CenterPoint Energy (CNP) 10-Q 6 Nov 13 2013 Q3 Quarterly report Financial data

Document_and_Entity_Supplement

Document and Entity Supplemental Information Document (USD $)	9 Months Ended
	Sep. 30, 2013	Oct. 18, 2013	Jun. 30, 2012
Entity Information [Line Items]	'	'	'
Entity Registrant Name	'CENTERPOINT ENERGY INC.	'	'
Entity Central Index Key	'0001130310	'	'
Current Fiscal Year End Date	'--12-31	'	'
Entity Filer Category	'Large Accelerated Filer	'	'
Document Type	'10-Q	'	'
Document Period End Date	30-Sep-13	'	'
Document Fiscal Year Focus	'2013	'	'
Document Fiscal Period Focus	'Q3	'	'
Amendment Flag	'false	'	'
Entity Common Stock, Shares Outstanding	'	428,640,167	'
Entity Well-known Seasoned Issuer	'Yes	'	'
Entity Voluntary Filers	'No	'	'
Entity Current Reporting Status	'Yes	'	'
Entity Public Float	'	'	$8,760,880,387

Condensed_Statements_of_Consol

Condensed Statements of Consolidated Income (Unaudited) (USD $)	3 Months Ended		9 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Revenues	$1,640	$1,705	$5,922	$5,314
Expenses:	'	'	'	'
Natural gas	595	520	2,671	1,898
Natural gas - affiliates	42	0	70	0
Operation and maintenance	422	458	1,352	1,364
Depreciation and amortization	248	301	741	800
Taxes other than income taxes	89	86	289	272
Goodwill impairment	0	252	0	252
Total	1,396	1,617	5,123	4,586
Operating Income	244	88	799	728
Other Income (Expense):	'	'	'	'
Gain on marketable securities	54	77	158	136
Loss on indexed debt securities	-42	-52	-120	-76
Interest and other finance charges	-86	-104	-269	-318
Interest on transition and system restoration bonds	-32	-37	-101	-112
Equity in earnings of unconsolidated affiliates, net	80	8	122	25
Step acquisition gain	0	136	0	136
Other, net	11	12	17	28
Total	-15	40	-193	-181
Income Before Income Taxes	229	128	606	547
Income tax expense	78	118	408	264
Net Income	$151	$10	$198	$283
Basic Earnings Per Share	$0.35	$0.02	$0.46	$0.66
Diluted Earnings Per Share	$0.35	$0.02	$0.46	$0.66
Dividends Declared Per Share	$0.21	$0.20	$0.62	$0.61
Weighted Average Shares Outstanding, Basic	428,628,000	427,406,000	428,389,000	427,086,000
Weighted Average Shares Outstanding, Diluted	430,867,000	429,983,000	430,624,000	429,655,000

Condensed_Statements_of_Consol1

Condensed Statements of Consolidated Comprehensive Income (Unaudited) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Net income	$151	$10	$198	$283
Other comprehensive income:	'	'	'	'
Adjustment related to pension and other postretirement plans (net of tax of $2, $2, $6 and $5)	3	3	8	8
Total	3	3	8	8
Comprehensive income	$154	$13	$206	$291

Condensed_Statements_of_Consol2

Condensed Statements of Consolidated Comprehensive Income Comprehensive Income Parentheticals (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement of Comprehensive Income [Abstract]	'	'	'	'
Other Comprehensive Income, Pension and Other Postretirement Benefit Plans, Tax	$2	$2	$5	$6

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (Unaudited) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Current Assets:	'	'
Cash and cash equivalents ($266 and $154 related to VIEs at December 31, 2012 and September 30, 2013, respectively)	$219	$646
Investment in marketable securities	689	540
Accounts receivable, net ($68 and $77 related to VIEs at December 31, 2012 and September 30, 2013, respectively)	617	768
Accrued unbilled revenues	170	339
Accounts receivable - affiliated companies	23	0
Natural gas inventory	237	145
Materials and supplies	137	177
Non-trading derivative assets	26	36
Taxes receivable	89	7
Prepaid expenses and other current assets ($54 and $44 related to VIEs at December 31, 2012 and September 30, 2013, respectively)	112	216
Total current assets	2,319	2,874
Property, Plant and Equipment:	'	'
Property, plant and equipment	13,909	18,377
Less accumulated depreciation and amortization	4,523	4,780
Property, plant and equipment, net	9,386	13,597
Other Assets:	'	'
Goodwill	840	1,468
Regulatory assets ($3,545 and $3,253 related to VIEs at December 31, 2012 and September 30, 2013, respectively)	3,992	4,324
Notes receivable - affiliated companies	363	0
Non-trading derivative assets	10	6
Investment in unconsolidated affiliates	4,525	405
Other	140	197
Total other assets	9,870	6,400
Total Assets	21,575	22,871
Current Liabilities:	'	'
Short-term borrowings	70	38
Current portion of VIE transition and system restoration bonds long-term debt	353	447
Current portion of indexed debt	141	138
Current portion of other long-term debt	59	815
Indexed debt securities derivative	382	268
Accounts payable	364	561
Accounts payable - affiliated companies	22	0
Taxes accrued	130	160
Interest accrued	100	150
Non-trading derivative liabilities	6	14
Accumulated deferred income taxes, net	625	604
Other	343	380
Total current liabilities	2,595	3,575
Other Liabilities:	'	'
Accumulated deferred income taxes, net	4,504	4,153
Non-trading derivative liabilities	1	2
Benefit obligations	1,052	1,143
Regulatory liabilities	1,153	1,093
Other	251	247
Total other liabilities	6,961	6,638
Long-term Debt:	'	'
VIE transition and system restoration bonds	3,106	3,400
Other	4,652	4,957
Total long-term debt	7,758	8,357
Commitments and Contingencies (Note 12)	'	'
Shareholders’ Equity:	'	'
Common stock (427,599,564 shares and 428,640,167 shares outstanding at December 31, 2012 and September 30, 2013, respectively)	4	4
Additional paid-in capital	4,151	4,130
Retained earnings	233	302
Accumulated other comprehensive loss	-127	-135
Total shareholders’ equity	4,261	4,301
Total Liabilities and Shareholders’ Equity	$21,575	$22,871

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets Balance Sheets Parentheticals (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, except Share data, unless otherwise specified
Total common stock outstanding (in shares)	428,640,167	427,599,564
Cash and cash equivalents	$219	$646
Accounts receivable, net	617	768
Prepaid expenses and other current assets	112	216
Regulatory assets	3,992	4,324
Variable Interest Entity, Primary Beneficiary [Member]	'	'
Cash and cash equivalents	154	266
Accounts receivable, net	77	68
Prepaid expenses and other current assets	44	54
Regulatory assets	$3,253	$3,545

Condensed_Statements_of_Consol3

Condensed Statements of Consolidated Cash Flows (Unaudited) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Cash Flows from Operating Activities:	'	'
Net income	$198	$283
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation and amortization	741	800
Amortization of deferred financing costs	23	23
Deferred income taxes	356	237
Goodwill impairment	0	252
Step acquisition gain	0	-136
Unrealized gain on marketable securities	-158	-136
Unrealized loss on indexed debt securities	120	76
Write-down of natural gas inventory	4	4
Equity in earnings of unconsolidated affiliates, net of distributions	-65	-6
Pension contributions	-89	-80
Changes in other assets and liabilities:	'	'
Accounts receivable and unbilled revenues, net	173	260
Inventory	-111	-3
Taxes receivable	-53	-5
Accounts payable	-151	-186
Fuel cost recovery	105	-72
Non-trading derivatives, net	-6	16
Margin deposits, net	5	49
Interest and taxes accrued	-66	-71
Net regulatory assets and liabilities	78	71
Other current assets	21	-12
Other current liabilities	-40	-23
Other assets	-2	-4
Other liabilities	36	32
Other, net	13	10
Net cash provided by operating activities	1,132	1,379
Cash Flows from Investing Activities:	'	'
Capital expenditures	-912	-818
Acquisitions, net of cash acquired	0	-360
Decrease (increase) in restricted cash of transition and system restoration bond companies	13	-12
Distributions from unconsolidated affiliates	0	6
Cash contribution to Enable	-38	0
Proceeds from sale of marketable securities	9	0
Other, net	2	-25
Net cash used in investing activities	-926	-1,209
Cash Flows from Financing Activities:	'	'
Increase (decrease) in short-term borrowings, net	32	-9
Payments of commercial paper, net	0	-285
Proceeds from long-term debt	1,050	2,495
Payments of long-term debt	-1,455	-1,528
Cash paid for debt exchange and debt retirement	0	-69
Debt issuance costs	-4	-16
Redemption of indexed debt securities	-8	0
Payment of common stock dividends	-267	-259
Proceeds from issuance of common stock, net	2	3
Other, net	17	0
Net cash provided by (used in) financing activities	-633	332
Net Increase (Decrease) in Cash and Cash Equivalents	-427	502
Cash and Cash Equivalents at Beginning of Period	646	220
Cash and Cash Equivalents at End of Period	219	722
Cash Payments:	'	'
Interest, net of capitalized interest	394	446
Income taxes, net	77	46
Non-cash transactions:	'	'
Accounts payable related to capital expenditures	$83	$100

Background_and_Basis_of_Presen

Background and Basis of Presentation	9 Months Ended
	Sep. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Background and Basis of Presentation	'
	Background and Basis of Presentation
	General. Included in this Quarterly Report on Form 10-Q (Form 10-Q) of CenterPoint Energy, Inc. are the condensed consolidated interim financial statements and notes (Interim Condensed Financial Statements) of CenterPoint Energy, Inc. and its subsidiaries (collectively, CenterPoint Energy). The Interim Condensed Financial Statements are unaudited, omit certain financial statement disclosures and should be read with the Annual Report on Form 10-K of CenterPoint Energy for the year ended December 31, 2012 (CenterPoint Energy Form 10-K).
	Background. CenterPoint Energy, Inc. is a public utility holding company. CenterPoint Energy’s operating subsidiaries own and operate electric transmission and distribution facilities and natural gas distribution facilities and own an interest in Enable Midstream Partners, LP (Enable) as described below. As of September 30, 2013, CenterPoint Energy’s indirect wholly owned subsidiaries included:
	•	CenterPoint Energy Houston Electric, LLC (CenterPoint Houston), which engages in the electric transmission and distribution business in the Texas Gulf Coast area that includes the city of Houston; and
	•	CenterPoint Energy Resources Corp. (CERC Corp. and, together with its subsidiaries, CERC), which owns and operates natural gas distribution systems (Gas Operations). A wholly owned subsidiary of CERC Corp. offers variable and fixed-price physical natural gas supplies primarily to commercial and industrial customers and electric and gas utilities. CERC Corp. also owns approximately 58.3% of the limited partner interests in Enable, which owns and operates interstate pipelines and natural gas gathering, processing and treating facilities.
	On March 14, 2013, CenterPoint Energy entered into a Master Formation Agreement (MFA) with OGE Energy Corp. (OGE) and affiliates of ArcLight Capital Partners, LLC (ArcLight), pursuant to which CenterPoint Energy, OGE and ArcLight agreed to form Enable as a private limited partnership. On May 1, 2013, the parties closed on the formation of Enable. In connection with the closing (i) CERC Corp. converted its direct wholly owned subsidiary, CenterPoint Energy Field Services, LLC, a Delaware limited liability company (CEFS), into a Delaware limited partnership that became Enable, (ii) CERC Corp. contributed to Enable its equity interests in each of CenterPoint Energy Gas Transmission Company, LLC, which has been subsequently renamed Enable Gas Transmission, LLC (EGT), CenterPoint Energy - Mississippi River Transmission, LLC, which has been subsequently renamed Enable Mississippi River Transmission, LLC (MRT), certain of its other midstream subsidiaries (Other CNP Midstream Subsidiaries), and a 24.95% interest in Southeast Supply Header, LLC (SESH and, collectively with CEFS, EGT, MRT and Other CNP Midstream Subsidiaries, CenterPoint Midstream), and (iii) OGE and ArcLight indirectly contributed 100% of the equity interests in Enogex LLC, which has been subsequently renamed Enable Oklahoma Intrastate Transmission, LLC (Enogex), to Enable.
	CERC Corp., OGE and ArcLight hold approximately 58.3%, 28.5% and 13.2%, respectively, of the limited partner interests in Enable. Enable is equally controlled by CERC Corp. and OGE; each own 50% of the management rights in the general partner of Enable. CERC Corp. and OGE will also own a 40% and 60% interest, respectively, in any incentive distribution rights to be held by the general partner of Enable following an initial public offering. The general partner of Enable is governed by a board of directors made up of an equal number of representatives designated by each of CERC Corp. and OGE. See Note 7 for further discussion on the formation of Enable. The investment in Enable is accounted for utilizing the equity method of accounting. See Notes 7 and 14 below.
	As of September 30, 2013, CenterPoint Energy had four variable interest entities (VIEs) consisting of transition and system restoration bond companies which it consolidates. The consolidated VIEs are wholly owned bankruptcy remote special purpose entities that were formed specifically for the purpose of securitizing transition and system restoration property. Creditors of CenterPoint Energy have no recourse to any assets or revenues of the transition and system restoration bond companies. The bonds issued by these VIEs are payable only from and secured by transition and system restoration property and the bondholders have no recourse to the general credit of CenterPoint Energy.
	Additionally, as of September 30, 2013, CenterPoint Energy determined that Enable was a VIE; however, CenterPoint Energy is not the primary beneficiary and as such, this entity is not consolidated. See Note 7 for further discussion.
	Basis of Presentation. The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
	CenterPoint Energy’s Interim Condensed Financial Statements reflect all normal recurring adjustments that are, in the opinion of management, necessary to present fairly the financial position, results of operations and cash flows for the respective periods. Amounts reported in CenterPoint Energy’s Condensed Statements of Consolidated Income are not necessarily indicative of amounts expected for a full-year period due to the effects of, among other things, (a) seasonal fluctuations in demand for energy and energy services, (b) changes in energy commodity prices, (c) timing of maintenance and other expenditures and (d) acquisitions and dispositions of businesses, assets and other interests.
	For a description of CenterPoint Energy’s reportable business segments, see Note 14.

New_Accounting_Pronouncements

New Accounting Pronouncements	9 Months Ended
	Sep. 30, 2013
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]	'
Description of New Accounting Pronouncements Not yet Adopted [Text Block]	'
	New Accounting Pronouncements
	In February 2013, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update No. 2013-02, “Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income” (ASU 2013-02).   The objective of ASU 2013-02 is to improve the transparency of changes in other comprehensive income and items reclassified out of Accumulated Other Comprehensive Income in financial statements.  This new guidance is effective for a reporting entity's first reporting period beginning after December 15, 2012 and should be applied prospectively.  CenterPoint Energy's adoption of this new guidance on January 1, 2013 did not have a material impact on its financial position, results of operations or cash flows.
	In December 2011 and January 2013, the FASB issued Accounting Standards Update No. 2011-11, “Disclosures About Offsetting Assets and Liabilities” (ASU 2011-11) and No. 2013-01, “Clarifying the Scope of Disclosures About Offsetting Assets and Liabilities” (ASU 2013-01), respectively.  The objective of ASU 2011-11 is to enhance disclosures about the nature of an entity's rights of setoff and related arrangements associated with its financial instruments and derivative instruments.  The objective of ASU 2013-01 is to clarify which instruments and transactions are subject to ASU 2011-11.  Both ASU 2011-11 and ASU 2013-01 are effective for a reporting entity's first reporting period beginning on or after January 1, 2013 and should be applied retrospectively. CenterPoint Energy's adoption of this new guidance on January 1, 2013 did not have a material impact on its financial position, results of operations or cash flows.
	Management believes that other recently issued standards, which are not yet effective, will not have a material impact on CenterPoint Energy’s consolidated financial position, results of operations or cash flows upon adoption.

Employee_Benefit_Plans

Employee Benefit Plans	9 Months Ended
	Sep. 30, 2013
Compensation and Retirement Disclosure [Abstract]	'
Employee Benefit Plans	'
	Employee Benefit Plans
	CenterPoint Energy’s net periodic cost includes the following components relating to pension and postretirement benefits:
		Three Months Ended September 30,
		2012								2013
		Pension				Postretirement				Pension			Postretirement
		Benefits (1)				Benefits				Benefits (1)			Benefits
		(in millions)
	Service cost	$	9			$	—			$	11		$	—
	Interest cost	25				6				22			5
	Expected return on plan assets	(30		)		(1		)		(33		)	(1		)
	Amortization of prior service credit	2				—				3			1
	Amortization of net loss	15				1				15			2
	Amortization of transition obligation	—				2				—			1
	Net periodic cost	$	21			$	8			$	18		$	8
		Nine Months Ended September 30,
		2012								2013
		Pension				Postretirement				Pension			Postretirement
		Benefits (1)				Benefits				Benefits (1)			Benefits
		(in millions)
	Service cost	$	27			$	1			$	33		$	1
	Interest cost	74				18				68			15
	Expected return on plan assets	(90		)		(5		)		(101		)	(5		)
	Amortization of prior service credit	6				2				7			1
	Amortization of net loss	45				3				47			5
	Amortization of transition obligation	—				5				—			5
	Net periodic cost	$	62			$	24			$	54		$	22
	________________
	-1	Net periodic cost in these tables is before considering amounts subject to overhead allocations for capital expenditure projects or for amounts subject to deferral for regulatory purposes.
	CenterPoint Energy's changes in accumulated comprehensive loss related to defined benefit and postretirement plans are as follows:
			Three Months Ended September 30, 2013				Nine Months Ended September 30, 2013
			Pension and Postretirement Plans
			(in millions)
	Beginning Balance		$	(127	)		$	(132	)
	Amounts reclassified from accumulated other comprehensive income:
	Prior service cost (1)		1				2
	Actuarial gains (1)		4				11
	Total reclassifications from accumulated other comprehensive income		5				13
	Tax expense		(2		)		(5		)
	Net current period other comprehensive income		3				8
	Ending Balance		$	(124	)		$	(124	)
	________________
	-1	These accumulated other comprehensive components are included in the computation of net periodic cost.
	CenterPoint Energy expects to contribute a total of approximately $92 million to its pension plans in 2013, of which approximately $52 million and $89 million, respectively, was contributed during the three and nine months ended September 30, 2013.
	CenterPoint Energy expects to contribute a total of approximately $17 million to its postretirement benefits plan in 2013, of which approximately $4 million and $12 million, respectively, was contributed during the three and nine months ended September 30, 2013.

Regulatory_Accounting

Regulatory Accounting	9 Months Ended
	Sep. 30, 2013
Regulatory Assets and Liabilities, Other Disclosures [Abstract]	'
Regulatory Matters	'
	Regulatory Accounting
	As of September 30, 2013, CenterPoint Energy has not recognized an allowed equity return of $518 million because such return will be recognized as it is recovered in rates. During the three months ended September 30, 2012 and 2013, CenterPoint Houston recognized approximately $16 million and $15 million, respectively, of the allowed equity return not previously recognized. During the nine months ended September 30, 2012 and 2013, CenterPoint Houston recognized approximately $37 million and $35 million, respectively, of the allowed equity return not previously recognized.

Derivative_Instruments

Derivative Instruments	9 Months Ended
	Sep. 30, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Derivative Instruments	'
	Derivative Instruments
	CenterPoint Energy is exposed to various market risks. These risks arise from transactions entered into in the normal course of business.  CenterPoint Energy utilizes derivative instruments such as physical forward contracts, swaps and options to mitigate the impact of changes in commodity prices and weather on its operating results and cash flows. Such derivatives are recognized in CenterPoint Energy’s Condensed Consolidated Balance Sheets at their fair value unless CenterPoint Energy elects the normal purchase and sales exemption for qualified physical transactions. A derivative may be designated as a normal purchase or sale if the intent is to physically receive or deliver the product for use or sale in the normal course of business.
	CenterPoint Energy has a Risk Oversight Committee composed of corporate and business segment officers that oversees all commodity price, weather and credit risk activities, including CenterPoint Energy’s marketing, risk management services and hedging activities. The committee’s duties are to establish CenterPoint Energy’s commodity risk policies, allocate board-approved commercial risk limits, approve the use of new products and commodities, monitor positions and ensure compliance with CenterPoint Energy’s risk management policies and procedures and limits established by CenterPoint Energy’s board of directors.
	CenterPoint Energy’s policies prohibit the use of leveraged financial instruments. A leveraged financial instrument, for this purpose, is a transaction involving a derivative whose financial impact will be based on an amount other than the notional amount or volume of the instrument.
	(a)	Non-Trading Activities
	Derivative Instruments. CenterPoint Energy enters into certain derivative instruments to manage physical commodity price risks and does not engage in proprietary or speculative commodity trading.  These financial instruments do not qualify or are not designated as cash flow or fair value hedges.
	Weather Hedges. CenterPoint Energy has weather normalization or other rate mechanisms that mitigate the impact of weather on its gas operations in Arkansas, Louisiana, Mississippi and Oklahoma. Gas operations in Texas and Minnesota and electric operations in Texas do not have such mechanisms. As a result, fluctuations from normal weather may have a significant positive or negative effect on Gas Operations’ results in these jurisdictions and on CenterPoint Houston’s results in its service territory.
	In 2012 and 2013, CenterPoint Energy entered into heating-degree day swaps for certain Gas Operations jurisdictions to mitigate the effect of fluctuations from normal weather on its results of operations and cash flows for the winter heating season. In 2013, CenterPoint Energy also entered into a similar winter weather hedge for the CenterPoint Houston service territory. The swaps are based on ten-year normal weather. During both the three months ended September 30, 2012 and 2013, CenterPoint Energy recognized gains of $-0- related to these swaps. During the nine months ended September 30, 2012 and 2013, CenterPoint Energy recognized gains of $6 million and losses of $6 million, respectively, related to these swaps. Weather hedge gains and losses are included in revenues in the Condensed Statements of Consolidated Income.
	(b)	Derivative Fair Values and Income Statement Impacts
	The following tables present information about CenterPoint Energy’s derivative instruments and hedging activities. The first four tables provide a balance sheet overview of CenterPoint Energy’s Derivative Assets and Liabilities as of December 31, 2012 and September 30, 2013, while the last two tables provide a breakdown of the related income statement impacts for the three and nine months ended September 30, 2012 and 2013.
	Fair Value of Derivative Instruments
					December 31, 2012
	Total derivatives not designated		Balance Sheet		Derivative				Derivative
	as hedging instruments		Location		Assets				Liabilities
					Fair Value				Fair Value
					(in millions)
	Natural gas derivatives (1) (2)		Current Assets: Non-trading derivative assets		$	37			$	1
	Natural gas derivatives (1) (2)		Other Assets: Non-trading derivative assets		6				—
	Natural gas derivatives (1) (2)		Current Liabilities: Non-trading derivative liabilities		5				27
	Natural gas derivatives (1) (2)		Other Liabilities: Non-trading derivative liabilities		1				4
	Indexed debt securities derivative		Current Liabilities		—				268
	Total				$	49			$	300
	________________
	-1	The fair value shown for natural gas contracts is comprised of derivative gross volumes totaling 489 billion cubic feet (Bcf) or a net 101 Bcf long position.  Of the net long position, basis swaps constitute 73 Bcf.
	-2	Natural gas contracts are presented on a net basis in the Condensed Consolidated Balance Sheets. Natural gas contracts 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 derivative assets and liabilities was a $26 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 offset by collateral netting of $9 million:
	Offsetting of Natural Gas Derivative Assets and Liabilities
			31-Dec-12
			Gross Amounts Recognized (1)				Gross Amounts Offset in the Consolidated Balance Sheets				Net Amount Presented in the Consolidated Balance Sheets (2)
			(in millions)
	Current Assets: Non-trading derivative assets		$	42			$	(6	)		$	36
	Other Assets: Non-trading derivative assets		7				(1		)		6
	Current Liabilities: Non-trading derivative liabilities		(28		)		14				(14		)
	Other Liabilities: Non-trading derivative liabilities		(4		)		2				(2		)
	Total		$	17			$	9			$	26
	________________
	-1	Gross amounts recognized include some derivative assets and liabilities that are not subject to master netting arrangements.
	-2	The derivative assets and liabilities on the 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.
	Fair Value of Derivative Instruments
					September 30, 2013
	Total derivatives not designated		Balance Sheet		Derivative				Derivative
	as hedging instruments		Location		Assets				Liabilities
					Fair Value				Fair Value
					(in millions)
	Natural gas derivatives (1) (3)		Current Assets: Non-trading derivative assets		$	26			$	—
	Natural gas derivatives (1) (3)		Other Assets: Non-trading derivative assets		10				—
	Natural gas derivatives (1) (2) (3)		Current Liabilities: Non-trading derivative liabilities		8				17
	Natural gas derivatives (1) (3)		Other Liabilities: Non-trading derivative liabilities		—				4
	Indexed debt securities derivative		Current Liabilities		—				382
	Total				$	44			$	403
	________________
	-1	The fair value shown for natural gas contracts is comprised of derivative gross volumes totaling 607 Bcf or a net 24 Bcf long position.  Of the net long position, basis swaps constitute 89 Bcf.
	-2	The $17 million Derivative Current Liability includes $2 million related to physical forwards purchased from Enable.
	-3	Natural gas contracts are presented on a net basis in the Condensed Consolidated Balance Sheets. Natural gas contracts 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 derivative assets and liabilities was a $29 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 offset by collateral netting of $6 million:
	Offsetting of Natural Gas Derivative Assets and Liabilities
			September 30, 2013
			Gross Amounts Recognized (1)				Gross Amounts Offset in the Consolidated Balance Sheets				Net Amount Presented in the Consolidated Balance Sheets (2)
			(in millions)
	Current Assets: Non-trading derivative assets		$	34			$	(8	)		$	26
	Other Assets: Non-trading derivative assets		10				—				10
	Current Liabilities: Non-trading derivative liabilities		(17		)		11				(6		)
	Other Liabilities: Non-trading derivative liabilities		(4		)		3				(1		)
	Total		$	23			$	6			$	29
	________________
-1	Gross amounts recognized include some derivative assets and liabilities that are not subject to master netting arrangements.
-2	The derivative assets and liabilities on the 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.
For CenterPoint Energy’s price stabilization activities of the Natural Gas Distribution business segment, the settled costs of derivatives are ultimately recovered through purchased gas adjustments. Accordingly, the net unrealized gains and losses associated with these contracts are recorded as net regulatory assets. Realized and unrealized gains and losses on other derivatives are recognized in the Condensed Statements of Consolidated Income as revenue for physical natural gas sales derivative contracts and as natural gas expense for financial natural gas derivatives and other physical natural gas derivatives. Unrealized gains and losses on indexed debt securities are recorded as Other Income (Expense) in the Condensed Statements of Consolidated Income.
Income Statement Impact of Derivative Activity
				Three Months Ended September 30,
Total derivatives not designated		Income Statement Location		2012				2013
as hedging instruments
				(in millions)
Natural gas derivatives		Gains (Losses) in Revenue		$	(21	)		$	11
Natural gas derivatives (1)		Gains (Losses) in Expense: Natural Gas		24				(2		)
Indexed debt securities derivative		Gains (Losses) in Other Income (Expense)		(52		)		(42		)
Total				$	(49	)		$	(33	)
Income Statement Impact of Derivative Activity
				Nine Months Ended September 30,
Total derivatives not designated		Income Statement Location		2012				2013
as hedging instruments
				(in millions)
Natural gas derivatives		Gains (Losses) in Revenue		$	22			$	24
Natural gas derivatives (1) (2)		Gains (Losses) in Expense: Natural Gas		(44		)		(3		)
Indexed debt securities derivative		Gains (Losses) in Other Income (Expense)		(76		)		(120		)
Total				$	(98	)		$	(99	)
________________
-1	The Gains (Losses) in Expense: Natural Gas includes $-0- during the three months ended September 30, 2013 and $(3) million during the nine months ended September 30, 2013 related to physical forwards purchased from Enable.
-2	The Gains (Losses) in Expense: Natural Gas includes $(38) million and $-0- of costs during the nine months ended September 30, 2012 and 2013, respectively, associated with price stabilization activities of the Natural Gas Distribution business segment that will be ultimately recovered through purchased gas adjustments.
(c)	Credit Risk Contingent Features
CenterPoint Energy enters into financial derivative contracts containing material adverse change provisions.  These provisions could require CenterPoint Energy to post additional collateral if the Standard & Poor’s Ratings Services or Moody’s Investors Service, Inc. credit ratings of CenterPoint Energy, Inc. or its subsidiaries are downgraded.  The total fair value of the derivative instruments that contain credit risk contingent features that are in a net liability position at December 31, 2012 and September 30, 2013 was $5 million and $3 million, respectively.  The aggregate fair value of assets that were posted as collateral was less than $1 million at both December 31, 2012 and September 30, 2013.  If all derivative contracts (in a net liability position) containing credit risk contingent features were triggered at December 31, 2012 and September 30, 2013, $5 million and $3 million, respectively, of additional assets would be required to be posted as collateral.

Fair_Value_Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
Fair Value Disclosures [Text Block]	'
	Fair Value Measurements
	Assets and liabilities that are recorded at fair value in the Condensed Consolidated Balance Sheets are categorized based upon the level of judgment associated with the inputs used to measure their value. Hierarchical levels, as defined below and directly related to the amount of subjectivity associated with the inputs to fair valuations of these assets and liabilities, are as follows:
	Level 1: Inputs are unadjusted quoted prices in active markets for identical assets or liabilities at the measurement date. The types of assets carried at Level 1 fair value generally are exchange-traded derivatives and equity securities.
	Level 2: Inputs, other than quoted prices included in Level 1, are observable for the asset or liability, either directly or indirectly. Level 2 inputs include quoted prices for similar instruments in active markets, and inputs other than quoted prices that are observable for the asset or liability. Fair value assets and liabilities that are generally included in this category are derivatives with fair values based on inputs from actively quoted markets.  A market approach is utilized to value CenterPoint Energy’s Level 2 assets or liabilities.
	Level 3: Inputs are unobservable for the asset or liability, and include situations where there is little, if any, market activity for the asset or liability. Unobservable inputs reflect CenterPoint Energy’s judgments about the assumptions market participants would use in pricing the asset or liability since limited market data exists. CenterPoint Energy develops these inputs based on the best information available, including CenterPoint Energy’s own data. A market approach is utilized to value CenterPoint Energy’s Level 3 assets or liabilities. Currently, CenterPoint Energy’s Level 3 assets and liabilities are comprised of physical forward contracts and options. Level 3 physical forward contracts are valued using a discounted cash flow model which includes illiquid forward price curve locations (ranging from $2.85 to $4.48 per one million British thermal units) as an unobservable input. Level 3 options are valued through Black-Scholes (including forward start) option models which include option volatilities (ranging from 0 to 52%) as an unobservable input.  CenterPoint Energy’s Level 3 derivative assets and liabilities consist of both long and short positions (forwards and options) and their fair value is sensitive to forward prices and volatilities. If forward prices decrease, CenterPoint Energy’s long forwards lose value whereas its short forwards gain in value.  If volatility decreases, CenterPoint Energy’s long options lose value whereas its short options gain in value.
	CenterPoint Energy determines the appropriate level for each financial asset and liability on a quarterly basis and recognizes transfers between levels at the end of the reporting period.  For the nine months ended September 30, 2013, there were no transfers between Level 1 and 2 with regard to Natural Gas derivatives. CenterPoint Energy also recognizes purchases of Level 3 financial assets and liabilities at their fair market value at the end of the reporting period.
	The following tables present information about CenterPoint Energy’s assets and liabilities (including derivatives that are presented net) measured at fair value on a recurring basis as of December 31, 2012 and September 30, 2013, and indicate the fair value hierarchy of the valuation techniques utilized by CenterPoint Energy to determine such fair value.
		Quoted Prices in			Significant Other			Significant			Netting			Balance
		Active Markets			Observable			Unobservable			Adjustments (1)			as of
		for Identical Assets			Inputs			Inputs						31-Dec-12
		(Level 1)			(Level 2)			(Level 3)
		(in millions)
	Assets
	Corporate equities	$	542		$	—		$	—		$	—		$	542
	Investments, including money	76			—			—			—			76
	market funds
	Natural gas derivatives	1			40			7			(6		)	42
	Total assets	$	619		$	40		$	7		$	(6	)	$	660
	Liabilities
	Indexed debt securities derivative	$	—		$	268		$	—		$	—		$	268
	Natural gas derivatives	5			21			5			(15		)	16
	Total liabilities	$	5		$	289		$	5		$	(15	)	$	284
	________________
	-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 $9 million posted with the same counterparties.
		Quoted Prices in			Significant Other			Significant			Netting			Balance
		Active Markets			Observable			Unobservable			Adjustments (1)			as of
		for Identical Assets			Inputs			Inputs						30-Sep-13
		(Level 1)			(Level 2)			(Level 3)
		(in millions)
	Assets
	Corporate equities	$	691		$	—		$	—		$	—		$	691
	Investments, including money	65			—			—			—			65
	market funds
	Natural gas derivatives	4			33			7			(8		)	36
	Total assets	$	760		$	33		$	7		$	(8	)	$	792
	Liabilities
	Indexed debt securities derivative	$	—		$	382		$	—		$	—		$	382
	Natural gas derivatives (2)	4			15			2			(14		)	7
	Total liabilities	$	4		$	397		$	2		$	(14	)	$	389
	________________
	-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 $6 million posted with the same counterparties.
	-2	The (Level 2) Natural gas derivative liability of $15 million includes $2 million related to physical forwards purchased from Enable.
	The following table presents additional information about assets or liabilities, including derivatives that are measured at fair value on a recurring basis for which CenterPoint Energy has utilized Level 3 inputs to determine fair value:
		Fair Value Measurements Using Significant
		Unobservable Inputs (Level 3)
		Derivative assets and liabilities, net
		Three Months Ended September 30,						Nine Months Ended September 30,
		2012			2013			2012			2013
		(in millions)
	Beginning balance	$	3		$	4		$	6		$	2
	Total gains (1)	—			2			4			5
	Total settlements (1)	(2		)	(1		)	(8		)	(2		)
	Transfers out of Level 3	—			—			(1		)	—
	Ending balance (2)	$	1		$	5		$	1		$	5
	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	$	(1	)	$	2		$	—		$	4
	________________
	-1	CenterPoint Energy did not have Level 3 unrealized gains (losses) or settlements related to price stabilization activities of the Natural Gas Distribution business segment during either the three or nine months ended September 30, 2012 or 2013.
	-2	CenterPoint Energy did not have significant Level 3 purchases, sales or transfers into Level 3 during either the three or nine months ended September 30, 2012 or 2013.
	Estimated Fair Value of Financial Instruments
	The fair values of cash and cash equivalents, investments in debt and equity securities classified as “trading” and short-term borrowings are estimated to be approximately equivalent to carrying amounts and have been excluded from the table below. The fair values of non-trading derivative assets and liabilities and CenterPoint Energy’s 2.0% Zero-Premium Exchangeable Subordinated Notes due 2029 (ZENS) indexed debt securities derivative are stated at fair value and are excluded from the table below.  The fair value of each debt instrument is determined by multiplying the principal amount of each debt instrument by the market price. These assets and liabilities, which are not measured at fair value in the Condensed Consolidated Balance Sheets but for which the fair value is disclosed, would be classified as Level 1 in the fair value hierarchy.
		December 31, 2012						September 30, 2013
		Carrying			Fair			Carrying			Fair
		Amount			Value			Amount			Value
	(in millions)
Financial assets:
Notes receivable - affiliated companies	$	—		$	—		$	363		$	362
Financial liabilities:
Long-term debt	$	9,619		$	10,807		$	8,170		$	8,807

