Amount of assets held-for-sale that are not part of a disposal group, expected to be sold within a year or the normal operating cycle, if longer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 15
-Paragraph 4
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=6390208&loc=d3e400-110220

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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=6500719&loc=d3e659983-123033

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Joint Plant Ownership (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Jan. 01, 2017	Dec. 31, 2016
Jointly Owned Utility Plant Interests [Line Items]
Assets held for sale	$ 2,338		$ 14,813
MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Assets held for sale	2,338		$ 14,813
Columbia Units [Member] \| MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share		20.40%	22.00%
Assets held for sale	$ 2,300		$ 14,800