| Pay vs Performance Disclosure | 12 Months Ended |
| Dec. 31, 2022 USD ($) $ / shares | Dec. 31, 2021 USD ($) $ / shares | Dec. 31, 2020 USD ($) $ / shares |
| Pay vs Performance Disclosure [Table] | | | |
| Pay vs Performance [Table Text Block] | Value of Initial Fixed $100 Investment Based On: Year Summary Compensation Table Total for PEO Compensation Actually Paid to PEO Average Summary Compensation Table Total for Non-PEO Named Executive Officers Average Compensation Actually Paid to Non-PEO Named Executive Officers Total Shareholder Return Peer Group Total Shareholder Return Net Earnings (In thousands) Incentive EPS ($) ($) ($) ($) ($) ($) ($) ($) (1) (2) (3)(4) (2)(3) (5) (6) (7) (8) 2022 6,596,575 7,807,506 1,547,874 1,607,675 105 115 185,180 2.69 2021 5,594,739 4,294,466 1,188,098 930,313 105 115 211,847 2.45 2020 7,837,411 10,571,654 1,435,144 1,827,210 95 99 187,316 2.28 | | |
| Named Executive Officers, Footnote [Text Block] | For 2022, our non-PEO NEOs were Messrs. Eldred, Tarry, Apodaca and Darnell and Ms. Eden. For 2021, our non-PEO NEOs were Messrs. Eldred, Tarry, Olson and Darnell. For 2020, our non-PEO NEOs were Messrs. Eldred, Tarry, Apodaca, Darnell and Olson. | | |
| Peer Group Issuers, Footnote [Text Block] | Represents the TSR for the EEI Peer Index, which is a peer issuer group of electric companies. For purposes of the table, an investment of $100 (with reinvestment of all dividends) is assumed to have been made in the EEI Peer Index on December 31, 2019. | | |
| PEO Total Compensation Amount | $ 6,596,575 | $ 5,594,739 | $ 7,837,411 |
| PEO Actually Paid Compensation Amount | $ 7,807,506 | 4,294,466 | 10,571,654 |
| Adjustment To PEO Compensation, Footnote [Text Block] | Represents the “Total” compensation for our principal executive officer (“PEO”), Ms. Collawn, as set forth in 2022 NEO Compensation Information—Summary of Executive Compensation—Summary Compensation Table on page 61. Year Reported Summary Compensation Table Total Reported Value of Stock Awards Stock Award Adjustments Reported Change in the Actuarial Present Value of Pension Benefits Pension Benefit Adjustments Compensation Actually Paid ($) ($) ($) ($) ($) ($) (a) (b) PEO 2022 6,596,575 (2,460,988) 3,671,919 — — 7,807,506 2021 5,594,739 (2,461,055) 1,160,782 — — 4,294,466 2020 7,837,411 (2,255,592) 4,989,835 — — 10,571,654 Average of non-PEO NEOs 2022 1,547,874 (388,384) 448,185 — — 1,607,675 2021 1,188,098 (381,514) 123,729 — — 930,313 2020 1,435,144 (328,545) 720,611 4,952 (4,952) 1,827,210 (a) Stock award adjustments for each applicable year are further detailed in the table below. (b) Amounts deducted or added in calculating the pension benefit adjustments are further detailed in the table below. Year Year End Fair Value of Outstanding and Unvested Stock Awards Granted in the Year Year over Year Change in Fair Value of Outstanding and Unvested Stock Awards Year over Year Change in Fair Value of Stock Awards Granted in Prior Years that Vested in the Year Total Stock Award Adjustments ($) ($) ($) ($) PEO 2022 2,869,882 842,241 (40,204) 3,671,919 2021 2,498,710 (1,248,122) (89,806) 1,160,782 2020 3,626,488 1,514,753 (151,406) 4,989,835 Average of non-PEO NEOs 2022 340,124 113,647 (5,586) 448,185 2021 327,348 (190,357) (13,262) 123,729 2020 530,638 224,498 (34,525) 720,611 Year Service Cost Prior Service Cost Total Pension Benefit Adjustments ($) ($) ($) PEO 2022 $ — $ — $ — 2021 $ — $ — $ — 2020 $ — $ — $ — Average of non-PEO NEOs 2022 $ — $ — $ — 2021 $ — $ — $ — 2020 $ — $ — $ (4,952) | | |
| Non-PEO NEO Average Total Compensation Amount | $ 1,547,874 | 1,188,098 | 1,435,144 |
| Non-PEO NEO Average Compensation Actually Paid Amount | $ 1,607,675 | 930,313 | 1,827,210 |
| Adjustment to Non-PEO NEO Compensation Footnote [Text Block] | Compensation actually paid to our PEO and the average of all non-PEO NEOs is calculated in accordance with Item 402(v) of Regulation S-K. The dollar amounts do not reflect the actual amount of compensation earned by or paid to our PEO and the other NEOs during the applicable year. In accordance with Item 402(v) of Regulation S-K, the following adjustments were made to the amounts reported in the “Stock Awards” and “Change in Pension Value and Non-Qualified Deferred Compensation Earnings” columns in the “Summary Compensation Table” in each year’s respective proxy statement to determine the compensation actually paid. Year Reported Summary Compensation Table Total Reported Value of Stock Awards Stock Award Adjustments Reported Change in the Actuarial Present