CenterPoint Energy (CNP) 10-K 28 Feb 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2016	Feb. 10, 2017	Jun. 30, 2016
Document and Entity Information [Abstract]
Entity Registrant Name	CENTERPOINT ENERGY INC
Entity Central Index Key	1,130,310
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		430,688,867
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 10,273,144,728

STATEMENTS OF CONSOLIDATED INCO

STATEMENTS OF CONSOLIDATED INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statements of Consolidated Income
Utility revenues	$ 5,440	$ 5,448	$ 6,116
Non-utility revenues	2,088	1,938	3,110
Total	7,528	7,386	9,226
Expenses:
Utility natural gas	983	1,264	1,878
Non-utility natural gas	1,983	1,838	3,043
Operation and maintenance	2,093	2,007	1,969
Depreciation and amortization	1,126	970	1,013
Taxes other than income taxes	384	374	388
Total	6,569	6,453	8,291
Operating Income	959	933	935
Other Income (Expense):
Gain (loss) on marketable securities	326	(93)	163
Gain (loss) on indexed debt securities	(413)	74	(86)
Interest and other finance charges	(338)	(352)	(353)
Interest on Securitization Bonds	(91)	(105)	(118)
Equity in earnings (losses) of unconsolidated affiliates	208	(1,633)	308
Other, net	35	46	36
Total	(273)	(2,063)	(50)
Income (Loss) Before Income Taxes	686	(1,130)	885
Income tax expense (benefit)	254	(438)	274
Net Income (Loss)	$ 432	$ (692)	$ 611
Basic Earnings Per Share:
Basic Earnings (Loss) Per Share	$ 1	$ (1.61)	$ 1.42
Diluted Earnings Per Share:
Diluted Earnings (Loss) Per Share	$ 1	$ (1.61)	$ 1.42
Weighted Average Shares Outstanding, Basic	430,606,000	430,180,000	429,634,000
Weighted Average Shares Outstanding, Diluted	433,603,000	430,180,000	431,668,000

STATEMENTS OF CONSOLIDATED COMP

STATEMENTS OF CONSOLIDATED COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statements of Consolidated Comprehensive Income
Net income (loss)	$ 432	$ (692)	$ 611
Other comprehensive income (loss):
Adjustment to pension and other postretirement plans (net of tax of $4, $12 and $5, respectively)	(7)	20	3
Net deferred gain from cash flow hedges (net of tax of $-0-, $-0-, and $-0-, respectively)	1	0	0
Reclassification of deferred loss from cash flow hedges realized in net income (net of tax of $1, $-0-, and $-0-, respectively)	1	0	1
Other comprehensive income (loss)	(5)	20	4
Comprehensive income (loss)	$ 427	$ (672)	$ 615

STATEMENTS OF CONSOLIDATED COM4

STATEMENTS OF CONSOLIDATED COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Tax benefit (expense) on adjustment related to pension and postretirement plans	$ 4	$ (12)	$ (5)
Tax expense (benefit) on net deferred gain (loss) from cash flow hedges	0	0	0
Tax expense (benefit) on deferred loss from cash flow hedges realized in net income	$ (1)	$ 0	$ 0

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Current Assets:
Cash and cash equivalents ($340 and $264 related to VIEs, respectively)		$ 341	$ 264
Investment in marketable securities		953	805
Accounts receivable ($52 and $64 related to VIEs, respectively), less bad debt reserve of $15 and $20, respectively		740	593
Accrued unbilled revenues		335	279
Natural gas inventory		131	168
Materials and supplies		181	179
Non-trading derivative assets		51	89
Taxes receivable		30	172
Prepaid expense and other current assets ($40 and $35 related to VIEs, respectively)		161	140
Total current assets		2,923	2,689
Property, Plant and Equipment, net		12,307	11,537
Other Assets:
Goodwill		862	840
Regulatory assets ($1,919 and $2,373 related to VIEs, respectively)		2,677	3,129
Notes receivable - affiliated companies		0	363
Non-trading derivative assets		19	36
Investment in unconsolidated affiliates		2,505	2,594
Preferred units - unconsolidated affiliate		363	0
Other		173	102
Total other assets		6,599	7,064
Total Assets	[1]	21,829	21,290
Current Liabilities:
Short-term borrowings	[2]	35	40
Current portion of VIE Securitization Bonds long-term debt		411	391
Indexed debt		114	145
Current portion of other long-term debt		500	328
Indexed debt securities derivative		717	442
Accounts payable		657	483
Taxes accrued		172	158
Interest accrued		108	117
Non-trading derivative liabilities		41	11
Other		325	343
Total current liabilities		3,080	2,458
Other Liabilities:
Deferred income taxes, net		5,263	5,047
Non-trading derivative liabilities		5	5
Benefit obligations		913	904
Regulatory liabilities		1,298	1,276
Other		278	273
Total other liabilities		7,757	7,505
Long-term Debt:
VIE Securitization Bonds, net		1,867	2,276
Other long-term debt, net		5,665	5,590
Total long-term debt, net		7,532	7,866	[3]
Commitments and Contingencies (Note 15)
Shareholders’ Equity:
Cumulative preferred stock, $0.01 par value, 20,000,000 shares authorized, none issued or outstanding		0	0
Common stock, $0.01 par value, 1,000,000,000 shares authorized, 430,682,504 shares and 430,262,703 shares outstanding, respectively		4	4
Additional paid-in capital		4,195	4,180
Accumulated deficit		(668)	(657)
Accumulated other comprehensive loss		(71)	(66)
Total shareholders’ equity		3,460	3,461
Total Liabilities and Shareholders’ Equity		$ 21,829	$ 21,290
[1]	Amounts for 2015 and 2014 have been restated to reflect the adoption of ASU 2015-03.
[2]	Includes amounts due or exchangeable within one year of the date noted.
[3]	Includes $35 million of unamortized debt issuance costs to reflect adoption of ASU 2015-03.

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Current Assets:
Cash and cash equivalents ($340 and $264 related to VIEs, respectively)	$ 341	$ 264
Allowance for Doubtful Accounts Receivable, Current	15	20
Accounts receivable ($52 and $64 related to VIEs, respectively), less bad debt reserve of $15 and $20, respectively	740	593
Prepaid expense and other current assets ($40 and $35 related to VIEs, respectively)	161	140
Other Assets:
Regulatory assets ($1,919 and $2,373 related to VIEs, respectively)	$ 2,677	$ 3,129
Shareholders’ Equity:
Cumulative preferred stock par value (in dollars per share)	$ 0.01	$ 0.01
Cumulative preferred stock authorized (in shares)	20,000,000	20,000,000
Cumulative preferred stock outstanding (in shares)	0	0
Common stock par value (in dollars per share)	$ 0.01	$ 0.01
Common stock authorized (in shares)	1,000,000,000	1,000,000,000
Common stock outstanding (in shares)	430,682,504	430,262,703
Variable Interest Entity, Primary Beneficiary [Member]
Current Assets:
Cash and cash equivalents ($340 and $264 related to VIEs, respectively)	$ 340	$ 264
Accounts receivable ($52 and $64 related to VIEs, respectively), less bad debt reserve of $15 and $20, respectively	52	64
Prepaid expense and other current assets ($40 and $35 related to VIEs, respectively)	40	35
Other Assets:
Regulatory assets ($1,919 and $2,373 related to VIEs, respectively)	$ 1,919	$ 2,373

STATEMENTS OF CONSOLIDATED CASH

STATEMENTS OF CONSOLIDATED CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash Flows from Operating Activities:
Net income (loss)	$ 432	$ (692)	$ 611
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	1,126	970	1,013
Amortization of deferred financing costs	26	27	28
Deferred income taxes	213	(413)	280
Unrealized loss (gain) on marketable securities	(326)	93	(163)
Loss (gain) on indexed debt securities	413	(74)	86
Write-down of natural gas inventory	1	4	8
Equity in (earnings) losses of unconsolidated affiliates, net of distributions	(208)	1,779	(2)
Pension contributions	(9)	(66)	(97)
Changes in other assets and liabilities, excluding acquisitions:
Accounts receivable and unbilled revenues, net	(117)	345	39
Inventory	34	28	(102)
Taxes receivable	142	18	(190)
Accounts payable	133	(224)	(3)
Fuel cost recovery	(72)	43	(41)
Non-trading derivatives, net	30	(7)	(34)
Margin deposits, net	101	(4)	(79)
Interest and taxes accrued	5	(10)	(23)
Net regulatory assets and liabilities	(60)	63	22
Other current assets	(17)	10	1
Other current liabilities	22	(50)	(20)
Other assets	(16)	(5)	9
Other liabilities	30	8	41
Other, net	45	22	13
Net cash provided by operating activities	1,928	1,865	1,397
Cash Flows from Investing Activities:
Capital expenditures	(1,414)	(1,584)	(1,372)
Acquisitions, net of cash acquired	(102)	0	0
Decrease in notes receivable - unconsolidated affiliate	363	0	0
Investment in preferred units - unconsolidated affiliate	(363)	0	0
Distributions from unconsolidated affiliates in excess of cumulative earnings	297	148	0
Decrease (increase) in restricted cash of Bond companies	(5)	12	(7)
Investment in unconsolidated affiliates	0	0	(1)
Proceeds from sale of marketable securities	178	32	0
Other, net	0	5	(4)
Net cash used in investing activities	(1,046)	(1,387)	(1,384)
Cash Flows from Financing Activities:
Increase (decrease) in short-term borrowings, net	(5)	(13)	10
Proceeds from commercial paper, net	469	403	414
Proceeds from long-term debt	600	200	600
Payments of long-term debt	(1,218)	(644)	(537)
Loss on reacquired debt	(22)	0	0
Debt issuance costs	(9)	0	(8)
Payment of dividends on common stock	(443)	(426)	(408)
Distribution to ZENS holders	(178)	(32)	0
Other, net	1	0	6
Net cash provided by (used in) financing activities	(805)	(512)	77
Net Increase (Decrease) in Cash and Cash Equivalents	77	(34)	90
Cash and Cash Equivalents at Beginning of Year	264	298	208
Cash and Cash Equivalents at End of Year	341	264	298
Cash Payments:
Interest, net of capitalized interest	406	426	434
Income taxes (refunds), net	(104)	(45)	192
Non-cash transactions:
Accounts payable related to capital expenditures	87	95	104
Exercise of SESH put to Enable	$ 0	$ 1	$ 196

STATEMENTS OF CONSOLIDATED SHAR

STATEMENTS OF CONSOLIDATED SHAREHOLDERS' EQUITY - USD ($) shares in Millions, $ in Millions	Total	Preference Stock [Member]	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Adjustment to pension and postretirement plans [Member]	Net deferred loss from cash flow hedges [Member]	Total accumulated other comprehensive loss, end of year [Member]
Shares, Outstanding at Dec. 31, 2013				429
Balance at Dec. 31, 2013				$ 4	$ 4,157	$ 258
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance related to benefit and investment plans				$ 0	12
Issuance related to benefit and investment plans (in shares)				1
Net income (loss)	$ 611					611
Common stock dividends						(408)
Balance at Dec. 31, 2014	4,548	$ 0	$ 0	$ 4	4,169	461	$ (85)	$ (1)	$ (86)
Shares, Outstanding at Dec. 31, 2014		0	0	430
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance related to benefit and investment plans				$ 0	11
Issuance related to benefit and investment plans (in shares)				0
Net income (loss)	(692)					(692)
Common stock dividends						(426)
Balance at Dec. 31, 2015	3,461	$ 0	$ 0	$ 4	4,180	(657)	(65)	(1)	(66)
Shares, Outstanding at Dec. 31, 2015		0	0	430
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance related to benefit and investment plans				$ 0	15
Issuance related to benefit and investment plans (in shares)				1
Net income (loss)	432					432
Common stock dividends						(443)
Balance at Dec. 31, 2016	$ 3,460	$ 0	$ 0	$ 4	$ 4,195	$ (668)	$ (72)	$ 1	$ (71)
Shares, Outstanding at Dec. 31, 2016		0	0	431

STATEMENTS OF CONSOLIDATED SHA9

STATEMENTS OF CONSOLIDATED SHAREHOLDERS' EQUITY (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Stockholders' Equity [Abstract]
Preferred Stock, Shares Outstanding	0	0	0
Cumulative preferred stock par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Cumulative preferred stock shares authorized (in shares)	20,000,000	20,000,000	20,000,000
Common stock shares par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Common stock shares authorized (in shares)	1,000,000,000	1,000,000,000	1,000,000,000

Background

Background	12 Months Ended
	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Background [Text Block]	Background CenterPoint Energy, Inc. is a public utility holding company. CenterPoint Energy’s operating subsidiaries own and operate electric transmission and distribution and natural gas distribution facilities, supply natural gas to commercial and industrial customers and electric and natural gas utilities and own interests in Enable as described below. CenterPoint Energy’s indirect, wholly-owned subsidiaries include: • Houston Electric, which engages in the electric transmission and distribution business in the Texas Gulf Coast area that includes the city of Houston; • CERC Corp., which owns and operates natural gas distribution systems in six states; and • CES, which obtains and offers competitive variable and fixed-price physical natural gas supplies and services primarily to commercial and industrial customers and electric and natural gas utilities in 31 states. As of December 31, 2016 , CenterPoint Energy also owned an aggregate of 14,520,000 Series A Preferred Units in Enable, which owns, operates and develops natural gas and crude oil infrastructure assets, and CERC Corp. owned approximately 54.1% of the limited partner interests in Enable. For a description of CenterPoint Energy’s reportable business segments, see Note 18 .

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Summary of Significant Accounting Policies [Text Block]	Summary of Significant Accounting Policies (a) Use of Estimates The preparation of financial statements in conformity with generally accepted accounting principles 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. (b) Principles of Consolidation The accounts of CenterPoint Energy and its wholly-owned and majority owned subsidiaries are included in the consolidated financial statements. All intercompany transactions and balances are eliminated in consolidation. CenterPoint Energy generally uses the equity method of accounting for investments in entities in which CenterPoint Energy has an ownership interest between 20% and 50% and exercises significant influence. CenterPoint Energy also uses the equity method for investments in which it has ownership percentages greater than 50%, when it exercises significant influence, does not have control and is not considered the primary beneficiary, if applicable. In 2013, CenterPoint Energy, OGE and affiliates of ArcLight, formed Enable as a private limited partnership. CenterPoint Energy has the ability to significantly influence the operating and financial policies of, but not solely control, Enable and, accordingly, recorded an equity method investment, at the historical costs of net assets contributed. Under the equity method, CenterPoint Energy adjusts its investment in Enable each period for contributions made, distributions received, CenterPoint Energy’s share of Enable’s comprehensive income and amortization of basis differences, as appropriate. 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. 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. Other investments, excluding marketable securities, are carried at cost. As of December 31, 2016 , CenterPoint Energy had VIEs consisting of the 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 related property. Creditors of CenterPoint Energy have no recourse to any assets or revenues of the 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. (c) Revenues CenterPoint Energy records revenue for electricity delivery and natural gas sales and services under the accrual method and these revenues are recognized upon delivery to customers. Electricity deliveries not billed by month-end are accrued based on actual AMS data, daily supply volumes and applicable rates. Natural gas sales not billed by month-end are accrued based upon estimated purchased gas volumes, estimated lost and unaccounted for gas and currently effective tariff rates. (d) Long-lived Assets and Intangibles CenterPoint Energy records property, plant and equipment at historical cost. CenterPoint Energy expenses repair and maintenance costs as incurred. CenterPoint Energy periodically evaluates long-lived assets, including property, plant and equipment, and specifically identifiable intangibles, when events or changes in circumstances indicate that the carrying value of these assets may not be recoverable. The determination of whether an impairment has occurred is based on an estimate of undiscounted cash flows attributable to the assets compared to the carrying value of the assets. (e) Regulatory Assets and Liabilities CenterPoint Energy applies the guidance for accounting for regulated operations to the Electric Transmission & Distribution business segment and the Natural Gas Distribution business segment. CenterPoint Energy’s rate-regulated subsidiaries may collect revenues subject to refund pending final determination in rate proceedings. In connection with such revenues, estimated rate refund liabilities are recorded which reflect management’s current judgment of the ultimate outcomes of the proceedings. CenterPoint Energy had current regulatory assets of $70 million and $21 million as of December 31, 2016 and 2015, respectively, included in other current assets in its Consolidated Balance Sheets. CenterPoint Energy had current regulatory liabilities of $18 million and $57 million as of December 31, 2016 and 2015, respectively, included in other current liabilities in its Consolidated Balance Sheets. CenterPoint Energy’s rate-regulated businesses recognize removal costs as a component of depreciation expense in accordance with regulatory treatment. As of December 31, 2016 and 2015 , these removal costs of $1,010 million and $980 million , respectively, are classified as regulatory liabilities in CenterPoint Energy’s Consolidated Balance Sheets. In addition, a portion of the amount of removal costs that relate to AROs has been reclassified from a regulatory liability to an asset retirement liability in accordance with accounting guidance for AROs. (f) Depreciation and Amortization Expense Depreciation and amortization is computed using the straight-line method based on economic lives or regulatory-mandated recovery periods. Amortization expense includes amortization of regulatory assets and other intangibles. (g) Capitalization of Interest and AFUDC Interest and AFUDC are capitalized as a component of projects under construction and are amortized over the assets’ estimated useful lives once the assets are placed in service. AFUDC represents the composite interest cost of borrowed funds and a reasonable return on the equity funds used for construction for subsidiaries that apply the guidance for accounting for regulated operations. Although AFUDC increases both utility plant and earnings, it is realized in cash when the assets are included in rates. During 2016 , 2015 and 2014 , CenterPoint Energy capitalized interest and AFUDC of $8 million , $10 million and $11 million , respectively. During 2016 , 2015 and 2014 , CenterPoint Energy recorded AFUDC equity of $7 million , $12 million and $14 million , respectively, which is included in Other Income in its Statements of Consolidated Income. (h) Income Taxes CenterPoint Energy uses the asset and liability method of accounting for deferred income taxes. Deferred income tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. A valuation allowance is established against deferred tax assets for which management believes realization is not considered to be more likely than not. CenterPoint Energy recognizes interest and penalties as a component of income tax expense. CenterPoint Energy reports the income tax provision associated with its interest in Enable in Income tax expense (benefit) in its Statements of Consolidated Income. (i) Accounts Receivable and Allowance for Doubtful Accounts Accounts receivable are recorded at the invoiced amount and do not bear interest. It is the policy of management to review the outstanding accounts receivable monthly, as well as the bad debt write-offs experienced in the past, and establish an allowance for doubtful accounts. Account balances are charged off against the allowance when management determines it is probable the receivable will not be recovered. The provision for doubtful accounts in CenterPoint Energy’s Statements of Consolidated Income for 2016 , 2015 and 2014 was $7 million , $19 million and $22 million , respectively. (j) Inventory Inventory consists principally of materials and supplies and natural gas. Materials and supplies are valued at the lower of average cost or market. Materials and supplies are recorded to inventory when purchased and subsequently charged to expense or capitalized to plant when installed. Natural gas inventories of CenterPoint Energy’s Energy Services business segment are valued at the lower of average cost or market. Natural gas inventories of CenterPoint Energy’s Natural Gas Distribution business segment are primarily valued at weighted average cost. During 2016 , 2015 and 2014 , CenterPoint Energy recorded $1 million , $4 million and $8 million , respectively, in write-downs of natural gas inventory to the lower of average cost or market. (k) 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, weather and interest rates on its operating results and cash flows. Such derivatives are recognized in CenterPoint Energy’s 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 normal 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 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. (l) Investments in Other Debt and Equity Securities CenterPoint Energy reports securities classified as trading at estimated fair value in its Consolidated Balance Sheets, and any unrealized holding gains and losses are recorded as other income (expense) in its Statements of Consolidated Income. (m) Environmental Costs CenterPoint Energy expenses or capitalizes environmental expenditures, as appropriate, depending on their future economic benefit. CenterPoint Energy expenses amounts that relate to an existing condition caused by past operations that do not have future economic benefit. CenterPoint Energy records undiscounted liabilities related to these future costs when environmental assessments and/or remediation activities are probable and the costs can be reasonably estimated. (n) Statements of Consolidated Cash Flows For purposes of reporting cash flows, CenterPoint Energy considers cash equivalents to be short-term, highly-liquid investments with maturities of three months or less from the date of purchase. In connection with the issuance of securitization bonds, CenterPoint Energy was required to establish restricted cash accounts to collateralize the bonds that were issued in these financing transactions. These restricted cash accounts are not available for withdrawal until the maturity of the bonds and are not included in cash and cash equivalents. These restricted cash accounts of $40 million and $35 million as of December 31, 2016 and 2015 , respectively, are included in other current assets in CenterPoint Energy’s Consolidated Balance Sheets. Cash and cash equivalents included $340 million and $264 million as of December 31, 2016 and 2015 , respectively, that was held by the Bond Companies solely to support servicing the securitization bonds. CenterPoint Energy considers distributions received from equity method investments which do not exceed cumulative equity in earnings subsequent to the date of investment to be a return on investment and classifies these distributions as operating activities in the Statements of Consolidated Cash Flows. CenterPoint Energy considers distributions received from equity method investments in excess of cumulative equity in earnings subsequent to the date of investment to be a return of investment and classifies these distributions as investing activities in the Statements of Consolidated Cash Flows. (o) New Accounting Pronouncements In February 2015, the FASB issued ASU No. 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis (ASU 2015-02). ASU 2015 -02 changes the analysis that reporting organizations must perform to evaluate whether they should consolidate certain legal entities, such as limited partnerships. The changes include, among others, modification of the evaluation of whether limited partnerships and similar legal entities are VIEs or voting interest entities and elimination of the presumption that a general partner should consolidate a limited partnership. ASU 2015-02 does not amend the related party guidance for situations in which power is shared between two or more entities that hold interests in a VIE. CenterPoint Energy adopted ASU 2015-02 on January 1, 2016, which did not have a material impact on its financial position, results of operations, cash flows and disclosures. In April 2015, the FASB issued ASU No. 2015-03, Interest-Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Cost (ASU 2015-03) . ASU 2015-03 requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The recognition and measurement guidance for debt issuance costs are not affected by ASU 2015-03. CenterPoint Energy adopted ASU 2015-03 retrospectively on January 1, 2016, which resulted in a reduction of other long-term assets, indexed debt and total long-term debt on its Consolidated Balance Sheets. CenterPoint Energy had debt issuance costs, excluding amounts related to credit facility arrangements, of $42 million and $44 million as a reduction to long-term debt on its Consolidated Balance Sheets as of December 31, 2016 and 2015 , respectively. In May 2015, the FASB issued ASU No. 2015-07, Fair Value Measurement (Topic 820): Disclosures for Investments in Certain Entities That Calculate Net Asset Value per Share (or Its Equivalent) (ASU 2015-07). ASU 2015-07 removes the requirement to categorize within the fair value hierarchy investments for which fair values are measured at NAV using the practical expedient. Entities will be required to disclose the fair value of investments measured using the NAV practical expedient so that financial statement users can reconcile amounts reported in the fair value hierarchy table to amounts reported on the balance sheet. CenterPoint Energy retrospectively adopted ASU 2015-07 on January 1, 2016, which impacts its employee benefit plan disclosures. See Note 7 for the impacts on the employee benefit plan disclosures. This standard did not have an impact on CenterPoint Energy’s financial position, results of operations or cash flows. In September 2015, the FASB issued ASU No. 2015-16, Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments (ASU 2015-16). ASU 2015-16 eliminates the requirement for an acquirer in a business combination to account for measurement-period adjustments retrospectively. Instead, an acquirer would recognize a measurement-period adjustment during the period in which the amount of the adjustment is determined. CenterPoint Energy prospectively adopted ASU 2015-16 on January 1, 2016, which did not have an impact on its financial position, results of operations or cash flows. In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments-Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities (ASU 2016-01). ASU 2016-01 requires equity investments that do not result in consolidation and are not accounted for under the equity method to be measured at fair value and to recognize any changes in fair value in net income unless the investments qualify for the new practicability exception. It does not change the guidance for classifying and measuring investments in debt securities and loans. ASU 2016-01 also changes certain disclosure requirements and other aspects related to recognition and measurement of financial assets and financial liabilities. ASU 2016-01 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017. As of the first reporting period in which the guidance is adopted, a cumulative-effect adjustment to beginning retained earnings will be made, with two features that will be adopted prospectively. CenterPoint Energy is currently assessing the impact that this standard will have on its financial position, results of operations, cash flows and disclosures. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (ASU 2016-02). ASU 2016-02 provides a comprehensive new lease model that requires lessees to recognize assets and liabilities for most leases and would change certain aspects of lessor accounting. ASU 2016-02 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018, with early adoption permitted. A modified retrospective adoption approach is required. CenterPoint Energy is currently assessing the impact that this standard will have on its financial position, results of operations, cash flows and disclosures. In 2016, the FASB issued ASUs which amended ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) . ASU 2014-09, as amended, provides a comprehensive new revenue recognition model that requires revenue to be recognized in a manner that depicts the transfer of goods or services to a customer at an amount that reflects the consideration expected to be received in exchange for those goods or services. Early adoption is not permitted, and entities have the option of using either a full retrospective or a modified retrospective adoption approach. CenterPoint Energy is currently evaluating its revenue streams under these ASUs and has not yet identified any significant changes as the result of these new standards. A substantial amount of CenterPoint Energy’s revenues are tariff based, which we do not anticipate will be significantly impacted by these ASUs. CenterPoint Energy is considering the impacts of the new guidance on its ability to recognize revenue for certain contracts when collectability is uncertain and its accounting for contributions in aid of construction. CenterPoint Energy expects to adopt these ASUs on January 1, 2018 and is evaluating the method of adoption. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (ASU 2016-15). ASU 2016-15 provides clarifying guidance on the classification of certain cash receipts and payments in the statement of cash flows and eliminates the variation in practice related to such classifications. ASU 2016-15 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017, with early adoption permitted. A retrospective adoption approach is required. CenterPoint Energy is currently assessing the impact that this standard will have on its statement of cash flows. In November 2016, the FASB issued ASU No. 2016-18 , Statement of Cash Flows (Topic 230): Restricted Cash (ASU 2016-18). ASU 2016-18 requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, restricted cash and restricted cash equivalents. As a result, the statement of cash flows will no longer present transfers between cash and cash equivalents and restricted cash and restricted cash equivalents. When cash, cash equivalents, restricted cash and restricted cash equivalents are presented in more than one line item on the balance sheet, the new guidance requires a reconciliation of the totals in the statement of cash flows to the related captions in the balance sheet. ASU 2016-18 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017, with early adoption permitted. A retrospective adoption approach is required. CenterPoint Energy is currently assessing the impact that this standard will have on its statement of cash flows and disclosures. In January 2017, the FASB issued ASU No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business (ASU 2017-01). ASU 2017-01 revises the definition of a business. If substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or a group of similar identifiable assets, then under ASU 2017-01, the asset or group of assets is not a business. The guidance also requires a business to include at least one substantive process and narrows the definition of outputs to be more closely aligned with how outputs are described in ASC 606. ASU 2017-01 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017, with early adoption permitted in certain circumstances. A prospective adoption approach is required. ASU 2017-01 could have a potential impact on CenterPoint Energy’s accounting for future acquisitions. In January 2017, the FASB issued ASU No. 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (ASU 2017-04). ASU 2017-04 eliminates Step 2 of the goodwill impairment test, which requires a hypothetical purchase price allocation. A goodwill impairment will now be the amount by which a reporting unit’s carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. ASU 2017-04 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019, with early adoption permitted. A prospective adoption approach is required. ASU 2017-04 will have an impact on CenterPoint Energy’s future calculation of goodwill impairments if an impairment is identified. 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.

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment [Text Block]	Property, Plant and Equipment (a) Property, Plant and Equipment Property, plant and equipment includes the following: Weighted Average Useful Lives December 31, (in years) 2016 2015 (in millions) Electric Transmission & Distribution 32 $ 10,840 $ 10,142 Natural Gas Distribution 32 6,219 5,762 Energy Services 25 83 86 Other property 25 689 660 Total 17,831 16,650 Accumulated depreciation and amortization: Electric Transmission & Distribution 3,443 3,209 Natural Gas Distribution 1,722 1,575 Energy Services 29 34 Other property 330 295 Total accumulated depreciation and amortization 5,524 5,113 Property, plant and equipment, net $ 12,307 $ 11,537 (b) Depreciation and Amortization The following table presents depreciation and amortization expense for 2016 , 2015 and 2014 . 2016 2015 2014 (in millions) Depreciation expense $ 607 $ 557 $ 521 Amortization expense 519 413 492 Total depreciation and amortization expense $ 1,126 $ 970 $ 1,013 (c) AROs A reconciliation of the changes in the ARO liability is as follows: December 31, 2016 2015 (in millions) Beginning balance $ 195 $ 176 Accretion expense 10 6 Revisions in estimates of cash flows — 13 Ending balance $ 205 $ 195 CenterPoint Energy recorded AROs associated with the removal of asbestos and asbestos-containing material in its buildings, including substation building structures. CenterPoint Energy also recorded AROs relating to gas pipelines abandoned in place, treated wood poles for electric distribution, distribution transformers containing PCB (also known as Polychlorinated Biphenyl), and underground fuel storage tanks. The estimates of future liabilities were developed using historical information, and where available, quoted prices from outside contractors. The increase of $13 million in the ARO from the revision in estimates in 2015 is primarily attributable to an increase in estimated disposal costs.

Acquisition

Acquisition	12 Months Ended
	Dec. 31, 2016
Business Combinations [Abstract]
Acquisition [Text Block]	Acquisition On April 1, 2016, CES, an indirect, wholly-owned subsidiary of CenterPoint Energy, closed the previously announced agreement to acquire the retail energy services business and natural gas wholesale assets of Continuum. After working capital adjustments, the final purchase price was $102 million and allocated to identifiable assets acquired and liabilities assumed based on their estimated fair values on the acquisition date. The following table summarizes the final purchase price allocation and the fair value amounts recognized for the assets acquired and liabilities assumed related to the acquisition: (in millions) Total purchase price consideration $ 102 Receivables $ 76 Derivative assets 38 Property and equipment 1 Identifiable intangibles 38 Total assets acquired 153 Accounts payable 49 Derivative liabilities 24 Total liabilities assumed 73 Identifiable net assets acquired 80 Goodwill 22 Net assets acquired $ 102 The goodwill of $22 million resulting from the acquisition reflects the excess of the purchase price over the fair value of the net identifiable assets acquired. The goodwill recorded as part of the acquisition primarily reflects the value of the complementary operational and geographic footprints, along with the scale, geographic reach and expanded capabilities. Identifiable intangible assets were recorded at estimated fair value as determined by management based on available information, which includes a valuation prepared by an independent third party. The significant assumptions used in arriving at the estimated identifiable intangible asset values included management’s estimates of future cash flows, the discount rate which is based on the weighted average cost of capital for comparable publicly traded guideline companies and projected customer attrition rates. The useful lives for the identifiable intangible assets were determined using methods that approximate the pattern of economic benefit provided by the utilization of the assets. The estimated fair value of the identifiable intangible assets and related useful lives as included in the final purchase price allocation include: Estimate Fair Value Estimate Useful Life (in millions) (in years) Customer relationships $ 34 15 Covenants not to compete 4 4 Total identifiable intangibles $ 38 Amortization expense related to the above identifiable intangible assets was $3 million for the year ended December 31, 2016. Revenues of approximately $466 million and operating income of approximately $1 million attributable to the acquisition are included in CenterPoint Energy’s Statements of Consolidated Income for the year ended December 31, 2016. As Continuum was a non-public company that did not prepare interim financial information and the acquisition included the purchase of both businesses and assets, the historical financial information for the businesses and assets acquired was impracticable to obtain. As a result, pro forma results of the acquired businesses and assets are not presented.

Goodwill

Goodwill	12 Months Ended
	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill [Text Block]	Goodwill Goodwill by reportable business segment as of December 31, 2015 and changes in the carrying amount of goodwill as of December 31, 2016 are as follows: December 31, 2015 Continuum Acquisition (1) December 31, (in millions) Natural Gas Distribution $ 746 $ — $ 746 Energy Services 83 (2) 22 105 (2) Other Operations 11 — 11 Total $ 840 $ 22 $ 862 (1) See Note 4 . (2) Amount presented is net of the accumulated goodwill impairment charge of $252 million . CenterPoint Energy performs 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 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 goodwill impairment test in the third quarter of each of 2016 and 2015 and determined, based on the results of the first step, that no goodwill impairment charge was required for any reportable segment. Other intangibles were not material as of December 31, 2016 and 2015 .

Regulatory Accounting

Regulatory Accounting	12 Months Ended
	Dec. 31, 2016
Regulated Operations [Abstract]
Regulatory Accounting [Text Block]	Regulatory Accounting The following is a list of regulatory assets/liabilities reflected on CenterPoint Energy’s Consolidated Balance Sheets as of December 31, 2016 and 2015 : December 31, 2016 2015 (in millions) Securitized regulatory assets $ 1,919 $ 2,373 Unrecognized equity return (1) (329 ) (393 ) Unamortized loss on reacquired debt 84 93 Pension and postretirement-related regulatory asset (2) 809 872 Other long-term regulatory assets (3) 194 184 Total regulatory assets 2,677 3,129 Estimated removal costs 1,010 980 Other long-term regulatory liabilities 288 296 Total regulatory liabilities 1,298 1,276 Total regulatory assets and liabilities, net $ 1,379 $ 1,853 (1) The unrecognized allowed equity return will be recognized as it is recovered in rates through 2024. During the years ended December 31, 2016 , 2015 and 2014 , Houston Electric recognized approximately $64 million , $49 million and $68 million , respectively, of the allowed equity return. The timing of CenterPoint Energy’s recognition of the allowed equity return will vary each period based on amounts actually collected during the period. The actual amounts recovered for the allowed equity return are reviewed and adjusted at least annually by the PUCT to correct any over-collections or under-collections during the preceding 12 months and to provide for the full and timely recovery of the allowed equity return. (2) NGD’s actuarially determined pension and other postemployment expense in excess of the amount being recovered through rates is being deferred for rate making purposes. Deferred pension and other postemployment expenses of $6 million and $5 million as of December 31, 2016 and 2015, respectively, were not earning a return. (3) Other regulatory assets that are not earning a return were not material as of December 31, 2016 and 2015 .

Stock-Based Incentive Compensat

Stock-Based Incentive Compensation Plans and Employee Benefit Plans	12 Months Ended
	Dec. 31, 2016
Disclosure of Stock-Based Incentive Compensation Plans and Employee Benefit Plans [Abstract]
Stock-Based Incentive Compensation Plans and Employee Benefit Plans [Text Block]	Stock-Based Incentive Compensation Plans and Employee Benefit Plans (a) Stock-Based Incentive Compensation Plans CenterPoint Energy has LTIPs that provide for the issuance of stock-based incentives, including stock options, performance awards, restricted stock unit awards and restricted and unrestricted stock awards to officers, employees and non-employee directors. Approximately 14 million shares of CenterPoint Energy common stock are authorized under these plans for awards. Equity awards are granted to employees without cost to the participants. The performance awards granted in 2016 , 2015 and 2014 are distributed based upon the achievement of certain objectives over a three-year performance cycle. The stock awards granted in 2016 , 2015 and 2014 are service based. The stock awards generally vest at the end of a three-year period. Upon vesting, both the performance and stock awards are issued to the participants along with the value of dividend equivalents earned over the performance cycle or vesting period. CenterPoint Energy issues new shares to satisfy stock-based payments related to LTIPs. CenterPoint Energy recorded LTIP compensation expense of $19 million , $17 million and $18 million for the years ended December 31, 2016 , 2015 and 2014 , respectively. This expense is included in Operation and Maintenance Expense in the Statements of Consolidated Income. The total income tax benefit recognized related to LTIPs was $7 million , $6 million and $7 million for the years ended December 31, 2016 , 2015 and 2014 , respectively. No compensation cost related to LTIPs was capitalized as a part of inventory or fixed assets in 2016 , 2015 or 2014 . The actual tax benefit realized for tax deductions related to LTIPs totaled $5 million , $6 million and $13 million for 2016 , 2015 and 2014 , respectively. Compensation costs for the performance and stock awards granted under LTIPs are measured using fair value and expected achievement levels on the grant date. For performance awards with operational goals, the achievement levels are revised as goals are evaluated. The fair value of awards granted to employees is based on the closing stock price of CenterPoint Energy’s common stock on the grant date. The compensation expense is recorded on a straight-line basis over the vesting period. Forfeitures are estimated on the date of grant based on historical averages, and estimates are updated periodically throughout the vesting period. The following tables summarize CenterPoint Energy’s LTIP activity for 2016 : Stock Options CenterPoint Energy has not issued stock options since 2004. There were no outstanding stock options at either December 31, 2016 or 2015. Cash received from stock options exercised was $1 million for 2014 . Performance Awards Outstanding and Non-Vested Shares Year Ended December 31, 2016 Shares (Thousands) Weighted-Average Grant Date Fair Value Remaining Average Contractual Life (Years) Aggregate Intrinsic Value (Millions) Outstanding as of December 31, 2015 2,628 $ 21.95 Granted 1,525 18.98 Forfeited or canceled (404 ) 20.68 Vested and released to participants (326 ) 20.68 Outstanding as of December 31, 2016 3,423 20.90 1.2 $ 43 The outstanding and non-vested shares displayed in the table above assumes that shares are issued at the maximum performance level. The aggregate intrinsic value reflects the impact of current expectations of achievement and stock price. Stock Awards Outstanding and Non-Vested Shares Year Ended December 31, 2016 Shares (Thousands) Weighted-Average Grant Date Fair Value Remaining Average Contractual Life (Years) Aggregate Intrinsic Value (Millions) Outstanding as of December 31, 2015 747 $ 21.86 Granted 464 19.24 Forfeited or canceled (19 ) 20.53 Vested and released to participants (272 ) 21.26 Outstanding as of December 31, 2016 920 20.74 1.3 $ 23 The weighted-average grant-date fair values per unit of awards granted were as follows for 2016 , 2015 and 2014 : Year Ended December 31, 2016 2015 2014 Performance awards $ 18.98 $ 21.28 $ 23.70 Stock awards 19.24 21.39 23.89 Valuation Data The total intrinsic value of awards received by participants was as follows for 2016 , 2015 and 2014 : Year Ended December 31, 2016 2015 2014 (in millions) Stock options exercised $ — $ — $ 2 Performance awards 7 9 24 Stock awards 6 7 10 The total grant date fair value of performance and stock awards which vested during the years ended December 31, 2016 , 2015 and 2014 was $13 million , $13 million and $21 million , respectively. As of December 31, 2016 , there was $21 million of total unrecognized compensation cost related to non-vested performance and stock awards which is expected to be recognized over a weighted-average period of 1.7 years. (b) Pension and Postretirement Benefits CenterPoint Energy maintains a non-contributory qualified defined benefit pension plan covering substantially all employees, with benefits determined using a cash balance formula. Under the cash balance formula, participants accumulate a retirement benefit based upon 5% of eligible earnings and accrued interest. Participants are 100% vested in their benefit after completing three years of service. In addition to the non-contributory qualified defined benefit pension plan, CenterPoint Energy maintains unfunded non-qualified benefit restoration plans which allow participants to receive the benefits to which they would have been entitled under CenterPoint Energy’s non-contributory pension plan except for federally mandated limits on qualified plan benefits or on the level of compensation on which qualified plan benefits may be calculated. CenterPoint Energy provides certain healthcare and life insurance benefits for retired employees on both a contributory and non-contributory basis. Employees become eligible for these benefits if they have met certain age and service requirements at retirement, as defined in the plans. Such benefit costs are accrued over the active service period of employees. The net unrecognized transition obligation is being amortized over approximately 20 years . Effective January 1, 2017, members of the IBEW Local Union 66 who retire on or after January 1, 2017, and their dependents, will receive any retiree medical and prescription drug benefits exclusively through the NECA/IBEW Family Medical Care Plan pursuant to the terms of the renegotiated collective bargaining agreement entered into in May 2016. CenterPoint Energy’s net periodic cost includes the following components relating to pension, including the benefit restoration plan, and postretirement benefits: Year Ended December 31, 2016 2015 2014 Pension Post-retirement Pension Benefits Post-retirement Benefits Pension Benefits Post-retirement Benefits (in millions) Service cost $ 38 $ 2 $ 41 $ 2 $ 42 $ 2 Interest cost 93 16 93 20 100 22 Expected return on plan assets (101 ) (6 ) (120 ) (7 ) (125 ) (7 ) Amortization of prior service cost (credit) 9 (3 ) 9 (1 ) 10 (1 ) Amortization of net loss 63 1 57 5 44 1 Amortization of transition obligation — — — — — 5 Curtailment (1) — (5 ) — — 6 — Settlement (2) — — 10 — — — Net periodic cost $ 102 $ 5 $ 90 $ 19 $ 77 $ 22 (1) A curtailment gain or loss is required when the expected future services of a significant number of current employees are reduced or eliminated for the accrual of benefits. During the fourth quarter of 2014, CenterPoint Energy recognized a curtailment pension loss of $6 million related to employees seconded to Enable. Substantially all of the seconded employees became employees of Enable effective January 1, 2015. Also, postretirement healthcare benefits were amended during 2016 resulting in a net curtailment gain of $5 million . In May 2016, Houston Electric entered into a renegotiated collective bargaining agreement with the IBEW Local Union 66 that provides that for Houston Electric union employees covered under the agreement who retire on or after January 1, 2017, retiree medical and prescription drug coverage will be provided exclusively through the NECA/IBEW Family Medical Care Plan in exchange for the payment of monthly premiums as determined under the agreement. As a result, the accrued postretirement benefits related to such future Houston Electric union retirees were eliminated. Houston Electric recognized a curtailment gain of $3 million as an accelerated recognition of the prior service credit that would otherwise be recognized in future periods for the post-retirement plan. CenterPoint Energy also recognized an additional curtailment gain of $2 million in October 2016 related to other amendments in the post-retirement plan. As a result of these amendments, the 2016 post-retirement expense was significantly lower than expenses reported for previous years. (2) A one-time, non-cash settlement charge is required when lump sum distributions or other settlements of plan benefit obligations during a plan year exceed the service cost and interest cost components of net periodic cost for that year. Due to the amount of lump sum payment distributions from the non-qualified pension plan during the year ended December 31, 2015, CenterPoint Energy recognized a non-cash settlement charge of $10 million . This charge is an acceleration of costs that would otherwise be recognized in future periods. CenterPoint Energy used the following assumptions to determine net periodic cost relating to pension and postretirement benefits: Year Ended December 31, 2016 2015 2014 Pension Post-retirement Pension Benefits Post-retirement Benefits Pension Post-retirement Discount rate 4.40 % 4.35 % 4.05 % 3.90 % 4.80 % 4.75 % Expected return on plan assets 6.25 4.80 6.50 5.20 7.00 5.50 Rate of increase in compensation levels 4.15 — 4.00 — 3.90 — In determining net periodic benefits cost, CenterPoint Energy uses fair value, as of the beginning of the year, as its basis for determining expected return on plan assets. The following table summarizes changes in the benefit obligation, plan assets, the amounts recognized in consolidated balance sheets and the key assumptions of CenterPoint Energy’s pension, including benefit restoration, and postretirement plans. The measurement dates for plan assets and obligations were December 31, 2016 and 2015 . December 31, 2016 2015 Pension Post-retirement Pension Benefits Post-retirement Benefits (in millions, except for actuarial assumptions) Change in Benefit Obligation Benefit obligation, beginning of year $ 2,193 $ 432 $ 2,403 $ 529 Service cost 38 2 41 2 Interest cost 93 16 93 20 Participant contributions — 10 — 8 Benefits paid (181 ) (37 ) (234 ) (32 ) Actuarial (gain) loss 54 13 (115 ) (87 ) Medicare reimbursement — 3 — 2 Plan amendment (1) — (56 ) — (10 ) Settlement — — 5 — Benefit obligation, end of year 2,197 383 2,193 432 Change in Plan Assets Fair value of plan assets, beginning of year 1,679 136 1,925 141 Employer contributions 9 18 66 18 Participant contributions — 10 — 8 Benefits paid (181 ) (37 ) (234 ) (32 ) Plan amendment (2) — (20 ) — — Actual investment return (loss) 149 6 (78 ) 1 Fair value of plan assets, end of year 1,656 113 1,679 136 Funded status, end of year $ (541 ) $ (270 ) $ (514 ) $ (296 ) Amounts Recognized in Balance Sheets Current liabilities-other $ (7 ) $ (6 ) $ (8 ) $ (8 ) Other liabilities-benefit obligations (534 ) (264 ) (506 ) (288 ) Net liability, end of year $ (541 ) $ (270 ) $ (514 ) $ (296 ) Actuarial Assumptions Discount rate 4.15 % 4.15 % 4.40 % 4.35 % Expected return on plan assets 6.00 4.50 6.25 4.80 Rate of increase in compensation levels 4.50 — 4.15 — Healthcare cost trend rate assumed for the next year - Pre-65 — 5.75 — 6.00 Healthcare cost trend rate assumed for the next year - Post-65 — 10.65 — 5.50 Prescription drug cost trend rate assumed for the next year — 10.75 — 11.00 Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) — 4.50 — 5.00 Year that the healthcare rate reaches the ultimate trend rate — 2024 — 2024 Year that the prescription drug rate reaches the ultimate trend rate — 2024 — 2024 (1) The Postretirement plan was amended during 2016 to change retiree medical coverage, effective January 1, 2017, as follows: (i) members of the IBEW Local Union 66 who retire on or after January 1, 2017, and their dependents, will receive any retiree medical and prescription drug coverage exclusively through the NECA/IBEW Family Medical Care Plan pursuant to the terms of the renegotiated collective bargaining agreement entered into in May 2016; and (ii) Medicare eligible post-65 retirees will receive coverage through a Medicare Advantage Program, an insured benefit, in lieu of the previous self-insured benefit. These changes resulted in a reduction in our Postretirement Plan liability of $56 million as of December 31, 2016. (2) In May 2016, Houston Electric entered into a renegotiated collective bargaining agreement with the IBEW Local Union 66 and amended the Houston Electric Union Postretirement Trust. The amendment resulted in a split of the trust into two segregated and restricted accounts, one holds assets for the benefit of current, retired on or before December 31, 2016, union retirees and one holds assets for the benefit of post-2016 union retirees who are now covered exclusively by the NECA/IBEW Family Medical Care Plan. Accordingly, $20 million was transferred to the account for post-2016 union retirees. The accumulated benefit obligation for all defined benefit pension plans was $2,168 million and $2,157 million as of December 31, 2016 and 2015 , respectively. The expected rate of return assumption was developed using the targeted asset allocation of CenterPoint Energy’s plans and the expected return for each asset class. The discount rate assumption was determined by matching the projected cash flows of CenterPoint Energy’s plans against a hypothetical yield curve of high-quality corporate bonds represented by a series of annualized individual discount rates from one-half to 99 years . For measurement purposes, medical costs are assumed to increase to 5.75% and 10.65% for the pre-65 and post-65 retirees during 2017 , respectively, and the prescription cost is assumed to increase to 10.75% during 2017 , after which these rates decrease until reaching the ultimate trend rate of 4.50% in 2024. CenterPoint Energy’s changes in accumulated comprehensive loss related to defined benefit, postretirement and other postemployment plans are as follows: Year Ended December 31, 2016 2015 (in millions) Beginning Balance $ (65 ) $ (85 ) Other comprehensive income (loss) before reclassifications (1) (19 ) 21 Amounts reclassified from accumulated other comprehensive income: Prior service cost (2) — 1 Actuarial losses (2) 8 10 Total reclassifications from accumulated other comprehensive income 8 11 Tax benefit (expense) 4 (12 ) Net current period other comprehensive income (loss) (7 ) 20 Ending Balance $ (72 ) $ (65 ) (1) Total other comprehensive income (loss) related to the remeasurement of pension, postretirement and other postemployment plans. (2) These accumulated other comprehensive components are included in the computation of net periodic cost. Amounts recognized in accumulated other comprehensive loss consist of the following: December 31, 2016 2015 Pension Benefits Postretirement Benefits Pension Benefits Postretirement Benefits (in millions) Unrecognized actuarial loss (gain) $ 100 $ 3 $ 106 $ (2 ) Unrecognized prior service cost (credit) 2 6 3 (1 ) Net amount recognized in accumulated other comprehensive loss $ 102 $ 9 $ 109 $ (3 ) The changes in plan assets and benefit obligations recognized in other comprehensive income during 2016 are as follows: Pension Benefits Postretirement Benefits (in millions) Net loss $ 2 $ 11 Amortization of net loss (8 ) — Amortization of prior service credit (cost) (1 ) 1 Total recognized in comprehensive income $ (7 ) $ 12 The total expense recognized in net periodic costs and other comprehensive income was $95 million and $17 million for pension and postretirement benefits, respectively, for the year ended December 31, 2016 . The amounts in accumulated other comprehensive loss expected to be recognized as components of net periodic benefit cost during 2017 are as follows: Pension Benefits Postretirement Benefits (in millions) Unrecognized actuarial loss $ 6 $ — Unrecognized prior service cost 1 1 Amounts in accumulated comprehensive loss to be recognized in net periodic cost in 2017 $ 7 $ 1 The following table displays pension benefits related to CenterPoint Energy’s pension plans that have accumulated benefit obligations in excess of plan assets: December 31, 2016 2015 Pension Qualified Pension Non-qualified Pension Qualified Pension Non-qualified (in millions) Accumulated benefit obligation $ 2,097 $ 71 $ 2,082 $ 75 Projected benefit obligation 2,126 71 2,118 75 Fair value of plan assets 1,656 — 1,679 — Assumed healthcare cost trend rates have a significant effect on the reported amounts for CenterPoint Energy’s postretirement benefit plans. A 1% change in the assumed healthcare cost trend rate would have the following effects: 1% Increase 1% Decrease (in millions) Effect on the postretirement benefit obligation $ 16 $ 15 Effect on total of service and interest cost 1 1 In managing the investments associated with the benefit plans, CenterPoint Energy’s objective is to achieve and maintain a fully funded plan. This objective is expected to be achieved through an investment strategy that manages liquidity requirements while maintaining a long-term horizon in making investment decisions and efficient and effective management of plan assets. As part of the investment strategy discussed above, CenterPoint Energy maintained the following weighted average allocation targets for its benefit plans as of December 31, 2016 : Pension Benefits Postretirement Benefits U.S. equity 12 – 28% 13 – 23% International developed market equity 7 – 17% 3 – 13% Emerging market equity 3 – 13% — Fixed income 54 – 66% 69 – 79% Cash 0 – 2% 0 – 2% The following tables set forth by level, within the fair value hierarchy (see Note 9 ), CenterPoint Energy’s pension plan assets at fair value as of December 31, 2016 and 2015 : Fair Value Measurements as of December 31, 2016 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Cash $ 14 $ — $ — $ 14 Corporate bonds: Investment grade or above — 401 — 401 Equity securities: U.S. companies 73 — — 73 Cash received as collateral from securities lending 69 — — 69 U.S. treasuries 49 — — 49 Mortgage backed securities — 3 — 3 Asset backed securities — 2 — 2 Municipal bonds — 52 — 52 Mutual funds (1) 171 — — 171 International government bonds — 16 — 16 Obligation to return cash received as collateral from securities lending (69 ) — — (69 ) Total investments at fair value $ 307 $ 474 $ — $ 781 Investments measured by net asset value per share or its equivalent (2) 875 Total Investments $ 1,656 (1) 57% of the amount invested in mutual funds was in international equities, 28% was in emerging market equities and 15% was in U.S. equities. (2) This represents the common collective trust funds with 53% of the amount invested in fixed income securities, 12% in U.S. equities, 30% in international equities and 5% in emerging market equities. Fair Value Measurements as of December 31, 2015 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Cash $ 11 $ — $ — $ 11 Corporate bonds: Investment grade or above — 385 — 385 Equity securities: International companies 38 — — 38 U.S. companies 74 — — 74 Cash received as collateral from securities lending 71 — — 71 U.S. treasuries 57 — — 57 Mortgage backed securities — 4 — 4 Asset backed securities — 3 — 3 Municipal bonds — 66 — 66 Mutual funds (1) 144 — — 144 International government bonds — 1 — 1 Obligation to return cash received as collateral from securities lending (71 ) — — (71 ) Total investments at fair value $ 324 $ 459 $ — $ 783 Investments measured by net asset value per share or its equivalent (2) 896 Total investments $ 1,679 (1) 58% of the amount invested in mutual funds was in international equities, 28% was in emerging market equities and 14% was in U.S. equities. (2) This represents the common collective trust funds with 60% of the amount invested in fixed income securities, 11% in U.S. equities, 23% in international equities and 2% in emerging market equities. The pension plan utilized both exchange traded and over-the-counter financial instruments such as futures, interest rate options and swaps that were marked to market daily with the gains/losses settled in the cash accounts. The pension plan did not include any holdings of CenterPoint Energy common stock as of December 31, 2016 or 2015 . The changes in the fair value of the pension plan’s level 3 investments for the years ended December 31, 2016 and 2015 were not material. The following tables present by level, within the fair value hierarchy, CenterPoint Energy’s postretirement plan assets at fair value as of December 31, 2016 and 2015 , by asset category: Fair Value Measurements as of December 31, 2016 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Mutual funds (1) $ 113 $ — $ — $ 113 Total $ 113 $ — $ — $ 113 (1) 74% of the amount invested in mutual funds was in fixed income securities, 18% was in U.S. equities and 8% was in international equities. Fair Value Measurements as of December 31, 2015 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Mutual funds (1) $ 136 $ — $ — $ 136 Total $ 136 $ — $ — $ 136 (1) 72% of the amount invested in mutual funds was in fixed income securities, 20% was in U.S. equities and 8% was in international equities. CenterPoint Energy contributed $-0- , $9 million and $18 million to its qualified pension, non-qualified pension and postretirement benefits plans, respectively, in 2016 . CenterPoint Energy expects to contribute approximately $39 million , $7 million and $16 million to its qualified pension, non-qualified pension and postretirement benefits plans, respectively, in 2017 . The following benefit payments are expected to be paid by the pension and postretirement benefit plans: Pension Benefits Postretirement Benefit Payments (in millions) 2017 $ 140 $ 19 2018 146 20 2019 152 23 2020 155 25 2021 159 28 2022-2026 802 152 (c) Savings Plan CenterPoint Energy has a tax-qualified employee savings plan that includes a cash or deferred arrangement under Section 401(k) of the Internal Revenue Code of 1986, as amended (the Code), and an employee stock ownership plan under Section 4975(e)(7) of the Code. Under the plan, participating employees may contribute a portion of their compensation, on a pre-tax or after-tax basis, generally up to a maximum of 50% of eligible compensation. CenterPoint Energy matches 100% of the first 6% of each employee’s compensation contributed. The matching contributions are fully vested at all times. Participating employees may elect to invest all (prior to January 1, 2016) or a portion of their contributions to the plan in CenterPoint Energy, Inc. common stock, to have dividends reinvested in additional shares or to receive dividend payments in cash on any investment in CenterPoint Energy, Inc. common stock, and to transfer all or part of their investment in CenterPoint Energy, Inc. common stock to other investment options offered by the plan. Effective January 1, 2016, the savings plan was amended to limit the percentage of future contributions that could be invested in CenterPoint Energy, Inc. common stock to 25% and to prohibit transfers of account balances where the transfer would result in more than 25% of a participant’s total account balance invested in CenterPoint Energy, Inc. common stock. The savings plan has significant holdings of CenterPoint Energy, Inc. common stock. As of December 31, 2016 , 14,216,986 shares of CenterPoint Energy, Inc. common stock were held by the savings plan, which represented approximately 17% of its investments. Given the concentration of the investments in CenterPoint Energy, Inc. common stock, the savings plan and its participants have market risk related to this investment. CenterPoint Energy’s savings plan benefit expenses were $38 million , $35 million and $39 million in 2016 , 2015 and 2014 , respectively. (d) Postemployment Benefits CenterPoint Energy provides postemployment benefits for certain former or inactive employees, their beneficiaries and covered dependents, after employment but before retirement (primarily healthcare and life insurance benefits for participants in the long-term disability plan). CenterPoint Energy recorded postemployment expenses of $5 million , $2 million and $3 million in 2016 , 2015 and 2014 , respectively. Included in Benefit Obligations in the accompanying Consolidated Balance Sheets as of December 31, 2016 and 2015 was $22 million and $23 million , respectively, relating to postemployment obligations. (e) Other Non-Qualified Plans CenterPoint Energy has non-qualified deferred compensation plans that provide benefits payable to directors, officers and certain key employees or their designated beneficiaries at specified future dates or upon termination, retirement or death. Benefit payments are made from the general assets of CenterPoint Energy. CenterPoint Energy recorded benefit expense relating to these plans of $3 million , $3 million and $5 million for the years in 2016 , 2015 and 2014 , respectively. Included in Benefit Obligations in the accompanying Consolidated Balance Sheets as of December 31, 2016 and 2015 was $47 million and $51 million , respectively, relating to deferred compensation plans. Included in Benefit Obligations in CenterPoint Energy’s Consolidated Balance Sheets as of December 31, 2016 and 2015 was $40 million and $32 million , respectively, relating to split-dollar life insurance arrangements. (f) Change in Control Agreements and Other Employee Matters CenterPoint Energy had change in control agreements with certain of its officers, which expired December 31, 2014. In lieu of these agreements, our Board of Directors approved a new change in control plan, which was effective January 1, 2015. The plan, like the expired agreements, generally provides, to the extent applicable, in the case of a change in control of CenterPoint Energy and termination of employment, for severance benefits of up to three times annual base salary plus bonus, and other benefits. Our officers, including our Executive Chairman, are participants under the plan. As of December 31, 2016 , approximately 35% of CenterPoint Energy’s employees were covered by collective bargaining agreements. The collective bargaining agreement with the IBEW Local 66 and the two collective bargaining agreements with Professional Employees International Union Local 12, which collectively cover approximately 21% of CenterPoint Energy’s employees, expired in March and May of 2016, respectively. CenterPoint Energy successfully negotiated all three follow-on agreements in 2016. The new collective bargaining agreement with the IBEW Local 66 expires in May of 2020, and the two new collective bargaining agreements with Professional Employees International Union Local 12 expire in March and May of 2021, respectively. The collective bargaining agreements with Gas Workers Union, Local 340 and the IBEW, Local 949, covering approximately 8% of CenterPoint Energy’s employees, will expire in April and December of 2020, respectively. These two agreements were last negotiated in 2015. The two collective bargaining agreements with the United Steelworkers Union, Locals 13-227 and 13-1, which cover approximately 6% of CenterPoint Energy’s employees, are scheduled to expire in June and July of 2017, respectively. CenterPoint Energy believes it has good relationships with these bargaining units and expect to negotiate new agreements in 2017.

Derivative Instruments

Derivative Instruments	12 Months Ended
	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments [Text Block]	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, weather and interest rates on its operating results and cash flows. (a) Non-Trading Activities Derivative Instruments. CenterPoint Energy enters into certain derivative instruments to mitigate the effects of commodity price movements. 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 NGD in Arkansas, Louisiana, Mississippi, Minnesota and Oklahoma. NGD and electric operations in Texas do not have such mechanisms, although fixed customer charges are historically higher in Texas for NGD compared to CenterPoint Energy’s other jurisdictions. As a result, fluctuations from normal weather may have a positive or negative effect on NGD’s results in Texas and on Houston Electric’s results in its service territory. CenterPoint Energy has historically entered into heating-degree day swaps for certain NGD jurisdictions to mitigate the effect of fluctuations from normal weather on its results of operations and cash flows for the winter heating season, which contained a bilateral dollar cap of $16 million in 2014–2015. However, NGD did not enter into heating-degree day swaps for the 2015–2016 winter season as a result of NGD’s Minnesota division implementing a full decoupling pilot in July 2015. CenterPoint Energy entered into weather hedges for the Houston Electric service territory, which contained bilateral dollar caps of $8 million , $7 million and $9 million for the 2014–2015, 2015–2016 and 2016–2017 winter seasons, respectively. The swaps are based on 10 -year normal weather. During the years ended December 31, 2016 , 2015 and 2014 , CenterPoint Energy recognized a gain of $1 million , and losses of $6 million and $11 million , respectively, related to these swaps. Weather hedge gains and losses are included in revenues in the Statements of Consolidated Income. Hedging of Interest Expense for Future Debt Issuances. In April 2016, Houston Electric entered into forward interest rate agreements with several counterparties, having an aggregate notional amount of $150 million . These agreements were executed to hedge, in part, volatility in the 5-year U.S. treasury rate by reducing Houston Electric’s exposure to variability in cash flows related to interest payments of Houston Electric’s $300 million issuance of fixed rate debt in May 2016. These forward interest rate agreements were designated as cash flow hedges. The realized gains and losses associated with the agreements were immaterial. In June and July 2016, Houston Electric entered into forward interest rate agreements with several counterparties, having an aggregate notional amount of $300 million . These agreements were executed to hedge, in part, volatility in the 10-year U.S. treasury rate by reducing Houston Electric’s exposure to variability in cash flows related to interest payments of Houston Electric’s $300 million issuance of fixed rate debt in August 2016. These forward interest rate agreements were designated as cash flow hedges. Accordingly, the effective portion of realized gains associated with the agreements, which totaled $1.1 million , is a component of accumulated other comprehensive income and will be amortized over the life of the bonds. The ineffective portion of the gains and losses was recorded in income and was immaterial. In January 2017, Houston Electric entered into forward interest rate agreements with several counterparties, having an aggregate notional amount of $150 million . These agreements were executed to hedge, in part, volatility in the 10-year U.S. treasury rate by reducing Houston Electric’s exposure to variability in cash flows related to interest payments of Houston Electric’s $300 million issuance of fixed rate debt in January 2017. These forward interest rate agreements were designated as cash flow hedges. Accordingly, the effective portion of unrealized losses associated with the agreements, which totaled approximately $0.5 million , will be a component of accumulated other comprehensive income in 2017 and will be amortized over the life of the bonds. (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, 2016 and 2015 , while the last table provides a breakdown of the related income statement impacts for the years ending December 31, 2016 , 2015 and 2014. Fair Value of Derivative Instruments December 31, 2016 Total derivatives not designated as hedging instruments Balance Sheet Location Derivative Assets Fair Value Derivative Liabilities Fair Value (in millions) Natural gas derivatives (1) (2) (3) Current Assets: Non-trading derivative assets $ 79 $ 14 Natural gas derivatives (1) (2) (3) Other Assets: Non-trading derivative assets 24 5 Natural gas derivatives (1) (2) (3) Current Liabilities: Non-trading derivative liabilities 2 43 Natural gas derivatives (1) (2) (3) Other Liabilities: Non-trading derivative liabilities — 5 Indexed debt securities derivative Current Liabilities — 717 Total $ 105 $ 784 (1) The fair value shown for natural gas contracts is comprised of derivative gross volumes totaling 1,035 Bcf or a net 59 Bcf long position. Of the net long position, basis swaps constitute a net 126 Bcf long position. (2) Natural gas contracts are presented on a net basis in the Consolidated Balance Sheets as they are subject to master netting arrangements. This netting applies to all undisputed amounts due or past due and causes derivative assets (liabilities) to be ultimately presented net in a liability (asset) account within the Consolidated Balance Sheets. The net of total non-trading natural gas derivative assets and liabilities was a $24 million asset as shown on CenterPoint Energy’s Consolidated Balance Sheets (and as detailed in the table below), and was comprised of the natural gas contracts derivative assets and liabilities separately shown above, impacted by collateral netting of $14 million . (3) Derivative Assets and Derivative Liabilities include no material amounts related to physical forward transactions with Enable. Offsetting of Natural Gas Derivative Assets and Liabilities December 31, 2016 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 $ 81 $ (30 ) $ 51 Other Assets: Non-trading derivative assets 24 (5 ) 19 Current Liabilities: Non-trading derivative liabilities (57 ) 16 (41 ) Other Liabilities: Non-trading derivative liabilities (10 ) 5 (5 ) Total $ 38 $ (14 ) $ 24 (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 December 31, 2015 Total derivatives not designated as hedging instruments Balance Sheet Location Derivative Assets Fair Value Derivative Liabilities Fair Value (in millions) Natural gas derivatives (1) (2) (3) Current Assets: Non-trading derivative assets $ 90 $ 2 Natural gas derivatives (1) (2) (3) Other Assets: Non-trading derivative assets 36 — Natural gas derivatives (1) (2) (3) Current Liabilities: Non-trading derivative liabilities 10 60 Natural gas derivatives (1) (2) (3) Other Liabilities: Non-trading derivative liabilities 4 25 Indexed debt securities derivative Current Liabilities — 442 Total $ 140 $ 529 (1) The fair value shown for natural gas contracts is comprised of derivative gross volumes totaling 767 Bcf or a net 112 Bcf long position. Of the net long position, basis swaps constitute 133 Bcf. (2) Natural gas contracts are presented on a net basis in the 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 Consolidated Balance Sheets. The net of total non-trading derivative assets and liabilities was a $109 million asset as shown on CenterPoint Energy’s Consolidated Balance Sheets (and as detailed in the table below), and was comprised of the natural gas contracts derivative assets and liabilities separately shown above, impacted by collateral netting of $56 million . (3) Derivative Assets and Derivative Liabilities include no material amounts related to physical forward transactions with Enable. Offsetting of Natural Gas Derivative Assets and Liabilities December 31, 2015 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 $ 100 $ (11 ) $ 89 Other Assets: Non-trading derivative assets 40 (4 ) 36 Current Liabilities: Non-trading derivative liabilities (62 ) 51 (11 ) Other Liabilities: Non-trading derivative liabilities (25 ) 20 (5 ) Total $ 53 $ 56 $ 109 (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. Realized and unrealized gains and losses on natural gas derivatives are recognized in the Statements of Consolidated Income as revenue for retail sales derivative contracts and as natural gas expense for financial natural gas derivatives and non-retail related physical natural gas derivatives. Realized and unrealized gains and losses on indexed debt securities are recorded as Other Income (Expense) in the Statements of Consolidated Income. Income Statement Impact of Derivative Activity Year Ended December 31, Total derivatives not designated as hedging instruments Income Statement Location 2016 2015 2014 (in millions) Natural gas derivatives Gains (Losses) in Revenue $ (18 ) $ 134 $ 35 Natural gas derivatives Gains (Losses) in Expense: Natural Gas 70 (105 ) 11 Indexed debt securities derivative Gains (Losses) in Other Income (Expense) (413 ) 74 (86 ) Total $ (361 ) $ 103 $ (40 ) (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 S&P or Moody’s 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 as of December 31, 2016 and 2015 was $1 million and $3 million , respectively. CenterPoint Energy posted no assets as collateral towards derivative instruments that contain credit risk contingent features as of either December 31, 2016 or 2015 . If all derivative contracts (in a net liability position) containing credit risk contingent features were triggered at December 31, 2016 and 2015 , $-0- and $2 million , respectively, of additional assets would be required to be posted as collateral. (d) Credit Quality of Counterparties In addition to the risk associated with price movements, credit risk is also inherent in CenterPoint Energy’s non-trading derivative activities. Credit risk relates to the risk of loss resulting from non-performance of contractual obligations by a counterparty. The following table shows the composition of counterparties to the non-trading derivative assets of CenterPoint Energy as of December 31, 2016 and 2015 : December 31, 2016 December 31, 2015 Investment Grade(1) Total Investment Grade(1) Total (in millions) Energy marketers $ 1 $ 4 $ 4 $ 10 Financial institutions 33 33 — — End users (2) 2 47 2 115 Total $ 36 $ 84 (3) $ 6 $ 125 (1) “Investment grade” is primarily determined using publicly available credit ratings and considers credit support (including parent company guarantees) and collateral (including cash and standby letters of credit). For unrated counterparties, CenterPoint Energy determines a synthetic credit rating by performing financial statement analysis and considers contractual rights and restrictions and collateral. (2) End users are comprised primarily of customers who have contracted to fix the price of a portion of their physical gas requirements for future periods. (3) The net of total non-trading natural gas derivative assets was $70 million and $125 million as of December 31, 2016 and 2015, respectively, as shown on CenterPoint Energy’s Consolidated Balance Sheets, and was comprised of the natural gas contracts derivatives assets separately shown above, impacted by collateral netting of $14 million and $-0- as of December 31, 2016 and 2015, respectively.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Fair Value Measurements [Text Block]	Fair Value Measurements Assets and liabilities that are recorded at fair value in the 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. At December 31, 2016 , CenterPoint Energy’s Level 3 assets and liabilities are comprised of physical forward contracts and options and its indexed debt securities derivative. Level 3 physical forward contracts are valued using a discounted cash flow model which includes illiquid forward price curve locations (ranging from $2.24 to $7.01 per MMBtu) 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 86% ) as an unobservable input. CenterPoint Energy’s Level 3 physical forward contracts and options 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’s Level 3 indexed debt securities are valued using a Black-Scholes option model and a discounted cash flow model, which use option volatility ( 19% ) and a projected dividend growth rate ( 8% ) as unobservable inputs. An increase in either volatilities or projected dividends will increase the value of the indexed debt securities, and a decrease in either volatilities or projected dividends will decrease the value of the indexed debt securities. 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 year ended December 31, 2016 , there were no transfers between Level 1 and 2. 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, and indicate the fair value hierarchy of the valuation techniques utilized by CenterPoint Energy to determine such fair value. December 31, 2016 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Netting Adjustments (1) Balance (in millions) Assets Corporate equities $ 956 $ — $ — $ — $ 956 Investments, including money market funds (2) 77 — — — 77 Natural gas derivatives (3) 11 74 20 (35 ) 70 Total assets $ 1,044 $ 74 $ 20 $ (35 ) $ 1,103 Liabilities Indexed debt securities derivative $ — $ — $ 717 $ — $ 717 Natural gas derivatives (3) 4 56 7 (21 ) 46 Total liabilities $ 4 $ 56 $ 724 $ (21 ) $ 763 (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 $14 million held by CES from the same counterparties. (2) Amounts are included in Prepaid and Other Current Assets and Other Assets in the Consolidated Balance Sheets. (3) Natural gas derivatives include no material amounts related to physical forward transactions with Enable. December 31, 2015 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Netting Adjustments (1) Balance (in millions) Assets Corporate equities $ 807 $ — $ — $ — $ 807 Investments, including money market funds (2) 53 — — — 53 Natural gas derivatives (3) 4 115 21 (15 ) 125 Total assets $ 864 $ 115 $ 21 $ (15 ) $ 985 Liabilities Indexed debt securities derivative $ — $ 442 $ — $ — $ 442 Natural gas derivatives (3) 13 65 9 (71 ) 16 Total liabilities $ 13 $ 507 $ 9 $ (71 ) $ 458 (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 $56 million posted with the same counterparties. (2) Amounts are included in Prepaid and Other Current Assets and Other Assets in the Consolidated Balance Sheets. (3) Natural gas derivatives include no material amounts related to physical forward transactions with 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 Year Ended December 31, 2016 2015 2014 (in millions) Beginning balance $ 12 $ 17 $ 3 Purchases 12 — — Total gains 12 7 14 Total settlements (27 ) (12 ) 1 Transfers out of Level 3 (1 ) (1 ) — Transfers into Level 3 (1) (712 ) 1 (1 ) Ending balance (2) $ (704 ) $ 12 $ 17 The amount of total gains (losses) for the period included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date (1) $ (402 ) $ 6 $ 16 (1) During 2016, CenterPoint Energy transferred its indexed debt securities from Level 2 to Level 3 to reflect changes in the significance of the unobservable inputs used in the valuation. As of December 31, 2016, the indexed debt securities liability was $717 million . During 2016, there was a loss of $413 million on the indexed debt securities. (2) During 2016, 2015 and 2014, CenterPoint Energy did not have significant Level 3 sales. Items Measured at Fair Value on a Nonrecurring Basis In 2015, CenterPoint Energy determined that an other than temporary decrease in the value of its investment in Enable had occurred and, using multiple valuation methodologies under both the market and income approaches, recorded an impairment on its investment in Enable of $1,225 million . Key assumptions in the market approach included recent market transactions of comparable companies and EBITDA to total enterprise multiples for comparable companies. Due to volatility of the quoted price of Enable’s units at the valuation date, a volume weighted average price was used under the market approach to best approximate fair value at the measurement date. Key assumptions in the income approach included Enable’s forecasted cash distributions, projected cash flows of incentive distribution rights, forecasted growth rate of Enable’s cash distributions beyond 2020, and the discount rate used to determine the present value of the estimated future cash flows. A weighing of the different approaches was utilized to determine the estimated fair value of our investment in Enable. Based on the significant unobservable estimates and assumptions required, CenterPoint Energy concluded that the fair value estimate should be classified as a Level 3 measurement within the fair value hierarchy. See Note 10 for further discussion of the impairments. As of December 31, 2016, there were no significant assets or liabilities measured at fair value on a nonrecurring basis. 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 carrying amounts of non-trading derivative assets and liabilities and CenterPoint Energy’s 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 Consolidated Balance Sheets but for which the fair value is disclosed, would be classified as Level 1 or Level 2 in the fair value hierarchy. December 31, 2016 December 31, 2015 Carrying Amount Fair Value Carrying Amount Fair Value (in millions) Financial assets: Notes receivable - affiliated companies $ — $ — $ 363 $ 356 Financial liabilities: Long-term debt $ 8,443 $ 8,846 $ 8,585 $ 9,067

Unconsolidated Affiliates

Unconsolidated Affiliates	12 Months Ended
	Dec. 31, 2016
Equity Method Investments and Joint Ventures [Abstract]
Unconsolidated Affiliates [Text Block]	Unconsolidated Affiliates CenterPoint Energy has the ability to significantly influence the operating and financial policies of Enable, a publicly traded MLP, and, accordingly, accounts for its investment in Enable’s common and subordinated units using the equity method of accounting. See Note 2 for information on the formation of Enable. CenterPoint Energy’s maximum exposure to loss related to Enable, a VIE in which CenterPoint Energy is not the primary beneficiary, is limited to its equity investment and Series A Preferred Unit investment as presented in the Consolidated Balance Sheet as of December 31, 2016 and outstanding current accounts receivable from Enable. On February 18, 2016, CenterPoint Energy purchased an aggregate of 14,520,000 Series A Preferred Units from Enable for a total purchase price of $363 million , which is accounted for as a cost method investment. In connection with the purchase, Enable redeemed $363 million of notes owed to a wholly-owned subsidiary of CERC Corp., which bore interest at an annual rate of 2.10% to 2.45% . Effective on the Formation Date, CenterPoint Energy and Enable entered into the Transition Agreements. Under the Services Agreement, CenterPoint Energy agreed to provide certain support services to Enable such as accounting, legal, risk management and treasury functions for an initial term, which ended on April 30, 2016. CenterPoint Energy is providing certain services to Enable on a year-to-year basis. Enable may terminate (i) the entire Services Agreement with at least 90 days’ notice prior to the end of any extension term, or (ii) either any service provided under the Services Agreement, or the entire Services Agreement, at any time upon approval by its board of directors and with at least 180 days’ notice. CenterPoint Energy provided seconded employees to Enable to support its operations for a term ending on December 31, 2014. Enable, at its discretion, had the right to select and offer employment to seconded employees from CenterPoint Energy. During the fourth quarter of 2014, Enable notified CenterPoint Energy that it selected seconded employees and provided employment offers to substantially all of the seconded employees from CenterPoint Energy. Substantially all of the seconded employees became employees of Enable effective January 1, 2015. In accordance with the Enable formation agreements, CenterPoint Energy had certain put rights, and Enable had certain call rights, exercisable with respect to the 25.05% interest in SESH retained by CenterPoint Energy. As of June 30, 2015, CenterPoint Energy’s remaining interest in SESH was transferred to Enable. Transactions with Enable: Year Ended December 31, 2016 2015 2014 (in millions) Reimbursement of transition services (1) $ 7 $ 16 $ 163 Natural gas expenses, including transportation and storage costs 110 117 130 Interest income related to notes receivable from Enable 1 8 8 (1) Represents amounts billed under the Transition Agreements, including the costs of seconded employees. Actual transition services costs are recorded net of reimbursement. Year Ended December 31, 2016 2015 (in millions) Accounts receivable for amounts billed for transition services $ 1 $ 3 Interest receivable related to notes receivable from Enable — 4 Accounts payable for natural gas purchases from Enable 10 11 CenterPoint Energy evaluates its equity method investments for impairment when factors indicate that a decrease in the value of its investment has occurred and the carrying amount of its investment may not be recoverable. An impairment loss, based on the excess of the carrying value over estimated fair value of the investment, is recognized in earnings when an impairment is deemed to be other than temporary. Considerable judgment is used in determining if an impairment loss is other than temporary and the amount of any impairment. Based on the sustained low Enable common unit price and further declines in such price during the year ended December 31, 2015, as well as the market outlook for continued depressed crude oil and natural gas prices impacting the midstream oil and gas industry, CenterPoint Energy determined that an other than temporary decrease in the value of its equity method investment in Enable had occurred. CenterPoint Energy wrote down the value of its equity method investment in Enable to its estimated fair value which resulted in impairment charges of $1,225 million for the year ended December 31, 2015. Both the income approach and market approach were utilized to estimate the fair value of CenterPoint Energy’s total investment in Enable, which includes the limited partner common and subordinated units, general partner interest and incentive distribution rights held by CenterPoint Energy. The determination of fair value considered a number of relevant factors including Enable’s common unit price and forecasted results, recent comparable transactions and the limited float of Enable’s publicly traded common units. See Note 9 for further discussion of the determination of fair value of CenterPoint Energy’s equity method investment in Enable in 2015. As of December 31, 2016 , the carrying value of CenterPoint Energy’s equity method investment in Enable was $10.71 per unit, which includes limited partner common and subordinated units, a general partner interest and incentive distribution rights. On December 31, 2016 , Enable’s common unit price closed at $15.73 . There was no impairment indicated in 2016. As there were no identified events or changes in circumstances that may have a significant adverse effect on the fair value of CenterPoint Energy’s cost method investment in Enable’s Series A Preferred Units as of December 31, 2016 , and the investment’s fair value is not readily determinable, an estimate of the fair value of the cost method investment was not performed. Investment in Unconsolidated Affiliates: As of December 31, 2016 2015 (in millions) Enable $ 2,505 $ 2,594 Equity in Earnings (Losses) of Unconsolidated Affiliates, net: Year Ended December 31, 2016 2015 2014 (in millions) Enable $ 208 $ (1,633 ) $ 303 SESH (1) — — 5 Total $ 208 $ (1,633 ) $ 308 (1) CenterPoint Energy contributed a 24.95% interest in SESH to Enable on May 30, 2014 and its remaining 0.1% interest in SESH to Enable on June 30, 2015. Limited Partner Interest in Enable: As of December 31, 2016 2015 2014 CenterPoint Energy 54.1 % (1) 55.4 % 55.4 % OGE 25.7 % 26.3 % 26.3 % (1) In November 2016, Enable closed a public offering of 10,000,000 common units. In connection with the offering, Enable and an affiliate of ArcLight sold an additional combined 1,500,000 common units to the underwriters. Enable Common and Subordinated Units Held: December 31, 2016 Common Subordinated CenterPoint Energy 94,151,707 139,704,916 OGE 42,832,291 68,150,514 Sales of more than 5% of the aggregate of the common units and subordinated units we own in Enable or sales by OGE of more than 5% of the aggregate of the common units and subordinated units it owns in Enable are subject to mutual rights of first offer and first refusal. Enable is controlled jointly by CERC Corp. and OGE, and each own 50% of the management rights in the general partner of Enable. Sale of our or OGE’s ownership interests in Enable’s general partner to a third party is subject to mutual rights of first offer and first refusal, and we are not permitted to dispose of less than all of our interest in Enable’s general partner. Summarized consolidated income (loss) information for Enable is as follows: Year Ended December 31, 2016 2015 2014 (in millions) Operating revenues $ 2,272 $ 2,418 $ 3,367 Cost of sales, excluding depreciation and amortization 1,017 1,097 1,914 Impairment of goodwill and other long-lived assets 9 1,134 8 Operating income (loss) 385 (712 ) 586 Net income (loss) attributable to Enable 290 (752 ) 530 Reconciliation of Equity in Earnings (Losses), net: CenterPoint Energy’s interest $ 160 $ (416 ) $ 298 Basis difference amortization (1) 48 8 5 Impairment of CenterPoint Energy’s equity method investment in Enable — (1,225 ) — CenterPoint Energy’s equity in earnings (losses), net (2) $ 208 $ (1,633 ) $ 303 (1) Equity in earnings of unconsolidated affiliates includes CenterPoint Energy’s share of Enable earnings adjusted for the amortization of the basis difference of CenterPoint Energy’s original investment in Enable and its underlying equity in net assets of Enable. The basis difference is being amortized over approximately 33 years, the average life of the assets to which the basis difference is attributed. (2) These amounts include impairment charges totaling $1,846 million composed of CenterPoint Energy’s impairment of its equity method investment in Enable of $1,225 million and CenterPoint Energy’s share, $621 million , of impairment charges Enable recorded for goodwill and long-lived assets for the year ended December 31, 2015. This impairment is offset by $213 million of earnings for the year ended December 31, 2015. Summarized consolidated balance sheet information for Enable is as follows: December 31, 2016 2015 (in millions) Current assets $ 396 $ 381 Non-current assets 10,816 10,845 Current liabilities 362 615 Non-current liabilities 3,056 3,080 Non-controlling interest 12 12 Preferred equity 362 — Enable partners’ capital 7,420 7,519 Reconciliation of Investment in Enable: CenterPoint Energy’s ownership interest in Enable partners’ capital $ 4,067 $ 4,163 CenterPoint Energy’s basis difference (1,562 ) (1,569 ) CenterPoint Energy’s investment in Enable $ 2,505 $ 2,594 Distributions Received from Unconsolidated Affiliates: Year Ended December 31, 2016 2015 2014 (in millions) Investment in Enable’s common and subordinated units $ 297 $ 294 $ 298 Investment in Enable’s Series A Preferred Units 22 (1 ) — — Interest in SESH (2) — — 7 Total $ 319 $ 294 $ 305 (1) Represents the period from February 18, 2016 to December 31, 2016. (2) CenterPoint Energy contributed a 24.95% interest in SESH to Enable on May 30, 2014 and its remaining 0.1% interest in SESH to Enable on June 30, 2015. As of December 31, 2016 , CERC Corp. and OGE also own 40% and 60% , respectively, of the incentive distribution rights held by the general partner of Enable. Enable is expected to pay a minimum quarterly distribution of $0.2875 per unit on its outstanding units to the extent it has sufficient cash from operations after establishment of cash reserves and payment of fees and expenses, including payments to its general partner and its affiliates, within 60 days after the end of each quarter. If cash distributions to Enable’s unitholders exceed $0.330625 per unit in any quarter, the general partner will receive increasing percentages or incentive distributions rights, up to 50% , of the cash Enable distributes in excess of that amount. In certain circumstances the general partner of Enable will have the right to reset the minimum quarterly distribution and the target distribution levels at which the incentive distributions receive increasing percentages to higher levels based on Enable’s cash distributions at the time of the exercise of this reset election. To date, no incentive distributions have been made.

Indexed Debt Securities (ZENS)

Indexed Debt Securities (ZENS) and Securities Related to ZENS	12 Months Ended
	Dec. 31, 2016
Indexed Debt Securities [Abstract]
Indexed Debt Securities (ZENS) and Securities Related to ZENS [Text Block]	Indexed Debt Securities (ZENS) and Securities Related to ZENS (a) Investment in Securities Related to ZENS In 1995, CenterPoint Energy sold a cable television subsidiary to TW and received TW securities as partial consideration. A subsidiary of CenterPoint Energy now holds 7.1 million shares of TW Common, 0.9 million shares of Time Common and 0.9 million shares of Charter Common, which are classified as trading securities and are expected to be held to facilitate CenterPoint Energy’s ability to meet its obligation under the ZENS. Unrealized gains and losses resulting from changes in the market value of the TW Securities are recorded in CenterPoint Energy’s Statements of Consolidated Income. (b) ZENS In September 1999, CenterPoint Energy issued ZENS having an original principal amount of $1 billion of which $828 million remain outstanding at December 31, 2016 . Each ZENS was originally exchangeable at the holder’s option at any time for an amount of cash equal to 95% of the market value of the reference shares of TW Common attributable to such note. The number and identity of the reference shares attributable to each ZENS are adjusted for certain corporate events. Prior to the closing of the transactions discussed below, the reference shares for each ZENS consisted of 0.5 share of TW Common, 0.125505 share of TWC Common and 0.0625 share of Time Common. On May 26, 2015, Charter announced that it had entered into a definitive merger agreement with TWC. On September 21, 2015, Charter shareholders approved the announced transaction with TWC. Pursuant to the merger agreement, upon closing of the merger, TWC Common would be exchanged for cash and Charter Common and as a result, reference shares for the ZENS would consist of Charter Common, TW Common and Time Common. The merger closed on May 18, 2016. CenterPoint Energy received $100 and 0.4891 shares of Charter Common for each share of TWC Common held, resulting in cash proceeds of $178 million and 872,531 shares of Charter Common. In accordance with the terms of the ZENS, CenterPoint Energy remitted $178 million to ZENS holders in June 2016, which reduced contingent principal. As a result, CenterPoint Energy recorded the following: (in millions) Cash payment to ZENS holders $ 178 Indexed debt – reduction (40 ) Indexed debt securities derivative – reduction (21 ) Loss on indexed debt securities $ 117 As of December 31, 2016 , the reference shares for each ZENS consisted of 0.5 share of TW Common, 0.0625 share of Time Common and 0.061382 share of Charter Common. On October 22, 2016, AT&T announced that it had entered into a definitive agreement to acquire TW in a stock and cash transaction. Pursuant to the agreement, TW Common would be exchanged for cash and AT&T Common, and as a result, reference shares would consist of Charter Common, Time Common and AT&T Common. AT&T announced that the merger is expected to close by the end of 2017. CenterPoint Energy pays interest on the ZENS at an annual rate of 2% plus the amount of any quarterly cash dividends paid in respect of the reference shares attributable to the ZENS. The principal amount of ZENS is subject to being increased or decreased to the extent that the annual yield from interest and cash dividends on the reference shares is less than or more than 2.309% . The adjusted principal amount is defined in the ZENS instrument as “contingent principal.” At December 31, 2016 , ZENS having an original principal amount of $828 million and a contingent principal amount of $514 million were outstanding and were exchangeable, at the option of the holders, for cash equal to 95% of the market value of reference shares deemed to be attributable to the ZENS. As of December 31, 2016 , the market value of such shares was approximately $953 million , which would provide an exchange amount of $1,094 for each $1,000 original principal amount of ZENS. At maturity of the ZENS in 2029 , CenterPoint Energy will be obligated to pay in cash the higher of the contingent principal amount of the ZENS or an amount based on the then-current market value of the reference shares, which will include any additional publicly-traded securities distributed with respect to the current reference shares prior to maturity. The ZENS obligation is bifurcated into a debt component and a derivative component (the holder’s option to receive the appreciated value of the reference shares at maturity). The bifurcated debt component accretes through interest charges at 19.5% annually up to the contingent principal amount of the ZENS in 2029. Such accretion will be reduced by annual cash interest payments, as described above. The derivative component is recorded at fair value and changes in the fair value of the derivative component are recorded in CenterPoint Energy’s Statements of Consolidated Income. Changes in the fair value of the TW Securities held by CenterPoint Energy are expected to substantially offset changes in the fair value of the derivative component of the ZENS. The following table sets forth summarized financial information regarding CenterPoint Energy’s investment in TW Securities and each component of CenterPoint Energy’s ZENS obligation. TW Securities Debt Component of ZENS (1) Derivative Component of ZENS (in millions) Balance as of December 31, 2013 $ 767 $ 132 $ 455 Accretion of debt component of ZENS — 27 — 2% interest paid — (17 ) — Loss on indexed debt securities — — 86 Gain on TW Securities 163 — — Balance as of December 31, 2014 930 142 541 Accretion of debt component of ZENS — 27 — 2% interest paid — (17 ) — Sale of TW Securities (32 ) — — Distribution to ZENS holders — (7 ) (18 ) Gain on indexed debt securities — — (81 ) Loss on TW Securities (93 ) — — Balance as of December 31, 2015 805 145 442 Accretion of debt component of ZENS — 26 — 2% interest paid — (17 ) — Sale of TW securities (178 ) — — Distribution to ZENS holders — (40 ) (21 ) Loss on indexed debt securities — — 296 Gain on TW Securities 326 — — Balance as of December 31, 2016 $ 953 $ 114 $ 717 (1) To reflect adoption of ASU 2015-03, balances have been restated to include unamortized debt issuance costs of $9 million , $10 million and $11 million as of December 31, 2015, 2014 and 2013, respectively.

Equity

Equity	12 Months Ended
	Dec. 31, 2016
Stockholders' Equity Note [Abstract]
Equity [Text Block]	Equity Dividends Declared CenterPoint Energy declared dividends per share of $1.03 , $0.99 and $0.95 , respectively, during the years ended December 31, 2016 , 2015 and 2014 . Undistributed Retained Earnings As of both December 31, 2016 and 2015 , CenterPoint Energy’s consolidated retained earnings balance includes undistributed earnings from Enable of $-0- .

Short Term Borrowings and Long

Short Term Borrowings and Long Term Debt	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Short-term Borrowings and Long-term Debt [Text Block]	Short-term Borrowings and Long-term Debt December 31, December 31, Long-Term Current (1) Long-Term (2) Current (1) (in millions) Short-term borrowings: Inventory financing (3) $ — $ 35 $ — $ 40 Total short-term borrowings — 35 — 40 Long-term debt: CenterPoint Energy: ZENS due 2029 (4) — 114 — 145 Senior notes 5.95% due 2017 — 250 550 — Pollution control bonds 5.05% to 5.125% due 2018 to 2028 (5) 118 — 118 — Commercial paper (6) 835 — 716 — Other — — — 3 Houston Electric: Bank Loans — — 200 — First mortgage bonds 9.15% due 2021 102 — 102 — General mortgage bonds 1.85% to 6.95% due 2021 to 2044 2,512 — 1,912 — System restoration bonds 3.46% to 4.243% due 2018 to 2022 312 53 365 50 Transition bonds 0.901% to 5.302% due 2017 to 2024 1,560 358 1,918 341 CERC Corp.: Senior notes 4.50% to 6.625% due 2017 to 2041 1,593 250 1,843 325 Commercial paper (6) 569 — 219 — Unamortized debt issuance costs (33 ) — (35 ) — Unamortized discount and premium, net (36 ) — (42 ) — Total long-term debt 7,532 1,025 7,866 864 Total debt $ 7,532 $ 1,060 $ 7,866 $ 904 (1) Includes amounts due or exchangeable within one year of the date noted. (2) Includes $35 million of unamortized debt issuance costs to reflect adoption of ASU 2015-03. (3) NGD currently has AMAs associated with its utility distribution service in Arkansas, north Louisiana and Oklahoma that extend through 2020. Pursuant to the provisions of the agreements, NGD 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 an inventory financing. (4) CenterPoint Energy’s ZENS obligation is bifurcated into a debt component and an embedded derivative component. For additional information regarding ZENS, see Note 11(b). As ZENS are exchangeable for cash at any time at the option of the holders, these notes are classified as a current portion of long-term debt. (5) $118 million of these series of debt were secured by general mortgage bonds of Houston Electric as of both December 31, 2016 and 2015 . (6) Classified as long-term debt because the termination date of the facility that backstops the commercial paper is more than one year from the date noted. Long-term Debt Debt Retirements. In May 2016, CERC retired approximately $325 million aggregate principal amount of its 6.15% senior notes at their maturity. The retirement of senior notes was financed by the issuance of commercial paper. In December, 2016, CenterPoint Energy redeemed $300 million aggregate principal amount of its outstanding 6.50% senior notes due 2018 at a redemption price equal to 100% of the principal amount thereof, plus accrued and unpaid interest thereon to but excluding the redemption date, plus the make-whole premium. The make-whole premium associated with the redemption was approximately $22 million and was included in Other Income, net on the Statements of Consolidated Income. In December 2016, Houston Electric retired $56 million of collateralized pollution control bonds that had been held for remarketing. These bonds were not reflected on our consolidated financial statements because Houston Electric was both the obligor on the bonds and the current owner of the bonds. Debt Issuances. Houston Electric issued the following general mortgage bonds during 2016 and as of February 10, 2017 in 2017. Issuance Date Aggregate Principal Amount Interest Rate Maturity Date (in millions) May 2016 $ 300 1.85% 2021 August 2016 300 2.40% 2026 January 2017 300 3.00% 2027 The proceeds from the issuance of these bonds were used to repay short-term debt and for general corporate purposes. Securitization Bonds. As of December 31, 2016 , Houston Electric had special purpose subsidiaries consisting of the Bond Companies, which it consolidates. The consolidated special purpose subsidiaries are wholly-owned, bankruptcy remote entities that were formed solely for the purpose of purchasing and owning transition or system restoration property through the issuance of transition bonds or system restoration bonds and activities incidental thereto. These Securitization Bonds are payable only through the imposition and collection of “transition” or “system restoration” charges, as defined in the Texas Public Utility Regulatory Act, which are irrevocable, non-bypassable charges to provide recovery of authorized qualified costs. Houston Electric has no payment obligations in respect of the Securitization Bonds other than to remit the applicable transition or system restoration charges it collects. Each special purpose entity is the sole owner of the right to impose, collect and receive the applicable transition or system restoration charges securing the bonds issued by that entity. Creditors of CenterPoint Energy or Houston Electric have no recourse to any assets or revenues of the Bond Companies (including the transition and system restoration charges), and the holders of Securitization Bonds have no recourse to the assets or revenues of CenterPoint Energy or Houston Electric. Credit Facilities. December 31, 2016 December 31, 2015 Size of Loans Letters Commercial Size of Loans Letters Commercial (in millions) CenterPoint Energy $ 1,600 $ — $ 6 $ 835 (1) $ 1,200 $ — $ 6 $ 716 (1) Houston Electric 300 — 4 — 300 200 (2) 4 — CERC Corp. 600 — 4 569 (3) 600 — 2 219 (3) Total $ 2,500 $ — $ 14 $ 1,404 $ 2,100 $ 200 $ 12 $ 935 (1) Weighted average interest rate was approximately 1.04% and 0.79% as of December 31, 2016 and December 31, 2015 , respectively. (2) Weighted average interest rate was approximately 1.64% as of December 31, 2015 . (3) Weighted average interest rate was approximately 1.03% and 0.81% as of December 31, 2016 and December 31, 2015 , respectively. Execution Date Company Size of Facility Draw Rate of LIBOR plus (1) Financial Covenant Limit on Debt to Capital Ratio Debt to Capital Ratio as of December 31, 2016 (2) Termination Date (in millions) March 3, 2016 CenterPoint Energy $ 1,600 1.250% 65% (3) 56.0% March 3, 2021 March 3, 2016 Houston Electric 300 1.125% 65% (3) 47.4% March 3, 2021 March 3, 2016 CERC Corp. 600 1.250% 65% 35.8% March 3, 2021 (1) Based on current credit ratings. (2) As defined in the revolving credit facility agreement, excluding Securitization Bonds. (3) The financial covenant limit will temporarily increase from 65% to 70% if Houston Electric experiences damage from a natural disaster in its service territory and CenterPoint Energy certifies to the administrative agent that Houston Electric has incurred system restoration costs reasonably likely to exceed $100 million in a consecutive twelve -month period, all or part of which Houston Electric intends to seek to recover through securitization financing. Such temporary increase in the financial covenant would be in effect from the date CenterPoint Energy delivers its certification until the earliest to occur of (i) the completion of the securitization financing, (ii) the first anniversary of CenterPoint Energy’s certification or (iii) the revocation of such certification. CenterPoint Energy, Houston Electric and CERC Corp. were in compliance with all financial debt covenants as of December 31, 2016 . Maturities. Maturities of long-term debt, capital leases and sinking fund requirements, excluding the ZENS obligation, are as follows: CenterPoint Energy (1) Securitization Bonds (in millions) 2017 $ 911 $ 411 2018 784 434 2019 458 458 2020 231 231 2021 2,610 211 (1) These maturities include Securitization Bonds principal repayments on scheduled payment dates. Liens. As of December 31, 2016 , Houston Electric’s assets were subject to liens securing approximately $102 million of first mortgage bonds. Sinking or improvement fund and replacement fund requirements on the first mortgage bonds may be satisfied by certification of property additions. Sinking fund and replacement fund requirements for 2016 , 2015 and 2014 have been satisfied by certification of property additions. The replacement fund requirement to be satisfied in 2017 is approximately $240 million , and the sinking fund requirement to be satisfied in 2017 is approximately $1.6 million . CenterPoint Energy expects Houston Electric to meet these 2017 obligations by certification of property additions. As of December 31, 2016 , Houston Electric’s assets were also subject to liens securing approximately $2.6 billion of general mortgage bonds, which are junior to the liens of the first mortgage bonds.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes [Text Block]	Income Taxes The components of CenterPoint Energy’s income tax expense (benefit) were as follows: Year Ended December 31, 2016 2015 2014 (in millions) Current income tax expense (benefit): Federal $ 23 $ (37 ) $ (20 ) State 18 12 14 Total current expense (benefit) 41 (25 ) (6 ) Deferred income tax expense (benefit): Federal 185 (359 ) 273 State 28 (54 ) 7 Total deferred expense (benefit) 213 (413 ) 280 Total income tax expense (benefit) $ 254 $ (438 ) $ 274 A reconciliation of income tax expense (benefit) using the federal statutory income tax rate to the actual income tax expense and resulting effective income tax rate is as follows: Year Ended December 31, 2016 2015 2014 (in millions) Income (loss) before income taxes $ 686 $ (1,130 ) $ 885 Federal statutory income tax rate 35 % 35 % 35 % Expected federal income tax expense (benefit) 240 (396 ) 310 Increase (decrease) in tax expense resulting from: State income tax expense, net of federal income tax 27 (27 ) 16 State valuation allowance, net of federal 3 — — Tax basis balance sheet adjustments — — (29 ) Other, net (16 ) (15 ) (23 ) Total 14 (42 ) (36 ) Total income tax expense (benefit) $ 254 $ (438 ) $ 274 Effective tax rate 37 % 39 % 31 % In 2016, CenterPoint Energy recognized a $6 million deferred tax expense due to Louisiana state law change and recorded an additional $3 million valuation allowance on certain state carryforwards. In 2015, CenterPoint Energy’s effective tax rate was higher than the statutory rate primarily due to lower earnings from the impairment of CenterPoint Energy’s equity method investment in Enable. The impairment loss reduced the deferred tax liability on CenterPoint Energy’s equity method investment in Enable. In 2014, CenterPoint Energy recognized a $29 million deferred income tax benefit upon completion of its tax basis balance sheet review. The adjustment resulted in a decrease to deferred tax liabilities of $32 million , a decrease to income taxes payable of $5 million and a decrease to income tax regulatory assets of $8 million . CenterPoint Energy determined the impact of the $29 million adjustment was not material to any prior period or the year ended December 31, 2014. The tax effects of temporary differences that give rise to significant portions of deferred tax assets and liabilities were as follows: December 31, 2016 2015 (in millions) Deferred tax assets: Benefits and compensation $ 316 $ 334 Loss and credit carryforwards 79 115 AROs 77 73 Other 21 45 Valuation allowance (5 ) (2 ) Total deferred tax assets 488 565 Deferred tax liabilities: Property, plant, and equipment 2,603 2,423 Investment in unconsolidated affiliates 1,383 1,277 Regulatory assets/liabilities, net 883 1,060 Investment in marketable securities and indexed debt 772 654 Indexed debt securities derivative 4 91 Other 106 107 Total deferred tax liabilities 5,751 5,612 Net deferred tax liabilities $ 5,263 $ 5,047 Tax Attribute Carryforwards and Valuation Allowance. CenterPoint Energy has no remaining federal net operating loss carryforward or federal tax credits as of December 31, 2016. CenterPoint Energy has $962 million of state net operating loss carryforwards that expire between 2017 and 2036 , $11 million of state tax credits that do not expire and $244 million of state capital loss carryforwards that expire in 2017 . CenterPoint Energy reported a tax-effected valuation allowance of $5 million because it is more likely than not that the benefit from certain state carryforwards will not be realized. Uncertain Income Tax Positions . CenterPoint Energy reported no uncertain tax liability as of December 31, 2016, 2015 and 2014. We expect no significant change to the uncertain tax liability over the next twelve months ending December 31, 2017. Tax Audits and Settlements. Tax years through 2014 have been audited and settled with the IRS. For the 2015, 2016 and 2017 tax years, CenterPoint Energy is a participant in the IRS’s Compliance Assurance Process.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies [Text Block]	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 Energy 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 Consolidated Balance Sheets as of December 31, 2016 and 2015 as these contracts meet an exception 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 December 31, 2016 , minimum payment obligations for natural gas supply commitments are approximately: (in millions) 2017 $ 461 2018 467 2019 268 2020 125 2021 127 2022 and beyond 8 (b) AMAs NGD has had AMAs associated with its utility distribution service in Arkansas, Louisiana, Mississippi, Oklahoma and Texas. Generally, AMAs are contracts between NGD and an asset manager that are intended to transfer the working capital obligation and maximize the utilization of the assets. In these AMAs, NGD agrees to release transportation and storage capacity to other parties to manage natural gas storage, supply and delivery arrangements for NGD and to use the released capacity for other purposes when it is not needed for NGD. NGD is compensated by the asset manager through payments made over the life of the AMAs based in part on the results of the asset optimization. NGD has an obligation to purchase its winter storage requirements that have been released to the asset manager under these AMAs. NGD has received approval from the state regulatory commissions in Arkansas, Louisiana, Mississippi and Oklahoma to retain a share of the AMA proceeds. NGD currently has AMAs in Arkansas, north Louisiana and Oklahoma that extend through 2020. (c) Lease Commitments The following table sets forth information concerning CenterPoint Energy’s obligations under non-cancelable long-term operating leases as of December 31, 2016 , which primarily consist of rental agreements for building space, data processing equipment, compression equipment and rights-of-way: (in millions) 2017 $ 5 2018 4 2019 4 2020 3 2021 3 2022 and beyond 7 Total $ 26 Total lease expense for all operating leases was $10 million , $9 million and $11 million during 2016 , 2015 and 2014 , respectively. (d) Legal, Environmental and Other Matters Legal Matters Gas Market Manipulation Cases . CenterPoint Energy, Houston Electric or their predecessor, 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, 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 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. 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 Houston Electric, for certain liabilities, including their indemnification obligations regarding the gas market manipulation litigation. 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 and its affiliates have since been released or dismissed from all such cases. CES, a subsidiary of CERC Corp., was a defendant in a case now pending in federal court in Nevada alleging a conspiracy to inflate Wisconsin natural gas prices in 2000–2002. On May 24, 2016, the district court granted CES’s motion for summary judgment, dismissing CES from the case. The plaintiffs have appealed that ruling. CenterPoint Energy and CES intend to continue vigorously defending against the plaintiffs’ claims. CenterPoint Energy does not expect the ultimate outcome of this matter to have a material adverse effect on its financial condition, results of operations or cash flows. Environmental Matters MGP Sites. CERC and its predecessors operated MGPs in the past. With respect to certain Minnesota MGP sites, CERC has completed state-ordered remediation and continues state-ordered monitoring and water treatment. As of December 31, 2016 , CERC had a recorded liability of $7 million for continued monitoring and any future remediation required by regulators in Minnesota. The estimated range of possible remediation costs for the sites for which CERC believes it may have responsibility was $5 million to $30 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 depend on the number of sites to be remediated, the participation of other PRPs, if any, and the remediation methods used. In addition to the Minnesota sites, the EPA 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. CenterPoint Energy does not expect the ultimate outcome of these matters to have a material adverse effect on the financial condition, results of operations or cash flows of either CenterPoint Energy or CERC. Asbestos. Some facilities owned by CenterPoint Energy or its predecessors contain or have contained asbestos insulation and other asbestos-containing materials. CenterPoint Energy and its subsidiaries are from time to time named, along with numerous others, as defendants in lawsuits filed by a number of individuals who claim injury due to exposure to asbestos, and CenterPoint Energy anticipates that additional claims may be asserted in the future. Although their ultimate outcome cannot be predicted at this time, CenterPoint Energy 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 during its operations or on property where its predecessor companies 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 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 and reasonably estimable 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.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Earnings Per Share [Text Block]	Earnings Per Share The following table reconciles numerators and denominators of CenterPoint Energy’s basic and diluted earnings (loss) per share calculations: For the Year Ended December 31, 2016 2015 2014 (in millions, except per share and share amounts) Net income (loss) $ 432 $ (692 ) $ 611 Basic weighted average shares outstanding 430,606,000 430,180,000 429,634,000 Plus: Incremental shares from assumed conversions: Restricted stock (1) 2,997,000 — 2,034,000 Diluted weighted average shares 433,603,000 430,180,000 431,668,000 Basic earnings (loss) per share $ 1.00 $ (1.61 ) $ 1.42 Diluted earnings (loss) per share $ 1.00 $ (1.61 ) $ 1.42 (1) 2,349,000 incremental shares from assumed conversions of restricted stock have not been included in the computation of diluted earnings (loss) per share for the year ended December 31, 2015, as their inclusion would be anti-dilutive.

Unaudited Quarterly Information

Unaudited Quarterly Information	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Unaudited Quarterly Information [Text Block]	Unaudited Quarterly Information Summarized quarterly financial data is as follows: Year Ended December 31, 2016 First Quarter Second Quarter Third Quarter Fourth Quarter (in millions, except per share amounts) Revenues $ 1,984 $ 1,574 $ 1,889 $ 2,081 Operating income 250 182 284 243 Net income (loss) 154 (2 ) 179 101 Basic earnings (loss) per share (1) $ 0.36 $ (0.01 ) $ 0.42 $ 0.23 Diluted earnings (loss) per share (1) $ 0.36 $ (0.01 ) $ 0.41 $ 0.23 Year Ended December 31, 2015 First Quarter Second Third Quarter (2) Fourth Quarter (3) (in millions, except per share amounts) Revenues $ 2,433 $ 1,532 $ 1,630 $ 1,791 Operating income 256 186 265 226 Net income (loss) 131 77 (391 ) (509 ) Basic earnings (loss) per share (1) $ 0.30 $ 0.18 $ (0.91 ) $ (1.18 ) Diluted earnings (loss) per share (1) $ 0.30 $ 0.18 $ (0.91 ) $ (1.18 ) (1) Quarterly earnings (loss) per common share are based on the weighted average number of shares outstanding during the quarter, and the sum of the quarters may not equal annual earnings (loss) per common share. (2) CenterPoint Energy recognized $862 million ( $537 million after tax) in impairment charges related to Enable during the three months ended September 30, 2015. (3) CenterPoint Energy recognized $984 million ( $620 million after tax) in impairment charges related to Enable during the three months ended December 31, 2015.

Reportable Business Segments

Reportable Business Segments	12 Months Ended
	Dec. 31, 2016
Segment Reporting [Abstract]
Reportable Business Segments [Text Block]	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 other than Midstream Investments, where it uses equity in earnings. CenterPoint Energy’s reportable business segments include the following: Electric Transmission & Distribution, Natural Gas Distribution, Energy Services, Midstream Investments and Other Operations. The electric transmission and distribution function (Houston Electric) 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. Energy Services represents CenterPoint Energy’s non-rate regulated gas sales and services operations. Midstream Investments consists of CenterPoint Energy’s equity investment in Enable. Other Operations consists primarily of other corporate operations which support all of CenterPoint Energy’s business operations. Long-lived assets include net property, plant and equipment, goodwill and other intangibles and equity investments in unconsolidated subsidiaries. Intersegment sales are eliminated in consolidation. Financial data for business segments and products and services are as follows: Revenues from External Customers Intersegment Revenues Depreciation and Amortization Operating Income (Loss) Total Assets (1) Expenditures for Long-Lived Assets (in millions) As of and for the year ended December 31, 2016: Electric Transmission & Distribution $ 3,060 (2) $ — $ 838 $ 628 $ 10,211 $ 858 Natural Gas Distribution 2,380 29 242 303 6,099 510 Energy Services 2,073 26 7 20 1,102 5 Midstream Investments (3) — — — — 2,505 — Other 15 — 39 8 2,681 (4) 33 Reconciling Eliminations — (55 ) — — (769 ) — Consolidated $ 7,528 $ — $ 1,126 $ 959 $ 21,829 $ 1,406 As of and for the year ended December 31, 2015: Electric Transmission & Distribution $ 2,845 (2) $ — $ 705 $ 607 $ 10,028 $ 934 Natural Gas Distribution 2,603 29 222 273 5,657 601 Energy Services 1,924 33 5 42 857 5 Midstream Investments (3) — — — — 2,594 — Other 14 — 38 11 2,879 (4) 35 Reconciling Eliminations — (62 ) — — (725 ) — Consolidated $ 7,386 $ — $ 970 $ 933 $ 21,290 $ 1,575 As of and for the year ended December 31, 2014: Electric Transmission & Distribution $ 2,845 (2) $ — $ 768 $ 595 $ 10,041 $ 818 Natural Gas Distribution 3,271 30 201 287 5,464 525 Energy Services 3,095 84 5 52 978 3 Midstream Investments (3) — — — — 4,521 — Other 15 — 39 1 3,343 (4) 56 Reconciling Eliminations — (114 ) — — (1,197 ) — Consolidated $ 9,226 $ — $ 1,013 $ 935 $ 23,150 $ 1,402 (1) Amounts for 2015 and 2014 have been restated to reflect the adoption of ASU 2015-03. (2) Houston Electric’s transmission and distribution revenues from major customers are as follows: Year Ended December 31, 2016 2016 2015 2014 (in millions) Affiliates of NRG $ 698 $ 741 $ 735 Affiliates of Energy Future Holdings 220 220 189 (3) Midstream Investments’ equity earnings (losses) are as follows: Year Ended December 31, 2016 2016 2015 2014 (in millions) Enable (a) $ 208 $ (1,633 ) $ 303 SESH — — 5 Total $ 208 $ (1,633 ) $ 308 (a) These amounts include impairment charges totaling $1,846 million composed of CenterPoint Energy’s impairment of its equity method investment in Enable of $1,225 million and CenterPoint Energy’s share, $621 million , of impairment charges Enable recorded for goodwill and long-lived assets for the year ended December 31, 2015. This impairment is offset by $213 million of earnings for the year ended December 31, 2015. (4) Included in total assets of Other Operations as of December 31, 2016 , 2015 and 2014 , are pension and other postemployment related regulatory assets of $759 million , $814 million and $795 million , respectively. Year Ended December 31, Revenues by Products and Services: 2016 2015 2014 (in millions) Electric delivery $ 3,060 $ 2,845 $ 2,845 Retail gas sales 3,329 3,725 5,049 Wholesale gas sales 977 657 1,159 Gas transportation and processing 23 26 38 Energy products and services 139 133 135 Total $ 7,528 $ 7,386 $ 9,226

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2016
Subsequent Events [Abstract]
Subsequent Events [Text Block]	Subsequent Events On January 5, 2017 , CenterPoint Energy’s board of directors declared a regular quarterly cash dividend of $0.2675 per share of common stock payable on March 10, 2017 , to shareholders of record as of the close of business on February 16, 2017 . On January 3, 2017 , CES, an indirect, wholly-owned subsidiary of CenterPoint Energy, closed the previously announced agreement to acquire AEM for approximately $140 million , including estimated working capital of $100 million . With the addition of this business, CES now operates in a total of 33 states, including seven states where CES previously had no commercial or industrial natural gas sales customers though CES did have other operations in five of those states. CES has begun to integrate AEM into its existing business. Due to the limited amount of time since the acquisition, the initial accounting for the acquisition is incomplete, principally with regard to the valuation of derivatives, property, plant and equipment, intangible assets and goodwill. CenterPoint Energy intends to provide additional business combination disclosures, if material, in its Form 10-Q for the first quarter of 2017. On February 10, 2017 , Enable declared a quarterly cash distribution of $0.318 per unit on all of its outstanding common and subordinated units for the quarter ended December 31, 2016. Accordingly, CERC Corp. expects to receive a cash distribution of approximately $74 million from Enable in the first quarter of 2017 to be made with respect to CERC Corp.’s limited partner interest in Enable for the fourth quarter of 2016. On February 10, 2017 , Enable declared a quarterly cash distribution of $0.625 per Series A Preferred Unit for the quarter ended December 31, 2016. Accordingly, CenterPoint Energy expects to receive a cash distribution of approximately $9 million from Enable in the first quarter of 2017 to be made with respect to CenterPoint Energy’s investment in Series A Preferred Units of Enable for the fourth quarter of 2016.

Summary of Significant Accoun29

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with generally accepted accounting principles 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.
Principles of Consolidation	Principles of Consolidation The accounts of CenterPoint Energy and its wholly-owned and majority owned subsidiaries are included in the consolidated financial statements. All intercompany transactions and balances are eliminated in consolidation. CenterPoint Energy generally uses the equity method of accounting for investments in entities in which CenterPoint Energy has an ownership interest between 20% and 50% and exercises significant influence. CenterPoint Energy also uses the equity method for investments in which it has ownership percentages greater than 50%, when it exercises significant influence, does not have control and is not considered the primary beneficiary, if applicable. In 2013, CenterPoint Energy, OGE and affiliates of ArcLight, formed Enable as a private limited partnership. CenterPoint Energy has the ability to significantly influence the operating and financial policies of, but not solely control, Enable and, accordingly, recorded an equity method investment, at the historical costs of net assets contributed. Under the equity method, CenterPoint Energy adjusts its investment in Enable each period for contributions made, distributions received, CenterPoint Energy’s share of Enable’s comprehensive income and amortization of basis differences, as appropriate. 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. 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. Other investments, excluding marketable securities, are carried at cost. As of December 31, 2016 , CenterPoint Energy had VIEs consisting of the 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 related property. Creditors of CenterPoint Energy have no recourse to any assets or revenues of the 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.
Revenues	Revenues CenterPoint Energy records revenue for electricity delivery and natural gas sales and services under the accrual method and these revenues are recognized upon delivery to customers. Electricity deliveries not billed by month-end are accrued based on actual AMS data, daily supply volumes and applicable rates. Natural gas sales not billed by month-end are accrued based upon estimated purchased gas volumes, estimated lost and unaccounted for gas and currently effective tariff rates.
Long-lived Assets and Intangibles	Long-lived Assets and Intangibles CenterPoint Energy records property, plant and equipment at historical cost. CenterPoint Energy expenses repair and maintenance costs as incurred. CenterPoint Energy periodically evaluates long-lived assets, including property, plant and equipment, and specifically identifiable intangibles, when events or changes in circumstances indicate that the carrying value of these assets may not be recoverable. The determination of whether an impairment has occurred is based on an estimate of undiscounted cash flows attributable to the assets compared to the carrying value of the assets.
Regulatory Assets and Liabilities	Regulatory Assets and Liabilities CenterPoint Energy applies the guidance for accounting for regulated operations to the Electric Transmission & Distribution business segment and the Natural Gas Distribution business segment. CenterPoint Energy’s rate-regulated subsidiaries may collect revenues subject to refund pending final determination in rate proceedings. In connection with such revenues, estimated rate refund liabilities are recorded which reflect management’s current judgment of the ultimate outcomes of the proceedings. CenterPoint Energy had current regulatory assets of $70 million and $21 million as of December 31, 2016 and 2015, respectively, included in other current assets in its Consolidated Balance Sheets. CenterPoint Energy had current regulatory liabilities of $18 million and $57 million as of December 31, 2016 and 2015, respectively, included in other current liabilities in its Consolidated Balance Sheets. CenterPoint Energy’s rate-regulated businesses recognize removal costs as a component of depreciation expense in accordance with regulatory treatment. As of December 31, 2016 and 2015 , these removal costs of $1,010 million and $980 million , respectively, are classified as regulatory liabilities in CenterPoint Energy’s Consolidated Balance Sheets. In addition, a portion of the amount of removal costs that relate to AROs has been reclassified from a regulatory liability to an asset retirement liability in accordance with accounting guidance for AROs.
Depreciation and Amortization Expense	Depreciation and Amortization Expense Depreciation and amortization is computed using the straight-line method based on economic lives or regulatory-mandated recovery periods. Amortization expense includes amortization of regulatory assets and other intangibles.
Capitalization of Interest and AFUDC	Capitalization of Interest and AFUDC Interest and AFUDC are capitalized as a component of projects under construction and are amortized over the assets’ estimated useful lives once the assets are placed in service. AFUDC represents the composite interest cost of borrowed funds and a reasonable return on the equity funds used for construction for subsidiaries that apply the guidance for accounting for regulated operations. Although AFUDC increases both utility plant and earnings, it is realized in cash when the assets are included in rates. During 2016 , 2015 and 2014 , CenterPoint Energy capitalized interest and AFUDC of $8 million , $10 million and $11 million , respectively. During 2016 , 2015 and 2014 , CenterPoint Energy recorded AFUDC equity of $7 million , $12 million and $14 million , respectively, which is included in Other Income in its Statements of Consolidated Income.
Income Taxes	Income Taxes CenterPoint Energy uses the asset and liability method of accounting for deferred income taxes. Deferred income tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. A valuation allowance is established against deferred tax assets for which management believes realization is not considered to be more likely than not. CenterPoint Energy recognizes interest and penalties as a component of income tax expense. CenterPoint Energy reports the income tax provision associated with its interest in Enable in Income tax expense (benefit) in its Statements of Consolidated Income.
Accounts Receivable and Allowance for Doubtful Accounts	Accounts Receivable and Allowance for Doubtful Accounts Accounts receivable are recorded at the invoiced amount and do not bear interest. It is the policy of management to review the outstanding accounts receivable monthly, as well as the bad debt write-offs experienced in the past, and establish an allowance for doubtful accounts. Account balances are charged off against the allowance when management determines it is probable the receivable will not be recovered. The provision for doubtful accounts in CenterPoint Energy’s Statements of Consolidated Income for 2016 , 2015 and 2014 was $7 million , $19 million and $22 million , respectively.
Inventory	Inventory Inventory consists principally of materials and supplies and natural gas. Materials and supplies are valued at the lower of average cost or market. Materials and supplies are recorded to inventory when purchased and subsequently charged to expense or capitalized to plant when installed. Natural gas inventories of CenterPoint Energy’s Energy Services business segment are valued at the lower of average cost or market. Natural gas inventories of CenterPoint Energy’s Natural Gas Distribution business segment are primarily valued at weighted average cost. During 2016 , 2015 and 2014 , CenterPoint Energy recorded $1 million , $4 million and $8 million , respectively, in write-downs of natural gas inventory to the lower of average cost or market.
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, weather and interest rates on its operating results and cash flows. Such derivatives are recognized in CenterPoint Energy’s 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 normal 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 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.
Investments in Other Debt and Equity Securities	Investments in Other Debt and Equity Securities CenterPoint Energy reports securities classified as trading at estimated fair value in its Consolidated Balance Sheets, and any unrealized holding gains and losses are recorded as other income (expense) in its Statements of Consolidated Income.
Environmental Costs	Environmental Costs CenterPoint Energy expenses or capitalizes environmental expenditures, as appropriate, depending on their future economic benefit. CenterPoint Energy expenses amounts that relate to an existing condition caused by past operations that do not have future economic benefit. CenterPoint Energy records undiscounted liabilities related to these future costs when environmental assessments and/or remediation activities are probable and the costs can be reasonably estimated.
Statements of Consolidated Cash Flows	Statements of Consolidated Cash Flows For purposes of reporting cash flows, CenterPoint Energy considers cash equivalents to be short-term, highly-liquid investments with maturities of three months or less from the date of purchase. In connection with the issuance of securitization bonds, CenterPoint Energy was required to establish restricted cash accounts to collateralize the bonds that were issued in these financing transactions. These restricted cash accounts are not available for withdrawal until the maturity of the bonds and are not included in cash and cash equivalents. These restricted cash accounts of $40 million and $35 million as of December 31, 2016 and 2015 , respectively, are included in other current assets in CenterPoint Energy’s Consolidated Balance Sheets. Cash and cash equivalents included $340 million and $264 million as of December 31, 2016 and 2015 , respectively, that was held by the Bond Companies solely to support servicing the securitization bonds. CenterPoint Energy considers distributions received from equity method investments which do not exceed cumulative equity in earnings subsequent to the date of investment to be a return on investment and classifies these distributions as operating activities in the Statements of Consolidated Cash Flows. CenterPoint Energy considers distributions received from equity method investments in excess of cumulative equity in earnings subsequent to the date of investment to be a return of investment and classifies these distributions as investing activities in the Statements of Consolidated Cash Flows.
New Accounting Pronouncements	New Accounting Pronouncements In February 2015, the FASB issued ASU No. 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis (ASU 2015-02). ASU 2015 -02 changes the analysis that reporting organizations must perform to evaluate whether they should consolidate certain legal entities, such as limited partnerships. The changes include, among others, modification of the evaluation of whether limited partnerships and similar legal entities are VIEs or voting interest entities and elimination of the presumption that a general partner should consolidate a limited partnership. ASU 2015-02 does not amend the related party guidance for situations in which power is shared between two or more entities that hold interests in a VIE. CenterPoint Energy adopted ASU 2015-02 on January 1, 2016, which did not have a material impact on its financial position, results of operations, cash flows and disclosures. In April 2015, the FASB issued ASU No. 2015-03, Interest-Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Cost (ASU 2015-03) . ASU 2015-03 requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The recognition and measurement guidance for debt issuance costs are not affected by ASU 2015-03. CenterPoint Energy adopted ASU 2015-03 retrospectively on January 1, 2016, which resulted in a reduction of other long-term assets, indexed debt and total long-term debt on its Consolidated Balance Sheets. CenterPoint Energy had debt issuance costs, excluding amounts related to credit facility arrangements, of $42 million and $44 million as a reduction to long-term debt on its Consolidated Balance Sheets as of December 31, 2016 and 2015 , respectively. In May 2015, the FASB issued ASU No. 2015-07, Fair Value Measurement (Topic 820): Disclosures for Investments in Certain Entities That Calculate Net Asset Value per Share (or Its Equivalent) (ASU 2015-07). ASU 2015-07 removes the requirement to categorize within the fair value hierarchy investments for which fair values are measured at NAV using the practical expedient. Entities will be required to disclose the fair value of investments measured using the NAV practical expedient so that financial statement users can reconcile amounts reported in the fair value hierarchy table to amounts reported on the balance sheet. CenterPoint Energy retrospectively adopted ASU 2015-07 on January 1, 2016, which impacts its employee benefit plan disclosures. See Note 7 for the impacts on the employee benefit plan disclosures. This standard did not have an impact on CenterPoint Energy’s financial position, results of operations or cash flows. In September 2015, the FASB issued ASU No. 2015-16, Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments (ASU 2015-16). ASU 2015-16 eliminates the requirement for an acquirer in a business combination to account for measurement-period adjustments retrospectively. Instead, an acquirer would recognize a measurement-period adjustment during the period in which the amount of the adjustment is determined. CenterPoint Energy prospectively adopted ASU 2015-16 on January 1, 2016, which did not have an impact on its financial position, results of operations or cash flows. In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments-Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities (ASU 2016-01). ASU 2016-01 requires equity investments that do not result in consolidation and are not accounted for under the equity method to be measured at fair value and to recognize any changes in fair value in net income unless the investments qualify for the new practicability exception. It does not change the guidance for classifying and measuring investments in debt securities and loans. ASU 2016-01 also changes certain disclosure requirements and other aspects related to recognition and measurement of financial assets and financial liabilities. ASU 2016-01 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017. As of the first reporting period in which the guidance is adopted, a cumulative-effect adjustment to beginning retained earnings will be made, with two features that will be adopted prospectively. CenterPoint Energy is currently assessing the impact that this standard will have on its financial position, results of operations, cash flows and disclosures. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (ASU 2016-02). ASU 2016-02 provides a comprehensive new lease model that requires lessees to recognize assets and liabilities for most leases and would change certain aspects of lessor accounting. ASU 2016-02 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018, with early adoption permitted. A modified retrospective adoption approach is required. CenterPoint Energy is currently assessing the impact that this standard will have on its financial position, results of operations, cash flows and disclosures. In 2016, the FASB issued ASUs which amended ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) . ASU 2014-09, as amended, provides a comprehensive new revenue recognition model that requires revenue to be recognized in a manner that depicts the transfer of goods or services to a customer at an amount that reflects the consideration expected to be received in exchange for those goods or services. Early adoption is not permitted, and entities have the option of using either a full retrospective or a modified retrospective adoption approach. CenterPoint Energy is currently evaluating its revenue streams under these ASUs and has not yet identified any significant changes as the result of these new standards. A substantial amount of CenterPoint Energy’s revenues are tariff based, which we do not anticipate will be significantly impacted by these ASUs. CenterPoint Energy is considering the impacts of the new guidance on its ability to recognize revenue for certain contracts when collectability is uncertain and its accounting for contributions in aid of construction. CenterPoint Energy expects to adopt these ASUs on January 1, 2018 and is evaluating the method of adoption. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (ASU 2016-15). ASU 2016-15 provides clarifying guidance on the classification of certain cash receipts and payments in the statement of cash flows and eliminates the variation in practice related to such classifications. ASU 2016-15 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017, with early adoption permitted. A retrospective adoption approach is required. CenterPoint Energy is currently assessing the impact that this standard will have on its statement of cash flows. In November 2016, the FASB issued ASU No. 2016-18 , Statement of Cash Flows (Topic 230): Restricted Cash (ASU 2016-18). ASU 2016-18 requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, restricted cash and restricted cash equivalents. As a result, the statement of cash flows will no longer present transfers between cash and cash equivalents and restricted cash and restricted cash equivalents. When cash, cash equivalents, restricted cash and restricted cash equivalents are presented in more than one line item on the balance sheet, the new guidance requires a reconciliation of the totals in the statement of cash flows to the related captions in the balance sheet. ASU 2016-18 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017, with early adoption permitted. A retrospective adoption approach is required. CenterPoint Energy is currently assessing the impact that this standard will have on its statement of cash flows and disclosures. In January 2017, the FASB issued ASU No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business (ASU 2017-01). ASU 2017-01 revises the definition of a business. If substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or a group of similar identifiable assets, then under ASU 2017-01, the asset or group of assets is not a business. The guidance also requires a business to include at least one substantive process and narrows the definition of outputs to be more closely aligned with how outputs are described in ASC 606. ASU 2017-01 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017, with early adoption permitted in certain circumstances. A prospective adoption approach is required. ASU 2017-01 could have a potential impact on CenterPoint Energy’s accounting for future acquisitions. In January 2017, the FASB issued ASU No. 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (ASU 2017-04). ASU 2017-04 eliminates Step 2 of the goodwill impairment test, which requires a hypothetical purchase price allocation. A goodwill impairment will now be the amount by which a reporting unit’s carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. ASU 2017-04 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019, with early adoption permitted. A prospective adoption approach is required. ASU 2017-04 will have an impact on CenterPoint Energy’s future calculation of goodwill impairments if an impairment is identified. 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.

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Schedule of Property, Plant and Equipment [Table Text Block]	Property, plant and equipment includes the following: Weighted Average Useful Lives December 31, (in years) 2016 2015 (in millions) Electric Transmission & Distribution 32 $ 10,840 $ 10,142 Natural Gas Distribution 32 6,219 5,762 Energy Services 25 83 86 Other property 25 689 660 Total 17,831 16,650 Accumulated depreciation and amortization: Electric Transmission & Distribution 3,443 3,209 Natural Gas Distribution 1,722 1,575 Energy Services 29 34 Other property 330 295 Total accumulated depreciation and amortization 5,524 5,113 Property, plant and equipment, net $ 12,307 $ 11,537
Depreciation and Amortization [Table Text Block]	The following table presents depreciation and amortization expense for 2016 , 2015 and 2014 . 2016 2015 2014 (in millions) Depreciation expense $ 607 $ 557 $ 521 Amortization expense 519 413 492 Total depreciation and amortization expense $ 1,126 $ 970 $ 1,013
Asset Retirement Obligation [Table Text Block]	A reconciliation of the changes in the ARO liability is as follows: December 31, 2016 2015 (in millions) Beginning balance $ 195 $ 176 Accretion expense 10 6 Revisions in estimates of cash flows — 13 Ending balance $ 205 $ 195

Acquisition (Tables)

Acquisition (Tables)	12 Months Ended
	Dec. 31, 2016
Business Combinations [Abstract]
Schedule of Business Acquisitions, by Acquisition [Table Text Block]	The following table summarizes the final purchase price allocation and the fair value amounts recognized for the assets acquired and liabilities assumed related to the acquisition: (in millions) Total purchase price consideration $ 102 Receivables $ 76 Derivative assets 38 Property and equipment 1 Identifiable intangibles 38 Total assets acquired 153 Accounts payable 49 Derivative liabilities 24 Total liabilities assumed 73 Identifiable net assets acquired 80 Goodwill 22 Net assets acquired $ 102
Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination [Table Text Block]	The estimated fair value of the identifiable intangible assets and related useful lives as included in the final purchase price allocation include: Estimate Fair Value Estimate Useful Life (in millions) (in years) Customer relationships $ 34 15 Covenants not to compete 4 4 Total identifiable intangibles $ 38

Goodwill (Tables)

Goodwill (Tables)	12 Months Ended
	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill by Reportable Segments [Table Text Block]	Goodwill by reportable business segment as of December 31, 2015 and changes in the carrying amount of goodwill as of December 31, 2016 are as follows: December 31, 2015 Continuum Acquisition (1) December 31, (in millions) Natural Gas Distribution $ 746 $ — $ 746 Energy Services 83 (2) 22 105 (2) Other Operations 11 — 11 Total $ 840 $ 22 $ 862 (1) See Note 4 . (2) Amount presented is net of the accumulated goodwill impairment charge of $252 million .

Regulatory Accounting (Tables)

Regulatory Accounting (Tables)	12 Months Ended
	Dec. 31, 2016
Regulated Operations [Abstract]
Schedule of Regulatory Assets and Liabilities [Table Text Block]	The following is a list of regulatory assets/liabilities reflected on CenterPoint Energy’s Consolidated Balance Sheets as of December 31, 2016 and 2015 : December 31, 2016 2015 (in millions) Securitized regulatory assets $ 1,919 $ 2,373 Unrecognized equity return (1) (329 ) (393 ) Unamortized loss on reacquired debt 84 93 Pension and postretirement-related regulatory asset (2) 809 872 Other long-term regulatory assets (3) 194 184 Total regulatory assets 2,677 3,129 Estimated removal costs 1,010 980 Other long-term regulatory liabilities 288 296 Total regulatory liabilities 1,298 1,276 Total regulatory assets and liabilities, net $ 1,379 $ 1,853 (1) The unrecognized allowed equity return will be recognized as it is recovered in rates through 2024. During the years ended December 31, 2016 , 2015 and 2014 , Houston Electric recognized approximately $64 million , $49 million and $68 million , respectively, of the allowed equity return. The timing of CenterPoint Energy’s recognition of the allowed equity return will vary each period based on amounts actually collected during the period. The actual amounts recovered for the allowed equity return are reviewed and adjusted at least annually by the PUCT to correct any over-collections or under-collections during the preceding 12 months and to provide for the full and timely recovery of the allowed equity return. (2) NGD’s actuarially determined pension and other postemployment expense in excess of the amount being recovered through rates is being deferred for rate making purposes. Deferred pension and other postemployment expenses of $6 million and $5 million as of December 31, 2016 and 2015, respectively, were not earning a return. (3) Other regulatory assets that are not earning a return were not material as of December 31, 2016 and 2015 .

Stock-Based Incentive Compens34

Stock-Based Incentive Compensation Plans and Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2016
Disclosure of Stock-Based Incentive Compensation Plans and Employee Benefit Plans [Abstract]
Schedule of Nonvested Performance-based Units Activity [Table Text Block]	Performance Awards Outstanding and Non-Vested Shares Year Ended December 31, 2016 Shares (Thousands) Weighted-Average Grant Date Fair Value Remaining Average Contractual Life (Years) Aggregate Intrinsic Value (Millions) Outstanding as of December 31, 2015 2,628 $ 21.95 Granted 1,525 18.98 Forfeited or canceled (404 ) 20.68 Vested and released to participants (326 ) 20.68 Outstanding as of December 31, 2016 3,423 20.90 1.2 $ 43
Schedule of Nonvested Share Activity [Table Text Block]	Stock Awards Outstanding and Non-Vested Shares Year Ended December 31, 2016 Shares (Thousands) Weighted-Average Grant Date Fair Value Remaining Average Contractual Life (Years) Aggregate Intrinsic Value (Millions) Outstanding as of December 31, 2015 747 $ 21.86 Granted 464 19.24 Forfeited or canceled (19 ) 20.53 Vested and released to participants (272 ) 21.26 Outstanding as of December 31, 2016 920 20.74 1.3 $ 23
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value [Table Text Block]	The weighted-average grant-date fair values per unit of awards granted were as follows for 2016 , 2015 and 2014 : Year Ended December 31, 2016 2015 2014 Performance awards $ 18.98 $ 21.28 $ 23.70 Stock awards 19.24 21.39 23.89
Schedule of Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Grant Date Intrinsic Value [Table Text Block]	Valuation Data The total intrinsic value of awards received by participants was as follows for 2016 , 2015 and 2014 : Year Ended December 31, 2016 2015 2014 (in millions) Stock options exercised $ — $ — $ 2 Performance awards 7 9 24 Stock awards 6 7 10
Schedule of Net Benefit Costs [Table Text Block]	CenterPoint Energy’s net periodic cost includes the following components relating to pension, including the benefit restoration plan, and postretirement benefits: Year Ended December 31, 2016 2015 2014 Pension Post-retirement Pension Benefits Post-retirement Benefits Pension Benefits Post-retirement Benefits (in millions) Service cost $ 38 $ 2 $ 41 $ 2 $ 42 $ 2 Interest cost 93 16 93 20 100 22 Expected return on plan assets (101 ) (6 ) (120 ) (7 ) (125 ) (7 ) Amortization of prior service cost (credit) 9 (3 ) 9 (1 ) 10 (1 ) Amortization of net loss 63 1 57 5 44 1 Amortization of transition obligation — — — — — 5 Curtailment (1) — (5 ) — — 6 — Settlement (2) — — 10 — — — Net periodic cost $ 102 $ 5 $ 90 $ 19 $ 77 $ 22 (1) A curtailment gain or loss is required when the expected future services of a significant number of current employees are reduced or eliminated for the accrual of benefits. During the fourth quarter of 2014, CenterPoint Energy recognized a curtailment pension loss of $6 million related to employees seconded to Enable. Substantially all of the seconded employees became employees of Enable effective January 1, 2015. Also, postretirement healthcare benefits were amended during 2016 resulting in a net curtailment gain of $5 million . In May 2016, Houston Electric entered into a renegotiated collective bargaining agreement with the IBEW Local Union 66 that provides that for Houston Electric union employees covered under the agreement who retire on or after January 1, 2017, retiree medical and prescription drug coverage will be provided exclusively through the NECA/IBEW Family Medical Care Plan in exchange for the payment of monthly premiums as determined under the agreement. As a result, the accrued postretirement benefits related to such future Houston Electric union retirees were eliminated. Houston Electric recognized a curtailment gain of $3 million as an accelerated recognition of the prior service credit that would otherwise be recognized in future periods for the post-retirement plan. CenterPoint Energy also recognized an additional curtailment gain of $2 million in October 2016 related to other amendments in the post-retirement plan. As a result of these amendments, the 2016 post-retirement expense was significantly lower than expenses reported for previous years. (2) A one-time, non-cash settlement charge is required when lump sum distributions or other settlements of plan benefit obligations during a plan year exceed the service cost and interest cost components of net periodic cost for that year. Due to the amount of lump sum payment distributions from the non-qualified pension plan during the year ended December 31, 2015, CenterPoint Energy recognized a non-cash settlement charge of $10 million . This charge is an acceleration of costs that would otherwise be recognized in future periods.
Schedule of Assumptions Used [Table Text Block]	CenterPoint Energy used the following assumptions to determine net periodic cost relating to pension and postretirement benefits: Year Ended December 31, 2016 2015 2014 Pension Post-retirement Pension Benefits Post-retirement Benefits Pension Post-retirement Discount rate 4.40 % 4.35 % 4.05 % 3.90 % 4.80 % 4.75 % Expected return on plan assets 6.25 4.80 6.50 5.20 7.00 5.50 Rate of increase in compensation levels 4.15 — 4.00 — 3.90 —
Schedule of Net Pension and Post-retirement Benefit Costs [Table Text Block]	The following table summarizes changes in the benefit obligation, plan assets, the amounts recognized in consolidated balance sheets and the key assumptions of CenterPoint Energy’s pension, including benefit restoration, and postretirement plans. The measurement dates for plan assets and obligations were December 31, 2016 and 2015 . December 31, 2016 2015 Pension Post-retirement Pension Benefits Post-retirement Benefits (in millions, except for actuarial assumptions) Change in Benefit Obligation Benefit obligation, beginning of year $ 2,193 $ 432 $ 2,403 $ 529 Service cost 38 2 41 2 Interest cost 93 16 93 20 Participant contributions — 10 — 8 Benefits paid (181 ) (37 ) (234 ) (32 ) Actuarial (gain) loss 54 13 (115 ) (87 ) Medicare reimbursement — 3 — 2 Plan amendment (1) — (56 ) — (10 ) Settlement — — 5 — Benefit obligation, end of year 2,197 383 2,193 432 Change in Plan Assets Fair value of plan assets, beginning of year 1,679 136 1,925 141 Employer contributions 9 18 66 18 Participant contributions — 10 — 8 Benefits paid (181 ) (37 ) (234 ) (32 ) Plan amendment (2) — (20 ) — — Actual investment return (loss) 149 6 (78 ) 1 Fair value of plan assets, end of year 1,656 113 1,679 136 Funded status, end of year $ (541 ) $ (270 ) $ (514 ) $ (296 ) Amounts Recognized in Balance Sheets Current liabilities-other $ (7 ) $ (6 ) $ (8 ) $ (8 ) Other liabilities-benefit obligations (534 ) (264 ) (506 ) (288 ) Net liability, end of year $ (541 ) $ (270 ) $ (514 ) $ (296 ) Actuarial Assumptions Discount rate 4.15 % 4.15 % 4.40 % 4.35 % Expected return on plan assets 6.00 4.50 6.25 4.80 Rate of increase in compensation levels 4.50 — 4.15 — Healthcare cost trend rate assumed for the next year - Pre-65 — 5.75 — 6.00 Healthcare cost trend rate assumed for the next year - Post-65 — 10.65 — 5.50 Prescription drug cost trend rate assumed for the next year — 10.75 — 11.00 Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) — 4.50 — 5.00 Year that the healthcare rate reaches the ultimate trend rate — 2024 — 2024 Year that the prescription drug rate reaches the ultimate trend rate — 2024 — 2024 (1) The Postretirement plan was amended during 2016 to change retiree medical coverage, effective January 1, 2017, as follows: (i) members of the IBEW Local Union 66 who retire on or after January 1, 2017, and their dependents, will receive any retiree medical and prescription drug coverage exclusively through the NECA/IBEW Family Medical Care Plan pursuant to the terms of the renegotiated collective bargaining agreement entered into in May 2016; and (ii) Medicare eligible post-65 retirees will receive coverage through a Medicare Advantage Program, an insured benefit, in lieu of the previous self-insured benefit. These changes resulted in a reduction in our Postretirement Plan liability of $56 million as of December 31, 2016. (2) In May 2016, Houston Electric entered into a renegotiated collective bargaining agreement with the IBEW Local Union 66 and amended the Houston Electric Union Postretirement Trust. The amendment resulted in a split of the trust into two segregated and restricted accounts, one holds assets for the benefit of current, retired on or before December 31, 2016, union retirees and one holds assets for the benefit of post-2016 union retirees who are now covered exclusively by the NECA/IBEW Family Medical Care Plan. Accordingly, $20 million was transferred to the account for post-2016 union retirees.
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	CenterPoint Energy’s changes in accumulated comprehensive loss related to defined benefit, postretirement and other postemployment plans are as follows: Year Ended December 31, 2016 2015 (in millions) Beginning Balance $ (65 ) $ (85 ) Other comprehensive income (loss) before reclassifications (1) (19 ) 21 Amounts reclassified from accumulated other comprehensive income: Prior service cost (2) — 1 Actuarial losses (2) 8 10 Total reclassifications from accumulated other comprehensive income 8 11 Tax benefit (expense) 4 (12 ) Net current period other comprehensive income (loss) (7 ) 20 Ending Balance $ (72 ) $ (65 ) (1) Total other comprehensive income (loss) related to the remeasurement of pension, postretirement and other postemployment plans. (2) These accumulated other comprehensive components are included in the computation of net periodic cost. Amounts recognized in accumulated other comprehensive loss consist of the following: December 31, 2016 2015 Pension Benefits Postretirement Benefits Pension Benefits Postretirement Benefits (in millions) Unrecognized actuarial loss (gain) $ 100 $ 3 $ 106 $ (2 ) Unrecognized prior service cost (credit) 2 6 3 (1 ) Net amount recognized in accumulated other comprehensive loss $ 102 $ 9 $ 109 $ (3 )
Schedule of Defined Benefit Plan Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block]	The changes in plan assets and benefit obligations recognized in other comprehensive income during 2016 are as follows: Pension Benefits Postretirement Benefits (in millions) Net loss $ 2 $ 11 Amortization of net loss (8 ) — Amortization of prior service credit (cost) (1 ) 1 Total recognized in comprehensive income $ (7 ) $ 12
Schedule of Amounts in Accumulated Other Comprehensive Income (Loss) to be Recognized over Next Fiscal Year [Table Text Block]	The amounts in accumulated other comprehensive loss expected to be recognized as components of net periodic benefit cost during 2017 are as follows: Pension Benefits Postretirement Benefits (in millions) Unrecognized actuarial loss $ 6 $ — Unrecognized prior service cost 1 1 Amounts in accumulated comprehensive loss to be recognized in net periodic cost in 2017 $ 7 $ 1
Schedule of Accumulated Benefit Obligations in Excess of Fair Value of Plan Assets [Table Text Block]	The following table displays pension benefits related to CenterPoint Energy’s pension plans that have accumulated benefit obligations in excess of plan assets: December 31, 2016 2015 Pension Qualified Pension Non-qualified Pension Qualified Pension Non-qualified (in millions) Accumulated benefit obligation $ 2,097 $ 71 $ 2,082 $ 75 Projected benefit obligation 2,126 71 2,118 75 Fair value of plan assets 1,656 — 1,679 —
Schedule of a One-percent Point Change in the Assumed Health Care Cost Trend Rates [Table Text Block]	Assumed healthcare cost trend rates have a significant effect on the reported amounts for CenterPoint Energy’s postretirement benefit plans. A 1% change in the assumed healthcare cost trend rate would have the following effects: 1% Increase 1% Decrease (in millions) Effect on the postretirement benefit obligation $ 16 $ 15 Effect on total of service and interest cost 1 1
Target Allocation of Plan Assets [Table Text Block]	As part of the investment strategy discussed above, CenterPoint Energy maintained the following weighted average allocation targets for its benefit plans as of December 31, 2016 : Pension Benefits Postretirement Benefits U.S. equity 12 – 28% 13 – 23% International developed market equity 7 – 17% 3 – 13% Emerging market equity 3 – 13% — Fixed income 54 – 66% 69 – 79% Cash 0 – 2% 0 – 2%
Schedule of Allocation of Plan Assets [Table Text Block]	The following tables set forth by level, within the fair value hierarchy (see Note 9 ), CenterPoint Energy’s pension plan assets at fair value as of December 31, 2016 and 2015 : Fair Value Measurements as of December 31, 2016 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Cash $ 14 $ — $ — $ 14 Corporate bonds: Investment grade or above — 401 — 401 Equity securities: U.S. companies 73 — — 73 Cash received as collateral from securities lending 69 — — 69 U.S. treasuries 49 — — 49 Mortgage backed securities — 3 — 3 Asset backed securities — 2 — 2 Municipal bonds — 52 — 52 Mutual funds (1) 171 — — 171 International government bonds — 16 — 16 Obligation to return cash received as collateral from securities lending (69 ) — — (69 ) Total investments at fair value $ 307 $ 474 $ — $ 781 Investments measured by net asset value per share or its equivalent (2) 875 Total Investments $ 1,656 (1) 57% of the amount invested in mutual funds was in international equities, 28% was in emerging market equities and 15% was in U.S. equities. (2) This represents the common collective trust funds with 53% of the amount invested in fixed income securities, 12% in U.S. equities, 30% in international equities and 5% in emerging market equities. Fair Value Measurements as of December 31, 2015 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Cash $ 11 $ — $ — $ 11 Corporate bonds: Investment grade or above — 385 — 385 Equity securities: International companies 38 — — 38 U.S. companies 74 — — 74 Cash received as collateral from securities lending 71 — — 71 U.S. treasuries 57 — — 57 Mortgage backed securities — 4 — 4 Asset backed securities — 3 — 3 Municipal bonds — 66 — 66 Mutual funds (1) 144 — — 144 International government bonds — 1 — 1 Obligation to return cash received as collateral from securities lending (71 ) — — (71 ) Total investments at fair value $ 324 $ 459 $ — $ 783 Investments measured by net asset value per share or its equivalent (2) 896 Total investments $ 1,679 (1) 58% of the amount invested in mutual funds was in international equities, 28% was in emerging market equities and 14% was in U.S. equities. (2) This represents the common collective trust funds with 60% of the amount invested in fixed income securities, 11% in U.S. equities, 23% in international equities and 2% in emerging market equities. The pension plan utilized both exchange traded and over-the-counter financial instruments such as futures, interest rate options and swaps that were marked to market daily with the gains/losses settled in the cash accounts. The pension plan did not include any holdings of CenterPoint Energy common stock as of December 31, 2016 or 2015 . The changes in the fair value of the pension plan’s level 3 investments for the years ended December 31, 2016 and 2015 were not material. The following tables present by level, within the fair value hierarchy, CenterPoint Energy’s postretirement plan assets at fair value as of December 31, 2016 and 2015 , by asset category: Fair Value Measurements as of December 31, 2016 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Mutual funds (1) $ 113 $ — $ — $ 113 Total $ 113 $ — $ — $ 113 (1) 74% of the amount invested in mutual funds was in fixed income securities, 18% was in U.S. equities and 8% was in international equities. Fair Value Measurements as of December 31, 2015 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Mutual funds (1) $ 136 $ — $ — $ 136 Total $ 136 $ — $ — $ 136 (1) 72% of the amount invested in mutual funds was in fixed income securities, 20% was in U.S. equities and 8% was in international equities.
Schedule of Expected Benefit Payments [Table Text Block]	The following benefit payments are expected to be paid by the pension and postretirement benefit plans: Pension Benefits Postretirement Benefit Payments (in millions) 2017 $ 140 $ 19 2018 146 20 2019 152 23 2020 155 25 2021 159 28 2022-2026 802 152

Derivative Instruments (Tables)

Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Fair Value of Derivative Instruments [Table Text Block]	Fair Value of Derivative Instruments December 31, 2015 Total derivatives not designated as hedging instruments Balance Sheet Location Derivative Assets Fair Value Derivative Liabilities Fair Value (in millions) Natural gas derivatives (1) (2) (3) Current Assets: Non-trading derivative assets $ 90 $ 2 Natural gas derivatives (1) (2) (3) Other Assets: Non-trading derivative assets 36 — Natural gas derivatives (1) (2) (3) Current Liabilities: Non-trading derivative liabilities 10 60 Natural gas derivatives (1) (2) (3) Other Liabilities: Non-trading derivative liabilities 4 25 Indexed debt securities derivative Current Liabilities — 442 Total $ 140 $ 529 (1) The fair value shown for natural gas contracts is comprised of derivative gross volumes totaling 767 Bcf or a net 112 Bcf long position. Of the net long position, basis swaps constitute 133 Bcf. (2) Natural gas contracts are presented on a net basis in the 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 Consolidated Balance Sheets. The net of total non-trading derivative assets and liabilities was a $109 million asset as shown on CenterPoint Energy’s Consolidated Balance Sheets (and as detailed in the table below), and was comprised of the natural gas contracts derivative assets and liabilities separately shown above, impacted by collateral netting of $56 million . (3) Derivative Assets and Derivative Liabilities include no material amounts related to physical forward transactions with Enable. 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, 2016 and 2015 , while the last table provides a breakdown of the related income statement impacts for the years ending December 31, 2016 , 2015 and 2014. Fair Value of Derivative Instruments December 31, 2016 Total derivatives not designated as hedging instruments Balance Sheet Location Derivative Assets Fair Value Derivative Liabilities Fair Value (in millions) Natural gas derivatives (1) (2) (3) Current Assets: Non-trading derivative assets $ 79 $ 14 Natural gas derivatives (1) (2) (3) Other Assets: Non-trading derivative assets 24 5 Natural gas derivatives (1) (2) (3) Current Liabilities: Non-trading derivative liabilities 2 43 Natural gas derivatives (1) (2) (3) Other Liabilities: Non-trading derivative liabilities — 5 Indexed debt securities derivative Current Liabilities — 717 Total $ 105 $ 784 (1) The fair value shown for natural gas contracts is comprised of derivative gross volumes totaling 1,035 Bcf or a net 59 Bcf long position. Of the net long position, basis swaps constitute a net 126 Bcf long position. (2) Natural gas contracts are presented on a net basis in the Consolidated Balance Sheets as they are subject to master netting arrangements. This netting applies to all undisputed amounts due or past due and causes derivative assets (liabilities) to be ultimately presented net in a liability (asset) account within the Consolidated Balance Sheets. The net of total non-trading natural gas derivative assets and liabilities was a $24 million asset as shown on CenterPoint Energy’s Consolidated Balance Sheets (and as detailed in the table below), and was comprised of the natural gas contracts derivative assets and liabilities separately shown above, impacted by collateral netting of $14 million . (3) Derivative Assets and Derivative Liabilities include no material amounts related to physical forward transactions with Enable.
Offsetting of Natural Gas Derivative Assets and Liabilities [Table Text Block]	Offsetting of Natural Gas Derivative Assets and Liabilities December 31, 2015 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 $ 100 $ (11 ) $ 89 Other Assets: Non-trading derivative assets 40 (4 ) 36 Current Liabilities: Non-trading derivative liabilities (62 ) 51 (11 ) Other Liabilities: Non-trading derivative liabilities (25 ) 20 (5 ) Total $ 53 $ 56 $ 109 (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. Offsetting of Natural Gas Derivative Assets and Liabilities December 31, 2016 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 $ 81 $ (30 ) $ 51 Other Assets: Non-trading derivative assets 24 (5 ) 19 Current Liabilities: Non-trading derivative liabilities (57 ) 16 (41 ) Other Liabilities: Non-trading derivative liabilities (10 ) 5 (5 ) Total $ 38 $ (14 ) $ 24 (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 Text Block]	Realized and unrealized gains and losses on natural gas derivatives are recognized in the Statements of Consolidated Income as revenue for retail sales derivative contracts and as natural gas expense for financial natural gas derivatives and non-retail related physical natural gas derivatives. Realized and unrealized gains and losses on indexed debt securities are recorded as Other Income (Expense) in the Statements of Consolidated Income. Income Statement Impact of Derivative Activity Year Ended December 31, Total derivatives not designated as hedging instruments Income Statement Location 2016 2015 2014 (in millions) Natural gas derivatives Gains (Losses) in Revenue $ (18 ) $ 134 $ 35 Natural gas derivatives Gains (Losses) in Expense: Natural Gas 70 (105 ) 11 Indexed debt securities derivative Gains (Losses) in Other Income (Expense) (413 ) 74 (86 ) Total $ (361 ) $ 103 $ (40 )
Credit Quality of Counterparties [Table Text Block]	In addition to the risk associated with price movements, credit risk is also inherent in CenterPoint Energy’s non-trading derivative activities. Credit risk relates to the risk of loss resulting from non-performance of contractual obligations by a counterparty. The following table shows the composition of counterparties to the non-trading derivative assets of CenterPoint Energy as of December 31, 2016 and 2015 : December 31, 2016 December 31, 2015 Investment Grade(1) Total Investment Grade(1) Total (in millions) Energy marketers $ 1 $ 4 $ 4 $ 10 Financial institutions 33 33 — — End users (2) 2 47 2 115 Total $ 36 $ 84 (3) $ 6 $ 125 (1) “Investment grade” is primarily determined using publicly available credit ratings and considers credit support (including parent company guarantees) and collateral (including cash and standby letters of credit). For unrated counterparties, CenterPoint Energy determines a synthetic credit rating by performing financial statement analysis and considers contractual rights and restrictions and collateral. (2) End users are comprised primarily of customers who have contracted to fix the price of a portion of their physical gas requirements for future periods. (3) The net of total non-trading natural gas derivative assets was $70 million and $125 million as of December 31, 2016 and 2015, respectively, as shown on CenterPoint Energy’s Consolidated Balance Sheets, and was comprised of the natural gas contracts derivatives assets separately shown above, impacted by collateral netting of $14 million and $-0- as of December 31, 2016 and 2015, respectively.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Fair Value, Assets Measured on a Recurring Basis [Table Text Block]	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, and indicate the fair value hierarchy of the valuation techniques utilized by CenterPoint Energy to determine such fair value. December 31, 2016 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Netting Adjustments (1) Balance (in millions) Assets Corporate equities $ 956 $ — $ — $ — $ 956 Investments, including money market funds (2) 77 — — — 77 Natural gas derivatives (3) 11 74 20 (35 ) 70 Total assets $ 1,044 $ 74 $ 20 $ (35 ) $ 1,103 Liabilities Indexed debt securities derivative $ — $ — $ 717 $ — $ 717 Natural gas derivatives (3) 4 56 7 (21 ) 46 Total liabilities $ 4 $ 56 $ 724 $ (21 ) $ 763 (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 $14 million held by CES from the same counterparties. (2) Amounts are included in Prepaid and Other Current Assets and Other Assets in the Consolidated Balance Sheets. (3) Natural gas derivatives include no material amounts related to physical forward transactions with Enable. December 31, 2015 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Netting Adjustments (1) Balance (in millions) Assets Corporate equities $ 807 $ — $ — $ — $ 807 Investments, including money market funds (2) 53 — — — 53 Natural gas derivatives (3) 4 115 21 (15 ) 125 Total assets $ 864 $ 115 $ 21 $ (15 ) $ 985 Liabilities Indexed debt securities derivative $ — $ 442 $ — $ — $ 442 Natural gas derivatives (3) 13 65 9 (71 ) 16 Total liabilities $ 13 $ 507 $ 9 $ (71 ) $ 458 (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 $56 million posted with the same counterparties. (2) Amounts are included in Prepaid and Other Current Assets and Other Assets in the Consolidated Balance Sheets. (3) Natural gas derivatives include no material amounts related to physical forward transactions with Enable.
Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs [Table Text Block]	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 Year Ended December 31, 2016 2015 2014 (in millions) Beginning balance $ 12 $ 17 $ 3 Purchases 12 — — Total gains 12 7 14 Total settlements (27 ) (12 ) 1 Transfers out of Level 3 (1 ) (1 ) — Transfers into Level 3 (1) (712 ) 1 (1 ) Ending balance (2) $ (704 ) $ 12 $ 17 The amount of total gains (losses) for the period included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date (1) $ (402 ) $ 6 $ 16 (1) During 2016, CenterPoint Energy transferred its indexed debt securities from Level 2 to Level 3 to reflect changes in the significance of the unobservable inputs used in the valuation. As of December 31, 2016, the indexed debt securities liability was $717 million . During 2016, there was a loss of $413 million on the indexed debt securities. (2) During 2016, 2015 and 2014, CenterPoint Energy did not have significant Level 3 sales.
Estimated Fair Value of Financial Instruments, Debt Instruments [Table Text Block]	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 carrying amounts of non-trading derivative assets and liabilities and CenterPoint Energy’s 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 Consolidated Balance Sheets but for which the fair value is disclosed, would be classified as Level 1 or Level 2 in the fair value hierarchy. December 31, 2016 December 31, 2015 Carrying Amount Fair Value Carrying Amount Fair Value (in millions) Financial assets: Notes receivable - affiliated companies $ — $ — $ 363 $ 356 Financial liabilities: Long-term debt $ 8,443 $ 8,846 $ 8,585 $ 9,067

Unconsolidated Affiliates (Tabl

Unconsolidated Affiliates (Tables)	12 Months Ended
	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Equity Method Investments [Table Text Block]	Transactions with Enable: Year Ended December 31, 2016 2015 2014 (in millions) Reimbursement of transition services (1) $ 7 $ 16 $ 163 Natural gas expenses, including transportation and storage costs 110 117 130 Interest income related to notes receivable from Enable 1 8 8 (1) Represents amounts billed under the Transition Agreements, including the costs of seconded employees. Actual transition services costs are recorded net of reimbursement. Year Ended December 31, 2016 2015 (in millions) Accounts receivable for amounts billed for transition services $ 1 $ 3 Interest receivable related to notes receivable from Enable — 4 Accounts payable for natural gas purchases from Enable 10 11 Investment in Unconsolidated Affiliates: As of December 31, 2016 2015 (in millions) Enable $ 2,505 $ 2,594 Equity in Earnings (Losses) of Unconsolidated Affiliates, net: Year Ended December 31, 2016 2015 2014 (in millions) Enable $ 208 $ (1,633 ) $ 303 SESH (1) — — 5 Total $ 208 $ (1,633 ) $ 308 (1) CenterPoint Energy contributed a 24.95% interest in SESH to Enable on May 30, 2014 and its remaining 0.1% interest in SESH to Enable on June 30, 2015. Limited Partner Interest in Enable: As of December 31, 2016 2015 2014 CenterPoint Energy 54.1 % (1) 55.4 % 55.4 % OGE 25.7 % 26.3 % 26.3 % (1) In November 2016, Enable closed a public offering of 10,000,000 common units. In connection with the offering, Enable and an affiliate of ArcLight sold an additional combined 1,500,000 common units to the underwriters. Enable Common and Subordinated Units Held: December 31, 2016 Common Subordinated CenterPoint Energy 94,151,707 139,704,916 OGE 42,832,291 68,150,514 Sales of more than 5% of the aggregate of the common units and subordinated units we own in Enable or sales by OGE of more than 5% of the aggregate of the common units and subordinated units it owns in Enable are subject to mutual rights of first offer and first refusal. Enable is controlled jointly by CERC Corp. and OGE, and each own 50% of the management rights in the general partner of Enable. Sale of our or OGE’s ownership interests in Enable’s general partner to a third party is subject to mutual rights of first offer and first refusal, and we are not permitted to dispose of less than all of our interest in Enable’s general partner. Summarized consolidated income (loss) information for Enable is as follows: Year Ended December 31, 2016 2015 2014 (in millions) Operating revenues $ 2,272 $ 2,418 $ 3,367 Cost of sales, excluding depreciation and amortization 1,017 1,097 1,914 Impairment of goodwill and other long-lived assets 9 1,134 8 Operating income (loss) 385 (712 ) 586 Net income (loss) attributable to Enable 290 (752 ) 530 Reconciliation of Equity in Earnings (Losses), net: CenterPoint Energy’s interest $ 160 $ (416 ) $ 298 Basis difference amortization (1) 48 8 5 Impairment of CenterPoint Energy’s equity method investment in Enable — (1,225 ) — CenterPoint Energy’s equity in earnings (losses), net (2) $ 208 $ (1,633 ) $ 303 (1) Equity in earnings of unconsolidated affiliates includes CenterPoint Energy’s share of Enable earnings adjusted for the amortization of the basis difference of CenterPoint Energy’s original investment in Enable and its underlying equity in net assets of Enable. The basis difference is being amortized over approximately 33 years, the average life of the assets to which the basis difference is attributed. (2) These amounts include impairment charges totaling $1,846 million composed of CenterPoint Energy’s impairment of its equity method investment in Enable of $1,225 million and CenterPoint Energy’s share, $621 million , of impairment charges Enable recorded for goodwill and long-lived assets for the year ended December 31, 2015. This impairment is offset by $213 million of earnings for the year ended December 31, 2015. Summarized consolidated balance sheet information for Enable is as follows: December 31, 2016 2015 (in millions) Current assets $ 396 $ 381 Non-current assets 10,816 10,845 Current liabilities 362 615 Non-current liabilities 3,056 3,080 Non-controlling interest 12 12 Preferred equity 362 — Enable partners’ capital 7,420 7,519 Reconciliation of Investment in Enable: CenterPoint Energy’s ownership interest in Enable partners’ capital $ 4,067 $ 4,163 CenterPoint Energy’s basis difference (1,562 ) (1,569 ) CenterPoint Energy’s investment in Enable $ 2,505 $ 2,594 Distributions Received from Unconsolidated Affiliates: Year Ended December 31, 2016 2015 2014 (in millions) Investment in Enable’s common and subordinated units $ 297 $ 294 $ 298 Investment in Enable’s Series A Preferred Units 22 (1 ) — — Interest in SESH (2) — — 7 Total $ 319 $ 294 $ 305 (1) Represents the period from February 18, 2016 to December 31, 2016. (2) CenterPoint Energy contributed a 24.95% interest in SESH to Enable on May 30, 2014 and its remaining 0.1% interest in SESH to Enable on June 30, 2015.

Indexed Debt Securities (ZENS38

Indexed Debt Securities (ZENS) and Securities Related to ZENS (Tables)	12 Months Ended
	Dec. 31, 2016
Indexed Debt Securities [Abstract]
Summarized Financial Information on Investment in Time Warner Securities and Indexed Debt Security Obligation [Table Text Block]	On May 26, 2015, Charter announced that it had entered into a definitive merger agreement with TWC. On September 21, 2015, Charter shareholders approved the announced transaction with TWC. Pursuant to the merger agreement, upon closing of the merger, TWC Common would be exchanged for cash and Charter Common and as a result, reference shares for the ZENS would consist of Charter Common, TW Common and Time Common. The merger closed on May 18, 2016. CenterPoint Energy received $100 and 0.4891 shares of Charter Common for each share of TWC Common held, resulting in cash proceeds of $178 million and 872,531 shares of Charter Common. In accordance with the terms of the ZENS, CenterPoint Energy remitted $178 million to ZENS holders in June 2016, which reduced contingent principal. As a result, CenterPoint Energy recorded the following: (in millions) Cash payment to ZENS holders $ 178 Indexed debt – reduction (40 ) Indexed debt securities derivative – reduction (21 ) Loss on indexed debt securities $ 117 The following table sets forth summarized financial information regarding CenterPoint Energy’s investment in TW Securities and each component of CenterPoint Energy’s ZENS obligation. TW Securities Debt Component of ZENS (1) Derivative Component of ZENS (in millions) Balance as of December 31, 2013 $ 767 $ 132 $ 455 Accretion of debt component of ZENS — 27 — 2% interest paid — (17 ) — Loss on indexed debt securities — — 86 Gain on TW Securities 163 — — Balance as of December 31, 2014 930 142 541 Accretion of debt component of ZENS — 27 — 2% interest paid — (17 ) — Sale of TW Securities (32 ) — — Distribution to ZENS holders — (7 ) (18 ) Gain on indexed debt securities — — (81 ) Loss on TW Securities (93 ) — — Balance as of December 31, 2015 805 145 442 Accretion of debt component of ZENS — 26 — 2% interest paid — (17 ) — Sale of TW securities (178 ) — — Distribution to ZENS holders — (40 ) (21 ) Loss on indexed debt securities — — 296 Gain on TW Securities 326 — — Balance as of December 31, 2016 $ 953 $ 114 $ 717 (1) To reflect adoption of ASU 2015-03, balances have been restated to include unamortized debt issuance costs of $9 million , $10 million and $11 million as of December 31, 2015, 2014 and 2013, respectively.

Short Term Borrowings and Lon39

Short Term Borrowings and Long Term Debt (Tables)	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Schedule of Short-term Borrowings and Long-term Debt [Table Text Block]	Houston Electric issued the following general mortgage bonds during 2016 and as of February 10, 2017 in 2017. Issuance Date Aggregate Principal Amount Interest Rate Maturity Date (in millions) May 2016 $ 300 1.85% 2021 August 2016 300 2.40% 2026 January 2017 300 3.00% 2027 December 31, December 31, Long-Term Current (1) Long-Term (2) Current (1) (in millions) Short-term borrowings: Inventory financing (3) $ — $ 35 $ — $ 40 Total short-term borrowings — 35 — 40 Long-term debt: CenterPoint Energy: ZENS due 2029 (4) — 114 — 145 Senior notes 5.95% due 2017 — 250 550 — Pollution control bonds 5.05% to 5.125% due 2018 to 2028 (5) 118 — 118 — Commercial paper (6) 835 — 716 — Other — — — 3 Houston Electric: Bank Loans — — 200 — First mortgage bonds 9.15% due 2021 102 — 102 — General mortgage bonds 1.85% to 6.95% due 2021 to 2044 2,512 — 1,912 — System restoration bonds 3.46% to 4.243% due 2018 to 2022 312 53 365 50 Transition bonds 0.901% to 5.302% due 2017 to 2024 1,560 358 1,918 341 CERC Corp.: Senior notes 4.50% to 6.625% due 2017 to 2041 1,593 250 1,843 325 Commercial paper (6) 569 — 219 — Unamortized debt issuance costs (33 ) — (35 ) — Unamortized discount and premium, net (36 ) — (42 ) — Total long-term debt 7,532 1,025 7,866 864 Total debt $ 7,532 $ 1,060 $ 7,866 $ 904 (1) Includes amounts due or exchangeable within one year of the date noted. (2) Includes $35 million of unamortized debt issuance costs to reflect adoption of ASU 2015-03. (3) NGD currently has AMAs associated with its utility distribution service in Arkansas, north Louisiana and Oklahoma that extend through 2020. Pursuant to the provisions of the agreements, NGD 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 an inventory financing. (4) CenterPoint Energy’s ZENS obligation is bifurcated into a debt component and an embedded derivative component. For additional information regarding ZENS, see Note 11(b). As ZENS are exchangeable for cash at any time at the option of the holders, these notes are classified as a current portion of long-term debt. (5) $118 million of these series of debt were secured by general mortgage bonds of Houston Electric as of both December 31, 2016 and 2015 . (6) Classified as long-term debt because the termination date of the facility that backstops the commercial paper is more than one year from the date noted.
Schedule of Revolving Credit Facilities and Utilization of Such Facilities [Table Text Block]	Credit Facilities. December 31, 2016 December 31, 2015 Size of Loans Letters Commercial Size of Loans Letters Commercial (in millions) CenterPoint Energy $ 1,600 $ — $ 6 $ 835 (1) $ 1,200 $ — $ 6 $ 716 (1) Houston Electric 300 — 4 — 300 200 (2) 4 — CERC Corp. 600 — 4 569 (3) 600 — 2 219 (3) Total $ 2,500 $ — $ 14 $ 1,404 $ 2,100 $ 200 $ 12 $ 935 (1) Weighted average interest rate was approximately 1.04% and 0.79% as of December 31, 2016 and December 31, 2015 , respectively. (2) Weighted average interest rate was approximately 1.64% as of December 31, 2015 . (3) Weighted average interest rate was approximately 1.03% and 0.81% as of December 31, 2016 and December 31, 2015 , respectively. Execution Date Company Size of Facility Draw Rate of LIBOR plus (1) Financial Covenant Limit on Debt to Capital Ratio Debt to Capital Ratio as of December 31, 2016 (2) Termination Date (in millions) March 3, 2016 CenterPoint Energy $ 1,600 1.250% 65% (3) 56.0% March 3, 2021 March 3, 2016 Houston Electric 300 1.125% 65% (3) 47.4% March 3, 2021 March 3, 2016 CERC Corp. 600 1.250% 65% 35.8% March 3, 2021 (1) Based on current credit ratings. (2) As defined in the revolving credit facility agreement, excluding Securitization Bonds. (3) The financial covenant limit will temporarily increase from 65% to 70% if Houston Electric experiences damage from a natural disaster in its service territory and CenterPoint Energy certifies to the administrative agent that Houston Electric has incurred system restoration costs reasonably likely to exceed $100 million in a consecutive twelve -month period, all or part of which Houston Electric intends to seek to recover through securitization financing. Such temporary increase in the financial covenant would be in effect from the date CenterPoint Energy delivers its certification until the earliest to occur of (i) the completion of the securitization financing, (ii) the first anniversary of CenterPoint Energy’s certification or (iii) the revocation of such certification.
Schedule of Maturities of Long-term Debt [Table Text Block]	Maturities of long-term debt, capital leases and sinking fund requirements, excluding the ZENS obligation, are as follows: CenterPoint Energy (1) Securitization Bonds (in millions) 2017 $ 911 $ 411 2018 784 434 2019 458 458 2020 231 231 2021 2,610 211 (1) These maturities include Securitization Bonds principal repayments on scheduled payment dates.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income Tax Expense [Table Text Block]	The components of CenterPoint Energy’s income tax expense (benefit) were as follows: Year Ended December 31, 2016 2015 2014 (in millions) Current income tax expense (benefit): Federal $ 23 $ (37 ) $ (20 ) State 18 12 14 Total current expense (benefit) 41 (25 ) (6 ) Deferred income tax expense (benefit): Federal 185 (359 ) 273 State 28 (54 ) 7 Total deferred expense (benefit) 213 (413 ) 280 Total income tax expense (benefit) $ 254 $ (438 ) $ 274
Reconciliation of Expected Federal Income Tax Expense to Actual [Table Text Block]	A reconciliation of income tax expense (benefit) using the federal statutory income tax rate to the actual income tax expense and resulting effective income tax rate is as follows: Year Ended December 31, 2016 2015 2014 (in millions) Income (loss) before income taxes $ 686 $ (1,130 ) $ 885 Federal statutory income tax rate 35 % 35 % 35 % Expected federal income tax expense (benefit) 240 (396 ) 310 Increase (decrease) in tax expense resulting from: State income tax expense, net of federal income tax 27 (27 ) 16 State valuation allowance, net of federal 3 — — Tax basis balance sheet adjustments — — (29 ) Other, net (16 ) (15 ) (23 ) Total 14 (42 ) (36 ) Total income tax expense (benefit) $ 254 $ (438 ) $ 274 Effective tax rate 37 % 39 % 31 %
Tax Assets and Liabilities [Table Text Block]	The tax effects of temporary differences that give rise to significant portions of deferred tax assets and liabilities were as follows: December 31, 2016 2015 (in millions) Deferred tax assets: Benefits and compensation $ 316 $ 334 Loss and credit carryforwards 79 115 AROs 77 73 Other 21 45 Valuation allowance (5 ) (2 ) Total deferred tax assets 488 565 Deferred tax liabilities: Property, plant, and equipment 2,603 2,423 Investment in unconsolidated affiliates 1,383 1,277 Regulatory assets/liabilities, net 883 1,060 Investment in marketable securities and indexed debt 772 654 Indexed debt securities derivative 4 91 Other 106 107 Total deferred tax liabilities 5,751 5,612 Net deferred tax liabilities $ 5,263 $ 5,047

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Long-term Purchase Commitment [Table Text Block]	Natural gas supply commitments include natural gas contracts related to CenterPoint Energy’s Natural Gas Distribution and Energy 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 Consolidated Balance Sheets as of December 31, 2016 and 2015 as these contracts meet an exception 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 December 31, 2016 , minimum payment obligations for natural gas supply commitments are approximately: (in millions) 2017 $ 461 2018 467 2019 268 2020 125 2021 127 2022 and beyond 8
Lease Commitments [Table Text Block]	The following table sets forth information concerning CenterPoint Energy’s obligations under non-cancelable long-term operating leases as of December 31, 2016 , which primarily consist of rental agreements for building space, data processing equipment, compression equipment and rights-of-way: (in millions) 2017 $ 5 2018 4 2019 4 2020 3 2021 3 2022 and beyond 7 Total $ 26

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Basic and Diluted Earnings Per Share [Table Text Block]	The following table reconciles numerators and denominators of CenterPoint Energy’s basic and diluted earnings (loss) per share calculations: For the Year Ended December 31, 2016 2015 2014 (in millions, except per share and share amounts) Net income (loss) $ 432 $ (692 ) $ 611 Basic weighted average shares outstanding 430,606,000 430,180,000 429,634,000 Plus: Incremental shares from assumed conversions: Restricted stock (1) 2,997,000 — 2,034,000 Diluted weighted average shares 433,603,000 430,180,000 431,668,000 Basic earnings (loss) per share $ 1.00 $ (1.61 ) $ 1.42 Diluted earnings (loss) per share $ 1.00 $ (1.61 ) $ 1.42 (1) 2,349,000 incremental shares from assumed conversions of restricted stock have not been included in the computation of diluted earnings (loss) per share for the year ended December 31, 2015, as their inclusion would be anti-dilutive.

Unaudited Quarterly Informati43

Unaudited Quarterly Information (Tables)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data [Table Text Block]	Summarized quarterly financial data is as follows: Year Ended December 31, 2016 First Quarter Second Quarter Third Quarter Fourth Quarter (in millions, except per share amounts) Revenues $ 1,984 $ 1,574 $ 1,889 $ 2,081 Operating income 250 182 284 243 Net income (loss) 154 (2 ) 179 101 Basic earnings (loss) per share (1) $ 0.36 $ (0.01 ) $ 0.42 $ 0.23 Diluted earnings (loss) per share (1) $ 0.36 $ (0.01 ) $ 0.41 $ 0.23 Year Ended December 31, 2015 First Quarter Second Third Quarter (2) Fourth Quarter (3) (in millions, except per share amounts) Revenues $ 2,433 $ 1,532 $ 1,630 $ 1,791 Operating income 256 186 265 226 Net income (loss) 131 77 (391 ) (509 ) Basic earnings (loss) per share (1) $ 0.30 $ 0.18 $ (0.91 ) $ (1.18 ) Diluted earnings (loss) per share (1) $ 0.30 $ 0.18 $ (0.91 ) $ (1.18 ) (1) Quarterly earnings (loss) per common share are based on the weighted average number of shares outstanding during the quarter, and the sum of the quarters may not equal annual earnings (loss) per common share. (2) CenterPoint Energy recognized $862 million ( $537 million after tax) in impairment charges related to Enable during the three months ended September 30, 2015. (3) CenterPoint Energy recognized $984 million ( $620 million after tax) in impairment charges related to Enable during the three months ended December 31, 2015.

Reportable Business Segments (T

Reportable Business Segments (Tables)	12 Months Ended
	Dec. 31, 2016
Revenue, Major Customer [Line Items]
Financial Data for Business Segments [Table Text Block]	Financial data for business segments and products and services are as follows: Revenues from External Customers Intersegment Revenues Depreciation and Amortization Operating Income (Loss) Total Assets (1) Expenditures for Long-Lived Assets (in millions) As of and for the year ended December 31, 2016: Electric Transmission & Distribution $ 3,060 (2) $ — $ 838 $ 628 $ 10,211 $ 858 Natural Gas Distribution 2,380 29 242 303 6,099 510 Energy Services 2,073 26 7 20 1,102 5 Midstream Investments (3) — — — — 2,505 — Other 15 — 39 8 2,681 (4) 33 Reconciling Eliminations — (55 ) — — (769 ) — Consolidated $ 7,528 $ — $ 1,126 $ 959 $ 21,829 $ 1,406 As of and for the year ended December 31, 2015: Electric Transmission & Distribution $ 2,845 (2) $ — $ 705 $ 607 $ 10,028 $ 934 Natural Gas Distribution 2,603 29 222 273 5,657 601 Energy Services 1,924 33 5 42 857 5 Midstream Investments (3) — — — — 2,594 — Other 14 — 38 11 2,879 (4) 35 Reconciling Eliminations — (62 ) — — (725 ) — Consolidated $ 7,386 $ — $ 970 $ 933 $ 21,290 $ 1,575 As of and for the year ended December 31, 2014: Electric Transmission & Distribution $ 2,845 (2) $ — $ 768 $ 595 $ 10,041 $ 818 Natural Gas Distribution 3,271 30 201 287 5,464 525 Energy Services 3,095 84 5 52 978 3 Midstream Investments (3) — — — — 4,521 — Other 15 — 39 1 3,343 (4) 56 Reconciling Eliminations — (114 ) — — (1,197 ) — Consolidated $ 9,226 $ — $ 1,013 $ 935 $ 23,150 $ 1,402 (1) Amounts for 2015 and 2014 have been restated to reflect the adoption of ASU 2015-03. (2) Houston Electric’s transmission and distribution revenues from major customers are as follows: Year Ended December 31, 2016 2016 2015 2014 (in millions) Affiliates of NRG $ 698 $ 741 $ 735 Affiliates of Energy Future Holdings 220 220 189 (3) Midstream Investments’ equity earnings (losses) are as follows: Year Ended December 31, 2016 2016 2015 2014 (in millions) Enable (a) $ 208 $ (1,633 ) $ 303 SESH — — 5 Total $ 208 $ (1,633 ) $ 308 (a) These amounts include impairment charges totaling $1,846 million composed of CenterPoint Energy’s impairment of its equity method investment in Enable of $1,225 million and CenterPoint Energy’s share, $621 million , of impairment charges Enable recorded for goodwill and long-lived assets for the year ended December 31, 2015. This impairment is offset by $213 million of earnings for the year ended December 31, 2015. (4) Included in total assets of Other Operations as of December 31, 2016 , 2015 and 2014 , are pension and other postemployment related regulatory assets of $759 million , $814 million and $795 million , respectively.
Revenues by Products and Services [Table Text Block]	Year Ended December 31, Revenues by Products and Services: 2016 2015 2014 (in millions) Electric delivery $ 3,060 $ 2,845 $ 2,845 Retail gas sales 3,329 3,725 5,049 Wholesale gas sales 977 657 1,159 Gas transportation and processing 23 26 38 Energy products and services 139 133 135 Total $ 7,528 $ 7,386 $ 9,226
Schedule of Revenue by Major Customers by Reporting Segments [Table Text Block]	Houston Electric’s transmission and distribution revenues from major customers are as follows: Year Ended December 31, 2016 2016 2015 2014 (in millions) Affiliates of NRG $ 698 $ 741 $ 735 Affiliates of Energy Future Holdings 220 220 189
Midstream Investments [Table Text Block]	Midstream Investments’ equity earnings (losses) are as follows: Year Ended December 31, 2016 2016 2015 2014 (in millions) Enable (a) $ 208 $ (1,633 ) $ 303 SESH — — 5 Total $ 208 $ (1,633 ) $ 308 (a) These amounts include impairment charges totaling $1,846 million composed of CenterPoint Energy’s impairment of its equity method investment in Enable of $1,225 million and CenterPoint Energy’s share, $621 million , of impairment charges Enable recorded for goodwill and long-lived assets for the year ended December 31, 2015. This impairment is offset by $213 million of earnings for the year ended December 31, 2015.

Background (Details)

Background (Details) - shares	Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014
Enable Midstream Partners [Member]
Equity Method Investment, Ownership Percentage	54.10%	[1]	55.40%	55.40%
Series A Preferred Stock [Member] | Enable Midstream Partners [Member]
Preferred Units Held	14,520,000
Natural Gas Distribution [Member]
Number of States in which Entity Operates	6
Energy Services [Member]
Number of States in which Entity Operates	31
[1]	In November 2016, Enable closed a public offering of 10,000,000 common units. In connection with the offering, Enable and an affiliate of ArcLight sold an additional combined 1,500,000 common units to the underwriters.

Summary of Significant Accoun46

Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Significant Accounting Policies [Line Items]
Regulatory liabilities, noncurrent	$ 1,298	$ 1,276
Capitalized interest costs, including AFUDC	8	10	$ 11
Provision for doubtful accounts	7	19	22
Inventory Write-down	1	4	8
Cash and cash equivalents	341	264	298	$ 208
Unamortized debt issuance expense	42	44
Variable Interest Entity, Primary Beneficiary [Member]
Significant Accounting Policies [Line Items]
Cash and cash equivalents	340	264
Other Current Liabilities [Member]
Significant Accounting Policies [Line Items]
Regulatory liabilities, current	18	57
Prepaid Expenses and Other Current Assets [Member]
Significant Accounting Policies [Line Items]
Regulatory assets, current	70	21
Restricted cash accounts	40	35
Other Income [Member]
Significant Accounting Policies [Line Items]
AFUDC equity	7	12	$ 14
Removal Costs [Member]
Significant Accounting Policies [Line Items]
Regulatory liabilities, noncurrent	$ 1,010	$ 980

Property, Plant and Equipment47

Property, Plant and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment, Net, by Type [Abstract]
Total	$ 17,831	$ 16,650
Total accumulated depreciation and amortization	5,524	5,113
Property, plant and equipment, net	12,307	11,537
Depreciation and Amortization [Abstract]
Depreciation expense	607	557	$ 521
Amortization expense	519	413	492
Total depreciation and amortization expense	1,126	970	1,013
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	195	176
Accretion expense	10	6
Revisions in estimates of cash flows	0	13
Ending balance	205	195	176
Electric Transmission & Distribution [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total	10,840	10,142
Total accumulated depreciation and amortization	3,443	3,209
Depreciation and Amortization [Abstract]
Total depreciation and amortization expense	838	705	768
Natural Gas Distribution [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total	6,219	5,762
Total accumulated depreciation and amortization	1,722	1,575
Depreciation and Amortization [Abstract]
Total depreciation and amortization expense	242	222	201
Energy Services [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total	83	86
Total accumulated depreciation and amortization	29	34
Depreciation and Amortization [Abstract]
Total depreciation and amortization expense	7	5	5
Other property [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total	689	660
Total accumulated depreciation and amortization	330	295
Depreciation and Amortization [Abstract]
Total depreciation and amortization expense	$ 39	$ 38	$ 39
Weighted Average [Member] | Electric Transmission & Distribution [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Weighted Average Useful Lives	32 years
Weighted Average [Member] | Natural Gas Distribution [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Weighted Average Useful Lives	32 years
Weighted Average [Member] | Energy Services [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Weighted Average Useful Lives	25 years
Weighted Average [Member] | Other property [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Weighted Average Useful Lives	25 years

Acquisition (Details)

Acquisition (Details) - USD ($) $ in Millions	Apr. 01, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Total purchase price consideration		$ 102	$ 0	$ 0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Total purchase price consideration		102	0	$ 0
Goodwill		862	$ 840
Continuum Energy Services [Member]
Total purchase price consideration	$ 102
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Total purchase price consideration	102
Receivables	76
Derivative assets	38
Property and equipment	1
Identifiable intangibles	38
Total assets acquired	153
Accounts payable	49
Derivative liabilities	24
Total liabilities assumed	73
Identifiable net assets acquired	80
Goodwill	22
Net assets acquired	102
Amortization of Intangible Assets		3
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual		466
Business Combination, Operating Income Of Acquiree Since Acquisition Date		$ 1
Continuum Energy Services [Member] | Customer Relationships [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Finite-lived Intangible Assets Acquired	$ 34
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	15 years
Continuum Energy Services [Member] | Noncompete Agreements [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Finite-lived Intangible Assets Acquired	$ 4
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	4 years

Goodwill (Details)

Goodwill (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Goodwill		$ 862	$ 840
Goodwill, Acquired During Period	[1]	22
Natural Gas Distribution [Member]
Goodwill [Line Items]
Goodwill		746	746
Goodwill, Acquired During Period	[1]	0
Energy Services [Member]
Goodwill [Line Items]
Goodwill	[2]	105	83
Goodwill, Acquired During Period	[1]	22
Accumulated Goodwill Impairment Charge		252	252
Other [Member]
Goodwill [Line Items]
Goodwill		11	$ 11
Goodwill, Acquired During Period	[1]	$ 0
[1]	See Note 4.
[2]	Amount presented is net of the accumulated goodwill impairment charge of $252 million

Regulatory Accounting (Details)

Regulatory Accounting (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Regulatory Assets and Liabilities [Line Items]
Securitized regulatory assets		$ 1,919	$ 2,373
Unrecognized equity return (1)	[1]	(329)	(393)
Unamortized loss on reacquired debt		84	93
Regulatory Assets		2,677	3,129
Regulatory liabilities		1,298	1,276
Total regulatory assets and liabilities, net		1,379	1,853
Removal Costs [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory liabilities		1,010	980
Other Regulatory Assets (Liabilities) [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory liabilities		288	296
Pension and Other Postretirement Plans Costs [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Assets	[2]	809	872
Other Regulatory Assets (Liabilities) [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory Assets	[3]	194	184
CenterPoint Houston [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Amount of allowed equity return on the true-up balance that was recognized in the period		64	49	$ 68
Natural Gas Distribution [Member] | Pension and Other Postretirement Plans Costs [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Remaining amounts of regulatory assets for which no return on investment during recovery period is provided		$ 6	$ 5
[1]	The unrecognized allowed equity return will be recognized as it is recovered in rates through 2024. During the years ended December 31, 2016, 2015 and 2014, Houston Electric recognized approximately $64 million, $49 million and $68 million, respectively, of the allowed equity return. The timing of CenterPoint Energy’s recognition of the allowed equity return will vary each period based on amounts actually collected during the period. The actual amounts recovered for the allowed equity return are reviewed and adjusted at least annually by the PUCT to correct any over-collections or under-collections during the preceding 12 months and to provide for the full and timely recovery of the allowed equity return.
[2]	NGD’s actuarially determined pension and other postemployment expense in excess of the amount being recovered through rates is being deferred for rate making purposes. Deferred pension and other postemployment expenses of $6 million and $5 million as of December 31, 2016 and 2015, respectively, were not earning a return.
[3]	Other regulatory assets that are not earning a return were not material as of December 31, 2016 and 2015.

Stock-Based Incentive Compens51

Stock-Based Incentive Compensation Plans and Employee Benefit Plans Stock Based Incentive Compensation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for issuance under long-term incentive plans (in shares)	14,000
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Income tax benefit recognized related to LTIPs	$ 7	$ 6	$ 7
Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount	0	0	0
Actual tax benefit realized for tax deductions related to LTIPs	5	6	13
Changes in shares outstanding under all long-term incentive plans, additional disclosures [Abstract]
Cash received from options exercised			1
valuation data [Abstract]
Total intrinsic value of stock options exercised in the period	0	0	2
Total grant date fair values of performance and stock awards which vested during the period	$ 13	$ 13	$ 21
Performance Shares [Member]
Summary of nonvested shares [Roll Forward]
Nonvested, beginning of period (in shares)	2,628
Granted (in shares)	1,525
Forfeited or cancelled (in shares)	(404)
Vested and released to participants (in shares)	(326)
Nonvested, end of period (in shares)	3,423	2,628
Weighted average grant date fair value, nonvested, beginning of period (in dollars per share)	$ 21.95
Weighted average grant date fair values of awards granted (in dollars per share)	18.98	$ 21.28	$ 23.70
Weighted average grant date fair value, forfeited or cancelled (in dollars per share)	20.68
Weighted average grant date fair value, vested and released to participants (in dollars per share)	20.68
Weighted average grant date fair value, nonvested, end of period (in dollars per share)	$ 20.90	$ 21.95
Remaining average contractual life of nonvested shares outstanding (in years)	1 year 2 months
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Nonvested	$ 43
valuation data [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested	$ 7	$ 9	$ 24
Stock Awards [Member]
Summary of nonvested shares [Roll Forward]
Nonvested, beginning of period (in shares)	747
Granted (in shares)	464
Forfeited or cancelled (in shares)	(19)
Vested and released to participants (in shares)	(272)
Nonvested, end of period (in shares)	920	747
Weighted average grant date fair value, nonvested, beginning of period (in dollars per share)	$ 21.86
Weighted average grant date fair values of awards granted (in dollars per share)	19.24	$ 21.39	$ 23.89
Weighted average grant date fair value, forfeited or cancelled (in dollars per share)	20.53
Weighted average grant date fair value, vested and released to participants (in dollars per share)	21.26
Weighted average grant date fair value, nonvested, end of period (in dollars per share)	$ 20.74	$ 21.86
Remaining average contractual life of nonvested shares outstanding (in years)	1 year 3 months
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Nonvested	$ 23
valuation data [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested	6	$ 7	$ 10
Performance and Stock Awards [Member]
valuation data [Abstract]
Unrecognized compensation cost related to non-vested performance and stock awards	$ 21
Weighted average period of recognition (in years)	1 year 8 months
Operation And Maintenance Expense Member
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
LTIP compensation expense	$ 19	$ 17	$ 18

Stock-Based Incentive Compens52

Stock-Based Incentive Compensation Plans and Employee Benefit Plans Pension and Postretirement Benefits (Details) - USD ($)		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Annualized individual discount rates based on time period, minimum				6 months
Pension and Postretirement Benefits [Abstract]
Percentage of eligible earnings used to determine retirement benefits (in hundredths)		5.00%		5.00%
Percent vested				100.00%
Pension plan minimum vesting period (in years)				3 years
Approximate amortization period of transition obligation (in years)				20 years
Change in plan assets [Rollforward]
Plan amendment (2)				$ 20,000,000
Amounts recognized in balance sheets
Other liabilities-benefit obligations		$ (913,000,000)	$ (904,000,000)	(913,000,000)	$ (904,000,000)
Plan amendment (2)				$ 20,000,000
Annualized individual discount rates based on time period, maximum				99 years
Amounts reclassified from accumulated other comprehensive income: [Abstract]
Beginning Balance				$ (65,000,000)	(85,000,000)
Other comprehensive income (loss) before reclassifications (1)	[1]			(19,000,000)	21,000,000
Amounts reclassified from accumulated other comprehensive income:
Prior service cost (2)	[2]			0	(1,000,000)
Actuarial losses (2)	[2]			8,000,000	10,000,000
Total reclassifications from accumulated other comprehensive income				8,000,000	11,000,000
Tax benefit (expense)				4,000,000	(12,000,000)	$ (5,000,000)
Net current period other comprehensive income (loss)				(7,000,000)	20,000,000	3,000,000
Ending Balance		$ (72,000,000)	$ (65,000,000)	(72,000,000)	(65,000,000)	(85,000,000)
Changes in plan assets and benefit obligations recognized in other comprehensive income
Amortization of net loss	[2]			(8,000,000)	(10,000,000)
Prior service cost (2)	[2]			0	(1,000,000)
Effect of a one-percentage point change in assumed health care cost trend rates
Effect of a one-percentage point increase on post-retirement benefit obligation				16,000,000
Effect of a one-percentage point decrease on post-retirement benefit obligation				15,000,000
Effect of a one-percentage point increase on total service and interest cost				1,000,000
Effect of a one-percentage point decrease on total service and interest cost				1,000,000
Defined Benefit Plan, Contribution by Employer, Qualified Plan				0
Postretirement Benefits [Member]
Components of net periodic costs [Abstract]
Service cost				2,000,000	2,000,000	2,000,000
Interest cost				16,000,000	20,000,000	22,000,000
Expected return on plan assets				(6,000,000)	(7,000,000)	(7,000,000)
Amortization of prior service cost (credit)				(3,000,000)	(1,000,000)	(1,000,000)
Amortization of net loss				1,000,000	5,000,000	1,000,000
Amortization of transition obligation				0	0	5,000,000
Curtailment (1)	[3]			(5,000,000)	0	0
Settlement (2)	[4]			0	0	0
Net periodic cost				$ 5,000,000	$ 19,000,000	$ 22,000,000
Assumptions used to determine net periodic benefit (income) cost
Discount rate				4.35%	3.90%	4.75%
Expected return on plan assets		4.50%	4.80%	4.80%	5.20%	5.50%
Rate of increase in compensation levels				0.00%	0.00%	0.00%
Change in benefit obligation [Roll Forward]
Benefit obligation, beginning of year				$ 432,000,000	$ 529,000,000
Service cost				2,000,000	2,000,000	$ 2,000,000
Interest cost				16,000,000	20,000,000	22,000,000
Participant contributions				10,000,000	8,000,000
Benefits paid				(37,000,000)	(32,000,000)
Actuarial (gain) loss				13,000,000	(87,000,000)
Medicare reimbursement				3,000,000	2,000,000
Plan amendment (1)	[5]			(56,000,000)	(10,000,000)
Settlement				0	0
Benefit obligation, end of year		$ 383,000,000	$ 432,000,000	383,000,000	432,000,000	529,000,000
Change in plan assets [Rollforward]
Fair value of plan assets, beginning of year				136,000,000	141,000,000
Employer contributions				18,000,000	18,000,000
Participant contributions				10,000,000	8,000,000
Benefits paid				(37,000,000)	(32,000,000)
Plan amendment (2)	[6]			(20,000,000)	0
Actual investment return (loss)				6,000,000	1,000,000
Fair value of plan assets, end of year		113,000,000	136,000,000	113,000,000	136,000,000	$ 141,000,000
Funded status of plan
Funded status, end of year		(270,000,000)	(296,000,000)	(270,000,000)	(296,000,000)
Amounts recognized in balance sheets
Current liabilities-other		(6,000,000)	(8,000,000)	(6,000,000)	(8,000,000)
Other liabilities-benefit obligations		(264,000,000)	(288,000,000)	(264,000,000)	(288,000,000)
Net liability, end of year		$ (270,000,000)	$ (296,000,000)	$ (270,000,000)	$ (296,000,000)
Discount rate		4.15%	4.35%	4.15%	4.35%
Expected return on plan assets		4.50%	4.80%	4.80%	5.20%	5.50%
Prescription drug cost trend rate assumed for the next year				10.75%	11.00%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate)				4.50%	5.00%
Plan amendment (2)	[6]			$ (20,000,000)	$ 0
Amounts reclassified from accumulated other comprehensive income:
Prior service cost (2)				1,000,000
Actuarial losses (2)				0
Amounts recognized in accumulated other comprehensive loss
Unrecognized actuarial loss (gain)		$ 3,000,000	$ (2,000,000)	3,000,000	(2,000,000)
Unrecognized prior service cost (credit)		6,000,000	(1,000,000)	6,000,000	(1,000,000)
Net amount recognized in accumulated other comprehensive loss		$ 9,000,000	$ (3,000,000)	9,000,000	(3,000,000)
Changes in plan assets and benefit obligations recognized in other comprehensive income
Net loss				11,000,000
Amortization of net loss				0
Prior service cost (2)				1,000,000
Total recognized in comprehensive income				12,000,000
Total expense recognized in net periodic cost and other comprehensive income				17,000,000
Amounts that will be amortized from accumulated other comprehensive loss in next fiscal year
Unrecognized actuarial loss				0
Unrecognized prior service cost				1,000,000
Amounts in accumulated comprehensive loss to be recognized in net periodic cost in 2017				1,000,000
Effect of a one-percentage point change in assumed health care cost trend rates
Estimated future contributions in the next fiscal year				16,000,000
Pension Plan [Member]
Components of net periodic costs [Abstract]
Service cost				38,000,000	41,000,000	$ 42,000,000
Interest cost				93,000,000	93,000,000	100,000,000
Expected return on plan assets				(101,000,000)	(120,000,000)	(125,000,000)
Amortization of prior service cost (credit)				9,000,000	9,000,000	10,000,000
Amortization of net loss				63,000,000	57,000,000	44,000,000
Amortization of transition obligation				0	0	0
Curtailment (1)	[3]			0	0	6,000,000
Settlement (2)	[4]			0	10,000,000	0
Net periodic cost				$ 102,000,000	$ 90,000,000	$ 77,000,000
Assumptions used to determine net periodic benefit (income) cost
Discount rate				4.40%	4.05%	4.80%
Expected return on plan assets		6.00%	6.25%	6.25%	6.50%	7.00%
Rate of increase in compensation levels				4.15%	4.00%	3.90%
Change in benefit obligation [Roll Forward]
Benefit obligation, beginning of year				$ 2,193,000,000	$ 2,403,000,000
Service cost				38,000,000	41,000,000	$ 42,000,000
Interest cost				93,000,000	93,000,000	100,000,000
Participant contributions				0	0
Benefits paid				(181,000,000)	(234,000,000)
Actuarial (gain) loss				54,000,000	(115,000,000)
Medicare reimbursement				0	0
Plan amendment (1)	[5]			0	0
Settlement				0	5,000,000
Benefit obligation, end of year		$ 2,197,000,000	$ 2,193,000,000	2,197,000,000	2,193,000,000	2,403,000,000
Change in plan assets [Rollforward]
Fair value of plan assets, beginning of year				1,679,000,000	1,925,000,000
Employer contributions				9,000,000	66,000,000
Participant contributions				0	0
Benefits paid				(181,000,000)	(234,000,000)
Plan amendment (2)	[6]			0	0
Actual investment return (loss)				149,000,000	(78,000,000)
Fair value of plan assets, end of year		1,656,000,000	1,679,000,000	1,656,000,000	1,679,000,000	$ 1,925,000,000
Funded status of plan
Funded status, end of year		(541,000,000)	(514,000,000)	(541,000,000)	(514,000,000)
Amounts recognized in balance sheets
Current liabilities-other		(7,000,000)	(8,000,000)	(7,000,000)	(8,000,000)
Other liabilities-benefit obligations		(534,000,000)	(506,000,000)	(534,000,000)	(506,000,000)
Net liability, end of year		$ (541,000,000)	$ (514,000,000)	$ (541,000,000)	$ (514,000,000)
Discount rate		4.15%	4.40%	4.15%	4.40%
Expected return on plan assets		6.00%	6.25%	6.25%	6.50%	7.00%
Rate of increase in compensation levels		4.50%	4.15%	4.50%	4.15%
Plan amendment (2)	[6]			$ 0	$ 0
Accumulated benefit obligation for all defined benefit pension plans		$ 2,168,000,000	$ 2,157,000,000	2,168,000,000	2,157,000,000
Amounts reclassified from accumulated other comprehensive income:
Prior service cost (2)				(1,000,000)
Actuarial losses (2)				8,000,000
Amounts recognized in accumulated other comprehensive loss
Unrecognized actuarial loss (gain)		100,000,000	106,000,000	100,000,000	106,000,000
Unrecognized prior service cost (credit)		2,000,000	3,000,000	2,000,000	3,000,000
Net amount recognized in accumulated other comprehensive loss		102,000,000	109,000,000	102,000,000	109,000,000
Changes in plan assets and benefit obligations recognized in other comprehensive income
Net loss				2,000,000
Amortization of net loss				(8,000,000)
Prior service cost (2)				(1,000,000)
Total recognized in comprehensive income				(7,000,000)
Total expense recognized in net periodic cost and other comprehensive income				95,000,000
Amounts that will be amortized from accumulated other comprehensive loss in next fiscal year
Unrecognized actuarial loss				6,000,000
Unrecognized prior service cost				1,000,000
Amounts in accumulated comprehensive loss to be recognized in net periodic cost in 2017				7,000,000
Pension benefits that have accumulated benefit obligations in excess of plan assets
Accumulated benefit obligation		2,097,000,000	2,082,000,000	2,097,000,000	2,082,000,000
Projected benefit obligation		2,126,000,000	2,118,000,000	2,126,000,000	2,118,000,000
Fair value of plan assets		$ 1,656,000,000	$ 1,679,000,000	1,656,000,000	$ 1,679,000,000
Effect of a one-percentage point change in assumed health care cost trend rates
Estimated future contributions in the next fiscal year				$ 39,000,000
Minimum [Member] | Postretirement Benefits [Member]
Amounts recognized in balance sheets
Defined Benefit Plan, Health Care Cost Trend Rate Assumed for Next Fiscal Year				5.75%	6.00%
Maximum [Member] | Postretirement Benefits [Member]
Amounts recognized in balance sheets
Defined Benefit Plan, Health Care Cost Trend Rate Assumed for Next Fiscal Year				10.65%	5.50%
CenterPoint Houston [Member] | Postretirement Benefits [Member]
Components of net periodic costs [Abstract]
Curtailment (1)				$ (3,000,000)
Parent Company [Member] | Postretirement Benefits [Member]
Components of net periodic costs [Abstract]
Curtailment (1)				$ (2,000,000)
Healthcare Sector [Member] | Postretirement Benefits [Member]
Amounts recognized in balance sheets
Defined Benefit Plan, Year that Rate Reaches Ultimate Trend Rate		2,024	2,024	2,024	2,024
Prescription Drug [Member] | Postretirement Benefits [Member]
Amounts recognized in balance sheets
Defined Benefit Plan, Year that Rate Reaches Ultimate Trend Rate		2,024	2,024	2,024	2,024
[1]	Total other comprehensive income (loss) related to the remeasurement of pension, postretirement and other postemployment plans.
[2]	These accumulated other comprehensive components are included in the computation of net periodic cost.
[3]	A curtailment gain or loss is required when the expected future services of a significant number of current employees are reduced or eliminated for the accrual of benefits. During the fourth quarter of 2014, CenterPoint Energy recognized a curtailment pension loss of $6 million related to employees seconded to Enable. Substantially all of the seconded employees became employees of Enable effective January 1, 2015. Also, postretirement healthcare benefits were amended during 2016 resulting in a net curtailment gain of $5 million. In May 2016, Houston Electric entered into a renegotiated collective bargaining agreement with the IBEW Local Union 66 that provides that for Houston Electric union employees covered under the agreement who retire on or after January 1, 2017, retiree medical and prescription drug coverage will be provided exclusively through the NECA/IBEW Family Medical Care Plan in exchange for the payment of monthly premiums as determined under the agreement. As a result, the accrued postretirement benefits related to such future Houston Electric union retirees were eliminated. Houston Electric recognized a curtailment gain of $3 million as an accelerated recognition of the prior service credit that would otherwise be recognized in future periods for the post-retirement plan. CenterPoint Energy also recognized an additional curtailment gain of $2 million in October 2016 related to other amendments in the post-retirement plan. As a result of these amendments, the 2016 post-retirement expense was significantly lower than expenses reported for previous years.
[4]	A one-time, non-cash settlement charge is required when lump sum distributions or other settlements of plan benefit obligations during a plan year exceed the service cost and interest cost components of net periodic cost for that year. Due to the amount of lump sum payment distributions from the non-qualified pension plan during the year ended December 31, 2015, CenterPoint Energy recognized a non-cash settlement charge of $10 million. This charge is an acceleration of costs that would otherwise be recognized in future periods.
[5]	The Postretirement plan was amended during 2016 to change retiree medical coverage, effective January 1, 2017, as follows: (i) members of the IBEW Local Union 66 who retire on or after January 1, 2017, and their dependents, will receive any retiree medical and prescription drug coverage exclusively through the NECA/IBEW Family Medical Care Plan pursuant to the terms of the renegotiated collective bargaining agreement entered into in May 2016; and (ii) Medicare eligible post-65 retirees will receive coverage through a Medicare Advantage Program, an insured benefit, in lieu of the previous self-insured benefit. These changes resulted in a reduction in our Postretirement Plan liability of $56 million as of December 31, 2016.
[6]	In May 2016, Houston Electric entered into a renegotiated collective bargaining agreement with the IBEW Local Union 66 and amended the Houston Electric Union Postretirement Trust. The amendment resulted in a split of the trust into two segregated and restricted accounts, one holds assets for the benefit of current, retired on or before December 31, 2016, union retirees and one holds assets for the benefit of post-2016 union retirees who are now covered exclusively by the NECA/IBEW Family Medical Care Plan. Accordingly, $20 million was transferred to the account for post-2016 union retirees.

Stock-Based Incentive Compens53

Stock-Based Incentive Compensation Plans and Employee Benefit Plans Plan Assets (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Defined Benefit Plan, Contribution by Employer, Qualified Plan	$ 0
Savings Plan [Abstract]
Maximum percentage of eligible compensation employees may contribute to the savings plan (in hundredths)	50.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	100.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	6.00%
Defined Contribution Plan, Cost Recognized	$ 38,000,000		$ 35,000,000		$ 39,000,000
Postemployment Benefits [Abstract]
Postemployment Benefits, Period Expense	5,000,000		2,000,000		3,000,000
Other Non-Qualified Plans [Abstract]
Benefit expense related to deferred compensation plans	3,000,000		3,000,000		5,000,000
Other Pension Plan [Member]
Accumulated benefit obligation	71,000,000		75,000,000
Projected benefit obligation	71,000,000		75,000,000
Fair value of plan assets	0		0
Total contributions to the plans during the period	9,000,000
Estimated future contributions in the next fiscal year	7,000,000
Pension Plan [Member]
Accumulated benefit obligation	2,097,000,000		2,082,000,000
Projected benefit obligation	2,126,000,000		2,118,000,000
Fair value of plan assets	1,656,000,000		1,679,000,000
Pension plan assets, fair value	1,656,000,000		1,679,000,000		1,925,000,000
Defined Benefits Plan, Fair Value Of Plan Assets, Excluding Investments Measured at Net Asset Value	781,000,000		783,000,000
Obligation To Return Cash Received As Collateral From Securities Lending,	(69,000,000)		(71,000,000)
Total contributions to the plans during the period	9,000,000		66,000,000
Estimated future contributions in the next fiscal year	39,000,000
Defined Benefit Plan, Estimated Future Benefit Payments [Abstract]
Pension benefit payments 2017	140,000,000
Pension benefit payments 2018	146,000,000
Pension benefit payments 2019	152,000,000
Pension benefit payments 2020	155,000,000
Pension benefit payments 2021	159,000,000
Pension benefit payments 2022 - 2026	802,000,000
Postretirement Benefits [Member]
Pension plan assets, fair value	113,000,000		136,000,000		$ 141,000,000
Total contributions to the plans during the period	18,000,000		18,000,000
Estimated future contributions in the next fiscal year	16,000,000
Defined Benefit Plan, Estimated Future Benefit Payments [Abstract]
Pension benefit payments 2017	19,000,000
Pension benefit payments 2018	20,000,000
Pension benefit payments 2019	23,000,000
Pension benefit payments 2020	25,000,000
Pension benefit payments 2021	28,000,000
Pension benefit payments 2022 - 2026	152,000,000
Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member]
Pension plan assets, fair value	307,000,000		324,000,000
Obligation To Return Cash Received As Collateral From Securities Lending,	(69,000,000)		(71,000,000)
Fair Value, Inputs, Level 1 [Member] | Postretirement Benefits [Member]
Pension plan assets, fair value	113,000,000		136,000,000
Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member]
Pension plan assets, fair value	474,000,000		459,000,000
Obligation To Return Cash Received As Collateral From Securities Lending,	0		0
Fair Value, Inputs, Level 2 [Member] | Postretirement Benefits [Member]
Pension plan assets, fair value	0		0
Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member]
Pension plan assets, fair value	0		0
Obligation To Return Cash Received As Collateral From Securities Lending,	0		0
Fair Value, Inputs, Level 3 [Member] | Postretirement Benefits [Member]
Pension plan assets, fair value	$ 0		0
U.S. Equity [Member] | Pension Plan [Member]
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum	12.00%
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum	28.00%
Pension plan assets, fair value	$ 73,000,000		74,000,000
U.S. Equity [Member] | Postretirement Benefits [Member]
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum	13.00%
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum	23.00%
U.S. Equity [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member]
Pension plan assets, fair value	$ 73,000,000		74,000,000
U.S. Equity [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member]
Pension plan assets, fair value	0		0
U.S. Equity [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member]
Pension plan assets, fair value	$ 0		0
International Developed Market Equity [Member] | Pension Plan [Member]
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum	7.00%
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum	17.00%
International Developed Market Equity [Member] | Postretirement Benefits [Member]
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum	3.00%
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum	13.00%
Emerging Market Equity [Member] | Pension Plan [Member]
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum	3.00%
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum	13.00%
Emerging Market Equity [Member] | Postretirement Benefits [Member]
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum	0.00%
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum	0.00%
Fixed Income [Member] | Pension Plan [Member]
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum	54.00%
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum	66.00%
Fixed Income [Member] | Postretirement Benefits [Member]
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum	69.00%
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum	79.00%
Cash and Cash Equivalents [Member] | Pension Plan [Member]
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum	0.00%
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum	2.00%
Pension plan assets, fair value	$ 14,000,000		11,000,000
Cash and Cash Equivalents [Member] | Postretirement Benefits [Member]
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum	0.00%
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum	2.00%
Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member]
Pension plan assets, fair value	$ 14,000,000		11,000,000
Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member]
Pension plan assets, fair value	0		0
Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member]
Pension plan assets, fair value	0		0
Common Collective Trust Funds [Member] | Pension Plan [Member]
Pension plan assets, fair value	$ 875,000,000	[1]	$ 896,000,000	[2]
Common Collective Trust Funds [Member] | International Equity [Member] | Pension Plan [Member]
Defined Benefit Plan, Actual Plan Asset Allocations	30.00%		23.00%
Common Collective Trust Funds [Member] | Fixed Income Funds [Member] | Pension Plan [Member]
Defined Benefit Plan, Actual Plan Asset Allocations	53.00%		60.00%
Common Collective Trust Funds [Member] | U.S. Equity [Member] | Pension Plan [Member]
Defined Benefit Plan, Actual Plan Asset Allocations	12.00%		11.00%
Common Collective Trust Funds [Member] | Emerging Market Equity [Member] | Pension Plan [Member]
Defined Benefit Plan, Actual Plan Asset Allocations	5.00%		2.00%
Investment grade or above [Member] | Pension Plan [Member]
Pension plan assets, fair value	$ 401,000,000		$ 385,000,000
Investment grade or above [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member]
Pension plan assets, fair value	0		0
Investment grade or above [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member]
Pension plan assets, fair value	401,000,000		385,000,000
Investment grade or above [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member]
Pension plan assets, fair value	0		0
International equities [Member] | Pension Plan [Member]
Pension plan assets, fair value			38,000,000
International equities [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member]
Pension plan assets, fair value			38,000,000
International equities [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member]
Pension plan assets, fair value			0
International equities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member]
Pension plan assets, fair value			0
Cash received as collateral from securities [Member] | Pension Plan [Member]
Pension plan assets, fair value	69,000,000		71,000,000
Cash received as collateral from securities [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member]
Pension plan assets, fair value	69,000,000		71,000,000
Cash received as collateral from securities [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member]
Pension plan assets, fair value	0		0
Cash received as collateral from securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member]
Pension plan assets, fair value	0		0
U.S. treasuries [Member] | Pension Plan [Member]
Pension plan assets, fair value	49,000,000		57,000,000
U.S. treasuries [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member]
Pension plan assets, fair value	49,000,000		57,000,000
U.S. treasuries [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member]
Pension plan assets, fair value	0		0
U.S. treasuries [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member]
Pension plan assets, fair value	0		0
Mortgage backed securities [Member] | Pension Plan [Member]
Pension plan assets, fair value	3,000,000		4,000,000
Mortgage backed securities [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member]
Pension plan assets, fair value	0		0
Mortgage backed securities [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member]
Pension plan assets, fair value	3,000,000		4,000,000
Mortgage backed securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member]
Pension plan assets, fair value	0		0
Asset backed securities [Member] | Pension Plan [Member]
Pension plan assets, fair value	2,000,000		3,000,000
Asset backed securities [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member]
Pension plan assets, fair value	0		0
Asset backed securities [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member]
Pension plan assets, fair value	2,000,000		3,000,000
Asset backed securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member]
Pension plan assets, fair value	0		0
Municipal bonds [Member] | Pension Plan [Member]
Pension plan assets, fair value	52,000,000		66,000,000
Municipal bonds [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member]
Pension plan assets, fair value	0		0
Municipal bonds [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member]
Pension plan assets, fair value	52,000,000		66,000,000
Municipal bonds [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member]
Pension plan assets, fair value	0		0
Mutual funds [Member] | Pension Plan [Member]
Pension plan assets, fair value	171,000,000	[3]	144,000,000	[4]
Mutual funds [Member] | Postretirement Benefits [Member]
Pension plan assets, fair value	$ 113,000,000	[5]	$ 136,000,000	[6]
Mutual funds [Member] | International Equity [Member] | Pension Plan [Member]
Defined Benefit Plan, Actual Plan Asset Allocations	57.00%		58.00%
Mutual funds [Member] | International Equity [Member] | Postretirement Benefits [Member]
Defined Benefit Plan, Actual Plan Asset Allocations	8.00%		8.00%
Mutual funds [Member] | Fixed Income Funds [Member] | Postretirement Benefits [Member]
Defined Benefit Plan, Actual Plan Asset Allocations	74.00%		72.00%
Mutual funds [Member] | U.S. Equity [Member] | Pension Plan [Member]
Defined Benefit Plan, Actual Plan Asset Allocations	15.00%		14.00%
Mutual funds [Member] | U.S. Equity [Member] | Postretirement Benefits [Member]
Defined Benefit Plan, Actual Plan Asset Allocations	18.00%		20.00%
Mutual funds [Member] | Emerging Market Equity [Member] | Pension Plan [Member]
Defined Benefit Plan, Actual Plan Asset Allocations	28.00%		28.00%
Mutual funds [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member]
Pension plan assets, fair value	$ 171,000,000	[3]	$ 144,000,000	[4]
Mutual funds [Member] | Fair Value, Inputs, Level 1 [Member] | Postretirement Benefits [Member]
Pension plan assets, fair value	113,000,000	[5]	136,000,000	[6]
Mutual funds [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member]
Pension plan assets, fair value	0	[3]	0	[4]
Mutual funds [Member] | Fair Value, Inputs, Level 2 [Member] | Postretirement Benefits [Member]
Pension plan assets, fair value	0	[5]	0	[6]
Mutual funds [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member]
Pension plan assets, fair value	0	[3]	0	[4]
Mutual funds [Member] | Fair Value, Inputs, Level 3 [Member] | Postretirement Benefits [Member]
Pension plan assets, fair value	0	[5]	0	[6]
International government bonds [Member] | Pension Plan [Member]
Pension plan assets, fair value	16,000,000		1,000,000
International government bonds [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member]
Pension plan assets, fair value	0		0
International government bonds [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member]
Pension plan assets, fair value	16,000,000		1,000,000
International government bonds [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member]
Pension plan assets, fair value	0		0
Benefit Obligation [Member]
Postemployment Benefits [Abstract]
Postemployment benefit obligations	22,000,000		23,000,000
Other Non-Qualified Plans [Abstract]
Other non-qualified plans benefit obligations deferred compensation	47,000,000		51,000,000
Benefit obligations related to split-dollar life insurance arrangements	$ 40,000,000		$ 32,000,000
Common Stock [Member] | CenterPoint Energy [Member]
Savings Plan [Abstract]
Defined Contribution Plan, Maximum Limit Of Account Balance In Company Stock, Percentage	25.00%
Number of Common stock held by the savings plan (in shares)	14,216,986
Percentage of investment in common stocks (in hundredths)	17.00%
[1]	This represents the common collective trust funds with 53% of the amount invested in fixed income securities, 12% in U.S. equities, 30% in international equities and 5% in emerging market equities.
[2]	This represents the common collective trust funds with 60% of the amount invested in fixed income securities, 11% in U.S. equities, 23% in international equities and 2% in emerging market equities.
[3]	57% of the amount invested in mutual funds was in international equities, 28% was in emerging market equities and 15% was in U.S. equities.
[4]	58% of the amount invested in mutual funds was in international equities, 28% was in emerging market equities and 14% was in U.S. equities.
[5]	74% of the amount invested in mutual funds was in fixed income securities, 18% was in U.S. equities and 8% was in international equities.
[6]	72% of the amount invested in mutual funds was in fixed income securities, 20% was in U.S. equities and 8% was in international equities.

Stock-Based Incentive Compens54

Stock-Based Incentive Compensation Plans and Employee Benefit Plans Change in Control Agreements and Other Employee Matters (Details)	12 Months Ended
	Dec. 31, 2016
Concentration Risk [Line Items]
Maximum Number Of Times Annual Salary Included In Severance Benefits	3
Number of Employees, Total [Member] | Employees Subject To Collective Bargaining Agreements [Member] | Labor Force Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage	35.00%
Workforce Subject to Collective Bargaining Arrangements Expiring in May 2020 and March and May 2021 [Member] | Employees Subject To Collective Bargaining Agreements [Member] | Labor Force Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage	21.00%
Workforce Subject to Collective Bargaining Arrangements Expiring in April and December 2020 [Member] | Employees Subject To Collective Bargaining Agreements [Member] | Labor Force Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage	8.00%
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member] | Employees Subject To Collective Bargaining Agreements [Member] | Labor Force Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage	6.00%

Derivative Instruments (Details

Derivative Instruments (Details) - USD ($) $ in Millions	Jan. 12, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Aug. 08, 2016	May 13, 2016
Weather Hedges [Abstract]
Weather Hedges Term		10 years
2014To2015 [Member] | Natural Gas Distribution [Member]
Weather Hedges [Abstract]
Weather Hedge, Bilateral Cap Amount			$ 16
2014To2015 [Member] | Electric Transmission & Distribution [Member]
Weather Hedges [Abstract]
Weather Hedge, Bilateral Cap Amount		$ 8
2015To2016 [Member] | Electric Transmission & Distribution [Member]
Weather Hedges [Abstract]
Weather Hedge, Bilateral Cap Amount		7
2016to2017 [Member] | Electric Transmission & Distribution [Member]
Weather Hedges [Abstract]
Weather Hedge, Bilateral Cap Amount		9
Sales [Member] | Weather Hedge Swaps [Member]
Weather Hedges [Abstract]
Derivative, Gain (Loss) on Derivative, Net		1	$ (6)	$ (11)
April [Member] | Treasury Lock [Member]
Weather Hedges [Abstract]
Derivative, Notional Amount		150
June and July [Member] | Treasury Lock [Member]
Weather Hedges [Abstract]
Derivative, Notional Amount		300
CenterPoint Houston [Member] | Bonds General Mortgage Due 2021 [Member]
Weather Hedges [Abstract]
Debt Instrument, Face Amount						$ 300
CenterPoint Houston [Member] | Bonds General Mortgage Due 2026 [Member]
Weather Hedges [Abstract]
Debt Instrument, Face Amount					$ 300
Cash Flow Hedging [Member]
Weather Hedges [Abstract]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net		$ 1.1
Subsequent Event [Member] | January [Member] | Treasury Lock [Member]
Weather Hedges [Abstract]
Derivative, Notional Amount	$ 150
Debt Instrument, Face Amount	300
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	$ (0.5)

Derivative Instruments Derivati

Derivative Instruments Derivative Fair Values (Details)		12 Months Ended
		Dec. 31, 2016USD ($)Bcf		Dec. 31, 2015USD ($)Bcf		Dec. 31, 2014USD ($)
Credit Risk Contract [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Assets (Liabilities), at Fair Value, Net		$ 70,000,000		$ 125,000,000
Derivative, Fair Value, Offsets, Net		$ (14,000,000)		$ 0
Natural gas derivative
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative, Nonmonetary Notional Amount, Volume | Bcf		1,035		767
Derivative Assets (Liabilities), at Fair Value, Net	[1]	$ 24,000,000		$ 109,000,000
Derivative, Fair Value, Net	[2]	38,000,000		53,000,000
Derivative, Fair Value, Offsets, Net		14,000,000		(56,000,000)
Natural gas derivative | Gains (Losses) in Revenue [Member]
Income Statement Impact of Derivative Activity [Abstract]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		(18,000,000)		134,000,000		$ 35,000,000
Natural gas derivative | Gains (Losses) in Expense: Natural Gas [Member]
Income Statement Impact of Derivative Activity [Abstract]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		70,000,000		(105,000,000)		11,000,000
Natural gas derivative | Current Assets [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	[2]	81,000,000		100,000,000
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		(30,000,000)		(11,000,000)
Natural gas derivatives (2)	[1]	51,000,000		89,000,000
Natural gas derivative | Other Noncurrent Assets [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	[2]	24,000,000		40,000,000
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		(5,000,000)		(4,000,000)
Natural gas derivatives (2)	[1]	19,000,000		36,000,000
Natural gas derivative | Current Liabilities [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	[2]	(57,000,000)		(62,000,000)
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		16,000,000		51,000,000
Derivative Liability	[1]	(41,000,000)		(11,000,000)
Natural gas derivative | Other Noncurrent Liabilities [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	[2]	(10,000,000)		(25,000,000)
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		5,000,000		20,000,000
Derivative Liability	[1]	(5,000,000)		(5,000,000)
Natural gas derivative | Derivatives Not Designated as Hedging Instruments [Member] | Current Assets [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Asset, Fair Value, Gross Asset	[3]	79,000,000	[4],[5]	90,000,000	[6],[7]
Derivative Liability, Fair Value, Gross Liability	[3]	14,000,000	[4],[5]	2,000,000	[6],[7]
Natural gas derivative | Derivatives Not Designated as Hedging Instruments [Member] | Other Noncurrent Assets [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Asset, Fair Value, Gross Asset	[3]	24,000,000	[4],[5]	36,000,000	[6],[7]
Derivative Liability, Fair Value, Gross Liability	[3]	5,000,000	[4],[5]	0	[6],[7]
Natural gas derivative | Derivatives Not Designated as Hedging Instruments [Member] | Current Liabilities [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Asset, Fair Value, Gross Asset	[3]	2,000,000	[4],[5]	10,000,000	[6],[7]
Derivative Liability, Fair Value, Gross Liability	[3]	43,000,000	[4],[5]	60,000,000	[6],[7]
Natural gas derivative | Derivatives Not Designated as Hedging Instruments [Member] | Other Noncurrent Liabilities [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Asset, Fair Value, Gross Asset	[3]	0	[4],[5]	4,000,000	[6],[7]
Derivative Liability, Fair Value, Gross Liability	[3]	$ 5,000,000	[4],[5]	$ 25,000,000	[6],[7]
Natural gas derivative | Long [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative, Nonmonetary Notional Amount, Volume | Bcf		59		112
indexed debt securities derivative | Nonoperating Income (Expense) [Member]
Income Statement Impact of Derivative Activity [Abstract]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		$ (413,000,000)		$ 74,000,000		(86,000,000)
indexed debt securities derivative | Derivatives Not Designated as Hedging Instruments [Member] | Current Liabilities [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Asset, Fair Value, Gross Asset		0		0
Derivative Liability, Fair Value, Gross Liability		717,000,000		442,000,000
Derivative Asset, Fair Value, Gross Asset		105,000,000		140,000,000
Derivative Liability, Fair Value, Gross Liability		784,000,000		529,000,000
Derivative, Fair Value, Offsets, Net		14,000,000		(56,000,000)
Income Statement Impact of Derivative Activity [Abstract]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		(361,000,000)		103,000,000		$ (40,000,000)
Derivative, Credit Risk Related Contingent Features [Abstract]
Total fair value of the derivative instruments that contain credit risk contingent features that are in a net liability position		1,000,000		3,000,000
The aggregate fair value of assets already posted as collateral		0		0
Credit Risk Contingent Features assets		0		2,000,000
Credit Risk Derivatives, at Fair Value, Net [Abstract]
Total		84,000,000	[8]	125,000,000
Energy Marketers [Member]
Credit Risk Derivatives, at Fair Value, Net [Abstract]
Total		4,000,000		10,000,000
Financial Institutions [Member]
Credit Risk Derivatives, at Fair Value, Net [Abstract]
Total		33,000,000		0
Retail End Users [Member]
Credit Risk Derivatives, at Fair Value, Net [Abstract]
Total	[9]	47,000,000		115,000,000
External Credit Rating, Investment Grade [Member]
Credit Risk Derivatives, at Fair Value, Net [Abstract]
Total	[10]	36,000,000		6,000,000
External Credit Rating, Investment Grade [Member] | Energy Marketers [Member]
Credit Risk Derivatives, at Fair Value, Net [Abstract]
Total	[10]	1,000,000		4,000,000
External Credit Rating, Investment Grade [Member] | Financial Institutions [Member]
Credit Risk Derivatives, at Fair Value, Net [Abstract]
Total	[10]	33,000,000		0
External Credit Rating, Investment Grade [Member] | Retail End Users [Member]
Credit Risk Derivatives, at Fair Value, Net [Abstract]
Total	[9],[10]	$ 2,000,000		$ 2,000,000
Swap [Member] | Natural gas derivative | Long [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative, Nonmonetary Notional Amount, Volume | Bcf		126		133
[1]	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.
[2]	Gross amounts recognized include some derivative assets and liabilities that are not subject to master netting arrangements.
[3]	Derivative Assets and Derivative Liabilities include no material amounts related to physical forward transactions with Enable.
[4]	Natural gas contracts are presented on a net basis in the Consolidated Balance Sheets as they are subject to master netting arrangements. This netting applies to all undisputed amounts due or past due and causes derivative assets (liabilities) to be ultimately presented net in a liability (asset) account within the Consolidated Balance Sheets. The net of total non-trading natural gas derivative assets and liabilities was a $24 million asset as shown on CenterPoint Energy’s Consolidated Balance Sheets (and as detailed in the table below), and was comprised of the natural gas contracts derivative assets and liabilities separately shown above, impacted by collateral netting of $14 million.
[5]	The fair value shown for natural gas contracts is comprised of derivative gross volumes totaling 1,035 Bcf or a net 59 Bcf long position. Of the net long position, basis swaps constitute a net 126 Bcf long position.
[6]	Natural gas contracts are presented on a net basis in the 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 Consolidated Balance Sheets. The net of total non-trading derivative assets and liabilities was a $109 million asset as shown on CenterPoint Energy’s Consolidated Balance Sheets (and as detailed in the table below), and was comprised of the natural gas contracts derivative assets and liabilities separately shown above, impacted by collateral netting of $56 million.
[7]	The fair value shown for natural gas contracts is comprised of derivative gross volumes totaling 767 Bcf or a net 112 Bcf long position. Of the net long position, basis swaps constitute 133 Bcf.
[8]	The net of total non-trading natural gas derivative assets was $70 million and $125 million as of December 31, 2016 and 2015, respectively, as shown on CenterPoint Energy’s Consolidated Balance Sheets, and was comprised of the natural gas contracts derivatives assets separately shown above, impacted by collateral netting of $14 million and $-0- as of December 31, 2016 and 2015, respectively.
[9]	End users are comprised primarily of customers who have contracted to fix the price of a portion of their physical gas requirements for future periods.
[10]	“Investment grade” is primarily determined using publicly available credit ratings and considers credit support (including parent company guarantees) and collateral (including cash and standby letters of credit). For unrated counterparties, CenterPoint Energy determines a synthetic credit rating by performing financial statement analysis and considers contractual rights and restrictions and collateral.

Fair Value Measurements (Detail

Fair Value Measurements (Details)		12 Months Ended
		Dec. 31, 2016USD ($)		Dec. 31, 2015USD ($)		Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Fair Value, assets and liabilities measured on recurring basis, financial statement captions
Derivative, Fair Value, Offsets, Net		$ 14,000,000		$ (56,000,000)
Indexed debt securities derivative		717,000,000		442,000,000
Gain (loss) on indexed debt securities		(413,000,000)		74,000,000		$ (86,000,000)
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount		0
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount		0
Fair Value, Liabilities, Level 1 to Level 2 Transfers, Amount		0
Fair Value, Liabilities, Level 2 to Level 1 Transfers, Amount		0
ASSETS
Derivative Asset, Fair Value, Gross Liability		(35,000,000)	[1]	(15,000,000)	[2]
Total assets		1,103,000,000		985,000,000
Liabilities
Derivative Liability, Fair Value, Gross Asset		(21,000,000)	[1]	(71,000,000)	[2]
Total liabilities		763,000,000		458,000,000
Fair value measurement using significant unobservable input (level 3) reconciliation [Roll Forward]
Beginning balance		12,000,000	[3]	17,000,000	[3]	3,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		12,000,000		0		0
Total gains		12,000,000		7,000,000		14,000,000
Total settlements		(27,000,000)		(12,000,000)		1,000,000
Transfers out of Level 3		(1,000,000)		(1,000,000)		0
Transfers into Level 3 (1)	[4]	(712,000,000)		1,000,000		(1,000,000)
Ending balance (2)	[3]	(704,000,000)		12,000,000		17,000,000
The amount of total gains (losses) for the period included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date (1)		(402,000,000)		6,000,000		16,000,000
Fair value [Member]
Fair value measurement using significant unobservable input (level 3) reconciliation [Roll Forward]
Notes receivable - affiliated companies		0		356,000,000
Long-term debt		8,846,000,000		9,067,000,000
Carrying amount [Member]
Fair value measurement using significant unobservable input (level 3) reconciliation [Roll Forward]
Notes receivable - affiliated companies		0		363,000,000
Long-term debt		8,443,000,000		8,585,000,000
Fair Value, Inputs, Level 1 [Member]
ASSETS
Total assets		1,044,000,000		864,000,000
Liabilities
Total liabilities		4,000,000		13,000,000
Fair Value, Inputs, Level 2 [Member]
ASSETS
Total assets		74,000,000		115,000,000
Liabilities
Total liabilities		56,000,000		507,000,000
Fair Value, Inputs, Level 3 [Member]
ASSETS
Total assets		20,000,000		21,000,000
Liabilities
Total liabilities		724,000,000		9,000,000
Fair Value, Measurements, Recurring [Member]
ASSETS
Corporate equities		956,000,000		807,000,000
Investments, including money market funds	[5]	77,000,000		53,000,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
ASSETS
Corporate equities		956,000,000		807,000,000
Investments, including money market funds	[5]	77,000,000		53,000,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
ASSETS
Corporate equities		0		0
Investments, including money market funds	[5]	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
ASSETS
Corporate equities		0		0
Investments, including money market funds	[5]	0		0
Natural gas derivative
Fair Value, assets and liabilities measured on recurring basis, financial statement captions
Derivative, Fair Value, Offsets, Net		14,000,000		(56,000,000)
Natural gas derivative | Fair Value, Measurements, Recurring [Member]
ASSETS
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	[6]	(35,000,000)	[1]	(15,000,000)	[2]
Natural gas derivatives (2)	[6]	70,000,000		125,000,000
Liabilities
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	[6]	(21,000,000)	[1]	(71,000,000)	[2]
Natural gas derivatives (2)	[6]	46,000,000		16,000,000
Natural gas derivative | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
ASSETS
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	[6]	11,000,000		4,000,000
Liabilities
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	[6]	4,000,000		13,000,000
Natural gas derivative | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
ASSETS
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	[6]	74,000,000		115,000,000
Liabilities
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	[6]	56,000,000		65,000,000
Natural gas derivative | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
ASSETS
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	[6]	20,000,000		21,000,000
Liabilities
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	[6]	$ 7,000,000		9,000,000
indexed debt securities derivative | Fair Value, Inputs, Level 3 [Member]
Fair Value, assets and liabilities measured on recurring basis, financial statement captions
Option volatilities		19.00%
Projected dividend growth rate		8.00%
indexed debt securities derivative | Fair Value, Measurements, Recurring [Member]
Liabilities
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		$ 0	[1]	0	[2]
Natural gas derivatives (2)		717,000,000		442,000,000
indexed debt securities derivative | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Liabilities
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		0		0
indexed debt securities derivative | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Liabilities
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		0		442,000,000
indexed debt securities derivative | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Liabilities
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		$ 717,000,000		0
Minimum [Member] | Forward Contracts [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, assets and liabilities measured on recurring basis, financial statement captions
Illiquid forward price low range		2.24
Minimum [Member] | Options Held [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, assets and liabilities measured on recurring basis, financial statement captions
Option volatilities		0.00%
Maximum [Member] | Forward Contracts [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, assets and liabilities measured on recurring basis, financial statement captions
Illiquid forward price low range		7.01
Maximum [Member] | Options Held [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, assets and liabilities measured on recurring basis, financial statement captions
Option volatilities		86.00%
Enable Midstream Partners [Member]
Fair value measurement using significant unobservable input (level 3) reconciliation [Roll Forward]
Impairment of CenterPoint Energy’s equity method investment in Enable		$ 0		1,225,000,000		0
Derivative Component Of ZENS [Member]
Fair Value, assets and liabilities measured on recurring basis, financial statement captions
Indexed debt securities derivative		717,000,000		442,000,000		541,000,000	$ 455,000,000
Gain (loss) on indexed debt securities		$ (296,000,000)		$ 81,000,000		$ (86,000,000)
[1]	Amounts represent the impact of legally enforceable master netting arrangements that allow CenterPoint Energy to settle positive and negative positions and also include cash collateral of $14 million held by CES from the same counterparties.
[2]	Amounts represent the impact of legally enforceable master netting arrangements that allow CenterPoint Energy to settle positive and negative positions and also include cash collateral of $56 million posted with the same counterparties.
[3]	During 2016, 2015 and 2014, CenterPoint Energy did not have significant Level 3 sales.
[4]	During 2016, CenterPoint Energy transferred its indexed debt securities from Level 2 to Level 3 to reflect changes in the significance of the unobservable inputs used in the valuation. As of December 31, 2016, the indexed debt securities liability was $717 million. During 2016, there was a loss of $413 million on the indexed debt securities.
[5]	Amounts are included in Prepaid and Other Current Assets and Other Assets in the Consolidated Balance Sheets.
[6]	Natural gas derivatives include no material amounts related to physical forward transactions with Enable.

Unconsolidated Affiliates (Deta

Unconsolidated Affiliates (Details) - USD ($) $ in Millions	Nov. 22, 2016	Feb. 18, 2016	Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cost Method Investments			$ 363		$ 0
Service Agreement Notice For Termination At Term End			90 days
Service Agreement Notice For Termination At Will Number Of Days			180 days
Enable and ArcLight [Member]
Partners' Capital Account, Units, Sold in Public Offering	1,500,000
CERC Corp [Member]
Sale of Units, Percentage, Trigger Right of First Refusal			5.00%
OGE [Member]
Sale of Units, Percentage, Trigger Right of First Refusal			5.00%
Enable Midstream Partners [Member]
Partners' Capital Account, Units, Sold in Public Offering	10,000,000
Southeast Supply Header LLC [Member]
Equity Method Investment, Ownership Percentage							25.05%
Enable Midstream Partners [Member]
Equity Method Investment, Ownership Percentage			54.10%	[1]	55.40%	55.40%
Enable Midstream Partners [Member]
Notes receivable - affiliated companies			$ 363
Series A Preferred Stock [Member] | Enable Midstream Partners [Member]
Purchase of Preferred Units, Number of Units Purchased		14,520,000
Cost Method Investments			$ 363
Minimum [Member] | Indebtedness to CERC Corp. [Member] | Enable Midstream Partners [Member]
Debt Instrument, Interest Rate, Stated Percentage			2.10%
Maximum [Member] | Indebtedness to CERC Corp. [Member] | Enable Midstream Partners [Member]
Debt Instrument, Interest Rate, Stated Percentage			2.45%
[1]	In November 2016, Enable closed a public offering of 10,000,000 common units. In connection with the offering, Enable and an affiliate of ArcLight sold an additional combined 1,500,000 common units to the underwriters.

Unconsolidated Affiliates Finan

Unconsolidated Affiliates Financial Data (Details) - USD ($)		Nov. 22, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014	Jun. 30, 2015	May 30, 2014	Dec. 31, 2013
Transaction with Enable [Abstract]
Investment in unconsolidated affiliates			$ 2,594,000,000		$ 2,505,000,000		$ 2,594,000,000
Equity in earnings (losses) of unconsolidated affiliates					$ 208,000,000		(1,633,000,000)	$ 308,000,000
Equity Method Investment, Summarized Financial Information, Gross Profit (Loss) [Abstract]
Basis Difference, Amortization Period					33 years
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
Investment in unconsolidated affiliates			2,594,000,000		$ 2,505,000,000		2,594,000,000
Proceeds from Equity Method Investment, Dividends or Distributions					319,000,000		294,000,000	305,000,000
Enable Midstream Partners [Member]
Transaction with Enable [Abstract]
Impairment of CenterPoint Energy’s equity method investment in Enable					$ 0		1,225,000,000	0
Equity Method Investment, Carrying Value Per Unit					$ 10.71
Investment in unconsolidated affiliates			$ 2,594,000,000		$ 2,505,000,000		2,594,000,000
Equity in earnings (losses) of unconsolidated affiliates	[1]				$ 208,000,000		$ (1,633,000,000)	$ 303,000,000
Limited Partner Interest in Enable [Abstract]
Equity Method Investment, Ownership Percentage			55.40%		54.10%	[2]	55.40%	55.40%
Equity Method Investment, Summarized Financial Information, Gross Profit (Loss) [Abstract]
Operating revenues					$ 2,272,000,000		$ 2,418,000,000	$ 3,367,000,000
Cost of sales, excluding depreciation and amortization					1,017,000,000		1,097,000,000	1,914,000,000
Impairment of goodwill and other long-lived assets					9,000,000		1,134,000,000	8,000,000
Operating income (loss)					385,000,000		(712,000,000)	586,000,000
Net income (loss) attributable to Enable					290,000,000		(752,000,000)	530,000,000
CenterPoint Energy’s interest					160,000,000		(416,000,000)	298,000,000
Basis difference amortization (1)	[3]				48,000,000		8,000,000	5,000,000
Impairment of CenterPoint Energy’s equity method investment in Enable					0		(1,225,000,000)	0
Impairment Charges			$ 984,000,000	$ 862,000,000			1,846,000,000
Goodwill And Long-LIved Assets Impairment Charges, Entity's Share							621,000,000
Income (Loss) From Equity Method Investment, Excluding Impairment Charge							213,000,000
Equity Method Investment, Summarized Financial Information, Assets [Abstract]
Current assets			381,000,000		396,000,000		381,000,000
Non-current assets			10,845,000,000		10,816,000,000		10,845,000,000
Current liabilities			615,000,000		362,000,000		615,000,000
Non-current liabilities			3,080,000,000		3,056,000,000		3,080,000,000
Non-controlling interest			12,000,000		12,000,000		12,000,000
Preferred equity			0		362,000,000		0
Enable partners' capital			7,519,000,000		7,420,000,000		7,519,000,000
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
CenterPoint Energy’s ownership interest in Enable partners’ capital			4,163,000,000		4,067,000,000		4,163,000,000
CenterPoint Energy’s basis difference			(1,569,000,000)		(1,562,000,000)		(1,569,000,000)
Investment in unconsolidated affiliates			2,594,000,000		2,505,000,000		2,594,000,000
Southeast Supply Header LLC [Member]
Transaction with Enable [Abstract]
Equity in earnings (losses) of unconsolidated affiliates	[4]				0		0	5,000,000
Limited Partner Interest in Enable [Abstract]
Equity Method Investment, Ownership Percentage											25.05%
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
Proceeds from Equity Method Investment, Dividends or Distributions	[4]				$ 0		$ 0	$ 7,000,000
Equity Method Investment, Contributed Ownership Percentage									0.10%	24.95%
Enable and ArcLight [Member]
Limited Partner Interest in Enable [Abstract]
Partners' Capital Account, Units, Sold in Public Offering		1,500,000
Enable Midstream Partners [Member]
Transaction with Enable [Abstract]
Share Price					$ 15.73
Limited Partner Interest in Enable [Abstract]
Partners' Capital Account, Units, Sold in Public Offering		10,000,000
Enable Midstream Partners [Member]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
Incentive Distribution Right, Maximum					50.00%
Enable Midstream Partners [Member] | CERC Corp [Member]
Limited Partner Interest in Enable [Abstract]
Management Rights Ownership Percentage					50.00%
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
Incentive Distribution Right, Percentage					40.00%
Enable Midstream Partners [Member] | OGE [Member]
Limited Partner Interest in Enable [Abstract]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage					25.70%		26.30%	26.30%
Management Rights Ownership Percentage					50.00%
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
Incentive Distribution Right, Percentage					60.00%
Common Stock [Member] | Enable Midstream Partners [Member]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
Proceeds from Equity Method Investment, Dividends or Distributions					$ 297,000,000		$ 294,000,000	$ 298,000,000
Preferred Stock [Member] | Enable Midstream Partners [Member]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
Proceeds from Equity Method Investment, Dividends or Distributions					$ 22,000,000	[5]	0	0
Maximum [Member] | Enable Midstream Partners [Member]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
Incentive Distribution, Distribution Per Unit					$ 0.330625
Minimum [Member] | Enable Midstream Partners [Member]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]
Incentive Distribution, Distribution Per Unit					$ 0.2875
Enable Midstream Partners [Member]
Transaction with Enable [Abstract]
Interest income related to notes receivable from Enable					$ 1,000,000		8,000,000	8,000,000
Interest receivable related to notes receivable from Enable			4,000,000		0		4,000,000
Transitional Service [Member] | Enable Midstream Partners [Member]
Transaction with Enable [Abstract]
Reimbursement of transition services (1)	[6]				7,000,000		16,000,000	163,000,000
Accounts receivable for amounts billed for transition services			3,000,000		1,000,000		3,000,000
Natural Gas Expenses [Member] | Enable Midstream Partners [Member]
Transaction with Enable [Abstract]
Natural gas expenses, including transportation and storage costs					110,000,000		117,000,000	$ 130,000,000
Accounts payable for natural gas purchases from Enable			$ 11,000,000		$ 10,000,000		$ 11,000,000
Subordinated Units [Member] | Enable Midstream Partners [Member]
Limited Partner Interest in Enable [Abstract]
Equity Method Investment, Ownership, Shares					139,704,916
Subordinated Units [Member] | Enable Midstream Partners [Member] | OGE [Member]
Limited Partner Interest in Enable [Abstract]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership, Shares					68,150,514
Common Stock [Member] | Enable Midstream Partners [Member]
Limited Partner Interest in Enable [Abstract]
Equity Method Investment, Ownership, Shares					94,151,707
Common Stock [Member] | Enable Midstream Partners [Member] | OGE [Member]
Limited Partner Interest in Enable [Abstract]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership, Shares					42,832,291
[1]	These amounts include impairment charges totaling $1,846 million composed of CenterPoint Energy’s impairment of its equity method investment in Enable of $1,225 million and CenterPoint Energy’s share, $621 million, of impairment charges Enable recorded for goodwill and long-lived assets for the year ended December 31, 2015. This impairment is offset by $213 million of earnings for the year ended December 31, 2015.
[2]	In November 2016, Enable closed a public offering of 10,000,000 common units. In connection with the offering, Enable and an affiliate of ArcLight sold an additional combined 1,500,000 common units to the underwriters.
[3]	Equity in earnings of unconsolidated affiliates includes CenterPoint Energy’s share of Enable earnings adjusted for the amortization of the basis difference of CenterPoint Energy’s original investment in Enable and its underlying equity in net assets of Enable. The basis difference is being amortized over approximately 33 years, the average life of the assets to which the basis difference is attributed.
[4]	CenterPoint Energy contributed a 24.95% interest in SESH to Enable on May 30, 2014 and its remaining 0.1% interest in SESH to Enable on June 30, 2015.
[5]	Represents the period from February 18, 2016 to December 31, 2016.
[6]	Represents amounts billed under the Transition Agreements, including the costs of seconded employees. Actual transition services costs are recorded net of reimbursement.

Indexed Debt Securities (ZENS60

Indexed Debt Securities (ZENS) and Securities Related to ZENS (Details)		12 Months Ended
		Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2016USD ($)shares	May 18, 2016$ / sharesshares	May 17, 2016	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Zero Premium Exchangeable Subordinated Notes [Abstract]
Distribution to ZENS holders		$ 178,000,000	$ 32,000,000	$ 0
Schedule of ZENS activities [Abstract]
Distribution to ZENS holders		178,000,000	32,000,000	0
Reduction In Indexed Debt		(40,000,000)
Reduction In ZENS Derivative Obligation		(21,000,000)
Realized Loss On Indexed Debt Securities		117,000,000
Referenced common shares
Investment in marketable securities		805,000,000	805,000,000		$ 953,000,000			$ 805,000,000
TW Securities
TW Securities		805,000,000
Proceeds from Sale and Maturity of Marketable Securities		(178,000,000)	(32,000,000)	0
Gain (loss) on TW Securities		326,000,000	(93,000,000)	163,000,000
TW Securities		953,000,000	805,000,000
Debt component of ZENS
Debt Component of ZENS		145,000,000
Distribution to ZENS holders		178,000,000	32,000,000	0
Debt Component of ZENS		114,000,000	145,000,000
Derivative component of ZENS
Derivative Component of ZENS		442,000,000
Distribution to ZENS holders		178,000,000	32,000,000	0
Loss (gain) on indexed debt securities		413,000,000	(74,000,000)	86,000,000
Derivative Component of ZENS		717,000,000	442,000,000
Unamortized debt issuance expense					$ 42,000,000			44,000,000
TW Common [Member]
Schedule of Trading Securities [Line Items]
Number of shares of common stock held by subsidiary of CenterPoint Energy (in shares) | shares					7,100,000
TWC Common [Member]
Zero Premium Exchangeable Subordinated Notes [Abstract]
Cash Exchanged, Per Share Held | $ / shares						$ 100
Fractional Shares Exchanged For Shares Held | shares						0.4891
Time Common [Member]
Schedule of Trading Securities [Line Items]
Number of shares of common stock held by subsidiary of CenterPoint Energy (in shares) | shares					900,000
Charter Common [Member]
Schedule of Trading Securities [Line Items]
Number of shares of common stock held by subsidiary of CenterPoint Energy (in shares) | shares					900,000
Zero Premium Exchangeable Subordinated Notes [Abstract]
Proceeds from Sale and Maturity of Trading Securities Held-for-investment		178,000,000
Shares Received for Shares Held | shares						872,531
TW Securities [Member]
Referenced common shares
Investment in marketable securities		805,000,000	930,000,000	767,000,000	$ 953,000,000			805,000,000	$ 930,000,000	$ 767,000,000
TW Securities
TW Securities		805,000,000	930,000,000	767,000,000
Proceeds from Sale and Maturity of Marketable Securities		(178,000,000)	(32,000,000)
Gain (loss) on TW Securities		326,000,000	(93,000,000)	163,000,000
TW Securities		953,000,000	805,000,000	930,000,000
Debt Component Of ZENS [Member]
Zero Premium Exchangeable Subordinated Notes [Abstract]
Distribution to ZENS holders	[1]	40,000,000	7,000,000
Schedule of ZENS activities [Abstract]
Distribution to ZENS holders	[1]	40,000,000	7,000,000
Debt component of ZENS
Debt Component of ZENS	[1]	145,000,000	142,000,000	132,000,000
Accretion of debt component of ZENS	[1]	26,000,000	27,000,000	27,000,000
2 % interest paid	[1]	(17,000,000)	(17,000,000)	(17,000,000)
Distribution to ZENS holders	[1]	40,000,000	7,000,000
Debt Component of ZENS	[1]	114,000,000	145,000,000	142,000,000
Derivative component of ZENS
Distribution to ZENS holders	[1]	40,000,000	7,000,000
Derivative Component Of ZENS [Member]
Zero Premium Exchangeable Subordinated Notes [Abstract]
Distribution to ZENS holders		21,000,000	18,000,000
Schedule of ZENS activities [Abstract]
Distribution to ZENS holders		21,000,000	18,000,000
Debt component of ZENS
Distribution to ZENS holders		21,000,000	18,000,000
Derivative component of ZENS
Derivative Component of ZENS		442,000,000	541,000,000	455,000,000
Distribution to ZENS holders		21,000,000	18,000,000
Loss (gain) on indexed debt securities		296,000,000	(81,000,000)	86,000,000
Derivative Component of ZENS		$ 717,000,000	$ 442,000,000	$ 541,000,000
Subordinated Debt ZENS Member
Zero Premium Exchangeable Subordinated Notes [Abstract]
Original principal amount of Zero Premium Exchangeable Subordinated Notes issued by CenterPoint Energy in September 1999					1,000,000,000
Long-term Debt, Gross					$ 828,000,000
Percentage of market value of referenced shares of Time Warner Common each zero premium exchangeable subordinated note could be exchanged for cash (in hundredths)		95.00%
Referenced common shares
Debt Instrument, Interest Rate, Stated Percentage					2.00%
Target annual yield from interest and cash dividends on referenced shares before principal amount of indexed debt securities is increased or decreased (in hundredths)					2.309%
Long-term Debt, Gross					$ 828,000,000
Contingent principal amount of indexed debt securities issued by CenterpPoint Energy in September 1999 and outstanding and exchangeable					514,000,000
Percentage of market value of referenced shares of Time Warner Common each zero premium exchangeable subordinated note could be exchanged for cash (in hundredths)		95.00%
The cash exchange amount from referenced shares per $1,000 face amount of individual notes					1,094
Face amount of each indexed debt security notes issued by CenterPoint Energy in September 1999					$ 1,000
The accretion rate for interest charges on bifurcated debt component of indexed debt securities (in hundredths)		19.50%
Subordinated Debt ZENS Member | TW Common [Member]
Zero Premium Exchangeable Subordinated Notes [Abstract]
The referenced shares of common stock for each zero premium exchangeable subordinated note (in shares)					0.5		0.5
Subordinated Debt ZENS Member | TWC Common [Member]
Zero Premium Exchangeable Subordinated Notes [Abstract]
The referenced shares of common stock for each zero premium exchangeable subordinated note (in shares)							0.125505
Subordinated Debt ZENS Member | Time Common [Member]
Zero Premium Exchangeable Subordinated Notes [Abstract]
The referenced shares of common stock for each zero premium exchangeable subordinated note (in shares)					0.0625		0.0625
Subordinated Debt ZENS Member | Charter Common [Member]
Zero Premium Exchangeable Subordinated Notes [Abstract]
The referenced shares of common stock for each zero premium exchangeable subordinated note (in shares)					0.061382
ASU 2015-03 Restatement [Member]
Derivative component of ZENS
Unamortized debt issuance expense								$ 9,000,000	$ 10,000,000	$ 11,000,000
[1]	To reflect adoption of ASU 2015-03, balances have been restated to include unamortized debt issuance costs of $9 million, $10 million and $11 million as of December 31, 2015, 2014 and 2013, respectively.

