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Segment Information - Narrative (Details) - Adjustments for New Accounting Pronouncement [Member] $ in Millions	9 Months Ended
	Sep. 30, 2015 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Previously reported amounts reclassified	$ 40.3
Public Service Company of New Mexico [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Previously reported amounts reclassified	22.1
Texas-New Mexico Power Company [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Previously reported amounts reclassified	$ 10.4

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

The amount of a reclassification adjustment made to prior period financial statement amounts.

+ References

No definition available.

+ Details

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- Details

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- Details

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X

- Details

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