PROPERTY, PLANT AND EQUIPMENT - Jointly Owned Facilities (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Jointly Owned Utility Plant Interests [Line Items]
Electric Plant in Service	$ 932,875
Accumulated Depreciation	705,798
Construction Work In Progress	$ 2,137
Yampa
Jointly Owned Utility Plant Interests [Line Items]
Tri-State share (as a percent)	24.00%
Electric Plant in Service	$ 392,510
Accumulated Depreciation	358,839
Construction Work In Progress	$ 23
MBPP
Jointly Owned Utility Plant Interests [Line Items]
Tri-State share (as a percent)	28.50%
Electric Plant in Service	$ 540,365
Accumulated Depreciation	346,959
Construction Work In Progress	$ 2,114

The period end amount owned by the reporting utility of a jointly owned utility plant in service.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 980
-SubTopic 360
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 10.C)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479960/980-360-S99-1

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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.

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The period end amount of construction work in progress at a jointly owned electricity generation plant.

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- Definition

The period end amount of accumulated depreciation in a jointly owned electricity generation plant.

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- Definition

The proportionate share of interest (percent) in a jointly owned utility plant.

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