XML 117 R95.htm IDEA: XBRL DOCUMENT
v3.3.1.900

Segment Information (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2015 | Sep. 30, 2015 | Jun. 30, 2015 | Mar. 31, 2015 | Dec. 31, 2014 | Sep. 30, 2014 | Jun. 30, 2014 | Mar. 31, 2014 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  | $ 130,973 | $ 140,795 | $ 122,126 | $ 170,134 | $ 145,707 |  | $ 135,135 | $ 128,765 | $ 210,245 | $ 564,028 | $ 619,852 |  | $ 590,887
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  | (44,225) | (40,695) |  | (38,838)
Other operating expenses |  |  |  |  |  |  |  |  |  |  | (395,548) | (441,059) |  | (424,062)
Operating Income (Loss) |  | 22,178 | 46,177 | 24,049 | 31,851 | 29,566 |  | 40,120 | 24,441 | 43,971 | 124,255 | 138,098 |  | 127,987
Other (deductions) income, net |  |  |  |  |  |  |  |  |  |  | 8,613 | 10,079 |  | 10,701
Interest (expense) income, net |  |  |  |  |  |  |  |  |  |  | (20,162) | (19,673) |  | (18,924)
Income before income taxes |  |  |  |  |  |  |  |  |  |  | 112,706 | 128,504 |  | 119,764
Income tax (provision) benefit |  | (7,417) | (15,351) | (8,008) | (10,587) | (8,600) |  | (14,286) | (9,034) | (16,265) | (41,363) | (48,185) |  | (44,859)
Net Income |  | 11,232 | $ 28,354 | $ 13,479 | $ 18,278 | 15,186 |  | $ 23,329 | $ 14,087 | $ 27,717 | 71,343 | 80,319 |  | 74,905
Segment Reporting Information Assets And Capital Expenditures [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Assets |  | 1,730,673 |  |  |  | 1,694,184 | [1] |  |  |  | 1,730,673 | 1,694,184 | [1] | 1,579,060
Capital expenditures |  |  |  |  |  |  |  |  |  |  | 72,030 | 92,676 |  | 119,047
Electric [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 412,528 | 394,849 |  | 403,957
Gas [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 143,737 | 221,720 |  | 181,462
Non Regulated Energy [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 7,763 | 3,283 |  | 5,468
Transmission Investment [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
All Others [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Operating Segments [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 564,028 | 619,852 |  | 590,887
Operating Segments [Member] | Electric [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 413,041 | 395,358 |  | 404,494
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  | (29,945) | (26,933) |  | (25,780)
Other operating expenses |  |  |  |  |  |  |  |  |  |  | (318,001) | (297,409) |  | (316,277)
Operating Income (Loss) |  |  |  |  |  |  |  |  |  |  | 65,095 | 71,016 |  | 62,437
Other (deductions) income, net |  |  |  |  |  |  |  |  |  |  | 400 | 2,847 |  | 3,062
Interest (expense) income, net |  |  |  |  |  |  |  |  |  |  | (11,187) | (10,410) |  | (9,645)
Income before income taxes |  |  |  |  |  |  |  |  |  |  | 54,308 | 63,453 |  | 55,854
Income tax (provision) benefit |  |  |  |  |  |  |  |  |  |  | (17,915) | (22,070) |  | (19,176)
Net Income |  |  |  |  |  |  |  |  |  |  | 36,393 | 41,383 |  | 36,678
Segment Reporting Information Assets And Capital Expenditures [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Assets |  | 976,271 |  |  |  | 948,005 | [1] |  |  |  | 976,271 | 948,005 | [1] | 899,257
Capital expenditures |  |  |  |  |  |  |  |  |  |  | 49,370 | 68,067 |  | 100,146
Operating Segments [Member] | Gas [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 155,517 | 230,086 |  | 194,091
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  | (6,758) | (6,308) |  | (5,898)
Other operating expenses |  |  |  |  |  |  |  |  |  |  | (128,241) | (194,203) |  | (162,661)
Operating Income (Loss) |  |  |  |  |  |  |  |  |  |  | 20,518 | 29,575 |  | 25,532
Other (deductions) income, net |  |  |  |  |  |  |  |  |  |  | (33) | (86) |  | 59
Interest (expense) income, net |  |  |  |  |  |  |  |  |  |  | (3,203) | (3,229) |  | (2,986)
Income before income taxes |  |  |  |  |  |  |  |  |  |  | 17,282 | 26,260 |  | 22,605
Income tax (provision) benefit |  |  |  |  |  |  |  |  |  |  | (6,915) | (10,480) |  | (9,168)
Net Income |  |  |  |  |  |  |  |  |  |  | 10,367 | 15,780 |  | 13,437
Segment Reporting Information Assets And Capital Expenditures [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Assets |  | 299,792 |  |  |  | 307,582 | [1] |  |  |  | 299,792 | 307,582 | [1] | 265,694
Capital expenditures |  |  |  |  |  |  |  |  |  |  | 18,787 | 22,104 |  | 15,554
Operating Segments [Member] | Non Regulated Energy [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 47,198 | 45,975 |  | 48,059
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  | (7,475) | (7,407) |  | (7,156)
Other operating expenses |  |  |  |  |  |  |  |  |  |  | (158) | (139) |  | (128)
Operating Income (Loss) |  |  |  |  |  |  |  |  |  |  | 39,565 | 38,429 |  | 40,775
Other (deductions) income, net |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Interest (expense) income, net |  |  |  |  |  |  |  |  |  |  | (5,993) | (6,208) |  | (6,400)
Income before income taxes |  |  |  |  |  |  |  |  |  |  | 33,572 | 32,221 |  | 34,375
Income tax (provision) benefit |  |  |  |  |  |  |  |  |  |  | (13,474) | (12,932) |  | (13,682)
Net Income |  |  |  |  |  |  |  |  |  |  | 20,098 | 19,289 |  | 20,693
Segment Reporting Information Assets And Capital Expenditures [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Assets |  | 278,735 |  |  |  | 281,514 | [1] |  |  |  | 278,735 | 281,514 | [1] | 288,116
Capital expenditures |  |  |  |  |  |  |  |  |  |  | 3,873 | 2,505 |  | 3,347
Operating Segments [Member] | Transmission Investment [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Other operating expenses |  |  |  |  |  |  |  |  |  |  | (19) | 0 |  | (1)
Operating Income (Loss) |  |  |  |  |  |  |  |  |  |  | (19) | 0 |  | (1)
Other (deductions) income, net |  |  |  |  |  |  |  |  |  |  | 7,728 | 9,150 |  | 9,434
Interest (expense) income, net |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Income before income taxes |  |  |  |  |  |  |  |  |  |  | 7,709 | 9,150 |  | 9,433
Income tax (provision) benefit |  |  |  |  |  |  |  |  |  |  | (3,102) | (3,664) |  | (3,796)
Net Income |  |  |  |  |  |  |  |  |  |  | 4,607 | 5,486 |  | 5,637
Segment Reporting Information Assets And Capital Expenditures [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Assets |  | 69,470 |  |  |  | 67,697 | [1] |  |  |  | 69,470 | 67,697 | [1] | 64,504
Capital expenditures |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Operating Segments [Member] | All Others [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  | (47) | (47) |  | (4)
Other operating expenses |  |  |  |  |  |  |  |  |  |  | (857) | (875) |  | (752)
Operating Income (Loss) |  |  |  |  |  |  |  |  |  |  | (904) | (922) |  | (756)
Other (deductions) income, net |  |  |  |  |  |  |  |  |  |  | 518 | (1,832) |  | (1,854)
Interest (expense) income, net |  |  |  |  |  |  |  |  |  |  | 221 | 174 |  | 107
Income before income taxes |  |  |  |  |  |  |  |  |  |  | (165) | (2,580) |  | (2,503)
Income tax (provision) benefit |  |  |  |  |  |  |  |  |  |  | 43 | 961 |  | 963
Net Income |  |  |  |  |  |  |  |  |  |  | (122) | (1,619) |  | (1,540)
Segment Reporting Information Assets And Capital Expenditures [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Assets |  | 434,868 |  |  |  | 438,898 | [1] |  |  |  | 434,868 | 438,898 | [1] | 431,436
Capital expenditures |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Operating Segments [Member] | Assets Not Allocated [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information Assets And Capital Expenditures [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Assets |  | 49,753 |  |  |  | 41,124 | [1] |  |  |  | 49,753 | 41,124 | [1] | 19,853
Capital expenditures |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Consolidation/Elimination Entries [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | (51,728) | (51,567) |  | (55,757)
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Other operating expenses |  |  |  |  |  |  |  |  |  |  | 51,728 | 51,567 |  | 55,757
Operating Income (Loss) |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Other (deductions) income, net |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Interest (expense) income, net |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Income before income taxes |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Income tax (provision) benefit |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Net Income |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Segment Reporting Information Assets And Capital Expenditures [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Assets |  | (378,216) |  |  |  | (390,636) | [1] |  |  |  | (378,216) | (390,636) | [1] | (389,800)
Capital expenditures |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Consolidation/Elimination Entries [Member] | Electric [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 513 | 509 |  | 537
Consolidation/Elimination Entries [Member] | Gas [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 11,780 | 8,366 |  | 12,629
Consolidation/Elimination Entries [Member] | Non Regulated Energy [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 39,435 | 42,692 |  | 42,591
Consolidation/Elimination Entries [Member] | Transmission Investment [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Consolidation/Elimination Entries [Member] | All Others [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
MGE [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 564,065 | 619,895 |  | 590,925
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  | (44,178) | (40,648) |  | (38,834)
Other operating expenses | [2] |  |  |  |  |  |  |  |  |  | (432,887) | (485,319) |  | (464,868)
Operating Income (Loss) | [2] |  |  |  |  |  |  |  |  |  | 87,000 | 93,928 |  | 87,223
Other (deductions) income, net | [2] |  |  |  |  |  |  |  |  |  | 4,848 | 7,857 |  | 8,253
Interest (expense) income, net |  |  |  |  |  |  |  |  |  |  | (20,383) | (19,847) |  | (19,031)
Income tax (provision) benefit |  |  |  |  |  |  |  |  |  |  | (41,406) | (49,145) |  | (45,822)
Net Income Including Noncontrolling Interest |  |  |  |  |  |  |  |  |  |  | 71,465 | 81,938 |  | 76,445
Less Net Income Attributable to Noncontrolling Interest, net of tax |  |  |  |  |  |  |  |  |  |  | (26,097) | (26,310) |  | (27,438)
Net Income |  |  |  |  |  |  |  |  |  |  | 45,368 | 55,628 |  | 49,007
Segment Reporting Information Assets And Capital Expenditures [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Assets |  | 1,673,784 |  |  |  | 1,639,351 | [1] |  |  |  | 1,673,784 | 1,639,351 | [1] | 1,530,643
Capital expenditures |  |  |  |  |  |  |  |  |  |  | 72,030 | 92,676 |  | 119,047
MGE [Member] | Electric [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 412,550 | 394,871 |  | 403,980
MGE [Member] | Gas [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 143,752 | 221,741 |  | 181,477
MGE [Member] | Non Regulated Energy [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 7,763 | 3,283 |  | 5,468
MGE [Member] | Transmission Investment [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
MGE [Member] | Operating Segments [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 564,065 | 619,895 |  | 590,925
MGE [Member] | Operating Segments [Member] | Electric [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 413,041 | 395,358 |  | 404,494
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  | (29,945) | (26,933) |  | (25,780)
Other operating expenses | [2] |  |  |  |  |  |  |  |  |  | (335,803) | (319,175) |  | (335,059)
Operating Income (Loss) | [2] |  |  |  |  |  |  |  |  |  | 47,293 | 49,250 |  | 43,655
Other (deductions) income, net | [2] |  |  |  |  |  |  |  |  |  | 287 | 2,543 |  | 2,668
Interest (expense) income, net |  |  |  |  |  |  |  |  |  |  | (11,187) | (10,410) |  | (9,645)
Net Income Including Noncontrolling Interest |  |  |  |  |  |  |  |  |  |  | 36,393 | 41,383 |  | 36,678
Less Net Income Attributable to Noncontrolling Interest, net of tax |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Net Income |  |  |  |  |  |  |  |  |  |  | 36,393 | 41,383 |  | 36,678
Segment Reporting Information Assets And Capital Expenditures [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Assets |  | 976,271 |  |  |  | 948,005 | [1] |  |  |  | 976,271 | 948,005 | [1] | 899,257
Capital expenditures |  |  |  |  |  |  |  |  |  |  | 49,370 | 68,067 |  | 100,146
MGE [Member] | Operating Segments [Member] | Gas [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 155,517 | 230,086 |  | 194,091
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  | (6,758) | (6,308) |  | (5,898)
Other operating expenses | [2] |  |  |  |  |  |  |  |  |  | (135,124) | (204,597) |  | (171,717)
Operating Income (Loss) | [2] |  |  |  |  |  |  |  |  |  | 13,635 | 19,181 |  | 16,476
Other (deductions) income, net | [2] |  |  |  |  |  |  |  |  |  | (65) | (172) |  | (53)
Interest (expense) income, net |  |  |  |  |  |  |  |  |  |  | (3,203) | (3,229) |  | (2,986)
Net Income Including Noncontrolling Interest |  |  |  |  |  |  |  |  |  |  | 10,367 | 15,780 |  | 13,437
Less Net Income Attributable to Noncontrolling Interest, net of tax |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Net Income |  |  |  |  |  |  |  |  |  |  | 10,367 | 15,780 |  | 13,437
Segment Reporting Information Assets And Capital Expenditures [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Assets |  | 299,792 |  |  |  | 307,582 | [1] |  |  |  | 299,792 | 307,582 | [1] | 265,694
Capital expenditures |  |  |  |  |  |  |  |  |  |  | 18,787 | 22,104 |  | 15,554
