Regulatory Assets and Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Regulatory Assets
Regulatory Assets, Current	$ 39,120	$ 44,993
Regulatory Assets, Noncurrent	555,577	482,155
Regulatory Liabilities
Regulatory Liability, Current	(15,173)	(125)
Regulatory liabilities, Noncurrent	(423,460)	(418,098)
Public Service Company of New Mexico [Member]
Regulatory Assets
Regulatory Assets, Current	36,490	44,480
Regulatory Assets, Noncurrent	431,956	352,387
Regulatory Assets	468,446	396,867
Regulatory Liabilities
Regulatory Liability, Current	(15,172)	(125)
Regulatory liabilities, Noncurrent	(379,841)	(373,703)
Regulatory Liabilities	(395,013)	(373,828)
Texas-New Mexico Power Company [Member]
Regulatory Assets
Regulatory Assets, Current	2,630	513
Regulatory Assets, Noncurrent	123,621	129,768
Regulatory Assets	126,251	130,281
Regulatory Liabilities
Regulatory liabilities, Noncurrent	(43,619)	(44,395)
Other [Member] \| Public Service Company of New Mexico [Member]
Regulatory Liabilities
Regulatory Liability, Current	(15,172)	(125)
Cost of removal [Member] \| Public Service Company of New Mexico [Member]
Regulatory Liabilities
Regulatory liabilities, Noncurrent	(257,396)	(250,778)
Cost of removal [Member] \| Texas-New Mexico Power Company [Member]
Regulatory Liabilities
Regulatory liabilities, Noncurrent	(31,115)	(32,786)
Deferred income taxes Member] \| Public Service Company of New Mexico [Member]
Regulatory Liabilities
Regulatory liabilities, Noncurrent	(49,723)	(45,323)
Deferred income taxes Member] \| Texas-New Mexico Power Company [Member]
Regulatory Liabilities
Regulatory liabilities, Noncurrent	(5,203)	(5,843)
Asset retirement obligations [Member] \| Public Service Company of New Mexico [Member]
Regulatory Liabilities
Regulatory liabilities, Noncurrent	(39,280)	(39,979)
Renewable energy tax benefits [Member] \| Public Service Company of New Mexico [Member]
Regulatory Liabilities
Regulatory liabilities, Noncurrent	(26,988)	(27,958)
Other [Member] \| Public Service Company of New Mexico [Member]
Regulatory Liabilities
Regulatory liabilities, Noncurrent	(6,454)	(9,665)
Other [Member] \| Texas-New Mexico Power Company [Member]
Regulatory Liabilities
Regulatory liabilities, Noncurrent	(7,301)	(5,766)
Other [Member] \| Public Service Company of New Mexico [Member]
Regulatory Assets
Regulatory Assets, Current	224	3,226
Other [Member] \| Texas-New Mexico Power Company [Member]
Regulatory Assets
Regulatory Assets, Current	2,630	513
Stranded costs [Member] \| Texas-New Mexico Power Company [Member]
Regulatory Assets
Regulatory Assets, Noncurrent	71,240	81,256
Coal mine reclamation costs [Member] \| Public Service Company of New Mexico [Member]
Regulatory Assets
Regulatory Assets, Noncurrent	46,065	51,985
Deferred income taxes Member] \| Public Service Company of New Mexico [Member]
Regulatory Assets
Regulatory Assets, Noncurrent	54,781	51,436
Deferred income taxes Member] \| Texas-New Mexico Power Company [Member]
Regulatory Assets
Regulatory Assets, Noncurrent	11,179	11,491
Loss on reacquired debt [Member] \| Public Service Company of New Mexico [Member]
Regulatory Assets
Regulatory Assets, Noncurrent	29,702	31,276
Loss on reacquired debt [Member] \| Texas-New Mexico Power Company [Member]
Regulatory Assets
Regulatory Assets, Noncurrent	1,711	2,852
Pension and OPEB [Member] \| Public Service Company of New Mexico [Member]
Regulatory Assets
Regulatory Assets, Noncurrent	254,351	208,033
Pension and OPEB [Member] \| Texas-New Mexico Power Company [Member]
Regulatory Assets
Regulatory Assets, Noncurrent	28,307	18,818
Fuel and purchased power adjustment clause [Member]
Regulatory Assets
Regulatory Assets, Current	22,200
Fuel and purchased power adjustment clause [Member] \| Public Service Company of New Mexico [Member]
Regulatory Assets
Regulatory Assets, Current	36,266	41,254
Regulatory Assets, Noncurrent	18,619	0
Renewable energy costs [Member] \| Public Service Company of New Mexico [Member]
Regulatory Assets
Regulatory Assets, Noncurrent	18,768	9,550
Hurricane recovery costs [Member] \| Texas-New Mexico Power Company [Member]
Regulatory Assets
Regulatory Assets, Noncurrent	4,572	9,210
Other [Member] \| Public Service Company of New Mexico [Member]
Regulatory Assets
Regulatory Assets, Noncurrent	9,670	107
Other [Member] \| Texas-New Mexico Power Company [Member]
Regulatory Assets
Regulatory Assets, Noncurrent	$ 6,612	$ 6,141

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The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 71

-Paragraph 9, 10

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 340

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

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- Definition

Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost.

+ References

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Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer.

+ References

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- Definition

The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 71

-Paragraph 11

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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The amount for the individual regulatory current liability as itemized in a table of regulatory current liabilities as of the end of the period.

+ References

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- Definition

The amount for the individual regulatory noncurrent liability as itemized in a table of regulatory noncurrent liabilities as of the end of the period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.24)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 71

-Paragraph 11

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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