Background and Basis of Presentation (Details) customer in Millions	Sep. 30, 2017 customer
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of metered customers	2.4

The number of metered customers the entity serves.

No definition available.

Name:	cehe_NumberofMeteredCustomers
Namespace Prefix:	cehe_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant