Notes Payable to Banks, Commercial Paper, and Lines of Credit (Details) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Short-term Debt [Line Items]
Maximum short-term borrowings	$ 32,000,000	[1]	$ 16,000,000	[1]	$ 28,500,000	[1]
Average short-term borrowings	6,992,000	[1]	1,154,000	[1]	3,410,000	[1]
Weighted-average interest rate during the year	0.18%	[1]	0.17%	[1]	1.43%	[1]
Line of Credit [Member]
Short-term Debt [Line Items]
Available lines of credit	150,000,000	[1]	115,000,000	[1]	115,000,000	[1]
MGE [Member]
Short-term Debt [Line Items]
Maximum short-term borrowings	32,000,000		16,000,000		9,500,000
Average short-term borrowings	6,992,000		1,154,000		349,000
Weighted-average interest rate during the year	0.18%		0.17%		0.25%
MGE [Member] | Line of Credit [Member]
Short-term Debt [Line Items]
Available lines of credit	100,000,000		75,000,000		75,000,000
MGE [Member] | Line of Credit [Member] | MGE $100 million unsecured committed revolving line of credit
Short-term Debt [Line Items]
Available lines of credit	100,000,000
Line of credit, borrowings outstanding	0
Debt covenant, required parent company ownership of MGE	100.00%
MGE [Member] | Line of Credit [Member] | MGE $100 million unsecured committed revolving line of credit | Minimum [Member]
Short-term Debt [Line Items]
Debt covenant, ownership interest by outside party resulting in repurchase of notes at par value	30.00%
MGE [Member] | Line of Credit [Member] | MGE $100 million unsecured committed revolving line of credit | Maximum [Member]
Short-term Debt [Line Items]
Debt to total capitalization ratio	0.65
MGE Energy [Member] | Line of Credit [Member] | MGE Energy $50 million unsecured commiteed revolving line of credit
Short-term Debt [Line Items]
Available lines of credit	50,000,000
Line of credit, borrowings outstanding	$ 0
Debt covenant, required parent company ownership of MGE	100.00%
MGE Energy [Member] | Line of Credit [Member] | MGE Energy $50 million unsecured commiteed revolving line of credit | Minimum [Member]
Short-term Debt [Line Items]
Debt covenant, ownership interest by outside party resulting in repurchase of notes at par value	30.00%
MGE Energy [Member] | Line of Credit [Member] | MGE Energy $50 million unsecured commiteed revolving line of credit | Maximum [Member]
Short-term Debt [Line Items]
Debt to total capitalization ratio	0.65

[1] MGE Energy short-term borrowings include MGE Energy and MGE lines of credit and MGE commercial paper.