Revenues Narrative (Details)	3 Months Ended
Mar. 31, 2018
Recovery period per ASC 980-605-25 \| Maximum
Disaggregation of Revenue [Line Items]
Surcharge Or Refund Period	24 months
Retail
Disaggregation of Revenue [Line Items]
Customer Payment Terms	16 days
Wholesale
Disaggregation of Revenue [Line Items]
Number Of Customers	1
Wholesale \| Maximum
Disaggregation of Revenue [Line Items]
Customer Payment Terms	10 days
Transmission \| Maximum
Disaggregation of Revenue [Line Items]
Customer Payment Terms	20 days
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year

Amount of time, in days, that customers have to pay the Company for services provided

No definition available.

Name:	ee_CustomerPaymentTerms
Namespace Prefix:	ee_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of customers.

+ References

No definition available.

+ Details

Name:	ee_NumberOfCustomers
Namespace Prefix:	ee_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Time period given to public utility (by regulatory agency) to surcharge or to refund customers, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	ee_SurchargeOrRefundPeriod
Namespace Prefix:	ee_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DisaggregationOfRevenueLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Period in which remaining performance obligation is expected to be recognized as revenue, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130556-203045

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 270
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=84173487&loc=SL51747714-108306

+ Details

Name:	us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_RegulatoryAssetAxis=ee_RecoveryperiodperASC98060525Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorCustomersAxis=ee_RetailMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorCustomersAxis=ee_WholesaleMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorCustomersAxis=ee_TransmissionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: