Income Taxes (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013
Income Tax Disclosure [Abstract]
Deferred Tax Assets, Operating Loss Carryforwards, State and Local, Decrease	$ 1.5

Deferred Tax Assets, Operating Loss Carryforwards, State and Local, Decrease

No definition available.

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Namespace Prefix:	pnm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant