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Regulatory and Rate Matters - New Mexico General Rate Cases (Details) $ in Thousands |  |  |  |  |  | 1 Months Ended | 12 Months Ended | 24 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Feb. 01, 2018 | Jan. 10, 2018 USD ($) | Dec. 07, 2016 USD ($) | Sep. 28, 2016 USD ($) lease MW | Aug. 27, 2015 USD ($) | Aug. 31, 2019 | Aug. 31, 2016 USD ($) lease MW | Dec. 31, 2019 USD ($) MW | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2018 USD ($) | May 16, 2019 MW | Dec. 31, 2016 MW | Sep. 30, 2016 MW | Jan. 31, 2016 MW
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income taxes (benefit) |  |  |  |  |  |  |  | $ (25,282) | $ 7,775 | $ 130,340 |  |  |  |  |
Regulatory disallowances and restructuring costs |  |  |  |  |  |  |  | 151,095 | $ 65,598 | 27,036 |  |  |  |  |
Percent of non-fuel revenue requirement change implemented | 50.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |
NMPRC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Requested rate increase (decrease) |  |  | $ 99,200 |  |  |  |  |  |  |  |  |  |  |  |
Requested return on equity |  |  | 10.125% |  |  |  |  |  |  |  |  |  |  |  |
Proposed term for providing benefits to customers related to reduction in state corporate tax |  |  |  |  |  |  |  |  | 23 years |  |  |  |  |  |
Public Service Company of New Mexico |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income taxes (benefit) |  |  |  |  |  |  |  | (25,962) | $ (5,971) | 81,555 |  |  |  |  |
Regulatory disallowances and restructuring costs |  |  |  |  |  |  |  | 150,599 | 66,339 | 27,036 |  |  |  |  |
Public Service Company of New Mexico | NMPRC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Requested rate increase (decrease) |  | $ 10,300 |  |  |  |  |  |  |  |  |  |  |  |  |
Requested return on equity |  | 9.575% |  |  |  |  |  |  |  |  |  |  |  |  |
Proposed term for providing benefits to customers related to reduction in state corporate tax |  | 3 years |  |  |  | 3 years |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico | Palo Verde Nuclear Generating Station, Unit 2 Leases |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatts purchased (in megawatts) | MW |  |  |  | 64.1 |  |  | 64.1 |  |  |  |  |  |  | 64.1 | 64.1
Number of megawatts (in megawatts) | MW |  |  |  | 114.6 |  |  | 114.6 |  |  |  |  |  |  | 114.6 |
Number of leases under which assets were purchased | lease |  |  |  | 3 |  |  | 3 |  |  |  |  |  |  |  |
Public Service Company of New Mexico | Palo Verde Nuclear Generating Station, Unit 1 Leases, extended |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated annual rent expense |  |  |  |  |  |  | $ 18,100 |  |  |  |  |  |  |  |
Public Service Company of New Mexico | 2015 Electric Rate Case |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Requested rate increase (decrease) |  |  |  |  | $ 123,500 |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease) |  |  |  | $ 61,200 |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico | 2015 Electric Rate Case | Palo Verde Nuclear Generating Station, Unit 2 Leases |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proposed disallowance of recovery of purchase price of assets |  |  |  |  |  |  | $ 163,300 |  |  |  |  |  |  |  |
Approved lease acquisition costs |  |  |  | 83,700 |  |  |  |  |  |  |  |  |  |  |
Disallowed leasehold improvements |  |  |  | $ 43,800 |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico | 2015 Electric Rate Case | Non-Fuel Energy |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Requested rate increase (decrease) |  |  |  |  | $ 121,700 |  |  |  |  |  |  |  |  |  |
Four Corners |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory disallowances and restructuring costs |  | $ 47,600 |  |  |  |  |  |  |  |  |  |  |  |  |
Pre-tax regulatory disallowance |  | $ 148,100 |  |  |  |  |  |  |  |  |  |  |  |  |
Palo Verde Nuclear Generating Station, Unit 2 | Public Service Company of New Mexico |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatts purchased (in megawatts) | MW |  |  |  |  |  |  | 64.1 |  |  |  |  |  |  |  |
Number of megawatts (in megawatts) | MW |  |  |  |  |  |  | 114.6 |  |  |  |  | 114.6 | 114.6 |  |
Palo Verde Nuclear Generating Station, Unit 2 | Public Service Company of New Mexico | 2015 Electric Rate Case |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatts purchased (in megawatts) | MW |  |  |  |  |  |  |  |  |  |  |  | 64.1 |  |  |
Pre-tax regulatory disallowance for capital costs |  |  |  |  |  |  |  |  | $ 4,000 | $ 3,100 | $ 18,400 |  |  |  |
New Mexico 2015 Rate Case | Public Service Company of New Mexico |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Recorded pre-tax impairments |  |  |  |  |  |  |  | 150,600 |  |  |  |  |  |  |
Amount of impairment to carrying amount of regulatory assets |  |  |  |  |  |  |  | 39,700 |  |  |  |  |  |  |
Income taxes (benefit) |  |  |  |  |  |  |  | $ 45,700 |  |  |  |  |  |  |
New Mexico 2015 Rate Case | Palo Verde Nuclear Generating Station, Unit 2 | Public Service Company of New Mexico |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatts purchased (in megawatts) | MW |  |  |  |  |  |  |  | 64.1 |  |  |  | 64.1 |  |  |
Recorded pre-tax impairments portion of purchase price |  |  |  |  |  |  |  | $ 73,200 |  |  |  |  |  |  |
Income taxes (benefit) |  |  |  |  |  |  |  | (45,700) |  |  |  |  |  |  |
Leaseholds and Leasehold Improvements | New Mexico 2015 Rate Case | Palo Verde Nuclear Generating Station, Units 1 And 4 | Public Service Company of New Mexico |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of impairment to carrying amount of regulatory assets |  |  |  |  |  |  |  | $ 37,700 |  |  |  |  |  |  |

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