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Current regulatory liability

1,570

1,793

^[2]

Total regulatory liabilities

1,263

530

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

$ 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]

Other Regulatory Assets (Liabilities) [Member]

Schedule Of Regulatory Assets And Liabilities [Line Items]

Excess deferred income taxes [Member]

^[3]

Schedule Of Regulatory Assets And Liabilities [Line Items]

Excess deferred income taxes [Member]

^[4]

Schedule Of Regulatory Assets And Liabilities [Line Items]

Schedule Of Regulatory Assets And Liabilities [Line Items]

^[4]

862

Removal Costs [Member]

Other Regulatory Assets (Liabilities) [Member]

285

345

Schedule Of Regulatory Assets And Liabilities [Line Items]

Hurricane Harvey [Member]

116

185

Schedule Of Regulatory Assets And Liabilities [Line Items]

Estimated storm restoration costs

^[5]

$ 0

120

Estimated storm restoration costs covered by insurance

Property, plant and equipment

Insurance proceeds received

(11)

Net property, plant and equipment

Operation and maintenance expense

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.

Employee Benefit Plans Pension and Postretirement Benefits (Details) - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Defined Benefit Plan Disclosure [Line Items]

Percentage of eligible earnings used to determine retirement benefits

5.00%

Recognized pension expense

$ 41

$ 44

$ 35

Non-qualified pension plan expense

$ 1

Maximum percentage of employee compensation eligible for contribution to savings plan

50.00%

Description of company match under savings plan

100.00%

Employer matching contribution percentage of employee's gross pay

6.00%

Savings plan benefit expense

$ 17

$ 14

Components of net periodic costs [Abstract]

Assumptions used to determine net periodic benefit (income) cost [Abstract]

$ 9

$ 10

Discount rate

4.15%

4.35%

3.90%

Expected long-term return on assets

4.75%

5.00%

5.45%

Change in Benefit Obligation

Accumulated benefit obligation, beginning of year

$ 217

$ 283

Participant contributions

Benefits paid

(14)

(20)

Medicare drug reimbursement

Plan amendment (1)

^[1]

(65)

Actuarial loss

Accumulated benefit obligation, end of year

$ 225

$ 217

225

217

$ 283

Change in Plan Assets

Plan assets, beginning of year

110

Benefits paid

(14)

(20)

Employer contributions

Participant contributions

Actual investment return

Plan amendment (2)

^[2]

(20)

Plan assets, end of year

$ 110

Amounts Recognized in Balance Sheets

Other liabilities-benefit obligations

$ (146)

$ (148)

$ (146)

$ (148)

Actuarial Assumptions

Discount rate

3.60%

4.15%

3.60%

4.15%

Expected long-term return on assets

4.75%

5.00%

5.45%

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%

Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rates [Abstract]

Effect of One Percentage Point Increase on Postretirement Benefit Obligation

$ 9

Effect of One Percentage Point Decrease on Postretirement Benefit Obligation

Effect of One Percentage Point Increase on Total Service and Interest Cost

Effect of One Percentage Point Decrease on Total Service and Interest Cost

$ 0

Annualized individual discount rates based on time period, minimum

6 months

Annualized individual discount rates based on time period, maximum

99 years

Other Postretirement Benefit Plans, Defined Benefit [Member]

Components of net periodic costs [Abstract]

$ 1

Expected return on plan assets

(4)

(5)

(6)

Amortization of prior service credit

(6)

(4)

(2)

Amortization of loss

Curtailment

(4)

Net postretirement benefit cost (credit)

(1)

Change in Benefit Obligation

Amounts Recognized in Balance Sheets

$ 13

Other liabilities-benefit obligations

$ (132)

$ (129)

(132)

(129)

Net liability, end of year

$ (132)

$ (129)

$ (132)

$ (129)

Maximum [Member]

Actuarial Assumptions

Healthcare cost trend rate assumed for the next year

23.85%

10.65%

23.85%

10.65%

Year that the cost trend rates reach the ultimate trend rate

2024

Minimum [Member]

Actuarial Assumptions

Healthcare cost trend rate assumed for the next year

6.15%

5.75%

6.15%

5.75%

Prescription drug cost trend rate assumed for the next year - Pre-65

9.85%

Year that the cost trend rates reach the ultimate trend rate

2026

2024

CenterPoint Energy [Member] | Common Stock [Member]

Defined Benefit Plan Disclosure [Line Items]

Maximum percentage limit of account balance in company stock

25.00%

Number of shares in common stock held by savings plan

12,806,085

Percentage of investment in common stocks

16.00%

[1]

