Fair Value of Derivative and Other Financial Instruments - Overview and Commodity Derivatives (Details) - PNM - Designated as Hedging Instrument - Commodity derivatives - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Other current assets	$ 1,097	$ 1,089
Other deferred charges	729	1,507
Derivative asset	1,826	2,596
Other current liabilities	(1,097)	(1,089)
Other deferred credits	(729)	(1,507)
Derivative liability	(1,826)	(2,596)
Net	$ 0	$ 0

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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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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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled after one year or the normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

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