Regulatory Accounting (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Regulatory Assets And Liabilities [Line Items]
Securitized regulatory assets		$ 1,590	$ 1,919
Unrecognized equity return (1)	[1]	(287)	(329)
Unamortized loss on reacquired debt		75	84
Regulatory assets		1,570	1,793
Current regulatory liability	[2]	22	7
Non-current regulatory liabilities		1,263	530
Total regulatory liabilities		1,285	537
Total regulatory assets and liabilities, net		285	1,256
Amount of allowed equity return on the true-up balance that was recognized in the period		42	64	$ 49
Property, plant and equipment		11,496	10,840
Net property, plant and equipment		7,863	7,397
Pension and Other Postretirement Plans Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets		31	34
Other Regulatory Assets (Liabilities) [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	[3]	70	85
Excess deferred income taxes [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	[4]	33	0
Excess deferred income taxes [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Non-current regulatory liabilities	[4]	862	0
Removal Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Non-current regulatory liabilities		285	345
Other Regulatory Assets (Liabilities) [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Non-current regulatory liabilities		116	185
Hurricane Harvey [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	[5]	58	$ 0
Estimated storm restoration costs		120
Estimated storm restoration costs covered by insurance		28
Property, plant and equipment		42
Insurance proceeds received		(11)
Net property, plant and equipment		31
Operation and maintenance expense		75
Insurance proceeds received		(3)
Insurance receivable		$ (14)

[1] The unrecognized allowed equity return will be recognized as it is recovered in rates through 2024. During the years ended December 31, 2017, 2016 and 2015, Houston Electric recognized approximately $42 million, $64 million and $49 million, respectively, of the allowed equity return. The timing of Houston Electric’s recognition of the allowed equity return will vary each period based on amounts actually collected during the period. The actual amounts recognized are adjusted at least annually to correct any over-collections or under-collections during the preceding 12 months.

[2] Current regulatory liabilities are included in Other current liabilities in Houston Electric’s Consolidated Balance Sheets.

[3] Other long-term regulatory assets that are not earning a return were not material as of December 31, 2017 and 2016.

[4] EDIT will be recovered or refunded to customers as required by tax and regulatory activities. See Note 9 for additional information.

[5] Houston Electric is not earning a return on its Hurricane Harvey restoration costs.