View Filing Data

Ownership percentage of equity method investment

54.00%

^[1]

Enable Midstream Partners [Member] | Series A Preferred Units [Member]

Preferred units held | shares

14,520,000

^[2]

Number of states in which entity operates

Number of states in which entity operates

[1]	Excluding the Series A Preferred Units owned by CenterPoint Energy.
[2]	The carrying amount of the Series A Preferred Units, reflected as Preferred units - unconsolidated affiliate on the Condensed Consolidated Balance Sheets, was $363 million as of both March 31, 2018 and December 31, 2017. No impairment charges or adjustment due to observable price changes were made during the current or prior reporting periods. See Note 2 for further discussion.

New Accounting Pronouncements (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accounting Standards Update 2016-15 [Member]
Effect of change on cash flow activities due to adoption of new ASU	$ 0	$ 2
Accounting Standards Update 2016-18 [Member]
Effect of change on cash flow activities due to adoption of new ASU	(2)	4
Accounting Standards Update 2017-07 [Member]
Increase to operating income and corresponding decrease to other net income from the adoption of ASU 2017-07	$ 14	$ 17

Revenue Recognition (Details) - USD ($)
$ in Millions

3 Months Ended

Mar. 31, 2018

Mar. 31, 2017

$ 2,126

$ 1,712

1,103

1,055

^[1]

(36)

(12)

Intersegment Eliminations [Member]

3,155

2,735

Electric Transmission and Distribution [Member]

(38)

(20)

Electric Transmission and Distribution [Member] | Intersegment Eliminations [Member]

^[2]

751

639

Natural Gas Distribution [Member] | Intersegment Eliminations [Member]

1,143

907

(10)

(9)

Energy Services [Member] | Intersegment Eliminations [Member]

1,257

1,185

Other Operations [Member]

(28)

(11)

Other Operations [Member] | Intersegment Eliminations [Member]

Reportable Subsegments [Member] | Intersegment Eliminations [Member]

^[3]

(10)

(9)

^[4]

(28)

(11)

Reportable Subsegments [Member] | Electric Transmission and Distribution [Member]

(38)

(20)

^[3]

761

644

^[3]

(4)

^[1],[3]

(6)

Reportable Subsegments [Member] | Natural Gas Distribution [Member]

^[3]

751

639

^[3]

1,186

925

^[3]

^[1],[3]

(33)

(9)

Reportable Subsegments [Member] | Energy Services [Member]

^[3]

1,143

907

^[4]

178

142

^[4]

1,107

1,054

^[1],[4]

Reportable Subsegments [Member] | Other Operations [Member]

^[4]

1,257

1,185

^[4]

^[4]

^[1],[4]

Defined Benefit Plan, Change in Accumulated Comprehensive Loss [Roll Forward]

^[4]

$ 4

[1]	Primarily consists of income from ARPs and leases. ARPs are contracts between the utility and its regulators, not between the utility and a customer. CenterPoint Energy recognizes ARP revenue as other revenues when the regulator-specified conditions for recognition have been met. Upon recovery of ARP revenue through incorporation in rates charged for utility service to customers, ARP revenue is reversed and recorded as revenue from contracts with customers. The recognition of ARP revenues and the reversal of ARP revenues upon recovery through rates charged for utility service may not occur in the same period.
[2]	Electric Transmission & Distribution revenues from major customers are as follows: Three Months Ended March 31, 2018 2017 (in millions)Affiliates of NRG $161 $152Affiliates of Vistra Energy Corp. 54 47
[3]	Reflected in Utility revenues in the Condensed Statements of Consolidated Income.
[4]	Reflected in Non-utility revenues in the Condensed Statements of Consolidated Income.

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

3 Months Ended

Mar. 31, 2018

Mar. 31, 2017

Beginning Balance

$ (66)

$ (72)

Amounts reclassified from accumulated other comprehensive loss:

Actuarial losses (1)

^[1]

Tax expense

(1)

Net current period other comprehensive income

Ending Balance

(65)

(71)

Pension Benefits [Member]

Total contributions expected in current year

Net periodic cost

Total contributions to the plans during the period

Postretirement Benefits [Member]

Total contributions expected in current year

Net periodic cost

Total contributions to the plans during the period

Operation and maintenance expense [Member] | Pension Benefits [Member]

Operation and maintenance expense [Member] | Postretirement Benefits [Member]

Service cost (1)

^[2]

Other, net [Member] | Pension Benefits [Member]

Service cost (1)

