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Summary of Significant Accounting Policies (Details) (USD $)	0 Months Ended	12 Months Ended
	Dec. 20, 2013	Dec. 31, 2013 sqmi	Dec. 31, 2012	Dec. 31, 2011
Basis of Presentation
Stock split declared December 20, 2013, ratio (3:2)	1.5
Receivable - Margin Account [Abstract]
Derivative asset, collateral offset		$ 200,000	$ 0
Trade Receivables, Allowance for Doubtful Accounts, and Concentration Risk
Late payment charge on upaid receivables		1.00%
Electric territory (in square miles)		316
Gas territory (in square miles)		1,649
Inventories
Emissions allowance included in inventory		100,000	100,000
Renewable energy credit allowance included in inventory		600,000	500,000
Purchased Gas Adjustment Clause
Purchased gas adjustment, over (under) collected		1,700,000	(100,000)
Allowance for Funds Used During Construction
Authorized AFUDC rate		50.00%	50.00%	50.00%
Rate at which AFUDC was capitalized		8.21%	8.36%	8.36%
Capitalized Software Costs
Capitalized software		20,900,000	14,500,000
Capitalized software amortization		1,500,000	1,300,000
Impairment of Long-Lived Assets
Impairment of long-lived assets		0	0	0
Excise taxes
License fee tax rate, electric, retail sales		3.19%
License fee tax rate, electric, resale by purchaser		1.59%
License fee tax rate, natural gas		0.97%
License fee tax expense		$ 13,800,000	$ 13,500,000	$ 12,900,000
Treasury Stock
Treasury stock outstanding (in shares)		0
Minimum [Member] \| Capitalized Software [Member]
Capitalized Software Costs
Property, plant, and equipment, useful life		5 years
Maximum [Member] \| Capitalized Software [Member]
Capitalized Software Costs
Property, plant, and equipment, useful life		10 years
Columbia Environmental Project [Member] \| PSCW [Member]
Allowance for Funds Used During Construction
Authorized AFUDC rate		50.00%	100.00%	100.00%
Electric [Member]
Property, Plant, and Equiptment
Composite straight-line depreciation rates		2.70%	2.90%	3.20%
Gas [Member]
Property, Plant, and Equiptment
Composite straight-line depreciation rates		1.70%	1.70%	1.60%
Non Regulated Energy [Member]
Property, Plant, and Equiptment
Composite straight-line depreciation rates		2.30%	2.30%	2.30%
MGE Power Elm Road [Member]
Principles of Consolidation
Ownership percentage by parent		100.00%
MGE Power West Campus [Member]
Principles of Consolidation
Ownership percentage by parent		100.00%