XML 23 R1.htm IDEA: XBRL DOCUMENT v3.3.1.900
Document and Entity Information - USD ($)
12 Months Ended
Dec. 31, 2015
Feb. 01, 2016
Jun. 30, 2015
Document and Entity Information [Line Items]      
Entity Registrant Name MGE Energy Inc    
Entity Central Index Key 0001161728    
Document Type 10-K    
Document Period End Date Dec. 31, 2015    
Amendment Flag false    
Trading Symbol MGEE    
Document Fiscal Year Focus 2015    
Document Fiscal Period Focus FY    
Current Fiscal Year End Date --12-31    
Entity Well known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Filer Category Large Accelerated Filer    
Entity Public Float     $ 1,338,879,665
Entity Common Stock Shares Outstanding   34,668,370  
MGE [Member]      
Document and Entity Information [Line Items]      
Entity Registrant Name Madison Gas and Electric Company    
Entity Central Index Key 0000061339    
Entity Well known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Filer Category Non-accelerated Filer    
Entity Common Stock Shares Outstanding   17,347,894