Oncor Electric Delivery S-4 5 Apr 18 2017 FY Registration of securities issued in business combination transactions Financial data

Document and Entity Information

Document and Entity Information	12 Months Ended
	Dec. 31, 2017
Entity Registrant Name	ONCOR ELECTRIC DELIVERY CO LLC
Entity Central Index Key	1,193,311
Document Type	S4
Document Period End Date	Dec. 31, 2017
Amendment Flag	false
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Entity Filer Category	Non-accelerated Filer

Statements Of Consolidated Inco

Statements Of Consolidated Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating revenues:
Nonaffiliates	$ 3,958	$ 3,205	$ 2,923
Affiliates		715	955
Total operating revenues	3,958	3,920	3,878
Operating expenses:
Wholesale transmission service	929	894	802
Operation and maintenance (Note 12)	762	754	724
Depreciation and amortization	762	785	863
Provision in lieu of income taxes (Notes 1,4 and 12)	255	259	260
Taxes other than amounts related to income taxes	462	451	450
Total operating expenses	3,170	3,143	3,099
Operating income	788	777	779
Other income and (deductions) - net (Note 13)	(15)	(15)	(22)
Nonoperating provision in lieu of income taxes (Note 4)	12	(5)	(8)
Interest expense and related charges (Note 13)	342	336	333
Net income	$ 419	$ 431	$ 432

Statements Of Consolidated Comp

Statements Of Consolidated Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statements Of Consolidated Comprehensive Income [Abstract]
Net income	$ 419	$ 431	$ 432
Other comprehensive income (loss):
Cash flow hedges – derivative value net loss recognized in net income (net of tax expense of $1, $1 and $1) (Note 1)	2	2	2
Defined benefit pension plans (net of tax benefit of $4, $- and $4) (Note 10)	8		(8)
Total other comprehensive income (loss)	10	2	(6)
Comprehensive income	$ 429	$ 433	$ 426

Statements Of Consolidated Com4

Statements Of Consolidated Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statements Of Consolidated Comprehensive Income [Abstract]
Cash flow hedges - derivative value net loss recognized in net income, tax expense	$ 1	$ 1	$ 1
Defined benefit pension plans- net tax benefit	$ 4		$ 4

Statements Of Consolidated Cash

Statements Of Consolidated Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows - operating activities:
Net income	$ 419	$ 431	$ 432
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	815	833	908
Provision in lieu of deferred income taxes - net	309	181	40
Other - net	(2)	(4)	(4)
Changes in operating assets and liabilities:
Accounts receivable - trade (including affiliates)	(76)	(34)	12
Inventories	(1)	(7)	(8)
Accounts payable - trade (including affiliates)	(11)	14	(21)
Regulatory accounts related to reconcilable tariffs (Note 5)	29	(55)	11
Other - assets	54	37	22
Other - liabilities	(77)	33	(31)
Cash provided by operating activities	1,459	1,429	1,361
Cash flows - financing activities:
Issuances of long-term debt (Note 7)	600	175	725
Repayments of long-term debt (Note 7)	(324)	(41)	(639)
Net (decrease) increase in short-term borrowings (Note 6)	161	(51)	129
Distributions to members (Note 9)	(237)	(230)	(436)
Debt discount, premium, financing and reacquisition costs - net	(10)	10	(12)
Cash provided by (used in) financing activities	190	(137)	(233)
Cash flows - investing activities:
Capital expenditures (Note 12)	(1,631)	(1,352)	(1,154)
Business acquisition (Note 14)	(25)
Other - net	12	51	47
Cash used in investing activities	(1,644)	(1,301)	(1,107)
Net change in cash and cash equivalents	5	(9)	21
Cash and cash equivalents - beginning balance	16	25	4
Cash and cash equivalents - ending balance	$ 21	$ 16	$ 25

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 21	$ 16
Trade accounts receivable - net (Note 13)	635	545
Amounts receivable from members related to income taxes (Note 12)	26	80
Materials and supplies inventories - at average cost	91	89
Prepayments and other current assets	88	100
Total current assets	861	830
Investments and other property (Note 13)	113	100
Property, plant and equipment - net (Note 13)	14,879	13,829
Goodwill (Notes 1 and 13)	4,064	4,064
Regulatory assets (Note 5)	2,180	1,974
Other noncurrent assets	23	14
Total assets	22,120	20,811
Current liabilities:
Short-term borrowings (Note 6)	950	789
Long-term debt due currently (Note 7)	550	324
Trade accounts payable (Note 12)	242	231
Amounts payable to members related to income taxes (Note 12)	21	20
Accrued taxes other than amounts related to income	190	182
Accrued interest	83	83
Other current liabilities	188	144
Total current liabilities	2,224	1,773
Long-term debt, less amounts due currently (Note 7)	5,567	5,515
Liability in lieu of deferred income taxes (Notes 1, 4, and 12)	1,517	2,788
Regulatory liabilities (Note 5)	2,807	856
Employee benefit obligations and other (Notes 12 and 13)	2,102	2,168
Total liabilities	14,217	13,100
Commitments and contingencies (Note 8)
Membership interests (Note 9):
Capital account — number of interests outstanding 2017 and 2016 - 635,000,000	8,004	7,822
Accumulated other comprehensive loss	(101)	(111)
Total membership interests	7,903	7,711
Total liabilities and membership interests	$ 22,120	$ 20,811

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - shares	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidated Balance Sheets [Abstract]
Capital account, interests outstanding	635,000,000	635,000,000	635,000,000

Statements Of Consolidated Memb

Statements Of Consolidated Membership Interests - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Capital account:
Balance at beginning of period		$ 7,822		$ 7,621	$ 7,822	$ 7,621	$ 7,625
Net income	$ 77	73	$ 77	81	419	431	432
Distributions to members					(237)	(230)	(436)
Balance at end of period (number of interests outstanding: 2017, 2016 and 2015 – 635 million)	8,004		7,822		8,004	7,822	7,621
Accumulated other comprehensive income (loss) net of tax effects:
Balance at beginning of period		$ (111)		$ (113)	(111)	(113)	(107)
Net effects of cash flow hedges (net of tax expense of $1, $1 and $1)					2	2	2
Defined benefit pension plans (net of tax benefit of $4, $- and $4) (Note 10)					8		(8)
Balance at end of period	(101)		(111)		(101)	(111)	(113)
Total membership interests at end of period	$ 7,903		$ 7,711		$ 7,903	$ 7,711	$ 7,508

Statements Of Consolidated Mem9

Statements Of Consolidated Membership Interests (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statements Of Consolidated Membership Interest [Abstract]
Interests outstanding	635,000,000	635,000,000	635,000,000
Net effects of cash flow hedges, tax expense	$ 1	$ 1	$ 1
Defined benefit pension plans- net tax benefit	$ 4		$ 4

Description Of Business and Sig

Description Of Business and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Description Of Business and Significant Accounting Policies [Abstract]
Description Of Business and Significant Accounting Policies	1. DESCRIPTION OF BUSINESS AND SIGNIFICANT ACCOUNTING POLICIES  Description of Business  References in this report to “we,” “our,” “us” and “the company” are to Oncor and/or its subsidiary as apparent in the context. See “Glossary” for definition of terms and abbreviations.  We are a regulated electricity transmission and distribution company principally engaged in providing delivery services to REPs that sell power in the north-central, eastern and western parts of Texas. Revenues from subsidiaries of Vistra (formerly subsidiaries of TCEH) represented 22% , 23% and 25% of our total operating revenues for the years ended December 31, 2017, 2016 and 2015, respectively. We are a direct, majority-owned subsidiary of Oncor Holdings, which is a direct, wholly-owned subsidiary of EFIH, a direct, wholly-owned subsidiary of EFH Corp. EFH Corp. is a subsidiary of Texas Holdings, which is controlled by the Sponsor Group. Oncor Holdings owns 80.03% of our membership interests, Texas Transmission owns 19.75% of our membership interests and certain members of our management team and board of directors indirectly own the remaining membership interests through Investment LLC. We are managed as an integrated business; consequently, there are no separate reportable business segments.  Our consolidated financial statements include our former wholly-owned, bankruptcy-remote financing subsidiary, Bondco, a VIE through December 29, 2016, at which time it was dissolved (see Note 13) . This financing subsidiary was organized for the limited purpose of issuing certain transition bonds to recover generation-related regulatory asset stranded costs and other qualified costs under an order issued by the PUCT in 2002. Bondco issued an aggregate $1.3 billion principal amount of transition bonds during 2003 and 2004. The 2003 Series transition bonds matured and were paid in full in 2015 and the 2004 Series transition bonds matured and were paid in full in May 2016. Final true-up proceedings and refunds of over-collected transition charges for the transition bonds were conducted by Oncor and the PUCT during 2016 and had no material net income impact.  Various “ring-fencing” measures have been taken to enhance the separateness between the Oncor Ring-Fenced Entities and the Texas Holdings Group and our credit quality. These measures serve to mitigate our and Oncor Holdings’ credit exposure to the Texas Holdings Group and to reduce the risk that our assets and liabilities or those of Oncor Holdings would be substantively consolidated with the assets and liabilities of the Texas Holdings Group in connection with a bankruptcy of one or more of those entities, including the EFH Bankruptcy Proceedings discussed below. Such measures include, among other things: our sale of a 19.75% equity interest to Texas Transmission in November 2008; maintenance of separate books and records for the Oncor Ring-Fenced Entities; our board of directors being comprised of a majority of independent directors; and prohibitions on the Oncor Ring-Fenced Entities providing credit support to, or receiving credit support from, any member of the Texas Holdings Group. The assets and liabilities of the Oncor Ring-Fenced Entities are separate and distinct from those of the Texas Holdings Group. None of the assets of the Oncor Ring-Fenced Entities are available to satisfy the debt or contractual obligations of any member of the Texas Holdings Group. We do not bear any liability for debt or contractual obligations of the Texas Holdings Group, and vice versa. Accordingly, our operations are conducted, and our cash flows are managed, independently from the Texas Holdings Group.  In the PUCT proceedings requesting approval of the Sempra Acquisition (PUCT Docket No. 47675), Sempra has committed to certain ring-fencing measures that will be in effect upon closing of the Sempra Acquisition. For more information on the Sempra Acquisition and the related PUCT proceedings, see Note 2.  EFH Bankruptcy Proceedings  On the EFH Petition Date, EFH Corp. and the substantial majority of its direct and indirect subsidiaries at the time, including EFIH, EFCH and TCEH, commenced proceedings under Chapter 11 of the U.S. Bankruptcy Code. The Oncor Ring-Fenced Entities are not parties to the EFH Bankruptcy Proceedings. We believe the “ring-fencing” measures discussed above mitigate our potential exposure to the EFH Bankruptcy Proceedings. See Note 2 for a discussion of the potential impacts of the EFH Bankruptcy Proceedings on our financial statements.  Basis of Presentation  Our consolidated financial statements have been prepared in accordance with GAAP. All dollar amounts in the financial statements and tables in the notes are stated in millions of U.S. dollars unless otherwise indicated.  Use of Estimates  Preparation of our financial statements requires management to make estimates and assumptions about future events that affect the reporting of assets and liabilities at the balance sheet dates and the reported amounts of revenue and expense, including fair value measurements. In the event estimates and/or assumptions prove to be different from actual amounts, adjustments are made in subsequent periods to reflect more current information. No material adjustments were made to previous estimates or assumptions during the current year.  Revenue Recognition  General  Oncor’s revenu e is billed under tariffs approved by the PUCT and the majority of revenues are related to providing electric delivery service to consumers. Tariff rates are designed to recover the cost of providing electric delivery service including a reasonable rate of return on invested capital. Revenues are generally recognized when the underlying service has been provided in an amount prescribed by the related tariff.  Reconcilable Tariffs  The PUCT has designated certain tariffs (TCRF, EECRF surcharges, AMS surcharges and charges related to transition bonds) as reconcilable, which means the differences between amounts billed under these tariffs and the related incurred costs are deferred as either regulatory assets or regulatory liabilities. Accordingly, at prescribed intervals, future tariffs are adjusted to either repay regulatory liabilities or collect regulatory assets. See “Regulatory Assets and Liabilities” below.  Impairment of Long-Lived Assets and Goodwill  We evaluate long-lived assets (including intangible assets with finite lives) for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable.  We also evaluate goodwill for impairment annually (at December 1) and whenever events or changes in circumstances indicate that an impairment may exist. The determination of the existence of these and other indications of impairment involves judgments that are subjective in nature and may require the use of estimates in forecasting future results and cash flows.  If at the assessment date our carrying value exceeds our estimated fair value (enterprise value), then the estimated enterprise value is compared to the estimated fair values of our operating assets (including identifiable intangible assets) and liabilities at the assessment date. The resultant implied goodwill amount is compared to the recorded goodwill amount. Any excess of the recorded goodwill amount over the implied goodwill amount is written off as an impairment charge.  The goodwill impairment tests performed in 201 7 , 201 6 and 201 5 were based on a qualitative assessment in which we considered macroeconomic conditions, industry and market considerations, cost factors, overall financial performance and other relative factors . Based on tests results, no impairments were recognized in 201 7 , 201 6 or 201 5 .  Provision in Lieu of Income Taxes  Effective with the November 2008 sale of equity interests to Texas Transmission and Investment LLC, we became a partnership for U.S. federal income tax purposes, and subsequently we are not a member of EFH Corp.’s consolidated tax group and only EFH Corp.’s share of our partnership income is included in its consolidated federal income tax return. Our tax sharing agreement with Oncor Holdings and EFH Corp. was amended in November 2008 to include Texas Transmission and Investment LLC. The tax sharing agreement provides for the calculation of tax liability substantially as if we and Oncor Holdings were taxed as corporations, and requires tax payments to members determined on that basis (without duplication for any income taxes paid by a subsidiary of Oncor Holdings).  While partnerships are not subject to income taxes, in consideration of the tax sharing agreement and the presentation of our financial statements as an entity subject to cost-based regulatory rate-setting processes, with such costs including income taxes, the financial statements present amounts determined under the tax sharing agreement as “provision in lieu of income taxes” and “liability in lieu of deferred income taxes” for periods subsequent to the sales of equity interests discussed in Note 4. Such amounts are determined in accordance with the provisions of accounting guidance for income taxes and for uncertainty in income taxes and thus differences between the book and tax bases of assets and liabilities are accounted for as if we were taxed as a corporation. The accounting guidance for rate-regulated enterprises requires the recognition of regulatory assets or liabilities if it is probable such deferred tax -related amounts will be recovered from, or returned to customers in future rates. Investment tax credits are amortized to income over the estimated lives of the related properties.  We classify interest and penalties expense related to uncertain tax positions as current provision in lieu of income taxes as discussed in Note 4.  Defined Benefit Pension Plans and OPEB Plans  We have liabilities under pension plans that offer benefits based on either a traditional defined benefit formula or a cash balance formula and an OPEB plan that offers certain health care and life insurance benefits to eligible employees and their eligible dependents upon the retirement of such employees from the company. Costs of pension and OPEB plans are dependent upon numerous factors, assumptions and estimates. See Note 10 for additional information regarding pension and OPEB plans.  Contingencies  We evaluate and account for contingencies using the best information available. A loss contingency is accrued and disclosed when it is probable that an asset has been impaired or a liability incurred and the amount of the loss can be reasonably estimated. If a range of probable loss is established, the minimum amount in the range is accrued, unless some other amount within the range appears to be a better estimate. If the probable loss cannot be reasonably estimated, no accrual is recorde d, but the loss contingency is disclosed to the effect that the probable loss cannot be reasonably estimated. A loss contingency will be disclosed when it is reasonably possible that an asset has been impaired or a liability incurred. If the likelihood that an impairment or incurrence is remote, the contingency is neither accrued nor disclosed. Gain contingencies are recognized upon realization.  System of Accounts  Our accounting records have been maintained in accordance with the FERC Uniform System of Accounts as adopted by the PUCT.  Property, Plant and Equipment  Properties are stated at original cost. The cost of self-constructed property additions includes materials and both direct and indirect labor and applicable overhead and an allowance for funds used during construction.  D epreciation of property, plant and equipment is calculated on a straight-line basis over the estimated service lives of the properties based on depreciation rates approved by the PUCT. As is common in the industry, depreciation expense is recorded using composite depreciation rates that reflect blended estimates of the lives of major asset groups as compared to depreciation expense calculated on a component asset-by-asset basis. Depreciation rates include plant removal costs as a component of depreciation expense, consistent with regulatory treatment. Actual removal costs incurred are charged to accumulated depreciation. When accrued removal costs exceed incurred removal costs, the difference is reclassified as a regulatory liability to retire assets in the future.  Regulatory Assets and Liabilities  We are subject to rate regulation and o ur financial statements reflect regulatory assets and liabilities in accordance with accounting standards related to the effect of certain types of regulation. Regulatory assets and liabilities represent probable future revenues that will be recovered from or refunded to customers through the ratemaking process based on PURA and/or the PUCT’s orders, precedents or s ubstantive r ules. Rate regulation is premised on the full recovery of prudently incurred costs and a reasonable rate of return on invested capital subject to PUCT review for reasonableness and prudence and possible disallowance . Regulatory decisions can have an impact on the recovery of costs, the rate earned on invested capital and the timing and amount of assets to be recovered by rates. See Note 5 for more information regarding regulatory assets and liabilities.  Franchise Taxes  Franchise taxes are assessed to us by local governmental bodies, based on kWh delivered and are a principal component of taxes other than amounts related to income taxes as reported in the income statement. Franchise taxes are not a “pass through” item. The rates we charge customers are intended to recover the franchise taxes, but we are not acting as an agent to collect the taxes from customers.  Allowance for Funds Used During Construction (AFUDC)  AFUDC is a regulatory cost accounting procedu re whereby both interest charges on borrowed funds and a return on equity capital used to finance construction are included in the recorded cost of utility plant and equipment being constructed. AFUDC is capitalized on all projects involving construction periods lasting greater than thirty days. The equity portion, if any, of capitalized AFUDC is accounted for as other income. See Note 13 for detail of amounts charged to interest expense.  Cash and Cash Equivalents  For purposes of reporting cash and cash equivalents, temporary cash investments purchased with a remaining maturity of three months or less are considered to be cash equivalents.  Fair Value of Nonderivative Financial Instruments  The carrying amounts for financial assets classified as current assets and the carrying amounts for financial liabilities classified as current liabilities approximate fair value due to the short maturity of such instruments. The fair values of other financial instruments, for which carrying amounts and fair values have not been presented, are not materially different than their related carrying amounts. The following discussion of fair value accounting standards applies primarily to our determination of the fair value of assets in the pension and OPEB plans trusts (see Note 10) and long-term debt (see Note 7).  Accounting standards related to the determination of fair value define fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. We use a “mid-market” valuation convention (the mid-point price between bid and ask prices) as a practical expedient to measure fair value for the majority of our assets and liabilities subject to fair value measurement on a recurring basis. We primarily use the market approach for recurring fair value measurements and use valuation techniques to maximize the use of observable inputs and minimize the use of unobservable inputs.  We categorize our assets and liabilities recorded at fair value based upon the following fair value hierarchy:  · Level 1 valuations use quoted prices in active markets for identical assets or liabilities that are accessible at the measurement date. An active market is a market in which transactions for the asset or liability occur with sufficient frequency and volume to provide pricing information on an ongoing basis.  · Level 2 valuations use inputs that, in the absence of actively quoted market prices, are observable for the asset or liability, either directly or indirectly. Level 2 inputs include: (a) quoted prices for similar assets or liabilities in active markets , (b) quoted prices for identical or similar assets or liabilities in markets that are not active, (c) inputs other than quoted prices that are observable for the asset or liability such as interest rates and yield curves observable at commonly quoted intervals and (d) inputs that are derived principally from or corroborated by observable market data by correlation or other means. Our Level 2 valuations utilize over-the-counter broker quotes, quoted prices for similar assets or liabilities that are corroborated by correlations or other mathematical means and other valuation inputs.  · Level 3 valuations use unobservable inputs for the asset or liability. Unobservable inputs are used to the extent observable inputs are not available, thereby allowing for situations in which there is little, if any, market activity for the asset or liability at the measurement date. We use the most meaningful information available from the market combined with internally developed valuation methodologies to develop our best estimate of fair value.  We utilize several different valuation techniques to measure the fair value of assets and liabilities, relying primarily on the market approach of using prices and other market information for identical and/or comparable assets and liabilities for those items that are measured on a recurring basis.  The fair value of certain investments is measured using the net asset value (NAV) per share as a practical expedient. Such investments measured at NAV are not required to be categorized within the fair value hierarchy. See “Changes in Accounting Standards” below.  Consolidation of Variable Interest Entities  A VIE is an entity with which we have a relationship or arrangement that indicates some level of control over the entity or results in economic risks to us. We consolidate a VIE if we have: a) the power to direct the significant activities of the VIE and b) the right or obligation to absorb profit and loss from the VIE (primary beneficiary). See Note 13.  Derivative Instruments and Mark-to-Market Accounting  We have from time-to-time entered into derivative instruments to hedge interest rate risk. If the instrument meets the definition of a derivative under accounting standards related to derivative instruments and hedging activities, the fair value of each derivative is recognized on the balance sheet as a derivative asset or liability and changes in the fair value are recognized in net income, unless criteria for certain exceptions are met. This recognition is referred to as “mark-to-market” accounting. Changes in Accounting Standards  Since May 2014, the Financial Accounting Standards Board (FASB) has issued Accounting Standards Update (ASU) 2014-09, Revenue from Contracts with Customers along with other supplemental guidance (together, Topic 606). Topic 606 introduces new, increased requirements for disclosure of revenue in financial statements and guidance that are intended to eliminate inconsistencies in the recognition of revenue. We will add a revenue-related note to the financial statements to satisfy the new disclosure requirements of Topic 606. Topic 606 also requires the separate presentation of “alternative revenue program” revenues on the income statement. We anticipate less than $20 million annually in alternative revenue program revenues related to our energy efficiency program and will disclose such activity in the notes to financial statements. We are required to adopt Topic 606 effective January 1, 2018. We will adopt using the modified retrospective approach and will elect certain practical expedients available under the guidance. Our revenues from customers are tariff-based and are designed to recover the cost of providing electric delivery service to customers including a reasonable rate of return on invested capital. Revenues are generally recognized when the underlying service has been provided in an amount prescribed by the related tariff. The new guidance does not change this pattern of recognition and therefore the adoption will not have an effect on our reported results of operations, financial position or cash flows.  In February 2016, the FASB issued ASU 2016-02 which created FASB Topic 842, Leases (Topic 842) . Topic 842 amends previous GAAP to require the balance sheet recognition of lease assets and liabilities for operating leases. Operating lease liabilities will not be classified as debt for GAAP purposes under Topic 842 and will not be treated as debt for regulatory purposes. At this time, all of Oncor’s existing leases meet the definition of an operating lease liability. Under the new rules, the recognition of any finance leases (currently known as capital leases) on the balance sheet would be classified as debt for GAAP purposes and are expected to be defined as debt for our regulatory capital structure purposes (see Note 9 for details) similar to the current capital lease treatment. We will be required to adopt Topic 842 by January 1, 2019. We expect to adopt at that time using certain practical expedients available under the transition guidance including a practical expedient to not assess whether existing land easements that were not previously accounted for as leases are or contain a lease under Topic 842. The initial adoption of Topic 842 will affect our balance sheet, as leased buildings and vehicles are recognized as operating lease liabilities. Subsequent to adoption, to the extent Oncor enters into finance leases, its credit facility covenants and capitalization ratios could be impacted. We continue to compile a population of contracts for assessment and evaluate the potential impact of Topic 842 on our financial statements.  In March 2017, the FASB issued ASU 2017-07 Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost , an amendment to Topic 715, Compensation – Retirement Benefits (Topic 715). Topic 715, as amended, will require the non-service cost components of net retirement benefit plan costs be presented as non-operating in the income statement. In addition, only the service cost component of net retirement benefit plan cost will be eligible for capitalization as part of inventory or property, plant and equipment. We are required to adopt the amendment effective January 1, 2018. The income statement presentation requirement must be applied on a retrospective basis while the capitalization eligibility requirement is applied on a prospective basis. The guidance allows a practical expedient that permits use of previously disclosed service costs and non-service costs from the Pension and OPEB Plans note in the comparative periods as appropriate estimates when retrospectively changing the presentation of these costs in the income statements. We will elect this practical expedient. For cash flow purposes on a prospective basis, non-service costs will be reflected as a reduction to operating cash flows, o ffset by lo wer cash used in investing activities (lower capital expenditures). W e do not expect the new guidance to have a material effect on our rate-making process, our results of operations, financial position or net change in total cash flows but continue to evaluate for potential impacts.

