Jointly-owned Plant Schedule of Jointly-owned plant (Details) $ in Millions	Dec. 31, 2022 USD ($)
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 781
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	490
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	12
Colstrip [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	571
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	421
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	0
Pelton/Round Butte Member
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	210
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	69
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 12

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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 360
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 10.C)
-URI https://asc.fasb.org/extlink&oid=122136288&loc=d3e659983-123033

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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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- Definition

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

+ References

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- Definition

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

+ References

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