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Pension and Other Postretirement Benefit Plans - Schedule of Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands | 3 Months Ended
--- | ---
Mar. 31, 2024 | Mar. 31, 2023
PNM | Pension Plan |  |
Components of Net Periodic Benefit Cost |  |
Service cost | $ 0 | $ 0
Interest cost | 5,427 | 5,913
Expected return on plan assets | (7,757) | (7,299)
Amortization of net loss | 2,661 | 2,646
Amortization of prior service cost | 0 | 0
Net Periodic Benefit Cost (Income) | 331 | 1,260
PNM | OPEB Plan |  |
Components of Net Periodic Benefit Cost |  |
Service cost | 0 | 0
Interest cost | 597 | 676
Expected return on plan assets | (1,391) | (1,243)
Amortization of net loss | 0 | 0
Amortization of prior service cost | 0 | 0
Net Periodic Benefit Cost (Income) | (794) | (567)
PNM | Executive Retirement Program |  |
Components of Net Periodic Benefit Cost |  |
Service cost | 0 | 0
Interest cost | 124 | 135
Expected return on plan assets | 0 | 0
Amortization of net loss | 50 | 38
Amortization of prior service cost | 0 | 0
Net Periodic Benefit Cost (Income) | 174 | 173
Texas-New Mexico Power Company | Pension Plan |  |
Components of Net Periodic Benefit Cost |  |
Service cost | 0 | 0
Interest cost | 553 | 601
Expected return on plan assets | (687) | (674)
Amortization of net loss | 139 | 110
Amortization of prior service cost | 0 | 0
Net Periodic Benefit Cost (Income) | 5 | 37
Texas-New Mexico Power Company | OPEB Plan |  |
Components of Net Periodic Benefit Cost |  |
Service cost | 5 | 5
Interest cost | 96 | 106
Expected return on plan assets | (129) | (120)
Amortization of net loss | (161) | (190)
Amortization of prior service cost | 0 | 0
Net Periodic Benefit Cost (Income) | (189) | (199)
Texas-New Mexico Power Company | Executive Retirement Program |  |
Components of Net Periodic Benefit Cost |  |
Service cost | 0 | 0
Interest cost | 4 | 3
Expected return on plan assets | 0 | 0
Amortization of net loss | 0 | 0
Amortization of prior service cost | 0 | 0
Net Periodic Benefit Cost (Income) | $ 4 | $ 3

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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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