EFH Bankruptcy Proceedings

EFH Bankruptcy Proceedings	12 Months Ended
	Dec. 31, 2017
EFH Bankruptcy Proceedings [Abstract]
EFH BANKRUPTCY PROCEEDINGS	2. EFH BANKRUPTCY PROCEEDINGS  On the EFH Petition Date, EFH Corp. and the substantial majority of its direct and indirect subsidiaries at the time, including E FIH, EFCH and TCEH, commenced proceedings under Chapter 11 of the U.S. Bankruptcy Code. The Oncor Ring-Fenced Entities are not parties to the EFH Bankruptcy Proceedings. We believe the “ring-fencing” measures discussed above mitigate our potential exposure to the EFH Bankruptcy Proceedings. See Note 1 and below for further information regarding the EFH Bankruptcy Proceedings and the proposed change in control of our indirect majority owner in connection with such proceedings.  The U.S. Bankruptcy Code automatically enjoined, or stayed, us from judicial or administrative proceedings or filing of other actions against our affiliates or their property to recover, collect or secure our claims arising prior to the EFH Petition Date. Following the EFH Petition Date, EFH Corp. received approval from the bankruptcy court to pay or otherwise honor certain prepetition obligations generally designed to stabilize its operations. Included in the approval were the obligations owed to us representing our prepetition electricity delivery fees. As of December 31, 2017, we had collected our prepetition receivables from the Texas Holdings Group of approximately $129 million.  In May 2016, the Debtors filed a joint Plan of Reorganization (2016 Plan of Reorganization) pursuant to Chapter 11 of the U.S. Bankruptcy Code and a related disclosure statement with the bankruptcy court. The 2016 Plan of Reorganization provided that the confirmation and effective date of the 2016 Plan of Reorganization with respect to the TCEH Debtors may occur separate from, and independent of, the confirmation and effective date of the 2016 Plan of Reorganization with respect to the EFH Debtors. In this regard, the bankruptcy court confirmed the 2016 Plan of Reorganization with respect to the TCEH Debtors in August 2016, and it became effective by its terms, and the spin-off of the TCEH Debtors from EFH Corp. (Vistra Spin-Off) occurred, effective October 3, 2016. As a result of the Vistra Spin-Off, Vistra and its subsidiaries, including Luminant and TXU Energy, ceased to be affiliates of ours as of October 3, 2016.  The EFH Bankruptcy Proceedings continue to be a complex litigation matter and the full extent of potential impacts on us remain unknown. Bankruptcy courts have broad equitable powers, and as a result, outcomes in bankruptcy proceedings are inherently difficult to predict. We will continue to evaluate our affiliate transactions and contingencies throughout the EFH Bankruptcy Proceedings to determine any risks and resulting impacts on our results of operations, financial statements and cash flows.  See Note 12 for details of Oncor’s related-party transactions with members of the Texas Holdings Group.  Potential Change in Indirect Ownership of Oncor  During the course of the EFH Bankruptcy Proceedings, certain plans of reorganization have been filed that contemplate the transfer of the ownership interests in Oncor that are indirectly held by EFH Corp. Below is a summary of certain matters relating to the potential change in indirect ownership of Oncor that have been proposed in the EFH Bankruptcy Proceedings .  Prior Merger Agreements  The following merger agreements relating to a potential change in indirect ownership of Oncor were entered into in connection with the EFH Bankruptcy Proceedings. Each of these prior merger agreements has been terminated in accordance with its respective terms.  · In August 2015, the EFH Debtors entered into a merger and purchase agreement (Hunt Merger Agreement) with an investor group consisting of certain unsecured creditors of TCEH and an affiliate of Hunt Consolidated, Inc., as well as certain other investors designated by Hunt Consolidated, Inc. (collectively, the Hunt Investor Group), that would have led to a significant change in the indirect equity ownership of Oncor . In August 2015, at the request of and with the consent of EFH Corp. and EFIH, Oncor and Oncor Holdings entered into a letter agreement (Hunt Letter Agreement) with the purchasers party to the Hunt Merger Agreement that described certain corporate actions Oncor and Oncor Holdings would take in connection with the merger contemplated by the Hunt Merger Agreement as well as conditions to Oncor’s and Oncor Holdings’ obligations to take those actions. In September 2015, Oncor and the Hunt Investor Group filed a joint application with the PUCT seeking certain regulatory approvals with respect to the transactions contemplated by the Hunt Merger Agreement. The PUCT issued an order conditionally approving the joint application in March 2016 and in April 2016 the Hunt Investor Group and certain intervenors filed motions for rehearing. As discussed under “PUCT Matters Related to the EFH Bankruptcy Proceedings – Hunt PUCT Proceedings” below, in May 2016, the PUCT denied the motions for rehearing in PUCT Docket No. 45188 and the Hunt Merger Agreement was terminated. The Hunt Letter Agreement was also terminated pursuant to its terms. In June 2016 the Hunt Investor Group filed a petition with the Travis County District Court seeking review of the PUCT order. We cannot predict the results of the review or the ultimate disposition of PUCT Docket No. 45188, particularly in light of the termination of the Hunt Merger Agreement.  · Following the termination of the Hunt Merger Agreement, in July 2016 EFH Corp. and EFIH entered into an Agreement and Plan of Merger (NEE Merger Agreement) with NextEra Energy, Inc. (NEE) and EFH Merger Co., LLC, a wholly-owned subsidiary of NEE, that provided for NEE’s acquisition of the equity interests in Oncor indirectly owned by EFH Corp. and EFIH. In addition, at the request of and with the consent of EFH Corp. and EFIH, on August 4, 2016, Oncor and Oncor Holdings entered into a letter agreement (NEE Letter Agreement) with NEE and EFH Merger Co., LLC that described certain corporate actions Oncor and Oncor Holdings would take in connection with the merger contemplated by the NEE Merger Agreement as well as conditions to Oncor’s and Oncor Holdings’ obligations to take those actions. Additionally, in October 2016, an affiliate of NEE entered into an Agreement and Plan of Merger (the TTI Merger Agreement) with Texas Transmission Holdings Corporation (TTHC), the parent of Texas Transmission, and certain of its affiliates to purchase Texas Transmission’s 19.75% equity interest in Oncor for approximately $2.4 billion. The bankruptcy court approved EFH Corp. and EFIH’s entry into the NEE Merger Agreement and related plan support agreement in September 2016 and confirmed an amended plan of reorganization in February 2017 (NEE Plan). The consummation of the transactions contemplated by the NEE Merger Agreement and related plan of reorganization and the TTI Merger Agreement was subject to various conditions precedent, including the approval of the PUCT. Oncor and NEE filed a joint application seeking certain regulatory approvals with respect to the NEE Merger Agreement and the TTI Merger Agreement in October 2016. The PUCT denied the application on April 13, 2017, issued an order on rehearing on June 7, 2017 re-affirming its decision that the proposed transaction was not in the public interest and denied NEE’s second motion for rehearing on June 29, 2017. Following these developments, on July 6, 2017, EFH and EFIH delivered a notice terminating the NEE Merger Agreement, which caused the NEE Plan to be null and void. The NEE Letter Agreement also terminated pursuant to its terms. As discussed under “PUCT Matters Related to the EFH Bankruptcy Proceedings” below, on July 13, 2017, NEE filed a petition with the Travis County District Court seeking review of the PUCT order (PUCT NEE Plan Order). We cannot assess the impact of the termination of the NEE Merger Agreement on the results of the review or ultimate disposition of the PUCT NEE Plan Order, or any associated impacts of such termination and matters relating to the PUCT NEE Plan Order on the TTI Merger Agreement and the transactions contemplated thereby. For more information regarding the TTI Merger Agreement and its related regulatory proceedings, see under “PUCT Matters Related to the EFH Bankruptcy Proceedings –NEE PUCT Proceedings” below.  · Following the termination of the NEE Merger Agreement, on July 7, 2017, EFH Corp. and EFIH executed a merger agreement (BHE Merger Agreement) with Berkshire Hathaway Energy Company (BHE) and certain of its subsidiaries. The BHE Merger Agreement provided for the acquisition by BHE of the 80.03% of Oncor’s membership interests owned indirectly by EFH Corp. and EFIH. In connection with the execution of the BHE Merger Agreement, on July 7, 2017, the EFH Debtors filed a joint plan of reorganization (BHE Plan) and a related disclosure statement. In addition, at the request of and with the consent of EFH Corp. and EFIH, on July 7, 2017, Oncor and Oncor Holdings entered into a letter agreement (BHE Letter Agreement) with BHE and its subsidiaries that were party to the BHE Merger Agreement that described certain corporate actions Oncor and Oncor Holdings would take in connection with the merger contemplated by the BHE Merger Agreement as well as conditions to Oncor’s and Oncor Holdings’ obligations to take those actions. The EFH Debtors terminated the BHE Merger Agreement on August 21, 2017 in connection with their entry into the Sempra Merger Agreement (as defined and discussed below), which caused the BHE Plan to become null and void. The BHE Letter Agreement also terminated pursuant to its terms. Further, by order dated September 7, 2017, the bankruptcy court ordered that the BHE Merger Agreement was terminated and not approved.  Sempra Merger Agreement  On August 15, 2017, the EFH Debtors received an alternative proposal from Sempra Energy (Sempra) that largely followed the structure of the BHE Plan. Following negotiations, on August 21, 2017, EFH Corp. and EFIH entered into an Agreement and Plan of Merger (Sempra Merger Agreement) with Sempra and one of its wholly-owned subsidiaries (collectively, the Sempra Parties). Pursuant to the Sempra Merger Agreement, EFH Corp. will be merged with an indirect subsidiary of Sempra, with EFH Corp. continuing as the surviving company and an indirect, wholly-owned subsidiary of Sempra. The Sempra Merger Agreement does not impose any conditions on the EFH Debtors regarding TTI’s minority interest in Oncor. Accordingly, the Sempra Merger Agreement provides for the acquisition by Sempra of the 80.03% of Oncor’s membership interests owned indirectly by EFH Corp. and EFIH (Sempra Acquisition).  Following the execution and delivery of the Sempra Merger Agreement, EFIH requested, pursuant to the Sempra Merger Agreement, that Oncor Holdings and Oncor enter into a letter agreement (Sempra Letter Agreement) with the Sempra Parties. The Sempra Letter Agreement was executed on August 25, 2017 and sets forth certain rights and obligations of the Oncor Ring-Fenced Entities and the Sempra Parties to cooperate in the manner set forth therein with respect to initial steps to be taken in connection with the acquisition of Reorganized EFH and the other transactions described in the Sempra Merger Agreement. Pursuant to the terms of the Sempra Letter Agreement, the Oncor Ring-Fenced Entities are to conduct, in all material respects, their businesses in the ordinary course of business and materially consistent with the plan for 2017 and 2018 contained in Oncor’s long-range business plan. The Sempra Letter Agreement also provides that the Oncor Ring-Fenced Entities will cooperate with the Sempra Parties to prepare and file all necessary applications for governmental approvals of the transactions contemplated by the Sempra Merger Agreement, including PUCT and FERC approvals. The Sempra Letter Agreement is not intended to give the Sempra Parties, directly or indirectly, the right to control or direct the operations of any of the Oncor Ring-Fenced Entities.  Closing Conditions to the Sempra Merger Agreement  The Sempra Merger Agreement is subject to customary closing conditions, including the approval of the bankruptcy court in the EFH Bankruptcy Proceedings, Federal Communications Commission and the PUCT. Certain conditions, such as approval from FERC, the Vermont Department of Financial Regulation and receipt of a private letter ruling from the IRS have already been satisfied.  In connection with the execution of the Sempra Merger Agreement, on September 5, 2017, the EFH Debtors filed an amended joint plan of reorganization (Sempra Plan) and a related disclosure statement (Sempra Disclosure Statement). On September 6, 2017, the bankruptcy court authorized the EFH Debtors’ entry into the Sempra Merger Agreement, approved the Sempra Disclosure Statement and authorized the EFH Debtors to solicit votes on the Sempra Plan. By declaration submitted on November 1, 2017, the EFH Debtors certified that they had received sufficient votes to confirm the Sempra Plan. The hearing on confirmation of the Sempra Plan is scheduled to begin on February 26, 2018 in the bankruptcy court.  Pursuant to the terms of the Sempra Merger Agreement, Oncor and Sempra filed a joint application with the PUCT seeking certain regulatory approvals with respect to the transactions contemplated by the Sempra Plan on October 5, 2017 in PUCT Docket No. 47675. On December 14, 2017, Oncor and Sempra entered into a stipulation with the Staff of the PUCT, the Office of Public Utility Counsel, the Steering Committee of Cities Served by Oncor and the Texas Industrial Energy Consumers reflecting the parties’ settlement of all issues in the PUCT proceeding regarding the joint application. On January 5, 2018, Oncor, Sempra and the Staff of the PUCT made a joint filing with the PUCT requesting that the PUCT approve the acquisition, consistent with the governance, regulatory and operating commitments in a revised stipulation joined by two additional parties. On January 23, 2018, Oncor and Sempra filed an additional revision to the revised stipulation (Sempra Settlement Stipulation) and announced that two more parties had joined in the Sempra Settlement Stipulation. On February 2, 2018, Oncor and Sempra announced that all of the intervenors in PUCT Docket No. 47675 had signed on to the Sempra Settlement Stipulation. At its February 15, 2018 open meeting, the PUCT directed PUCT Staff to prepare an order based on the Sempra Settlement Stipulation for consideration by the PUCT at its open meeting on March 8, 2018. We cannot predict what the form of any final order will be or the ultimate disposition in the PUCT docket. For more information regarding the Sempra Settlement Stipulation and the proceedings in PUCT Docket No. 47675, see “PUCT Matters Relating to EFH Bankruptcy Proceedings – Sempra PUCT Proceedings” below.  We cannot predict the ultimate outcome of the EFH Bankruptcy Proceedings, including whether the Sempra Acquisition will (or when it will) close. There remain conditions and uncertainties relating to the confirmation of the Sempra Plan and it becoming effective and the consummation of the transactions contemplated by the Sempra Merger Agreement, including, without limitation, the ability to obtain required bankruptcy court approvals as well as the required regulatory approvals from the PUCT, as described below under “PUCT Matters Related to EFH Bankruptcy Proceedings.” As a result, we remain unable to predict how any reorganization of the EFH Debtors and the related matters ultimately will impact Oncor or what form any change in indirect ownership of Oncor may take. Assuming that all approvals are received, we currently expect that the Sempra Acquisition will close in the first half of 2018, although there can be no assurance that the Sempra Acquisition will be completed on that timetable, or at all.  PUCT Matters Related to EFH Bankruptcy Proceedings  Hunt Investor Group PUCT Proceedings  In September 2015, Oncor and the Hunt Investor Group filed in PUCT Docket No. 45188 a joint application with the PUCT seeking certain regulatory approvals with respect to the transactions contemplated by a plan of reorganization in the EFH Bankruptcy Proceedings. In March 2016, the PUCT issued an order conditionally approving the joint application. In April 2016, the Hunt Investor Group and certain intervenors in PUCT Docket No. 45188 filed motions for rehearing and in May 2016, the PUCT denied such motions and the order became final. In May 2016, the plan of reorganization and the Hunt Merger Agreement that contemplated the transactions in PUCT Docket No. 45188 were terminated. The Hunt Investor Group filed a petition with the Travis County District Court in June 2016 seeking review of the order. We cannot predict the results of the review or the ultimate disposition of PUCT Docket No. 45188, particularly in light of the termination of the Hunt Merger Agreement.  In connection with PUCT Docket No. 45188, certain cities that have retained original jurisdiction over electric utility rates passed resolutions directing Oncor to file rate review proceedings. Oncor made a rate filing with the PUCT and original jurisdiction cities to comply with their resolutions on March 17, 2017 in PUCT Docket No. 46957. In July 2017, we and certain parties to our rate review agreed to a settlement of that rate review, and on August 2, 2017 a settlement agreement was filed that settled all issues in the docket. On October 13, 2017, the PUCT issued an order approving the settlement agreement, and on November 26, 2017, the new rates took effect. For more information, see Note 3 – “2017 Rate Review (PUCT Docket No. 46957).”  NEE PUCT Proceedings  The NEE Merger Agreement contemplated that Oncor and NEE file a joint application with the PUCT seeking certain regulatory approvals with respect to the transactions contemplated by the NEE Merger Agreement. Oncor and NEE filed that joint application in PUCT Docket No. 46238 in October 2016. The PUCT denied the application on April 13, 2017. The PUCT issued an order on rehearing on June 7, 2017 and denied NEE’s second motion for rehearing on June 29, 2017. On July 13, 2017, NEE filed a petition with the Travis County District Court seeking review of the PUCT order. We cannot predict the results of the review or the ultimate disposition of PUCT Docket No. 46238, particularly in light of the termination of the NEE Merger Agreement.  On July 28, 2017, TTHC and NEE filed in PUCT Docket No. 47453 a joint application with the PUCT seeking certain regulatory approvals with respect to NEE’s proposed acquisition of the 19.75% minority interest in Oncor that is indirectly held by TTHC. The application requested that the PUCT issue an order disclaiming jurisdiction over the transaction or finding that the transaction is in the public interest and approved. On September 14, 2017, Oncor filed a motion to intervene as a party, but not as an applicant, in PUCT Docket No. 47453. On October 26, 2017, the PUCT voted to dismiss the application without prejudice on jurisdictional grounds and ordered that any future filing of the application must include the affected utility (in this case Oncor) as an applicant. The PUCT further ordered that in any such filing Oncor is not required to seek approval of the application or any other specific relief. On October 31, 2017, TTHC notified the PUCT that it had terminated the TTI Merger Agreement with NEE. NEE filed a motion for rehearing on November 20, 2017, which was not granted. On January 9, 2018, NEE filed a petition with the Travis County District Court seeking review of the PUCT order of dismissal. We cannot predict the results of the review or the ultimate disposition of PUCT Docket No. 47453, particularly in light of TTHC’s termination of the TTI Merger Agreement.  