Noncontrolling Interest (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
MGE Power [Member]
Noncontrolling Interest [Line Items]
Ownership percentage by parent		100.00%
MGE [Member]
Noncontrolling Interest [Line Items]
Noncontrolling interest on balance sheet		$ 148,587	$ 141,196
Net income attributable to noncontrolling interest, net of tax		$ 22,391	22,393	$ 22,349
MGE Power Elm Road [Member]
Noncontrolling Interest [Line Items]
Ownership percentage by parent		100.00%
Noncontrolling interest on balance sheet	[1]	$ 101,507	96,856
Net income attributable to noncontrolling interest, net of tax	[1]	$ 15,151	15,184	15,153
MGE Power West Campus [Member]
Noncontrolling Interest [Line Items]
Ownership percentage by parent		100.00%
Noncontrolling interest on balance sheet	[1]	$ 47,080	44,340
Net income attributable to noncontrolling interest, net of tax	[1]	$ 7,240	$ 7,209	$ 7,196

[1] MGE Power Elm Road and MGE Power West Campus are not subsidiaries of MGE; however, they have been consolidated in the consolidated financial statements of MGE (see Footnote 3). MGE Power Elm Road and MGE Power West Campus are 100% owned by MGE Power, and MGE Power is 100% owned by MGE Energy. MGE Energy's proportionate share of the equity and net income (through its wholly owned subsidiary MGE Power) of MGE Power Elm Road and MGE Power West Campus is classified within the MGE consolidated financial statements as noncontrolling interest