MGE [Member] | Operating Segments [Member] | Non Regulated Energy [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 47,198 | 45,975 |  | 48,059
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  | (7,475) | (7,407) |  | (7,156)
Other operating expenses | [2] |  |  |  |  |  |  |  |  |  | (13,632) | (13,071) |  | (13,810)
Operating Income (Loss) | [2] |  |  |  |  |  |  |  |  |  | 26,091 | 25,497 |  | 27,093
Other (deductions) income, net | [2] |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Interest (expense) income, net |  |  |  |  |  |  |  |  |  |  | (5,993) | (6,208) |  | (6,400)
Net Income Including Noncontrolling Interest |  |  |  |  |  |  |  |  |  |  | 20,098 | 19,289 |  | 20,693
Less Net Income Attributable to Noncontrolling Interest, net of tax |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Net Income |  |  |  |  |  |  |  |  |  |  | 20,098 | 19,289 |  | 20,693
Segment Reporting Information Assets And Capital Expenditures [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Assets |  | 278,685 |  |  |  | 281,464 | [1] |  |  |  | 278,685 | 281,464 | [1] | 288,066
Capital expenditures |  |  |  |  |  |  |  |  |  |  | 3,873 | 2,505 |  | 3,347
MGE [Member] | Operating Segments [Member] | Transmission Investment [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Other operating expenses | [2] |  |  |  |  |  |  |  |  |  | (19) | 0 |  | (1)
Operating Income (Loss) | [2] |  |  |  |  |  |  |  |  |  | (19) | 0 |  | (1)
Other (deductions) income, net | [2] |  |  |  |  |  |  |  |  |  | 4,626 | 5,486 |  | 5,638
Interest (expense) income, net |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Net Income Including Noncontrolling Interest |  |  |  |  |  |  |  |  |  |  | 4,607 | 5,486 |  | 5,637
Less Net Income Attributable to Noncontrolling Interest, net of tax |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Net Income |  |  |  |  |  |  |  |  |  |  | 4,607 | 5,486 |  | 5,637
Segment Reporting Information Assets And Capital Expenditures [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Assets |  | 69,470 |  |  |  | 67,697 | [1] |  |  |  | 69,470 | 67,697 | [1] | 64,504
Capital expenditures |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
MGE [Member] | Operating Segments [Member] | Assets Not Allocated [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information Assets And Capital Expenditures [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Assets |  | 49,753 |  |  |  | 41,124 | [1] |  |  |  | 49,753 | 41,124 | [1] | 19,853
Capital expenditures |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
MGE [Member] | Consolidation/Elimination Entries [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | (51,691) | (51,524) |  | (55,719)
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Other operating expenses | [2] |  |  |  |  |  |  |  |  |  | 51,691 | 51,524 |  | 55,719
Operating Income (Loss) | [2] |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Other (deductions) income, net | [2] |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Interest (expense) income, net |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Net Income Including Noncontrolling Interest |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
Less Net Income Attributable to Noncontrolling Interest, net of tax |  |  |  |  |  |  |  |  |  |  | (26,097) | (26,310) |  | (27,438)
Net Income |  |  |  |  |  |  |  |  |  |  | (26,097) | (26,310) |  | (27,438)
Segment Reporting Information Assets And Capital Expenditures [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Assets |  | $ (187) |  |  |  | $ (6,521) | [1] |  |  |  | (187) | (6,521) | [1] | (6,731)
Capital expenditures |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  | 0
MGE [Member] | Consolidation/Elimination Entries [Member] | Electric [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 491 | 487 |  | 514
MGE [Member] | Consolidation/Elimination Entries [Member] | Gas [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 11,765 | 8,345 |  | 12,614
MGE [Member] | Consolidation/Elimination Entries [Member] | Non Regulated Energy [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | 39,435 | 42,692 |  | 42,591
MGE [Member] | Consolidation/Elimination Entries [Member] | Transmission Investment [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating revenues |  |  |  |  |  |  |  |  |  |  | $ 0 | $ 0 |  | $ 0
[1] | Reflects retrospective application of new accounting pronouncement. See Footnote 12 for additional information.