Sempra PUCT Proceedings  Oncor and Sempra filed a joint application with the PUCT seeking certain regulatory approvals with respect to the transactions contemplated by the Sempra Plan on October 5, 2017 in PUCT Docket No. 47675. On December 14, 2017, Oncor and Sempra entered into a stipulation with the Staff of the PUCT, the Office of Public Utility Counsel, the Steering Committee of Cities Served by Oncor and the Texas Industrial Energy Consumers reflecting the parties’ settlement of all issues in the PUCT proceeding regarding the joint application. On January 5, 2018, Oncor, Sempra and the Staff of the PUCT made a joint filing with the PUCT requesting that the PUCT approve the acquisition, consistent with the governance, regulatory and operating commitments in a revised stipulation joined by two additional parties. On January 23, 2018, Oncor and Sempra filed an additional revision to the revised stipulation (Sempra Settlement Stipulation) and announced that two more parties had joined in the Sempra Settlement Stipulation. On February 2, 2018, Oncor and Sempra announced that all of the intervenors in PUCT Docket No. 47675 had signed on to the Sempra Settlement Stipulation. At its February 15, 2018 open meeting, the PUCT directed PUCT Staff to prepare an order based on the Sempra Settlement Stipulation for consideration by the PUCT at its open meeting on March 8, 2018. We cannot predict what the form of any final order will be or the ultimate disposition in the PUCT docket.  T he parties to the Sempra Settlement Stipulation have agreed that Sempra’s acquisition of EFH Corp. is in the public interest and will bring substantial benefits. The Sempra Settlement Stipulation requests that the PUCT approve the Sempra Acquisition. Previously, EFH Corp. and Oncor implemented various ring-fencing measures to enhance Oncor’s separateness from its owners and to mitigate the risk that Oncor would be negatively impacted in the event of a bankruptcy or other adverse financial developments affecting EFH Corp. or EFH Corp.’s subsidiaries or owners. The existing ring-fencing measures are designed to create both legal and financial separation between the Oncor Ring-Fenced Entities, on the one hand, and EFH Corp. and its other affiliates and subsidiaries, on the other hand. The joint application filed with the PUCT and the Sempra Settlement Stipulation outline certain ring-fencing measures, governance mechanisms and restrictions that will apply after the Sempra Acquisition. As a result of these ring-fencing measures, Sempra will not control Oncor, and the ring-fencing measures limit Sempra’s ability to direct the management, policies and operations of Oncor, including the deployment or disposition of Oncor’s assets, declarations of dividends, strategic planning and other important corporate issues and actions. These limitations include limited representation on the board of directors of Oncor.  Pursuant to the Sempra Settlement Stipulation, if the Sempra Acquisition is consummated, the board of directors of Oncor is expected to consist of thirteen members and be constituted as follows: · seven members, which we refer to as disinterested directors, will be (i) independent directors in all material respects under the rules of the New York Stock Exchange in relation to Sempra and its subsidiaries and affiliated entities and any entity with a direct or indirect ownership interest in Oncor or Oncor Holdings, and (ii) will have no material relationship with Sempra or its affiliates or any entity with a direct or indirect ownership interest in Oncor or Oncor Holdings at the time of the Sempra Acquisition or within the previous ten years; · two members will be designated by Sempra; · two members will be appointed by Texas Transmission; and · two members will be current or former officers of Oncor (the Oncor Officer Directors), initially Robert S. Shapard and E. Allen Nye, Jr., who no later than the closing of the Sempra Acquisition will be the chair of the Oncor board and chief executive officer of Oncor, respectively.  In order for a current or former officer of Oncor to be eligible to serve as an Oncor Officer Director, such officer cannot have worked for Sempra or any of its affiliates (excluding Oncor Holdings and Oncor) or any other entity with a direct or indirect ownership interest in Oncor or Oncor Holdings in the ten year period prior to such officer being employed by Oncor. Oncor Holdings, at the direction of EFIH (a subsidiary of EFH, which will be a wholly owned indirect subsidiary of, and controlled by, Sempra following the Sempra Acquisition), will have the right to nominate and/or seek the removal of the Oncor Officer Directors, with such nomination or removal subject to approval by a majority of the Oncor board of directors.  In addition, the Sempra Settlement Stipulation provides that Oncor’s board cannot be overruled by the board of Sempra or any of its subsidiaries on dividend policy, the issuance of dividends or other distributions (except for contractual tax payments), debt issuance, capital expenditures, operation and maintenance expenditures, management and service fees, and appointment or removal of board members, provided that certain actions may also require the additional approval of the Oncor Holdings board of directors. The Sempra Settlement Stipulation also provides that any changes to the size, composition, structure or rights of the board must first be approved by the PUCT. In addition, if Sempra acquires Texas Transmission’s interest in Oncor, the Sempra Settlement Agreement provides that the two board positions on Oncor’s board of directors that Texas Transmission is entitled to appoint shall be eliminated and the size of Oncor’s board of directors will be reduced by two.  Additional regulatory commitments, governance mechanisms and restrictions provided in the Sempra Settlement Stipulation include, among others:  · A majority of the disinterested directors of Oncor must approve any annual or multi-year budget if the aggregate amount of capital expenditures or operating and maintenance expenditures in such budget is more than a 10% increase or decrease from the corresponding amounts of such expenditures in the budget for the preceding fiscal year or multi-year period, as applicable;  · Oncor will make minimum aggregate capital expenditures equal to at least $7.5 billion over the period from January 1, 2018 through December 31, 2022 (subject to certain possible adjustments);  · Sempra has agreed to make, within 60 days after the Sempra Acquisition, its proportionate share of the aggregate equity investment in Oncor in an amount necessary for Oncor to achieve a capital structure consisting of 57.5% long-term debt to 42.5% equity, as calculated for regulatory purposes (until recently, Oncor’s regulatory capital structure required 40% equity, with the remaining 60% as debt);  · Oncor may not pay any dividends or make any other distributions (except for contractual tax payments) if a majority of its disinterested directors determines that it is in the best interests of Oncor to retain such amounts to meet expected future requirements;  · At all times, Oncor will remain in compliance with the debt-to-equity ratio established by the PUCT from time to time for ratemaking purposes, and Oncor will not pay dividends or other distributions (except for contractual tax payments), if that payment would cause its debt-to-equity ratio to exceed the debt-to-equity ratio approved by the PUCT;  · Sempra will ensure that, as of the closing of the Sempra Acquisition, Oncor’s credit rating by all three major rating agencies will be at or above Oncor’s credit ratings as of June 30, 2017;  · If the credit rating on Oncor’s senior secured debt by any of the three major rating agencies falls below BBB (or the equivalent), Oncor will suspend dividends and other distributions (except for contractual tax payments), unless otherwise allowed by the PUCT;  · Without the prior approval of the PUCT, neither Sempra nor any of its affiliates (excluding Oncor) will incur, guaranty or pledge assets in respect of any indebtedness that is dependent on the revenues of Oncor in more than a proportionate degree than the other revenues of Sempra or on the stock of Oncor, and there will be no debt at EFH Corp. or EFIH at any time following the closing of the Sempra Acquisition;  · Neither Oncor nor Oncor Holdings will lend money to or borrow money from Sempra or any of its affiliates (other than Oncor subsidiaries), or any entity with a direct or indirect ownership interest in Oncor or Oncor Holdings, and neither Oncor nor Oncor Holdings will share credit facilities with Sempra or any of its affiliates (other than Oncor subsidiaries), or any entity with a direct or indirect ownership interest in Oncor or Oncor Holdings;  · Oncor will not seek recovery in rates of any expenses or liabilities related to EFH Corp.’s bankruptcy, or (1) any tax liabilities resulting from the Vistra Spin-Off, (2) any asbestos claims relating to non-Oncor operations of EFH Corp. or (3) any make-whole claims by holders of debt securities issued by EFH Corp. or EFIH, and Sempra must file with the PUCT a plan providing for the extinguishment of the liabilities described in items (1) through (3) above, which protects Oncor from any harm;  · There must be maintained certain “separateness measures” that reinforce the financial separation of Oncor from EFH Corp. and EFH Corp.’s owners, including a requirement that dealings between Oncor, Oncor Holdings and their subsidiaries with Sempra, any of Sempra’s other affiliates or any entity with a direct or indirect ownership interest in Oncor or Oncor Holdings, must be on an arm’s-length basis, limitations on affiliate transactions, separate recordkeeping requirements and a prohibition on pledging Oncor assets or stock for any entity other than Oncor;  · No transaction costs or transition costs related to the Sempra Acquisition (excluding Oncor employee time) will be borne by Oncor’s customers nor included in Oncor’s rates;  · Sempra will continue to hold indirectly at least 51% of the ownership interests in Oncor and Oncor Holdings for at least five years following the closing of the Sempra Acquisition, unless otherwise specifically authorized by the PUCT; and  · Oncor will provide bill credits to electric delivery rates for ultimate credits to customers in an amount equal to 90% of any interest rate savings achieved due to any improvement in its credit ratings or market spreads compared to those as of June 30, 2017 until final rates are set in the next Oncor base rate case filed after PUCT Docket No. 46957 (except that savings will not be included in credits if already realized in rates); and one year after the Sempra Acquisition, Oncor will provide bill credits to electric delivery rates for inclusion in customer bills equal to 90% of any synergy savings until final rates are set in the next Oncor base rate proceeding after PUCT Docket No. 46957, at which time any total synergy savings shall be reflected in Oncor’s rates.  If the PUCT does not accept the Sempra Settlement Stipulation as presented, or issues an order inconsistent with the terms of the stipulation, the parties have agreed that any party adversely affected by the alteration has the right to withdraw from the stipulation and to exercise all rights available to such party under the law.  We cannot predict the results of the review or the ultimate disposition of PUCT Docket No. 47675.  EFH Bankruptcy Proceedings Settlement Agreement  In connection with the EFH Bankruptcy Proceedings, the EFH Debtors and various creditor parties entered into a settlement agreement (the Settlement Agreement) in August 2015 (as amended in September 2015) to compromise and settle, among other things (a) intercompany claims among the EFH Debtors, (b) claims and causes of actions against holders of first lien claims against TCEH and the agents under TCEH’s senior secured facilities, (c) claims and causes of action against holders of interests in EFH Corp. and certain related entities and (d) claims and causes of action against each of the EFH Debtors’ current and former directors, the Sponsor Group, managers and officers and other related entities. The Settlement Agreement contemplates a release of such claims upon approval of the Settlement Agreement by the bankruptcy court, which approval was obtained in December 2015. The Settlement Agreement settles substantially all inter-debtor claims through the effective date of the Settlement Agreement. These settled claims include potentially contentious inter-debtor claims, including various potential avoidance actions and claims a

Regulatory Matters

Regulatory Matters	12 Months Ended
	Dec. 31, 2017
Regulatory Matters [Abstract]
REGULATORY MATTERS	3. REGULATORY MATTERS  Change in Control Reviews  See “PUCT Matters Related to EFH Bankruptcy Proceedings” in Note 2.  2017 Rate Review (PUCT Docket No. 46957)  In July 2017, we and certain parties to our rate review agreed to a settlement of that rate review, and on August 2, 2017 a settlement agreement was filed with the PUCT that settled all issues in the docket. On October 13, 2017, the PUCT issued an order approving the settlement of the rate review, subject to closing of the Sharyland Asset Exchange, which closed on November 9, 2017. As a result of the Sharyland Asset Exchange closing on November 9, 2017, the contingency in the PUCT order in PUCT Docket No. 46957 was met and our new rates as set forth in that order took effect on November 27, 2017. As a result of the PUCT order, our annual distribution and transmission base rate revenues, net of eliminations, are expected to increase approximatel y $65 m illion excluding the impacts of the Sharyland Asset Exchange and the TCJA. The order also requires us to record as a regulatory liability, instead of revenue, the amount that we collect through our approved tariffs for federal income taxes that is above the new corporate federal income rate. We estimate that incorporating the new corporate federal income tax rate in our approved rate settlement agreement would have reduced our annual revenues and our tax expense by approximately $125 million. Other significant findings include a change in our authorized return on equity to 9.80% and a change in our authorized regulatory capital structure to 57.5% debt to 42.5% equity. Our previous authorized return on equity was 10.25% and our previous authorized regulatory capital structure was 60% debt to 40% equity. The PUCT order in PUCT Docket No. 46957 requires us to record a regulatory liability until the new authorized regulatory capital structure is met to reflect our actual capitalization prior to achieving the authorized capital structure. Once the authorized capital structure is attained, the regulatory liability will be returned to customers through the capital structure refund mechanism approved in the PUCT docket. We implemented the regulatory liability as of November 27, 2017.  Sharyland Asset Exchange (PUCT Docket No. 47469)  On July 21, 2017, we entered into the Sharyland Agreement with the Sharyland Entities. The Sharyland Agreement provided that we would exchange certain of our transmission assets and cash certain of the Sharyland Entities’ distribution assets (constituting substantially all of their electricity distribution business) and certain of their transmission assets. The transaction for assets between us and SDTS was structured to qualify, in part, as a simultaneous tax deferred like kind exchange of assets to the extent that the assets exchanged are of “like kind” (within the meaning of Section 1031 of the Internal Revenue Code of 1986 (as amended, the Code)).  On August 4, 2017, we , SDTS and SU filed a joint application for sale, transfer, or merger in PUCT Docket No. 47469 requesting PUCT approvals of the Sharyland Asset Exchange, and on October 13, 2017, the PUCT issued an order approving the transactions. On November 9, 2017, the parties consummated the transactions. We exchanged approximately $383 million of our transmission assets, consisting of 517 circuit miles of 345 kV transmission lines, and approximately $25 million in cash for approximately $408 million of the Sharyland Entities’ distribution assets (constituting substantially all of their electricity distribution business) and certain of their transmission assets. We do not expect the Sharyland transaction will have a material effect on our results of operations, financial position or cash flows. For more information on the Sharyland Agreement and the Sharyland Asset Exchange, see Note 14 to Financial Statements.  2008 Rate Review (PUCT Docket No. 35717)  In August 2009, the PUCT issued a final order with respect to our June 2008 rate review filing with the PUCT and 204 cities based on a test year ended December 31, 2007 (PUCT Docket No. 35717), and new rates were implemented in September 2009. We and four other parties appealed various portions of the rate review final order to a state district court. In January 2011, the district court signed its judgment reversing the PUCT with respect to two issues: the PUCT’s disallowance of certain franchise fees and the PUCT’s decision that PURA no longer requires imposition of a rate discount for state colleges and universities. We filed an appeal with the Texas Third Court of Appeals (Austin Court of Appeals) in February 2011 with respect to the issues we appealed to the district court and did not prevail upon, as well as the district court’s decision to reverse the PUCT with respect to discounts for state colleges and universities. In early August 2014, the Austin Court of Appeals reversed the district court and affirmed the PUCT with respect to the PUCT’s disallowance of certain franchise fees and the PUCT’s decision that PURA no longer requires imposition of a rate discount for state colleges and universities. The Austin Court of Appeals also reversed the PUCT and district court’s rejection of a proposed consolidated tax savings adjustment arising out of EFH Corp.’s ability to offset our taxable income against losses from other investments and remanded the issue to the PUCT to determine the amount of the consolidated tax savings adjustment. In late August 2014, we filed a motion on rehearing with the Austin Court of Appeals with respect to certain appeal issues on which we were not successful, including the consolidated tax savings adjustment. In December 2014, the Austin Court of Appeals issued its opinion, clarifying that it was rendering judgment on the rate discount for state colleges and universities issue (affirming that PURA no longer requires imposition of the rate discount) rather than remanding it to the PUCT, and dismissing the motions for rehearing regarding the franchise fee issue and the consolidated tax savings adjustment. We filed a petition for review with the Texas Supreme Court in February 2015. The Texas Supreme Court granted the petition for review and heard oral arguments in September 2016. On January 6, 2017, the Texas Supreme Court issued its opinion, unanimously ruling as follows on the three issues before it:  · Consolidated tax savings adjustment - The Supreme Court reversed the Court of Appeals and upheld the PUCT’s decision not to make a consolidated tax savings adjustment, concluding that the PUCT had properly applied PURA Section 36.060 and that we no longer met the statutory criteria for imposition of such an adjustment.  · State colleges and universities rate discount - The Supreme Court upheld the Court of Appeals’ and the PUCT’s decisions that no such discount was proper, concluding that PURA Section 36.351 requires a discount only for the provision of electric service and that, upon the start of retail competition, electric service is provided to end-use customers by REPs and not TDUs.  · Municipal franchise fees - The Supreme Court reversed the Court of Appeals’ and the PUCT’s disallowance of certain franchise fees, ruling that the relevant PURA provision did not limit negotiated franchise fees to a one-time opportunity upon the expiration of a franchise that was in effect on September 1, 1999, but that such renegotiations may take place at any time.  The Texas Supreme Court issued its mandate on February 16, 2017. On February 17, 2017, we filed a tariff modification with the PUCT to immediately remove the state colleges and universities discount rider, and on February 23, 2017, the PUCT opened Docket No. 46884 to consider the remand from the Texas Supreme Court. The Docket No. 46957 rate review order granted the recovery of the municipal franchise fees through a surcharge over approximately nine months beginning November 27, 2017.  We are involved in various other regulatory proceedings in the normal course of business, the ultimate resolution of which, in the opinion of management, should not have a material effect upon our financial position, results of operations or cash flows. 

Provision In Lieu Of Income Tax

Provision In Lieu Of Income Taxes	12 Months Ended
	Dec. 31, 2017
Provision In Lieu Of Income Taxes [Abstract]
PROVISION IN LIEU OF INCOME TAXES	4. PROVISION IN LIEU OF I NCOME TAXES  Tax Cuts and Jobs Act (TCJA)  On December 22, 2017, President Trump signed the TCJA into law . Substantially all of the provisions of the TCJA are effective for our taxable years beginning January 1, 2018. The TCJA includes significant changes to the Code, including amendments which significantly change the taxation of business entities and includes specific provisions related to regulated public utilities such as Oncor. The most significant TCJA change that impacts us is the reduction in the corporate federal income tax rate from 35% to 21% . The specific provisions related to regulated public utilities in the TCJA applicable to us include the continued deductibility of interest expense, the elimination of bonus depreciation on certain property acquired after September 27, 2017 and certain rate normalization requirements for accelerated depreciation benefits.  Changes in the Code from the TCJA had a material impact on our financial statements in 2017. Under GAAP, specifically ASC Topic 740, Income Taxes, the tax effects of changes in tax laws must be recognized when the law is enacted, or December 22, 2017 for the TCJA. ASC 740 also requires deferred tax assets and liabilities to be measured at the enacted tax rate expected to apply when temporary differences are to be realized or settled. Based on this, our liability in lieu of deferred income taxes was re-measured at the date of enactment using the new tax rate.  We have completed the measurement and accounting for the effects of the TCJA which have been reflected in our December 31, 2017 financial statements. The re-measurement of our liability in lieu of deferred income taxes related to our non-regulated operations resulted in a $21 million charge to the nonoperating provision in lieu of tax expense for the year ending December 31, 2017. The re - measurement of our liability in lieu of deferred income taxes related to our regulated operations resulted in a $1.6 billion decrease in our liability in lieu of deferred income taxes at December 22, 2017 and a corresponding increase in our regulatory liabilities.  The increase in regulatory liabilities reflects our obligation, as required by PUCT order in Docket No. 46957, to refund to utility cust omers any excess deferred tax related balances created by the reduction in the corporate federal income tax rate . The TCJA includes provisions that stipulate how quickly certai n of these excess deferred tax related balances may be refunded to our customers through reductions in our future rates. These adjustments had no impact on our 2017 cash flows. Also, beginning January 1, 2018, Oncor will record as a regulatory liability the amount that Oncor collects through its approved tariffs for federal income taxes that is above the new corporate federal income tax rate in compliance with PUCT Docket No. 46957. We estimate that incorporating the new corporate federal income tax rate in our approved rate settlement agreement would have reduced our annual revenues and our tax expense by approximately $125 million.  Components of Liability in Lieu of Deferred Income Taxes  The components of our liability in lieu of deferred income tax es are provided in the table below.    At Ended December 31,  2017 2016    Deferred Tax Related Assets:  Employee benefit liabilities $ 253 $ 413  Regulatory liabilities 15 26  Other 7 79  Total 275 518  Deferred Tax Related Liabilities:  Property, plant and equipment 1,551 2,892  Regulatory assets 240 412  Other 1 2  Total 1,792 3,306  Liability in lieu of deferred income taxes - net $ 1,517 $ 2,788  Provision (Benefit) in Lieu of Income Taxes  The components of our reported provision (benefit) in lieu of income taxes are as follows:   Year Ended December 31,  2017 2016 2015   Reported in operating expenses:  Current:  U.S. federal $ (55) $ 60 $ 189  State 20 20 32  Deferred:  U.S. federal 292 181 55  State - - (13)  Amortization of investment tax credits (2) (2) (3)  Total reported in operating expenses 255 259 260  Reported in other income and deductions:  Current:  U.S. federal (5) (5) (7)  State - - -  Deferred federal 17 - (1)  Total reported in other income and deductions 12 (5) (8)  Total provision in lieu of income taxes $ 267 $ 254 $ 252  Reconciliation of provision in lieu of income taxes computed at the U.S. federal statutory rate to provision in lieu of income taxes:   Year Ended December 31,  2017 2016 2015   Income before provision in lieu of income taxes $ 686 $ 685 $ 684  Provision in lieu of income taxes at the U.S. federal statutory rate of 35% $ 240 $ 240 $ 239  Amortization of investment tax credits – net of deferred tax effect (2) (2) (3)  Amortization (under regulatory accounting) of statutory tax rate changes (1) (1) (1)  Impact of federal statutory rate change from 35% to 21% 21 - -  Texas margin tax, net of federal tax benefit 13 13 13  Nontaxable gains on benefit plan investments (4) - -  Other, including audit settlements - 4 4  Reported provision in lieu of income taxes $ 267 $ 254 $ 252  Effective rate 38.9% 37.1% 36.8%  The net amounts of $ 1 . 517 billion and $2. 788 billion reported in the balance sheets at December 31, 201 7 and 201 6 , respectively, as liability in lieu of deferred income taxes include amounts previously recorded as net deferred tax liabilities. Upon the sale of equity interests to Texas Transmission and Investment LLC in 2008, we became a partnership for U . S . federal income tax purposes, and the temporary differences that gave rise to the deferred taxes will, over time, become taxable to the equity holders. Under a tax sharing agreement among us and our equity holders (see Note 1), we make payments to the equity holders related to income taxes when amounts would have become due to the IRS if Oncor was taxed as a corporation . Accordingly, as the temporary differences become taxable, we will pay the equity holders. In the event such amounts are not paid under the tax sharing agreement, it is probable that this regulatory liability will continue to be included in Oncor’s rate setting processes .  Accounting For Uncertainty in Provision in Lieu of Income Taxes  Prior to November 2008, we were a member of the EFH Corp. consolidated tax group. The examination and applicable appeals process of EFH Corp. and its subsidiaries’ federal income tax returns for the years ending prior to January 1, 2016 are complete. The statute of limitations is open for our partnership tax returns for the years beginning after December 31, 2009, however, the IRS has declined to review the tax returns for the years ending prior to January 1, 2016. Texas margin tax returns are under examination or still open for examination for tax years beginning after 2014. Subsequent to November 2008, we are not a member of the EFH Corp. consolidated federal tax group and assess our liability for uncertain tax positions in our partnership returns.  The following table summarizes the changes to the uncertain tax positions reported in other noncurrent liabilities in our consolidated balance sheet during the years ended December 31, 2017, 2016 and 2015:   2017 2016 2015    Balance at January 1, excluding interest and penalties $ 3 $ 3 $ 2  Additions based on tax positions related to prior years - - -  Reductions based on tax positions related to prior years (3) - -  Settlements with taxing authorities - - 1  Balance at December 31, excluding interest and penalties $ - $ 3 $ 3  Of the balances at both December 31, 2016 and 2015, $3 million represents tax positions for which the uncertainty relates to the timing of recognition for tax purposes. The disallowance of such positions would not affect the effective tax rate, but would accelerate the payment of cash under the tax sharing agreement to an earlier period. In the first quarter 2017, EFH Corp. settled all open tax claims with the IRS. As a result, we reduced the liability for uncertain tax positions by $3 million. This reduction is reported as a decrease in income taxes in 2017.  Noncurrent liabilities included no accrued interest related to uncertain tax positions at December 31, 2017 and 2016. There were no amounts recorded related to interest and penalties in the year s ended December 31, 2017, 2016 and 2015. The federal income tax benefit on the interest accrued on uncertain tax positions is recorded as liability in lieu of deferred income taxes.

Regulatory Assets and Liabiliti

Regulatory Assets and Liabilities	12 Months Ended
	Dec. 31, 2017
Regulatory Assets and Liabilities [Abstract]
REGULATORY ASSETS AND LIABILITIES	5. REGULATORY ASSETS AND LIABILITIES  Recognition of regulatory assets and liabilities and the periods which they are to be recovered or refunded through rate regulation are determined by t he PUCT. Components of our regulatory assets and liabilities and their remaining periods as of December 31, 2017 are provided in the table below. Amounts not earning a return through rate regulation are noted.   Remaining Rate Recovery/Amortization Period at Carrying Amount At  December 31, 2017 December 31, 2017 December 31, 2016   Regulatory assets:  Employee retirement costs being amortized 10 years $ 331 $ 23  Unrecovered employee retirement costs incurred since the last rate review period (b) To be determined 30 327  Employee retirement liability (a)(b)(c) To be determined 854 849  Self-insurance reserve (primarily storm recovery costs) being amortized 10 years 394 64  Unrecovered self-insurance reserve incurred since the last rate review period (b) To be determined 49 367  Securities reacquisition costs (post-industry restructure) Lives of related debt 12 13  Deferred conventional meter and metering facilities depreciation 3 years 57 78  Under-recovered AMS costs 10 years 206 209  Unprotected excess deferred taxes Various 197 -  Energy efficiency performance bonus (a) 1 year or less 12 10  Other regulatory assets Various 38 34  Total regulatory assets 2,180 1,974   Regulatory liabilities:  Estimated net removal costs Lives of related assets 954 819  Protected excess deferred taxes Various 1,595 3  Unprotected excess deferred taxes Various 194 -  Over-recovered wholesale transmission service expense (a) 1 year or less 47 10  Other regulatory liabilities Various 17 24  Total regulatory liabilities 2,807 856  Net regulatory assets (liabilities) $ (627) $ 1,118 ____________ (a) Not earning a return in the regulatory rate-setting process. (b) Recovery is specifically authorized by statute or by the PUCT, subject to reasonableness review. (c) Represents unfunded liabilities recorded in accordance with pension and OPEB accounting standards.   The excess deferred tax related balances at December 31, 2017 are primarily the result of the TCJA corporate federal income tax rate reduction from 35% to 21%. These regulatory assets and liabilities reflect our obligation, as required by PUCT order in Docket No. 46957, to refund to utility customers any excess deferred tax related balances created by the reduction in the corporate federal income tax rate . The TCJA includes provisions that stipulate how quickly certain of these excess deferred tax related balances, labeled “Protected excess deferred taxes”, may be refunded to our customers through reductions in our future rates. These adjustments had no impact on our 2017 cash flows. In October 2017, the PUCT issued a final order in our rate review filed in March 2017. The rate review included a determination of the recoverability of regulatory assets at December 31, 2016, including the recoverability period of those assets deemed allowable by the PUCT. The rate review resulted in significant amounts being reclassified to “Employee retirement costs being amortized” and “Self-insurance reserve being amortized” as reflected in the table above.  In September 2008, the PUCT approved a settlement for us to recover our estimated future investment for advanced metering deployment. We began billing the AMS surcharge in the January 2009 billing month cycle. The surcharge was expected to total $1.023 billion over the 11 -year recovery period and includes a cost recovery factor of $2.19 per month per residential retail customer and $2.39 to $5.15 per month for non-residential retail customers. We accounted for the difference between the surcharge billings for advanced metering facilities and the allowable revenues under the surcharge provisions, which were based on expenditures and an allowed return, as a regulatory asset or li ability. Such differences arose principally as a result of timing of expenditures or cost increases. In accordance with the PUCT Docket No 46957 rate review final order, effective November 27, 2017, the AMS surcharge ceased and ongoing AMS costs are being recovered through base rates which include the recovery of the AMS regulatory asset over a 10 -year period.

Short-Term Borrowings

Short-Term Borrowings	12 Months Ended
	Dec. 31, 2017
Short-Term Borrowings [Abstract]
SHORT-TERM BORROWINGS	6. SHORT-TERM BORROWINGS  On November 17, 2017, we entered into a new $2.0 billion unsecured revolving credit facility (2017 Credit Facility) to be used for working capital and general corporate purposes, issuances of letters of credit and support for any commercial paper issuances. We may request increases in our borrowing capacity in increments of not less than $100 million, not to exceed $400 million in the aggregate, provided certain conditions are met, including lender approvals. The 2017 Credit Facility has a five-year term expiring in November 2022 and gives us the option of requesting up to two one -year extensions, with such extensions subject to certain conditions and lender approvals. The 2017 Credit Facility replaced our previous $2.0 billion secured revolving credit facility (previous credit facility) , which was terminated in connection with our entrance into the 2017 Credit Facility . Borrowings under our previous credit facility were secured with the lien of the Deed of Trust discussed in Note 7 below. Borrowings are classified as short-term on the balance sheet.  At December 31, 2017, we had outstanding borrowings under the 2017 Credit Facility totaling $950 million with an interest rate of 2.62% per annum and outstanding letters of credit totaling $9 million. At December 31, 2016, we had outstanding borrowings under our previous credit facility totaling $789 million with an interest rate of 1.72% and outstanding letters of credit totaling $7 million.  Borrowings under the 2017 Credit Facility bear interest at per annum rates equal to, at our option, (i) adjusted LIBOR plus a spread ranging from 0 .875% to 1.50% depending on credit ratings assigned to our senior secured non-credit enhanced long-term debt or (ii) an alternate base rate (the highest of (1) the prime rate of JPMorgan Chase, (2) the federal funds effective rate plus 0.50% , and (3) adjusted LIBOR plus 1.00% ) plus a spread ranging from 0.00% to 0.50% depending on credit ratings assigned to our senior secured non-credit enhanced long-term debt. At December 31, 2017, all outstanding borrowings bore interest at LIBOR plus 1.125% . Amounts borrowed under the 2017 Credit Facility , once repaid, can be borrowed again from time to time.  An unused commitment fee is payable quarterly in arrears and upon termination or commitment reduction at a rate equal to 0.075% to 0.225% (such spread depending on certain credit ratings assigned to our senior secured debt) of the daily unused commitments under the 2017 Credit Facility . Letter of credit fees on the stated amount of letters of credit issued under the 2017 Credit Facility are payable to the lenders quarterly in arrears and upon termination at a rate per annum equal to the sp read over adjusted LIBOR. Customary fronting and administrative fees are also payable to letter of credit fronting banks. At December 31, 2017, letters of credit bore interest at 1.325% , and a commitment f ee (at a rate of 0.125% per annum) was payable on the unfunded commitments under the 2017 Credit Facility , each based on our current credit ratings.  Under the terms of the 2017 Credit Facility , the commitments of the lenders to make loans to us are several and not joint. Accordingly, if any lender fails to make loans to us, our available liquidity could be reduced by an amount up to the aggregate amount of such lender’s commitments under the facility.  Subject to the limitations described below, borrowing capacity available under the 2017 Credit Facility at December 31, 2017 was $1.041 billion, and borrowing capacity under our previous credit facility at December 31, 2016 was $1.204 billion and could be fully drawn.  The 2017 Credit Facility contains customary covenants for facilities of this type, restricting, subject to certain exceptions, us and our subsidiaries from, among other things : incurring certain additional liens (not including liens relating to obligations secured pursuant to our Deed of Trust, which are permitted); entering into mergers and consolidations; sales of substantial assets and acquisitions and investments in subsidiaries . In addition, the 2017 Credit Facility requires that we maintain a consolidated senior debt-to-capitalization ratio of no greater than 0.65 to 1.00 and observe certain customary reporting requirements and other affirmative covenants. For purposes of the ratio, debt is calculated as indebtedness defined in the 2017 Credit Facility (principally, the sum of long-term debt, any capital leases, short-term debt and debt due currently in accordance with GAAP). Capitalization is calculated as membership interests determined in accordance with GAAP plus indebtedness described above. At December 31, 201 7 , we were in compliance with this and all other covenants .

