Number of Megawatts being purchased under capacity and energy contract

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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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Total obligations incurred as part of normal operations that are expected to be paid during the following twelve months or within one business cycle, if longer.

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Amount of Net Income (Loss) attributable to noncontrolling interest.

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Variable Interest Entity: (Details) $ in Thousands		12 Months Ended
Variable Interest Entity: (Details) $ in Thousands	Apr. 14, 2016	Dec. 31, 2020 USD ($) MW	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Variable Interest Entity [Line Items]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage	49.90%
Net income attributable to noncontrolling interest		$ (15,155)	$ (14,012)	$ (14,220)
Current assets		493,291	473,184
Property, plant and equipment of variable interest entities, net		6,019,714	5,503,186
Current liabilities		696,533	811,294
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Current assets		13,604	13,350
Property, plant and equipment of variable interest entities, net		190,637	193,046
Current liabilities		5,318	6,013
Power Generation
Variable Interest Entity [Line Items]
Net income attributable to noncontrolling interest		(15,000)	(14,000)	$ (14,000)
Property, plant and equipment of variable interest entities, net		$ 367,016	$ 380,156
Pueblo Airport Generation \| Subsidiary of Common Parent
Variable Interest Entity [Line Items]
Electric Generation Capacity, Megawatts \| MW		200