CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - TXNM ENERGY, INC. AND SUBSIDIARIES (Parenthetical) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Statement of Comprehensive Income [Abstract]
Net increase in unrealized holding gains arising during the period, income tax (expense) benefit	$ (7)	$ (36)	$ (24)	$ (164)
Reclassification adjustment for (gains) losses included in net earnings, income tax expense (benefit)	28	69	93	155
Pension liability adjustment, income tax expense (benefit)	(16)	(349)	(383)	(1,047)
Change in fair market value, income tax (expense) benefit	0	(242)	0	391
Reclassification adjustment for gains (losses) included in net earnings, income tax (expense) benefit	$ (12)	$ 0	$ (36)	$ 0

Amount, after reclassification adjustment, of tax (expense) benefit for (increase) decrease in accumulated other comprehensive income for defined benefit plan, attributable to parent.

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-Topic 810
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 19
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-Name Accounting Standards Codification
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-Paragraph 1A
-Subparagraph (c)(3)
-SubTopic 10
-Topic 810
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481203/810-10-50-1A

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Amount, before reclassification, of tax expense (benefit) for gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
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Amount of tax expense (benefit) for reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

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Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

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Amount, before adjustment, of tax expense (benefit) for unrealized holding gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). Excludes tax expense (benefit) for unrealized gain (loss) on investment in debt security measured at amortized cost (held-to-maturity) from transfer to available-for-sale.

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-Name Accounting Standards Codification
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