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2017
Long-Term Debt [Abstract]
LONG-TERM DEBT	7. LONG-TERM DEBT  Our senior notes are secured by a first priority lien on certain transmission and distribution assets equally and ratably with all of Oncor’s other secured indebtedness. See “Deed of Trust” below for additional information. At December 31, 201 7 and 201 6 , our long-term debt consisted of the following:   December 31,  2017 2016   Secured:  5.000% Fixed Senior Notes due September 30, 2017 $ - $ 324  6.800% Fixed Senior Notes due September 1, 2018 550 550  2.150% Fixed Senior Notes due June 1, 2019 250 250  5.750% Fixed Senior Notes due September 30, 2020 126 126  4.100% Fixed Senior Notes due June 1, 2022 400 400  7.000% Fixed Debentures due September 1, 2022 800 800  2.950% Fixed Senior Notes due April 1, 2025 350 350  7.000% Fixed Senior Notes due May 1, 2032 500 500  7.250% Fixed Senior Notes due January 15, 2033 350 350  7.500% Fixed Senior Notes due September 1, 2038 300 300  5.250% Fixed Senior Notes due September 30, 2040 475 475  4.550% Fixed Senior Notes due December 1, 2041 400 400  5.300% Fixed Senior Notes due June 1, 2042 500 500  3.750% Fixed Senior Notes due April 1, 2045 550 550  3.800% Fixed Senior Notes due September 30, 2047 325 -  Secured long-term debt 5,876 5,875  Unsecured:  Term loan credit agreement due no later than March 26, 2019 275 -  Total long-term debt 6,151 5,875  Unamortized discount and debt issuance costs (34) (36)  Less amount due currently (550) (324)  Long-term debt, less amounts due currently $ 5,567 $ 5,515  Debt-Related Activity in 2017  Debt Repayments  Repayments of long-term debt in 2017 consisted of $324 million aggregate principal amount of 5.00% senior secured notes due September 30, 2017 (2017 Notes) that we redeemed on September 29, 2017.  Issuance of Senior Secured Notes  In September 2017, we issued $325 million aggregate principal amount of 3.80% senior secured notes due September 30, 2047 (2047 Notes). We used the proceeds (net of the initial purchasers’ discount, fees and expenses) of $321 million from the sale of the 2047 Notes for general corporate purposes, including repayment of borrowings under the revolving credit facility and payment of a portion of the redemption price for the 2017 Notes. The 2047 Notes are secured by a first priority lien, and are secured equally and ratably with all of our other secured indebtedness.  Interest on the 2047 Notes is payable in cash semiannually on March 30 and September 30 of each year, beginning on March 30, 2018. Prior to March 30, 2047, we may at our option at any time redeem all or part of the 2047 Notes at a price equal to 100% of their principal amount, plus accrued and unpaid interest and a make-whole premium. On and after March 30, 2047, Oncor may redeem the 2047 Notes at any time, in whole or in part, at a redemption price equal to 100% of the principal amount of such 2047 Notes, plus accrued and unpaid interest. The 2047 Notes also contain customary events of default, including failure to pay principal or interest on the 2047 Notes when due.  The 2047 Notes were issued in a private placement and were not registered under the Securities Act. We have agreed, subject to certain exceptions, to register with the SEC notes having substantially identical terms as the 2047 Notes (except for provisions relating to the transfer restriction and payment of additional interest) as part of an offer to exchange freely tradable exchange notes for the 2047 Notes. We have agreed to use commercially reasonable efforts to cause the exchange offer to be completed within 315 days after the issue date of the 2047 Notes. If a registration statement for the exchange offer is not declared effective by the SEC within 270 days after the issue date of the 2047 Notes or the exchange offer is not completed within 315 days after the issue date of the 2047 Notes (an exchange default), then the annual interest rate on the 2047 Notes will increase 50 basis points per annum until the earlier of the expiration of the exchange default or the second anniversary of the issue date of the 2047 Notes.  Term Loan Credit Agreement  On September 26, 2017, we entered into an unsecured term loan credit agreement in an aggregate principal amount of $275 million. We used the proceeds (net of the fees and expenses) for general corporate purposes, including repayment of borrowings under the revolving credit facility and to pay a portion of the redemption price for the 2017 Notes. The term loan credit agreement has an 18 -month term maturing on March 26, 2019, and contains optional prepayment provisions as well as mandatory prepayment provisions that require prepayment in the event of certain specified debt issuances or certain specified asset dispositions.  At December 31, 2017, we had outstanding borrowings of $275 million under the term loan credit agreement bearing interest at a rate per annum of 2. 452 % .  Loans under the term loan credit agreement bear interest at per annum rates equal to, at our option, (i) LIBOR plus 0.90% , or (ii) an alternate base rate (the highest of (1) the prime rate of Wells Fargo Bank, National Association, (2) the federal funds effective rate plus 0.50% , and (3) daily one-month LIBOR plus 1.00% ).  The term loan credit agreement contains customary covenants for facilities of this type, restricting, subject to certain exceptions, us and our subsidiaries from, among other things, incurring additional liens, entering into mergers and consolidations, and sales of substantial assets. In addition, the term loan credit agreement requires that we maintain a consolidated senior debt to capitalization ratio of no greater than 0.65 to 1.00 and observe certain customary reporting requirements and other affirmative covenants. At December 31, 2017, we were in compliance with the covenants under our term loan credit agreement.  The term loan credit agreement also contains customary events of default for facilities of this type the occurrence of which would allow the lenders to accelerate all outstanding loans and terminate their commitments, including certain changes in control of Oncor that are not permitted transactions under the term loan credit agreement, cross-default provisions in the event Oncor or any of its subsidiaries defaults on indebtedness in a principal amount in excess of $100 million or receives judgments for the payment of money in excess of $50 million that are not discharged within 60 days.  Debt-Related Activity in 2016  Debt Repayments  Rep ayments of long-term debt in 2016 totaled $41 million, representing the final transition bond principal payment at the scheduled maturity date.  Issuance of Senior Secured Notes  In August 2016, we completed the sale of $175 million aggregate principal amount of 3.75% senior secured notes maturing in April 2045 (Additional 2045 Notes). The Additional 2045 Notes were an additional issuance of our 3.75% senior secured notes maturing in April 2045, $375 million aggregate principal amount of which were previously issued in March 2015 (2045 Notes). The Additional 2045 Notes were issued as part of the same series as the 2045 Notes. We used the net proceeds of approximately $185 million from the sale of the Additional 2045 Notes to repay borrowings under our revolving credit facility and for general corporate purposes. The Additional 2045 Notes and 2045 Notes are secured by the first priority lien and are secured equally and ratably with all of our other secured indebtedness as discussed below.  Interest on the Additional 2045 Notes is payable in cash semiannually in arrears on April 1 and October 1 of each year, beginning on October 1, 2016. We may at our option redeem the Additional 2045 Notes, in whole or in part, at any time, at a price equal to 100% of their principal amount, plus accrued and unpaid interest and, until October 1, 2044 , a make-whole premium. The Additional 2045 Notes also contain customary events of default, including failure to pay principal or interest on the Additional 2045 Notes when due.  The Additional 2045 Notes were issued in a private placement. In January 2017, we completed an offering with the holders of the Additional 2045 Notes to exchange their respective Additional 2045 Notes for notes that have terms identical in all material respects to the Additional 2045 Notes (Exchange Notes), except that the Exchange Notes do not contain terms with respect to transfer restrictions, registration rights and payment of additional interest for failure to observe certain obligations in a certain registration rights agreement. The Exchange Notes were registered on a Form S-4, which was declared effective in December 2016.  Deed of Trust  Our secured indebtedness is secured equally and ratably by a first priority lien on property we acquired or constructed for the transmission and distribution of electricity. The property is mortgaged under the Deed of Trust. The Deed of Trust permits us to secure indebtedness ( excluding borrowings under the 2017 Credit Facility and the term loan credit agreement ) with the lien of the Deed of Trust up to the aggregate of (i) the amount of available bond credits, and (ii) 85% of the lower of the fair value or cost of certain property additions that could be certified to the Deed of Trust collateral agent. At December 31, 201 7 , the amount of available bond credits was approximately $3.038 billion and the amount of future debt we could secure with property additions, subject to those property additions being certified to the Deed of Trust collateral agent, was $2.458 billion.  Maturities  Long-term debt maturities at December 31, 201 7 , are as follows:   Year Amount  2018 $ 550  2019 525  2020 126  2021 -  2022 1,200  Thereafter 3,750  Unamortized discount and debt issuance costs (34)  Total $ 6,117  Fair Value of Long-Term Debt  At December 31, 201 7 and 201 6 , the estimated fair value of our long-term debt (including current maturities) totaled $7.153 billion and $6.751 billion, respectively, and the carrying amount totaled $ 6 . 117 billion and $5.839 billion, r espectively. The fair value is estimated using observable market data , representing Level 2 valuations under accounting standards related to the determination of fair value.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies [Abstract]
COMMITMENTS AND CONTINGENCIES	8 . COMMITMENTS AND CONTINGENCIES  EFH Bankruptcy Proceedings  On the EFH Petition Date, the Debtors commenced the EFH Bankruptcy Proceedings. T he Oncor Ring-Fenced Entities are not parties to the EFH Bankruptcy Proceedings. See Notes 2 and 12 for a discussion of the potential impacts on us as a result of the EFH Bankruptcy Proceedings and our related-party transactions involving members of the Texas Holdings Group, respectively.  Leases  At December 31, 201 7 , our future minimum lease payments under our operating leases (with initial or remaining noncancelable lease terms in excess of one year) were as follows:    Year Amount  2018 $ 32  2019 21  2020 14  2021 11  2022 10  Thereafter 1  Total future minimum lease payments $ 89  Rent charged to operation and maintenance expense totaled $ 27 million, $9 million and $ 8 million for the years ended December 31, 201 7 , 201 6 and 201 5 , respectively.  Efficiency Spending  We are required to annually invest in programs designed to improve customer electricity demand efficiencies to satisfy ongoing regulatory requirements. The 201 8 requirement is $50 million which is recoverable in rates .  Legal/Regulatory Proceedings  We are involved in various legal and administrative proceedings in the normal course of business, the ultimate resolution of which, in the opinion of management, should not have a material effect upon our financial position, results of operations or cash flows. See Note 3 for additional information regarding contingencies.  Labor Contracts  At December 31, 2017, approximately 19% of our full time employees were represented by a labor union and covered by a collective bargaining agreement with an expiration date of October 25, 2018 .  Environmental Contingencies  We must comply with environmental laws and regulations applicable to the handling and disposal of hazardous waste. We are in compliance with all current laws and regulations; however, the impact, if any, of changes to existing regulations or the implementation of new regulations is not determinable. The costs to comply with environmental regulations can be significantly affected by the following external events or conditions:  · changes to existing state or federal regulation by governmental authorities having jurisdiction over control of toxic substances and hazardous and solid wastes, and other environmental matters, and · the identification of additional sites requiring clean-up or the filing of other complaints in which we may be asserted to be a potential responsible party.

Membership Interests

Membership Interests	12 Months Ended
	Dec. 31, 2017
Membership Interests [Abstract]
MEMBERSHIP INTERESTS	9 . MEMBERSHIP INTERESTS  Cash Distributions  Distributions are limited by our required regulatory capital structure to be at or below the assumed debt-to-equity ratio established periodically by the PUCT for ratemaking purposes. The PUCT has the authority to determine what types of debt and equity are included in a utility’s debt-to-equity ratio. For purposes of this ratio, debt is calculated as long-term debt including capital leases plus unamortized gains on reacquired debt less unamortized issuance expenses, premiums and losses on reacquired debt. Equity is calculated as membership interests determined in accordance with GAAP, excluding the effects of acquisition accounting (which included recording the initial goodwill and fair value adjustments and subsequent related impairments and amortization).  Our PUCT authorized capital structure is 57.5% debt to 42.5% equity effective November 27, 2017 based on the PUCT order issued in PUCT Docket No. 46957 (see Note 3 for additional information). Our previous PUCT authorized capital structure was 60% debt to 40% equity. At December 31, 2017, our regulatory capitalization ratio was 59.4% debt to 40.6% equity effectively restricting our ability to make cash distributions to our members. The PUCT order requires Oncor to record a regulatory liability until the new authorized regulatory capital structure is met to reflect our actual capitalization prior to achieving the authorized capital structure. Once the authorized capital structure is attained, the regulatory liability will be returned to customers through the capital structure refund mechanism approved in the PUCT docket. Oncor implemented the regulatory liability as of November 27, 2017.  On O ctober 25, 2017, our board of directors declared a contingent cash distribution of $32 million to be paid to our members as of October 25, 2017 within one business day after an additional equity contribution is made to Oncor from members totaling approximately $250 million. In the event the additional equity contribution is not made on or before the date of the closing of the Sempra Merger Agreement, no distribution shall be payable. As of February 22 , 201 8 th e distribution had not been made. For more information on the Sempra Merger Agreement, see Note 2.  During 2017, our board of directors declared, and we paid, the following cash distributions to our members:   Declaration Date Payment Date Amount  July 26, 2017 August 1, 2017 $ 65  April 26, 2017 April 27, 2017 $ 86  March 22, 2017 March 24, 2017 $ 86  During 2016, our board of directors declared, and we paid, the following cash distributions to our members:  Declaration Date Payment Date Amount  October 26, 2016 October 27, 2016 $ 41  July 27, 2016 August 11, 2016 $ 68  April 27, 2016 May 11, 2016 $ 65  February 24, 2016 February 25, 2016 $ 56  Accumulated Other Comprehensive Income (Loss)  The following table presents the changes to accumulated other comprehensive income (loss) for the years ended December 31, 2017, 2016 and 2015.   Cash Flow Hedges – Interest Rate Swap Defined Benefit Pension and OPEB Plans Accumulated Other Comprehensive Income (Loss)   Balance at December 31, 2014 $ (24) $ (83) $ (107)  Defined benefit pension plans (net of tax) - (8) (8)  Amounts reclassified from accumulated other comprehensive income (loss) and reported in interest expense and related charges 2 - 2  Balance at December 31, 2015 $ (22) $ (91) $ (113)  Defined benefit pension plans (net of tax) - - -  Amounts reclassified from accumulated other comprehensive income (loss) and reported in interest expense and related charges 2 - 2  Balance at December 31, 2016 $ (20) $ (91) $ (111)  Defined benefit pension plans (net of tax) - 8 8  Amounts reclassified from accumulated other comprehensive income (loss) and reported in interest expense and related charges 2 - 2  Balance at December 31, 2017 $ (18) $ (83) $ (101) 

Pension and OPEB Plans

Pension and OPEB Plans	12 Months Ended
	Dec. 31, 2017
Pension And OPEB Plans [Abstract]
PENSION AND OPEB PLANS	10 . PENSION AND OPEB PLANS  Regulatory Recovery of Pension and OPEB Costs  PURA provides for our recovery of pension and OPEB costs applicable to services of our active and retired employees, as well as services of other EFH Corp. /Vistra active and retired employees prior to the deregulation and disaggregation of EFH Corp.’s electric utility businesses effective January 1, 2002 (recoverable service). Accordingly, in 2005, we entered into an agreement with a predecessor of EFH Corp. whereby we assumed responsibility for applicable pension and OPEB costs related to those personnel’s recoverable service. We subsequently entered into agreements with EFH Corp. and a Vistra affiliate regarding provision of these benefits. Pursuant to our agreement with the Vistra affiliate, we now sponsor an OPEB plan that provides certain retirement healthcare and life insurance benefits to eligible former Oncor, EFH Corp. and Vistra employees for whom both Oncor and Vistra bear a portion of the benefit responsibility. See “Oncor OPEB Plan” below for more information.  We are authorized to establish a regulatory asset or liability for the difference between the amounts of pension and OPEB costs approved in current billing rates and the actual amounts that would otherwise have been recorded as charges or credits to earnings related to recoverable service. Amounts deferred are ultimately subject to regulatory approval. At December 31, 201 7 and 201 6 , we had recorded regulatory assets totali ng $1.215 bill ion and $ 1.199 b illion, respectively, related to pension and OPEB costs, including amounts related to deferred expenses as well as amounts related to unfunded liabilities that otherwise would be recorded as other comprehensive income.  We have also assumed primary responsibility for pension benefits of a closed group of retired and terminated vested plan participants not related to our regulated utility business (non-recoverable service) in a 2012 transaction. Any retirement costs associated with non-recoverable service is not recoverable through rates.  Pension Plan s  We sponsor the Oncor Retirement Plan and also have liabilities under the Vistra Retirement Plan (formerly EFH Retirement Plan ) , both of which are qualified pension plans under Section 401(a) of the Code, and are subject to the provisions of ERISA. Employees do not contribute to either plan. These pension plans provide benefits to participants under one of two formulas: (i) a Cash Balance Formula under which participants earn monthly contribution credits based on their compensation and a combination of their age and years of service, plus monthly interest credits or (ii) a Traditional Retirement Plan Formula based on years of service and the average earnings of the three years of highest earnings. The interest component of the Cash Balance Formula is variable and is determined using the yield on 30-year Treasury bonds. Under the Cash Balance Formula, future increases in earnings will not apply to prior service costs.  All eligible employees hired after January 1, 2001 participate under the Cash Balance Formula. Certain employees, who, prior to January 1, 2002, participated under the Traditional Retirement Plan Formula, continue their participation under that formula. It is the sponsors’ policy to fund the plans on a current basis to the extent required under existing federal tax and ERISA regulations.  We also have the S upplemental Retirement P lan for certain employees whose retirement benefits cannot be fully earned under the qualified retirement plan . Supplemental Retirement Plan amounts are included in the reported pension amounts below.  Oncor OPEB Plan  Oncor’s OPEB Plan covers our eligible current and future retirees. Pursuant to our agreement with a Vistra affiliate, we sponsor an OPEB plan that covers certain eligible retirees of Oncor, EFH Corp./Vistra and their affiliates whose employment service was assigned to both Oncor (or a predecessor regulated electric business) and a non-regulated business of EFH Corp. Vistra is solely responsible for its portion of the liability for retiree benefits related to those retirees . As we are not responsible for Vistra’s portion of the Oncor OPEB Plan’s unfunded liability totaling $111 million as of December 31, 201 7 , that amount is not reported on our balance sheet.  OPEB plan contributions are generally required to be made at least annually based on OPEB expense included in rates. Contributions are placed in an irrevocable external trust fund dedicated to the payment of OPEB expenses.  For employees retiring on or after January 1, 2002, the retiree contributions required for such coverage vary based on a formula depending on the retiree’s age and years of service.  Pension and OPEB Costs Recognized as Expense  P ension and OPEB amounts p rovided herein include amounts related only to our portion of the various plans based on actuarial computations and reflect our employee and retiree demographics as described above. Our net costs related to pension and OPEB plans for the years ended December 31, 2017, 2016 and 2015 were comprised of the following :      Year Ended December 31,  2017 2016 2015   Pension costs $ 85 $ 76 $ 104  OPEB costs 58 62 53  Total benefit costs 143 138 157  Less amounts recognized principally as property or a regulatory asset (98) (100) (113)  Net amounts recognized as expense $ 45 $ 38 $ 44  T he calculated value method is used to determine the market-related value of the assets held in the trust for purposes of calculating our pension costs. R ealized and unrealized gains or losses in the market-related value of assets are included over a rolling four -year period. Each year, 25% of such gains and losses for the current year and for each of the preceding three years is included in the market-related value. Each year, the market-related value of assets is increased for contributions to the plan and investment income and is decreased for benefit payments and expenses for that year.  T he fair value method is used to determine the market-related value of the assets held in the trust for purposes of calculating OPEB cost.  Detailed Information Regarding Pension and OPEB Benefits  The following pension and OPEB information is based on December 31, 201 7 , 201 6 and 201 5 measurement dates:   Pension Plans OPEB Plan  Year Ended December 31, Year Ended December 31,  2017 2016 2015 2017 2016 2015   Assumptions Used to Determine Net Periodic Pension and OPEB Costs:  Discount rate 4.05% 4.30% 3.96% 4.35% 4.60% 4.23%  Expected return on plan assets 5.17% 5.54% 5.26% 6.10% 6.30% 6.65%  Rate of compensation increase 3.33% 3.29% 3.29% - - -   Components of Net Pension and OPEB Costs:  Service cost $ 24 $ 23 $ 25 $ 7 $ 7 $ 7  Interest cost 131 134 131 47 49 43  Expected return on assets (115) (122) (115) (8) (9) (10)  Amortization of prior service cost (credit) - - - (20) (20) (20)  Amortization of net loss 45 41 63 32 35 33  Net periodic pension and OPEB costs $ 85 $ 76 $ 104 $ 58 $ 62 $ 53   Other Changes in Plan Assets and Benefit Obligations Recognized as Regulatory Assets or in Other Comprehensive Income:  Net loss (gain) $ (11) $ 41 $ 37 $ 139 $ 10 $ 39  Amortization of net loss (45) (41) (63) (32) (35) (33)  Plan amendments - - - (78) - -  Amortization of prior service (cost) credit - - - 20 20 20  Total recognized as regulatory assets or other comprehensive income (56) - (26) 49 (5) 26  Total recognized in net periodic pension and OPEB costs and as regulatory assets or other comprehensive income $ 29 $ 76 $ 78 $ 107 $ 57 $ 79    Pension Plans OPEB Plan  Year Ended December 31, Year Ended December 31,  2017 2016 2015 2017 2016 2015   Assumptions Used to Determine Benefit Obligations at Period End:  Discount rate 3.54% 4.05% 4.30% 3.73% 4.35% 4.60%  Rate of compensation increase 4.46% 3.33% 3.29% - - -     Pension Plans OPEB Plan  Year Ended December 31, Year Ended December 31,  2017 2016 2017 2016   Change in Projected Benefit Obligation:  Projected benefit obligation at beginning of year $ 3,307 $ 3,201 $ 1,116 $ 1,088  Service cost 24 23 7 7  Interest cost 131 134 47 49  Participant contributions - - 19 17  Assumption of liabilities - - - 7  Plan amendments - - (78) -  Actuarial (gain) loss 201 106 154 10  Benefits paid (163) (157) (67) (62)  Projected benefit obligation at end of year $ 3,500 $ 3,307 $ 1,198 $ 1,116  Accumulated benefit obligation at end of year $ 3,387 $ 3,213 $ - $ -   Change in Plan Assets:  Fair value of assets at beginning of year $ 2,287 $ 2,252 $ 143 $ 141  Actual return (loss) on assets 327 188 23 9  Employer contributions 149 4 31 31  Assets related to assumed liabilities - - - 7  Participant contributions - - 19 17  Benefits paid (163) (157) (67) (62)  Fair value of assets at end of year $ 2,600 $ 2,287 $ 149 $ 143   Funded Status:  Projected benefit obligation at end of year $ (3,500) $ (3,307) $ (1,198) $ (1,116)  Fair value of assets at end of year 2,600 2,287 149 143  Funded status at end of year $ (900) $ (1,020) $ (1,049) $ (973)             Pension Plans OPEB Plan  Year Ended December 31, Year Ended December 31,  2017 2016 2017 2016   Amounts Recognized in the Balance Sheet Consist of:  Liabilities:  Other current liabilities $ (4) $ (4) $ (12) $ -  Other noncurrent liabilities (896) (1,016) (1,037) (973)  Net liability recognized $ (900) $ (1,020) $ (1,049) $ (973)  Regulatory assets:  Net loss $ 538 $ 583 $ 402 $ 296  Prior service cost (credit) - - (86) (30)  Net regulatory asset recognized $ 538 $ 583 $ 316 $ 266  Accumulated other comprehensive net loss $ 124 $ 136 $ 3 $ 4  The following tables provide information regarding the assumed health care cost trend rates.   Year Ended December 31,  2017 2016   Assumed Health Care Cost Trend Rates – Not Medicare Eligible:  Health care cost trend rate assumed for next year (a) 8.00% 5.80%  Rate to which the cost trend is expected to decline (the ultimate trend rate) 4.50% 5.00%  Year that the rate reaches the ultimate trend rate 2026 2024   Assumed Health Care Cost Trend Rates – Medicare Eligible:  Health care cost trend rate assumed for next year (b) 9.40% 5.70%  Rate to which the cost trend is expected to decline (the ultimate trend rate) 4.50% 5.00%  Year that the rate reaches the ultimate trend rate 2026 2024   (a) 2017 trend rates include weighting for prescription drugs. Comparable rate for 2016 is 6.80%.  (b) 2017 trend rates include weighting for prescription drugs. Comparable rate for 2016 is 8.40%.  1-Percentage Point Increase 1-Percentage Point Decrease   Sensitivity Analysis of Assumed Health Care Cost Trend Rates:  Effect on accumulated postretirement obligation $ 158 $ (131)  Effect on postretirement benefits cost 8 (6)  The following table provides information regarding pension plans with projected benefit obligations (PBO) and accumulated benefit obligations (ABO) in excess of the fair value of plan assets.    At December 31,  2017 2016   Pension Plan with PBO and ABO in Excess of Plan Assets:  Projected benefit obligations $ 3,316 $ 3,137  Accumulated benefit obligations 3,207 3,051  Plan assets 2,409 2,112  Pension and OPEB Plan s Investment Strategy and Asset Allocations  Our investment objective for the retirement plans is to invest in a suitable mix of assets to meet the future benefit obligations at an acceptable level of risk, while minimizing the volatility of contributions. Equity securities are held to achieve returns in excess of passive indexes by participating in a wide range of investment opportunities. International equity , real estate securities and credit strategies (high yield bonds, emerging market debt and bank loans) are used to further diversify the equity portfolio . International equity securities may include investments in both developed and emerging international markets. Fixed income securities include primarily corporate bonds from a diversified range of companies, U . S . Treasuries and agency securities and money market instruments. Our investment strategy for fixed income investments is to maintain a high grade portfolio of securities, which assists us in managing the volatility and magnitude of plan contributions and expense while maintaining sufficient cash and short-term investments to pay near-term benefits and expenses. The Oncor Retirement Plan’s investments are managed in two pools: one pool associated with the recoverable service portion of plan obligations related to Oncor’s regulated utility business, and a second pool associated with the non-recoverable service portion of plan obligations not related to Oncor’s regulated utility business. Each pool is invested in a broadly diversified portfolio as shown below. The second pool represents about 31% of total investments at December 31, 2017.  The target asset allocation ranges of the pension plan s investments by asset category are as follows:   Target Allocation Ranges  Asset Category Recoverable Non-recoverable   International equities 13% - 21% 5% - 9%  U.S. equities 16% - 24% 6% - 10%  Real estate 3% - 6% -  Credit strategies 5% - 9% 4% - 6%  Fixed income 45% - 57% 76% - 84%  Our investment objective for the OPEB p lan primarily follows the objectives of the pension plans discussed above, while maintaining sufficient cash and short-term investments to pay near-term benefits and expenses. The actual amounts at December 31, 201 7 provided below are consistent with the asset allocation targets.  Fair Value Measurement of Pension Plan s Assets  At December 31, 201 7 and 201 6 , pension plan s assets measured at fair value on a recurring basis consisted of the following:   At December 31, 2017  Level 1 Level 2 Level 3 Total   Asset Category  Interest-bearing cash $ - $ 11 $ - $ 11  Equity securities:  U.S. 235 2 - 237  International 271 - - 271  Fixed income securities:  Corporate bonds (a) - 1,081 - 1,081  U.S. Treasuries - 251 - 251  Other (b) - 44 - 44  Real estate - - 3 3  Total assets in the fair value hierarchy $ 506 $ 1,389 $ 3 1,898  Total assets measured at net asset value (c) 702  Total fair value of plan assets $ 2,600   At December 31, 2016  Level 1 Level 2 Level 3 Total   Asset Category  Interest-bearing cash $ - $ 14 $ - $ 14  Equity securities:  U.S. 193 3 - 196  International 225 - - 225  Fixed income securities:  Corporate bonds (a) - 1,089 - 1,089  U.S. Treasuries - 223 - 223  Other (b) - 40 - 40  Real estate - - 5 5  Total assets in the fair value hierarchy $ 418 $ 1,369 $ 5 $ 1,792  Total assets measured at net asset value (c) 495  Total fair value of plan assets $ 2,287 _____________ (a) Substantially all corporate bonds are rated investment grade by a major ratings agency such as Moody’s. (b) Other consists primarily of municipal bonds, emerging market debt, bank loans and fixed income derivative instruments. (c) Fair value was measured using the net asset value (NAV) per share as a practical expedient as the investments did not have a readily determinable fair value and are not required to be classified in the fair value hierarchy. The NAV fair value amounts presented here are intended to permit a reconciliation to the total fair value of plan assets.  The decrease in the fair value of the Level 3 assets was due to the sale of a portion of the investments.   Fair Value Measurement of OPEB P lan Assets  At December 31, 201 7 and 201 6, OPEB p lan assets measured at fair value on a recurring basis consisted of the following:   At December 31, 2017  Level 1 Level 2 Level 3 Total   Asset Category  Interest-bearing cash $ 1 $ 1 $ - $ 2  Equity securities:  U.S. 35 - - 35  International 33 - - 33  Fixed income securities:  Corporate bonds (a) - 30 - 30  U.S. Treasuries - 3 - 3  Other (b) 28 1 - 29  Total assets in the fair value hierarchy $ 97 $ 35 $ - 132  Total assets measured at net asset value (c) 17  Total fair value of plan assets $ 149   At December 31, 2016  Level 1 Level 2 Level 3 Total   Asset Category  Interest-bearing cash $ 2 $ - $ - $ 2  Equity securities:  U.S. 41 - - 41  International 28 - - 28  Fixed income securities:  Corporate bonds (a) - 28 - 28  U.S. Treasuries - 2 - 2  Other (b) 28 - - 28  Total assets in the fair value hierarchy $ 99 $ 30 $ - 129  Total assets measured at net asset value (c) 14  Total fair value of plan assets $ 143 _____________ (a) Substantially all corporate bonds are rated investment grade by a major ratings agency such as Moody’s. (b) Other consists primarily of diversified bond mutual funds. (c) Fair value was measured using the net asset value (NAV) per share as a practical expedient as the investments did not have a readily determinable fair value and are not required to be classified in the fair value hierarchy. The NAV fair value amounts presented here are intended to permit a reconciliation to the total fair value of plan assets.  Expected Long-Term Rate of Return on Assets Assumption  The retirement plans’ strategic asset allocation is determined in conjunction with the plans’ advisors and utilizes a comprehensive Asset-Liability modeling approach to evaluate potential long-term outcomes of various investment strategies. The modeling incorporates long-term rate of return assumptions for each asset class based on historical and future expected asset class returns, current market conditions, rate of inflation, current prospects for economic growth, and taking into account the diversification benefits of investing in multiple asset classes and potential benefits of employing active investment management.    Pension Plans OPEB Plan  Asset Class Expected Long-Term Rate of Return Asset Class Expected Long-Term Rate of Return   International equity securities 7.33% 401(h) accounts 6.51%  U.S. equity securities 6.40% Life insurance VEBA 6.13%  Real estate 5.60% Union VEBA 6.13%  Credit strategies 5.03% Non-union VEBA 2.60%  Fixed income securities 4.20% Weighted average 6.20%  Weighted average (a) 5.48% _____________ (a) The 2018 expected long-term rate of return for the nonregulated portion of the Oncor Retirement Plan is 4.36% and 4.78% for Oncor's portion of the Vistra Retirement Plan.  Significant Concentrations of Risk  The plans’ investments are exposed to risks such as interest rate, capital market and credit risks. We seek to optimize return on investment consistent with levels of liquidity and investment risk which are prudent and reasonable, given prevailing capital market conditions and other factors specific to participating employers. While we recognize the importance of return, investments will be diversified in order to minimize the risk of large losses unless, under the circumstances, it is clearly prudent not to do so. There are also various restrictions and guidelines in place including limitations on types of investments allowed and portfolio weightings for certain investment securities to assist in the mitigation of the risk of large losses.  Assumed Discount Rate  For the Oncor retirement plans at December 31, 201 7 , we selected the assumed discount rate using the Aon Hewitt AA-AAA Bond Universe yield curve, which is based on corporate bond yields and at December 31, 201 7 consisted of 1,029 corporate bonds with an average rating of AA and AAA using Moody’s, S&P and Fitch ratings. For the Oncor OPEB Plan at December 31, 201 7 , we selected the assumed discount rate using the Aon Hewitt AA Above Median yield curve, which is based on corporate bond yields and at December 31, 201 7 consisted of 391 corporate bonds with an average rating of AA using Moody’s, S&P and Fitch ratings.  Amortization in 201 8  In 2018, amortization of the net actuarial loss for the defined benefit pension plans from regulatory assets and other comprehensive income into net periodic benefit cost is expected to be $45 million and $ 4 million, respectively. No amortization of prior service credit is expected in 2018 for the defined benefit pension plans. Amortization of the net actuarial loss for the OPEB plan from regulatory assets and other comprehensive income into net periodic benefit cost is expected to be $56 million and $1 million, respectively. Amortization of prior service credit for the OPEB plan from regulatory assets and other comprehensive income into net periodic benefit cost is expected to be $30 million and zero , respectively.  Pension and OPEB Plan s Cash Contributions  Our contributions to the benefit plans were as follows:   Year Ended December 31,  2017 2016 2015   Pension plans contributions $ 149 $ 4 $ 54  OPEB plan contributions 31 31 25  Total contributions $ 180 $ 35 $ 79  Our funding for the pension plans and the Oncor OPEB P lan is expected to total $82 million and $35 million, respectively in 201 8 and approximately $556 million and $178 million, respectively, in the 201 8 to 20 22 period.  Future Benefit Payments  Estimated future benefit payments to participants are as follows:   2018 2019 2020 2021 2022 2023-27   Pension plans $ 186 $ 187 $ 192 $ 197 $ 200 $ 1,050  OPEB plan $ 56 $ 59 $ 62 $ 65 $ 68 $ 351  Thrift Plan  Our employees are eligible to participate in a qualified savings plan, a participant-directed defined contribution plan intended to qualify under Section 401(a) of the Code, and is subject to the provisions of ERISA. Under the p lan, employees may contribute, through pre-tax salary deferrals and/or after-tax applicable payroll deductions, a portion of t heir regular salary or wages as permitted under law. Employer matching contributions are made in an amount equal to 100% of the first 6% of employee contributions for employees who are covered under the Cash Balance Formula of the Oncor Retirement Plan, and 75% of the first 6% of employee contributions for employees who are covered under the Traditional Retirement Plan Formula of the Oncor Retirement Plan. Employer matching contributions are made in cash and may be allocated by participants to any of the plan's investment options. Our contributions to the Oncor Thrift Plan totaled $17 million, $15 million and $14 million for the years ended December 31, 2017, 2016 and 2015, respectively.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2017
Stock-Based Compensation [Abstract]
STOCK-BASED COMPENSATION	11. STOCK-BASED COMPENSATION  We currently do not offer stock-based compensation to our employees or directors. In 2008, we established the SARs Plan under which certain of our executive officers and key employees were granted stock appreciation rights payable in cash, or in some circumstances, Oncor membership interests. In February 2009, we established the Oncor Electric Delivery Company LLC Director Stock Appreciation Rights Plan (the Director SARs Plan) under which certain non-employee members of our board of directors and other persons having a relationship with us were granted SARs payable in cash, or in some circumstances, Oncor membership interests.  In November 2012, we accepted the early exercise of all outstanding SARs (both vested and unvested ) issued to date pursuant to both SARs Plans. As part of the 2012 early exercise of SARs we began accruing interest on dividends declared with respect to the SARs. Under both SARs plans, dividends that were paid in respect of Oncor membership interests while the SARs were outstanding were credited to the SARs holder’s account as if the SARs were units, payable upon the earliest to occur of death, disability, separation from service, unforeseeable emergency, a change in control, or the occurrence of an event triggering SAR exercisability pursuant to Section 5(c)(ii) of the SARs Plan . As a result, at December 31, 2017, we have recorded a liability of approx imately $11 million relating to SARS dividend accruals. For accounting purposes, the liability is discounted based on an employee’s or director’s expected retirement date . We recognized approximately $1 million in accretion and interest with respect to such dividends in each of the years 201 7 , 201 6 and 201 5. 

Related-Party Transactions

Related-Party Transactions	12 Months Ended
	Dec. 31, 2017
Related-Party Transactions [Abstract]
RELATED-PARTY TRANSACTIONS	1 2 . RELATED-PARTY TRANSACTIONS  The following represent our significant related-party transactions and related matters . See Note 2 for additional information regarding related-party contingencies resulting from the EFH Bankruptcy Proceedings and information regarding the Vistra Spin-Off. As a result of the Vistra Spin-Off, Vistra and its subsidiaries, including Luminant and TXU Energy, ceased to be related parties as of October 3, 2016.  · We recorded revenue from TCEH, principally for electricity delivery fees, which totaled $715 million for the period January 1, 2016 through October 2, 2016 and $955 million for the year ended December 31, 2015 . The fees are based on rates regulated by the PUCT that apply to all REPs.    · EFH Corp. subsidiaries charge d us for certain administrative services at cost. Our payments to EFH Corp. subsidiaries for administrative services, which are primarily reported in operation and maintenance expenses, totaled $1 million and $17 million for the years ended December 31, 201 6 and 201 5 , respectively. We also charge each other for shared facilities at cost. Our payments to EFH Corp. subsidiaries for shared facilities totale d $3 million and $4 million for the year s ended December 31, 2016 and 2015, respectively . Payments we received from EFH Corp. subsidiaries related to shared facilities, totaled $1 million and $2 million for the years ended December 31, 2016 and 201 5, respectively .  · We are not a member of EFH Corp.’s consolidated tax group, but EFH Corp.’s consolidated federal income tax return includes EFH Corp.’s portion of our results due to EFH Corp.’s equity ownership in us. Under the terms of a tax sharing agreement among us, Oncor Holdings, Texas Transmission, Investment LLC and EFH Corp., we are generally obligated to make payments to Texas Transmission, Investment LLC and EFH Corp., pro rata in accordance with their respective membership interests, in an aggregate amount that is substantially equal to the amount of federal income taxes that we would have been required to pay if we were filing our own corporate income tax return. EFH Corp. also includes our results in its consolidated Texas margin tax payments, which we account for as income taxes and calculate as if we were filing our own return. See discussion in Note 1 under “ Provision in Lieu of Income Taxes.” Under the “in lieu of” tax concept, all in lieu of tax assets and tax liabilities represent amounts that will eventually be settled with our members. In the event such amounts are not paid under the tax sharing agreement, it is probable that this regulatory liability will continue to be included in Oncor’s rate setting processes .  Amounts payable to (receivable from) members related to income taxes under the agreement and reported on our balance sheet consisted of the following:    At December 31, 2017 At December 31, 2016  EFH Corp. Texas Transmission Total EFH Corp. Texas Transmission Total   Federal income taxes receivable $ (21) $ (5) $ (26) $ (62) $ (18) $ (80)  Texas margin taxes payable 21 - 21 20 - 20  Net payable (receivable) $ - $ (5) $ (5) $ (42) $ (18) $ (60)  Cash payments made to (received from) members related to income taxes consisted of the following:   Year Ended December 31, 2017 Year Ended December 31, 2016 Year Ended December 31, 2015  EFH Corp. Texas Transm. Total EFH Corp. Texas Transm. Total EFH Corp. Texas Transm. Total   Federal income taxes $ (102) $ (12) $ (114) $ - $ - $ - $ 108 $ 27 $ 135  Texas margin taxes 20 - 20 20 - 20 24 - 24  Total payments (receipts) $ (82) $ (12) $ (94) $ 20 $ - $ 20 $ 132 $ 27 $ 159  · Related parties of the Sponsor Group have (1) sold, acquired or participated in the offerings of our debt or debt securities in open market transactions or through loan syndications, and (2) performed various financial advisory, dealer, commercial banking and investment banking services for us and certain of our affiliates for which they have received or will receive customary fees and expenses, and may from time to time in the future participate in any of the items in (1) and (2) above. Also, as of December 31, 2017, approximately 16% of the equity in an existing vendor of the company was owned by a member of the Sponsor Group . During 2017 and 2016, this vendor performed transmission and distribution system construction and maintenance services for us. Cash payments were made for such services to this vendor and/or its subsidiaries totaling $219 million for 201 7, of which approximately $210 million was capitalized and $9 million recorded as an operation and maintenance expense, and $188 million for 201 6, of which approximately $180 million was capitalized and $8 million recorded as an operation and maintenance expense. At December 31, 2017 and 2016, we had outstanding trade payables to this vendor of $7 million and $5 million, respectively.  See Notes 1, 4 , 9 and 10 for information regarding the tax sharing agreement, distributions to members and our participation in the Vistra Retirement Plan .

