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Schedule I - Condensed Parent Company Finanical Statements (Details-Comprehensive Income Statement) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2019 | Sep. 30, 2019 | Jun. 30, 2019 | Mar. 31, 2019 | Dec. 31, 2018 | Sep. 30, 2018 | Jun. 30, 2018 | Mar. 31, 2018 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Operating Expenses: |  |  |  |  |  |  |  |  |  |  |  |
Other operations and maintenance |  |  |  |  |  |  |  |  | $ 193,322 | $ 177,823 | $ 177,740 |
Total Operating Expenses | $ 119,064 | $ 99,460 | $ 102,364 | $ 137,057 | $ 116,089 | $ 97,997 | $ 100,031 | $ 131,444 | 457,945 | 445,561 | 438,474 |
Operating Income (Loss) | 21,877 | 38,738 | 19,783 | 30,512 | 23,990 | 39,798 | 24,231 | 26,188 | 110,910 | 114,207 | 124,625 |
Equity earnings of investments |  |  |  |  |  |  |  |  | 9,889 | 8,821 | 10,125 |
Income before income taxes |  |  |  |  |  |  |  |  | 106,658 | 111,653 | 119,700 |
Income tax provision | (3,116) | (7,454) | (3,505) | (5,709) | (5,642) | (9,597) | (5,828) | (6,367) | (19,784) | (27,434) | (22,094) | [1]
Net Income | $ 16,662 | $ 30,657 | $ 15,548 | $ 24,007 | $ 16,361 | $ 29,506 | $ 18,351 | $ 20,001 | 86,874 | 84,219 | 97,606 |
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] |  |  |  |  |  |  |  |  |  |  |  |
Unrealized gain (loss) on available for sale securities, net of tax |  |  |  |  |  |  |  |  | 0 | 0 | 175 |
Comprehensive Income |  |  |  |  |  |  |  |  | 86,874 | 84,219 | 97,781 |
MGE Energy [Member] |  |  |  |  |  |  |  |  |  |  |  |
Operating Expenses: |  |  |  |  |  |  |  |  |  |  |  |
Other operations and maintenance |  |  |  |  |  |  |  |  | 815 | 913 | 880 |
Total Operating Expenses |  |  |  |  |  |  |  |  | 815 | 913 | 880 |
Operating Income (Loss) |  |  |  |  |  |  |  |  | (815) | (913) | (880) |
Equity earnings of investments |  |  |  |  |  |  |  |  | 87,728 | 85,220 | 99,246 |
Other income/(loss), net |  |  |  |  |  |  |  |  | (1,500) | (1,966) | (2,165) |
Interest income, net |  |  |  |  |  |  |  |  | 1,224 | 1,489 | 605 |
Income before income taxes |  |  |  |  |  |  |  |  | 86,637 | 83,830 | 96,806 |
Income tax provision |  |  |  |  |  |  |  |  | 237 | 389 | 800 |
Net Income |  |  |  |  |  |  |  |  | 86,874 | 84,219 | 97,606 |
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] |  |  |  |  |  |  |  |  |  |  |  |
Unrealized gain (loss) on available for sale securities, net of tax |  |  |  |  |  |  |  |  | 0 | 0 | 175 |
Comprehensive Income |  |  |  |  |  |  |  |  | $ 86,874 | $ 84,219 | $ 97,781 |
[1] | In December 2017, there was a $21.7 million one-time tax impact as a result of the Tax Act.

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