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Joint Plant Ownership (Details) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2015 USD ($) operatingunit MW | Dec. 31, 2014 USD ($) | Dec. 31, 2013 USD ($)
Columbia Units [Member] |  |  |
Jointly Owned Plants, Net Plant Ownership [Abstract] |  |  |
Plant | $ 273,762 | $ 268,597 |
Accumulated depreciation | (84,864) | (80,645) |
Property, plant, and equipment, net | 188,898 | 187,952 |
Construction work in progress | 17,110 | 6,941 |
Total property, plant, and equipment | $ 206,008 | 194,893 |
Columbia Units [Member] | MGE [Member] |  |  |
Jointly Owned Utility Plant Interests [Line Items] |  |  |
Jointly owned utility plant, proportion of total net summer generating capability | 31.00% |  |
Jointly owned utility plant, plant capacity (in MW) | MW | 242 |  |
Jointly owned utility plant, ownership interest | 22.00% |  |
Jointly owned utility plant, fuel, operating, and maintenance expense | $ 38,200 | 28,100 | $ 37,500
Elm Road Units [Member] | MGE [Member] |  |  |
Jointly Owned Utility Plant Interests [Line Items] |  |  |
Jointly owned utility plant, fuel, operating, and maintenance expense | $ 20,900 | 20,300 | 13,400
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 | $ 202,326 | 199,582 |
Accumulated depreciation | (24,422) | (19,962) |
Property, plant, and equipment, net | 177,904 | 179,620 |
Construction work in progress | 2,400 | 1,976 |
Total property, plant, and equipment | $ 180,304 | 181,596 |
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 | $ 3,700 | 2,800 | $ 4,900
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 | $ 111,141 | 111,453 |
Accumulated depreciation | (26,738) | (24,691) |
Property, plant, and equipment, net | $ 84,403 | $ 86,762 |

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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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