Fair Value of Financial Instruments (Details-2) - USD ($) $ in Thousands	Dec. 31, 2019		Dec. 31, 2018
Assets:
Available-for-sale securities	$ 14,546		$ 9,363
Liabilities:
Collateral posted against derivative positions	1,500
Recurring [Member]
Assets:
Derivative assets, net	303		1,042
Total Assets	1,574		1,890
Liabilities:
Derivative liabilities, net	27,178	[1]	32,872
Deferred compensation	3,157		3,078
Total Liabilities	30,335		35,950
Recurring [Member] | Exchange-traded investments
Assets:
Available-for-sale securities	1,271		848
Recurring [Member] | Level 1 [Member]
Assets:
Derivative assets, net	189		296
Total Assets	1,460		1,144
Liabilities:
Derivative liabilities, net	608	[1]	124
Deferred compensation	0		0
Total Liabilities	608		124
Recurring [Member] | Level 1 [Member] | Exchange-traded investments
Assets:
Available-for-sale securities	1,271		848
Recurring [Member] | Level 2 [Member]
Assets:
Derivative assets, net	0		0
Total Assets	0		0
Liabilities:
Derivative liabilities, net	0	[1]	0
Deferred compensation	3,157		3,078
Total Liabilities	3,157		3,078
Recurring [Member] | Level 2 [Member] | Exchange-traded investments
Assets:
Available-for-sale securities	0		0
Recurring [Member] | Level 3 [Member]
Assets:
Derivative assets, net	114		746
Total Assets	114		746
Liabilities:
Derivative liabilities, net	26,570	[1]	32,748
Deferred compensation	0		0
Total Liabilities	26,570		32,748
Recurring [Member] | Level 3 [Member] | Exchange-traded investments
Assets:
Available-for-sale securities	0		0
MGE [Member]
Assets:
Available-for-sale securities	209		388
Liabilities:
Collateral posted against derivative positions	0		100
MGE [Member] | Recurring [Member]
Assets:
Derivative assets, net	303		1,042
Total Assets	512		1,085
Liabilities:
Derivative liabilities, net	27,178	[1]	32,872
Deferred compensation	3,157		3,078
Total Liabilities	30,335		35,950
MGE [Member] | Recurring [Member] | Exchange-traded investments
Assets:
Available-for-sale securities	209		43
MGE [Member] | Recurring [Member] | Level 1 [Member]
Assets:
Derivative assets, net	189		296
Total Assets	398		339
Liabilities:
Derivative liabilities, net	608	[1]	124
Deferred compensation	0		0
Total Liabilities	608		124
MGE [Member] | Recurring [Member] | Level 1 [Member] | Exchange-traded investments
Assets:
Available-for-sale securities	209		43
MGE [Member] | Recurring [Member] | Level 2 [Member]
Assets:
Derivative assets, net	0		0
Total Assets	0		0
Liabilities:
Derivative liabilities, net	0	[1]	0
Deferred compensation	3,157		3,078
Total Liabilities	3,157		3,078
MGE [Member] | Recurring [Member] | Level 2 [Member] | Exchange-traded investments
Assets:
Available-for-sale securities	0		0
MGE [Member] | Recurring [Member] | Level 3 [Member]
Assets:
Derivative assets, net	114		746
Total Assets	114		746
Liabilities:
Derivative liabilities, net	26,570	[1]	32,748
Deferred compensation	0		0
Total Liabilities	26,570		32,748
MGE [Member] | Recurring [Member] | Level 3 [Member] | Exchange-traded investments
Assets:
Available-for-sale securities	$ 0		$ 0

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