^[2]

Expected return on plan assets (2)

Interest cost (2)

^[3]

^[3]

(27)

(24)

Amortization of prior service cost (credit) (2)

^[3]

Amortization of net loss (2)

^[3]

Other, net [Member] | Postretirement Benefits [Member]

Expected return on plan assets (2)

Interest cost (2)

^[3]

^[3]

(1)

Amortization of prior service cost (credit) (2)

^[3]

(1)

Amortization of net loss (2)

^[3]

$ 0

[1]	These accumulated other comprehensive components are included in the computation of net periodic cost.
[2]	Included in Operation and maintenance expense in the Condensed Statements of Consolidated Income.
[3]	Included in Other, net in the Condensed Statements of Consolidated Income.

Regulatory Accounting (Details) - USD ($)
$ in Millions

3 Months Ended

Mar. 31, 2018

Mar. 31, 2017

Dec. 31, 2017

Securitized regulatory assets

$ 1,455

$ 1,590

Unrecognized equity return (2)

^[1]

(266)

(287)

Unamortized loss on reacquired debt

2,213

2,347

Total regulatory assets

2,278

2,477

Total regulatory liabilities

2,505

2,464

2,548

2,488

Total regulatory assets and liabilities, net

(270)

(11)

CenterPoint Houston [Member]

Amount of allowed equity return on the true-up balance that was recognized in the period

$ 7

Hurricane Harvey [Member]

Prepaid expenses and other current assets [Member]

^[2]

Current regulatory assets (1)

^[3]

130

Other current liabilities [Member]

Current regulatory liabilities (7)

^[4]

Pension and Other Postretirement Plans Costs [Member]

Amounts related to TCJA [Member]

^[5]

636

646

Other Regulatory Assets (Liabilities) [Member]

^[6]

Amounts related to TCJA [Member]

^[7]

202

211

^[6]

1,373

1,354

Removal Costs [Member]

Other Regulatory Assets (Liabilities) [Member]

882

878

Natural Gas Distribution [Member] | Pension and Other Postretirement Plans Costs [Member]

250

232

Remaining amounts of regulatory assets for which no return on investment during recovery period is provided

$ 6

$ 7

[1]	The unrecognized equity return will be recognized as it is recovered in rates through 2024. During the three months ended March 31, 2018 and 2017, Houston Electric recognized approximately $21 million and $7 million, respectively, of the allowed equity return. The timing of CenterPoint Energy’s recognition of the 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]	CenterPoint Energy is not earning a return on its Hurricane Harvey restoration costs.
[3]	Current regulatory assets are included in Prepaid expenses and other current assets in CenterPoint Energy’s Condensed Consolidated Balance Sheets.
[4]	Current regulatory liabilities are included in Other current liabilities in CenterPoint Energy’s Condensed Consolidated Balance Sheets.
[5]	Includes a portion of NGD’s actuarially determined pension and other postemployment expense in excess of the amount being recovered through rates that is being deferred for rate making purposes. Deferred pension and other postemployment expenses of $6 million and $7 million as of March 31, 2018 and December 31, 2017, respectively, were not earning a return.
[6]	The EDIT and deferred revenues will be recovered or refunded to customers as required by tax and regulatory authorities.
[7]	Other long-term regulatory assets that are not earning a return were not material as of March 31, 2018 and December 31, 2017.

Derivative Instruments Derivatives and hedging (Details) - USD ($)
$ in Millions

3 Months Ended

Mar. 31, 2018

Mar. 31, 2017

Mar. 26, 2018

Feb. 28, 2018

Gains (Losses) in Revenue [Member] | Weather Hedge Swaps [Member]

Weather hedges term

10 years

Recognized gain (loss) on weather hedges

^[1]

$ (4)

$ 1

Gains (Losses) in Revenue [Member] | Weather Hedge Swaps [Member] | Natural Gas Distribution [Member]

Recognized gain (loss) on weather hedges

Gains (Losses) in Revenue [Member] | Weather Hedge Swaps [Member] | Electric Transmission and Distribution [Member]

Recognized gain (loss) on weather hedges

(4)

$ 1

2017 to 2018 [Member] | Natural Gas Distribution [Member]

Weather hedge bilateral cap amount

2017 to 2018 [Member] | Electric Transmission and Distribution [Member]

Weather hedge bilateral cap amount

2016to2017 [Member] | Electric Transmission and Distribution [Member]

Weather hedge bilateral cap amount

CenterPoint Houston [Member] | January thru February [Member] | Treasury Lock [Member]

Aggregate notional amount

200

Effective portion of realized gains (losses)

CERC Corp [Member] | March [Member] | Treasury Lock [Member]

Aggregate notional amount

450

Effective portion of realized gains (losses)

$ (1)

General Mortgage Bonds Due 2048 [Member] | CenterPoint Houston [Member]

Senior Notes [Member] | CERC Corp [Member]

$ 400

$ 600

[1]	Weather hedge gains (losses) are recorded in Revenues in the Condensed Statements of Consolidated Income.

