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Financing - Schedule of Long-Term Debt Outstanding and Unamortized (Premiums), Discounts, and Debt Issuance Costs (Details) - USD ($) $ in Thousands | Dec. 31, 2024 | Dec. 31, 2023
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Debt Instrument [Line Items] |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 15,846 | $ 3,932
Total | 4,939,214 | 4,525,743
Principal, less current maturities | 611,907 | 280,529
Unamortized discounts, (premiums), and issuance costs, net, less current maturities | 304 | 360
Long-term debt, excluding current maturities, gross | 4,327,307 | 4,245,214
Unamortized discounts, (premiums), and issuance costs, net, excluding current maturities | 15,542 | 3,572
PNM |  |
Debt Instrument [Line Items] |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | 10,424 | 10,765
Total | 2,470,016 | 2,272,545
Principal, less current maturities | 560,907 | 200,529
Unamortized discounts, (premiums), and issuance costs, net, less current maturities | 270 | 307
Long-term debt, excluding current maturities, gross | 1,909,109 | 2,072,016
Unamortized discounts, (premiums), and issuance costs, net, excluding current maturities | 10,154 | 10,458
PNM | Senior Secured Notes, Energy Transition Bonds | Series A-1, 5.64% |  |
Debt Instrument [Line Items] |  |
Secured long-term debt, noncurrent | 172,471 | 175,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 1,025 | 1,093
PNM | Senior Unsecured Notes, Pollution Control Revenue Bonds: | Series A-1, 5.64% |  |
Debt Instrument [Line Items] |  |
Stated percentage (as a percent) | 5.64% |
PNM | Senior Unsecured Notes, Pollution Control Revenue Bonds: | Series A-2, 6.03% |  |
Debt Instrument [Line Items] |  |
Secured long-term debt, noncurrent | $ 168,200 | 168,200
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 1,014 | 1,057
Stated percentage (as a percent) | 6.03% |
PNM | Senior Unsecured Notes, Pollution Control Revenue Bonds: | 2.15% due April 2033 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 146,000 | 146,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 736 | 824
Stated percentage (as a percent) | 2.15% |
PNM | Senior Unsecured Notes, Pollution Control Revenue Bonds: | 3.00% due June 2040, mandatory tender - June 1, 2024 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 0 | 37,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 0 | 88
Stated percentage (as a percent) | 3.00% |
PNM | Senior Unsecured Notes, Pollution Control Revenue Bonds: | 0.875% mandatory tender - October 1, 2026 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 100,345 | 100,345
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 257 | 403
Stated percentage (as a percent) | 0.875% |
PNM | Senior Unsecured Notes, Pollution Control Revenue Bonds: | 3.00% due January 2038, mandatory tender - June 1, 2024 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 0 | 36,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 0 | 87
Stated percentage (as a percent) | 3.00% |
PNM | Senior Unsecured Notes, Pollution Control Revenue Bonds: | 1.15% due June 2040, mandatory tender - June 1, 2024 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 0 | 125,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 0 | 132
Stated percentage (as a percent) | 1.15% |
PNM | Senior Unsecured Notes, Pollution Control Revenue Bonds: | 3.90% due June 2040, mandatory tender - June 1, 2028 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 130,000 | 130,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 796 | 1,029
Stated percentage (as a percent) | 3.90% |
PNM | Senior Unsecured Notes, Pollution Control Revenue Bonds: | 3.875% due June 2040, mandatory tender - June 1, 2029 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 162,000 | 0
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 1,158 | 0
Stated percentage (as a percent) | 3.875% |
PNM | Senior Unsecured Notes, Pollution Control Revenue Bonds: | 3.875% due January 2038, mandatory tender - June 1, 2029 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 36,000 | 0
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 258 | 0
Stated percentage (as a percent) | 3.875% |
PNM | Senior Unsecured Notes: | 3.45% due May 2025 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 104,000 | 104,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 39 | 143
Stated percentage (as a percent) | 3.45% |
PNM | Senior Unsecured Notes: | 3.85% due August 2025 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 250,000 | 250,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 174 | 477
Stated percentage (as a percent) | 3.85% |
PNM | Senior Unsecured Notes: | 3.68% due May 2028 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 88,000 | 88,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 209 | 271
Stated percentage (as a percent) | 3.68% |
