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Financing - Financing Activities (Details) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 12 Months Ended |  |  |  |  |  |  |
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Nov. 10, 2022 USD ($) $ / shares | Oct. 31, 2022 USD ($) derivative | Sep. 30, 2022 USD ($) derivative | Aug. 05, 2022 USD ($) | May 20, 2022 USD ($) | May 02, 2022 USD ($) derivative | Jan. 24, 2022 USD ($) | Dec. 02, 2021 USD ($) | Jul. 14, 2021 USD ($) | Jun. 18, 2021 USD ($) | May 18, 2021 USD ($) | Mar. 09, 2021 USD ($) | Dec. 22, 2020 USD ($) | Dec. 21, 2020 USD ($) | Dec. 31, 2022 USD ($) $ / shares | Dec. 31, 2017 USD ($) derivative | Jun. 01, 2022 USD ($) derivative | Apr. 27, 2022 USD ($) bond | Dec. 31, 2021 USD ($) $ / shares | Oct. 01, 2021 USD ($) | Aug. 16, 2021 USD ($) | Dec. 31, 2020 USD ($) | Dec. 30, 2020 USD ($)
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock, no par value (in dollars per share) | $ / shares |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  |
Cash flow hedge derivative instrument assets at fair value |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 11,100,000 |  |  |  |  |  |  |  |
Interest rate contract |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of derivatives | derivative |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 |  |  |  |  |  |  |
Interest rate contract | Cash Flow Hedge |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative asset, number of instruments held | derivative |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |
PNMR 2022 ATM Program |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distribution agreement, sale of stock | $ 200,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock, no par value (in dollars per share) | $ / shares | $ 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR 2020 Delayed-Draw Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Available borrowing capacity |  |  |  |  |  |  |  |  |  |  |  | $ 220,000,000 |  |  |  |  |  |  |  |  |  |  |
Term loans |  |  |  |  |  |  |  |  |  |  |  |  | $ 300,000,000 |  |  |  |  |  |  |  |  |  |
Proceeds from long-term lines of credit |  |  |  |  |  |  |  |  |  |  |  |  | 80,000,000 |  |  |  |  |  |  |  |  |  |
PNMR 2020 Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loans |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 150,000,000 |  |  |  |  |  |  |  |  |
PNMR 2018 Two-Year Term Loan due December 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, term |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 years |  |  |  |  |  |  |  |  |
Variable Rate Short-Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 50,000,000 |  |  |  |  |  |  |
Term of derivatives |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4 years |  |  |  |  |  |  |
Variable Rate Short-Term Debt | Interest rate 1 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed interest rate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1.926% |  |  |  |  |  |  |
Variable Rate Short-Term Debt | Interest rate 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed interest rate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1.823% |  |  |  |  |  |  |
Variable Rate Short-Term Debt | Interest rate 3 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed interest rate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1.629% |  |  |  |  |  |  |
Variable Rate Debt | Interest rate contract | Cash Flow Hedge |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, term |  |  | 15 months |  | 19 months | 20 months |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative asset, number of instruments held | derivative |  |  | 2 |  |  | 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed interest rate |  |  |  |  | 2.52% | 2.65% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative asset, notional amount |  |  | $ 200,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative, notional amount |  |  |  |  | $ 100,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Variable Rate Debt, Tranche 1 | Interest rate contract | Cash Flow Hedge |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Variable interest rate |  |  | 4.17% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative asset, notional amount |  |  | $ 100,000,000 |  |  | $ 150,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Variable Rate Debt, Tranche 2 | Interest rate contract | Cash Flow Hedge |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Variable interest rate |  |  | 4.18% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative asset, notional amount |  |  | $ 100,000,000 |  |  | $ 200,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed Rate Debt | Interest rate contract | Cash Flow Hedge |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, term |  | 14 months |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative asset, number of instruments held | derivative |  | 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed Rate Debt, Tranche 1 | Interest rate contract | Cash Flow Hedge |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed interest rate |  | 4.66% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative asset, notional amount |  | $ 100,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed Rate, Tranche 2 | Interest rate contract | Cash Flow Hedge |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed interest rate |  | 4.65% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative asset, notional amount |  | $ 200,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Short-term debt - affiliate |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 150,000,000 |  |  |  |  |  |  |  |
PNM and TNMP |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Short-term debt - affiliate |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  |
PNM |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maturity term over which financings require regulator approval (more than) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 18 months |  |  |  |  |  |  |  |
Common stock, no par value (in dollars per share) | $ / shares |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  |
PNM | PNM 2019 $— Million Term Loan due June 2021 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 40,000,000 |
Repayments of debt |  |  |  |  |  |  |  |  |  | $ 40,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Short-term debt - affiliate |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 5,300,000 |  |  |  | $ 6,400,000 |  |  |  |
PNMR | PNMR 2018 Two-Year Term Loan due December 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  |  |  |  |  |  |  | $ 220,000,000 |  |  |  |  |  |  |  |  |  |
PNMR | PNMR 2021 Delayed-Draw Term Loan due May 2025 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loans |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,000,000,000 |  |  |  | 900,000,000 |  |  |  |
PNMR Development |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Financing capacity |  |  |  |  |  |  |  |  |  |  | $ 40,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Short-term debt - affiliate |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 0 |  |  |  | 0 |  |  |  |
Line of Credit | PNMR 2021 Delayed-Draw Term Loan due May 2025 | Revolving Credit Facility |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from long-term lines of credit |  |  |  |  |  |  | $ 100,000,000 | $ 50,000,000 |  |  | 850,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Interest rates on outstanding borrowings |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5.37% |  |  |  |  |  |  |  |
Line of Credit | PNMR Development Revolving Credit Facility | Revolving Credit Facility |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  |  |  |  |  | 40,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Line of Credit | PNMR Revolving Credit Facility | Revolving Credit Facility |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  |  |  |  |  | 92,100,000 |  |  |  |  |  |  |  |  |  |  |  |
Line of Credit | PNM 2022 Delayed-Draw Term Loan | Revolving Credit Facility |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from long-term lines of credit |  |  | $ 45,000,000 | $ 180,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Financing capacity |  |  |  | $ 225,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Line of Credit | PNMR and PNMR Development |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ratio of debt to capital (less than or equal to) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 70.00% |  |  |  |  |  |  |  |
Line of Credit | PNM and TNMP |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ratio of debt to capital (less than or equal to) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 65.00% |  |  |  |  |  |  |  |
Senior Unsecured Notes | PNMR 3.25% 2018 SUNs due March 2021 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 300,000,000 |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3.25% |
Repayments of debt |  |  |  |  |  |  |  |  |  |  |  | $ 80,000,000 |  |  |  |  |  |  |  |  |  |  |
Senior Unsecured Notes | PNM |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Shelf registration statement, capacity of issuance (up to) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 650,000,000 |  |  |  |  |  |  |  |
Senior Unsecured Notes | PNM | PNM 2021 $75.0 Million Term Loan due December 2022 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loans |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 0 |  |  |  | 75,000,000.0 |  |  |  |
Medium-term Notes | PNMR Development Term Loan due January 2022 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 65,000,000 |  |  | $ 65,000,000 | $ 90,000,000
Repayments of debt |  |  |  |  |  |  |  |  |  |  | 65,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Medium-term Notes | PNMR 2019 Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 150,000,000 |
Medium-term Notes | PNMR 2021 Delayed-Draw Term Loan due May 2025 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  |  |  |  |  | 65,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Bonds | PNMR 2020 Delayed-Draw Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  |  |  |  |  | 300,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Bonds | PNMR 2019 Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  |  |  |  |  | 150,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Bonds | PNMR 2020 Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  |  |  |  |  | 150,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Bonds | PNMR 2018 Two-Year Term Loan due December 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 50,000,000 |  |  |  |  |  |  |  |  |
Bonds | PNMR 2021 Delayed-Draw Term Loan due May 2025 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  |  |  |  |  | $ 150,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Bonds | Pollution Control Revenue Bonds Due June 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loans |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 100,300,000 |
Bonds | PNM 2021 Fixed Rate PCRBs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.875% |  |  |
Bonds | Pollution Control Revenue Bonds, Due 2033 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.15% |  |  |
Term loans |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 146,000,000 |  | $ 146,000,000 |
Bonds | PNM | PNM 2021 $75.0 Million Term Loan due December 2022 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Variable interest rate |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5.09% |  |  |  |  |  |  |  |
Bonds | PNM | Pollution Control Revenue Bonds |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loans |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 31,500,000 |  | 104,500,000 |  |  |  |
Bonds | PNM | Pollution Control Revenue Bonds Due June 2038 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 36,000,000 |  | $ 36,000,000 |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1.05% |  |  |  |
Bonds | PNM | Pollution Control Revenue Bonds Due June 2040, 1 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 37,000,000 |  | $ 37,000,000 |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.125% |  |  |  |
Bonds | PNM | Pollution Control Revenue Bonds Due June 2040, 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 11,500,000 |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1.20% |  |  |  |
Bonds | PNM | Pollution Control Revenue Bonds Due June 2042 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 20,000,000 |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.45% |  |  |  |
Bonds | PNM | Pollution Control Revenue Bonds Due June 2024 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3.00% |  |  |  |  |  |
Bonds | Texas-New Mexico Power Company | TNMP 2022 Bond Purchase Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 160,000,000 |  |  |  |  |
Series of bond issuance | bond |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |
Bonds | Texas-New Mexico Power Company | TNMP 2022 Bond Purchase Agreement at 4.13% Due May 12, 2022 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 65,000,000 |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4.13% |  |  |  |  |
Bonds | Texas-New Mexico Power Company | TNMP 2022 Bond Purchase Agreement at 3.81% Due July 28, 2032 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 95,000,000 |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3.81% |  |  |  |  |
Notes Payable to Banks | PNM | PNM 2021 $75.0 Million Term Loan due December 2022 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  | $ 75,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Notes | PNM 2020 SUNs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  | 5.35% |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  |  |  | $ 160,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Notes | PNM 2021 SUNs At 2.59 Percent Due July 15, 2033 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 80,000,000 |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.59% |  |  |  |
Senior Notes | PNM 2021 SUNs At 3.14 Percent Due July 15, 2041 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 80,000,000 |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3.14% |  |  |  |
Senior Notes | 2.29% Senior Unsecured Notes Due December 30, 2031 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  | $ 50,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.29% |  |  |  |
Senior Notes | 2.97% Senior Unsecured Notes Due December 30, 2041 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 100,000,000 |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.97% |  |  |  |
Secured Debt | Texas-New Mexico Power Company | TNMP 2021 Bond Purchase Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  | $ 65,000,000 |  |  |  |  |  |  |  |  |  |  |  | $ 65,000,000 |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.44% |  |
Secured Debt | Texas-New Mexico Power Company | TNMP First Mortgage Bonds |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 750,000,000 |  |  |  |  |  |  |  |
Debt instrument, prepayment period |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 30 days |  |  |  |  |  |  |  |
Debt instrument, redemption price, percentage of principal amount redeemed |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 100.00% |  |  |  |  |  |  |  |

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