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Financing - Activities, PNM and TNMP (Details) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 Months Ended | 6 Months Ended | 9 Months Ended | 12 Months Ended |  |  |  |  |  |  |  |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Jan. 08, 2020 shares | Jan. 07, 2020 $ / shares shares | Jul. 01, 2019 USD ($) | Apr. 01, 2019 USD ($) | Feb. 26, 2019 USD ($) | Dec. 21, 2018 USD ($) | Dec. 14, 2018 USD ($) | Nov. 26, 2018 USD ($) | Jul. 31, 2018 USD ($) | May 14, 2018 USD ($) | Apr. 09, 2018 USD ($) | Jan. 01, 2018 USD ($) | Dec. 15, 2017 | Jul. 28, 2017 USD ($) | Dec. 31, 2018 USD ($) shares | Jul. 31, 2018 USD ($) | Jun. 30, 2018 | Sep. 30, 2018 | Dec. 31, 2019 USD ($) shares | Dec. 31, 2018 USD ($) shares | Dec. 31, 2017 USD ($) derivative | Dec. 18, 2019 USD ($) | Mar. 29, 2019 USD ($) | Jan. 18, 2019 USD ($) | Dec. 17, 2018 USD ($) | Jul. 25, 2018 USD ($) | Jun. 28, 2018 USD ($) | May 22, 2018 USD ($) | Mar. 09, 2018 USD ($) | Jul. 20, 2017 USD ($) | Jun. 14, 2017 USD ($) | Jan. 01, 2017 USD ($) loan | Feb. 01, 2016 USD ($) | Mar. 09, 2015 USD ($)
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 235,900,000 |  |  |  | $ 185,100,000 | $ 235,900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock, shares issued (in shares) | shares |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 79,653,624 |  |  |  | 79,653,624 | 79,653,624 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest charges |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 121,016,000 | $ 127,244,000 | $ 127,625,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Other deferred credits |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 167,668,000 |  |  |  | $ 185,753,000 | 167,668,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed interest rate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1.927% |  |
PNMR 2016 One-Year Term Loan and PNMR 2016 Two-Year Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of loan agreements (in loans) | loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |
PNMR 2016 One Year Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 100,000,000.0 |  |
Debt instrument, term |  |  |  |  |  |  |  |  |  |  |  |  | 1 year |  | 1 year | 1 year |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR 2016 Two-Year Term Loan due December 2018 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loan entered into |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 100,000,000.0 |  |
Debt instrument, term |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 years | 2 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR Development Term Loan due November 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding amount |  |  |  |  |  |  |  | $ 90,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Variable interest rate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.60% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR 2018 One Year Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  | $ 150,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 150,000,000 |  |  |  | $ 0 | 150,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, term |  |  |  |  |  |  | 1 year |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Variable interest rate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.70% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR 2018 Two-Year Term Loan due December 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  | $ 50,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, term |  |  |  |  |  | 2 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Variable interest rate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.60% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
TNMP 2018 Term Loan Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loan restatement to provide additional funding |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 15,000,000.0 |  |  |  |  |  |  |  |  |
TNMP 2018 Term Loan due July 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loan restatement committed amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 35,000,000.0 |  |  |  |  |  |  |  |  |
Variable Rate Short-Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |
Time hedged in interest rate cash flow hedge |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Level 2 | Cash Flow Hedging |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fair value gain (loss, less than) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 400,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fair value gain (loss, less than) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 42,400,000 |  |  |  | $ 58,000,000 | $ 42,400,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock, shares issued (in shares) | shares |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 39,117,799 |  |  |  | 39,117,799 | 39,117,799 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest charges |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 72,900,000 | $ 76,458,000 | 82,697,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Other deferred credits |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 215,737,000 |  |  |  | 155,744,000 | 215,737,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico | San Juan Generating Station |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Request issuance of energy transition bonds |  |  | $ 361,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 361,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico | PNM 2019 $250.0 Million Term Loan due July 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 250,000,000.0 |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico | PNM 2019 $40.0 Million Term Loan due June 2021 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 40,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico | NMPRC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Requirement to obtain approval for any financing transaction, period of time (more than) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 18 months |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR | PNMR Development Term Loan due November 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loan entered into |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 90,000,000 |  |  |  | $ 90,000,000 | 90,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR | PNMR 2018 Two-Year Term Loan due December 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loan entered into |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50,000,000 |  |  |  | 50,000,000 | 50,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
