Property Plant and Equipment Property Plant and Equipment Joint Ownership (Details) $ in Millions	Dec. 31, 2019 USD ($)
Jointly Owned Utility Plant Interests [Line Items]
Plant in Service	$ 1,735.7
Accumulated Depreciation	626.7
CWIP	7.9
Electric Generation \| Sherco Unit 3
Jointly Owned Utility Plant Interests [Line Items]
Plant in Service	603.0
Accumulated Depreciation	426.3
CWIP	$ 3.8
Percent Owned	59.00%
Electric Generation \| Sherco Common Facilities Units 1, 2 and 3
Jointly Owned Utility Plant Interests [Line Items]
Plant in Service	$ 144.7
Accumulated Depreciation	102.7
CWIP	$ 1.9
Percent Owned	80.00%
Electric Generation \| Sherco Substation
Jointly Owned Utility Plant Interests [Line Items]
Plant in Service	$ 4.8
Accumulated Depreciation	3.5
CWIP	$ 0.0
Percent Owned	59.00%
Electric Transmission \| CapX2020
Jointly Owned Utility Plant Interests [Line Items]
Plant in Service	$ 972.5
Accumulated Depreciation	91.6
CWIP	$ 2.2
Percent Owned	51.00%
Electric Transmission \| Grand Meadow
Jointly Owned Utility Plant Interests [Line Items]
Plant in Service	$ 10.7
Accumulated Depreciation	2.6
CWIP	$ 0.0
Percent Owned	50.00%

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 http://asc.fasb.org/extlink&oid=115995737&loc=d3e659983-123033

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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.

+ References

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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.

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- Definition

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

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