Value of Pension Benefits Pension Benefit Adjustments Compensation Actually Paid ($) ($) ($) ($) ($) ($) (a) (b) PEO 2022 6,596,575 (2,460,988) 3,671,919 — — 7,807,506 2021 5,594,739 (2,461,055) 1,160,782 — — 4,294,466 2020 7,837,411 (2,255,592) 4,989,835 — — 10,571,654 Average of non-PEO NEOs 2022 1,547,874 (388,384) 448,185 — — 1,607,675 2021 1,188,098 (381,514) 123,729 — — 930,313 2020 1,435,144 (328,545) 720,611 4,952 (4,952) 1,827,210 (a) Stock award adjustments for each applicable year are further detailed in the table below. (b) Amounts deducted or added in calculating the pension benefit adjustments are further detailed in the table below. Year Year End Fair Value of Outstanding and Unvested Stock Awards Granted in the Year Year over Year Change in Fair Value of Outstanding and Unvested Stock Awards Year over Year Change in Fair Value of Stock Awards Granted in Prior Years that Vested in the Year Total Stock Award Adjustments ($) ($) ($) ($) PEO 2022 2,869,882 842,241 (40,204) 3,671,919 2021 2,498,710 (1,248,122) (89,806) 1,160,782 2020 3,626,488 1,514,753 (151,406) 4,989,835 Average of non-PEO NEOs 2022 340,124 113,647 (5,586) 448,185 2021 327,348 (190,357) (13,262) 123,729 2020 530,638 224,498 (34,525) 720,611 Year Service Cost Prior Service Cost Total Pension Benefit Adjustments ($) ($) ($) PEO 2022 $ — $ — $ — 2021 $ — $ — $ — 2020 $ — $ — $ — Average of non-PEO NEOs 2022 $ — $ — $ — 2021 $ — $ — $ — 2020 $ — $ — $ (4,952) | | |
| Tabular List [Table Text Block] | Most Important Performance Measures Listed below are the financial and non-financial performance measures that represent the most important performance measures used to link compensation actually paid to our PEO and non-PEO NEOs, for 2022, to the Company’s performance: Most Important Incentive EPS Earnings Growth FFO/Debt Ratio Reliability | | |
| Total Shareholder Return Amount | $ 105 | 105 | 95 |
| Peer Group Total Shareholder Return Amount | 115 | 115 | 99 |
| Net Income (Loss) | $ 185,180,000 | $ 211,847,000 | $ 187,316,000 |
| Company Selected Measure Amount | $ / shares | 2.69 | 2.45 | 2.28 |
| Additional 402(v) Disclosure [Text Block] | Under rules issued pursuant to the Dodd-Frank Act, PNM Resources is providing the following information about the relationships between executive compensation actually paid and certain measures of financial performance of the Company. SEC rules prescribed the disclosure included in this section, and the information does not necessarily align with how the Company or the Compensation and HC Committee view the link between the Company’s performance and its NEOs’ pay. See Executive Compensation—Compensation Discussion and Analysis beginning on page 44 for additional information about our pay for performance and how the Company aligns executive compensation with its performance. Descriptions of Relationships of Information Presented in the Pay Versus Performance Table Compensation Actually Paid and TSR Compensation actually paid is generally aligned with the Company’s cumulative TSR over the period presented because a significant portion of the compensation actually paid comprises equity-based compensation. Compensation Actually Paid and Net Earnings Although the Company does not use net earnings as a performance measure in the overall executive compensation program, net earnings is similar to Incentive EPS, which the Company uses to determine awards under the AIP. Compensation Actually Paid and Incentive EPS While the Company uses multiple financial and non-financial performance measures for the purpose of evaluating performance for the Company’s compensation programs, the Company has determined that Incentive EPS is the financial performance measure that represents the most important financial performance measure (that is not otherwise required to be disclosed in the table) used by the Company to link compensation actually paid to the NEOs, for the most recently completed year, to the Company’s performance. Particularly in 2021 and 2022, compensation actually paid was aligned with Incentive EPS. See the Elements of Executive Compensation section beginning on page 49 for more information regarding the above performance measures as they relate to our short-term and long-term incentive plans. | | |
| Earnings Per Share | $ / shares | $ 1.97 | | |
| Earning Per Share Attributable To Net Change In Unrealized Gains (Losses) On Investment Securities | $ / shares | 0.55 | | |
| Earnings Per Share Attributable To Federal Energy Regulatory Committee Ordered Time-Value Refunds | $ / shares | 0.07 | | |
| Earnings Per Share, Attributable To Regulatory Disallowances And Restructuring Costs | $ / shares | 0.02 | | |
| Earnings Per Share Attributable To Pension Expense Related To Previously Disposed Of Gas Distribution Business | $ / shares | 0.02 | | |
| Earnings Per Share Attributable To Merger | $ / shares | 0.02 | | |
| Earnings Per Share Attributable To San Juan Generating Station Retirement Income Tax Adjustment Expense | $ / shares | $ 0.04 | | |
| Measure [Axis]: 1 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Incentive EPS | | |
| Non-GAAP Measure Description [Text Block] | Represents the company-selected financial performance measure used to link compensation actually paid to our PEO and non-PEO NEOs, for the most recently completed fiscal year, to company performance. Incentive EPS is defined as corporate diluted earnings per share, excluding certain terms that do not factor into ongoing earnings. For 2022, Incentive EPS of $2.69 equals net earnings attributable to PNMR per common stock share (as reported in the Company’s Form 10-K for the fiscal year ended December 31, 2022) of $1.97 adjusted to exclude: (1) $0.55 per share attributable to the net change in unrealized gains and losses on investment securities: (2) $0.07 per share attributable to Federal Energy Regulatory Committee ordered time-value refunds; (3) $0.02 per share attributable to regulatory disallowances and restructuring costs; (4) $0.02 per share attributable to pension expense related to previously disposed of gas distribution business; (5) $0.02 per share attributable to Merger related costs; and (6) $0.04 per share attributable to San Juan Generating Station retirement income tax adjustments. | | |
| Measure [Axis]: 2 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Earnings Growth | | |
| Measure [Axis]: 3 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | FFO/Debt Ratio | | |
| Measure [Axis]: 4 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Reliability | | |
| PEO [Member] | Equity Awards, Fair Value [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | $ (2,460,988) | $ (2,461,055) | $ (2,255,592) |
| PEO [Member] | Equity Awards, Adjustment [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 3,671,919 | 1,160,782 | 4,989,835 |
| PEO [Member] | Pension Benefits, Change In The Actuarial Present Value [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 0 | 0 | 0 |
| PEO [Member] | Pension Benefits, Adjustments [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 0 | 0 | 0 |
| PEO [Member] | Equity Awards Fair Value Of Outstanding And Unvested, Granted In Year [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount, Equity Awards | 2,869,882 | 2,498,710 | 3,626,488 |
| PEO [Member] | Equity Awards, Year Over Year Change In Value Of Outstanding And Unvested Awards [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount, Equity Awards | 842,241 | (1,248,122) | 1,514,753 |
| PEO [Member] | Equity Awards, Fair Value Of Awards Granted In Prior Years, Vested [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount, Equity Awards | (40,204) | (89,806) | (151,406) |
| PEO [Member] | Pension Benefit Adjustments [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 0 | 0 | 0 |
| Non-PEO NEO [Member] | Equity Awards, Fair Value [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (388,384) | (381,514) | (328,545) |
| Non-PEO NEO [Member] | Equity Awards, Adjustment [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 448,185 | 123,729 | 720,611 |
| Non-PEO NEO [Member] | Pension Benefits, Change In The Actuarial Present Value [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 0 | 0 | 4,952 |
| Non-PEO NEO [Member] | Pension Benefits, Adjustments [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 0 | 0 | (4,952) |
| Non-PEO NEO [Member] | Equity Awards Fair Value Of Outstanding And Unvested, Granted In Year [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount, Equity Awards | 340,124 | 327,348 | 530,638 |
| Non-PEO NEO [Member] | Equity Awards, Year Over Year Change In Value Of Outstanding And Unvested Awards [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount, Equity Awards | 113,647 | (190,357) | 224,498 |
| Non-PEO NEO [Member] | Equity Awards, Fair Value Of Awards Granted In Prior Years, Vested [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount, Equity Awards | (5,586) | (13,262) | (34,525) |
| Non-PEO NEO [Member] | Pension Benefit Adjustments [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | $ 0 | $ 0 | $ (4,952) |
