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Financing - Financing Activities (Details) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 12 Months Ended |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
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. 15, 2020 USD ($) $ / shares shares | Jun. 22, 2020 USD ($) | Apr. 30, 2020 USD ($) | Apr. 15, 2020 USD ($) | Jan. 08, 2020 shares | Jan. 07, 2020 $ / shares shares | Jan. 01, 2020 USD ($) | Dec. 18, 2019 USD ($) | Apr. 01, 2019 USD ($) | Dec. 21, 2018 | Dec. 31, 2021 USD ($) shares | Dec. 31, 2020 USD ($) shares | Dec. 31, 2019 USD ($) bond_series | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) derivative | Feb. 18, 2022 USD ($) | Oct. 01, 2021 | Sep. 23, 2021 USD ($) | Aug. 16, 2021 USD ($) | Nov. 25, 2020 USD ($) | Jul. 15, 2020 USD ($) | Jun. 01, 2020 USD ($) | Apr. 24, 2020 USD ($) bond_series | Jul. 01, 2019 USD ($) | Mar. 29, 2019 USD ($) | Feb. 26, 2019 USD ($) | Jan. 18, 2019 USD ($) | Jan. 01, 2019 USD ($) | Dec. 17, 2018 USD ($) | Jul. 25, 2018 USD ($) | Jan. 01, 2018 USD ($)
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Short-term debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 62,700,000 | $ 32,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Financing capacity |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 40,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest expenses |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 96,877,000 | 114,392,000 | $ 121,016,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Letters of credit outstanding |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3,400,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cash Flow Hedge | Significant Other Observable Inputs (Level 2) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fair value gain (loss, less than) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate contract |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of derivatives | derivative |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Short-term debt - affiliate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revolving Credit Facility | Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Available borrowing capacity |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 799,800,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR 2020 Forward Equity Sales Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock, shares issued (in shares) | shares |  |  |  |  |  |  |  |  |  |  |  |  |  | 6,200,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of shares issued in transaction (in shares) | shares |  |  |  |  |  |  |  |  | 6,200,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sale of stock, price per share (in dollars per share) | $ / shares |  |  |  |  |  |  |  |  | $ 45.805 |  |  |  |  | $ 47.21 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sale of stock, consideration received on transaction |  |  |  |  |  |  |  |  | $ 283,100,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payments of stock issuance costs |  |  |  |  |  |  |  |  | $ 100,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Over-Allotment Option |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of shares issued in transaction (in shares) | shares |  |  |  |  |  |  |  |  |  |  |  |  | 800,000 | 800,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR 2018 Two-Year Term Loan due December 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, term |  |  |  |  |  |  |  | 2 years |  |  |  |  |  |  |  |  |  | 2 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR 2020 Delayed-Draw Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loans |  |  |  |  |  |  | $ 300,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Available borrowing capacity |  |  |  |  |  | $ 220,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from Long-term Lines of Credit |  |  |  |  |  |  | 80,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR 2020 Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loans |  |  |  |  |  |  |  | $ 150,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
2.44% due August 2035 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loan restatement to provide additional funding |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 15,000,000 |  |
Term loan restatement committed amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 35,000,000 |  |
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% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
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 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Short-term debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 7,400,000 | $ 10,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock, shares issued (in shares) | shares |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 39,117,799 | 39,117,799 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest expenses |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 51,360,000 | $ 64,615,000 | 72,900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Letters of credit outstanding |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNM | Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Consolidated invested cash |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNM | PNM 2019 $250 Million Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 250,000,000 |  |  |  |
PNM | PNM 2019 $40.0 Million Term Loan due June 2021 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 40,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  |  | $ 40,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNM | PNM 2019 Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  |  | 40,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNM | PNM Revolving Credit Facility | Revolving Credit Facility |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 40,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Short-term debt - affiliate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 6,400,000 | 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR | Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Short-term debt - affiliate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 6,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR | PNMR 2018 Two-Year Term Loan due December 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  | $ 220,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR | PNMR 3.25% 2018 SUNs due March 2021 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loans |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 0 | 300,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3.25% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR | PNMR 2020 Delayed-Draw Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loans |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 0 | 80,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR | PNMR Development Term Loan due January 2022 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loans |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 65,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR | PNMR 2020 Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loans |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 150,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR | PNMR 2021 Delayed-Draw Term Loan due May 2023 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loans |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 900,000,000 | 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR | PNM 2019 Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loans |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 150,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR Development |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Short-term debt - affiliate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR Development | Deposit Related to Potential Transmission Interconnections |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of related party transaction |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 68,200,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Accrued interest |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 5,700,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest expenses |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR Development | Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Short-term debt - affiliate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Texas-New Mexico Power Company |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Short-term debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 400,000 | $ 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock, shares issued (in shares) | shares |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 6,358 | 6,358 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest expenses |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 33,735,000 | $ 30,388,000 | 29,100,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Letters of credit outstanding |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Texas-New Mexico Power Company | Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Short-term debt - affiliate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 45,500,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Consolidated invested cash |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Line of Credit | PNMR 2021 Delayed-Draw Term Loan due May 2023 | Revolving Credit Facility |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from Long-term Lines of Credit |  | $ 50,000,000 |  |  | $ 850,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rates on outstanding borrowings |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.95% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Line of Credit | PNMR 2021 Delayed-Draw Term Loan due May 2023 | Revolving Credit Facility | Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from Long-term Lines of Credit | $ 100,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