[2]

Employee Benefit Plans Plan Assets (Details) - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]

Postemployment benefit expense

$ 93

$ 88

$ 110

Postemployment Benefits [Abstract]

Postemployment benefit credit

(1)

Defined Benefit Plan [Abstract]

Benefit expense related to deferred compensation plans

$ 1

Equity Funds [Member]

Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]

Fair Value, Inputs, Level 1 [Member]

^[1]

^[2]

Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]

Fair Value, Inputs, Level 1 [Member] | Equity Funds [Member]

Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]

Fair Value, Inputs, Level 2 [Member]

^[1]

^[2]

Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]

Fair Value, Inputs, Level 2 [Member] | Equity Funds [Member]

Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]

Fair Value, Inputs, Level 3 [Member]

^[1]

^[2]

Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]

Fair Value, Inputs, Level 3 [Member] | Equity Funds [Member]

Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]

Other Postretirement Benefit Plans, Defined Benefit [Member]

^[1]

$ 0

^[2]

Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]

Estimated future contributions in the next fiscal year

Expected Future Benefit Payments, Fiscal Year Maturity [Abstract]

Postretirement benefit payments - 2018

Postretirement benefit payments - 2019

Postretirement benefit payments - 2020

Postretirement benefit payments - 2021

Postretirement benefit payments - 2022

Postretirement benefit payments - 2023-2027

$ 85

International Equity [Member] | Equity Funds [Member]

Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]

Actual plan asset allocations

8.00%

Fixed Income Funds [Member] | Equity Funds [Member]

Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]

Actual plan asset allocations

74.00%

73.00%

U.S. Equity [Member] | Equity Funds [Member]

Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]

Actual plan asset allocations

18.00%

19.00%

Benefit Obligation [Member]

Postemployment Benefits [Abstract]

Postemployment benefit obligations

$ 3

$ 6

Defined Benefit Plan [Abstract]

Other non-qualified plans benefit obligations deferred compensation

$ 10

$ 11

Minimum [Member] | U.S. Equity [Member]

Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]

Postretirement benefit plan asset allocation percentage

0.13

Minimum [Member] | International Equity [Member]

Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]

Postretirement benefit plan asset allocation percentage

0.03

Minimum [Member] | Fixed Income [Member]

Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]

Postretirement benefit plan asset allocation percentage

0.69

Minimum [Member] | Cash and Cash Equivalents [Member]

Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]

Postretirement benefit plan asset allocation percentage

Maximum [Member] | U.S. Equity [Member]

Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]

Postretirement benefit plan asset allocation percentage

0.23

Maximum [Member] | International Equity [Member]

Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]

Postretirement benefit plan asset allocation percentage

0.13

Maximum [Member] | Fixed Income [Member]

Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]

Postretirement benefit plan asset allocation percentage

0.79

Maximum [Member] | Cash and Cash Equivalents [Member]

Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]

Postretirement benefit plan asset allocation percentage

0.02

[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.
[2]	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.

Employee Benefit Plans Other Employee Matters (Details)	12 Months Ended
Employee Benefit Plans Other Employee Matters (Details)	Dec. 31, 2017 employee
Concentration Risk [Line Items]
Number of full-time employees	2,816
Employees Subject To Collective Bargaining Agreements [Member] \| Labor Force Concentration Risk [Member] \| Number of Employees [Member]
Concentration Risk [Line Items]
Concentration risk percentage	52.00%

Fair Value Measurements (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Fair Value Assets and Liabilities Measured on Recurring Basis Disclosure Items [Line Items]
Fair value amount of Level 1 into Level 2 (Asset)	$ 0
Fair value amount of Level 2 into Level 1 (Asset)	0
Fair value amount of Level 1 into Level 2 (Liability)	0
Fair value amount of Level 2 into Level 1 (Liability)	0
Carrying Amount [Member]
Fair Value Assets and Liabilities Measured on Recurring Basis Disclosure Items [Line Items]
Long-term debt, including current portion	4,753,000,000	$ 4,865,000,000
Fair Value [Member]
Fair Value Assets and Liabilities Measured on Recurring Basis Disclosure Items [Line Items]
Long-term debt, including current portion	5,034,000,000	5,079,000,000
Fair Value, Inputs, Level 1 [Member]
Fair Value Assets and Liabilities Measured on Recurring Basis Disclosure Items [Line Items]
Investments, including money market funds	51,000,000	59,000,000
Fair Value, Inputs, Level 2 [Member]
Fair Value Assets and Liabilities Measured on Recurring Basis Disclosure Items [Line Items]
Assets or liabilities	0	0
Fair Value, Inputs, Level 3 [Member]
Fair Value Assets and Liabilities Measured on Recurring Basis Disclosure Items [Line Items]
Assets or liabilities	$ 0	$ 0

