Fair Value of Financial Instruments (Details-2) - Recurring [Member] - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Assets:
Derivatives	$ 799	$ 1,042
Total Assets	1,762	1,890
Liabilities:
Derivatives	31,822	32,872
Deferred compensation	3,009	3,078
Total liabilities	34,831	35,950
Exchange Traded [Member]
Assets:
Available-for-sale securities	963	848
Level 1 [Member]
Assets:
Derivatives	316	296
Total Assets	1,279	1,144
Liabilities:
Derivatives	56	124
Deferred compensation	0	0
Total liabilities	56	124
Level 1 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	963	848
Level 2 [Member]
Assets:
Derivatives	0	0
Total Assets	0	0
Liabilities:
Derivatives	0	0
Deferred compensation	3,009	3,078
Total liabilities	3,009	3,078
Level 2 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	0	0
Level 3 [Member]
Assets:
Derivatives	483	746
Total Assets	483	746
Liabilities:
Derivatives	31,766	32,748
Deferred compensation	0	0
Total liabilities	31,766	32,748
Level 3 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	0	0
MGE [Member]
Assets:
Derivatives	799	1,042
Total Assets	869	1,085
Liabilities:
Derivatives	31,822	32,872
Deferred compensation	3,009	3,078
Total liabilities	34,831	35,950
MGE [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	70	43
MGE [Member] | Level 1 [Member]
Assets:
Derivatives	316	296
Total Assets	386	339
Liabilities:
Derivatives	56	124
Deferred compensation	0	0
Total liabilities	56	124
MGE [Member] | Level 1 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	70	43
MGE [Member] | Level 2 [Member]
Assets:
Derivatives	0	0
Total Assets	0	0
Liabilities:
Derivatives	0	0
Deferred compensation	3,009	3,078
Total liabilities	3,009	3,078
MGE [Member] | Level 2 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	0	0
MGE [Member] | Level 3 [Member]
Assets:
Derivatives	483	746
Total Assets	483	746
Liabilities:
Derivatives	31,766	32,748
Deferred compensation	0	0
Total liabilities	31,766	32,748
MGE [Member] | Level 3 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	$ 0	$ 0