Fair Value of Financial Instruments (Details-2) - Recurring [Member] - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Assets:
Derivatives	$ 819	$ 1,527
Total Assets	1,481	2,027
Liabilities:
Derivatives	48,892	50,808
Deferred compensation	3,014	3,039
Total liabilities	51,906	53,847
Exchange Traded [Member]
Assets:
Available-for-sale securities	662	500
Level 1 [Member]
Assets:
Derivatives	341	1,041
Total Assets	1,003	1,541
Liabilities:
Derivatives	60	16
Deferred compensation	0	0
Total liabilities	60	16
Level 1 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	662	500
Level 2 [Member]
Assets:
Derivatives	0	0
Total Assets	0	0
Liabilities:
Derivatives	0	0
Deferred compensation	3,014	3,039
Total liabilities	3,014	3,039
Level 2 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	0	0
Level 3 [Member]
Assets:
Derivatives	478	486
Total Assets	478	486
Liabilities:
Derivatives	48,832	50,792
Deferred compensation	0	0
Total liabilities	48,832	50,792
Level 3 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	0	0
MGE [Member]
Assets:
Derivatives	819	1,527
Total Assets	951	1,670
Liabilities:
Derivatives	48,892	50,808
Deferred compensation	3,014	3,039
Total liabilities	51,906	53,847
MGE [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	132	143
MGE [Member] | Level 1 [Member]
Assets:
Derivatives	341	1,041
Total Assets	473	1,184
Liabilities:
Derivatives	60	16
Deferred compensation	0	0
Total liabilities	60	16
MGE [Member] | Level 1 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	132	143
MGE [Member] | Level 2 [Member]
Assets:
Derivatives	0	0
Total Assets	0	0
Liabilities:
Derivatives	0	0
Deferred compensation	3,014	3,039
Total liabilities	3,014	3,039
MGE [Member] | Level 2 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	0	0
MGE [Member] | Level 3 [Member]
Assets:
Derivatives	478	486
Total Assets	478	486
Liabilities:
Derivatives	48,832	50,792
Deferred compensation	0	0
Total liabilities	48,832	50,792
MGE [Member] | Level 3 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	$ 0	$ 0