Unconsolidated_Affiliates_Note

Unconsolidated Affiliates (Notes)	9 Months Ended
	Sep. 30, 2013
Equity Method Investments and Joint Ventures [Abstract]	'
Equity Method Investments and Joint Ventures Disclosure [Text Block]	'
	Unconsolidated Affiliates
	As discussed in Note 1, on May 1, 2013 (the Closing Date) CERC Corp., OGE and ArcLight closed on the formation of Enable. Enable owns CenterPoint Midstream, which consists of substantially all of CERC Corp.’s former Interstate Pipelines and Field Services business segments. As a result, CenterPoint Energy no longer has Interstate Pipelines or Field Services business segments. Equity earnings associated with CenterPoint Energy's interest in Enable and equity earnings associated with its retained 25.05% interest in SESH are now reported under the Midstream Investments segment. For a further description of CenterPoint Energy's reportable business segments, see Note 14.
	The formation of Enable by CenterPoint Energy has been considered a contribution of in-substance real estate to a limited partnership as the businesses are composed of, and reliant upon, substantial real estate assets and integral equipment. Real estate assets and integral equipment primarily includes gas transmission pipelines, compressor station equipment, rights of way, storage and processing assets, and long-term customer contracts. Accordingly, CenterPoint Energy did not recognize a gain or loss upon contribution and recorded its investment in Enable using the equity method of accounting based on the historical cost of the contributed assets and liabilities as of the Closing Date. Approximately $5.8 billion of assets and $1.5 billion of liabilities (which includes the Term Loan and the indebtedness owed to CERC, both discussed below, of $1.05 billion and $363 million, respectively) were contributed by CERC Corp. CenterPoint Energy has the ability to significantly influence the operating and financial policies of Enable and, accordingly, recorded an equity method investment of $4.3 billion in Enable on the Closing Date. Pursuant to the MFA, CenterPoint Energy retained certain assets and liabilities historically held by CenterPoint Midstream such as balances relating to federal income taxes and benefit plan obligations.
	CenterPoint Energy’s investment in Enable is considered to be a VIE because the power to direct the activities that most significantly impact Enable’s economic performance does not reside with the holders of equity investment at risk. However, CenterPoint Energy is not considered the primary beneficiary of Enable since it does not have the power to direct the activities of Enable that are considered most significant to the economic performance of Enable. As discussed above, CenterPoint Energy accounts for its investment in Enable using the equity method of accounting. Under the equity method, the investment will be adjusted each period for contributions made, distributions received and CenterPoint Energy’s share of Enable’s comprehensive income. CenterPoint Energy’s maximum exposure to loss related to Enable is limited to its equity investment as presented in the Condensed Consolidated Balance Sheet at September 30, 2013 and its guarantee of Enable’s $1.05 billion Term Loan and certain other guarantees as discussed in Note 12. CenterPoint Energy evaluates its equity method investments for impairment when events or changes in circumstances indicate there is a loss in value of the investment that is other than a temporary decline. See Note 1 for further discussion on Enable’s ownership structure.
	Effective on the Closing Date, CenterPoint Energy and Enable entered into a Services Agreement, Employee Transition Agreement, Transitional Services Agreement and other agreements (collectively, Transition Agreements) whereby CenterPoint Energy agreed to provide certain support services to Enable such as accounting, legal, risk management and treasury functions. Additionally, CenterPoint Energy provides seconded employees to Enable to support its operations. CenterPoint Energy does not anticipate extending the services provided to Enable, including providing seconded employees, beyond December 31, 2014. CenterPoint Energy did not transfer any employees to Enable at formation of the partnership or at any time during the nine months ended September 30, 2013. CenterPoint Energy billed Enable for reimbursement of transitional services, including the costs of seconded employees, of $42 million and $70 million during the three and five months ended September 30, 2013, respectively, under the Transition Agreements. Actual transitional services costs are recorded net of reimbursements received from Enable.
	Enable, at its discretion, has the right to select and offer employment to seconded employees from CenterPoint Energy. As of September 30, 2013, CenterPoint Energy determined it cannot reasonably estimate the impact of the costs associated with the termination of employees related to the formation of Enable or transfer of employees from CenterPoint Energy to Enable, including the impact of the changes to the actuarial determination of employee benefit plan obligations. Pursuant to the Transition Agreements, Enable has agreed to reimburse CenterPoint Energy for severance and termination costs related to the termination of CenterPoint Energy's seconded employees, including any potential benefit-related costs, regardless of whether such seconded employees are offered employment by Enable.
	On the Closing Date, Enable entered into a $1.05 billion three-year senior unsecured term loan facility (the Term Loan) with third parties and repaid $1.05 billion of affiliated notes payable (Affiliated Notes Payable) owed to CERC. CERC provided a guarantee of Enable's obligations under the Term Loan. The guarantee is subordinated to all senior debt of CERC. Certain of the entities contributed to Enable by CERC are obligated on approximately $363 million of indebtedness owed to CERC bearing interest at an annual rate of 2.10% to 2.45% and scheduled to mature in 2017.
	CERC has certain put rights, and Enable has certain call rights, exercisable with respect to the 25.05% interest in SESH retained by CERC, under which CERC would contribute its retained interest in SESH, in exchange for a specified number of limited partnership units in Enable and a cash payment, payable either from CERC to Enable or from Enable to CERC, for changes in the value of SESH.
	As of September 30, 2013, CenterPoint Energy held an approximate 58.3% interest in Enable and a 25.05% interest in SESH.
	Investment in Unconsolidated Affiliates:
		31-Dec-12		September 30, 2013
		(in millions)
	Enable	$	—	$	4,326
	SESH	404		199
	Other	1		—
	Total	$	405	$	4,525
	Equity in Earnings of Unconsolidated Affiliates, net:
		Three Months Ended September 30,				Nine Months Ended September 30,
		2012		2013		2012		2013
		(in millions)
	Enable	$	—	$	77	$	—	$	110
	SESH	8		3		20		12
	Other	—		—		5		—
		$	8	$	80	$	25	$	122
	Summarized income information for Enable from formation on May 1, 2013 through September 30, 2013, based on the Enogex assets recorded at estimated fair value on the Closing Date, is as follows (in millions):
	Operating Revenues	$	1,298
	Gross Margin	545
	Operating Income	207
	Net Income from Controlling Interest	188
	CenterPoint Energy's 58.3% interest	$	110
	Summarized balance sheet information for Enable as of September 30, 2013 is as follows (in millions):
	Current assets	$	428
	Non-current assets	10,537
	Current liabilities	622
	Non-current liabilities	2,140
	Enable concluded that the formation of Enable is considered a business combination, and CenterPoint Midstream is the acquirer for accounting purposes.  Under this method, the fair value of the consideration paid by CenterPoint Midstream for Enogex is allocated to the assets acquired and liabilities assumed on the Closing Date based on their fair value.  Enogex’s assets, liabilities and equity were accordingly adjusted to estimated fair value as of May 1, 2013.  Determining the fair value of assets and liabilities is judgmental in nature and often involves the use of significant estimates and assumptions.  Enable used appraisers to assist in the determination of the estimated fair value of certain assets and liabilities contributed by Enogex.
	CenterPoint Energy recorded its 58.3% interest in Enable’s net income for the period May 1, 2013 through September 30, 2013 of $110 million, which includes the depreciation and amortization of the step-up in fair value of Enogex assets at Enable.
	As of September 30, 2013, CenterPoint Energy’s investment in Enable, recorded at the historical cost of the contributed CenterPoint Midstream assets and liabilities, was $439 million less than CenterPoint Energy’s proportionate share of Enable’s limited partners’ capital. This difference in CenterPoint Energy’s investment basis included $229 million related to CenterPoint Energy’s proportionate share of Enable’s goodwill arising from its acquisition of Enogex, and therefore will not be recognized by CenterPoint Energy. CenterPoint Energy will accrete the remaining $210 million basis difference over 30 years.
	Distributions received from Enable were approximately $36 million during the three and five months ended September 30, 2013.

Goodwill

Goodwill	9 Months Ended
	Sep. 30, 2013
Goodwill and Intangible Assets Disclosure [Abstract]	'
Goodwill and Intangible Assets Disclosure [Text Block]	'
	Goodwill
	Goodwill by reportable business segment as of December 31, 2012 and changes in the carrying amount of goodwill as of September 30, 2013 are as follows (in millions):
		31-Dec-12		Contributed to Enable		September 30, 2013
	Natural Gas Distribution	$	746	$	—	$	746
	Interstate Pipelines	579		579		—
	Competitive Natural Gas Sales and Services	83		—		83
	Field Services	49		49		—
	Other Operations	11		—		11
	Total	$	1,468	$	628	$	840
	CenterPoint Energy performs its goodwill impairment tests at least annually and evaluates goodwill when events or changes in circumstances indicate that its carrying value may not be recoverable. The impairment evaluation for goodwill is performed by using a two-step process. In the first step, the fair value of each reporting unit is compared with the carrying amount of the reporting unit, including goodwill. The estimated fair value of the reporting unit is generally determined on the basis of discounted cash flows. If the estimated fair value of the reporting unit is less than the carrying amount of the reporting unit, then a second step must be completed in order to determine the amount of the goodwill impairment that should be recorded. In the second step, the implied fair value of the reporting unit's goodwill is determined by allocating the reporting unit's fair value to all of its assets and liabilities other than goodwill (including any unrecognized intangible assets) in a manner similar to a purchase price allocation. The resulting implied fair value of the goodwill that results from the application of this second step is then compared to the carrying amount of the goodwill and an impairment charge is recorded for the difference.
	CenterPoint Energy performed its annual impairment test in the third quarter of 2013 and determined, based on the results of the first step, that no impairment charge was required for any reportable segment.

Capital_Stock

Capital Stock	9 Months Ended
	Sep. 30, 2013
Class of Stock Disclosures [Abstract]	'
Capital Stock	'
	Capital Stock
	CenterPoint Energy, Inc. has 1,020,000,000 authorized shares of capital stock, comprised of 1,000,000,000 shares of $0.01 par value common stock and 20,000,000 shares of $0.01 par value preferred stock. At December 31, 2012, 427,599,730 shares of CenterPoint Energy, Inc. common stock were issued and 427,599,564 shares were outstanding. At September 30, 2013, 428,640,333 shares of CenterPoint Energy, Inc. common stock were issued and 428,640,167 shares were outstanding. Outstanding common shares exclude 166 treasury shares at both December 31, 2012 and September 30, 2013.

ShortTerm_Borrowings_and_Longt

Short-Term Borrowings and Long-term Debt	9 Months Ended
	Sep. 30, 2013
Debt Disclosure [Abstract]	'
Short-term Borrowings and Long-term Debt [Text Block]	'
	Short-term Borrowings and Long-term Debt
	(a)	Short-term Borrowings
	Inventory Financing. Gas Operations has asset management agreements associated with its utility distribution service in Arkansas, north Louisiana and Oklahoma that extend through 2015. Pursuant to the provisions of the agreements, Gas Operations sells natural gas and agrees to repurchase an equivalent amount of natural gas during the winter heating seasons at the same cost, plus a financing charge. These transactions are accounted for as a financing and had an associated principal obligation of $38 million and $70 million as of December 31, 2012 and September 30, 2013, respectively.
	(b)	Long-term Debt
	Debt Repayments. In April 2013, CERC Corp. retired approximately $365 million aggregate principal amount of its 7.875% senior notes at their maturity. The retirement of senior notes was financed by CERC Corp. with the issuance of commercial paper. In May 2013, CERC Corp. applied proceeds from Enable's May 1, 2013 debt repayment of $1.05 billion to the repayment of $357 million aggregate principal amount of its commercial paper and to the May 31, 2013 redemption of $160 million aggregate principal amount of its 5.95% senior notes due January 15, 2014 at 103.419% of their aggregate principal amount. On August 1, 2013, approximately $92 million aggregate principal amount of pollution control bonds issued on CenterPoint Energy's behalf were redeemed at 101% of their aggregate principal amount. These bonds had an interest rate of 4%, a maturity date of August 1, 2015 and were collateralized by first mortgage bonds of CenterPoint Houston. On October 15, 2013, approximately $59 million aggregate principal amount of pollution control bonds issued on CenterPoint Energy’s behalf were redeemed at 101% of their aggregate principal amount. These bonds had an interest rate of 4%, a maturity date of October 15, 2015 and were collateralized by first mortgage bonds of CenterPoint Houston.
	Credit Facilities. As of December 31, 2012 and September 30, 2013, CenterPoint Energy, CenterPoint Houston and CERC Corp. had the following revolving credit facilities and utilization of such facilities (in millions):
		December 31, 2012								September 30, 2013
		Size of		Loans		Letters		Commercial		Size of		Loans		Letters		Commercial
		Facility				of Credit		Paper		Facility				of Credit		Paper
	CenterPoint Energy	$	1,200	$	—	$	7	$	—	$	1,200	$	—	$	6	$	—
	CenterPoint Houston	300		—		4		—		300		—		4		—
	CERC Corp.	950		—		—		—		600		—		—		—
	Total	$	2,450	$	—	$	11	$	—	$	2,100	$	—	$	10	$	—
	CenterPoint Energy’s $1.2 billion revolving credit facility, which is scheduled to terminate on September 9, 2018, can be drawn at the London Interbank Offered Rate (LIBOR) plus 150 basis points based on CenterPoint Energy’s current credit ratings. The revolving credit facility contains a financial covenant which limits CenterPoint Energy’s consolidated debt (excluding transition and system restoration bonds) to an amount not to exceed 65% of CenterPoint Energy’s consolidated capitalization. The financial covenant limit will temporarily increase from 65% to 70% if CenterPoint Houston experiences damage from a natural disaster in its service territory and CenterPoint Energy certifies to the administrative agent that CenterPoint Houston has incurred system restoration costs reasonably likely to exceed $100 million in a consecutive twelve-month period, all or part of which CenterPoint Houston 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.
	CenterPoint Houston’s $300 million revolving credit facility, which is scheduled to terminate on September 9, 2018, can be drawn at LIBOR plus 125 basis points based on CenterPoint Houston’s current credit ratings. The revolving credit facility contains a financial covenant which limits CenterPoint Houston’s consolidated debt (excluding transition and system restoration bonds) to an amount not to exceed 65% of CenterPoint Houston's consolidated capitalization.
	CERC Corp.’s $600 million revolving credit facility, which is scheduled to terminate on September 9, 2018, can be drawn at LIBOR plus 150 basis points based on CERC Corp.’s current credit ratings. The revolving credit facility contains a financial covenant which limits CERC’s consolidated debt to an amount not to exceed 65% of CERC’s consolidated capitalization.