Derivative Instruments Derivative Fair Values (Details)

3 Months Ended

12 Months Ended

Mar. 31, 2018

USD ($)

Bcf

Mar. 31, 2017

USD ($)

Dec. 31, 2017

USD ($)

Bcf

$ 166,000,000

$ 218,000,000

Gain (loss) on derivative instruments not designated as hedging instruments

789,000,000

775,000,000

(30,000,000)

$ 19,000,000

Total fair value of the derivative instruments that contain credit risk contingent features that are in a net liability position

2,000,000

The aggregate fair value of assets already posted as collateral

Credit risk contingent features assets

2,000,000

$ 2,000,000

Gains (Losses) in Expense: Natural Gas [Member]

Change in unrealized gain (loss) on hedged item in fair value hedge

(2,000,000)

(4,000,000)

Gain (loss) on fair value hedges recognized in earnings

^[1]

$ (2,000,000)

(1,000,000)

Energy Related Derivative [Member]

Derivative gross volume notional amount (in Bcf) | Bcf

1,735

1,795

Net amount presented in the consolidated balance sheets

^[2]

$ 103,000,000

$ 130,000,000

Gross Amounts Offset in the Consolidated Balance Sheets

^[3]

51,000,000

111,000,000

52,000,000

19,000,000

Gain (loss) on derivative instruments not designated as hedging instruments

57,000,000

96,000,000

Change in unrealized gain (loss) on fair value hedging instruments

3,000,000

Gain (loss) on derivative instruments not designated as hedging instruments

(69,000,000)

(67,000,000)

^[3]

105,000,000

165,000,000

(21,000,000)

(55,000,000)

Derivative Asset

^[2]

84,000,000

110,000,000

^[3]

61,000,000

53,000,000

(9,000,000)

Derivative Asset

^[2]

52,000,000

44,000,000

^[3]

(73,000,000)

(83,000,000)

52,000,000

63,000,000

Derivative Liability

^[2]

(21,000,000)

(20,000,000)

^[3]

(42,000,000)

(24,000,000)

30,000,000

20,000,000

Derivative Liability

^[2]

(12,000,000)

(4,000,000)

^[4]

1,000,000

^[5],[6]

13,000,000

^[7],[8]

^[4]

1,000,000

^[5],[6]

1,000,000

^[7],[8]

^[4]

86,000,000

^[5],[6]

114,000,000

^[7],[8]

^[4]

2,000,000

^[5],[6]

4,000,000

^[7],[8]

^[4]

52,000,000

^[5],[6]

44,000,000

^[7],[8]

^[4]

^[5],[6]

^[7],[8]

^[4]

18,000,000

^[5],[6]

38,000,000

^[7],[8]

^[4]

70,000,000

^[5],[6]

78,000,000

^[7],[8]

^[4]

9,000,000

^[5],[6]

9,000,000

^[7],[8]

^[4]

$ 42,000,000

^[5],[6]

$ 24,000,000

^[7],[8]

Derivative gross volume notional amount (in Bcf) | Bcf

437

224

IDS Derivative [Member] | Gains (losses) in Other Income (Expense) [Member]

Gain (loss) on derivative instruments not designated as hedging instruments

$ (18,000,000)

$ (10,000,000)

IDS Derivative [Member] | Not Designated as Hedging Instrument [Member] | Current Liabilities [Member]

$ 0

Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]

$ 674,000,000

$ 668,000,000

[1]	Hedge ineffectiveness results from the basis ineffectiveness discussed above, and excludes the impact to natural gas expense from timing ineffectiveness. Timing ineffectiveness arises due to changes in the difference between the spot price and the futures price, as well as the difference between the timing of the settlement of the futures and the valuation of the underlying physical commodity. As the commodity contract nears the settlement date, spot-to-forward price differences should converge, which should reduce or eliminate the impact of this ineffectiveness on natural gas expense.
[2]	The derivative assets and liabilities on the Condensed Consolidated Balance Sheets exclude accounts receivable or accounts payable that, should they exist, could be used as offsets to these balances in the event of a default.
[3]	Gross amounts recognized include some derivative assets and liabilities that are not subject to master netting arrangements.
[4]	Derivative Assets and Derivative Liabilities include no material amounts related to physical forward transactions with Enable.
[5]	Natural gas contracts are presented on a net basis in the Condensed Consolidated Balance Sheets as they are subject to master netting arrangements. This netting applies to all undisputed amounts due or past due and causes derivative assets (liabilities) to be ultimately presented net in a liability (asset) account within the Condensed Consolidated Balance Sheets. The net of total non-trading natural gas derivative assets and liabilities was a $103 million asset as shown on CenterPoint Energy’s Condensed Consolidated Balance Sheets (and as detailed in the table below), and was comprised of the natural gas contracts derivative assets and liabilities separately shown above, impacted by collateral netting of $52 million.
[6]	The fair value shown for natural gas contracts is comprised of derivative gross volumes totaling 1,735 Bcf or a net 437 Bcf long position. Certain natural gas contracts hedge basis risk only and lack a fixed price exposure.
[7]	Natural gas contracts are presented on a net basis in the Condensed Consolidated Balance Sheets as they are subject to master netting arrangements. This netting applies to all undisputed amounts due or past due and causes derivative assets (liabilities) to be ultimately presented net in a liability (asset) account within the Condensed Consolidated Balance Sheets. The net of total non-trading natural gas derivative assets and liabilities was a $130 million asset as shown on CenterPoint Energy’s Condensed Consolidated Balance Sheets (and as detailed in the table below), and was comprised of the natural gas contracts derivative assets and liabilities separately shown above, impacted by collateral netting of $19 million.
[8]	The fair value shown for natural gas contracts is comprised of derivative gross volumes totaling 1,795 Bcf or a net 224 Bcf long position. Certain natural gas contracts hedge basis risk only and lack a fixed price exposure.

Fair Value Measurements (Details)

3 Months Ended

Mar. 31, 2018

USD ($)

Mar. 31, 2017

USD ($)

Dec. 31, 2017

USD ($)

Fair value amount of Level 1 to Level 2 assets transferred

$ 0

Fair value amount of Level 2 to Level 1 assets transferred

Fair value amount of Level 1 to Level 2 liabilities transferred

Fair value amount of Level 2 to Level 1 liabilities transferred

Assets

Total derivative assets, netting adjustment

(30,000,000)

^[1]

$ (64,000,000)

^[2]

1,152,000,000

1,199,000,000

Total derivative liabilities, netting adjustment

(82,000,000)

^[1]

(83,000,000)

^[2]

Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]

715,000,000

692,000,000

Beginning balance

(622,000,000)

$ (704,000,000)

Total gains (losses)

(4,000,000)

6,000,000

Total settlements

(34,000,000)

(4,000,000)

Transfers into Level 3

1,000,000

Transfers out of Level 3

(2,000,000)

1,000,000

Ending balance (1)

^[3]

(662,000,000)

(700,000,000)

The amount of total gains (losses) for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held at the reporting date (3)

(5,000,000)

$ 5,000,000

Carrying Value [Member]

Estimated Fair Value of Financial Instruments

Long-term debt

8,670,000,000

8,679,000,000

Fair Value [Member]

Estimated Fair Value of Financial Instruments

Long-term debt

9,008,000,000

9,220,000,000

Natural gas derivatives [Member]

Assets

Derivative fair value offsets, net

52,000,000

19,000,000

Fair Value, Inputs, Level 1 [Member]

Assets

1,016,000,000

1,045,000,000

Fair Value, Inputs, Level 2 [Member]

8,000,000

Assets

147,000,000

161,000,000

Fair Value, Inputs, Level 3 [Member]

108,000,000

96,000,000

Assets

19,000,000

57,000,000

Fair Value, Inputs, Level 3 [Member] | Forward Contracts [Member] | Minimum [Member]

$ 681,000,000

679,000,000

Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]

Fair value inputs (price per MMBtu)

1.36

Fair Value, Inputs, Level 3 [Member] | Forward Contracts [Member] | Maximum [Member]

Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]

Fair value inputs (price per MMBtu)

3.26

Fair Value, Inputs, Level 3 [Member] | IDS Derivative [Member]

Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]

Fair value options volatility rate

19.00%

Fair value projected dividend growth rate

6.00%

Fair Value, Measurements, Recurring [Member]

