Pension Plans and Other Postretirement Benefits (Details-2) - USD ($)	12 Months Ended
	Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Deferred Net Periodic Benefit Cost [Abstract]
Deferred pension and OPRB costs	$ 6,200,000
Pension Benefits [Member]
Components of Net Periodic Benefit Cost
Service cost	4,692,000	[1]	$ 5,723,000	$ 5,383,000
Interest cost	14,302,000	[1]	12,859,000	12,625,000
Expected return on assets	(22,786,000)	[1]	(26,241,000)	(22,963,000)
Amortization of:
Transition obligation	0	[1]	0	0
Prior service (credit) cost	(117,000)	[1]	(44,000)	(17,000)
Actuarial loss	7,379,000	[1]	5,278,000	6,352,000
Net periodic benefit cost (credit)	3,470,000	[1]	(2,425,000)	1,380,000
Postretirement Benefits [Member]
Components of Net Periodic Benefit Cost
Service cost	1,110,000	[1]	1,283,000	1,231,000
Interest cost	2,893,000	[1]	2,612,000	2,666,000
Expected return on assets	(2,723,000)	[1]	(3,232,000)	(2,887,000)
Amortization of:
Transition obligation	3,000	[1]	3,000	3,000
Prior service (credit) cost	(2,669,000)	[1]	(2,669,000)	(2,669,000)
Actuarial loss	401,000	[1]	488,000	660,000
Net periodic benefit cost (credit)	$ (985,000)	[1]	$ (1,515,000)	$ (996,000)

[1] MGE has deferred approximately $6.2 million of pension and other postretirement costs. The impact of the deferral has not been reflected in the table above. See Footnote 8 for further information.