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Asset Retirement Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Asset Retirement Obligations [Line Items]
ARO liabilities related to nuclear decommissioning	81.00%
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	$ 146,679	$ 127,519	$ 111,895
Liabilities incurred(1)	0	1,854	0
Liabilities settled	(192)	(968)	(14)
Accretion expense	11,482	10,680	9,170
Revisions to estimated cash flows	705	7,594	6,468
Ending balance	158,674	146,679	127,519
Public Service Company of New Mexico
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	145,707	126,601	111,049
Liabilities incurred(1)	0	1,853	0
Liabilities settled	0	(944)	(14)
Accretion expense	11,402	10,603	9,098
Revisions to estimated cash flows	705	7,594	6,468
Ending balance	157,814	145,707	126,601
Texas-New Mexico Power Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	793	754	695
Liabilities incurred(1)	0	0	0
Liabilities settled	0	(24)	0
Accretion expense	67	63	59
Revisions to estimated cash flows	0	0	0
Ending balance	$ 860	$ 793	$ 754

X

- Definition

Asset Retirement Obligation, Liabilities Related to Nuclear Decommissioning

+ References

No definition available.

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- Definition

Asset Retirement Obligations [Line Items]

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- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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

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- Definition

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://fasb.org/us-gaap/role/ref/legacyRef
-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

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Amount of asset retirement obligations incurred during the period.

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-SubTopic 20
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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.

+ References

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- Definition

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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 35
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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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