Summary of Significant Accounting Policies (Details)	3 Months Ended
Mar. 31, 2012 town segment
Summary of Significant Accounting Policies
Number of business segments	3
Number of towns to which water service is provided	3

Represents the number of towns to which the entity provides water service.

No definition available.

Name:	ede_NumberOfTownsToWhichEntityProvidesWaterService
Namespace Prefix:	ede_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration