Pension and Other Postretirement Benefits APBO, PBO, Fair Value of Plan Assets, and Funded Status of the Plans (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Non-current liability	$ 110,738	$ 80,046
Public Service Company of New Mexico [Member] \| Pension Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation at beginning of year	599,537	675,549
Service cost	0	0	0
Interest cost	30,163	28,142	32,232
Plan amendment	0	(6,346)
Actuarial (gain) loss	72,524	(56,533)
Benefits paid	(44,667)	(41,275)
Benefit Obligation at end of year	657,557	599,537	675,549
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	556,353	518,095
Actual return on plan assets	76,223	19,533
Employer contributions	0	60,000
Benefits paid	(44,667)	(41,275)
Fair value of plan assets at end of year	587,909	556,353	518,095
Funded status – asset (liability) for pension benefits	(69,648)	(43,184)
Public Service Company of New Mexico [Member] \| Other Postretirement Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation at beginning of year	92,165	99,613
Service cost	181	260	217
Interest cost	4,630	4,113	5,293
Participant contributions	(2,582)	(2,537)
Actuarial (gain) loss	4,455	(4,566)
Benefits paid	(8,838)	(9,792)
Benefit Obligation at end of year	95,175	92,165	99,613
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	73,565	64,464
Actual return on plan assets	7,334	12,780
Employer contributions	3,532	3,576
Participant contributions	2,582	2,537
Benefits paid	(8,838)	(9,792)
Fair value of plan assets at end of year	78,175	73,565	64,464
Funded status – asset (liability) for pension benefits	(17,000)	(18,600)
Public Service Company of New Mexico [Member] \| Executive Retirement Program [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation at beginning of year	16,363	17,467
Service cost	0	0	0
Interest cost	822	720	876
Actuarial (gain) loss	2,040	(330)
Benefits paid	(1,495)	(1,494)
Benefit Obligation at end of year	17,730	16,363	17,467
Less current liability	1,528	1,536
Non-current liability	16,202	14,827
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Benefits paid	(1,495)	(1,494)
Texas-New Mexico Power Company [Member] \| Pension Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation at beginning of year	66,159	76,640
Service cost	0	0	0
Interest cost	3,193	3,087	3,635
Plan amendment	0	0
Actuarial (gain) loss	8,466	(7,820)
Benefits paid	(5,513)	(5,748)
Benefit Obligation at end of year	72,305	66,159	76,640
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	66,118	66,540
Actual return on plan assets	8,572	4,326
Employer contributions	0	1,000
Benefits paid	(5,513)	(5,748)
Fair value of plan assets at end of year	69,177	66,118	66,540
Funded status – asset (liability) for pension benefits	(3,128)	(41)
Texas-New Mexico Power Company [Member] \| Other Postretirement Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation at beginning of year	12,266	13,678
Service cost	237	299	244
Interest cost	619	566	624
Participant contributions	(366)	(373)
Actuarial (gain) loss	1,639	(1,080)
Benefits paid	(1,057)	(1,570)
Benefit Obligation at end of year	14,070	12,266	13,678
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	9,601	8,643
Actual return on plan assets	841	1,813
Employer contributions	343	342
Participant contributions	366	373
Benefits paid	(1,057)	(1,570)
Fair value of plan assets at end of year	10,094	9,601	8,643
Funded status – asset (liability) for pension benefits	(3,976)	(2,665)
Texas-New Mexico Power Company [Member] \| Executive Retirement Program [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation at beginning of year	823	902
Service cost	0	0	0
Interest cost	39	36	45
Actuarial (gain) loss	110	(21)
Benefits paid	(94)	(94)
Benefit Obligation at end of year	878	823	902
Less current liability	94	94
Non-current liability	784	729
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Benefits paid	$ (94)	$ (94)

The difference between fair value of plan assets at the end of the period and the fair value at the beginning of the period, adjusted for contributions and payments of benefits during the period, and after adjusting for taxes and other expenses, as applicable.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Actual Return on Plan Assets (Component of Net Periodic Postretirement Benefit Cost)

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-Glossary Actual Return on Plan Assets (Component of Net Periodic Pension Cost)

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Amount of gain (loss) related to change in benefit obligation resulting from changes in actuarial assumptions, for example, but not limited to, interest, mortality, employee turnover, salary, and temporary deviation from the substantive plan.

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1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date.

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-Glossary Accumulated Postretirement Benefit Obligation

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The amount of payments made for which participants are entitled under a pension plan, including pension benefits, death benefits, and benefits due on termination of employment. Also includes payments made under a postretirement benefit plan, including prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. This item represents a periodic decrease to the plan obligations and a decrease to plan assets.

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The increase in the fair value of plan assets from contributions made by the employer.

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The amount of contributions made by plan participants. This item represents a periodic increase to the plan obligation and an increase to plan assets.

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Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

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The funded status is measured as the difference between the fair value of plan assets and the benefit obligation. Will normally be the same as the net Defined Benefit Plan, Amounts Recognized in Balance Sheet, Total.

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The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.

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The amount of increase or decrease due to a change in the terms of an existing plan or the initiation of a new plan. A plan amendment may increase or decrease benefits, including those attributed to years of service already rendered.

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The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.

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For a classified balance sheet, the amount recognized in balance sheet as a current liability associated with an underfunded defined benefit plan.

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-Glossary Current Liabilities

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This represents the noncurrent liability for underfunded plans recognized in the balance sheet that is associated with the defined benefit pension plans and other postretirement defined benefit plans.

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