Discloses entity portion of the fuel, operating, and maintenance expenses for the period.

No definition available.

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- Definition

The total period end amount of plant in service net of accumulated depreciation for the utility's share of jointly owned electricity generation plant.

+ References

No definition available.

+ Details

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- Definition

The total operating capacity of each of the units in the jointly owned utility plant.

+ References

No definition available.

+ Details

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- Definition

A jointly owned utility plant's share of MGE's net generating capability.

+ References

No definition available.

+ Details

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- Definition

A jointly owned utility plant's share of MGE's net generating capability capacity.

+ References

No definition available.

+ Details

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- Definition

Number of operating units in the jointly owned utility plant.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

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.

+ References

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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Period Type:	instant

- Definition

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

+ 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

+ 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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Data Type:	xbrli:stringItemType
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Period Type:	duration

- Definition

The total period end amount of plant in service and construction in progress net of accumulated depreciation for the utility's share of jointly owned electricity generation plant.

+ References

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

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

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

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- Details

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- Details

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Joint Plant Ownership (Details) $ in Thousands	12 Months Ended
Joint Plant Ownership (Details) $ in Thousands	Dec. 31, 2016 USD ($) operatingunit MW	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jan. 01, 2017
Jointly Owned Utility Plant Interests [Line Items]
Assets held for sale	$ 14,813	$ 0
MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Assets held for sale	14,813	0
Columbia Units [Member]
Jointly Owned Plants, Net Plant Ownership [Abstract]
Plant	270,898	273,762
Accumulated depreciation	(81,935)	(84,864)
Property, plant, and equipment, net	188,963	188,898
Construction work in progress	21,120	17,110
Total property, plant, and equipment	$ 210,083	206,008
Columbia Units [Member] \| MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, proportion of total net summer generating capability	30.00%
Jointly owned utility plant, plant capacity (in MW) \| MW	225
Jointly owned utility plant, ownership interest	22.00%
Assets held for sale	$ 14,800
Jointly owned utility plant, fuel, operating, and maintenance expense	39,500	38,200	$ 28,100
Columbia Units [Member] \| MGE [Member] \| Subsequent Event [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership interest				20.40%
Elm Road Units [Member] \| MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, fuel, operating, and maintenance expense	$ 21,200	20,900	20,300
Elm Road Units [Member] \| MGE Power Elm Road [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, proportion of total net summer generating capability	14.00%
Jointly owned utility plant, proportion of total net summer generating capability, plant capacity (in MW) \| MW	106
Jointly owned utility plant, number of operating units \| operatingunit	2
Jointly Owned Plants, Net Plant Ownership [Abstract]
Plant	$ 204,292	202,326
Accumulated depreciation	(28,790)	(24,422)
Property, plant, and equipment, net	175,502	177,904
Construction work in progress	3,241	2,400
Total property, plant, and equipment	$ 178,743	180,304
Elm Road Unit 1 [Member] \| MGE Power Elm Road [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, plant capacity (in MW) \| MW	615
Jointly owned utility plant, ownership interest	8.33%
Elm Road Unit 2 [Member] \| MGE Power Elm Road [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, plant capacity (in MW) \| MW	615
Jointly owned utility plant, ownership interest	8.33%
West Campus [Member] \| UW [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership interest	45.00%
Jointly owned utility plant, fuel, operating, and maintenance expense	$ 5,500	3,700	$ 2,800
West Campus [Member] \| MGE Power West Campus [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership interest	55.00%
Jointly Owned Plants, Net Plant Ownership [Abstract]
Plant	$ 111,330	111,141
Accumulated depreciation	(29,742)	(26,738)
Property, plant, and equipment, net	81,588	84,403
Construction work in progress	1,009	113
Total property, plant, and equipment	$ 82,597	$ 84,516