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Stock-Based Compensation - Excess Tax Benefits (Details) - Accounting Standards Update 2016-09 - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Public Service Company of New Mexico |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Excess tax benefit from share-based compensation, operating activities | $ 279 | $ 559 | $ 1,007
Texas-New Mexico Power Company |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Excess tax benefit from share-based compensation, operating activities | 112 | 236 | 377
PNMR |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Excess tax benefit from share-based compensation, operating activities | $ 391 | $ 795 | $ 1,384

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- Definition Amount of cash outflow for realized tax benefit related to deductible compensation cost reported on the entity's tax return for equity instruments in excess of the compensation cost for those instruments recognized for financial reporting purposes. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 20 -Section 55 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=120383193&loc=d3e11374-113907 + Details
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