Income_Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2013
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	Income Taxes
	The effective tax rate for the three and nine months ended September 30, 2013 was 34% and 67%, respectively, compared to 92% and 48%, respectively, for the same periods in 2012. The lower effective tax rate for the three months ended September 30, 2013 was primarily due to the tax effects associated with the goodwill impairment for the same period in 2012. In addition, CenterPoint Energy recognized a tax benefit of $8 million based on the settlement of outstanding tax claims for the 2002 and 2003 audit cycles in 2013. The higher effective tax rate for the nine month period ended September 30, 2013 compared to the same period in 2012 is primarily due to additional tax expense of $225 million recorded for the book to tax basis difference arising from the formation of Enable. In addition, CenterPoint Energy recognized a tax benefit of $29 million associated with the remeasurement of state deferred taxes related to the formation of Enable.
	The following table summarizes CenterPoint Energy’s unrecognized tax benefits (expenses) at December 31, 2012 and September 30, 2013:
		December 31,			September 30,
		2012			2013
		(in millions)
	Unrecognized tax expenses	$	(23	)	$	—
	Portion of unrecognized tax expenses that, if recognized,	(3		)	—
	would increase the effective income tax rate
	Interest accrued on unrecognized tax expenses	(8		)	—
	CenterPoint Energy does not expect the change to the amount of unrecognized tax expenses over the twelve months ending September 30, 2014 to materially impact the financial position of CenterPoint Energy.
	CenterPoint Energy’s consolidated federal income tax returns have been audited by the Internal Revenue Service (IRS) and settled through the 2009 tax year. On July 9, 2013, CenterPoint Energy received notification that the Joint Committee of Taxation had approved its outstanding tax claims related to the 2002 and 2003 audit cycles. As a result, CenterPoint Energy recorded the settlement of all unrecognized tax expenses during the three month period ended September 30, 2013. CenterPoint Energy is currently under examination by the IRS for tax years 2010 and 2011. CenterPoint Energy has considered the effects of these examinations in its accrual for settled issues and liability for uncertain income tax positions as of September 30, 2013.

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2013
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	Commitments and Contingencies
	(a)	Natural Gas Supply Commitments
	Natural gas supply commitments include natural gas contracts related to CenterPoint Energy’s Natural Gas Distribution and Competitive Natural Gas Sales and Services business segments, which have various quantity requirements and durations, that are not classified as non-trading derivative assets and liabilities in CenterPoint Energy’s Condensed Consolidated Balance Sheets as of December 31, 2012 and September 30, 2013 as these contracts meet the exception to be classified as “normal purchases contracts” or do not meet the definition of a derivative. Natural gas supply commitments also include natural gas transportation contracts that do not meet the definition of a derivative. As of September 30, 2013, minimum payment obligations for natural gas supply commitments are approximately $143 million for the remaining three months in 2013, $449 million in 2014, $382 million in 2015, $309 million in 2016, $250 million in 2017 and $366 million after 2017.
	(b)	Legal, Environmental and Other Regulatory Matters
	Legal Matters
	Gas Market Manipulation Cases.  CenterPoint Energy, CenterPoint Houston or their predecessor, Reliant Energy, Incorporated (Reliant Energy), and certain of their former subsidiaries have been named as defendants in certain lawsuits described below. Under a master separation agreement between CenterPoint Energy and a former subsidiary, Reliant Resources, Inc. (RRI), CenterPoint Energy and its subsidiaries are entitled to be indemnified by RRI and its successors for any losses, including certain attorneys’ fees and other costs, arising out of these lawsuits.  In May 2009, RRI sold its Texas retail business to a subsidiary of NRG Energy, Inc. (NRG) and RRI changed its name to RRI Energy, Inc. In December 2010, Mirant Corporation merged with and became a wholly owned subsidiary of RRI, and RRI changed its name to GenOn Energy, Inc. (GenOn). In December 2012, NRG acquired GenOn through a merger in which GenOn became a wholly owned subsidiary of NRG. None of the sale of the retail business, the merger with Mirant Corporation, or the acquisition of GenOn by NRG alters RRI’s (now GenOn’s) contractual obligations to indemnify CenterPoint Energy and its subsidiaries, including CenterPoint Houston, for certain liabilities, including their indemnification obligations regarding the gas market manipulation litigation, nor does it affect the terms of existing guarantee arrangements for certain GenOn gas transportation contracts discussed below.
	A large number of lawsuits were filed against numerous gas market participants in a number of federal and western state courts in connection with the operation of the natural gas markets in 2000-2002. CenterPoint Energy’s former affiliate, RRI, was a participant in gas trading in the California and Western markets. These lawsuits, many of which were filed as class actions, allege violations of state and federal antitrust laws. Plaintiffs in these lawsuits are seeking a variety of forms of relief, including, among others, recovery of compensatory damages (in some cases in excess of $1 billion), a trebling of compensatory damages, full consideration damages and attorneys’ fees. CenterPoint Energy and/or Reliant Energy were named in approximately 30 of these lawsuits, which were instituted between 2003 and 2009. CenterPoint Energy and its affiliates have since been released or dismissed from all but one such case. CenterPoint Energy Services, Inc. (CES), a subsidiary of CERC Corp., is a defendant in a case now pending in federal court in Nevada alleging a conspiracy to inflate Wisconsin natural gas prices in 2000-2002.  In July 2011, the court issued an order dismissing the plaintiffs’ claims against other defendants in the case, each of whom had demonstrated FERC jurisdictional sales for resale during the relevant period, based on federal preemption.  The plaintiffs appealed this ruling to the United States Court of Appeals for the Ninth Circuit, which reversed the trial court's dismissal of the plaintiffs' claims. In August 2013, the other defendants filed a petition for review with the U.S. Supreme Court. CenterPoint Energy believes that CES is not a proper defendant in this case and will continue to pursue a dismissal.  CenterPoint Energy does not expect the ultimate outcome of this matter to have a material impact on its financial condition, results of operations or cash flows.
	Environmental Matters
	Manufactured Gas Plant Sites. CERC and its predecessors operated manufactured gas plants (MGPs) in the past. In Minnesota, CERC has completed remediation on two sites, other than ongoing monitoring and water treatment. There are five remaining sites in CERC’s Minnesota service territory. CERC believes that it has no liability with respect to two of these sites.
	At September 30, 2013, CERC had recorded a liability of $13 million for remediation of these Minnesota sites. The estimated range of possible remediation costs for the sites for which CERC believes it may have responsibility was $6 million to $41 million based on remediation continuing for 30 to 50 years. The cost estimates are based on studies of a site or industry average costs for remediation of sites of similar size. The actual remediation costs will be dependent upon the number of sites to be remediated, the participation of other potentially responsible parties (PRPs), if any, and the remediation methods used. The Minnesota Public Utilities Commission includes approximately $285,000 annually in rates to fund normal ongoing remediation costs.  As of September 30, 2013, CERC had collected $6.1 million from insurance companies to be used for future environmental remediation.
	In addition to the Minnesota sites, the United States Environmental Protection Agency and other regulators have investigated MGP sites that were owned or operated by CERC or may have been owned by one of its former affiliates. CERC and CenterPoint Energy do not expect the ultimate outcome of these investigations will have a material adverse impact on the financial condition, results of operations or cash flows of either CenterPoint Energy or CERC.
	Asbestos. Some facilities owned by CenterPoint Energy contain or have contained asbestos insulation and other asbestos-containing materials. CenterPoint Energy or its subsidiaries have been named, along with numerous others, as a defendant in lawsuits filed by a number of individuals who claim injury due to exposure to asbestos. Some of the claimants have worked at locations owned by subsidiaries of CenterPoint Energy, but most existing claims relate to facilities previously owned by CenterPoint Energy’s subsidiaries. CenterPoint Energy anticipates that additional claims like those received may be asserted in the future. In 2004 and early 2005, CenterPoint Energy sold its generating business, to which most of these claims relate, to a company which is now an affiliate of NRG. Under the terms of the arrangements regarding separation of the generating business from CenterPoint Energy and its sale of that business, ultimate financial responsibility for uninsured losses from claims relating to the generating business has been assumed by the NRG affiliate, but CenterPoint Energy has agreed to continue to defend such claims to the extent they are covered by insurance maintained by CenterPoint Energy, subject to reimbursement of the costs of such defense by the NRG affiliate. Although their ultimate outcome cannot be predicted at this time, CenterPoint Energy intends to continue vigorously contesting claims that it does not consider to have merit and, based on its experience to date, does not expect these matters, either individually or in the aggregate, to have a material adverse effect on CenterPoint Energy’s financial condition, results of operations or cash flows.
	Other Environmental. From time to time CenterPoint Energy identifies the presence of environmental contaminants on property where its subsidiaries conduct or have conducted operations.  Other such sites involving contaminants may be identified in the future.  CenterPoint Energy has and expects to continue to remediate identified sites consistent with its legal obligations. From time to time CenterPoint Energy has received notices from regulatory authorities or others regarding its status as a PRP in connection with sites found to require remediation due to the presence of environmental contaminants. In addition, CenterPoint Energy has been named from time to time as a defendant in litigation related to such sites. Although the ultimate outcome of such matters cannot be predicted at this time, CenterPoint Energy does not expect, based on its experience to date, these matters, either individually or in the aggregate, to have a material adverse effect on CenterPoint Energy’s financial condition, results of operations or cash flows.
	Other Proceedings
	CenterPoint Energy is involved in other legal, environmental, tax and regulatory proceedings before various courts, regulatory commissions and governmental agencies regarding matters arising in the ordinary course of business. From time to time, CenterPoint Energy is also a defendant in legal proceedings with respect to claims brought by various plaintiffs against broad groups of participants in the energy industry. Some of these proceedings involve substantial amounts. CenterPoint Energy regularly analyzes current information and, as necessary, provides accruals for probable liabilities on the eventual disposition of these matters. CenterPoint Energy does not expect the disposition of these matters to have a material adverse effect on CenterPoint Energy’s financial condition, results of operations or cash flows.
	(c)	Guarantees
	Prior to the distribution of CenterPoint Energy’s ownership in RRI to its shareholders, CERC had guaranteed certain contractual obligations of what became RRI’s trading subsidiary.  When the companies separated, RRI agreed to secure CERC against obligations under the guarantees RRI had been unable to extinguish by the time of separation.  Pursuant to such agreement, as amended in December 2007, RRI (now GenOn) agreed to provide to CERC cash or letters of credit as security against CERC’s obligations under its remaining guarantees for demand charges under certain gas transportation agreements if and to the extent changes in market conditions expose CERC to a risk of loss on those guarantees based on an annual calculation, with any required collateral to be posted each December.  The undiscounted maximum potential payout of the demand charges under these transportation contracts, which will be in effect until 2018, was approximately $62 million as of September 30, 2013.  Based on market conditions in the fourth quarter of 2013 at the time the most recent annual calculation was made under the agreement, GenOn was not obligated to post any security. If GenOn should fail to perform the contractual obligations, CERC could have to honor its guarantee and, in such event, any collateral then provided as security may be insufficient to satisfy CERC’s obligations.
	CenterPoint Energy, Inc. has provided guarantees (CenterPoint Midstream Guarantees) with respect to the performance of certain obligations of Enable under long-term gas gathering and treating agreements with an indirect wholly owned subsidiary of Encana Corporation and an indirect wholly owned subsidiary of Royal Dutch Shell plc. As of September 30, 2013, CenterPoint Energy, Inc. had guaranteed Enable's obligations up to an aggregate amount of $100 million under these agreements. CERC Corp. has provided guarantees (CERC Midstream Guarantees) with respect to the performance of certain obligations of EGT under certain contractual arrangements with third parties, which guarantees are scheduled to expire in June 2015 and December 2018. The maximum aggregate amount payable by CERC Corp. under these guarantees is $53.2 million. The aggregate dollar amount of the obligations covered by the CERC Midstream Guarantees varies over time. The obligations supported by the CERC Midstream Guarantees for the months of September and October 2013 totaled less than $1 million. Under the terms of the omnibus agreement entered into in connection with the closing of the formation of Enable, Enable and CenterPoint Energy, Inc. have agreed to use commercially reasonable efforts and cooperate with each other to terminate the CenterPoint Midstream Guarantees and the CERC Midstream Guarantees, and to release CenterPoint Energy, Inc. or CERC Corp. from such guarantees by causing Enable or one of its subsidiaries to enter into substitute guarantees or to assume the CenterPoint Midstream Guarantees or CERC Midstream Guarantees, as applicable. CERC Corp. has also provided a guarantee of collection of Enable's obligations under its $1.05 billion three-year unsecured term loan facility, which guarantee is subordinated to all senior debt of CERC Corp.

Earnings_Per_Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]	'
Earnings Per Share	'
	Earnings Per Share
	The following table reconciles numerators and denominators of CenterPoint Energy’s basic and diluted earnings per share calculations:
		Three Months Ended September 30,				Nine Months Ended September 30,
		2012		2013		2012		2013
		(in millions, except share and per share amounts)
	Net income	$	10	$	151	$	283	$	198
	Basic weighted average shares outstanding	427,406,000		428,628,000		427,086,000		428,389,000
	Plus: Incremental shares from assumed conversions:
	Stock options	230,000		97,000		222,000		93,000
	Restricted stock	2,347,000		2,142,000		2,347,000		2,142,000
	Diluted weighted average shares	429,983,000		430,867,000		429,655,000		430,624,000
	Basic earnings per share:
	Net income	$	0.02	$	0.35	$	0.66	$	0.46
	Diluted earnings per share:
	Net income	$	0.02	$	0.35	$	0.66	$	0.46

