Schedule I - Condensed Parent Company Finanical Statements (Details-Notes 2) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
MGE Energy [Member]
Dividends from Affiliates [Line Items]
Dividends from affiliates	$ 26,735	$ 67,781	$ 74,107
First Mortgage Bonds [Member] | 7.70%, 2028 Series
Dividend Restrictions
Debt covenant, allowable amount available for payment of dividends	400,000
MGE [Member]
Dividends from Affiliates [Line Items]
Dividends from affiliates	0	45,000	50,000	[1]
Dividend in kind from affiliate	$ 0	0	15,822
Dividend Restrictions
Common equity ratio	0.563
Amount available for dividend payments without regulatory approval	$ 70,800
MGE [Member] | Minimum [Member]
Dividend Restrictions
Dividend restrictions, common equity ratio	0.55
MGE Power Elm Road [Member]
Dividends from Affiliates [Line Items]
Dividends from affiliates	$ 15,500	12,000	13,500
MGE Power West Campus [Member]
Dividends from Affiliates [Line Items]
Dividends from affiliates	6,500	6,000	9,500
MGE Transco [Member]
Dividends from Affiliates [Line Items]
Dividends from affiliates	4,625	4,669	1,107
MGEE Transco [Member]
Dividends from Affiliates [Line Items]
Dividends from affiliates	60	112	0
NGV Fueling Services [Member]
Dividends from Affiliates [Line Items]
Dividends from affiliates	$ 50	$ 0	$ 0

[1] Excludes $15.8 million dividend in kind to MGE Energy from MGE in 2016 .