New Accounting Standards (Details-1) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 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)	$ (377)
Cumulative Effect of New Accounting Principle in Period of Adoption	377	377
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	28
Cumulative Effect of New Accounting Principle in Period of Adoption	(28)	(28)
Accounting Standards Update 2017-07 - Compensation - Retirement Benefits [Member]
Adoption of Accounting Principles and Recently Issued Accounting Pronouncements [Line Items]
Effect of New Accounting Principle on Prior Period Presentation	1,000	3,000
Accounting Standards Update 2017-07 - Compensation - Retirement Benefits [Member] | MGE [Member]
Adoption of Accounting Principles and Recently Issued Accounting Pronouncements [Line Items]
Effect of New Accounting Principle on Prior Period Presentation	$ 1,000	$ 3,000