Pension and Other Postretirement Benefit Plans (Details) - USD ($)	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Public Service Company of New Mexico [Member] \| Pension Plan [Member]
Components of Net Periodic Benefit Cost
Service cost	$ 0	$ 0
Interest cost	7,577,000	7,064,000
Expected return on plan assets	(8,854,000)	(9,831,000)
Amortization of net (gain) loss	3,455,000	3,705,000
Amortization of prior service cost	(241,000)	(241,000)
Net Periodic Benefit Cost (Income)	1,937,000	697,000
Contributions by employer		30,000,000
Total expected employer contributions for fiscal year	0
Total expected employer contributions for future fiscal years	$ 0
Public Service Company of New Mexico [Member] \| Pension Plan [Member] \| Minimum [Member]
Components of Net Periodic Benefit Cost
Assumptions used calculating net periodic benefit cost, discount rate	4.80%
Public Service Company of New Mexico [Member] \| Pension Plan [Member] \| Maximum [Member]
Components of Net Periodic Benefit Cost
Assumptions used calculating net periodic benefit cost, discount rate	5.70%
Public Service Company of New Mexico [Member] \| OPEB [Member]
Components of Net Periodic Benefit Cost
Service cost	$ 35,000	51,000
Interest cost	1,087,000	1,022,000
Expected return on plan assets	(1,371,000)	(1,403,000)
Amortization of net (gain) loss	286,000	491,000
Amortization of prior service cost	(7,000)	(160,000)
Net Periodic Benefit Cost (Income)	30,000	1,000
Contributions by employer	800,000	800,000
Total expected employer contributions for fiscal year	3,500,000
Total expected employer contributions for future fiscal years	14,000,000
Public Service Company of New Mexico [Member] \| Other Pension Plan [Member]
Components of Net Periodic Benefit Cost
Service cost	0	0
Interest cost	203,000	190,000
Expected return on plan assets	0	0
Amortization of net (gain) loss	64,000	81,000
Amortization of prior service cost	0	0
Net Periodic Benefit Cost (Income)	267,000	271,000
Contributions by employer	500,000	500,000
Total expected employer contributions for fiscal year	1,500,000
Total expected employer contributions for future fiscal years	5,900,000
Texas-New Mexico Power Company [Member] \| Pension Plan [Member]
Components of Net Periodic Benefit Cost
Service cost	0	0
Interest cost	826,000	761,000
Expected return on plan assets	(986,000)	(1,105,000)
Amortization of net (gain) loss	175,000	195,000
Amortization of prior service cost	0	0
Net Periodic Benefit Cost (Income)	15,000	(149,000)
Contributions by employer		0
Total expected employer contributions for fiscal year	0
Total expected employer contributions for future fiscal years	$ 0
Texas-New Mexico Power Company [Member] \| Pension Plan [Member] \| Minimum [Member]
Components of Net Periodic Benefit Cost
Assumptions used calculating net periodic benefit cost, discount rate	4.80%
Texas-New Mexico Power Company [Member] \| Pension Plan [Member] \| Maximum [Member]
Components of Net Periodic Benefit Cost
Assumptions used calculating net periodic benefit cost, discount rate	5.70%
Texas-New Mexico Power Company [Member] \| OPEB [Member]
Components of Net Periodic Benefit Cost
Service cost	$ 46,000	62,000
Interest cost	169,000	152,000
Expected return on plan assets	(122,000)	(130,000)
Amortization of net (gain) loss	(10,000)	0
Amortization of prior service cost	0	0
Net Periodic Benefit Cost (Income)	83,000	84,000
Contributions by employer	0	0
Total expected employer contributions for fiscal year	300,000
Total expected employer contributions for future fiscal years	1,400,000
Texas-New Mexico Power Company [Member] \| Other Pension Plan [Member]
Components of Net Periodic Benefit Cost
Service cost	0	0
Interest cost	10,000	9,000
Expected return on plan assets	0	0
Amortization of net (gain) loss	1,000	1,000
Amortization of prior service cost	0	0
Net Periodic Benefit Cost (Income)	11,000	10,000
Total expected employer contributions for fiscal year	100,000
Total expected employer contributions for future fiscal years	400,000
Texas-New Mexico Power Company [Member] \| Other Pension Plan [Member] \| Maximum [Member]
Components of Net Periodic Benefit Cost
Contributions by employer	$ 100,000	$ 100,000

Defined Benefit Plan, Estimated Future Employer Contributions in Year Two Through Year Five

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- Definition

Defined Benefit Plan Total Expected Employer Contributions for Fiscal Year

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No definition available.

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- Definition

The amount of gains or losses recognized in net periodic benefit cost.

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- Definition

The amount of the prior service cost or credit recognized in net periodic benefit cost relating to benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (h)(1)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Prior Service Cost
-URI http://asc.fasb.org/extlink&oid=49177896

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The interest rate used to adjust for the time value of money.

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- Definition

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

+ References

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- Definition

An amount calculated as a basis for determining the extent of delayed recognition of the effects of changes in the fair value of assets. The expected return on plan assets is determined based on the expected long-term rate of return on plan assets and the market-related value of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Expected Return on Plan Assets
-URI http://asc.fasb.org/extlink&oid=6512171

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-Publisher FASB
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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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- Definition

The total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (h)
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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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