Reportable_Business_Segments

Reportable Business Segments	9 Months Ended
	Sep. 30, 2013
Segment Reporting [Abstract]	'
Reportable Business Segments	'
	Reportable Business Segments
	CenterPoint Energy’s determination of reportable business segments considers the strategic operating units under which CenterPoint Energy manages sales, allocates resources and assesses performance of various products and services to wholesale or retail customers in differing regulatory environments. CenterPoint Energy uses operating income as the measure of profit or loss for its business segments.
	CenterPoint Energy’s reportable business segments include the following: Electric Transmission & Distribution, Natural Gas Distribution, Competitive Natural Gas Sales and Services, Midstream Investments and Other Operations. The electric transmission and distribution function (CenterPoint Houston) is reported in the Electric Transmission & Distribution business segment. Natural Gas Distribution consists of intrastate natural gas sales to, and natural gas transportation and distribution for, residential, commercial, industrial and institutional customers. Competitive Natural Gas Sales and Services represents CenterPoint Energy’s non-rate regulated gas sales and services operations. Midstream Investments consists primarily of CenterPoint Energy’s investment in Enable and its retained interest in SESH. Other Operations consists primarily of other corporate operations which support all of CenterPoint Energy’s business operations.
	Prior to May 1, 2013, CenterPoint Energy also reported an Interstate Pipelines business segment, which included CenterPoint Energy’s interstate natural gas pipeline operations, and a Field Services business segment, which included CenterPoint Energy’s non-rate regulated natural gas gathering, processing and treating operations. As previously disclosed, the formation of Enable closed on May 1, 2013. Enable now owns substantially all of CenterPoint Energy’s former Interstate Pipelines and Field Services business segments, except for the retained interest in SESH. As a result, effective May 1, 2013, CenterPoint Energy reports equity earnings associated with its interest in Enable and equity earnings associated with its retained interest in SESH under a new Midstream Investments segment, and no longer has Interstate Pipelines and Field Services reporting segments prospectively.
	Financial data for business segments is as follows (in millions):
		For the Three Months Ended September 30, 2012
		Revenues from			Net				Operating
		External			Intersegment				Income (Loss)
		Customers			Revenues
	Electric Transmission & Distribution	$	748	(1)	$	—			$	242
	Natural Gas Distribution	351			4				5
	Competitive Natural Gas Sales and Services	382			7				(259		)
	Interstate Pipelines	92			30				48
	Field Services	129			12				55
	Other Operations	3			—				(3		)
	Eliminations	—			(53		)		—
	Consolidated	$	1,705		$	—			$	88
		For the Three Months Ended September 30, 2013
		Revenues from			Net				Operating
		External			Intersegment				Income (Loss)
		Customers			Revenues
	Electric Transmission & Distribution	$	745	(1)	$	—			$	239
	Natural Gas Distribution	375			6				5
	Competitive Natural Gas Sales and Services	516			4				2
	Midstream Investments	—			—				—			(3)
	Other Operations	4			—				(2		)
	Eliminations	—			(10		)		—
	Consolidated	$	1,640		$	—			$	244
		For the Nine Months Ended September 30, 2012
		Revenues from			Net				Operating				Total Assets
		External			Intersegment				Income (Loss)				as of December
		Customers			Revenues								31, 2012
	Electric Transmission & Distribution	$	1,955	(1)	$	—			$	540			$	11,174
	Natural Gas Distribution	1,560			15				135				4,775
	Competitive Natural Gas Sales and Services	1,204			18				(262		)		839
	Interstate Pipelines	262			112				160				4,004
	Field Services	324			26				153				2,453
	Other Operations	9			—				2				2,600			(4)
	Eliminations	—			(171		)		—				(2,974		)
	Consolidated	$	5,314		$	—			$	728			$	22,871
		For the Nine Months Ended September 30, 2013
		Revenues from			Net				Operating				Total Assets
		External			Intersegment				Income (Loss)				as of September 30, 2013
		Customers			Revenues
	Electric Transmission & Distribution	$	1,933	(1)	$	—			$	488			$	10,364
	Natural Gas Distribution	1,942			19				169				4,776
	Competitive Natural Gas Sales and Services	1,726			19				12				806
	Interstate Pipelines	133		(2)	53			(2)	72			(2)	—
	Field Services	178		(2)	18			(2)	73			(2)	—
	Midstream Investments	—			—				—				4,525			(3)
	Other Operations	10			—				(15		)		2,780			(4)
	Eliminations	—			(109		)		—				(1,676		)
	Consolidated	$	5,922		$	—			$	799			$	21,575
	________________
	-1	Sales to affiliates of NRG in the three months ended September 30, 2012 and 2013 represented approximately $196 million and $202 million, respectively, of CenterPoint Houston’s transmission and distribution revenues.  Sales to affiliates of Energy Future Holdings Corp. in the three months ended September 30, 2012 and 2013 represented approximately $49 million and $52 million, respectively, of CenterPoint Houston’s transmission and distribution revenues. Sales to affiliates of NRG in the nine months ended September 30, 2012 and 2013 represented approximately $488 million and $494 million, respectively, of CenterPoint Houston’s transmission and distribution revenues. Sales to affiliates of Energy Future Holdings Corp. in the nine months ended September 30, 2012 and 2013 represented approximately $123 million and $125 million, respectively, of CenterPoint Houston’s transmission and distribution revenues.
	-2	Results reflected in the nine months ended September 30, 2013 represent only January 2013 through April 2013.
	-3	Midstream Investments reported equity earnings of $77 million from Enable and $3 million of equity earnings from CenterPoint Energy’s retained interest in SESH for the three months ended September 30, 2013. Midstream Investments reported equity earnings of $110 million from Enable and $5 million of equity earnings from CenterPoint Energy’s retained interest in SESH for the five months ended September 30, 2013. Included in total assets of Midstream Investments as of September 30, 2013 is $4,326 million related to CenterPoint Energy’s investment in Enable and $199 million related to CenterPoint Energy’s retained interest in SESH.
	-4	Included in total assets of Other Operations as of December 31, 2012 and September 30, 2013 are pension and other postemployment related regulatory assets of $832 million and $787 million, respectively.

Subsequent_Events

Subsequent Events	9 Months Ended
	Sep. 30, 2013
Subsequent Events [Abstract]	'
Subsequent Events [Text Block]	'
	Subsequent Events
	On October 23, 2013, CenterPoint Energy’s board of directors declared a regular quarterly cash dividend of $0.2075 per share of common stock payable on December 10, 2013, to shareholders of record as of the close of business on November 15, 2013.

Employee_Benefit_Plans_Tables

Employee Benefit Plans (Tables)	9 Months Ended
	Sep. 30, 2013
Compensation and Retirement Disclosure [Abstract]	'
Schedule of Defined Benefit Plans Disclosures [Table Text Block]	'
	CenterPoint Energy’s net periodic cost includes the following components relating to pension and postretirement benefits:
		Three Months Ended September 30,
		2012								2013
		Pension				Postretirement				Pension			Postretirement
		Benefits (1)				Benefits				Benefits (1)			Benefits
		(in millions)
	Service cost	$	9			$	—			$	11		$	—
	Interest cost	25				6				22			5
	Expected return on plan assets	(30		)		(1		)		(33		)	(1		)
	Amortization of prior service credit	2				—				3			1
	Amortization of net loss	15				1				15			2
	Amortization of transition obligation	—				2				—			1
	Net periodic cost	$	21			$	8			$	18		$	8
		Nine Months Ended September 30,
		2012								2013
		Pension				Postretirement				Pension			Postretirement
		Benefits (1)				Benefits				Benefits (1)			Benefits
		(in millions)
	Service cost	$	27			$	1			$	33		$	1
	Interest cost	74				18				68			15
	Expected return on plan assets	(90		)		(5		)		(101		)	(5		)
	Amortization of prior service credit	6				2				7			1
	Amortization of net loss	45				3				47			5
	Amortization of transition obligation	—				5				—			5
	Net periodic cost	$	62			$	24			$	54		$	22
	________________
	-1	Net periodic cost in these tables is before considering amounts subject to overhead allocations for capital expenditure projects or for amounts subject to deferral for regulatory purposes.
	CenterPoint Energy's changes in accumulated comprehensive loss related to defined benefit and postretirement plans are as follows:
			Three Months Ended September 30, 2013				Nine Months Ended September 30, 2013
			Pension and Postretirement Plans
			(in millions)
	Beginning Balance		$	(127	)		$	(132	)
	Amounts reclassified from accumulated other comprehensive income:
	Prior service cost (1)		1				2
	Actuarial gains (1)		4				11
	Total reclassifications from accumulated other comprehensive income		5				13
	Tax expense		(2		)		(5		)
	Net current period other comprehensive income		3				8
	Ending Balance		$	(124	)		$	(124	)
	________________
	-1	These accumulated other comprehensive components are included in the computation of net periodic cost.

Derivative_Instruments_Tables

Derivative Instruments (Tables)	9 Months Ended
	Sep. 30, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Fair Value of Derivative Instruments Table	'
	The following tables present information about CenterPoint Energy’s derivative instruments and hedging activities. The first four tables provide a balance sheet overview of CenterPoint Energy’s Derivative Assets and Liabilities as of December 31, 2012 and September 30, 2013, while the last two tables provide a breakdown of the related income statement impacts for the three and nine months ended September 30, 2012 and 2013.
	Fair Value of Derivative Instruments
					December 31, 2012
	Total derivatives not designated		Balance Sheet		Derivative				Derivative
	as hedging instruments		Location		Assets				Liabilities
					Fair Value				Fair Value
					(in millions)
	Natural gas derivatives (1) (2)		Current Assets: Non-trading derivative assets		$	37			$	1
	Natural gas derivatives (1) (2)		Other Assets: Non-trading derivative assets		6				—
	Natural gas derivatives (1) (2)		Current Liabilities: Non-trading derivative liabilities		5				27
	Natural gas derivatives (1) (2)		Other Liabilities: Non-trading derivative liabilities		1				4
	Indexed debt securities derivative		Current Liabilities		—				268
	Total				$	49			$	300
	________________
	-1	The fair value shown for natural gas contracts is comprised of derivative gross volumes totaling 489 billion cubic feet (Bcf) or a net 101 Bcf long position.  Of the net long position, basis swaps constitute 73 Bcf.
	-2	Natural gas contracts are presented on a net basis in the Condensed Consolidated Balance Sheets. Natural gas contracts 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 derivative assets and liabilities was a $26 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 offset by collateral netting of $9 million:
	Offsetting of Natural Gas Derivative Assets and Liabilities
			31-Dec-12
			Gross Amounts Recognized (1)				Gross Amounts Offset in the Consolidated Balance Sheets				Net Amount Presented in the Consolidated Balance Sheets (2)
			(in millions)
	Current Assets: Non-trading derivative assets		$	42			$	(6	)		$	36
	Other Assets: Non-trading derivative assets		7				(1		)		6
	Current Liabilities: Non-trading derivative liabilities		(28		)		14				(14		)
	Other Liabilities: Non-trading derivative liabilities		(4		)		2				(2		)
	Total		$	17			$	9			$	26
	________________
	-1	Gross amounts recognized include some derivative assets and liabilities that are not subject to master netting arrangements.
	-2	The derivative assets and liabilities on the 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.
	Fair Value of Derivative Instruments
					September 30, 2013
	Total derivatives not designated		Balance Sheet		Derivative				Derivative
	as hedging instruments		Location		Assets				Liabilities
					Fair Value				Fair Value
					(in millions)
	Natural gas derivatives (1) (3)		Current Assets: Non-trading derivative assets		$	26			$	—
	Natural gas derivatives (1) (3)		Other Assets: Non-trading derivative assets		10				—
	Natural gas derivatives (1) (2) (3)		Current Liabilities: Non-trading derivative liabilities		8				17
	Natural gas derivatives (1) (3)		Other Liabilities: Non-trading derivative liabilities		—				4
	Indexed debt securities derivative		Current Liabilities		—				382
	Total				$	44			$	403
	________________
	-1	The fair value shown for natural gas contracts is comprised of derivative gross volumes totaling 607 Bcf or a net 24 Bcf long position.  Of the net long position, basis swaps constitute 89 Bcf.
	-2	The $17 million Derivative Current Liability includes $2 million related to physical forwards purchased from Enable.
	-3	Natural gas contracts are presented on a net basis in the Condensed Consolidated Balance Sheets. Natural gas contracts 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 derivative assets and liabilities was a $29 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 offset by collateral netting of $6 million:
	Offsetting of Natural Gas Derivative Assets and Liabilities
			September 30, 2013
			Gross Amounts Recognized (1)				Gross Amounts Offset in the Consolidated Balance Sheets				Net Amount Presented in the Consolidated Balance Sheets (2)
			(in millions)
	Current Assets: Non-trading derivative assets		$	34			$	(8	)		$	26
	Other Assets: Non-trading derivative assets		10				—				10
	Current Liabilities: Non-trading derivative liabilities		(17		)		11				(6		)
	Other Liabilities: Non-trading derivative liabilities		(4		)		3				(1		)
	Total		$	23			$	6			$	29
	________________
	-1	Gross amounts recognized include some derivative assets and liabilities that are not subject to master netting arrangements.
	-2	The derivative assets and liabilities on the 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.
Income Statement Impact of Derivative Activity Table	'
	For CenterPoint Energy’s price stabilization activities of the Natural Gas Distribution business segment, the settled costs of derivatives are ultimately recovered through purchased gas adjustments. Accordingly, the net unrealized gains and losses associated with these contracts are recorded as net regulatory assets. Realized and unrealized gains and losses on other derivatives are recognized in the Condensed Statements of Consolidated Income as revenue for physical natural gas sales derivative contracts and as natural gas expense for financial natural gas derivatives and other physical natural gas derivatives. Unrealized gains and losses on indexed debt securities are recorded as Other Income (Expense) in the Condensed Statements of Consolidated Income.
	Income Statement Impact of Derivative Activity
					Three Months Ended September 30,
	Total derivatives not designated		Income Statement Location		2012				2013
	as hedging instruments
					(in millions)
	Natural gas derivatives		Gains (Losses) in Revenue		$	(21	)		$	11
	Natural gas derivatives (1)		Gains (Losses) in Expense: Natural Gas		24				(2		)
	Indexed debt securities derivative		Gains (Losses) in Other Income (Expense)		(52		)		(42		)
	Total				$	(49	)		$	(33	)
	Income Statement Impact of Derivative Activity
					Nine Months Ended September 30,
	Total derivatives not designated		Income Statement Location		2012				2013
	as hedging instruments
					(in millions)
	Natural gas derivatives		Gains (Losses) in Revenue		$	22			$	24
	Natural gas derivatives (1) (2)		Gains (Losses) in Expense: Natural Gas		(44		)		(3		)
	Indexed debt securities derivative		Gains (Losses) in Other Income (Expense)		(76		)		(120		)
	Total				$	(98	)		$	(99	)
	________________
	-1	The Gains (Losses) in Expense: Natural Gas includes $-0- during the three months ended September 30, 2013 and $(3) million during the nine months ended September 30, 2013 related to physical forwards purchased from Enable.
	-2	The Gains (Losses) in Expense: Natural Gas includes $(38) million and $-0- of costs during the nine months ended September 30, 2012 and 2013, respectively, associated with price stabilization activities of the Natural Gas Distribution business segment that will be ultimately recovered through purchased gas adjustments.

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
Fair value, assets measured on a recurring basis	'
	The following tables present information about CenterPoint Energy’s assets and liabilities (including derivatives that are presented net) measured at fair value on a recurring basis as of December 31, 2012 and September 30, 2013, and indicate the fair value hierarchy of the valuation techniques utilized by CenterPoint Energy to determine such fair value.
		Quoted Prices in			Significant Other			Significant			Netting			Balance
		Active Markets			Observable			Unobservable			Adjustments (1)			as of
		for Identical Assets			Inputs			Inputs						31-Dec-12
		(Level 1)			(Level 2)			(Level 3)
		(in millions)
	Assets
	Corporate equities	$	542		$	—		$	—		$	—		$	542
	Investments, including money	76			—			—			—			76
	market funds
	Natural gas derivatives	1			40			7			(6		)	42
	Total assets	$	619		$	40		$	7		$	(6	)	$	660
	Liabilities
	Indexed debt securities derivative	$	—		$	268		$	—		$	—		$	268
	Natural gas derivatives	5			21			5			(15		)	16
	Total liabilities	$	5		$	289		$	5		$	(15	)	$	284
	________________
	-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 $9 million posted with the same counterparties.
		Quoted Prices in			Significant Other			Significant			Netting			Balance
		Active Markets			Observable			Unobservable			Adjustments (1)			as of
		for Identical Assets			Inputs			Inputs						30-Sep-13
		(Level 1)			(Level 2)			(Level 3)
		(in millions)
	Assets
	Corporate equities	$	691		$	—		$	—		$	—		$	691
	Investments, including money	65			—			—			—			65
	market funds
	Natural gas derivatives	4			33			7			(8		)	36
	Total assets	$	760		$	33		$	7		$	(8	)	$	792
	Liabilities
	Indexed debt securities derivative	$	—		$	382		$	—		$	—		$	382
	Natural gas derivatives (2)	4			15			2			(14		)	7
	Total liabilities	$	4		$	397		$	2		$	(14	)	$	389
	________________
	-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 $6 million posted with the same counterparties.
	-2	The (Level 2) Natural gas derivative liability of $15 million includes $2 million related to physical forwards purchased from Enable.
Assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs	'
	The following table presents additional information about assets or liabilities, including derivatives that are measured at fair value on a recurring basis for which CenterPoint Energy has utilized Level 3 inputs to determine fair value:
		Fair Value Measurements Using Significant
		Unobservable Inputs (Level 3)
		Derivative assets and liabilities, net
		Three Months Ended September 30,						Nine Months Ended September 30,
		2012			2013			2012			2013
		(in millions)
	Beginning balance	$	3		$	4		$	6		$	2
	Total gains (1)	—			2			4			5
	Total settlements (1)	(2		)	(1		)	(8		)	(2		)
	Transfers out of Level 3	—			—			(1		)	—
	Ending balance (2)	$	1		$	5		$	1		$	5
	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	$	(1	)	$	2		$	—		$	4
	________________
	-1	CenterPoint Energy did not have Level 3 unrealized gains (losses) or settlements related to price stabilization activities of the Natural Gas Distribution business segment during either the three or nine months ended September 30, 2012 or 2013.
	-2	CenterPoint Energy did not have significant Level 3 purchases, sales or transfers into Level 3 during either the three or nine months ended September 30, 2012 or 2013.
Estimated fair value of financial instruments, debt instruments	'
	The fair values of cash and cash equivalents, investments in debt and equity securities classified as “trading” and short-term borrowings are estimated to be approximately equivalent to carrying amounts and have been excluded from the table below. The fair values of non-trading derivative assets and liabilities and CenterPoint Energy’s 2.0% Zero-Premium Exchangeable Subordinated Notes due 2029 (ZENS) indexed debt securities derivative are stated at fair value and are excluded from the table below.  The fair value of each debt instrument is determined by multiplying the principal amount of each debt instrument by the market price. These assets and liabilities, which are not measured at fair value in the Condensed Consolidated Balance Sheets but for which the fair value is disclosed, would be classified as Level 1 in the fair value hierarchy.
		December 31, 2012						September 30, 2013
		Carrying			Fair			Carrying			Fair
		Amount			Value			Amount			Value
		(in millions)
	Financial assets:
	Notes receivable - affiliated companies	$	—		$	—		$	363		$	362
	Financial liabilities:
	Long-term debt	$	9,619		$	10,807		$	8,170		$	8,807

