Fair Value of Financial Instruments (Details-2) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Liabilities:
Derivative liability, collateral offset		$ 1,000
Recurring [Member]
Assets:
Derivative assets, net	$ 1,367	234
Total Assets	1,887	993
Liabilities:
Derivative liabilities, net	50,938	54,316	[1]
Deferred compensation	2,963	3,145
Total liabilities	53,901	57,461
Recurring [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	520	759
Recurring [Member] | Level 1 [Member]
Assets:
Derivative assets, net	917	0
Total Assets	1,437	759
Liabilities:
Derivative liabilities, net	59	581	[1]
Deferred compensation	0	0
Total liabilities	59	581
Recurring [Member] | Level 1 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	520	759
Recurring [Member] | Level 2 [Member]
Assets:
Derivative assets, net	0	0
Total Assets	0	0
Liabilities:
Derivative liabilities, net	0	0	[1]
Deferred compensation	2,963	3,145
Total liabilities	2,963	3,145
Recurring [Member] | Level 2 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	0	0
Recurring [Member] | Level 3 [Member]
Assets:
Derivative assets, net	450	234
Total Assets	450	234
Liabilities:
Derivative liabilities, net	50,879	53,735	[1]
Deferred compensation	0	0
Total liabilities	50,879	53,735
Recurring [Member] | Level 3 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	0	0
MGE [Member]
Liabilities:
Derivative liability, collateral offset		1,000
MGE [Member] | Recurring [Member]
Assets:
Derivative assets, net	1,367	234
Total Assets	1,464	382
Liabilities:
Derivative liabilities, net	50,938	54,316	[1]
Deferred compensation	2,963	3,145
Total liabilities	53,901	57,461
MGE [Member] | Recurring [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	97	148
MGE [Member] | Recurring [Member] | Level 1 [Member]
Assets:
Derivative assets, net	917	0
Total Assets	1,014	148
Liabilities:
Derivative liabilities, net	59	581	[1]
Deferred compensation	0	0
Total liabilities	59	581
MGE [Member] | Recurring [Member] | Level 1 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	97	148
MGE [Member] | Recurring [Member] | Level 2 [Member]
Assets:
Derivative assets, net	0	0
Total Assets	0	0
Liabilities:
Derivative liabilities, net	0	0	[1]
Deferred compensation	2,963	3,145
Total liabilities	2,963	3,145
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:
Derivative assets, net	450	234
Total Assets	450	234
Liabilities:
Derivative liabilities, net	50,879	53,735	[1]
Deferred compensation	0	0
Total liabilities	50,879	53,735
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 $1.0 million of collateral that was posted against derivative positions with counterparties as of December 31, 2015.