Fair Value of Financial Instruments (Details-2) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Assets:
Available-for-sale securities	$ 2,365		$ 1,733
Liabilities:
Derivative asset, collateral offset	200		0
Recurring [Member]
Assets:
Total Assets	792		320
Liabilities:
Derivatives, net	63,893	[1]	72,329
Deferred compensation	2,364		2,010
Total Liabilities	66,257		74,339
Recurring [Member] | Exchange-traded investments
Assets:
Available-for-sale securities	792		320
Recurring [Member] | Level 1 [Member]
Assets:
Total Assets	792		320
Liabilities:
Derivatives, net	(735)	[1]	(17)
Deferred compensation	0		0
Total Liabilities	(735)		(17)
Recurring [Member] | Level 1 [Member] | Exchange-traded investments
Assets:
Available-for-sale securities	792		320
Recurring [Member] | Level 2 [Member]
Assets:
Total Assets	0		0
Liabilities:
Derivatives, net	0	[1]	0
Deferred compensation	2,364		2,010
Total Liabilities	2,364		2,010
Recurring [Member] | Level 2 [Member] | Exchange-traded investments
Assets:
Available-for-sale securities	0		0
Recurring [Member] | Level 3 [Member]
Assets:
Total Assets	0		0
Liabilities:
Derivatives, net	64,628	[1]	72,346
Deferred compensation	0		0
Total Liabilities	64,628		72,346
Recurring [Member] | Level 3 [Member] | Exchange-traded investments
Assets:
Available-for-sale securities	0		0
MGE [Member]
Assets:
Available-for-sale securities	811		497
Liabilities:
Derivative asset, collateral offset	200
MGE [Member] | Recurring [Member]
Assets:
Total Assets	431		117
Liabilities:
Derivatives, net	63,893	[1]	72,329
Deferred compensation	2,364		2,010
Total Liabilities	66,257		74,339
MGE [Member] | Recurring [Member] | Exchange-traded investments
Assets:
Available-for-sale securities	431		117
MGE [Member] | Recurring [Member] | Level 1 [Member]
Assets:
Total Assets	431		117
Liabilities:
Derivatives, net	(735)	[1]	(17)
Deferred compensation	0		0
Total Liabilities	(735)		(17)
MGE [Member] | Recurring [Member] | Level 1 [Member] | Exchange-traded investments
Assets:
Available-for-sale securities	431		117
MGE [Member] | Recurring [Member] | Level 2 [Member]
Assets:
Total Assets	0		0
Liabilities:
Derivatives, net	0	[1]	0
Deferred compensation	2,364		2,010
Total Liabilities	2,364		2,010
MGE [Member] | Recurring [Member] | Level 2 [Member] | Exchange-traded investments
Assets:
Available-for-sale securities	0		0
MGE [Member] | Recurring [Member] | Level 3 [Member]
Assets:
Total Assets	0		0
Liabilities:
Derivatives, net	64,628	[1]	72,346
Deferred compensation	0		0
Total Liabilities	64,628		72,346
MGE [Member] | Recurring [Member] | Level 3 [Member] | Exchange-traded investments
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.