Variable Interest Entities (Narrative) (Details) - Grand Gulf [Member] - System Energy [Member] - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Variable Interest Entity [Line Items]
Payments on lease, including interest	$ 8.6	$ 8.6
Percentage in power plant owned by VIE	11.50%

Percentage of the VIE's voting interest owned by the registrant. In general, a VIE is a corporation, partnership, trust, or any other legal structure used for business purposes that either (a) does not have equity investors with voting rights or (b) has equity investors that do not provide sufficient financial resources for the entity to support its activities. A VIE often holds financial assets, including loans or receivables, real estate or other property. A VIE may be essentially passive or it may engage in research and development or other activities on behalf of another company.

No definition available.

Name:	etr_PercentageInPowerPlantOwnedByVie
Namespace Prefix:	etr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration