Fair Value of Financial Instruments (Details-2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Liabilities:
Derivative asset, collateral offset		$ 200
Recurring [Member]
Assets:
Total Assets	804	792
Liabilities:
Derivatives, net	58,213	63,893	[1]
Deferred compensation	2,472	2,364
Total liabilities	60,685	66,257
Recurring [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	804	792
Recurring [Member] | Level 1 [Member]
Assets:
Total Assets	804	792
Liabilities:
Derivatives, net	(584)	(735)	[1]
Deferred compensation	0	0
Total liabilities	(584)	(735)
Recurring [Member] | Level 1 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	804	792
Recurring [Member] | Level 2 [Member]
Assets:
Total Assets	0	0
Liabilities:
Derivatives, net	0	0	[1]
Deferred compensation	2,472	2,364
Total liabilities	2,472	2,364
Recurring [Member] | Level 2 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	0	0
Recurring [Member] | Level 3 [Member]
Assets:
Total Assets	0	0
Liabilities:
Derivatives, net	58,797	64,628	[1]
Deferred compensation	0	0
Total liabilities	58,797	64,628
Recurring [Member] | Level 3 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	0	0
MGE [Member]
Liabilities:
Derivative asset, collateral offset		200
MGE [Member] | Recurring [Member]
Assets:
Total Assets	461	431
Liabilities:
Derivatives, net	58,213	63,893	[1]
Deferred compensation	2,472	2,364
Total liabilities	60,685	66,257
MGE [Member] | Recurring [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	461	431
MGE [Member] | Recurring [Member] | Level 1 [Member]
Assets:
Total Assets	461	431
Liabilities:
Derivatives, net	(584)	(735)	[1]
Deferred compensation	0	0
Total liabilities	(584)	(735)
MGE [Member] | Recurring [Member] | Level 1 [Member] | Exchange Traded [Member]
Assets:
Available-for-sale securities	461	431
MGE [Member] | Recurring [Member] | Level 2 [Member]
Assets:
Total Assets	0	0
Liabilities:
Derivatives, net	0	0	[1]
Deferred compensation	2,472	2,364
Total liabilities	2,472	2,364
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:
Total Assets	0	0
Liabilities:
Derivatives, net	58,797	64,628	[1]
Deferred compensation	0	0
Total liabilities	58,797	64,628
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 $0.2 million of collateral that was posted against derivative positions with counterparties.