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Utility Plant Intangible Assets Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 1997	Jan. 08, 2020
Finite-Lived Intangible Assets [Line Items]
Intangible assets	$ 35,167	$ 33,424
Purchase premium customer relationships	13,400	13,400
Amortization of Intangible Assets	1,401	745	$ 647
Future Amortization of Intangible Assets
2021	1,401
2022	1,401
2023	1,401
2024	1,401
2025	1,401
Thereafter	1,401
Concession fees
Finite-Lived Intangible Assets [Line Items]
Intangible assets	6,800	6,800			$ 5,000
Other intangibles
Finite-Lived Intangible Assets [Line Items]
Intangible assets	14,967	$ 13,224
Service Agreements
Finite-Lived Intangible Assets [Line Items]
Intangible assets	3,999
Useful life of intangible assets				25 years
Infrastructure
Finite-Lived Intangible Assets [Line Items]
Intangible assets	5,984
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets	1,400
Contractual Rights
Finite-Lived Intangible Assets [Line Items]
Intangible assets	$ 1,040
Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life of intangible assets	5 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life of intangible assets	70 years

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- Definition

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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Gross carrying amount before accumulated amortization as of the balance sheet date to an asset acquired in a business combination representing a favorable existing relationship with customers having a finite beneficial life.

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Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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