[2] | *Amounts are shown net of the related tax expense, consistent with the presentation on the MGE Consolidated Statements of Income.

X
- References No definition available. + Details
Name: | mgee_SegmentReportingInformationAssetsAndCapitalExpendituresAbstract
Namespace Prefix: | mgee_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Discloses the total amount of operating expense for the period excluding depreciation and amortization. + References No definition available. + Details
Name: | mgee_UtilitiesOperatingExpenseExcludingDepreciationAndAmortization
Namespace Prefix: | mgee_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.18) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 12 -Article 7 + Details
Name: | us-gaap_Assets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The portion of earnings or loss from continuing operations before income taxes that is attributable to domestic operations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(h)(1)(i)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 + Details
Name: | us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a),(b) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32639-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(h)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Income Tax Expense (or Benefit) -URI http://asc.fasb.org/extlink&oid=6515339 + Details
Name: | us-gaap_IncomeTaxExpenseBenefit
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The net amount of operating interest income (expense). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.10) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
Name: | us-gaap_InterestIncomeExpenseNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The portion of profit or loss for the period, net of income taxes, which is attributable to the parent. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Net Income -URI http://asc.fasb.org/extlink&oid=51831255 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.19) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.18) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.22) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Other Comprehensive Income -URI http://asc.fasb.org/extlink&oid=51831270 Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 19 -Article 5 Reference 9: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 20 -Article 9 + Details
Name: | us-gaap_NetIncomeLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of Net Income (Loss) attributable to noncontrolling interest. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4J -URI http://asc.fasb.org/extlink&oid=35736750&loc=SL4591551-111686 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=18733093&loc=SL4573702-111684 + Details
Name: | us-gaap_NetIncomeLossAttributableToNoncontrollingInterest
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The aggregate amount of income or expense from ancillary business-related activities (that is to say, excluding major activities considered part of the normal operations of the business). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.7) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 + Details
Name: | us-gaap_NonoperatingIncomeExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The net result for the period of deducting operating expenses from operating revenues. + References No definition available. + Details
Name: | us-gaap_OperatingIncomeLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3213-108585 + Details
Name: | us-gaap_PaymentsToAcquirePropertyPlantAndEquipment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 19 -URI http://asc.fasb.org/extlink&oid=51664549&loc=SL4569616-111683 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4K -URI http://asc.fasb.org/extlink&oid=35736750&loc=SL4591552-111686 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=18733093&loc=SL4573702-111684 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4J -URI http://asc.fasb.org/extlink&oid=35736750&loc=SL4591551-111686 + Details
Name: | us-gaap_ProfitLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The total amount of operating revenues recognized during the period. + References No definition available. + Details
Name: | us-gaap_RegulatedAndUnregulatedOperatingRevenue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- 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
Name: | us-gaap_SegmentReportingInformationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of operating expense for depreciation and amortization of regulated operation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.2(b)) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 + Details
Name: | us-gaap_UtilitiesOperatingExpenseDepreciationAndAmortization
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=mgee_ElectricMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=mgee_GasMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=mgee_NonRegulatedEnergyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=mgee_TransmissionInvestmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=us-gaap_CorporateAndOtherMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConsolidationItemsAxis=us-gaap_OperatingSegmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=mgee_AssetsNotAllocatedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConsolidationItemsAxis=us-gaap_IntersegmentEliminationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=us-gaap_SubsidiariesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |