Fair Value of Financial Instruments (Details-2) - Recurring [Member] - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Assets:
Derivatives	$ 1,536	$ 1,527
Total Assets	2,352	2,027
Liabilities:
Derivatives	43,812	50,808
Deferred compensation	3,150	3,039
Total liabilities	46,962	53,847
Exchange Traded [Member]
Assets:
Available-for-sale securities	816	500
Level 1 [Member]
Assets:
Derivatives	673	1,041
Total Assets	1,489	1,541
Liabilities:
Derivatives	190	16
Deferred compensation	0	0
Total liabilities	190	16
Level 1 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	816	500
Level 2 [Member]
Assets:
Derivatives	0	0
Total Assets	0	0
Liabilities:
Derivatives	0	0
Deferred compensation	3,150	3,039
Total liabilities	3,150	3,039
Level 2 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	0	0
Level 3 [Member]
Assets:
Derivatives	863	486
Total Assets	863	486
Liabilities:
Derivatives	43,622	50,792
Deferred compensation	0	0
Total liabilities	43,622	50,792
Level 3 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	0	0
MGE [Member]
Assets:
Derivatives	1,536	1,527
Total Assets	1,614	1,670
Liabilities:
Derivatives	43,812	50,808
Deferred compensation	3,150	3,039
Total liabilities	46,962	53,847
MGE [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	78	143
MGE [Member] | Level 1 [Member]
Assets:
Derivatives	673	1,041
Total Assets	751	1,184
Liabilities:
Derivatives	190	16
Deferred compensation	0	0
Total liabilities	190	16
MGE [Member] | Level 1 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	78	143
MGE [Member] | Level 2 [Member]
Assets:
Derivatives	0	0
Total Assets	0	0
Liabilities:
Derivatives	0	0
Deferred compensation	3,150	3,039
Total liabilities	3,150	3,039
MGE [Member] | Level 2 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	0	0
MGE [Member] | Level 3 [Member]
Assets:
Derivatives	863	486
Total Assets	863	486
Liabilities:
Derivatives	43,622	50,792
Deferred compensation	0	0
Total liabilities	43,622	50,792
MGE [Member] | Level 3 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	$ 0	$ 0