Related Party Transactions and Major Customers (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Money Pool Borrowings	$ 60								$ 60
Investments in Money Pool					$ 96					$ 96
Weighted average interest rate	1.90%								1.90%
Affiliate related net interest income (expense)									$ 2	(4)	$ (1)
Cash dividends paid to parent company									180	135	252
Proceeds from contributions from parent									0	374	0
Revenues	$ 765	$ 843	$ 752	$ 638	$ 731	$ 909	$ 763	$ 656	2,998	3,059	2,846
Affiliates of NRG Energy, Inc. [Member]
Related Party Transaction [Line Items]
Revenues									713	698	741
Affiliates of Vistra Energy Corp. [Member]
Related Party Transaction [Line Items]
Revenues									229	220	220
Operation And Maintenance Expense [Member] \| CenterPoint Energy [Member]
Related Party Transaction [Line Items]
Corporate service charges									188	179	176
Operation And Maintenance Expense [Member] \| CERC Corp [Member]
Related Party Transaction [Line Items]
Corporate service charges									8	7	6
Other revenues from transactions with related party									$ (17)	$ (15)	$ (18)

Long-term Debt (Details)
$ in Millions

12 Months Ended

Jan. 12, 2017

USD ($)

Dec. 31, 2017

USD ($)

Jan. 02, 2018

USD ($)

Dec. 31, 2016

USD ($)

Unamortized debt issuance costs

$ (22.0)

$ (23.0)

Unamortized discount and premium, net

(10.0)

(9.0)

Long-term Debt, Excluding Current Maturities

4,319.0

4,454.0

Long-term Debt, Current Maturities

^[1]

434.0

411.0

Size of Credit Facility

300.0

First mortgage bonds 9.15% due 2021

2018

^[2]

434.0

2019

^[2]

458.0

2020

^[2]

231.0

2021

^[2]

613.0

2022

^[2]

519.0

102.0

^[1]

$ 0.0

0.0

9.15%

Replacement fund requirements

Secured debt

$ 102.0

266.0

Sinking fund requirements

1.6

General mortgage bonds 1.85% to 6.95% due 2021 to 2044 (2)

^[3]

2,812.0

2,512.0

^[1],[3]

0.0

System restoration bonds 3.46% to 4.243% due 2018 to 2022

Secured debt

2,900.0

256.0

312.0

Transition bonds 2.161% to 5.302% due 2019 to 2024

^[1]

56.0

53.0

1,181.0

1,560.0

Bonds General Mortgage Due 2027 [Member]

^[1]

378.0

358.0

Aggregate principal amount

$ 300.0

Transition And System Restoration Bonds [Member]

3.00%

Maturity date

Feb. 01, 2027

Revolving Credit Facility [Member]

434.0

458.0

231.0

211.0

219.0

Loans Outstanding

$ 0.0

0.0

Line of Credit [Member]

Percentage on limitation of debt to total capitalization under covenant (in hundredths)

^[4]

65.00%

Ratio of indebtedness to net capital

^[5]

0.486

Percentage on limitation of debt to total capitalization under covenant amended (in hundredths)

70.00%

Restoration cost expected cost

$ 100.0

Consecutive period for system restoration costs to exceed $100 million (in months)

Letter of Credit [Member]

London Interbank Offered Rate (LIBOR) [Member] | Line of Credit [Member]

Loans Outstanding

$ 4.0

Line of credit facility interest rate description

^[6]

1.125%

January thru February [Member] | Treasury Lock [Member] | Subsequent Event [Member]

Aggregate notional amount

$ 200.0

January [Member] | Treasury Lock [Member]

Aggregate principal amount

$ 300.0

Aggregate notional amount

150.0

Effective portion of realized losses

$ 1.0

Minimum [Member] | General mortgage bonds 1.85% to 6.95% due 2021 to 2044 (2)

Minimum [Member] | System restoration bonds 3.46% to 4.243% due 2018 to 2022

1.85%

Minimum [Member] | Transition bonds 2.161% to 5.302% due 2019 to 2024

3.46%

Maximum [Member] | General mortgage bonds 1.85% to 6.95% due 2021 to 2044 (2)

2.161%

Maximum [Member] | System restoration bonds 3.46% to 4.243% due 2018 to 2022

6.95%

Maximum [Member] | Transition bonds 2.161% to 5.302% due 2019 to 2024

4.243%