Commitments and Contingencies (Details-1) (Columbia Units [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2014
Columbia Units [Member]
Columbia Commitments [Abstract]
Accrual for future environmental mitigation projects	$ 0.6
Envrionmental civil penalty expense	$ 0.2

Accrual for future environmental mitigation projects as a result of environmental regulation violations.

No definition available.

Name:	mgee_AccrualForFutureEnvironmentalMitigationProjects
Namespace Prefix:	mgee_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant