Revenue (Details-1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Total Operating Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	$ 568,855	$ 559,768	$ 563,099	[1]
Electric [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	408,285	400,882	413,926
Electric [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	140,006	138,566	136,168
Electric [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	213,265	204,683	216,461	[1]
Electric [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	12,772	13,878	16,176
Electric [Member] | Other-retail/municipal [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	35,174	34,023	38,010
Electric [Member] | Total Retail [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	401,217	391,150	406,815
Electric [Member] | Sales To The Market [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	5,664	7,438	4,067
Electric [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	1,404	2,294	3,044
Gas [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	159,875	157,767	148,825
Gas [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	95,146	94,017	88,695
Gas [Member] | Commercial/Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	59,051	59,060	55,151	[1]
Gas [Member] | Total Retail [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	154,197	153,077	143,846
Gas [Member] | Gas Transportation [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	5,293	4,283	4,561
Gas [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	385	407	418
Non Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	$ 695	$ 1,119	348
MGE [Member]
Disaggregation of Revenue [Line Items]
CNG Vehicle Fuel Servicing			$ 100

[1] In 2017, MGE had less than $0.1 million of revenues related to compressed natural gas vehicle fuel servicing. No revenue was recognized for fuel servicing by MGE Energy in 2017.