Consolidated Balance Sheets (Parentheticals) - USD ($) shares in Thousands, $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Receivables, Net
Reserve for uncollectible accounts receivable	$ 2,840	$ 3,017
Reserve for uncollectible other accounts receivable	$ 335	$ 426
Common shareholders' equity
Common stock, par value	$ 1	$ 1
Common stock, shares authorized	75,000	75,000
Common stock, shares issued	34,668	34,668
Common stock, shares outstanding	34,668	34,668
MGE [Member]
Receivables, Net
Reserve for uncollectible accounts receivable	$ 2,840	$ 3,017
Reserve for uncollectible other accounts receivable	$ 335	$ 426
Common shareholders' equity
Common stock, par value	$ 1	$ 1
Common stock, shares authorized	50,000	50,000
Common stock, shares outstanding	17,348	17,348