NM Capital | San Juan Coal Company, Westmoreland | Coal Supply |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loan entered into |  |  |  |  |  |  |  |  |  |  |  | $ 50,100,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repurchased face amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 50,100,000 |  |  |  |  |  |
NM Capital | San Juan Generating Station | Coal Supply |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payments to fund long-term loans to unaffiliated third party |  |  |  |  |  |  |  |  |  |  |  | 125,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Texas-New Mexico Power Company |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 17,500,000 |  |  |  | $ 15,000,000 | $ 17,500,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock, shares issued (in shares) | shares |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 6,358 |  |  |  | 6,358 | 6,358 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest charges |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 29,100,000 | $ 32,091,000 | $ 30,084,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Other deferred credits |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 2,908,000 |  |  |  | $ 7,469,000 | 2,908,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Line of Credit |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt-to-capital ratios (less than or equal to) |  |  |  |  |  |  |  | 70.00% |  |  |  |  |  |  |  |  | 65.00% | 65.00% | 70.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Line of Credit | Public Service Company of New Mexico |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt-to-capital ratios (less than or equal to) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 65.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Line of Credit | Texas-New Mexico Power Company |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt-to-capital ratios (less than or equal to) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 65.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR 2015 Term Loan Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loan entered into |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 150,000,000.0 |  | $ 150,000,000.0
BTMU Term Loan Agreement | NM Capital |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loan entered into |  |  |  |  |  |  |  |  |  |  |  | $ 125,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 125,000,000.0 |
Repurchased face amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 43,000,000.0 |  |  |  |  |  |
Estimated principal payments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 43,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Letter of Credit | PNMR | Letter or credit, 30 mil JP Morgan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 30,300,000 |  |
Senior Unsecured Notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 300,000,000.0 |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3.25% |  |  |  |  |
Senior Unsecured Notes | Public Service Company of New Mexico | Senior Unsecured Note Agreement (SUNs) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 450,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt to capital ratio |  |  |  |  |  |  |  |  |  |  |  |  |  | 65.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Unsecured Notes | Public Service Company of New Mexico | SUNs, Issuance in May 2018 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  | $ 350,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Unsecured Notes | Public Service Company of New Mexico | SUN's, Issuance in July 2018 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  | $ 100,000,000.0 |  |  |  |  |  |  | $ 100,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNM 2016 Term Loan Agreement due 2017 | Public Service Company of New Mexico |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 175,000,000.0 |  |
Pollution Control Bonds | Public Service Company of New Mexico | Pollution Control Revenue Bonds 2.125 Percent, due 2040 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 37,000,000.0 |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.125% |  |
Pollution Control Bonds | Public Service Company of New Mexico | Pollution Control Revenue Bonds 2.45 Percent, due 2042 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 20,000,000.0 |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.45% |  |
Unsecured Debt | Public Service Company of New Mexico |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Shelf registration statement, capacity of issuance (up to) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 475,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Unsecured Debt | Public Service Company of New Mexico | PNM 2017 Term Loan Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loan entered into |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 200,000,000 |  |  |  | 0 | 200,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Unsecured Debt | Public Service Company of New Mexico | SUNs, Issuance in May 2018 | Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, term |  |  |  |  |  |  |  |  |  | 5 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  | 3.15% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Unsecured Debt | Public Service Company of New Mexico | SUNs, Issuance in May 2018 | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, term |  |  |  |  |  |  |  |  |  | 30 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  | 4.50% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Unsecured Debt | Public Service Company of New Mexico | SUN's, Issuance in July 2018 | Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, term |  |  |  |  |  |  |  |  | 10 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  | 3.78% |  |  |  |  |  |  | 3.78% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Unsecured Debt | Public Service Company of New Mexico | SUN's, Issuance in July 2018 | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, term |  |  |  |  |  |  |  |  | 30 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  | 4.60% |  |  |  |  |  |  | 4.60% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Unsecured Debt | Public Service Company of New Mexico | 7.95% due May 2018 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  | 7.95% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Unsecured Debt | Public Service Company of New Mexico | 7.50% due August 2018 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  | 7.50% |  |  |  |  |  |  | 7.50% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Unsecured Debt | Public Service Company of New Mexico | PNM 2019 $250.0 Million Term Loan due July 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loan entered into |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 |  |  |  | 250,000,000 | 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Unsecured Debt | Public Service Company of New Mexico | PNM 2019 $40.0 Million Term Loan due June 2021 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loan entered into |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 40,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Unsecured Debt | Texas-New Mexico Power Company | 9.50% due April 2019 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  | 9.50% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Extinguishment of debt |  |  |  | $ 172,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
First Mortgage Bonds | Texas-New Mexico Power Company | Interest Rate of 3.22%, Due 2027 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 60,000,000.0 |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3.22% |  |  |
First Mortgage Bonds | Texas-New Mexico Power Company | TNMP 2018 Term Loan due July 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loan entered into |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 35,000,000 |  |  |  | $ 0 | 35,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
First Mortgage Bonds | Texas-New Mexico Power Company | 9.50% due April 2019 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 9.50% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
First Mortgage Bonds | Texas-New Mexico Power Company | 3.60% due July 2029 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3.60% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgages | Texas-New Mexico Power Company | First Mortgage Bonds |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 60,000,000.0 |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3.85% |  |  |  |  |  |  |
Mortgages | Texas-New Mexico Power Company | TNMP 2019 Bond Purchase Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  | $ 305,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 225,000,000.0 |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  | 400.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt to capital ratio |  |  |  |  | 65.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgages | Texas-New Mexico Power Company | 3.60% due July 2029 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  | $ 80,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Secured Debt | Texas-New Mexico Power Company | TNMP Term Loan Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 20,000,000.0 |  |  |  |  |  |  |  |
JPMorgan Chase Bank, N.A. and U.S. Bank National Association | PNM 2016 Term Loan Agreement due 2017 | Public Service Company of New Mexico |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 175,000,000.0 |  |  |  |
JPMorgan Chase Bank, N.A. and U.S. Bank National Association | Notes Payable to Banks | Public Service Company of New Mexico | PNM 2017 Term Loan Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  | $ 200,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
JPMorgan Chase Bank, N.A. and U.S. Bank National Association | Notes Payable to Banks | Public Service Company of New Mexico | PNM 2019 $250.0 Million Term Loan due July 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.45% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
JPMorgan Chase Bank, N.A. and U.S. Bank National Association | Notes Payable to Banks | Public Service Company of New Mexico | PNM 2019 $40.0 Million Term Loan due June 2021 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.39% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate contract |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of derivative instruments held | derivative |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate contract one | Variable Rate Short-Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed interest rate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1.926% |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate contract two | Variable Rate Short-Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed interest rate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1.823% |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate contract three | Variable Rate Short-Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed interest rate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1.629% |  |  |  |  |  |  |  |  |  |  |  |  |
Deposit Related to Potential Transmission Interconnections | PNMR Development |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of related party transaction |  |  |  |  |  |  |  |  |  |  | $ 68,200,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Accrued interest |  |  |  |  |  |  |  |  |  |  | 5,700,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest charges |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 3,300,000 | $ 2,400,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other deferred credits |  |  |  |  |  |  |  |  |  |  | $ 68,200,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR 2020 Forward Equity Sales Agreement | Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock, shares issued (in shares) | shares |  | 6,200,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sale of stock, price per share (in dollars per share) | $ / shares |  | $ 47.21 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Over-Allotment Option | Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of shares issued in transaction (in shares) | shares | 800,000 | 800,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

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