Equity (Details)

Equity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Dividends Declared Per Share	$ 1.03	$ 0.99	$ 0.95
Enable Midstream Partners [Member]
Retained Earnings, Undistributed Earnings from Equity Method Investees	$ 0	$ 0

Short Term Borrowings and Lon62

Short Term Borrowings and Long Term Debt Schedule of Debt (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Short term borrowings:
Total short-term borrowings	[1]	$ 35	$ 40
Long-term debt:
Unamortized Issuance Costs		(33)	(35)	[2]
Unamortized Discount (Premium), Net		(36)	(42)	[2]
Long-term Debt, Excluding Current Maturities		7,532	7,866	[2]
Long-term Debt, Current Maturities	[1]	1,025	864
Debt, Current	[1]	$ 1,060	904
ZENS due 2029 (4)
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		2.00%
Parent Company [Member]
Long-term debt:
Capital Lease Obligations, Noncurrent		$ 0	0	[2]
Capital Lease Obligations, Current	[1]	0	3
Parent Company [Member] | ZENS due 2029 (4)
Long-term debt:
Long-Term	[3]	0	0	[2]
Current	[1],[3]	114	145
Parent Company [Member] | Senior notes 5.95% due 2017
Long-term debt:
Long-Term		0	550	[2]
Current	[1]	250	0
Parent Company [Member] | Pollution control bonds 5.05% to 5.125% due 2018 to 2028 (5)
Long-term debt:
Long-Term	[4]	118	118	[2]
Current	[1],[4]	0	0
Amount of debt secured by general mortgage bonds		118	118
Parent Company [Member] | Commercial paper (6)
Long-term debt:
Long-Term	[5]	835	716	[2]
Current	[1],[5]	0	0
CenterPoint Houston [Member] | Bank Loans
Long-term debt:
Long-Term		0	200	[2]
Current	[1]	$ 0	0
CenterPoint Houston [Member] | First mortgage bonds 9.15% due 2021
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		9.15%
Long-term debt:
Long-Term		$ 102	102	[2]
Current	[1]	0	0
Amount of debt secured by general mortgage bonds		102
CenterPoint Houston [Member] | General mortgage bonds 1.85% to 6.95% due 2021 to 2044
Long-term debt:
Long-Term		2,512	1,912	[2]
Current	[1]	0	0
Amount of debt secured by general mortgage bonds		2,600
CenterPoint Houston [Member] | System restoration bonds 3.46% to 4.243% due 2018 to 2022
Long-term debt:
Long-Term		312	365	[2]
Current	[1]	53	50
CenterPoint Houston [Member] | Transition bonds 0.901% to 5.302% due 2017 to 2024
Long-term debt:
Long-Term		1,560	1,918	[2]
Current	[1]	358	341
CERC Corp [Member] | Commercial paper (6)
Long-term debt:
Long-Term	[5]	569	219	[2]
Current	[1]	0	0
CERC Corp [Member] | Senior notes 4.50% to 6.625% due 2017 to 2041
Long-term debt:
Long-Term		1,593	1,843	[2]
Current	[1]	250	325
Product Financing Arrangement [Member]
Short term borrowings:
Total short-term borrowings	[1],[6]	$ 35	$ 40
Minimum [Member] | Parent Company [Member] | Senior notes 5.95% due 2017
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.95%
Minimum [Member] | Parent Company [Member] | Pollution control bonds 5.05% to 5.125% due 2018 to 2028 (5)
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.05%
Minimum [Member] | CenterPoint Houston [Member] | General mortgage bonds 1.85% to 6.95% due 2021 to 2044
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		1.85%
Minimum [Member] | CenterPoint Houston [Member] | System restoration bonds 3.46% to 4.243% due 2018 to 2022
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.46%
Minimum [Member] | CenterPoint Houston [Member] | Transition bonds 0.901% to 5.302% due 2017 to 2024
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		0.901%
Minimum [Member] | CERC Corp [Member] | Senior notes 4.50% to 6.625% due 2017 to 2041
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		4.50%
Maximum [Member] | Parent Company [Member] | Pollution control bonds 5.05% to 5.125% due 2018 to 2028 (5)
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.125%
Maximum [Member] | CenterPoint Houston [Member] | General mortgage bonds 1.85% to 6.95% due 2021 to 2044
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.95%
Maximum [Member] | CenterPoint Houston [Member] | System restoration bonds 3.46% to 4.243% due 2018 to 2022
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		4.243%
Maximum [Member] | CenterPoint Houston [Member] | Transition bonds 0.901% to 5.302% due 2017 to 2024
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.302%
Maximum [Member] | CERC Corp [Member] | Senior notes 4.50% to 6.625% due 2017 to 2041
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.625%
[1]	Includes amounts due or exchangeable within one year of the date noted.
[2]	Includes $35 million of unamortized debt issuance costs to reflect adoption of ASU 2015-03.
[3]	CenterPoint Energy’s ZENS obligation is bifurcated into a debt component and an embedded derivative component. For additional information regarding ZENS, see Note 11(b). As ZENS are exchangeable for cash at any time at the option of the holders, these notes are classified as a current portion of long-term debt.
[4]	$118 million of these series of debt were secured by general mortgage bonds of Houston Electric as of both December 31, 2016 and 2015.
[5]	Classified as long-term debt because the termination date of the facility that backstops the commercial paper is more than one year from the date noted.
[6]	NGD currently has AMAs associated with its utility distribution service in Arkansas, north Louisiana and Oklahoma that extend through 2020. Pursuant to the provisions of the agreements, NGD 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 an inventory financing.

Short Term Borrowings and Lon63

Short Term Borrowings and Long Term Debt Long-term Debt (Details) $ in Millions		Jan. 12, 2017USD ($)	Dec. 31, 2016USD ($)	Aug. 08, 2016USD ($)	May 13, 2016USD ($)	May 01, 2016USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Line of Credit Facility [Abstract]
Size of Facility			$ 2,500				$ 2,500	$ 2,100
Long term Debt Excluding ZENS [Member]
Annual maturities of long term debt, capital leases, and sinking fund requirements, excluding ZENS obligations [Abstract]
2,017	[1]		911				911
2,018	[1]		784				784
2,019	[1]		458				458
2,020	[1]		231				231
2,021	[1]		2,610				2,610
Securitization Bonds [Member]
Annual maturities of long term debt, capital leases, and sinking fund requirements, excluding ZENS obligations [Abstract]
2,017			411				411
2,018			434				434
2,019			458				458
2,020			231				231
2,021			211				211
Parent Company [Member]
Line of Credit Facility [Abstract]
Size of Facility			$ 1,600				$ 1,600	1,200
Parent Company [Member] | Senior Notes [Member]
Long-term debt:
Debt Instrument, Interest Rate, Stated Percentage			6.50%				6.50%
Debt Instrument, Redemption Price, Percentage			100.00%
Extinguishment of Debt, Amount			$ 300
Gain (Loss) on Extinguishment of Debt			22
CenterPoint Houston [Member]
Line of Credit Facility [Abstract]
Size of Facility			300				$ 300	300
CenterPoint Houston [Member] | Municipal Bonds [Member]
Long-term debt:
Extinguishment of Debt, Amount			$ 56
CenterPoint Houston [Member] | First mortgage bonds 9.15% due 2021
Long-term debt:
Debt Instrument, Interest Rate, Stated Percentage			9.15%				9.15%
Annual maturities of long term debt, capital leases, and sinking fund requirements, excluding ZENS obligations [Abstract]
Secured debt amount with asset liens			$ 102				$ 102
Replacement fund requirements to be satisfied in 2017			240				240
Sinking fund requirements to be satisfied in 2017			1.6				1.6
CenterPoint Houston [Member] | General mortgage bonds 1.85% to 6.95% due 2021 to 2044
Annual maturities of long term debt, capital leases, and sinking fund requirements, excluding ZENS obligations [Abstract]
Secured debt amount with asset liens			2,600				2,600
CenterPoint Houston [Member] | Bonds General Mortgage Due 2021 [Member]
Long-term debt:
Debt Instrument, Interest Rate, Stated Percentage					1.85%
Debt Instrument, Maturity Date					May 13, 2021
Debt Instrument, Face Amount					$ 300
CenterPoint Houston [Member] | Bonds General Mortgage Due 2026 [Member]
Long-term debt:
Debt Instrument, Interest Rate, Stated Percentage				2.40%
Debt Instrument, Maturity Date				Aug. 8, 2026
Debt Instrument, Face Amount				$ 300
CERC Corp [Member]
Line of Credit Facility [Abstract]
Size of Facility			600				600	600
CERC Corp [Member] | Senior Notes [Member]
Long-term debt:
Debt Instrument, Interest Rate, Stated Percentage						6.15%
Extinguishment of Debt, Amount						$ 325
Revolving Credit Facility [Member]
Line of Credit Facility [Abstract]
Loans			0				0	200
Revolving Credit Facility [Member] | Parent Company [Member]
Line of Credit Facility [Abstract]
Loans			0				0	0
Revolving Credit Facility [Member] | CenterPoint Houston [Member]
Line of Credit Facility [Abstract]
Loans			0				0	$ 200	[2]
Debt, Weighted Average Interest Rate								1.64%
Revolving Credit Facility [Member] | CERC Corp [Member]
Line of Credit Facility [Abstract]
Loans			$ 0				$ 0	$ 0
Line of Credit [Member] | Parent Company [Member]
Line of Credit Facility [Abstract]
Percentage on limitation of debt to total capitalization under covenant (in hundredths)	[3]						65.00%
Ratio of Indebtedness to Net Capital	[4]		0.560				0.560
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
Consecutive Period for System Restoration Costs to Exceed $100 million (in months)							12
Line of Credit [Member] | CenterPoint Houston [Member]
Line of Credit Facility [Abstract]
Percentage on limitation of debt to total capitalization under covenant (in hundredths)	[3]						65.00%
Ratio of Indebtedness to Net Capital	[4]		0.474				0.474
Line of Credit [Member] | CERC Corp [Member]
Line of Credit Facility [Abstract]
Percentage on limitation of debt to total capitalization under covenant (in hundredths)							65.00%
Ratio of Indebtedness to Net Capital	[4]		0.358				0.358
Line of Credit [Member] | London Interbank Offered Rate (LIBOR) [Member] | Parent Company [Member]
Line of Credit Facility [Abstract]
Debt Instrument, Basis Spread on Variable Rate	[5]						1.25%
Line of Credit [Member] | London Interbank Offered Rate (LIBOR) [Member] | CenterPoint Houston [Member]
Line of Credit Facility [Abstract]
Debt Instrument, Basis Spread on Variable Rate	[5]						1.125%
Line of Credit [Member] | London Interbank Offered Rate (LIBOR) [Member] | CERC Corp [Member]
Line of Credit Facility [Abstract]
Debt Instrument, Basis Spread on Variable Rate	[5]						1.25%
Letter of Credit [Member]
Line of Credit Facility [Abstract]
Loans			$ 14				$ 14	12
Letter of Credit [Member] | Parent Company [Member]
Line of Credit Facility [Abstract]
Loans			6				6	6
Letter of Credit [Member] | CenterPoint Houston [Member]
Line of Credit Facility [Abstract]
Loans			4				4	4
Letter of Credit [Member] | CERC Corp [Member]
Line of Credit Facility [Abstract]
Loans			4				4	2
Commercial paper (6)
Line of Credit Facility [Abstract]
Loans			1,404				1,404	935
Commercial paper (6) | Parent Company [Member]
Line of Credit Facility [Abstract]
Loans	[6]		$ 835				$ 835	$ 716
Debt, Weighted Average Interest Rate			1.04%				1.04%	0.79%
Commercial paper (6) | CenterPoint Houston [Member]
Line of Credit Facility [Abstract]
Loans			$ 0				$ 0	$ 0
Commercial paper (6) | CERC Corp [Member]
Line of Credit Facility [Abstract]
Loans	[7]		$ 569				$ 569	$ 219
Debt, Weighted Average Interest Rate			1.03%				1.03%	0.81%
Subsequent Event [Member] | CenterPoint Houston [Member] | Bonds General Mortgage Due 2027 [Member]
Long-term debt:
Debt Instrument, Interest Rate, Stated Percentage		3.00%
Debt Instrument, Maturity Date		Jan. 17, 2027
Debt Instrument, Face Amount		$ 300
[1]	These maturities include Securitization Bonds principal repayments on scheduled payment dates.
[2]	Weighted average interest rate was approximately 1.64% as of December 31, 2015.
[3]	The financial covenant limit will temporarily increase from 65% to 70% if Houston Electric experiences damage from a natural disaster in its service territory and CenterPoint Energy certifies to the administrative agent that Houston Electric has incurred system restoration costs reasonably likely to exceed $100 million in a consecutive twelve-month period, all or part of which Houston Electric intends to seek to recover through securitization financing. Such temporary increase in the financial covenant would be in effect from the date CenterPoint Energy delivers its certification until the earliest to occur of (i) the completion of the securitization financing, (ii) the first anniversary of CenterPoint Energy’s certification or (iii) the revocation of such certification.
[4]	As defined in the revolving credit facility agreement, excluding Securitization Bonds.
[5]	Based on current credit ratings.
[6]	Weighted average interest rate was approximately 1.04% and 0.79% as of December 31, 2016 and December 31, 2015, respectively.
[7]	Weighted average interest rate was approximately 1.03% and 0.81% as of December 31, 2016 and December 31, 2015, respectively.

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other Tax Carryforward [Line Items]
Effective Income Tax Rate Reconciliation, Deduction, Amount	$ 0	$ 0	$ (29)
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	3	0	0
Current income tax expense (benefit):
Federal	23	(37)	(20)
State	18	12	14
Total current expense (benefit)	41	(25)	(6)
Deferred income tax expense (benefit):
Federal	185	(359)	273
Deferred State and Local Income Tax Expense (Benefit)	28	(54)	7
Total deferred expense (benefit)	213	(413)	280
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	3
Total income tax expense (benefit)	254	(438)	274
Income tax reconciliation [Abstract]
Income (loss) before income taxes	$ 686	$ (1,130)	$ 885
Federal statutory income tax rate	35.00%	35.00%	35.00%
Expected federal income tax expense (benefit)	$ 240	$ (396)	$ 310
Increase (decrease) in tax expense resulting from:
State income tax expense, net of federal income tax	27	(27)	16
Other, net	(16)	(15)	(23)
Total	14	(42)	(36)
Total income tax expense (benefit)	$ 254	$ (438)	$ 274
Effective tax rate (in hundredths)	37.00%	39.00%	31.00%
Increase (Decrease) in Deferred Income Taxes			$ (32)
Increase (Decrease) in Accrued Taxes Payable			(5)
Increase (Decrease) in Income Taxes			$ (8)
Deferred tax assets:
Benefits and compensation	$ 316	$ 334
Loss and credit carryforwards	79	115
AROs	77	73
Other	21	45
Valuation allowance	(5)	(2)
Deferred Tax Assets, Net of Valuation Allowance	488	565
Deferred tax liabilities:
Property, plant, and equipment	2,603	2,423
Investment in unconsolidated affiliates	1,383	1,277
Regulatory assets/liabilities, net	883	1,060
Investment in marketable securities and indexed debt	772	654
Deferred Tax Liabilities, Derivatives	4	91
Other	106	107
Deferred Tax Liabilities, Gross	5,751	5,612
Deferred Tax Liabilities, Net	5,263	$ 5,047
State and Local Jurisdiction [Member]
Deferred income tax expense (benefit):
State	6
Deferred tax liabilities:
Operating Loss Carryforwards	962
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	11
State and Local Jurisdiction [Member] | Capital Loss Carryforward [Member]
Deferred tax liabilities:
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	$ 244
Latest Tax Year [Member] | State and Local Jurisdiction [Member]
Deferred tax liabilities:
Tax Credit Carryforward, Expiration Date	Dec. 31, 2036
Latest Tax Year [Member] | State and Local Jurisdiction [Member] | Capital Loss Carryforward [Member]
Deferred tax liabilities:
Tax Credit Carryforward, Expiration Date	Dec. 31, 2017
Earliest Tax Year [Member] | State and Local Jurisdiction [Member]
Deferred tax liabilities:
Tax Credit Carryforward, Expiration Date	Dec. 31, 2017

Commitments and Contingencies65

Commitments and Contingencies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating Leases, Future Minimum Payments Due [Abstract]
2,017	$ 5
2,018	4
2,019	4
2,020	3
2,021	3
2022 and beyond	7
Total	26
Total lease expense for all operating leases	10	$ 9	$ 11
Minnesota Service Territory [Member] | CERC Corp [Member]
Legal Environmental And Other Regulatory Matters Legal Matters Gas Market Manipulation Cases Abstract
Liability recorded for remediation of Minnesota sites	7
Natural Gas Supply Commitments [Member]
Long-term Purchase Commitment [Line Items]
2,017	461
2,018	467
2,019	268
2,020	125
2,021	127
2022 and beyond	8
Maximum [Member] | Minnesota Service Territory [Member] | CERC Corp [Member]
Legal Environmental And Other Regulatory Matters Legal Matters Gas Market Manipulation Cases Abstract
Estimated remediation costs for the Minnesota sites	$ 30
Site Contingency, Years to Resolve Contingency	50 years
Minimum [Member] | Minnesota Service Territory [Member] | CERC Corp [Member]
Legal Environmental And Other Regulatory Matters Legal Matters Gas Market Manipulation Cases Abstract
Estimated remediation costs for the Minnesota sites	$ 5
Site Contingency, Years to Resolve Contingency	30 years

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended																12 Months Ended
		Dec. 31, 2016		Sep. 30, 2016		Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2015	[1]	Sep. 30, 2015	[3]	Jun. 30, 2015		Mar. 31, 2015		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net income (loss)		$ 101		$ 179		$ (2)		$ 154		$ (509)	[2]	$ (391)		$ 77		$ 131		$ 432	$ (692)	$ 611
Weighted Average Number of Shares Outstanding, Basic																		430,606,000	430,180,000	429,634,000
Plus: Incremental shares from assumed conversions:
Diluted weighted average shares (in shares)																		433,603,000	430,180,000	431,668,000
Basic earnings per share:
Basic earnings (loss) per share		$ 0.23	[2]	$ 0.42	[2]	$ (0.01)	[2]	$ 0.36	[2]	$ (1.18)		$ (0.91)	[2]	$ 0.18	[2]	$ 0.30	[2]	$ 1	$ (1.61)	$ 1.42
Diluted earnings per share:
Diluted earnings (loss) per share		$ 0.23	[2]	$ 0.41	[2]	$ (0.01)	[2]	$ 0.36	[2]	$ (1.18)		$ (0.91)	[2]	$ 0.18	[2]	$ 0.30	[2]	$ 1	$ (1.61)	$ 1.42
Restricted Stock [Member]
Plus: Incremental shares from assumed conversions:
Stock options (in shares)	[4]																	2,997,000	0	2,034,000
Diluted earnings per share:
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount																			2,349,000
[1]	CenterPoint Energy recognized $984 million ($620 million after tax) in impairment charges related to Enable during the three months ended December 31, 2015.
[2]	Quarterly earnings (loss) per common share are based on the weighted average number of shares outstanding during the quarter, and the sum of the quarters may not equal annual earnings (loss) per common share.
[3]	CenterPoint Energy recognized $862 million ($537 million after tax) in impairment charges related to Enable during the three months ended September 30, 2015.
[4]	2,349,000 incremental shares from assumed conversions of restricted stock have not been included in the computation of diluted earnings (loss) per share for the year ended December 31, 2015, as their inclusion would be anti-dilutive.

Unaudited Quarterly Informati67

Unaudited Quarterly Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended																12 Months Ended
	Dec. 31, 2016		Sep. 30, 2016		Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2015		Sep. 30, 2015		Jun. 30, 2015		Mar. 31, 2015		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Selected Quarterly Financial Information [Abstract]
Total	$ 2,081		$ 1,889		$ 1,574		$ 1,984		$ 1,791	[1]	$ 1,630	[2]	$ 1,532		$ 2,433		$ 7,528	$ 7,386	$ 9,226
Operating income	243		284		182		250		226	[1]	265	[2]	186		256		959	933	935
Net income (loss)	$ 101		$ 179		$ (2)		$ 154		$ (509)	[1],[3]	$ (391)	[2]	$ 77		$ 131		$ 432	$ (692)	$ 611
Basic Earnings Per Share:
Basic earnings (loss) per share	$ 0.23	[3]	$ 0.42	[3]	$ (0.01)	[3]	$ 0.36	[3]	$ (1.18)	[1]	$ (0.91)	[2],[3]	$ 0.18	[3]	$ 0.30	[3]	$ 1	$ (1.61)	$ 1.42
Diluted Earnings Per Share:
Diluted earnings (loss) per share	$ 0.23	[3]	$ 0.41	[3]	$ (0.01)	[3]	$ 0.36	[3]	$ (1.18)	[1]	$ (0.91)	[2],[3]	$ 0.18	[3]	$ 0.30	[3]	$ 1	$ (1.61)	$ 1.42
Enable Midstream Partners [Member]
Diluted Earnings Per Share:
Impairment Charges									$ 984		$ 862							$ 1,846
Impairment Charge, net of tax									$ 620		$ 537
[1]	CenterPoint Energy recognized $984 million ($620 million after tax) in impairment charges related to Enable during the three months ended December 31, 2015.
[2]	CenterPoint Energy recognized $862 million ($537 million after tax) in impairment charges related to Enable during the three months ended September 30, 2015.
[3]	Quarterly earnings (loss) per common share are based on the weighted average number of shares outstanding during the quarter, and the sum of the quarters may not equal annual earnings (loss) per common share.

Reportable Business Segments (D

Reportable Business Segments (Details) - USD ($) $ in Millions		3 Months Ended										12 Months Ended
		Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015		Sep. 30, 2015		Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenues from External Customers and Intersegment Revenues		$ 2,081	$ 1,889	$ 1,574	$ 1,984	$ 1,791	[1]	$ 1,630	[2]	$ 1,532	$ 2,433	$ 7,528	$ 7,386	$ 9,226
Depreciation and Amortization												1,126	970	1,013
Operating Income (Loss)		243	$ 284	$ 182	$ 250	226	[1]	265	[2]	$ 186	$ 256	959	933	935
Total Assets	[3]	21,829				21,290						21,829	21,290	23,150
Expenditures for Long-Lived Assets												1,406	1,575	1,402
Equity income												208	(1,633)	308
Enable Midstream Partners [Member]
Segment Reporting Information [Line Items]
Equity income	[4]											208	(1,633)	303
Impairment Charges						984		$ 862					1,846
Impairment of CenterPoint Energy’s equity method investment in Enable												0	1,225	0
Goodwill And Long-LIved Assets Impairment Charges, Entity's Share													621
Income (Loss) From Equity Method Investment, Excluding Impairment Charge													213
Southeast Supply Header LLC [Member]
Segment Reporting Information [Line Items]
Equity income	[5]											0	0	5
Electric Transmission & Distribution [Member]
Segment Reporting Information [Line Items]
Revenues from External Customers and Intersegment Revenues	[6]											3,060	2,845	2,845
Depreciation and Amortization												838	705	768
Operating Income (Loss)												628	607	595
Expenditures for Long-Lived Assets												858	934	818
Electric Transmission & Distribution [Member] | Affiliates of NRG Energy, Inc. [Member]
Segment Reporting Information [Line Items]
Revenues from External Customers and Intersegment Revenues												698	741	735
Electric Transmission & Distribution [Member] | Affiliates of Energy Future Holdings Corp. [Member]
Segment Reporting Information [Line Items]
Revenues from External Customers and Intersegment Revenues												220	220	189
Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Revenues from External Customers and Intersegment Revenues												2,380	2,603	3,271
Depreciation and Amortization												242	222	201
Operating Income (Loss)												303	273	287
Expenditures for Long-Lived Assets												510	601	525
Energy Services [Member]
Segment Reporting Information [Line Items]
Revenues from External Customers and Intersegment Revenues												2,073	1,924	3,095
Depreciation and Amortization												7	5	5
Operating Income (Loss)												20	42	52
Expenditures for Long-Lived Assets												5	5	3
Midstream Investments [Member]
Segment Reporting Information [Line Items]
Revenues from External Customers and Intersegment Revenues	[7]											0	0	0
Depreciation and Amortization	[7]											0	0	0
Operating Income (Loss)	[7]											0	0	0
Expenditures for Long-Lived Assets	[7]											0	0	0
Equity income												208	(1,633)	308
Midstream Investments [Member] | Enable Midstream Partners [Member]
Segment Reporting Information [Line Items]
Equity income	[8]											208	(1,633)	303
Midstream Investments [Member] | Southeast Supply Header LLC [Member]
Segment Reporting Information [Line Items]
Equity income												0	0	5
Other [Member]
Segment Reporting Information [Line Items]
Revenues from External Customers and Intersegment Revenues												15	14	15
Depreciation and Amortization												39	38	39
Operating Income (Loss)												8	11	1
Expenditures for Long-Lived Assets												33	35	56
Operating Segments [Member] | Electric Transmission & Distribution [Member]
Segment Reporting Information [Line Items]
Total Assets	[3]	10,211				10,028						10,211	10,028	10,041
Operating Segments [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Total Assets	[3]	6,099				5,657						6,099	5,657	5,464
Operating Segments [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Total Assets	[3]	1,102				857						1,102	857	978
Operating Segments [Member] | Midstream Investments [Member]
Segment Reporting Information [Line Items]
Total Assets	[3],[7]	2,505				2,594						2,505	2,594	4,521
Operating Segments [Member] | Other [Member]
Segment Reporting Information [Line Items]
Total Assets	[3],[9]	2,681				2,879						2,681	2,879	3,343
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues from External Customers and Intersegment Revenues												(55)	(62)	(114)
Total Assets	[3]	(769)				(725)						(769)	(725)	(1,197)
Intersegment Eliminations [Member] | Electric Transmission & Distribution [Member]
Segment Reporting Information [Line Items]
Revenues from External Customers and Intersegment Revenues												0	0	0
Intersegment Eliminations [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Revenues from External Customers and Intersegment Revenues												(29)	(29)	(30)
Intersegment Eliminations [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Revenues from External Customers and Intersegment Revenues												(26)	(33)	(84)
Intersegment Eliminations [Member] | Midstream Investments [Member]
Segment Reporting Information [Line Items]
Revenues from External Customers and Intersegment Revenues	[7]											0	0	0
Intersegment Eliminations [Member] | Other [Member]
Segment Reporting Information [Line Items]
Revenues from External Customers and Intersegment Revenues												0	0	0
Pension and Other Postretirement Plans Costs [Member] | Other [Member]
Segment Reporting Information [Line Items]
Total regulatory assets		$ 759				$ 814						$ 759	$ 814	$ 795
[1]	CenterPoint Energy recognized $984 million ($620 million after tax) in impairment charges related to Enable during the three months ended December 31, 2015.
[2]	CenterPoint Energy recognized $862 million ($537 million after tax) in impairment charges related to Enable during the three months ended September 30, 2015.
[3]	Amounts for 2015 and 2014 have been restated to reflect the adoption of ASU 2015-03.
[4]	These amounts include impairment charges totaling $1,846 million composed of CenterPoint Energy’s impairment of its equity method investment in Enable of $1,225 million and CenterPoint Energy’s share, $621 million, of impairment charges Enable recorded for goodwill and long-lived assets for the year ended December 31, 2015. This impairment is offset by $213 million of earnings for the year ended December 31, 2015.
[5]	CenterPoint Energy contributed a 24.95% interest in SESH to Enable on May 30, 2014 and its remaining 0.1% interest in SESH to Enable on June 30, 2015.
[6]	Houston Electric’s transmission and distribution revenues from major customers are as follows: Year Ended December 31, 2016 2016 2015 2014 (in millions)Affiliates of NRG $698 $741 $735Affiliates of Energy Future Holdings 220 220 189
[7]	Midstream Investments’ equity earnings (losses) are as follows: Year Ended December 31, 2016 2016 2015 2014 (in millions)Enable (a) $208 $(1,633) $303SESH — — 5 Total $208$(1,633)$308(a)These amounts include impairment charges totaling $1,846 million composed of CenterPoint Energy’s impairment of its equity method investment in Enable of $1,225 million and CenterPoint Energy’s share, $621 million, of impairment charges Enable recorded for goodwill and long-lived assets for the year ended December 31, 2015. This impairment is offset by $213 million of earnings for the year ended December 31, 2015.
[8]	These amounts include impairment charges totaling $1,846 million composed of CenterPoint Energy’s impairment of its equity method investment in Enable of $1,225 million and CenterPoint Energy’s share, $621 million, of impairment charges Enable recorded for goodwill and long-lived assets for the year ended December 31, 2015. This impairment is offset by $213 million of earnings for the year ended December 31, 2015.
[9]	Included in total assets of Other Operations as of December 31, 2016, 2015 and 2014, are pension and other postemployment related regulatory assets of $759 million, $814 million and $795 million, respectively.

Reportable Business Segments Re

Reportable Business Segments Revenues by Products and Services (Details) - USD ($) $ in Millions	3 Months Ended										12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	[1]	Sep. 30, 2015	[2]	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues by Products and Services:
Total	$ 2,081	$ 1,889	$ 1,574	$ 1,984	$ 1,791		$ 1,630		$ 1,532	$ 2,433	$ 7,528	$ 7,386	$ 9,226
Electric Delivery [Member]
Revenues by Products and Services:
Total											3,060	2,845	2,845
Retail Gas Sales [Member]
Revenues by Products and Services:
Total											3,329	3,725	5,049
Wholesale Gas Sales [Member]
Revenues by Products and Services:
Total											977	657	1,159
Gas Transportation and Processing [Member]
Revenues by Products and Services:
Total											23	26	38
Energy Products Or Services [Member]
Revenues by Products and Services:
Total											$ 139	$ 133	$ 135
[1]	CenterPoint Energy recognized $984 million ($620 million after tax) in impairment charges related to Enable during the three months ended December 31, 2015.
[2]	CenterPoint Energy recognized $862 million ($537 million after tax) in impairment charges related to Enable during the three months ended September 30, 2015.

Subsequent Events (Details)

Subsequent Events (Details) $ / shares in Units, $ in Millions	Feb. 10, 2017USD ($)$ / shares	Jan. 05, 2017$ / shares	Jan. 03, 2017USD ($)	Dec. 31, 2016USD ($)$ / shares	Dec. 31, 2015USD ($)$ / shares	Dec. 31, 2014USD ($)$ / shares
Subsequent Event [Line Items]
Quarterly Cash Dividend Declared | $ / shares				$ 1.03	$ 0.99	$ 0.95
Payments to Acquire Businesses, Gross				$ 102	$ 0	$ 0
Expected Cash Distribution				$ 319	$ 294	$ 305
Subsequent Event [Member]
Subsequent Event [Line Items]
Dividends Payable, Date Declared		Jan. 5, 2017
Quarterly Cash Dividend Declared | $ / shares		$ 0.2675
Dividends Payable, Date to be Paid		Mar. 10, 2017
Dividends Payable, Date of Record		Feb. 16, 2017
Subsequent Event [Member] | Enable Midstream Partners [Member]
Subsequent Event [Line Items]
Dividends Payable, Date Declared	Feb. 10, 2017
Quarterly Cash Dividend Declared | $ / shares	$ 0.318
Expected Cash Distribution	$ 74
Subsequent Event [Member] | Redeemable Preferred Stock [Member] | Enable Midstream Partners [Member]
Subsequent Event [Line Items]
Dividends Payable, Date Declared	Feb. 10, 2017
Preferred Stock, Dividends Per Share, Declared | $ / shares	$ 0.625
Cost Method Investment, Dividends Or Distributions	$ 9
Subsequent Event [Member] | Energy Services [Member]
Subsequent Event [Line Items]
Number of States in which Entity Operates			33
Number of States in which Entity Operates, No Prior Commercial or Industrial Customers			7
Number of States in which Entity Operates, Prior Other Operations			5
Subsequent Event [Member] | Atmos Energy Marketing [Member]
Subsequent Event [Line Items]
Business Acquisition, Effective Date of Acquisition			Jan. 3, 2017
Payments to Acquire Businesses, Gross			$ 140
Payments To Acquire Businesses, Adjustment For Working Capital			$ 100