Fair Value of Derivative and Other Financial Instruments - Derivative Balance Sheet Information (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Current assets	$ 9,342,000us-gaap_DerivativeAssetsCurrent	$ 11,232,000us-gaap_DerivativeAssetsCurrent
Commodity derivative instruments, Current liabilities	(1,235,000)us-gaap_DerivativeLiabilitiesCurrent	(1,209,000)us-gaap_DerivativeLiabilitiesCurrent
Commodity derivative instruments, Long-term liabilities	(277,000)us-gaap_DerivativeLiabilitiesNoncurrent	(477,000)us-gaap_DerivativeLiabilitiesNoncurrent
Assets, Current	503,721,000us-gaap_AssetsCurrent	432,817,000us-gaap_AssetsCurrent
PNMR and PNM [Member]
Derivatives, Fair Value [Line Items]
Derivative, Collateral, Right to Reclaim Cash	0	0
Margin Deposit Assets	2,800,000	3,800,000
Derivative, Collateral, Obligation to Return Cash	200,000	200,000
Fair Value Hedging [Member] \| Commodity Contract [Member] \| PNMR and PNM [Member]
Derivatives, Fair Value [Line Items]
Current assets	9,342,000	11,232,000
Deferred charges	0	0
Commodity derivative instruments, Assets	9,342,000	11,232,000
Commodity derivative instruments, Current liabilities	(1,235,000)	(1,209,000)
Commodity derivative instruments, Long-term liabilities	(277,000)	(477,000)
Commodity derivative instruments, Liabilities	(1,512,000)	(1,686,000)
Commodity derivative instruments, Net	7,830,000	9,546,000
Fuel and Purchased Power Adjustment Clause [Member] \| Fair Value Hedging [Member] \| Commodity Contract [Member] \| Public Service Company of New Mexico [Member] \| Maximum [Member]
Derivatives, Fair Value [Line Items]
Assets, Current	100,000
Palo Verde Nuclear Generating Station [Member] \| Fair Value Hedging [Member] \| Commodity Contract [Member] \| PNMR and PNM [Member]
Derivatives, Fair Value [Line Items]
Current assets	$ 2,200,000	$ 3,000,000

Sum of the carrying amounts as of the balance sheet date of all assets that are expected to be realized in cash, sold, or consumed within one year (or the normal operating cycle, if longer). Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

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Amount of obligation to return cash collateral under master netting arrangements that have not been offset against derivative assets.

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The amount of cash or securities placed with a broker or counterparty as security for a trading or derivatives securities position which was partially obtained with funds provided by the broker dealer.

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