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Investments (Details-1) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Equity Securities [Abstract] |  |  |
Equity Securities | $ 14,546 | $ 9,363 |
Equity method investments: |  |  |
Equity method investments | 71,648 | 66,339 | $ 20,400
Other Investments | 2,298 | 2,298 |
Total investments | 88,492 | 78,000 |
Results of Investment Liquidation [Abstract] |  |  |
Proceeds from sale of investments | 216 | 960 | 677
Gain (loss) on sale of investments | 580 | 476 | 522
ATC and ATC Holdco [Member] |  |  |
Equity method investments: |  |  |
Equity method investments | 71,609 | 66,313 |
Other Equity Method Investments [Member] |  |  |
Equity method investments: |  |  |
Equity method investments | 39 | 26 |
MGE [Member] |  |  |
Equity Securities [Abstract] |  |  |
Equity Securities | 209 | 388 |
Equity method investments: |  |  |
Equity method investments | 0 | 0 |
Other Investments | 0 | 0 |
Total investments | 209 | 388 |
Results of Investment Liquidation [Abstract] |  |  |
Proceeds from sale of investments | 2 | 3 | 0
Gain (loss) on sale of investments | (343) | 3 | $ 0
MGE [Member] | ATC and ATC Holdco [Member] |  |  |
Equity method investments: |  |  |
Equity method investments | 0 | 0 |
MGE [Member] | Other Equity Method Investments [Member] |  |  |
Equity method investments: |  |  |
Equity method investments | $ 0 | $ 0 |

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