SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Utility Plant (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Depreciable plant and equipment
Equipment	$ 3,645,770	$ 3,235,415
Office buildings and other structures	$ 27,567	24,854
Office Buildings and other structures, useful life	50 years
Minimum
Depreciable plant and equipment
Equipment, useful life	5 years
Transmission and distribution plant, useful life	40 years
Maximum
Depreciable plant and equipment
Equipment, useful life	50 years
Transmission and distribution plant, useful life	65 years
Utility Plant
Depreciable plant and equipment
Equipment	$ 785,578	726,475
Office buildings and other structures	305,791	281,462
Transmission and distribution plant	2,554,401	2,227,478
Total	$ 3,645,770	$ 3,235,415

Period end amount of property, plant and equipment and Office buildings and other structures owned by public utility.

No definition available.

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- Definition

Useful life of assets common to business units owned by public utility, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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- Definition

Period end book value of equipment owned (but not classified elsewhere) by the public utility.

+ References

No definition available.

+ Details

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- Definition

Useful life of other equipment owned by public utility, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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- Definition

Period end book value of other property, plant and equipment (PPE) owned (but not classified elsewhere) by the public utility.

+ References

No definition available.

+ Details

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- Definition

Period end amount of property, plant and equipment (PPE) related to transmission and distribution owned by public utility.

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No definition available.

+ Details

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- Definition

Useful life of utility transmission equipment owned by public utility, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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