Fair Value of Financial Instruments (Details-2) - USD ($) $ in Thousands		Jun. 30, 2020	Dec. 31, 2019
Liabilities:
Collateral posted against derivative positions		$ 300	$ 1,500
Recurring [Member]
Assets:
Derivatives		1,475	303
Total Assets		3,097	1,574
Liabilities:
Derivatives	[1]	21,875	27,178
Deferred compensation		3,339	3,157
Total liabilities		25,214	30,335
Recurring [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities		1,622	1,271
Recurring [Member] | Level 1 [Member]
Assets:
Derivatives		1,076	189
Total Assets		2,698	1,460
Liabilities:
Derivatives	[1]	453	608
Deferred compensation		0	0
Total liabilities		453	608
Recurring [Member] | Level 1 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities		1,622	1,271
Recurring [Member] | Level 2 [Member]
Assets:
Derivatives		0	0
Total Assets		0	0
Liabilities:
Derivatives	[1]	0	0
Deferred compensation		3,339	3,157
Total liabilities		3,339	3,157
Recurring [Member] | Level 2 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities		0	0
Recurring [Member] | Level 3 [Member]
Assets:
Derivatives		399	114
Total Assets		399	114
Liabilities:
Derivatives	[1]	21,422	26,570
Deferred compensation		0	0
Total liabilities		21,422	26,570
Recurring [Member] | Level 3 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities		0	0
MGE [Member]
Liabilities:
Collateral posted against derivative positions		300	1,500
MGE [Member] | Recurring [Member]
Assets:
Derivatives		1,475	303
Total Assets		1,688	512
Liabilities:
Derivatives	[1]	21,875	27,178
Deferred compensation		3,339	3,157
Total liabilities		25,214	30,335
MGE [Member] | Recurring [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities		213	209
MGE [Member] | Recurring [Member] | Level 1 [Member]
Assets:
Derivatives		1,076	189
Total Assets		1,289	398
Liabilities:
Derivatives	[1]	453	608
Deferred compensation		0	0
Total liabilities		453	608
MGE [Member] | Recurring [Member] | Level 1 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities		213	209
MGE [Member] | Recurring [Member] | Level 2 [Member]
Assets:
Derivatives		0	0
Total Assets		0	0
Liabilities:
Derivatives	[1]	0	0
Deferred compensation		3,339	3,157
Total liabilities		3,339	3,157
MGE [Member] | Recurring [Member] | Level 2 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities		0	0
MGE [Member] | Recurring [Member] | Level 3 [Member]
Assets:
Derivatives		399	114
Total Assets		399	114
Liabilities:
Derivatives	[1]	21,422	26,570
Deferred compensation		0	0
Total liabilities		21,422	26,570
MGE [Member] | Recurring [Member] | Level 3 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities		$ 0	$ 0

[1] These amounts are shown gross and exclude $0.3 million and $1.5 million of collateral that was posted against derivative positions with counterparties as of June 30, 2020 and December 31, 2019, respectively.