Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2017

Retirement Benefits [Abstract]

Schedule of Defined Benefit Plans Disclosures [Table Text Block]

Following are reconciliations of Houston Electric’s beginning and ending balances of its postretirement benefit plan’s benefit obligation, plan assets and funded status for 2017 and 2016.  The measurement dates for plan assets and obligations were December 31, 2017 and 2016.

	December 31,
	2017			2016
	(in millions)
Change in Benefit Obligation
Accumulated benefit obligation, beginning of year	$	217		$	283
Service cost	1			1
Interest cost	9			10
Benefits paid	(14		)	(20		)
Participant contributions	2			3
Medicare drug reimbursement	—			1
Plan amendment (1)	—			(65		)
Actuarial loss	10			4
Accumulated benefit obligation, end of year	$	225		$	217
Change in Plan Assets
Plan assets, beginning of year	$	88		$	110
Benefits paid	(14		)	(20		)
Employer contributions	10			10
Participant contributions	2			3
Actual investment return	7			5
Plan amendment (2)	—			(20		)
Plan assets, end of year	$	93		$	88
Amounts Recognized in Balance Sheets
Other liabilities-benefit obligations	$	(132	)	$	(129	)
Net liability, end of year	$	(132	)	$	(129	)
Actuarial Assumptions
Discount rate	3.60		%	4.15		%
Expected long-term return on assets	4.75		%	4.75		%
Medical cost trend rate assumed for the next year - Pre-65	6.15		%	5.75		%
Medical/prescription drug cost trend rate assumed for the next year - Post-65	23.85		%	10.65		%
Prescription drug cost trend rate assumed for the next year - Pre-65	9.85		%	10.75		%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate)	4.50		%	4.50		%
Year that the cost trend rates reach the ultimate trend rate - Pre-65	2026			2024
Year that the cost trend rates reach the ultimate trend rate - Post-65	2024			2024

(1) The postretirement benefits were amended during 2016 to change retiree medical coverage, effective January 1, 2017, as follows: (i) members of the IBEW Local Union 66 who retire on or after January 1, 2017, and their dependents, will receive any retiree medical and prescription drug coverage exclusively through the NECA/IBEW Family Medical Care Plan pursuant to the terms of the renegotiated collective bargaining agreement entered into in May 2016; and (ii)  Medicare eligible post-65 retirees will receive coverage through a Medicare Advantage Program, an insured benefit, in lieu of the previous self-insured benefit.  These changes resulted in a reduction in our postretirement plan liability of $65 million as of December 31, 2016.

(2) In May 2016, Houston Electric entered into a renegotiated collective bargaining agreement with the IBEW Local Union 66. The Houston Lighting & Power Company Union Retirees’ Medical and Dental Benefits Trust was amended to reflect the renegotiated collective bargaining agreement by establishing a segregated and restricted account under the trust for the retiree medical benefits of post-2016 union retirees who are now covered exclusively by the NECA/IBEW Family Medical Care Plan. $20 million

As part of the investment strategy discussed above, Houston Electric has adopted and maintained the following asset allocation ranges for its postretirement benefit plans:

U.S. equity	13 – 23%
International developed market equity	3 – 13%
Fixed income	69 – 79%
Cash	0 – 2%

Houston Electric is required to fund a portion of its obligations in accordance with rate orders. The net postretirement benefit cost includes the following components:

	Year Ended December 31,
	2017			2016			2015
	(in millions)
Service cost - benefits earned during the period	$	1		$	1		$	1
Interest cost on accumulated benefit obligation	9			10			13
Expected return on plan assets	(4		)	(5		)	(6		)
Amortization of prior service credit	(6		)	(4		)	(2		)
Amortization of loss	—			1			3
Curtailment	—			(4		)	—
Net postretirement benefit cost (credit)	$	—		$	(1	)	$	9

Houston Electric used the following assumptions to determine net postretirement benefit costs:

	Year Ended December 31,
	2017		2016		2015
Discount rate	4.15	%	4.35	%	3.90	%
Expected return on plan assets	4.75	%	5.00	%	5.45	%

Houston Electric expects to contribute $10 million to its postretirement benefits plan in 2018. The following benefit payments are expected to be paid by the postretirement benefit plan: 

	Benefit Payments
	(in millions)
2018	$	11
2019	12
2020	14
2021	16
2022	17
2023-2027	85

Schedule of a one-percent point change In Assumed Health Care Cost Trend Rates [Table Text Block]

Assumed healthcare cost trend rates have a significant effect on the reported amounts for Houston Electric’s postretirement benefit plans. A 1% change in the assumed healthcare cost trend rate would have the following effects:

	1% Increase		1% Decrease
	(in millions)
Effect on postretirement benefit obligation	$	9	$	8
Effect on total of service and interest cost	—		—

Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Table Text Block]

The following tables present by level, within the fair value hierarchy, Houston Electric’s postretirement plan assets at fair value as of December 31, 2017 and 2016, by asset category as follows:

	Fair Value Measurements as of December 31, 2017
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Mutual funds (1)	$	93	$	—	$	—	$	93
Total	$	93	$	—	$	—	$	93

(1) 74% of the amount invested in mutual funds was in fixed income securities; 18% was in U.S. equities and 8% was in international equities.

	Fair Value Measurements as of December 31, 2016
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Mutual funds (1)	$	88	$	—	$	—	$	88
Total	$	88	$	—	$	—	$	88

(1) 73% of the amount invested in mutual funds was in fixed income securities; 19% was in U.S. equities and 8% was in international equities.