Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Segment Reporting Information [Line Items]
Operating revenues	$ 217,253	$ 208,938
Equity in earnings of investment	2,611	2,504
Net income (loss)	31,078	34,420
Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	117,244	110,089
Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	99,962	98,811
Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	47	38
Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0
All Others [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	217,253	208,938
Equity in earnings of investment	2,611	2,504
Net income (loss)	31,078	34,420
Operating Segments [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	117,192	110,207
Equity in earnings of investment	0	0
Net income (loss)	13,314	14,617
Operating Segments [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	106,623	104,932
Equity in earnings of investment	0	0
Net income (loss)	10,759	12,084
Operating Segments [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	10,597	10,353
Equity in earnings of investment	0	0
Net income (loss)	5,570	5,352
Operating Segments [Member] | Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0
Equity in earnings of investment	2,611	2,504
Net income (loss)	1,899	1,822
Operating Segments [Member] | All Others [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0
Equity in earnings of investment	0	0
Net income (loss)	(464)	545
Consolidation Elimination Entries [Member]
Segment Reporting Information [Line Items]
Operating revenues	(17,159)	(16,554)
Equity in earnings of investment	0	0
Net income (loss)	0	0
Consolidation Elimination Entries [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	(52)	118
Consolidation Elimination Entries [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	6,661	6,121
Consolidation Elimination Entries [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	10,550	10,315
Consolidation Elimination Entries [Member] | Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0
Consolidation Elimination Entries [Member] | All Others [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0
MGE [Member]
Segment Reporting Information [Line Items]
Operating revenues	217,253	208,938
Net income (loss)	24,123	27,297
MGE [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	117,244	110,089
MGE [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	99,962	98,811
MGE [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	47	38
MGE [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	217,253	208,938
Net income (loss)	24,123	27,297
MGE [Member] | Operating Segments [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	117,192	110,207
Net income (loss)	13,314	14,617
MGE [Member] | Operating Segments [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	106,623	104,932
Net income (loss)	10,759	12,084
MGE [Member] | Operating Segments [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	10,597	10,353
Net income (loss)	5,570	5,352
MGE [Member] | Consolidation Elimination Entries [Member]
Segment Reporting Information [Line Items]
Operating revenues	(17,159)	(16,554)
Net income (loss)	(5,520)	(4,756)
MGE [Member] | Consolidation Elimination Entries [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	(52)	118
MGE [Member] | Consolidation Elimination Entries [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	6,661	6,121
MGE [Member] | Consolidation Elimination Entries [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	$ 10,550	$ 10,315