SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 4) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Depreciable plant and equipment
Equipment	$ 3,235,415	$ 2,950,424
Transmission and distribution plant	$ 24,854	$ 24,743
Office Buildings and other structures, Useful Lives	50 years
Provision for depreciation expressed as a percentage of the aggregate depreciable asset balances	2.96%	3.02%	3.00%
Minimum
Depreciable plant and equipment
Equipment, Useful Lives	5 years
Transmission and distribution plant, Useful Lives	40 years
Maximum
Depreciable plant and equipment
Equipment, Useful Lives	50 years
Transmission and distribution plant, Useful Lives	65 years
Utility Plant
Depreciable plant and equipment
Equipment	$ 726,475	$ 643,581
Office buildings and other structures	281,462	267,948
Transmission and distribution plant	2,227,478	2,038,895
Total	$ 3,235,415	$ 2,950,424

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.

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- Definition

Composite depreciation rate for public utility plants in service.

+ References

No definition available.

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- Definition

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

+ References

No definition available.

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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.

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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.

+ References

No definition available.

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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.

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