Pension and Other Postretirement Benefits Components of Net Periodic Benefit Cost (Income) Recognized (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Public Service Company of New Mexico [Member] \| Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 0	$ 0	$ 0
Interest cost	30,163	28,142	32,232
Expected return on plan assets	(38,044)	(41,930)	(41,301)
Amortization of net (gain) loss	13,020	14,840	10,516
Amortization of prior service cost (credit)	(965)	76	317
Net periodic benefit cost	4,174	1,128	1,764
Public Service Company of New Mexico [Member] \| Executive Retirement Program [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0	0	0
Interest cost	822	720	876
Amortization of net (gain) loss	210	232	83
Amortization of prior service cost (credit)	0	0	0
Net periodic benefit cost	1,032	952	959
Public Service Company of New Mexico [Member] \| Other Postretirement Benefits [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	181	260	217
Interest cost	4,630	4,113	5,293
Expected return on plan assets	(5,638)	(5,043)	(4,901)
Amortization of net (gain) loss	2,225	4,242	3,888
Amortization of prior service cost (credit)	(1,343)	(1,343)	(1,343)
Net periodic benefit cost	55	2,229	3,154
Texas-New Mexico Power Company [Member] \| Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0	0	0
Interest cost	3,193	3,087	3,635
Expected return on plan assets	(4,526)	(4,849)	(5,324)
Amortization of net (gain) loss	665	1,049	462
Amortization of prior service cost (credit)	0	0	0
Net periodic benefit cost	(668)	(713)	(1,227)
Texas-New Mexico Power Company [Member] \| Executive Retirement Program [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0	0	0
Interest cost	39	36	45
Amortization of net (gain) loss	0	0	0
Amortization of prior service cost (credit)	0	0	0
Net periodic benefit cost	39	36	45
Texas-New Mexico Power Company [Member] \| Other Postretirement Benefits [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	237	299	244
Interest cost	619	566	624
Expected return on plan assets	(534)	(503)	(516)
Amortization of net (gain) loss	(122)	0	(209)
Amortization of prior service cost (credit)	32	57	57
Net periodic benefit cost	$ 232	$ 419	$ 200

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

+ Details

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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

-Topic 715

-SubTopic 30

-Glossary Expected Return on Plan Assets

-URI http://asc.fasb.org/extlink&oid=6512136

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 60

-Glossary Expected Return on Plan Assets

-URI http://asc.fasb.org/extlink&oid=6512171

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (h)(3)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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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.

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+ Details

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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.

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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

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (h)(1)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Service Cost (Component of Net Periodic Pension Cost)

-URI http://asc.fasb.org/extlink&oid=6525008

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

+ Details

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