Unconsolidated_Affiliates_Tabl

Unconsolidated Affiliates (Tables)	9 Months Ended
	Sep. 30, 2013
Investment in Unconsolidated Affilidates [Abstract]	'
Summary of Investment Holdings, Schedule of Investments [Table Text Block]	'
		31-Dec-12		September 30, 2013
		(in millions)
	Enable	$	—	$	4,326
	SESH	404		199
	Other	1		—
	Total	$	405	$	4,525
Schedule of Equity in Earning of Unconsolidated Affiliates [Table Text Block]	'
		Three Months Ended September 30,				Nine Months Ended September 30,
		2012		2013		2012		2013
		(in millions)
	Enable	$	—	$	77	$	—	$	110
	SESH	8		3		20		12
	Other	—		—		5		—
		$	8	$	80	$	25	$	122
	Summarized income information for Enable from formation on May 1, 2013 through September 30, 2013, based on the Enogex assets recorded at estimated fair value on the Closing Date, is as follows (in millions):
	Operating Revenues	$	1,298
	Gross Margin	545
	Operating Income	207
	Net Income from Controlling Interest	188
	CenterPoint Energy's 58.3% interest	$	110
Schedule of Balance Sheet of Unconsolidated Affiliate [Table Text Block]	'
	Current assets	$	428
	Non-current assets	10,537
	Current liabilities	622
	Non-current liabilities	2,140

Goodwill_Tables

Goodwill (Tables)	9 Months Ended
	Sep. 30, 2013
Goodwill and Intangible Assets Disclosure [Abstract]	'
Schedule of Goodwill [Table Text Block]	'
	Goodwill by reportable business segment as of December 31, 2012 and changes in the carrying amount of goodwill as of September 30, 2013 are as follows (in millions):
		31-Dec-12		Contributed to Enable		September 30, 2013
	Natural Gas Distribution	$	746	$	—	$	746
	Interstate Pipelines	579		579		—
	Competitive Natural Gas Sales and Services	83		—		83
	Field Services	49		49		—
	Other Operations	11		—		11
	Total	$	1,468	$	628	$	840

ShortTerm_Borrowings_and_Longt1

Short-Term Borrowings and Long-term Debt Credit Facilities (Tables)	9 Months Ended
	Sep. 30, 2013
Debt Disclosure [Abstract]	'
Schedule of Line of Credit Facilities [Table Text Block]	'
	Credit Facilities. As of December 31, 2012 and September 30, 2013, CenterPoint Energy, CenterPoint Houston and CERC Corp. had the following revolving credit facilities and utilization of such facilities (in millions):
		December 31, 2012								September 30, 2013
		Size of		Loans		Letters		Commercial		Size of		Loans		Letters		Commercial
		Facility				of Credit		Paper		Facility				of Credit		Paper
	CenterPoint Energy	$	1,200	$	—	$	7	$	—	$	1,200	$	—	$	6	$	—
	CenterPoint Houston	300		—		4		—		300		—		4		—
	CERC Corp.	950		—		—		—		600		—		—		—
	Total	$	2,450	$	—	$	11	$	—	$	2,100	$	—	$	10	$	—

Income_Taxes_Tables

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2013
Income Tax Disclosure [Abstract]	'
Summary of unrecognized tax benefits	'
	The following table summarizes CenterPoint Energy’s unrecognized tax benefits (expenses) at December 31, 2012 and September 30, 2013:
		December 31,			September 30,
		2012			2013
		(in millions)
	Unrecognized tax expenses	$	(23	)	$	—
	Portion of unrecognized tax expenses that, if recognized,	(3		)	—
	would increase the effective income tax rate
	Interest accrued on unrecognized tax expenses	(8		)	—

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]	'
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	'
		Three Months Ended September 30,				Nine Months Ended September 30,
		2012		2013		2012		2013
		(in millions, except share and per share amounts)
	Net income	$	10	$	151	$	283	$	198
	Basic weighted average shares outstanding	427,406,000		428,628,000		427,086,000		428,389,000
	Plus: Incremental shares from assumed conversions:
	Stock options	230,000		97,000		222,000		93,000
	Restricted stock	2,347,000		2,142,000		2,347,000		2,142,000
	Diluted weighted average shares	429,983,000		430,867,000		429,655,000		430,624,000
	Basic earnings per share:
	Net income	$	0.02	$	0.35	$	0.66	$	0.46
	Diluted earnings per share:
	Net income	$	0.02	$	0.35	$	0.66	$	0.46

Reportable_Business_Segments_T

Reportable Business Segments (Tables)	9 Months Ended
	Sep. 30, 2013
Segment Reporting [Abstract]	'
Schedule of Segment Reporting Information, by Segment [Table Text Block]	'
	Financial data for business segments is as follows (in millions):
		For the Three Months Ended September 30, 2012
		Revenues from			Net				Operating
		External			Intersegment				Income (Loss)
		Customers			Revenues
	Electric Transmission & Distribution	$	748	(1)	$	—			$	242
	Natural Gas Distribution	351			4				5
	Competitive Natural Gas Sales and Services	382			7				(259		)
	Interstate Pipelines	92			30				48
	Field Services	129			12				55
	Other Operations	3			—				(3		)
	Eliminations	—			(53		)		—
	Consolidated	$	1,705		$	—			$	88
		For the Three Months Ended September 30, 2013
		Revenues from			Net				Operating
		External			Intersegment				Income (Loss)
		Customers			Revenues
	Electric Transmission & Distribution	$	745	(1)	$	—			$	239
	Natural Gas Distribution	375			6				5
	Competitive Natural Gas Sales and Services	516			4				2
	Midstream Investments	—			—				—			(3)
	Other Operations	4			—				(2		)
	Eliminations	—			(10		)		—
	Consolidated	$	1,640		$	—			$	244
		For the Nine Months Ended September 30, 2012
		Revenues from			Net				Operating				Total Assets
		External			Intersegment				Income (Loss)				as of December
		Customers			Revenues								31, 2012
	Electric Transmission & Distribution	$	1,955	(1)	$	—			$	540			$	11,174
	Natural Gas Distribution	1,560			15				135				4,775
	Competitive Natural Gas Sales and Services	1,204			18				(262		)		839
	Interstate Pipelines	262			112				160				4,004
	Field Services	324			26				153				2,453
	Other Operations	9			—				2				2,600			(4)
	Eliminations	—			(171		)		—				(2,974		)
	Consolidated	$	5,314		$	—			$	728			$	22,871
		For the Nine Months Ended September 30, 2013
		Revenues from			Net				Operating				Total Assets
		External			Intersegment				Income (Loss)				as of September 30, 2013
		Customers			Revenues
	Electric Transmission & Distribution	$	1,933	(1)	$	—			$	488			$	10,364
	Natural Gas Distribution	1,942			19				169				4,776
	Competitive Natural Gas Sales and Services	1,726			19				12				806
	Interstate Pipelines	133		(2)	53			(2)	72			(2)	—
	Field Services	178		(2)	18			(2)	73			(2)	—
	Midstream Investments	—			—				—				4,525			(3)
	Other Operations	10			—				(15		)		2,780			(4)
	Eliminations	—			(109		)		—				(1,676		)
	Consolidated	$	5,922		$	—			$	799			$	21,575
	________________
	-1	Sales to affiliates of NRG in the three months ended September 30, 2012 and 2013 represented approximately $196 million and $202 million, respectively, of CenterPoint Houston’s transmission and distribution revenues.  Sales to affiliates of Energy Future Holdings Corp. in the three months ended September 30, 2012 and 2013 represented approximately $49 million and $52 million, respectively, of CenterPoint Houston’s transmission and distribution revenues. Sales to affiliates of NRG in the nine months ended September 30, 2012 and 2013 represented approximately $488 million and $494 million, respectively, of CenterPoint Houston’s transmission and distribution revenues. Sales to affiliates of Energy Future Holdings Corp. in the nine months ended September 30, 2012 and 2013 represented approximately $123 million and $125 million, respectively, of CenterPoint Houston’s transmission and distribution revenues.
	-2	Results reflected in the nine months ended September 30, 2013 represent only January 2013 through April 2013.
	-3	Midstream Investments reported equity earnings of $77 million from Enable and $3 million of equity earnings from CenterPoint Energy’s retained interest in SESH for the three months ended September 30, 2013. Midstream Investments reported equity earnings of $110 million from Enable and $5 million of equity earnings from CenterPoint Energy’s retained interest in SESH for the five months ended September 30, 2013. Included in total assets of Midstream Investments as of September 30, 2013 is $4,326 million related to CenterPoint Energy’s investment in Enable and $199 million related to CenterPoint Energy’s retained interest in SESH.
	-4	Included in total assets of Other Operations as of December 31, 2012 and September 30, 2013 are pension and other postemployment related regulatory assets of

Background_and_Basis_of_Presen1

Background and Basis of Presentation (Details)	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	31-May-13	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	31-May-13
		CERC Corp [Member]	CERC Corp [Member]	CERC Corp [Member]	ArcLight [Member]	CERC Corp [Member]	CERC Corp [Member]	OGE ARCLIGHT [Member]
		Enable Midstream Partners [Member]	Enable Midstream Partners [Member]	Southeast Supply Header Llc [Member]	Enable Midstream Partners [Member]	Enable Midstream Partners [Member]	Enable Midstream Partners [Member]	Enogex LLC [Member]
Equity Method Investment, Ownership Percentage	'	58.30%	58.30%	'	13.20%	28.50%	28.50%	'
Equity Interest Contributed, Percentage	'	'	'	24.95%	'	'	'	100.00%
Nature of Common Ownership or Management Control Relationships	'	'	50.00%	'	'	'	50.00%	'
Incentive Distribution Right	'	40.00%	'	'	'	60.00%	'	'
Number Of Vies Consolidated In Financial Statements	4	'	'	'	'	'	'	'

Employee_Benefit_Plans_Details

Employee Benefit Plans (Details) (USD $)	3 Months Ended				9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Defined Benefit Plan, Change in Accumulated Comprehensive Loss [Roll Forward]	'		'		'		'
Beginning Balance	'		'		($135)		'
Amounts reclassified from accumulated other comprehensive income:	'		'		'		'
Net current period other comprehensive income	3		3		8		8
Ending Balance	-127		'		-127		'
Pension Plans, Defined Benefit [Member]	'		'		'		'
Defined Benefit Plan Disclosure [Line Items]	'		'		'		'
Service cost	11	[1]	9	[1]	33	[1]	27	[1]
Interest cost	22	[1]	25	[1]	68	[1]	74	[1]
Expected return on plan assets	-33	[1]	-30	[1]	-101	[1]	-90	[1]
Amortization of prior service credit	3	[1]	2	[1]	7	[1]	6	[1]
Amortization of net loss	15	[1]	15	[1]	47	[1]	45	[1]
Amortization of transition obligation	0	[1]	0	[1]	0	[1]	0	[1]
Net periodic cost	18	[1]	21	[1]	54	[1]	62	[1]
Total contributions to the plans during the period	52		'		89		'
Total contributions expected in 2013	92		'		'		'
Other Postretirement Benefit Plans, Defined Benefit [Member]	'		'		'		'
Defined Benefit Plan Disclosure [Line Items]	'		'		'		'
Service cost	0		0		1		1
Interest cost	5		6		15		18
Expected return on plan assets	-1		-1		-5		-5
Amortization of prior service credit	1		0		1		2
Amortization of net loss	2		1		5		3
Amortization of transition obligation	1		2		5		5
Net periodic cost	8		8		22		24
Total contributions to the plans during the period	4		'		12		'
Total contributions expected in 2013	17		'		'		'
Other Pension Plans, Postretirement or Supplemental Plans, Defined Benefit [Member]	'		'		'		'
Defined Benefit Plan, Change in Accumulated Comprehensive Loss [Roll Forward]	'		'		'		'
Beginning Balance	-127		'		-132		'
Amounts reclassified from accumulated other comprehensive income:	'		'		'		'
Prior service cost (1)	1	[2]	'		2	[2]	'
Actuarial gains (1)	4	[2]	'		11	[2]	'
Total reclassifications from accumulated other comprehensive income	5		'		13		'
Tax expense	-2		'		-5		'
Net current period other comprehensive income	3		'		8		'
Ending Balance	($124)		'		($124)		'
[1]	Net periodic cost in these tables is before considering amounts subject to overhead allocations for capital expenditure projects or for amounts subject to deferral for regulatory purposes.
[2]	These accumulated other comprehensive components are included in the computation of net periodic cost.

Regulatory_Accounting_Details

Regulatory Accounting (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Amount of allowed equity return on the true-up balance that has not been recognized	$518	'	$518	'
Amount of allowed equity return on the true-up balance that was recognized in the period	$15	$16	$35	$37

