Derivative and Hedging Instruments (Details-4) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022
Current and Long-Term Regulatory Asset (Liability) [Member]
Change In Derivative Fair Value [Roll Forward]
Beginning balance,	$ 5,094	$ (617)
Unrealized (loss) gain	14,303	(11,333)
Realized (loss) gain reclassified to a deferred account	(6,917)	1,279
Realized (loss) gain reclassified to income statement	(4,667)	1,030
Ending balance,	7,813	(9,641)
Other Current Assets [Member]
Change In Derivative Fair Value [Roll Forward]
Beginning balance,	2,747	770
Unrealized (loss) gain	0	0
Realized (loss) gain reclassified to a deferred account	6,917	(1,279)
Realized (loss) gain reclassified to income statement	(9,209)	776
Ending balance,	$ 455	$ 267

No definition available.

Name:	mgee_ChangeInDerivativeFairValueRollForward
Namespace Prefix:	mgee_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Change in realized derivative gains and losses deferred.

+ References

No definition available.

+ Details

Name:	mgee_DerivativeRealizedGainLossDeferred
Namespace Prefix:	mgee_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Fair value of the assets less the liabilities of a derivative or group of derivatives.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI https://asc.fasb.org/extlink&oid=123594938&loc=d3e13433-108611

+ Details

Name:	us-gaap_DerivativeFairValueOfDerivativeNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)(1)
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5618551-113959

+ Details

Name:	us-gaap_DerivativeGainLossOnDerivativeNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3602-108585

+ Details

Name:	us-gaap_UnrealizedGainLossOnDerivatives
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_BalanceSheetLocationAxis=mgee_RegulatoryAssetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_OtherCurrentAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: