Income Tax [Line Items]

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Operating loss carryforward, Limitations on Use, Percent of Taxable income allowed to be carried forward indefinitely.

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- Definition

Period of Average Annual Book Income Before Taxes, In Years

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Tax year no longer subject to tax examination by the taxing authorities.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible alternative minimum tax credit carryforwards.

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- Definition

Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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- Definition

Amount of decrease in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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- Definition

Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

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Amount of interest expense for an underpayment of income taxes.

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Amount of increase (decrease) in unrecognized tax benefits attributable to uncertain tax positions taken in tax returns.

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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax [Line Items]
Period of Average Annual Book Income Before Taxes	3 years
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	$ 0	$ 8,855
Federal statutory tax rate	21.00%	21.00%	35.00%
Unrecognized Tax Benefits, Decrease Resulting from Current Period Tax Positions	$ 0	$ 200	$ 0
Unrecognized tax benefits that would impact effective tax rate	1,900
Unrecognized tax benefits, interest on income taxes expense (benefit)	200	600	200
Unrecognized tax benefits, income tax penalties and interest accrued	$ 1,400	1,200
Internal Revenue Service (IRS)
Income Tax [Line Items]
Operating loss carryforward, Limitations on Use, Percent	80.00%
State and Local Jurisdiction
Income Tax [Line Items]
Unrecognized Tax Benefits, Decrease Resulting from Current Period Tax Positions	$ 300
Tax credit taken \| ARIZONA
Income Tax [Line Items]
Unrecognized Tax Benefits, Period Increase (Decrease)	$ 300	$ 500	100
Earliest Tax Year \| TEXAS
Income Tax [Line Items]
Tax Year Closed	2007
Latest Tax Year \| Internal Revenue Service (IRS)
Income Tax [Line Items]
Tax Year Closed	2014
Latest Tax Year \| NEW MEXICO
Income Tax [Line Items]
Tax Year Closed	2014
Latest Tax Year \| TEXAS
Income Tax [Line Items]
Tax Year Closed	2011
Latest Tax Year \| ARIZONA
Income Tax [Line Items]
Tax Year Closed	2014
Electric Transmission and Distribution Equipment \| TEXAS
Income Tax [Line Items]
Unrecognized Tax Benefits, Period Increase (Decrease)	$ (400)		(1,200)
Depreciation \| TEXAS
Income Tax [Line Items]
Unrecognized Tax Benefits, Period Increase (Decrease)			$ 500