Derivative_Instruments_Details

Derivative Instruments (Details) (USD $)	3 Months Ended				9 Months Ended				12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012
					MMcf				MMcf
					Years
Derivative, Fair Value, Net [Abstract]	'		'		'		'		'
Derivative assets fair value	$44	[1],[2]	'		$44	[1],[2]	'		$49	[3],[4]
Derivative liabilities fair value	-403	[1],[2]	'		-403	[1],[2]	'		-300	[3],[4]
Net Amount Presented in the Consolidated Balance Sheets	29		'		29		'		26
Derivative, fair value, offsets, net	6		'		6		'		9
Derivative Instruments, Liabilities, Physical Forwards Purchased	2		'		2		'		'
Derivative gross volumes on natural gas contracts (MMcf)	'		'		607,000		'		489,000
Net long position (MMcf)	'		'		24,000		'		101,000
Amount of net long position constituted by basis swaps (MMcf)	'		'		89,000		'		73,000
Total fair value of the derivative instruments that contain credit risk contingent features that are in a net liability position	3		'		3		'		5
The aggregate fair value of assets already posted as collateral	1		'		1		'		1
Credit Risk Contingent Features assets	3		'		3		'		5
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net [Abstract]	'		'		'		'		'
Term of normal weather used as the basis for weather hedges (in years)	'		'		10		'		'
Gains (Losses) Recognized Related to Weather Hedges	0		0		-6		6		'
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	-33		-49		-99		-98		'
Natural gas derivatives [Member]	'		'		'		'		'
Derivative, Fair Value, Net [Abstract]	'		'		'		'		'
Gross Amounts Recognized	23	[5]	'		23	[5]	'		17	[5]
Net Amount Presented in the Consolidated Balance Sheets	29	[6]	'		29	[6]	'		26	[6]
Derivative, fair value, offsets, net	6		'		6		'		9
Natural gas derivatives [Member] | Gains (Losses) in Revenue [Member]	'		'		'		'		'
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net [Abstract]	'		'		'		'		'
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	11		-21		24		22		'
Natural gas derivatives [Member] | Gains (Losses) in Expense: Natural Gas [Member]	'		'		'		'		'
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net [Abstract]	'		'		'		'		'
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	-2	[7]	24	[7]	-3	[7],[8]	-44	[7],[8]	'
Derivative Instruments physical purchase	0		'		-3		'		'
Costs associated with price stabilization activities of the Natural Gas Distribution business segment included in Expenses	'		'		0		-38		'
Natural gas derivatives [Member] | Current Assets [Member]	'		'		'		'		'
Derivative, Fair Value, Net [Abstract]	'		'		'		'		'
Derivative assets fair value	34	[5]	'		34	[5]	'		42	[5]
Derivative Asset, Fair Value, Gross Liability	-8		'		-8		'		-6
Net Amount Presented in the Consolidated Balance Sheets	26	[6]	'		26	[6]	'		36	[6]
Natural gas derivatives [Member] | Other Assets [Member]	'		'		'		'		'
Derivative, Fair Value, Net [Abstract]	'		'		'		'		'
Derivative assets fair value	10	[5]	'		10	[5]	'		7	[5]
Derivative Asset, Fair Value, Gross Liability	0		'		0		'		-1
Net Amount Presented in the Consolidated Balance Sheets	10	[6]	'		10	[6]	'		6	[6]
Natural gas derivatives [Member] | Current Liabilities [Member]	'		'		'		'		'
Derivative, Fair Value, Net [Abstract]	'		'		'		'		'
Derivative liabilities fair value	-17	[5]	'		-17	[5]	'		-28	[5]
Derivative Liability, Fair Value, Gross Asset	11		'		11		'		14
Net Amount Presented in the Consolidated Balance Sheets	-6	[6]	'		-6	[6]	'		-14	[6]
Natural gas derivatives [Member] | Other Liabilities [Member]	'		'		'		'		'
Derivative, Fair Value, Net [Abstract]	'		'		'		'		'
Derivative liabilities fair value	-4	[5]	'		-4	[5]	'		-4	[5]
Derivative Liability, Fair Value, Gross Asset	3		'		3		'		2
Net Amount Presented in the Consolidated Balance Sheets	-1	[6]	'		-1	[6]	'		-2	[6]
Indexed Debt Securities Derivative [Member] | Gains (losses) in Other Income (Expense) [Member]	'		'		'		'		'
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net [Abstract]	'		'		'		'		'
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	-42		-52		-120		-76		'
Not Designated as Hedging Instrument [Member] | Natural gas derivatives [Member] | Current Assets [Member]	'		'		'		'		'
Derivative, Fair Value, Net [Abstract]	'		'		'		'		'
Derivative assets fair value	26	[1],[2]	'		26	[1],[2]	'		37	[3],[4]
Derivative liabilities fair value	0	[1],[2]	'		0	[1],[2]	'		-1	[3],[4]
Not Designated as Hedging Instrument [Member] | Natural gas derivatives [Member] | Other Assets [Member]	'		'		'		'		'
Derivative, Fair Value, Net [Abstract]	'		'		'		'		'
Derivative assets fair value	10	[1],[2]	'		10	[1],[2]	'		6	[3],[4]
Derivative liabilities fair value	0	[1],[2]	'		0	[1],[2]	'		0	[3],[4]
Not Designated as Hedging Instrument [Member] | Natural gas derivatives [Member] | Current Liabilities [Member]	'		'		'		'		'
Derivative, Fair Value, Net [Abstract]	'		'		'		'		'
Derivative assets fair value	8	[1],[2],[9]	'		8	[1],[2],[9]	'		5	[3],[4]
Derivative liabilities fair value	-17	[1],[2],[9]	'		-17	[1],[2],[9]	'		-27	[3],[4]
Not Designated as Hedging Instrument [Member] | Natural gas derivatives [Member] | Other Liabilities [Member]	'		'		'		'		'
Derivative, Fair Value, Net [Abstract]	'		'		'		'		'
Derivative assets fair value	0	[1],[2]	'		0	[1],[2]	'		1	[3],[4]
Derivative liabilities fair value	-4	[1],[2]	'		-4	[1],[2]	'		-4	[3],[4]
Not Designated as Hedging Instrument [Member] | Indexed Debt Securities Derivative [Member] | Current Liabilities [Member]	'		'		'		'		'
Derivative, Fair Value, Net [Abstract]	'		'		'		'		'
Derivative assets fair value	0		'		0		'		0
Derivative liabilities fair value	($382)		'		($382)		'		($268)
[1]	Natural gas contracts are presented on a net basis in the Condensed Consolidated Balance Sheets. Natural gas contracts 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 derivative assets and liabilities was a $29 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 offset by collateral netting of $6 million
[2]	The fair value shown for natural gas contracts is comprised of derivative gross volumes totaling 607 Bcf or a net 24 Bcf long position. Of the net long position, basis swaps constitute 89 Bcf.
[3]	Natural gas contracts are presented on a net basis in the Condensed Consolidated Balance Sheets. Natural gas contracts 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 derivative assets and liabilities was a $26 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 offset by collateral netting of $9 million
[4]	The fair value shown for natural gas contracts is comprised of derivative gross volumes totaling 489 billion cubic feet (Bcf) or a net 101 Bcf long position. Of the net long position, basis swaps constitute 73 Bcf.
[5]	Gross amounts recognized include some derivative assets and liabilities that are not subject to master netting arrangements.
[6]	The derivative assets and liabilities on the 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.
[7]	The Gains (Losses) in Expense: Natural Gas includes $(38) million and $-0- of costs during the nine months ended September 30, 2012 and 2013, respectively, associated with price stabilization activities of the Natural Gas Distribution business segment that will be ultimately recovered through purchased gas adjustments.
[8]	The Gains (Losses) in Expense: Natural Gas includes $-0- during the three months ended September 30, 2013 and $(3) million during the nine months ended September 30, 2013 related to physical forwards purchased from Enable.
[9]	The $17 million Derivative Current Liability includes $2 million related to physical forwards purchased from Enable.

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)	3 Months Ended				9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012
Assets	'		'		'		'		'
Corporate equities	$691		'		$691		'		$542
Investments, including money market funds	65		'		65		'		76
Natural gas derivatives, gross assets	44	[1],[2]	'		44	[1],[2]	'		49	[3],[4]
Natural gas derivatives, assets	36		'		36		'		42
Total assets	792		'		792		'		660
Liabilities	'		'		'		'		'
Indexed debt securities derivative	382		'		382		'		268
Natural gas derivatives, gross liability	403	[1],[2]	'		403	[1],[2]	'		300	[3],[4]
Natural gas derivatives, liabilities	7	[5]	'		7	[5]	'		16
Total liabilities	389		'		389		'		284
Cash collateral posted with counterparties	6		'		6		'		9
Derivative Instruments, Liabilities, Physical Forwards Purchased	2		'		2		'		'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'		'		'		'		'
Beginning balance	4		3		2		6		'
Total gains	2	[6]	0	[6]	5	[6]	4	[6]	'
Total settlements	-1	[6]	-2	[6]	-2	[6]	-8	[6]	'
Transfers out of Level 3	0		0		0		-1		'
Ending balance	5	[7]	1	[7]	5	[7]	1	[7]	'
The amount of total gains for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held at the reporting date	2		-1		4		0		'
Carrying Amount [Member]	'		'		'		'		'
Liabilities	'		'		'		'		'
Notes Receivable, Fair Value Disclosure	363		'		363		'		0
Long-term Debt	8,170		'		8,170		'		9,619
Fair Value [Member]	'		'		'		'		'
Liabilities	'		'		'		'		'
Notes Receivable, Fair Value Disclosure	362		'		362		'		0
Long-term Debt	8,807		'		8,807		'		10,807
Fair Value, Inputs, Level 1 [Member]	'		'		'		'		'
Assets	'		'		'		'		'
Corporate equities	691		'		691		'		542
Investments, including money market funds	65		'		65		'		76
Natural gas derivatives, gross assets	4		'		4		'		1
Total assets	760		'		760		'		619
Liabilities	'		'		'		'		'
Indexed debt securities derivative	0		'		0		'		0
Natural gas derivatives, gross liability	4	[5]	'		4	[5]	'		5
Total liabilities	4		'		4		'		5
Fair Value, Inputs, Level 2 [Member]	'		'		'		'		'
Assets	'		'		'		'		'
Corporate equities	0		'		0		'		0
Investments, including money market funds	0		'		0		'		0
Natural gas derivatives, gross assets	33		'		33		'		40
Total assets	33		'		33		'		40
Liabilities	'		'		'		'		'
Indexed debt securities derivative	382		'		382		'		268
Natural gas derivatives, gross liability	15	[5]	'		15	[5]	'		21
Total liabilities	397		'		397		'		289
Fair Value, Inputs, Level 3 [Member]	'		'		'		'		'
Assets	'		'		'		'		'
Corporate equities	0		'		0		'		0
Investments, including money market funds	0		'		0		'		0
Natural gas derivatives, gross assets	7		'		7		'		7
Total assets	7		'		7		'		7
Liabilities	'		'		'		'		'
Indexed debt securities derivative	0		'		0		'		0
Natural gas derivatives, gross liability	2	[5]	'		2	[5]	'		5
Total liabilities	2		'		2		'		5
Netting Adjustments [Member]	'		'		'		'		'
Assets	'		'		'		'		'
Corporate equities	0	[8]	'		0	[8]	'		0	[9]
Investments, including money market funds	0	[8]	'		0	[8]	'		0	[9]
Natural gas derivatives, netting adjustment	-8	[8]	'		-8	[8]	'		-6	[9]
Liabilities	'		'		'		'		'
Indexed debt securities derivative	0	[8]	'		0	[8]	'		0	[9]
Natural gas derivatives, netting adjustment	($14)	[5],[8]	'		($14)	[5],[8]	'		($15)	[9]
Minimum [Member] | Fair Value, Inputs, Level 3 [Member]	'		'		'		'		'
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]	'		'		'		'		'
Option volatilities	0.00%		'		0.00%		'		'
Maximum [Member] | Fair Value, Inputs, Level 3 [Member]	'		'		'		'		'
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]	'		'		'		'		'
Option volatilities	52.00%		'		52.00%		'		'
Forward Contracts [Member] | Minimum [Member] | Fair Value, Inputs, Level 3 [Member]	'		'		'		'		'
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]	'		'		'		'		'
Illiquid forward price per mmbtu	'		'		2.85		'		'
Forward Contracts [Member] | Maximum [Member] | Fair Value, Inputs, Level 3 [Member]	'		'		'		'		'
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]	'		'		'		'		'
Illiquid forward price per mmbtu	'		'		4.48		'		'
[1]	Natural gas contracts are presented on a net basis in the Condensed Consolidated Balance Sheets. Natural gas contracts 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 derivative assets and liabilities was a $29 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 offset by collateral netting of $6 million
[2]	The fair value shown for natural gas contracts is comprised of derivative gross volumes totaling 607 Bcf or a net 24 Bcf long position. Of the net long position, basis swaps constitute 89 Bcf.
[3]	Natural gas contracts are presented on a net basis in the Condensed Consolidated Balance Sheets. Natural gas contracts 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 derivative assets and liabilities was a $26 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 offset by collateral netting of $9 million
[4]	The fair value shown for natural gas contracts is comprised of derivative gross volumes totaling 489 billion cubic feet (Bcf) or a net 101 Bcf long position. Of the net long position, basis swaps constitute 73 Bcf.
[5]	The (Level 2) Natural gas derivative liability of $15 million includes $2 million related to physical forwards purchased from Enable.
[6]	CenterPoint Energy did not have Level 3 unrealized gains (losses) or settlements related to price stabilization activities of the Natural Gas Distribution business segment during either the three or nine months ended September 30, 2012 or 2013.
[7]	CenterPoint Energy did not have significant Level 3 purchases, sales or transfers into Level 3 during either the three or nine months ended September 30, 2012 or 2013.
[8]	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 $6 million posted with the same counterparties.
[9]	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 $9 million posted with the same counterparties.

Unconsolidated_Affiliates_Deta

Unconsolidated Affiliates (Details) (USD $)	3 Months Ended		5 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2012	1-May-13	Dec. 31, 2012
Contributed Assets	'	'	'	'	'	$5,800,000,000	'
Contributed Liabilities	'	'	'	'	'	1,500,000,000	'
Investment in unconsolidated affiliates	4,525,000,000	'	4,525,000,000	4,525,000,000	'	'	405,000,000
Transitional Services Costs to be Reimbursed	42,000,000	'	70,000,000	'	'	'	'
Term Loan of Affiliate	1,050,000,000	'	1,050,000,000	1,050,000,000	'	'	'
Equity in earnings of unconsolidated affiliates, net	80,000,000	8,000,000	122,000,000	122,000,000	25,000,000	'	'
Midstream Partnership [Member]	'	'	'	'	'	'	'
Equity in earnings of unconsolidated affiliates, net	77,000,000	0	110,000,000	'	0	'	'
Operating Revenues	'	'	1,298,000,000	'	'	'	'
Gross Margin	'	'	545,000,000	'	'	'	'
Operating Income	'	'	207,000,000	'	'	'	'
Net Income	'	'	188,000,000	'	'	'	'
CenterPoint Energy's 58.3% interest	'	'	110,000,000	'	'	'	'
Equity Method Investment, Carrying Amount in Net Assets	229,000,000	'	229,000,000	229,000,000	'	'	'
Equity Method Investment Basis Difference To Be Amortized	210,000,000	'	210,000,000	210,000,000	'	'	'
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	439,000,000	'	439,000,000	439,000,000	'	'	'
Proceeds from Equity Method Investment, Dividends or Distributions	'	'	36,000,000	'	'	'	'
SESH [Member]	'	'	'	'	'	'	'
Equity in earnings of unconsolidated affiliates, net	3,000,000	8,000,000	12,000,000	'	20,000,000	'	'
Other Entity [Member]	'	'	'	'	'	'	'
Equity in earnings of unconsolidated affiliates, net	0	0	0	'	5,000,000	'	'
Midstream Partnership [Member]	'	'	'	'	'	'	'
Debt Repayment by Midstream Partnership	1,050,000,000	'	1,050,000,000	1,050,000,000	'	1,050,000,000	'
Indebtedness to CERC	363,000,000	'	363,000,000	363,000,000	'	'	'
Investment in unconsolidated affiliates	4,326,000,000	'	4,326,000,000	4,326,000,000	'	4,300,000,000	0
Guarantor Obligations, Current Amount	1,050,000,000	'	1,050,000,000	1,050,000,000	'	1,050,000,000	'
Assets, Current	428,000,000	'	428,000,000	428,000,000	'	'	'
Liabilities, Current	10,537,000,000	'	10,537,000,000	10,537,000,000	'	'	'
Liabilities, Current	622,000,000	'	622,000,000	622,000,000	'	'	'
Liabilities, Noncurrent	2,140,000,000	'	2,140,000,000	2,140,000,000	'	'	'
CERC Corp [Member]	'	'	'	'	'	'	'
Guarantor Obligations, Current Amount	1,000,000	'	1,000,000	1,000,000	'	'	'
CERC Corp [Member] | Enable Midstream Partners [Member]	'	'	'	'	'	'	'
Equity Method Investment, Ownership Percentage	58.30%	'	58.30%	58.30%	'	'	'
CERC Corp [Member] | Senior Subordinated Notes [Member]	'	'	'	'	'	'	'
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum	2.10%	'	'	'	'	'	'
Debt Instrument, Interest Rate, Stated Percentage	2.45%	'	'	'	'	'	'
SESH [Member]	'	'	'	'	'	'	'
Investment in unconsolidated affiliates	199,000,000	'	199,000,000	199,000,000	'	'	404,000,000
Equity Method Investment, Ownership Percentage	25.05%	'	25.05%	25.05%	'	'	'
Other Entity [Member]	'	'	'	'	'	'	'
Investment in unconsolidated affiliates	$0	'	$0	$0	'	'	$1,000,000

Goodwill_Details

Goodwill (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013
Goodwill [Roll Forward]	'
Balance at December 31, 2012	$1,468
Contributed to Midstream Partnership	628
Balance at September30, 2013	840
Natural Gas Distribution [Member]	'
Goodwill [Roll Forward]	'
Balance at December 31, 2012	746
Contributed to Midstream Partnership	0
Balance at September30, 2013	746
Interstate Pipelines [Member]	'
Goodwill [Roll Forward]	'
Balance at December 31, 2012	579
Contributed to Midstream Partnership	579
Balance at September30, 2013	0
Competitive Natural Gas Sales and Services [Member]	'
Goodwill [Roll Forward]	'
Balance at December 31, 2012	83
Contributed to Midstream Partnership	0
Balance at September30, 2013	83
Field Services [Member]	'
Goodwill [Roll Forward]	'
Balance at December 31, 2012	49
Contributed to Midstream Partnership	49
Balance at September30, 2013	0
Corporate and Other [Member]	'
Goodwill [Roll Forward]	'
Balance at December 31, 2012	11
Contributed to Midstream Partnership	0
Balance at September30, 2013	$11