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 | 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% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Line of Credit | PNM | PNM Revolving Credit Facility |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  |  |  |  |  | $ 100,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Letter of Credit | PNMR | Letter or credit, 30 mil JP Morgan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 30,300,000
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 2019 $40.0 Million Term Loan due June 2021 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loans |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | $ 40,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Unsecured Notes | PNM | PNM 2021 $75.0 Million Term Loan due December 2022 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loans |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 75,000,000 | 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Unsecured Notes | Texas-New Mexico Power Company | First Mortgage Bonds at 9.50% due 2019 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 9.50% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Extinguishment of debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 172,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Medium-term Notes | PNMR Development Term Loan due January 2022 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 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 | PNM | PNM 2019 Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  |  |  |  |  |  | $ 250,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Medium-term Notes | PNM | PNM 2020 $250.0 Million Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  | $ 250,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  |  | 150,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Bonds |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  |  |  |  | $ 302,500,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Bonds | City of Farmington, New Mexico |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 266,500,000 |  |  |  |  |  |  |  |  |
Bonds | PNMR 2018 Two-Year Term Loan due December 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  |  | $ 50,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
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 | Pollution Control Revenue Bonds Due June Twenty Twenty |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loans |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 100,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number Of Outstanding PCRB's Subject To Mandatory Tender | bond_series |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Bonds | Pollution Control Revenue Bonds Due June Twenty Forty |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loans |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 40,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number Of Outstanding PCRB's Subject To Mandatory Tender | bond_series |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Bonds | Pollution Control Revenue Bonds, Due 2043 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number Of Outstanding PCRB's Subject To Mandatory Tender | bond_series |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Bonds | Pollution Control Revenue Bonds, Due 2043, Series 1 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loans |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 39,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Bonds | Pollution Control Revenue Bonds, Due 2043, Series 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loans |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 21,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Bonds | PNM 2021 Fixed Rate PCRBs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.875% |  |  |  |  |  |  |  |  |  |  |  |  |  |
Bonds | Pollution Control Revenue Bonds, 6.25%, Callable | Maricopa County, Arizona Pollution Control Corporation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 36,000,000 |  |  |  |  |  | $ 36,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 6.25% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, redemption price, percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 101.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Bonds | Pollution Control Revenue Bonds, 6.25%, Callable | City of Farmington, New Mexico |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 11,500,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 6.25% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Bonds | Pollution Control Revenue Bonds, 5.90%, Callable | City of Farmington, New Mexico |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 255,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5.90% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Bonds | Pollution Control Revenue Bonds, Due 2033 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loans |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 146,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.15% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notes Payable to Banks | PNM | PNM 2017 Term Loan Agreement | JPMorgan Chase Bank, N.A. and U.S. Bank National Association |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 200,000,000 |  |  |
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 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Variable interest rate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.93% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Notes | Senior Unsecured Notes, 3.21% Series A, due April 2030 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  | $ 150,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  | 3.21% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Notes | Senior Unsecured Notes, 3.57% Series B, due April 2039 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  | $ 50,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  | 3.57% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
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 | PNM SUNs At 5.35 Percent Due October 1, 2021 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  | 5.35% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  | $ 160,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Notes | Two Point Two Nine Percent Senior Unsecured Notes Due July 15, 2033 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.29% |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Notes | Two Point Two Nine Percent Senior Unsecured Notes Due December 30, 2031 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  | $ 50,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Notes | Two Point Nine Seven Senior Unsecured Notes Due December 30, 2041 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 100,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.97% |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Notes | PNM |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  | $ 200,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Notes | PNM | PNM 2020 $250.0 Million Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  |  |  |  |  | $ 100,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Notes | PNM | PNM 2021 Note Purchase Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  | 160,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Notes | PNM | PNM September 2021 Note Purchase Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 150,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Secured Debt | Texas-New Mexico Power Company | TNMP Term Loan Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 20,000,000 |
Secured Debt | Texas-New Mexico Power Company | TNMP 2020 Bond Purchase Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 185,000,000 |  |  |  |  |  |  |  |
Series of bond issuance | bond_series |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4 |  |  |  |  |  |  |  |
Secured Debt | Texas-New Mexico Power Company | TNMP 2020 Bond Purchase Agreement, Bond Series 1 and 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 110,000,000 |  |  |  |  |  |  |  |
Secured Debt | Texas-New Mexico Power Company | TNMP 2020 Bond Purchase Agreement, Bond Series 3 and 4 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 75,000,000 |  |  |  |  |  |  |  |  |  |
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% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgages | Texas-New Mexico Power Company | TNMP 2019 Bond Purchase Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 225,000,000 | $ 305,000,000 |  |  |  |  |
Stated percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 400.00% |  |  |  |  |
Mortgages | Texas-New Mexico Power Company | First Mortgage Bonds at 3.60% due 2029 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate principal amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 80,000,000 |  |  |  |  |  |  |

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- Definition Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123466204&loc=SL6036836-161870 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=124435984&loc=d3e28551-108399 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=124429444&loc=SL124452920-239629 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 1B -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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