PNM | Senior Unsecured Notes: | 3.78% due August 2028 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 15,000 | 15,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 38 | 48
Stated percentage (as a percent) | 3.78% |
PNM | Senior Unsecured Notes: | 3.93% due May 2033 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 38,000 | 38,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 149 | 167
Stated percentage (as a percent) | 3.93% |
PNM | Senior Unsecured Notes: | 4.22% due May 2038 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 45,000 | 45,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 212 | 228
Stated percentage (as a percent) | 4.22% |
PNM | Senior Unsecured Notes: | 4.50% due May 2048 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 20,000 | 20,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 110 | 114
Stated percentage (as a percent) | 4.50% |
PNM | Senior Unsecured Notes: | 4.60% due August 2048 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 85,000 | 85,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 470 | 490
Stated percentage (as a percent) | 4.60% |
PNM | Senior Unsecured Notes: | 3.21% due April 2030 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 150,000 | 150,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 852 | 1,011
Stated percentage (as a percent) | 3.21% |
PNM | Senior Unsecured Notes: | 3.57% due April 2039 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 50,000 | 50,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 398 | 426
Stated percentage (as a percent) | 3.57% |
PNM | Senior Unsecured Notes: | 2.59% due July 2033 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 80,000 | 80,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 328 | 366
Stated percentage (as a percent) | 2.59% |
PNM | Senior Unsecured Notes: | 3.14% due July 2041 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 80,000 | 80,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 381 | 404
Stated percentage (as a percent) | 3.14% |
PNM | Senior Unsecured Notes: | 2.29% due December 2031 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 50,000 | 50,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 205 | 235
Stated percentage (as a percent) | 2.29% |
PNM | Senior Unsecured Notes: | 2.97% due December 2041 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 100,000 | 100,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 499 | 528
Stated percentage (as a percent) | 2.97% |
PNM | Senior Unsecured Notes: | 5.51% due April 2035 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 150,000 | 150,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 779 | 854
Stated percentage (as a percent) | 5.51% |
PNM | Senior Unsecured Notes: | 5.92% due April 2053 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 50,000 | 50,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 280 | 290
Stated percentage (as a percent) | 5.92% |
PNM | Senior Unsecured Notes: | PNM 2024 $200.0 Million Term Loan due November 2025 |  |
Debt Instrument [Line Items] |  |
Term loans | $ 200,000 | 0
Unamortized Discounts, (Premiums), and Issuance Costs, net | 57 | 0
TNMP |  |
Debt Instrument [Line Items] |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | (5,881) | (7,682)
Total | 1,458,198 | 1,253,198
Principal, less current maturities | 0 | 80,000
Unamortized discounts, (premiums), and issuance costs, net, less current maturities | 0 | 53
Long-term debt, excluding current maturities, gross | 1,458,198 | 1,173,198
Unamortized discounts, (premiums), and issuance costs, net, excluding current maturities | (5,881) | (7,735)
TNMP | First Mortgage Bonds: | 6.95% due April 2043 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | 93,198 | 93,198
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ (13,056) | (13,771)
Stated percentage (as a percent) | 6.95% |
TNMP | First Mortgage Bonds: | 4.03% due July 2024 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 0 | 80,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 0 | 53
Stated percentage (as a percent) | 4.03% |
TNMP | First Mortgage Bonds: | 3.53% due February 2026 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 60,000 | 60,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 91 | 174
Stated percentage (as a percent) | 3.53% |
TNMP | First Mortgage Bonds: | 3.22% due August 2027 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 60,000 | 60,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 152 | 209
Stated percentage (as a percent) | 3.22% |
TNMP | First Mortgage Bonds: | 3.85% due June 2028 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 60,000 | 60,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 219 | 281
Stated percentage (as a percent) | 3.85% |
TNMP | First Mortgage Bonds: | 3.79% due March 2034 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 75,000 | 75,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 347 | 385
Stated percentage (as a percent) | 3.79% |
TNMP | First Mortgage Bonds: | 3.92% due March 2039 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 75,000 | 75,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 401 | 429
Stated percentage (as a percent) | 3.92% |
TNMP | First Mortgage Bonds: | 4.06% due March 2044 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 75,000 | 75,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 433 | 456
Stated percentage (as a percent) | 4.06% |
TNMP | First Mortgage Bonds: | 3.60% due July 2029 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 80,000 | 80,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 270 | 330
Stated percentage (as a percent) | 3.60% |
TNMP | First Mortgage Bonds: | 2.73% due April 2030 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 85,000 | 85,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 445 | 530
Stated percentage (as a percent) | 2.73% |
TNMP | First Mortgage Bonds: | 3.36% due April 2050 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 25,000 | 25,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 210 | 218
Stated percentage (as a percent) | 3.36% |
TNMP | First Mortgage Bonds: | 2.93% due July 2035 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 25,000 | 25,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 175 | 191
Stated percentage (as a percent) | 2.93% |
TNMP | First Mortgage Bonds: | 3.36% due July 2050 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 50,000 | 50,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 424 | 441
Stated percentage (as a percent) | 3.36% |
TNMP | First Mortgage Bonds: | 2.44% due August 2035 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 65,000 | 65,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 382 | 418
Stated percentage (as a percent) | 2.44% |
TNMP | First Mortgage Bonds: | 4.13% due May 2052 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 65,000 | 65,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 409 | 424
Stated percentage (as a percent) | 4.13% |
TNMP | First Mortgage Bonds: | 3.81% due July 2032 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 95,000 | 95,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 505 | 572
Stated percentage (as a percent) | 3.81% |
TNMP | First Mortgage Bonds: | 5.01% due April 2033 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 130,000 | 130,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 610 | 682
Stated percentage (as a percent) | 5.01% |
TNMP | First Mortgage Bonds: | 5.47% due July 2053 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 55,000 | 55,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 286 | 296
Stated percentage (as a percent) | 5.47% |
TNMP | First Mortgage Bonds: | 5.26% due March 2029 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 32,000 | 0
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 189 | 0
Stated percentage (as a percent) | 5.26% |
TNMP | First Mortgage Bonds: | 5.55% due March 2036 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 85,000 | 0
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 538 | 0
Stated percentage (as a percent) | 5.55% |
TNMP | First Mortgage Bonds: | 5.65% due July 2039 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 40,000 | 0
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 256 | 0
Stated percentage (as a percent) | 5.65% |
TNMP | First Mortgage Bonds: | 5.79% due July 2054 |  |
Debt Instrument [Line Items] |  |
Unsecured long-term debt, noncurrent | $ 128,000 | 0
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 833 | 0
Stated percentage (as a percent) | 5.79% |
TXNM |  |
Debt Instrument [Line Items] |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 11,303 | 849
Total | 1,011,000 | 1,000,000
Principal, less current maturities | 51,000 | 0
Unamortized discounts, (premiums), and issuance costs, net, less current maturities | 34 | 0
Long-term debt, excluding current maturities, gross | 960,000 | 1,000,000
Unamortized discounts, (premiums), and issuance costs, net, excluding current maturities | 11,269 | 849
TXNM | TXNM 2021 Delayed-Draw Term Loan due May 2025 |  |
Debt Instrument [Line Items] |  |
Term loans | 51,000 | 500,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | 34 | 114
TXNM | TXNM 2023 Term Loan due June 2026 |  |
Debt Instrument [Line Items] |  |
Term loans | 410,000 | 500,000
Unamortized Discounts, (Premiums), and Issuance Costs, net | 441 | 735
TXNM | 5.75% TXNM Junior Subordinated Convertible Notes due June 2054 |  |
Debt Instrument [Line Items] |  |
Term loans | 550,000 | 0
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 10,828 | $ 0
Stated percentage (as a percent) | 5.75% |

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