Capital_Stock_Details

Capital Stock (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Class of Stock Disclosures [Abstract]	'	'
Capital stock shares authorized (in shares)	1,020,000,000	'
Common stock shares authorized (in shares)	1,000,000,000	'
Common stock shares par value (in dollars per share)	$0.01	'
Cumulative preferred stock shares authorized (in shares)	20,000,000	'
Cumulative preferred stock par value (in dollars per share)	$0.01	'
Total common stock issued (in shares)	428,640,333	427,599,730
Total common stock outstanding (in shares)	428,640,167	427,599,564
Treasury stock (in shares)	166	166

ShortTerm_Borrowings_and_Longt2

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

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

1-May-13

Jun. 30, 2013

Apr. 30, 2013

Jun. 30, 2013

Jun. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Midstream Partnership [Member]

Midstream Partnership [Member]

Senior Notes [Member]

Senior Notes [Member]

Commercial Paper [Member]

Bonds General Mortgage Due January 2014 [Member]

Bank loans due 2016 [Member]

Bank loans due 2016 [Member]

Bank loans due 2016 [Member]

Bank loans due 2016 [Member]

Bank loans due 2016 [Member]

Bank loans due 2016 [Member]

August 1st, 2013 [Member]

August 1st, 2013 [Member]

October 15th, 2013 [Member]

October 15th, 2013 [Member]

Product Financing Arrangement [Member]

Product Financing Arrangement [Member]

CERC Corp [Member]

CERC Corp [Member]

CERC Corp [Member]

CERC Corp [Member]

CenterPoint Houston [Member]

CenterPoint Houston [Member]

CenterPoint Energy [Member]

CenterPoint Energy [Member]

CERC Corp [Member]

CERC Corp [Member]

Bonds Pollution Control Due2015 Member

Bonds Pollution Control Due2015 Member

Bonds Pollution Control Due2015 Member

Bonds Pollution Control Due2015 Member

CenterPoint Energy [Member]

CenterPoint Energy [Member]

CenterPoint Energy [Member]

CenterPoint Energy [Member]

Debt Instrument [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt Instrument, Interest Rate, Stated Percentage

'

'

'

'

'

7.88%

'

5.95%

'

'

'

'

'

'

4.00%

4.00%

4.00%

4.00%

'

'

Extinguishment Of Debt Purchase Price Percentage Of Principal

'

'

'

'

103.42%

'

'

'

'

'

'

'

'

'

'

101.00%

'

101.00%

'

'

Debt Repayment by Midstream Partnership

'

'

$1,050,000,000

$1,050,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Extinguishment of Debt, Amount

'

'

'

'

365,000,000

'

357,000,000

160,000,000

'

'

'

'

'

'

92,000,000

'

59,000,000

'

'

'

Total short term borrowings

70,000,000

38,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

70,000,000

38,000,000

Long-term Debt [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total credit facility amount

2,100,000,000

2,450,000,000

'

'

'

'

'

'

300,000,000

300,000,000

1,200,000,000

1,200,000,000

600,000,000

950,000,000

'

'

'

'

'

'

Loans Outstanding

0

0

'

'

'

'

'

'

0

0

0

0

0

0

'

'

'

'

'

'

Letters of Credit outstanding

10,000,000

11,000,000

'

'

'

'

'

'

4,000,000

4,000,000

6,000,000

7,000,000

0

0

'

'

'

'

'

'

Commercial Paper Outstanding

0

0

'

'

'

'

'

'

0

0

0

0

0

0

'

'

'

'

'

'

Revolving credit facility borrowing rate

'

'

'

'

'

'

'

'

'LIBOR plus 125

'

'London Interbank Offered Rate (LIBOR) plus 150

'

'LIBOR plus 150

'

'

'

'

'

'

'

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

'

'

'

'

'

'

'

'

65.00%

'

65.00%

'

65.00%

'

'

'

'

'

'

'

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

'

'

'

'

'

'

'

'

'

'

70.00%

'

'

'

'

'

'

'

'

'

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)

'

'

'

'

'

'

'

'

'

'

12

'

'

'

'

'

'

'

'

'

Income_Taxes_Details

Income Taxes (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Effective tax rate (in hundredths)	34.00%	92.00%	67.00%	48.00%	'
Tax Adjustments, Settlements, and Unusual Provisions	$8	'	'	'	'
Deferred Taxes, Business Combination, Valuation Allowance, Available to Reduce Goodwill	225	'	225	'	'
Unrecognized tax expenses	0	'	0	'	-23
Unrecognized Tax Expense that Would Impact Effective Tax Rae if Recognized	0	'	0	'	-3
Interest accrued on unrecognized tax expenses	0	'	0	'	-8
Period of time for possible impact of unrecognized tax expenses (in months)	'	'	'12	'	'
Deferred income taxes	'	'	-356	-237	'
Enable Midstream Partners [Member]	'	'	'	'	'
Deferred income taxes	$29	'	'	'	'

Commitments_and_Contingencies_

Commitments and Contingencies (Details) (USD $)	9 Months Ended					9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	1-May-13	Sep. 30, 2013	Sep. 30, 2013
		CenterPoint Energy [Member]	CERC Corp [Member]	Midstream Partnership [Member]	Midstream Partnership [Member]	Minimum [Member]	Maximum [Member]
Recorded Unconditional Purchase Obligation	'	'	'	'	'	'	'
Remainder of 2013	$143,000,000	'	'	'	'	'	'
2014	449,000,000	'	'	'	'	'	'
2015	382,000,000	'	'	'	'	'	'
2016	309,000,000	'	'	'	'	'	'
2017	250,000,000	'	'	'	'	'	'
After 2017	366,000,000	'	'	'	'	'	'
Legal Environmental And Other Regulatory Matters	'	'	'	'	'	'	'
Recovery of compensatory damages sought by plaintiffs	'in excess of $1 billion	'	'	'	'	'	'
Approximate number of gas market manipulation lawsuits naming CenterPoint and/or Reliant Energy (in number of lawsuits)	30	'	'	'	'	'	'
Number of gas market manipulation lawsuits pending for CenterPoint and its affiliates (in number of lawsuits)	1	'	'	'	'	'	'
Number of sites where remediation is complete, other than ongoing operations (in number of sites)	2	'	'	'	'	'	'
Number of remaining sites in the Minnesota service territory (in number of sites)	5	'	'	'	'	'	'
Number of the remaining sites in the Minnesota service territory where the company believes it has no liability (in number of sites)	2	'	'	'	'	'	'
Amount accrued for remediation of Minnesota sites (in number of sites)	13,000,000	'	'	'	'	'	'
Maximum estimated remediation costs for the Minnesota sites	'	'	'	'	'	6,000,000	41,000,000
Years of remediation for the Minnesota sites (in years)	'	'	'	'	'	'30	'50
Annual amount included in rates to fund normal on-going remediation costs	285,000	'	'	'	'	'	'
Amount collected from insurance companies to be used for future environmental remediation	6,100,000	'	'	'	'	'	'
Approximate amount of undiscounted maximum obligation under guarantee	62,000,000	'	53,200,000	'	'	'	'
Guarantee Obligations Maximum Amount Upon Completion Of Gathering Systems	'	100,000,000	'	'	'	'	'
Guarantor Obligations, Current Amount	'	'	$1,000,000	$1,050,000,000	$1,050,000,000	'	'

Earnings_Per_Share_Details

Earnings Per Share (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Net income	$151	$10	$198	$283
Basic weighted average shares outstanding	428,628,000	427,406,000	428,389,000	427,086,000
Plus: Incremental shares from assumed conversions:	'	'	'	'
Stock Options	97,000	230,000	93,000	222,000
Restricted Stock	2,142,000	2,347,000	2,142,000	2,347,000
Diluted weighted average shares	430,867,000	429,983,000	430,624,000	429,655,000
Basic Earnings Per Share:	'	'	'	'
Net income	$0.35	$0.02	$0.46	$0.66
Diluted earnings per share:	'	'	'	'
Net income	$0.35	$0.02	$0.46	$0.66

Reportable_Business_Segments_D

Reportable Business Segments (Details) (USD $)

3 Months Ended

5 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

5 Months Ended

3 Months Ended

5 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

In Millions, unless otherwise specified

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Sep. 30, 2013

1-May-13

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Midstream Partnership [Member]

Midstream Partnership [Member]

Midstream Partnership [Member]

SESH [Member]

SESH [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Consolidation, Eliminations [Member]

Consolidation, Eliminations [Member]

Electric Transmission and Distribution [Member]

Electric Transmission and Distribution [Member]

Electric Transmission and Distribution [Member]

Electric Transmission and Distribution [Member]

Electric Transmission and Distribution [Member]

Electric Transmission and Distribution [Member]

Electric Transmission and Distribution [Member]

Electric Transmission and Distribution [Member]

Electric Transmission and Distribution [Member]

Electric Transmission and Distribution [Member]

Electric Transmission and Distribution [Member]

Electric Transmission and Distribution [Member]

Electric Transmission and Distribution [Member]

Electric Transmission and Distribution [Member]

Electric Transmission and Distribution [Member]

Electric Transmission and Distribution [Member]

Electric Transmission and Distribution [Member]

Electric Transmission and Distribution [Member]

Natural Gas Distribution [Member]

Natural Gas Distribution [Member]

Natural Gas Distribution [Member]

Natural Gas Distribution [Member]

Natural Gas Distribution [Member]

Natural Gas Distribution [Member]

Natural Gas Distribution [Member]

Natural Gas Distribution [Member]

Natural Gas Distribution [Member]

Natural Gas Distribution [Member]

Competitive Natural Gas Sales and Services [Member]

Competitive Natural Gas Sales and Services [Member]

Competitive Natural Gas Sales and Services [Member]

Competitive Natural Gas Sales and Services [Member]

Competitive Natural Gas Sales and Services [Member]

Competitive Natural Gas Sales and Services [Member]

Competitive Natural Gas Sales and Services [Member]

Competitive Natural Gas Sales and Services [Member]

Competitive Natural Gas Sales and Services [Member]

Competitive Natural Gas Sales and Services [Member]

Interstate Pipelines [Member]

Interstate Pipelines [Member]

Interstate Pipelines [Member]

Interstate Pipelines [Member]

Interstate Pipelines [Member]

Interstate Pipelines [Member]

Interstate Pipelines [Member]

Interstate Pipelines [Member]

Field Services [Member]

Field Services [Member]

Field Services [Member]

Field Services [Member]

Field Services [Member]

Field Services [Member]

Field Services [Member]

Field Services [Member]

Midstream Investments [Member]

Midstream Investments [Member]

Midstream Investments [Member]

Midstream Investments [Member]

Midstream Investments [Member]

Midstream Investments [Member]

Midstream Investments [Member]

Midstream Investments [Member]

Midstream Investments [Member]

Midstream Investments [Member]

Other Operations [Member]

Other Operations [Member]

Other Operations [Member]

Other Operations [Member]

Other Operations [Member]

Other Operations [Member]

Other Operations [Member]

Other Operations [Member]

Other Operations [Member]

Other Operations [Member]

Other Operations [Member]

Affiliates of NRG Energy, Inc. [Member]

Affiliates of NRG Energy, Inc. [Member]

Affiliates of NRG Energy, Inc. [Member]

Affiliates of NRG Energy, Inc. [Member]

Affiliates of Energy Future Holdings Corp. [Member]

Affiliates of Energy Future Holdings Corp. [Member]

Affiliates of Energy Future Holdings Corp. [Member]

Affiliates of Energy Future Holdings Corp. [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Operating Segments [Member]

Operating Segments [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Operating Segments [Member]

Operating Segments [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Operating Segments [Member]

Operating Segments [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Operating Segments [Member]

Operating Segments [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Operating Segments [Member]

Operating Segments [Member]

Midstream Partnership [Member]

Midstream Partnership [Member]

CERC Remaining Interest in SESH [Member]

CERC Remaining Interest in SESH [Member]

SESH [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Operating Segments [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Operating Segments [Member]

Operating Segments [Member]

Segment Reporting Information [Line Items]

'

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Revenues

$1,640

$1,705

'

$5,922

$5,314

'

'

'

'

'

'

($10)

($53)

($109)

($171)

'

'

$745

[1]

$748

[1]

$1,933

[1]

$1,955

[1]

$202

$196

$494

$488

$52

$49

$125

$123

$0

$0

$0

$0

'

'

$375

$351

$1,942

$1,560

($6)

($4)

($19)

($15)

'

'

$516

$382

$1,726

$1,204

($4)

($7)

($19)

($18)

'

'

$92

$133

[2]

$262

($30)

($53)

[2]

($112)

'

'

$129

$178

[2]

$324

($12)

($18)

[2]

($26)

'

'

$0

$0

'

'

'

'

'

$0

$0

'

$4

$3

$10

$9

'

$0

$0

$0

$0

'

'

Operating Income (Loss)

244

88

'

799

728

'

'

'

'

'

'

'

'

'

'

'

'

239

242

488

540

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5

5

169

135

'

'

'

'

'

'

2

-259

12

-262

'

'

'

'

'

'

48

72

[2]

160

'

'

'

'

'

55

73

[2]

153

'

'

'

'

'

0

[3]

0

'

'

'

'

'

'

'

'

-2

-3

-15

2

'

'

'

'

'

'

'

Assets

21,575

'

21,575

21,575

'

22,871

'

'

'

'

'

'

'

'

'

-1,676

-2,974

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

10,364

11,174

'

'

'

'

'

'

'

'

4,776

4,775

'

'

'

'

'

'

'

'

806

839

'

'

'

'

'

'

0

4,004

'

'

'

'

'

'

0

2,453

'

'

'

'

'

'

'

'

'

4,525

[3]

'

'

'

'

'

'

'

'

'

2,780

[4]

2,600

[3]

Segment Reporting Pension Plan Assets

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'

'

'

787

'

787

'

832

'

'

'

'

'

'

Equity in earnings of unconsolidated affiliates, net

80

8

122

122

25

'

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'

77

110

3

5

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Investment in unconsolidated affiliates

$4,525

'

$4,525

$4,525

'

$405

$4,326

$4,300

$0

$199

$404

'

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'

$4,326

$4,326

'

'

$199

'

'

'

'

'

'

'

'

'

'

'

'

'

'

[1]

Sales to affiliates of NRG in the three months ended September 30, 2012 and 2013 represented approximately $196 million and $202 million, respectively, of CenterPoint Houston’s transmission and distribution revenues. Sales to affiliates of Energy Future Holdings Corp. in the three months ended September 30, 2012 and 2013 represented approximately $49 million and $52 million, respectively, of CenterPoint Houston’s transmission and distribution revenues. Sales to affiliates of NRG in the nine months ended September 30, 2012 and 2013 represented approximately $488 million and $494 million, respectively, of CenterPoint Houston’s transmission and distribution revenues. Sales to affiliates of Energy Future Holdings Corp. in the nine months ended September 30, 2012 and 2013 represented approximately $123 million and $125 million, respectively, of CenterPoint Houston’s transmission and distribution revenues.

[2]

Results reflected in the nine months ended September 30, 2013 represent only January 2013 through April 2013.

[3]

Midstream Investments reported equity earnings of $77 million from Enable and $3 million of equity earnings from CenterPoint Energy’s retained interest in SESH for the three months ended September 30, 2013. Midstream Investments reported equity earnings of $110 million from Enable and $5 million of equity earnings from CenterPoint Energy’s retained interest in SESH for the five months ended September 30, 2013. Included in total assets of Midstream Investments as of September 30, 2013 is $4,326 million related to CenterPoint Energy’s investment in Enable and $199 million related to CenterPoint Energy’s retained interest in SESH.

[4]

Included in total assets of Other Operations as of December 31, 2012 and September 30, 2013 are pension and other postemployment related regulatory assets of $832 million and $787 million, respectively.

Subsequent_Events_Details

Subsequent Events (Details) (Dividend Declared [Member], USD $)	9 Months Ended
	Sep. 30, 2013	Oct. 23, 2013
Dividend Declared [Member]	'	'
Subsequent Event [Line Items]	'	'
Dividends Payable, Date Declared	23-Oct-13	'
Dividends Payable, Amount Per Share	'	$0.21
Dividends Payable, Date to be Paid, Day, Month and Year	10-Dec-13	'
Dividends Payable, Date of Record, Day, Month and Year	15-Nov-13	'