Asset Retirement Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	$ 111,895	$ 104,170	$ 96,135
Liabilities incurred	0	0	0
Liabilities settled	(14)	(730)	0
Accretion expense	9,170	8,625	7,984
Revisions to estimated cash flows	6,468	(170)	51
Ending balance	127,519	111,895	104,170
Public Service Company of New Mexico [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	111,049	103,182	95,225
Liabilities incurred	0	0	0
Liabilities settled	(14)	(506)	0
Accretion expense	9,098	8,543	7,906
Revisions to estimated cash flows	6,468	(170)	51
Ending balance	126,601	111,049	103,182
Public Service Company of New Mexico [Member] \| Palo Verde Nuclear Generating Station [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Increase (decrease) to asset retirement obligation	6,100	1,000
Public Service Company of New Mexico [Member] \| San Juan Generating Station [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Increase (decrease) to asset retirement obligation	300	(1,200)
Texas-New Mexico Power Company [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	695	848	782
Liabilities incurred	0	0	0
Liabilities settled	0	(224)	0
Accretion expense	59	71	66
Revisions to estimated cash flows	0	0	0
Ending balance	$ 754	$ 695	$ 848

The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Asset Retirement Obligation
-URI http://asc.fasb.org/extlink&oid=6505190

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Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6392676&loc=d3e7480-110848

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Amount of asset retirement obligations incurred during the period.

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Amount of asset retirement obligations settled, or otherwise disposed of, during the period. This may include asset retirement obligations transferred to third parties associated with the sale of a long-lived asset.

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Amount of increase (decrease) in asset retirement obligations.

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Amount of increase (decrease) in the asset retirement obligation from changes in the amount or timing of the estimated cash flows associated with the settlement of the obligation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)(4)
-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 35
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6392603&loc=d3e7123-110846

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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