Assets

$ 946,000,000

963,000,000

^[4]

70,000,000

68,000,000

14,000,000

Fair Value, Measurements, Recurring [Member] | IDS Derivative [Member]

8,000,000

Derivative liabilities, netting adjustment

^[1]

^[2]

Derivative liabilities

674,000,000

668,000,000

Fair Value, Measurements, Recurring [Member] | Natural gas derivatives [Member]

Assets

Derivative asset, netting adjustment

^[5]

(30,000,000)

^[1]

(64,000,000)

^[2]

Derivative assets

^[5]

136,000,000

154,000,000

Derivative liabilities, netting adjustment

^[5]

(82,000,000)

^[1]

(83,000,000)

^[2]

Derivative liabilities

^[5]

33,000,000

24,000,000

Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]

Assets

946,000,000

963,000,000

^[4]

70,000,000

68,000,000

14,000,000

Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | IDS Derivative [Member]

8,000,000

Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Natural gas derivatives [Member]

Assets

Derivative asset

^[5]

Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]

^[5]

Assets

^[4]

Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | IDS Derivative [Member]

Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Natural gas derivatives [Member]

Assets

Derivative asset

^[5]

147,000,000

161,000,000

Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]

^[5]

108,000,000

96,000,000

Assets

^[4]

Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | IDS Derivative [Member]

Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Natural gas derivatives [Member]

674,000,000

668,000,000

Assets

Derivative asset

^[5]

19,000,000

57,000,000

^[5]

$ 7,000,000

$ 11,000,000

[1]	Amounts represent the impact of legally enforceable master netting arrangements that allow CenterPoint Energy to settle positive and negative positions and also include cash collateral of $52 million posted with the same counterparties.
[2]	Amounts represent the impact of legally enforceable master netting arrangements that allow CenterPoint Energy to settle positive and negative positions and also include cash collateral of $19 million posted with the same counterparties.
[3]	CenterPoint Energy did not have significant Level 3 sales or purchases during either of the three months ended March 31, 2018 or 2017.
[4]	Amounts are included in Prepaid expenses and other current assets in the Condensed Consolidated Balance Sheets.
[5]	Natural gas derivatives include no material amounts related to physical forward transactions with Enable.

Unconsolidated Affiliate (Details) - USD ($)
$ / shares in Units, $ in Millions

3 Months Ended

Mar. 31, 2018

Mar. 31, 2017

Dec. 31, 2017

Preferred units – unconsolidated affiliate

$ 363

Percentage of sales that trigger right of first refusal

5.00%

Total distributions received from Enable

$ 83

Equity Method Investment, Summarized Financial Information, Gross Profit (Loss) [Abstract]

CenterPoint Energy’s equity in earnings, net

Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]

CenterPoint Energy’s equity method investment in Enable

$ 2,467

2,472

OGE [Member]

Percentage of sales that trigger right of first refusal

5.00%

Equity Method Investment, Ownership Percentage

^[1]

54.00%

Equity Method Investment, Summarized Financial Information, Gross Profit (Loss) [Abstract]

Operating revenues

$ 748

666

Cost of sales, excluding depreciation and amortization

375

308

Operating income

139

140

Net income attributable to Enable

105

111

CenterPoint Energy’s interest

Basis difference amortization (1)

^[2]

CenterPoint Energy’s equity in earnings, net

$ 69

Basis difference amortization period

31 years

Equity Method Investment, Summarized Financial Information, Assets and Liabilities [Abstract]

Current assets

$ 413

416

Non-current assets

11,274

11,177

Current liabilities

1,404

1,279

Non-current liabilities

2,664

2,660

Non-controlling interest

Preferred equity

362

Enable partners’ equity

7,246

7,280

Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]

CenterPoint Energy’s ownership interest in Enable partners’ equity

3,913

3,935

CenterPoint Energy’s basis difference

(1,446)

(1,463)

CenterPoint Energy’s equity method investment in Enable

2,467

2,472

Enable Midstream Partners [Member] | Common Units [Member]

Distributions received from Enable equity method investment

Enable Midstream Partners [Member] | Series A Preferred Units [Member]

Distributions received from Enable cost method investment

$ 9

Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage

^[1]

100.00%

Maximum incentive distribution right

50.00%

Enable Midstream Partners [Member] | CERC Corp [Member]

Management rights ownership percentage

50.00%

Incentive distribution right

40.00%

Enable Midstream Partners [Member] | OGE [Member]

Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage

^[1]

25.60%

Management rights ownership percentage

50.00%

Incentive distribution right

60.00%

Enable Midstream Partners [Member] | Public unitholders [Member]

Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage

^[1]

20.40%

Enable Midstream Partners [Member] | Minimum [Member]

Incentive distribution per unit

$ 0.2875

Enable Midstream Partners [Member] | Maximum [Member]

Incentive distribution per unit

$ 0.330625

Common Units [Member] | Enable Midstream Partners [Member]

Equity Method Investment, Ownership, Shares

233,856,623

Common Units [Member] | Enable Midstream Partners [Member]

Variable Interest Entity, Ownership, Shares

433,072,001

Common Units [Member] | Enable Midstream Partners [Member] | OGE [Member]

Variable Interest Entity, Ownership, Shares

110,982,805

Common Units [Member] | Enable Midstream Partners [Member] | Public unitholders [Member]

Variable Interest Entity, Ownership, Shares

88,232,573

Series A Preferred Units [Member] | Enable Midstream Partners [Member]

Transitional Service [Member] | Enable Midstream Partners [Member]

Preferred Units Held

^[3]

14,520,000

Transactions with Enable [Abstract]

Reimbursement of transition services (1)

^[4]

$ 2

Accounts receivable for amounts billed for transition services

Natural Gas Expenses [Member] | Enable Midstream Partners [Member]

Transactions with Enable [Abstract]

Natural gas expenses, including transportation and storage costs

$ 33

Accounts payable for natural gas purchases from Enable

$ 11

$ 13

[1]	Excluding the Series A Preferred Units owned by CenterPoint Energy.
[2]	Equity in earnings of unconsolidated affiliate includes CenterPoint Energy’s share of Enable’s earnings adjusted for the amortization of the basis difference of CenterPoint Energy’s original investment in Enable and its underlying equity in Enable’s net assets. The basis difference is amortized over approximately 31 years, the average life of the assets to which the basis difference is attributed.
[3]	The carrying amount of the Series A Preferred Units, reflected as Preferred units - unconsolidated affiliate on the Condensed Consolidated Balance Sheets, was $363 million as of both March 31, 2018 and December 31, 2017. No impairment charges or adjustment due to observable price changes were made during the current or prior reporting periods. See Note 2 for further discussion.
[4]	Represents amounts billed under the Transition Agreements for certain support services provided to Enable. Actual transition services costs are recorded net of reimbursement.

Goodwill and Other Intangibles (Details) - USD ($)
$ in Millions

3 Months Ended

Mar. 31, 2018

Mar. 31, 2017

Dec. 31, 2017

$ 867

105

(34)

(31)

Amortization expense of intangible assets

$ 2

746

Accumulated goodwill impairment charge recorded in 2012

^[1]

110

252

Other Operations [Member]

Customer Relationships [Member]

$ 11

Intangible asset useful lives

15 years

$ 86

(23)

(21)

Noncompete Agreements [Member]

$ 63

Intangible asset useful lives

4 years

$ 4

(2)

Other Intangible Assets [Member]

(9)

(8)

$ 6

$ 7

[1]	Amount presented is net of the accumulated goodwill impairment charge of $252 million recorded in 2012.

Indexed Debt Securities (ZENS) and Securities Related to ZENS (Details) $ / shares in Units, $ in Millions		3 Months Ended
	Feb. 15, 2017 $ / shares shares	Mar. 31, 2018 USD ($) shares	Mar. 31, 2017 USD ($)	Jan. 31, 2018 $ / shares	Dec. 31, 2017 shares	Nov. 26, 2017 $ / shares
Distribution To ZENS holders \| $		$ 16	$ 0
Indexed debt – reduction \| $		(4)
Indexed debt securities derivative – reduction \| $		(1)
Loss on indexed debt securities \| $		11
Subordinated Debt ZENS [Member]
Principal amount of debt issued \| $		1,000
Outstanding debt balance \| $		$ 828
Subordinated note cash exchangeable percentage of fair value		95.00%
Contingent principal amount outstanding \| $		$ 486
TW Common [Member]
Balance of investment owned (in shares) \| shares		7,107,130			7,107,130
TW Common [Member] \| Subordinated Debt ZENS [Member]
Number of shares referenced in exchangeable subordinated note \| shares		0.5			0.5
Time Common [Member]
Balance of investment owned (in shares) \| shares					888,392
ZENS early exchange ratio				100.00%
Time Common [Member] \| Subordinated Debt ZENS [Member]
Number of shares referenced in exchangeable subordinated note \| shares					0.0625
Charter Common [Member]
Balance of investment owned (in shares) \| shares		872,503			872,503
Charter Common [Member] \| Subordinated Debt ZENS [Member]
Number of shares referenced in exchangeable subordinated note \| shares		0.061382			0.061382
AT&T To Acquire Time Warner [Member]
Implied value of consideration received by TW common stock shareholders, net \| $ / shares	$ 107.50
Implied value of consideration received by TW common stock shareholders, Cash \| $ / shares	53.75
Implied value of consideration received by TW common stock shareholders, Noncash \| $ / shares	$ 53.75
Lower range of shares received by TW common shareholders \| shares	1.437
Price of AT&T common stock, lower range \| $ / shares	$ 37.411
Upper range of shares received by TW Common shareholders \| shares	1.3
Price of AT&T common stock, upper range \| $ / shares	$ 41.349
Meredith to acquire Time [Member] \| Time Common [Member]
Cash paid per share of Time Common \| $ / shares				$ 18.50		$ 18.50
Cash proceeds received for Time Common shares \| $		$ 16

