New Accounting Standards (Details-1) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Adoption of Accounting Principles and Recently Issued Accounting Pronouncements [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption		$ 0
MGE [Member]
Adoption of Accounting Principles and Recently Issued Accounting Pronouncements [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption		$ 0
Accounting Standards Update 2016-01 - Financial Instruments - Overall [Member]
Adoption of Accounting Principles and Recently Issued Accounting Pronouncements [Line Items]
Accumulated other comprehensive income (loss)	$ (377,000)
Cumulative Effect of New Accounting Principle in Period of Adoption	377,000
Accounting Standards Update 2016-01 - Financial Instruments - Overall [Member] | MGE [Member]
Adoption of Accounting Principles and Recently Issued Accounting Pronouncements [Line Items]
Accumulated other comprehensive income (loss)	28,000
Cumulative Effect of New Accounting Principle in Period of Adoption	(28,000)
Accounting Standards Update 2017-07 - Compensation - Retirement Benefits [Member]
Adoption of Accounting Principles and Recently Issued Accounting Pronouncements [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	1,100,000
Accounting Standards Update 2017-07 - Compensation - Retirement Benefits [Member] | MGE [Member]
Adoption of Accounting Principles and Recently Issued Accounting Pronouncements [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 1,100,000