Joint Plant Ownership (Details) - MGE [Member] $ in Millions	Jul. 31, 2019 USD ($) MW	Jun. 30, 2019 USD ($) MW
Two Creeks Units [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership interest		33.00%
Jointly owned utility plant, plant capacity (in MW) \| MW		150
Projected Solar Farm Project Costs		$ 65.0
Public Utilities Property Plant And Equipment Construction Work In Progress		16.5
Badger Hollow Units [Member]
Jointly Owned Utility Plant Interests [Line Items]
Public Utilities Property Plant And Equipment Construction Work In Progress		$ 1.0
Badger Hollow Units [Member] \| Subsequent Event [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership interest	33.00%
Jointly owned utility plant, plant capacity (in MW) \| MW	150
Projected Solar Farm Project Costs	$ 65.0

The total operating capacity (in megawatts) of the jointly owned utility plant.

No definition available.

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- Definition

The Company's projected costs for the current solar projects.

+ References

No definition available.

+ Details

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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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- Definition

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

+ References

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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- Definition

Period end amount of construction work in progress in public utility.

+ References

No definition available.

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