Short-Term Borrowings and Long-term Debt (Details)

3 Months Ended

Mar. 26, 2018

USD ($)

Feb. 28, 2018

USD ($)

Mar. 31, 2018

USD ($)

Dec. 31, 2017

USD ($)

Short-term Debt [Line Items]

Short-term borrowings

$ 0

$ 39,000,000

2,900,000,000

Parent Company [Member]

CenterPoint Houston [Member]

1,700,000,000

300,000,000

CERC Corp [Member]

Revolving Credit Facility [Member]

900,000,000

Revolving Credit Facility [Member] | Parent Company [Member]

Revolving Credit Facility [Member] | CenterPoint Houston [Member]

Revolving Credit Facility [Member] | CERC Corp [Member]

Line of Credit [Member] | Parent Company [Member]

$ 0

Percentage on limitation of debt to total capitalization under covenant

^[1]

65.00%

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

70.00%

Ratio of indebtedness to net capital

^[2]

0.526

System restoration costs threshold for increase in permitted debt to EBITDA covenant ratio

$ 100,000,000

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

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

Line of Credit [Member] | CenterPoint Houston [Member]

Basis spread on LIBOR

^[3]

1.25%

Percentage on limitation of debt to total capitalization under covenant

^[1]

65.00%

Ratio of indebtedness to net capital

^[2]

0.512

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

Line of Credit [Member] | CERC Corp [Member]

Basis spread on LIBOR

^[3]

1.125%

Percentage on limitation of debt to total capitalization under covenant

65.00%

Ratio of indebtedness to net capital

^[2]

0.387

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

Letter of Credit [Member]

Basis spread on LIBOR

^[3]

1.25%

Letter of Credit [Member] | Parent Company [Member]

$ 11,000,000

11,000,000

Letter of Credit [Member] | CenterPoint Houston [Member]

6,000,000

Letter of Credit [Member] | CERC Corp [Member]

4,000,000

Commercial Paper [Member]

1,000,000

Commercial Paper [Member] | Parent Company [Member]

915,000,000

1,753,000,000

Weighted average interest rate of debt

^[4]

$ 189,000,000

$ 855,000,000

2.24%

1.88%

Commercial Paper [Member] | CenterPoint Houston [Member]

Commercial Paper [Member] | CERC Corp [Member]

$ 0

Weighted average interest rate of debt

^[5]

$ 726,000,000

$ 898,000,000

2.34%

1.72%

Product Financing Arrangement [Member]

Short-term Debt [Line Items]

Short-term borrowings

$ 0

$ 39,000,000

General Mortgage Bonds Due 2048 [Member] | CenterPoint Houston [Member]

Debt Instruments [Abstract]

Interest rate of debt issued

$ 400,000,000

3.95%

Maturity date of debt issued

Mar. 01, 2048

Senior Notes Due 2023 [Member] | CERC Corp [Member]

Debt Instruments [Abstract]

Interest rate of debt issued

$ 300,000,000

3.55%

Maturity date of debt issued

Apr. 01, 2023

Senior Notes Due 2028 [Member] | CERC Corp [Member]

Debt Instruments [Abstract]

