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Pension and Other Postretirement Benefits - Assumed Health Care Cost Trend Rates and Impact of a One-Percentage-Point Change in Assumed Health Care Cost Trend Rates (Details) - Public Service Company of New Mexico - Other Postretirement Benefits | 12 Months Ended
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Dec. 31, 2021 | Dec. 31, 2020
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract] |  |
Health care cost trend rate assumed for next year | 6.00% | 6.25%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) | 4.75% | 5.00%
Year that the rate reaches the ultimate trend rate | 2027 | 2026

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- Definition Assumed rate, for next fiscal year, based on annual change in cost of health care cost benefits used to measure expected cost of benefits covered by defined benefit postretirement plan. Factors include, but are not limited to, estimate of health care inflation, change in health care utilization or delivery pattern, technological advances, and change in health status of participant. Excludes factors for change in composition of plan population by age and dependency status. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (l) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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- Definition Ultimate trend rate for health care cost for defined benefit postretirement plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (l) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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- Definition Year ultimate health care cost trend rate is expected to be reached, in YYYY format. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (l) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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