Pension and Other Postretirement Benefits - Pre-Tax Information about Prior Service Cost and Net Actuarial (Gain) loss in AOCI (Details) $ in Thousands	12 Months Ended
Dec. 31, 2023 USD ($)
PNM \| Pension Plan
Net actuarial (gain) loss
Amounts in AOCI not yet recognized in net periodic benefit cost (income) at beginning of year	$ 110,345
Experience (gain) loss	(6,193)
Regulatory asset (liability) adjustment	4,629
Amortization recognized in net periodic benefit (income)	(4,713)
Amounts in AOCI not yet recognized in net periodic benefit cost at end of year	104,068
PNM \| Executive Retirement Program
Net actuarial (gain) loss
Amounts in AOCI not yet recognized in net periodic benefit cost (income) at beginning of year	995
Experience (gain) loss	411
Regulatory asset (liability) adjustment	(238)
Amortization recognized in net periodic benefit (income)	(64)
Amounts in AOCI not yet recognized in net periodic benefit cost at end of year	1,104
TNMP \| Pension Plan
Net actuarial (gain) loss
Amounts in AOCI not yet recognized in net periodic benefit cost (income) at beginning of year	0
Experience (gain) loss	1,005
Regulatory asset (liability) adjustment	(1,005)
Amortization recognized in net periodic benefit (income)	0
Amounts in AOCI not yet recognized in net periodic benefit cost at end of year	0
TNMP \| Executive Retirement Program
Net actuarial (gain) loss
Amounts in AOCI not yet recognized in net periodic benefit cost (income) at beginning of year	0
Experience (gain) loss	13
Regulatory asset (liability) adjustment	(13)
Amortization recognized in net periodic benefit (income)	0
Amounts in AOCI not yet recognized in net periodic benefit cost at end of year	$ 0

Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Actuarial (Gain) Loss, Regulatory Asset (Liability) Adjustment, before Tax

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- Definition

Amount, before tax, of accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

+ References

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- Definition

Amount, before tax, of gain (loss) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

+ References

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- Definition

Amount, before tax, of reclassification adjustment from accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan.

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