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Pension and Other Postretirement Benefit Plans - Schedule of Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2023 | Sep. 30, 2022
PNM | Pension Plan |  |  |  |
Components of Net Periodic Benefit Cost |  |  |  |
Service cost | $ 0 | $ 0 | $ 0 | $ 0
Interest cost | 5,913 | 4,215 | 17,740 | 12,643
Expected return on plan assets | (7,299) | (7,140) | (21,897) | (21,422)
Amortization of net loss | 2,646 | 3,948 | 7,937 | 11,846
Amortization of prior service cost | 0 | 0 | 0 | 0
Net Periodic Benefit Cost (Income) | 1,260 | 1,023 | 3,780 | 3,067
PNM | OPEB Plan |  |  |  |
Components of Net Periodic Benefit Cost |  |  |  |
Service cost | 0 | 2 | 0 | 6
Interest cost | 675 | 479 | 2,027 | 1,437
Expected return on plan assets | (1,242) | (1,088) | (3,727) | (3,264)
Amortization of net loss | 0 | 0 | 0 | 0
Amortization of prior service cost | 0 | 0 | 0 | 0
Net Periodic Benefit Cost (Income) | (567) | (607) | (1,700) | (1,821)
PNM | Executive Retirement Program |  |  |  |
Components of Net Periodic Benefit Cost |  |  |  |
Service cost | 0 | 0 | 0 | 0
Interest cost | 135 | 90 | 405 | 270
Expected return on plan assets | 0 | 0 | 0 | 0
Amortization of net loss | 38 | 81 | 114 | 245
Amortization of prior service cost | 0 | 0 | 0 | 0
Net Periodic Benefit Cost (Income) | 173 | 171 | 519 | 515
Texas-New Mexico Power Company | Pension Plan |  |  |  |
Components of Net Periodic Benefit Cost |  |  |  |
Service cost | 0 | 0 | 0 | 0
Interest cost | 601 | 430 | 1,802 | 1,290
Expected return on plan assets | (674) | (618) | (2,023) | (1,854)
Amortization of net loss | 110 | 233 | 329 | 699
Amortization of prior service cost | 0 | 0 | 0 | 0
Net Periodic Benefit Cost (Income) | 37 | 45 | 108 | 135
Texas-New Mexico Power Company | OPEB Plan |  |  |  |
Components of Net Periodic Benefit Cost |  |  |  |
Service cost | 5 | 9 | 16 | 27
Interest cost | 106 | 77 | 319 | 231
Expected return on plan assets | (120) | (104) | (361) | (312)
Amortization of net loss | (190) | (130) | (570) | (390)
Amortization of prior service cost | 0 | 0 | 0 | 0
Net Periodic Benefit Cost (Income) | (199) | (148) | (596) | (444)
Texas-New Mexico Power Company | Executive Retirement Program |  |  |  |
Components of Net Periodic Benefit Cost |  |  |  |
Service cost | 0 | 0 | 0 | 0
Interest cost | 3 | 2 | 9 | 8
Expected return on plan assets | 0 | 0 | 0 | 0
Amortization of net loss | 0 | 0 | 0 | 0
Amortization of prior service cost | 0 | 0 | 0 | 0
Net Periodic Benefit Cost (Income) | $ 3 | $ 2 | $ 9 | $ 8

X
- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480482/715-20-55-17 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 3A -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480535/715-20-45-3A Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 18 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480482/715-20-55-18 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (h)(4) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a)(4) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-6 + Details
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- Definition Amount of prior service cost (credit) recognized in net periodic benefit cost (credit) of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480482/715-20-55-17 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 3A -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480535/715-20-45-3A Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 18 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480482/715-20-55-18 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (h)(5) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a)(5) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-6 + Details
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- Definition Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480482/715-20-55-17 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 3A -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480535/715-20-45-3A Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 18 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480482/715-20-55-18 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (h)(3) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a)(3) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-6 + Details
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