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Fair Value of Financial Instruments (Details-1) - USD ($) $ in Thousands | Sep. 30, 2021 | Dec. 31, 2020
--- | --- | ---
Liabilities: |  |  |
Unamortized discount and debt issuance costs, net |  | $ 4,500 | $ 4,100
Carrying Amount [Member] |  |  |
Assets: |  |  |
Cash and cash equivalents |  | 70,454 | 44,738
Liabilities: |  |  |
Short-term debt - commercial paper |  | 0 | 52,500
Long-term debt | [1] | 624,653 | 528,220
Fair Value [Member] |  |  |
Assets: |  |  |
Cash and cash equivalents |  | 70,454 | 44,738
Liabilities: |  |  |
Short-term debt - commercial paper |  | 0 | 52,500
Long-term debt | [1] | 692,987 | 639,271
MGE [Member] |  |  |
Liabilities: |  |  |
Unamortized discount and debt issuance costs, net |  | 4,500 | 4,100
MGE [Member] | Carrying Amount [Member] |  |  |
Assets: |  |  |
Cash and cash equivalents |  | 57,003 | 4,103
Liabilities: |  |  |
Short-term debt - commercial paper |  | 0 | 52,500
Long-term debt | [1] | 624,653 | 528,220
MGE [Member] | Fair Value [Member] |  |  |
Assets: |  |  |
Cash and cash equivalents |  | 57,003 | 4,103
Liabilities: |  |  |
Short-term debt - commercial paper |  | 0 | 52,500
Long-term debt | [1] | $ 692,987 | $ 639,271
[1] | Includes long-term debt due within one year. Excludes debt issuance costs and unamortized discount of $4.5 million and $4.1 million as of September 30, 2021, and December 31, 2020, respectively.

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- Definition Fair value portion of commercial paper. + References No definition available. + Details
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- Definition Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. + References No definition available. + Details
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- Definition Amount of unamortized debt discount (premium) and debt issuance costs. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 55 -Paragraph 69C -URI http://asc.fasb.org/extlink&oid=123466577&loc=SL123495737-112612 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b)(2) -URI http://asc.fasb.org/extlink&oid=123466204&loc=SL6031897-161870 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 1D -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495340-112611 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 55 -Paragraph 69B -URI http://asc.fasb.org/extlink&oid=123466577&loc=SL123495735-112612 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=124435984&loc=d3e28555-108399 + Details
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- Definition The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. + References No definition available. + Details
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