |  |  |
Period of time currently remaining to submit initial plans to meet environmental targets |  |  |  |  |  |  | 6 months |  |  |  |  |  |  |  |  |  |  |  |  |
Period of time currently remaining to submit initial plans to meet environmental targets, including potential extension |  |  |  |  |  |  | 2 years 6 months |  |  |  |  |  |  |  |  |  |  |  |  |
National Ambient Air Quality Standards, 2015 EPA Legal Settlement [Member] | Public Service Company of New Mexico [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Period of time to act on settlement |  |  | 16 months |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Emissions tons of SO2 per year (more than) | T |  |  | 16,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
National Ambient Air Quality Standards, 2015 EPA Legal Settlement [Member] | Public Service Company of New Mexico [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Emissions tons of SO2 per year (more than) | T |  |  | 2,600 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public utilities, 1-hour SO2 emissions rate (in pounds per MMBTU) | lb / MMBTU |  |  | 0.45 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
National Ambient Air Quality Standards, 2015 EPA Legal Settlement [Member] [Member] | Public Service Company of New Mexico [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Period of time from state designation, to provide implementation plans | 36 months |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

X
- Definition coal-fired generation in Megawatts + References No definition available. + Details
Name: | pnm_CoalfiredgenerationinMegawatts
Namespace Prefix: | pnm_
Data Type: | num:powerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Installation Capital Costs + References No definition available. + Details
Name: | pnm_InstallationCapitalCosts
Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Net book value + References No definition available. + Details
Name: | pnm_NetBookValue
Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Number of states that filed a petition against the Clean Power Plan + References No definition available. + Details
Name: | pnm_NumberofstatesthatfiledapetitionagainsttheCleanPowerPlan
Namespace Prefix: | pnm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Period of potential extension to submit initial plans to meet environmental targets + References No definition available. + Details
Name: | pnm_Periodofpotentialextensiontosubmitinitialplanstomeetenvironmentaltargets
Namespace Prefix: | pnm_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period of time currently remaining to submit initial plans to meet environmental targets + References No definition available. + Details
Name: | pnm_Periodoftimecurrentlyremainingtosubmitinitialplanstomeetenvironmentaltargets
Namespace Prefix: | pnm_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period of time currently remaining to submit initial plans to meet environmental targets, including potential extension + References No definition available. + Details
Name: | pnm_Periodoftimecurrentlyremainingtosubmitinitialplanstomeetenvironmentaltargetsincludingpotentialextension
Namespace Prefix: | pnm_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period of time from state designation, to provide implementation plans + References No definition available. + Details
Name: | pnm_Periodoftimefromstatedesignationtoprovideimplementationplans
Namespace Prefix: | pnm_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period of time to act on settlement + References No definition available. + Details
Name: | pnm_Periodoftimetoactonsettlement
Namespace Prefix: | pnm_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Public Utilities, 1-hour SO2 Emissions Rate + References No definition available. + Details
Name: | pnm_PublicUtilities1hourSO2EmissionsRate
Namespace Prefix: | pnm_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Accumulated plant write-off, disallowance + References No definition available. + Details
Name: | pnm_PublicUtilitiesAccumulatedplantwriteoffdisallowance
Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Public Utilities, Additional Ownership To Be Obtained, in Megawatts + References No definition available. + Details
Name: | pnm_PublicUtilitiesAdditionalOwnershipToBeObtainedinMegawatts
Namespace Prefix: | pnm_
Data Type: | num:powerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Annual cost of Renewable Energy Credits + References No definition available. + Details
Name: | pnm_PublicUtilitiesAnnualcostofRenewableEnergyCredits
Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Public Utilities, Commitments And Contingencies [Line Items] + References No definition available. + Details
Name: | pnm_PublicUtilitiesCommitmentsAndContingenciesLineItems
Namespace Prefix: | pnm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Public Utilities, Current ownership interest, in Megawatts + References No definition available. + Details
Name: | pnm_PublicUtilitiesCurrentownershipinterestinMegawatts
Namespace Prefix: | pnm_
Data Type: | num:powerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Emissions Tons of SO2 per year + References No definition available. + Details
Name: | pnm_PublicUtilitiesEmissionsTonsofSO2peryear
Namespace Prefix: | pnm_
Data Type: | num:massItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Estimated costs to remain unrecovered + References No definition available. + Details
Name: | pnm_PublicUtilitiesEstimatedcoststoremainunrecovered
Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Public Utilities, Estimated rate base value at 1/1/2018 + References No definition available. + Details
Name: | pnm_PublicUtilitiesEstimatedratebasevalueat112018
Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Public Utilities, Estimated undepreciated value at 12/31/17 + References No definition available. + Details
Name: | pnm_PublicUtilitiesEstimatedundepreciatedvalueat123117
Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Public Utilities, Government Standard Emission Limit + References No definition available. + Details
Name: | pnm_PublicUtilitiesGovernmentStandardEmissionLimit
Namespace Prefix: | pnm_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Net Carrying Value of Utility Plant + References No definition available. + Details
Name: | pnm_PublicUtilitiesNetCarryingValueofUtilityPlant
Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Public Utilities, Number of Compliance alternatives + References No definition available. + Details
Name: | pnm_PublicUtilitiesNumberOfComplianceAlternatives
Namespace Prefix: | pnm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Number of States To Address Regional Haze + References No definition available. + Details
Name: | pnm_PublicUtilitiesNumberOfStatesToAddressRegionalHaze
Namespace Prefix: | pnm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Number of Megawatt-hours of Renewable Energy Certificates to be acquired and retired beginning Jan 2020 + References No definition available. + Details
Name: | pnm_PublicUtilitiesNumberofMegawatthoursofRenewableEnergyCertificatestobeacquiredandretiredbeginningJan2020
Namespace Prefix: | pnm_
Data Type: | num:energyItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Number of Megawatts Nuclear Generation + References No definition available. + Details
Name: | pnm_PublicUtilitiesNumberofMegawattsNuclearGeneration
Namespace Prefix: | pnm_
Data Type: | num:powerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Number of other owner + References No definition available. + Details
Name: | pnm_PublicUtilitiesNumberofotherowner
Namespace Prefix: | pnm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Ownership Percentage + References No definition available. + Details
Name: | pnm_PublicUtilitiesOwnershipPercentage
Namespace Prefix: | pnm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Period of time agreed to by all parties to settle rate case + References No definition available. + Details
Name: | pnm_PublicUtilitiesPeriodoftimeagreedtobyallpartiestosettleratecase
Namespace Prefix: | pnm_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Public Utilities, Plant Requirement to Meet NOx emissions Limit + References No definition available. + Details
Name: | pnm_PublicUtilitiesPlantRequirementtoMeetNOxemissionsLimit
Namespace Prefix: | pnm_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Plant Requirement to Meet Opacity Limit, Percentage + References No definition available. + Details
Name: | pnm_PublicUtilitiesPlantRequirementtoMeetOpacityLimitPercentage
Namespace Prefix: | pnm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Potential Acquisition of Ownership in Megawatts + References No definition available. + Details
Name: | pnm_PublicUtilitiesPotentialAcquisitionofOwnershipinMegawatts
Namespace Prefix: | pnm_
Data Type: | num:powerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Potential to emit tons per year of visibility impairing pollution, maximum + References No definition available. + Details
Name: | pnm_PublicUtilitiesPotentialtoemittonsperyearofvisibilityimpairingpollutionmaximum
Namespace Prefix: | pnm_
Data Type: | num:massItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Proposed Government Standard Emission Limit + References No definition available. + Details
Name: | pnm_PublicUtilitiesProposedGovernmentStandardEmissionLimit
Namespace Prefix: | pnm_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Proposed percentage reduction in CO2 emissions, Stayed by the USSC + References No definition available. + Details
Name: | pnm_PublicUtilitiesProposedpercentagereductioninCO2emissionsStayedbytheUSSC
Namespace Prefix: | pnm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Recovery Percentage of Estimated undepreciated value at 12/31/17 + References No definition available. + Details
Name: | pnm_PublicUtilitiesRecoveryPercentageofEstimatedundepreciatedvalueat123117
Namespace Prefix: | pnm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Rule Imposes Opacity Limitation on Certain Fugitive Dust Emissions From Coal and Material Handling Operations + References No definition available. + Details
Name: | pnm_PublicUtilitiesRuleImposesOpacityLimitationOnCertainFugitiveDustEmissionsFromCoalAndMaterialHandlingOperations
Namespace Prefix: | pnm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Time Period to Recover Retired Units remaining NBV + References No definition available. + Details
Name: | pnm_PublicUtilitiesTimePeriodtoRecoverRetiredUnitsremainingNBV
Namespace Prefix: | pnm_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Regulatory Disallowance + References No definition available. + Details
Name: | pnm_RegulatoryDisallowance
Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Regulatory Disallowance, Additional amount recorded + References No definition available. + Details
Name: | pnm_RegulatoryDisallowanceAdditionalamountrecorded
Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Reflects the estimated amount of loss from the specified contingency as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 9 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349 + Details
Name: | us-gaap_LossContingencyEstimateOfPossibleLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of other expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses associated with a discontinued operation or an asset retirement obligation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB Topic 5.P.4(b)) -URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 5.P.3) -URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140864-122747 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869 + Details
Name: | us-gaap_OtherRestructuringCosts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Period end book value of accumulated depreciation on property, plant and equipment (PPE) that is owned by the regulated operations of the public utility. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Period end amount of total gross PPE. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesPropertyPlantAndEquipmentPlantInService
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | dei_LegalEntityAxis=pnm_PublicServiceCompanyOfNewMexicoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_JointlyOwnedUtilityPlantAxis=pnm_SanJuanGeneratingStationUnits2And3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_JointlyOwnedUtilityPlantAxis=pnm_SanJuanGeneratingStationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LossContingenciesByNatureOfContingencyAxis=us-gaap_LossOnLongTermPurchaseCommitmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_ClassificationOfMineAxis=pnm_SurfaceMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_JointlyOwnedUtilityPlantAxis=pnm_SanJuanGeneratingStationAndFourCornersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=pnm_PnmrAndPnmMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_JointlyOwnedUtilityPlantAxis=pnm_PaloVerdeNuclearGeneratingStationUnit3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_CommitmentsAndContingenciesRelatedToEnvironmentAndOtherNatureAxis=pnm_CleanAirActRelatedToRegionalHazeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_CommitmentsAndContingenciesRelatedToEnvironmentAndOtherNatureAxis=pnm_CleanAirActSncrMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_JointlyOwnedUtilityPlantAxis=pnm_SanJuanGeneratingStationUnit4Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_JointlyOwnedUtilityPlantAxis=pnm_SanJuanGeneratingStationUnits1And4Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_PublicUtilitiesCommitmentsAndContingenciesByNatureOfExpenseAxis=pnm_InstallationCostsIncludingConstructionManagementGrossReceiptsTaxesAfudcAndOtherPnmCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LossContingenciesByNatureOfContingencyAxis=pnm_IncreaseincoalminedecommissioningliabilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=pnm_PNMRDevelopmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_CommitmentsAndContingenciesRelatedToEnvironmentAndOtherNatureAxis=pnm_CleanAirActSNCRHearingExaminerRecommendedDenialMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_CommitmentsAndContingenciesRelatedToEnvironmentAndOtherNatureAxis=pnm_CleanAirActPost2022CoalSupplyfutureratecaseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_CommitmentsAndContingenciesRelatedToEnvironmentAndOtherNatureAxis=pnm_CleanAirActRelatedToPostCombustionControlsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_JointlyOwnedUtilityPlantAxis=pnm_FourCornersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_JointlyOwnedUtilityPlantAxis=pnm_FourCornersUnits4And5CoalMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_CommitmentsAndContingenciesRelatedToEnvironmentAndOtherNatureAxis=pnm_CleanPowerPlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_CommitmentsAndContingenciesRelatedToEnvironmentAndOtherNatureAxis=pnm_NationalAmbientAirQualityStandards2015EPALegalSettlementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_CommitmentsAndContingenciesRelatedToEnvironmentAndOtherNatureAxis=pnm_NationalAmbientAirQualityStandardsProposed2016SO2RuleMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |