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Summary of the Business and Significant Accounting Policies - Narrative (Details) | 12 Months Ended
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Dec. 31, 2023 USD ($) utility | Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($)
Accounting Policies Disclosures [Line Items] |  |  |
Payment defaults | $ 0 |  |
Net gains (losses) on debt securities | $ 4,008,000 | $ (33,392,000) | $ 8,554,000
PNMR |  |  |
Accounting Policies Disclosures [Line Items] |  |  |
Number of regulated utilities | utility | 2 |  |
Restricted cash | $ 0 | 0 |
PNM |  |  |
Accounting Policies Disclosures [Line Items] |  |  |
Restricted cash | 0 | 0 |
Allowance for funds used during construction, capitalized interest | $ 9,500,000 | $ 3,700,000 | $ 3,400,000
Allowance for funds used during construction, capitalized interest rate | 2.99% | 1.70% | 1.70%
Allowance for equity funds used during construction | $ 9,800,000 | $ 9,300,000 | $ 9,900,000
Allowance for funds used during construction, capitalized cost of equity rate | 3.24% | 4.26% | 4.94%
Net gains (losses) on debt securities | $ (19,100,000) | $ 25,800,000 | $ (700,000)
TNMP |  |  |
Accounting Policies Disclosures [Line Items] |  |  |
Restricted cash | 0 | 0 |
Allowance for funds used during construction, capitalized interest | $ 5,700,000 | $ 3,400,000 | $ 1,600,000
Allowance for funds used during construction, capitalized interest rate | 3.49% | 2.25% | 1.80%
Allowance for equity funds used during construction | $ 5,100,000 | $ 4,500,000 | $ 3,300,000
Allowance for funds used during construction, capitalized cost of equity rate | 3.17% | 2.99% | 3.67%

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- Definition Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), investment in debt security measured at amortized cost (held-to-maturity) and investment in debt security measured at fair value with change in fair value recognized in net income (trading). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(7)(c)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(9)(a)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(3)(d)(1)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483586/944-220-S99-1 + Details
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