Interest rate of debt issued

$ 300,000,000

4.00%

Maturity date of debt issued

Apr. 01, 2028

[1]	The financial covenant limit will temporarily increase from 65% to 70% if Houston Electric experiences damage from a natural disaster in its service territory and CenterPoint Energy certifies to the administrative agent that Houston Electric has incurred system restoration costs reasonably likely to exceed $100 million in a consecutive 12-month period, all or part of which Houston Electric intends to seek to recover through securitization financing. Such temporary increase in the financial covenant would be in effect from the date CenterPoint Energy delivers its certification until the earliest to occur of (i) the completion of the securitization financing, (ii) the first anniversary of CenterPoint Energy’s certification or (iii) the revocation of such certification.
[2]	As defined in the revolving credit facility agreement, excluding Securitization Bonds.
[3]	Based on current credit ratings.
[4]	Weighted average interest rate was 2.24% and 1.88% as of March 31, 2018 and December 31, 2017, respectively.
[5]	Weighted average interest rate was 2.34% and 1.72% as of March 31, 2018 and December 31, 2017, respectively.

Income Taxes (Details)	3 Months Ended
Income Taxes (Details)	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Effective income tax rate	22.00%	36.00%
Federal statutory income tax rate	21.00%	35.00%

Commitments and Contingencies (Details)	3 Months Ended
Commitments and Contingencies (Details)	Mar. 31, 2018 USD ($)
CERC Corp [Member] \| Minnesota Service Territory [Member]
Legal, Environmental and Other Matters
Liability recorded for remediation of Minnesota sites	$ 7,000,000
CERC Corp [Member] \| Minnesota Service Territory [Member] \| Minimum [Member]
Legal, Environmental and Other Matters
Estimated remediation costs for the Minnesota sites	$ 5,000,000
Years to resolve contingency	30 years
CERC Corp [Member] \| Minnesota Service Territory [Member] \| Maximum [Member]
Legal, Environmental and Other Matters
Estimated remediation costs for the Minnesota sites	$ 30,000,000
Years to resolve contingency	50 years
Natural Gas Supply Commitments [Member]
Natural Gas Supply Commitments
Remaining nine months of 2018	$ 289,000,000
2019	311,000,000
2020	170,000,000
2021	81,000,000
2022	51,000,000
2023 and beyond	125,000,000
Minnehaha Academy Gas Explosion [Member]
Legal, Environmental and Other Matters
Contested amount of fines imposed	$ 200,000

Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Net income	$ 165	$ 192
Basic weighted average shares outstanding	431,231,000	430,794,000
Plus: Incremental shares from assumed conversions:
Diluted weighted average shares	434,008,000	433,348,000
Basic earnings per share
Net income	$ 0.38	$ 0.45
Diluted earnings per share
Net income	$ 0.38	$ 0.44
Restricted Stock [Member]
Plus: Incremental shares from assumed conversions:
Restricted stock	2,777,000	2,554,000

Reportable Business Segments (Details) - USD ($)
$ in Millions

3 Months Ended

Mar. 31, 2018

Mar. 31, 2017

Dec. 31, 2017

$ 3,155

$ 2,735

251

291

^[1]

Electric Transmission and Distribution [Member]

22,410

$ 22,736

Enable

Total regulatory assets

2,278

2,477

^[2]

751

639

Electric Transmission and Distribution [Member] | Affiliates of NRG Energy, Inc. [Member]

115

^[1]

Electric Transmission and Distribution [Member] | Affiliates of Vistra Energy Corp. [Member]

161

152

1,143

907

156

168

^[1]

1,257

1,185

Midstream Investments [Member]

(26)

^[1]

^[3]

Other Operations [Member]

^[3]

^[1]

Intersegment Eliminations [Member]

^[1]

(38)

(20)

Intersegment Eliminations [Member] | Electric Transmission and Distribution [Member]

(682)

(654)

Intersegment Eliminations [Member] | Natural Gas Distribution [Member]

Intersegment Eliminations [Member] | Energy Services [Member]

(10)

(9)

Intersegment Eliminations [Member] | Midstream Investments [Member]

(28)

(11)

Intersegment Eliminations [Member] | Other Operations [Member]

^[3]

Operating Segments [Member] | Electric Transmission and Distribution [Member]

Operating Segments [Member] | Natural Gas Distribution [Member]

10,358

10,292

Operating Segments [Member] | Energy Services [Member]

6,438

6,608

Operating Segments [Member] | Midstream Investments [Member]

1,329

1,521

Operating Segments [Member] | Other Operations [Member]

^[3]

2,467

2,472

^[4]

2,500

2,497

Enable Midstream Partners [Member] | Midstream Investments [Member]

Enable