Supplementary Financial Informa

Supplementary Financial Information	12 Months Ended
	Dec. 31, 2017
Supplementary Financial Information [Abstract]
SUPPLEMENTARY FINANCIAL INFORMATION	13 . SUPPLEMENTARY FINANCIAL INFORMATION  Variable Interest Entities  Through December 29, 2016, we were the primary beneficiary and consolidated a former wholly-owned VIE, Bondco, which was organized for the limited purpose of issuing specific transition bonds and purchasing and owning transition property acquired from us that was pledged as collateral to secure the bonds. We acted as the servicer for this entity to collect transition charges authorized by the PUCT. These funds were remitted to the trustee and used for interest and principal payments on the transition bonds and related costs. Bondco was dissolved effective December 29, 2016.  Bondco had issued an aggregate $1.3 billion principal amount of transition bonds during 2003 and 2004. The 2003 Series transition bonds matured and were paid in full in 2015 and the 2004 Series transition bonds matured and were paid in full in May 2016. We did not provide any financial support to Bondco during the year ended Decemb er 31, 2016.  Major Customers  Revenues from subsidiaries of Vistra (formerly subsidiaries of TCEH) represented 22% , 23 % and 25 % of our total operating revenues for the years ended December 31, 201 7 , 201 6 and 201 5 , respectively. Revenues from REP subsidiaries of a nother nonaffiliated entity, collectively represented 18% , 17% and 17% of total operating revenues for the years ended December 31, 201 7 , 201 6 and 201 5 , respectively. No other customer represented 10 % or more of our total operating revenues.  Other Income and Deductions  Year Ended December 31,  2017 2016 2015   Accretion of fair value adjustment (discount) to regulatory assets due to acquisition accounting $ - $ 1 $ 5  Professional fees (15) (15) (19)  Non-recoverable pension and OPEB (Note 9) (5) (2) (9)  Interest income 6 2 -  Other (1) (1) 1  Total other income and (deductions) - net $ (15) $ (15) $ (22)  Interest Expense and Related Charges   Year Ended December 31,  2017 2016 2015   Interest $ 351 $ 341 $ 335  Amortization of debt issuance costs and discounts 3 3 3  Less allowance for funds used during construction – capitalized interest portion (12) (8) (5)  Total interest expense and related charges $ 342 $ 336 $ 333  Trade Accounts and Other Receivable s  Trade a ccounts and other r eceivable s reported on our balance sheet consisted of the following:   At December 31,  2017 2016   Gross trade accounts and other receivables $ 638 $ 548  Allowance for uncollectible accounts (3) (3)  Trade accounts receivable – net $ 635 $ 545  At December 31, 201 7 , REP subsidiaries of two of our largest counterparties collectively represented approximately 12% and 10% of the trade accounts receivable balance and at December 31, 201 6 , r epresented app roximately 15% a nd 12% of the trade accounts receivable balance .  Under a PUCT rule relating to the Certification of Retail Electric Providers, write-offs of uncollectible amounts owed by nonaffiliated REPs are deferred as a regulatory asset.  Investments and Other Property  Investments and other property reported on our balance sheet consist of the following:   At December 31,  2017 2016   Assets related to employee benefit plans, including employee savings programs $ 111 $ 98  Land 2 2  Total investments and other property $ 113 $ 100  The majority of these assets represent cash surrender values of life insurance policies that are purchased to fund liabilities under deferred compensation plans. At December 31, 201 7 and 201 6 , the face amount of these policies totaled $162 million and $153 million, respectively, and the net cash surrender values (determined using a Level 2 valuation technique) totaled $84 million an d $76 mi llion for the years ended December 31, 2017 and 2016, respectively. Changes in cash surrender value are netted against premiums paid. Other investment assets held to satisfy deferred compensation liabilities are recorded at market value.  Property, Plant and Equipment  Property, plant and equipment reported on our balance sheet consisted of the following:    Composite Depreciation Rate/ At December 31,  Avg. Life at December 31, 2017 2017 2016  Assets in service:  Distribution 2.9% / 34.3 years $ 12,467 $ 11,369  Transmission 2.9% / 34.7 years 7,870 7,734  Other assets 7.1% / 14.1 years 1,380 1,131  Total 21,717 20,234  Less accumulated depreciation 7,255 6,836  Net of accumulated depreciation 14,462 13,398  Construction work in progress 402 416  Held for future use 15 15  Property, plant and equipment – net $ 14,879 $ 13,829  Depreciation expense as a percent of average depreciable property approximated 3.4% , 3.5% and 3.6% for the years ended December 31, 2017, 2016 and 2015, respectively.  Intangible Assets  Intangible assets (other than goodwill) reported on our balance sheet as part of property, plant and equipment consisted of the following:   At December 31, 2017 At December 31, 2016  Gross Gross  Carrying Accumulated Carrying Accumulated  Amount Amortization Net Amount Amortization Net  Identifiable intangible assets subject to amortization:  Land easements $ 453 $ 96 $ 357 $ 491 $ 94 $ 397  Capitalized software 679 339 340 470 326 144  Total $ 1,132 $ 435 $ 697 $ 961 $ 420 $ 541  A ggregate amortization expense for intangible assets totaled $57 million , $61 million and $64 million for the years ended December 31, 201 7 , 201 6 and 201 5, respectively . At December 31, 201 7 , the weighted average remaining useful lives of capitalized land easements and software were 82 years and 8 years, respectively. The estimated aggregate amortization expense for each of the next five fiscal years is as follows:   Year Amortization Expense   2018 $ 47  2019 44  2020 43  2021 43  2022 43  At both December 31, 201 7 and 201 6 , goodwill totaling $ 4.1 billion was reported on our balance sheet. None of this goodwill is being deducted for tax purposes. See Note 1 regarding goodwill impairment assessment and testing.  Employee Benefit Obligations and Other  Employee benefit obligations and other reported on our balance sheet consisted of the following:   At December 31,  2017 2016   Retirement plans and other employee benefits $ 2,035 $ 2,092  Uncertain tax positions (including accrued interest) - 3  Investment tax credits 10 12  Other 57 61  Total employee benefit obligations and other $ 2,102 $ 2,168  Supplemental Cash Flow Information   Year Ended December 31,  2017 2016 2015  Cash payments related to:   Interest $ 345 $ 336 $ 346  Less capitalized interest (12) (8) (5)  Interest payments (net of amounts capitalized) $ 333 $ 328 $ 341   Amount in lieu of income taxes:  Federal $ (114) $ - $ 135  State 20 20 43  Total payments (refunds) in lieu of income taxes $ (94) $ 20 $ 178   Noncash Sharyland Asset Exchange costs $ 383 $ - $ -  Noncash construction expenditures (a) $ 129 $ 122 $ 56 ______________ (a) Represents end-of-period accruals.  Quarterly Information (unaudited)  Results of operations by quarter for the years ended December 31, 2017 and 2016 are summarized below. In our opinion, all adjustments (consisting of normal recurring accruals) necessary for a fair statement of such amounts have been made. Quarterly results are not necessarily indicative of a full year’s operations because of seasonal and other factors.   2017 First Quarter Second Quarter Third Quarter Fourth Quarter  Operating revenues $ 935 $ 964 $ 1,068 $ 991  Operating income 160 197 247 184  Net income 73 112 157 77   2016 First Quarter Second Quarter Third Quarter Fourth Quarter  Operating revenues $ 943 $ 948 $ 1,071 $ 958  Operating income 169 196 250 162  Net income 81 110 163 77 

Sharyland Asset Exchange

Sharyland Asset Exchange	12 Months Ended
	Dec. 31, 2017
Sharyland Asset Exchange [Abstract]
Sharyland Asset Exchange	14. S HARYLAND ASSET EXCHANGE  On July 21, 2017, we entered into the Sharyland Agreement with the Sharyland Entities. The Sharyland Agreement provided that we would exchange certain of our transmission assets and cash for certain of the Sharyland Entities’ distribution assets (constituting substantially all of their electricity distribution business) and certain of their transmission assets. The transaction for assets between Oncor and SDTS was structured to qualify, in part, as a simultaneous tax deferred like kind exchange of assets to the extent that the assets exchanged are of “like kind” (within the meaning of Section 1031 of the Code).  On August 4, 2017, we , SDTS and SU filed a joint application for sale, transfer, or merger in PUCT Docket No. 47469 requesting PUCT approval of the Sharyland Asset Exchange, and on October 13, 2017, the PUCT issued an order approving the transactions. On November 9, 2017, the parties consummated the transactions. We exchanged approximately $383 million of our transmission assets, consisting of approximately 258 miles ( 517 circuit miles) of 345 kV transmission lines, and approximately $25 million in cash for approximately $408 million of the Sharyland Entities’ distribution assets and certain of their transmission assets.  The transaction expanded our customer base in west Texas and provides some potential growth opportunities of the distribution network. As part of the transaction, we acquired approximately 55,000 customers. The acquisition did not result in the recognition of goodwill as the assets’ regulatory book value approximates their fair value.  Distribution revenues following the November 9, 2017 Sharyland Asset Exchange included in our 2017 consolidated results are $12 million. Earnings of the Sharyland distribution assets we acquired are largely offset by a reduction in earnings attributable to the transfer of transmission assets. The Sharyland Asset Exchange did not have a material effect on our results of operations, financial position or cash flows for the year ended December 31, 2017. Had the Sharyland Asset Exchange occurred at the beginning of the 2017 annual reporting period, the revenue and earnings of the combined entity for the current reporting period would not have been significantly different.     

Description Of Business and S24

Description Of Business and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Description Of Business and Significant Accounting Policies [Abstract]
Description Of Business	Description of Business  References in this report to “we,” “our,” “us” and “the company” are to Oncor and/or its subsidiary as apparent in the context. See “Glossary” for definition of terms and abbreviations.  We are a regulated electricity transmission and distribution company principally engaged in providing delivery services to REPs that sell power in the north-central, eastern and western parts of Texas. Revenues from subsidiaries of Vistra (formerly subsidiaries of TCEH) represented 22% , 23% and 25% of our total operating revenues for the years ended December 31, 2017, 2016 and 2015, respectively. We are a direct, majority-owned subsidiary of Oncor Holdings, which is a direct, wholly-owned subsidiary of EFIH, a direct, wholly-owned subsidiary of EFH Corp. EFH Corp. is a subsidiary of Texas Holdings, which is controlled by the Sponsor Group. Oncor Holdings owns 80.03% of our membership interests, Texas Transmission owns 19.75% of our membership interests and certain members of our management team and board of directors indirectly own the remaining membership interests through Investment LLC. We are managed as an integrated business; consequently, there are no separate reportable business segments.  Our consolidated financial statements include our former wholly-owned, bankruptcy-remote financing subsidiary, Bondco, a VIE through December 29, 2016, at which time it was dissolved (see Note 13) . This financing subsidiary was organized for the limited purpose of issuing certain transition bonds to recover generation-related regulatory asset stranded costs and other qualified costs under an order issued by the PUCT in 2002. Bondco issued an aggregate $1.3 billion principal amount of transition bonds during 2003 and 2004. The 2003 Series transition bonds matured and were paid in full in 2015 and the 2004 Series transition bonds matured and were paid in full in May 2016. Final true-up proceedings and refunds of over-collected transition charges for the transition bonds were conducted by Oncor and the PUCT during 2016 and had no material net income impact.  Various “ring-fencing” measures have been taken to enhance the separateness between the Oncor Ring-Fenced Entities and the Texas Holdings Group and our credit quality. These measures serve to mitigate our and Oncor Holdings’ credit exposure to the Texas Holdings Group and to reduce the risk that our assets and liabilities or those of Oncor Holdings would be substantively consolidated with the assets and liabilities of the Texas Holdings Group in connection with a bankruptcy of one or more of those entities, including the EFH Bankruptcy Proceedings discussed below. Such measures include, among other things: our sale of a 19.75% equity interest to Texas Transmission in November 2008; maintenance of separate books and records for the Oncor Ring-Fenced Entities; our board of directors being comprised of a majority of independent directors; and prohibitions on the Oncor Ring-Fenced Entities providing credit support to, or receiving credit support from, any member of the Texas Holdings Group. The assets and liabilities of the Oncor Ring-Fenced Entities are separate and distinct from those of the Texas Holdings Group. None of the assets of the Oncor Ring-Fenced Entities are available to satisfy the debt or contractual obligations of any member of the Texas Holdings Group. We do not bear any liability for debt or contractual obligations of the Texas Holdings Group, and vice versa. Accordingly, our operations are conducted, and our cash flows are managed, independently from the Texas Holdings Group.  In the PUCT proceedings requesting approval of the Sempra Acquisition (PUCT Docket No. 47675), Sempra has committed to certain ring-fencing measures that will be in effect upon closing of the Sempra Acquisition. For more information on the Sempra Acquisition and the related PUCT proceedings, see Note 2.
EFH Corp. Bankruptcy Proceedings	EFH Bankruptcy Proceedings  On the EFH Petition Date, EFH Corp. and the substantial majority of its direct and indirect subsidiaries at the time, including EFIH, EFCH and TCEH, commenced proceedings under Chapter 11 of the U.S. Bankruptcy Code. The Oncor Ring-Fenced Entities are not parties to the EFH Bankruptcy Proceedings. We believe the “ring-fencing” measures discussed above mitigate our potential exposure to the EFH Bankruptcy Proceedings. See Note 2 for a discussion of the potential impacts of the EFH Bankruptcy Proceedings on our financial statements.
Basis Of Presentation	Basis of Presentation  Our consolidated financial statements have been prepared in accordance with GAAP. All dollar amounts in the financial statements and tables in the notes are stated in millions of U.S. dollars unless otherwise indicated.
Use Of Estimates	Use of Estimates  Preparation of our financial statements requires management to make estimates and assumptions about future events that affect the reporting of assets and liabilities at the balance sheet dates and the reported amounts of revenue and expense, including fair value measurements. In the event estimates and/or assumptions prove to be different from actual amounts, adjustments are made in subsequent periods to reflect more current information. No material adjustments were made to previous estimates or assumptions during the current year.
Revenue Recognition	Revenue Recognition  General  Oncor’s revenu e is billed under tariffs approved by the PUCT and the majority of revenues are related to providing electric delivery service to consumers. Tariff rates are designed to recover the cost of providing electric delivery service including a reasonable rate of return on invested capital. Revenues are generally recognized when the underlying service has been provided in an amount prescribed by the related tariff.  Reconcilable Tariffs  The PUCT has designated certain tariffs (TCRF, EECRF surcharges, AMS surcharges and charges related to transition bonds) as reconcilable, which means the differences between amounts billed under these tariffs and the related incurred costs are deferred as either regulatory assets or regulatory liabilities. Accordingly, at prescribed intervals, future tariffs are adjusted to either repay regulatory liabilities or collect regulatory assets. See “Regulatory Assets and Liabilities” below.
Impairment Of Long-Lived Assets And Goodwill	Impairment of Long-Lived Assets and Goodwill  We evaluate long-lived assets (including intangible assets with finite lives) for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable.  We also evaluate goodwill for impairment annually (at December 1) and whenever events or changes in circumstances indicate that an impairment may exist. The determination of the existence of these and other indications of impairment involves judgments that are subjective in nature and may require the use of estimates in forecasting future results and cash flows.  If at the assessment date our carrying value exceeds our estimated fair value (enterprise value), then the estimated enterprise value is compared to the estimated fair values of our operating assets (including identifiable intangible assets) and liabilities at the assessment date. The resultant implied goodwill amount is compared to the recorded goodwill amount. Any excess of the recorded goodwill amount over the implied goodwill amount is written off as an impairment charge.  The goodwill impairment tests performed in 201 7 , 201 6 and 201 5 were based on a qualitative assessment in which we considered macroeconomic conditions, industry and market considerations, cost factors, overall financial performance and other relative factors . Based on tests results, no impairments were recognized in 201 7 , 201 6 or 201 5 .
Provision In Lieu Of Income Taxes	Provision in Lieu of Income Taxes  Effective with the November 2008 sale of equity interests to Texas Transmission and Investment LLC, we became a partnership for U.S. federal income tax purposes, and subsequently we are not a member of EFH Corp.’s consolidated tax group and only EFH Corp.’s share of our partnership income is included in its consolidated federal income tax return. Our tax sharing agreement with Oncor Holdings and EFH Corp. was amended in November 2008 to include Texas Transmission and Investment LLC. The tax sharing agreement provides for the calculation of tax liability substantially as if we and Oncor Holdings were taxed as corporations, and requires tax payments to members determined on that basis (without duplication for any income taxes paid by a subsidiary of Oncor Holdings).  While partnerships are not subject to income taxes, in consideration of the tax sharing agreement and the presentation of our financial statements as an entity subject to cost-based regulatory rate-setting processes, with such costs including income taxes, the financial statements present amounts determined under the tax sharing agreement as “provision in lieu of income taxes” and “liability in lieu of deferred income taxes” for periods subsequent to the sales of equity interests discussed in Note 4. Such amounts are determined in accordance with the provisions of accounting guidance for income taxes and for uncertainty in income taxes and thus differences between the book and tax bases of assets and liabilities are accounted for as if we were taxed as a corporation. The accounting guidance for rate-regulated enterprises requires the recognition of regulatory assets or liabilities if it is probable such deferred tax -related amounts will be recovered from, or returned to customers in future rates. Investment tax credits are amortized to income over the estimated lives of the related properties.  We classify interest and penalties expense related to uncertain tax positions as current provision in lieu of income taxes as discussed in Note 4.
Defined Benefit Pension Plans And OPEB Plans	Defined Benefit Pension Plans and OPEB Plans  We have liabilities under pension plans that offer benefits based on either a traditional defined benefit formula or a cash balance formula and an OPEB plan that offers certain health care and life insurance benefits to eligible employees and their eligible dependents upon the retirement of such employees from the company. Costs of pension and OPEB plans are dependent upon numerous factors, assumptions and estimates. See Note 10 for additional information regarding pension and OPEB plans.
Contingencies	Contingencies  We evaluate and account for contingencies using the best information available. A loss contingency is accrued and disclosed when it is probable that an asset has been impaired or a liability incurred and the amount of the loss can be reasonably estimated. If a range of probable loss is established, the minimum amount in the range is accrued, unless some other amount within the range appears to be a better estimate. If the probable loss cannot be reasonably estimated, no accrual is recorde d, but the loss contingency is disclosed to the effect that the probable loss cannot be reasonably estimated. A loss contingency will be disclosed when it is reasonably possible that an asset has been impaired or a liability incurred. If the likelihood that an impairment or incurrence is remote, the contingency is neither accrued nor disclosed. Gain contingencies are recognized upon realization.
System Of Accounts	System of Accounts  Our accounting records have been maintained in accordance with the FERC Uniform System of Accounts as adopted by the PUCT.
Property, Plant And Equipment	Property, Plant and Equipment  Properties are stated at original cost. The cost of self-constructed property additions includes materials and both direct and indirect labor and applicable overhead and an allowance for funds used during construction.  D epreciation of property, plant and equipment is calculated on a straight-line basis over the estimated service lives of the properties based on depreciation rates approved by the PUCT. As is common in the industry, depreciation expense is recorded using composite depreciation rates that reflect blended estimates of the lives of major asset groups as compared to depreciation expense calculated on a component asset-by-asset basis. Depreciation rates include plant removal costs as a component of depreciation expense, consistent with regulatory treatment. Actual removal costs incurred are charged to accumulated depreciation. When accrued removal costs exceed incurred removal costs, the difference is reclassified as a regulatory liability to retire assets in the future.
Regulatory Assets And Liabilities	Regulatory Assets and Liabilities  We are subject to rate regulation and o ur financial statements reflect regulatory assets and liabilities in accordance with accounting standards related to the effect of certain types of regulation. Regulatory assets and liabilities represent probable future revenues that will be recovered from or refunded to customers through the ratemaking process based on PURA and/or the PUCT’s orders, precedents or s ubstantive r ules. Rate regulation is premised on the full recovery of prudently incurred costs and a reasonable rate of return on invested capital subject to PUCT review for reasonableness and prudence and possible disallowance . Regulatory decisions can have an impact on the recovery of costs, the rate earned on invested capital and the timing and amount of assets to be recovered by rates. See Note 5 for more information regarding regulatory assets and liabilities. 
Franchise Taxes	 Franchise Taxes  Franchise taxes are assessed to us by local governmental bodies, based on kWh delivered and are a principal component of taxes other than amounts related to income taxes as reported in the income statement. Franchise taxes are not a “pass through” item. The rates we charge customers are intended to recover the franchise taxes, but we are not acting as an agent to collect the taxes from customers.
Allowance For Funds Used During Construction (AFUDC)	Allowance for Funds Used During Construction (AFUDC)  AFUDC is a regulatory cost accounting procedu re whereby both interest charges on borrowed funds and a return on equity capital used to finance construction are included in the recorded cost of utility plant and equipment being constructed. AFUDC is capitalized on all projects involving construction periods lasting greater than thirty days. The equity portion, if any, of capitalized AFUDC is accounted for as other income. See Note 13 for detail of amounts charged to interest expense.
Cash And Cash Equivalents	Cash and Cash Equivalents  For purposes of reporting cash and cash equivalents, temporary cash investments purchased with a remaining maturity of three months or less are considered to be cash equivalents.
Fair Value Of Nonderivative Financial Instruments	Fair Value of Nonderivative Financial Instruments  The carrying amounts for financial assets classified as current assets and the carrying amounts for financial liabilities classified as current liabilities approximate fair value due to the short maturity of such instruments. The fair values of other financial instruments, for which carrying amounts and fair values have not been presented, are not materially different than their related carrying amounts. The following discussion of fair value accounting standards applies primarily to our determination of the fair value of assets in the pension and OPEB plans trusts (see Note 10) and long-term debt (see Note 7).  Accounting standards related to the determination of fair value define fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. We use a “mid-market” valuation convention (the mid-point price between bid and ask prices) as a practical expedient to measure fair value for the majority of our assets and liabilities subject to fair value measurement on a recurring basis. We primarily use the market approach for recurring fair value measurements and use valuation techniques to maximize the use of observable inputs and minimize the use of unobservable inputs.  We categorize our assets and liabilities recorded at fair value based upon the following fair value hierarchy:  · Level 1 valuations use quoted prices in active markets for identical assets or liabilities that are accessible at the measurement date. An active market is a market in which transactions for the asset or liability occur with sufficient frequency and volume to provide pricing information on an ongoing basis.  · Level 2 valuations use inputs that, in the absence of actively quoted market prices, are observable for the asset or liability, either directly or indirectly. Level 2 inputs include: (a) quoted prices for similar assets or liabilities in active markets , (b) quoted prices for identical or similar assets or liabilities in markets that are not active, (c) inputs other than quoted prices that are observable for the asset or liability such as interest rates and yield curves observable at commonly quoted intervals and (d) inputs that are derived principally from or corroborated by observable market data by correlation or other means. Our Level 2 valuations utilize over-the-counter broker quotes, quoted prices for similar assets or liabilities that are corroborated by correlations or other mathematical means and other valuation inputs.  · Level 3 valuations use unobservable inputs for the asset or liability. Unobservable inputs are used to the extent observable inputs are not available, thereby allowing for situations in which there is little, if any, market activity for the asset or liability at the measurement date. We use the most meaningful information available from the market combined with internally developed valuation methodologies to develop our best estimate of fair value.  We utilize several different valuation techniques to measure the fair value of assets and liabilities, relying primarily on the market approach of using prices and other market information for identical and/or comparable assets and liabilities for those items that are measured on a recurring basis.  The fair value of certain investments is measured using the net asset value (NAV) per share as a practical expedient. Such investments measured at NAV are not required to be categorized within the fair value hierarchy. See “Changes in Accounting Standards” below.
Consolidation Of Variable Interest Entities	Consolidation of Variable Interest Entities  A VIE is an entity with which we have a relationship or arrangement that indicates some level of control over the entity or results in economic risks to us. We consolidate a VIE if we have: a) the power to direct the significant activities of the VIE and b) the right or obligation to absorb profit and loss from the VIE (primary beneficiary). See Note 13.
Derivative Instruments And Mark-To-Market Accounting	Derivative Instruments and Mark-to-Market Accounting  We have from time-to-time entered into derivative instruments to hedge interest rate risk. If the instrument meets the definition of a derivative under accounting standards related to derivative instruments and hedging activities, the fair value of each derivative is recognized on the balance sheet as a derivative asset or liability and changes in the fair value are recognized in net income, unless criteria for certain exceptions are met. This recognition is referred to as “mark-to-market” accounting.
Changes In Accounting Standards	Changes in Accounting Standards  Since May 2014, the Financial Accounting Standards Board (FASB) has issued Accounting Standards Update (ASU) 2014-09, Revenue from Contracts with Customers along with other supplemental guidance (together, Topic 606). Topic 606 introduces new, increased requirements for disclosure of revenue in financial statements and guidance that are intended to eliminate inconsistencies in the recognition of revenue. We will add a revenue-related note to the financial statements to satisfy the new disclosure requirements of Topic 606. Topic 606 also requires the separate presentation of “alternative revenue program” revenues on the income statement. We anticipate less than $20 million annually in alternative revenue program revenues related to our energy efficiency program and will disclose such activity in the notes to financial statements. We are required to adopt Topic 606 effective January 1, 2018. We will adopt using the modified retrospective approach and will elect certain practical expedients available under the guidance. Our revenues from customers are tariff-based and are designed to recover the cost of providing electric delivery service to customers including a reasonable rate of return on invested capital. Revenues are generally recognized when the underlying service has been provided in an amount prescribed by the related tariff. The new guidance does not change this pattern of recognition and therefore the adoption will not have an effect on our reported results of operations, financial position or cash flows.  In February 2016, the FASB issued ASU 2016-02 which created FASB Topic 842, Leases (Topic 842) . Topic 842 amends previous GAAP to require the balance sheet recognition of lease assets and liabilities for operating leases. Operating lease liabilities will not be classified as debt for GAAP purposes under Topic 842 and will not be treated as debt for regulatory purposes. At this time, all of Oncor’s existing leases meet the definition of an operating lease liability. Under the new rules, the recognition of any finance leases (currently known as capital leases) on the balance sheet would be classified as debt for GAAP purposes and are expected to be defined as debt for our regulatory capital structure purposes (see Note 9 for details) similar to the current capital lease treatment. We will be required to adopt Topic 842 by January 1, 2019. We expect to adopt at that time using certain practical expedients available under the transition guidance including a practical expedient to not assess whether existing land easements that were not previously accounted for as leases are or contain a lease under Topic 842. The initial adoption of Topic 842 will affect our balance sheet, as leased buildings and vehicles are recognized as operating lease liabilities. Subsequent to adoption, to the extent Oncor enters into finance leases, its credit facility covenants and capitalization ratios could be impacted. We continue to compile a population of contracts for assessment and evaluate the potential impact of Topic 842 on our financial statements.  In March 2017, the FASB issued ASU 2017-07 Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost , an amendment to Topic 715, Compensation – Retirement Benefits (Topic 715). Topic 715, as amended, will require the non-service cost components of net retirement benefit plan costs be presented as non-operating in the income statement. In addition, only the service cost component of net retirement benefit plan cost will be eligible for capitalization as part of inventory or property, plant and equipment. We are required to adopt the amendment effective January 1, 2018. The income statement presentation requirement must be applied on a retrospective basis while the capitalization eligibility requirement is applied on a prospective basis. The guidance allows a practical expedient that permits use of previously disclosed service costs and non-service costs from the Pension and OPEB Plans note in the comparative periods as appropriate estimates when retrospectively changing the presentation of these costs in the income statements. We will elect this practical expedient. For cash flow purposes on a prospective basis, non-service costs will be reflected as a reduction to operating cash flows, o ffset by lo wer cash used in investing activities (lower capital expenditures). W e do not expect the new guidance to have a material effect on our rate-making process, our results of operations, financial position or net change in total cash flows but continue to evaluate for potential impacts.

Provision In Lieu Of Income T25

Provision In Lieu Of Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Provision In Lieu Of Income Taxes [Abstract]
Schedule Of Deferred Tax Assets and Liabilities	  At Ended December 31,  2017 2016    Deferred Tax Related Assets:  Employee benefit liabilities $ 253 $ 413  Regulatory liabilities 15 26  Other 7 79  Total 275 518  Deferred Tax Related Liabilities:  Property, plant and equipment 1,551 2,892  Regulatory assets 240 412  Other 1 2  Total 1,792 3,306  Liability in lieu of deferred income taxes - net $ 1,517 $ 2,788 
Components Of Income Tax Provisions (Benefits)	  Year Ended December 31,  2017 2016 2015   Reported in operating expenses:  Current:  U.S. federal $ (55) $ 60 $ 189  State 20 20 32  Deferred:  U.S. federal 292 181 55  State - - (13)  Amortization of investment tax credits (2) (2) (3)  Total reported in operating expenses 255 259 260  Reported in other income and deductions:  Current:  U.S. federal (5) (5) (7)  State - - -  Deferred federal 17 - (1)  Total reported in other income and deductions 12 (5) (8)  Total provision in lieu of income taxes $ 267 $ 254 $ 252 
Schedule Of Income Tax Reconciliation	  Year Ended December 31,  2017 2016 2015   Income before provision in lieu of income taxes $ 686 $ 685 $ 684  Provision in lieu of income taxes at the U.S. federal statutory rate of 35% $ 240 $ 240 $ 239  Amortization of investment tax credits – net of deferred tax effect (2) (2) (3)  Amortization (under regulatory accounting) of statutory tax rate changes (1) (1) (1)  Impact of federal statutory rate change from 35% to 21% 21 - -  Texas margin tax, net of federal tax benefit 13 13 13  Nontaxable gains on benefit plan investments (4) - -  Other, including audit settlements - 4 4  Reported provision in lieu of income taxes $ 267 $ 254 $ 252  Effective rate 38.9% 37.1% 36.8% 
Schedule Of Changes To Uncertain Tax Positions	  2017 2016 2015    Balance at January 1, excluding interest and penalties $ 3 $ 3 $ 2  Additions based on tax positions related to prior years - - -  Reductions based on tax positions related to prior years (3) - -  Settlements with taxing authorities - - 1  Balance at December 31, excluding interest and penalties $ - $ 3 $ 3 

Regulatory Assets and Liabili26

Regulatory Assets and Liabilities (Tables)	12 Months Ended
	Dec. 31, 2017
Regulatory Assets and Liabilities [Abstract]
Components Of Regulatory Assets And Liabilities	  Remaining Rate Recovery/Amortization Period at Carrying Amount At  December 31, 2017 December 31, 2017 December 31, 2016   Regulatory assets:  Employee retirement costs being amortized 10 years $ 331 $ 23  Unrecovered employee retirement costs incurred since the last rate review period (b) To be determined 30 327  Employee retirement liability (a)(b)(c) To be determined 854 849  Self-insurance reserve (primarily storm recovery costs) being amortized 10 years 394 64  Unrecovered self-insurance reserve incurred since the last rate review period (b) To be determined 49 367  Securities reacquisition costs (post-industry restructure) Lives of related debt 12 13  Deferred conventional meter and metering facilities depreciation 3 years 57 78  Under-recovered AMS costs 10 years 206 209  Unprotected excess deferred taxes Various 197 -  Energy efficiency performance bonus (a) 1 year or less 12 10  Other regulatory assets Various 38 34  Total regulatory assets 2,180 1,974   Regulatory liabilities:  Estimated net removal costs Lives of related assets 954 819  Protected excess deferred taxes Various 1,595 3  Unprotected excess deferred taxes Various 194 -  Over-recovered wholesale transmission service expense (a) 1 year or less 47 10  Other regulatory liabilities Various 17 24  Total regulatory liabilities 2,807 856  Net regulatory assets (liabilities) $ (627) $ 1,118 ____________ (a) Not earning a return in the regulatory rate-setting process. (b) Recovery is specifically authorized by statute or by the PUCT, subject to reasonableness review. Represents unfunded liabilities recorded in accordance with pension and OPEB accounting standards.

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Long-Term Debt [Abstract]
Schedule Of Long-Term Debt	  December 31,  2017 2016   Secured:  5.000% Fixed Senior Notes due September 30, 2017 $ - $ 324  6.800% Fixed Senior Notes due September 1, 2018 550 550  2.150% Fixed Senior Notes due June 1, 2019 250 250  5.750% Fixed Senior Notes due September 30, 2020 126 126  4.100% Fixed Senior Notes due June 1, 2022 400 400  7.000% Fixed Debentures due September 1, 2022 800 800  2.950% Fixed Senior Notes due April 1, 2025 350 350  7.000% Fixed Senior Notes due May 1, 2032 500 500  7.250% Fixed Senior Notes due January 15, 2033 350 350  7.500% Fixed Senior Notes due September 1, 2038 300 300  5.250% Fixed Senior Notes due September 30, 2040 475 475  4.550% Fixed Senior Notes due December 1, 2041 400 400  5.300% Fixed Senior Notes due June 1, 2042 500 500  3.750% Fixed Senior Notes due April 1, 2045 550 550  3.800% Fixed Senior Notes due September 30, 2047 325 -  Secured long-term debt 5,876 5,875  Unsecured:  Term loan credit agreement due no later than March 26, 2019 275 -  Total long-term debt 6,151 5,875  Unamortized discount and debt issuance costs (34) (36)  Less amount due currently (550) (324)  Long-term debt, less amounts due currently $ 5,567 $ 5,515 
Schedule Of Long-Term Debt Maturity	  Year Amount  2018 $ 550  2019 525  2020 126  2021 -  2022 1,200  Thereafter 3,750  Unamortized discount and debt issuance costs (34)  Total $ 6,117 

Commitments And Contingencies (

Commitments And Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies [Abstract]
Schedule Of Future Miinimum Lease Payments Under Operating Leases	  Year Amount  2018 $ 32  2019 21  2020 14  2021 11  2022 10  Thereafter 1  Total future minimum lease payments $ 89 

Membership Interests (Tables)

Membership Interests (Tables)	12 Months Ended
	Dec. 31, 2017
Membership Interests [Abstract]
Schedule Of Distributions Paid	During 2017, our board of directors declared, and we paid, the following cash distributions to our members:   Declaration Date Payment Date Amount  July 26, 2017 August 1, 2017 $ 65  April 26, 2017 April 27, 2017 $ 86  March 22, 2017 March 24, 2017 $ 86  During 2016, our board of directors declared, and we paid, the following cash distributions to our members:  Declaration Date Payment Date Amount  October 26, 2016 October 27, 2016 $ 41  July 27, 2016 August 11, 2016 $ 68  April 27, 2016 May 11, 2016 $ 65  February 24, 2016 February 25, 2016 $ 56 
Schedule Of Changes To Accumulated Other Comprehensive Income (Loss)	The following table presents the changes to accumulated other comprehensive income (loss) for the years ended December 31, 2017, 2016 and 2015.   Cash Flow Hedges – Interest Rate Swap Defined Benefit Pension and OPEB Plans Accumulated Other Comprehensive Income (Loss)   Balance at December 31, 2014 $ (24) $ (83) $ (107)  Defined benefit pension plans (net of tax) - (8) (8)  Amounts reclassified from accumulated other comprehensive income (loss) and reported in interest expense and related charges 2 - 2  Balance at December 31, 2015 $ (22) $ (91) $ (113)  Defined benefit pension plans (net of tax) - - -  Amounts reclassified from accumulated other comprehensive income (loss) and reported in interest expense and related charges 2 - 2  Balance at December 31, 2016 $ (20) $ (91) $ (111)  Defined benefit pension plans (net of tax) - 8 8  Amounts reclassified from accumulated other comprehensive income (loss) and reported in interest expense and related charges 2 - 2  Balance at December 31, 2017 $ (18) $ (83) $ (101)   

Pension and OPEB Plans (Tables)

Pension and OPEB Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Schedule Of Pension And OPEB Plan Costs	  Year Ended December 31,  2017 2016 2015   Pension costs $ 85 $ 76 $ 104  OPEB costs 58 62 53  Total benefit costs 143 138 157  Less amounts recognized principally as property or a regulatory asset (98) (100) (113)  Net amounts recognized as expense $ 45 $ 38 $ 44 
Schedule Of Assumptions Used And Net Periodic Benefit Cost Not Yet Recognized And Amounts Recognized In Other Comprehensive Income (Loss)	  Pension Plans OPEB Plan  Year Ended December 31, Year Ended December 31,  2017 2016 2015 2017 2016 2015   Assumptions Used to Determine Net Periodic Pension and OPEB Costs:  Discount rate 4.05% 4.30% 3.96% 4.35% 4.60% 4.23%  Expected return on plan assets 5.17% 5.54% 5.26% 6.10% 6.30% 6.65%  Rate of compensation increase 3.33% 3.29% 3.29% - - -   Components of Net Pension and OPEB Costs:  Service cost $ 24 $ 23 $ 25 $ 7 $ 7 $ 7  Interest cost 131 134 131 47 49 43  Expected return on assets (115) (122) (115) (8) (9) (10)  Amortization of prior service cost (credit) - - - (20) (20) (20)  Amortization of net loss 45 41 63 32 35 33  Net periodic pension and OPEB costs $ 85 $ 76 $ 104 $ 58 $ 62 $ 53   Other Changes in Plan Assets and Benefit Obligations Recognized as Regulatory Assets or in Other Comprehensive Income:  Net loss (gain) $ (11) $ 41 $ 37 $ 139 $ 10 $ 39  Amortization of net loss (45) (41) (63) (32) (35) (33)  Plan amendments - - - (78) - -  Amortization of prior service (cost) credit - - - 20 20 20  Total recognized as regulatory assets or other comprehensive income (56) - (26) 49 (5) 26  Total recognized in net periodic pension and OPEB costs and as regulatory assets or other comprehensive income $ 29 $ 76 $ 78 $ 107 $ 57 $ 79 
Schedule Of Assumptions Used	 Pension Plans OPEB Plan  Year Ended December 31, Year Ended December 31,  2017 2016 2015 2017 2016 2015   Assumptions Used to Determine Benefit Obligations at Period End:  Discount rate 3.54% 4.05% 4.30% 3.73% 4.35% 4.60%  Rate of compensation increase 4.46% 3.33% 3.29% - - - 
Schedule Of Changes In Projected Benefit Obligations And Changes In Fair Value Of Plan Assets And Net Funded Status	  Pension Plans OPEB Plan  Year Ended December 31, Year Ended December 31,  2017 2016 2017 2016   Change in Projected Benefit Obligation:  Projected benefit obligation at beginning of year $ 3,307 $ 3,201 $ 1,116 $ 1,088  Service cost 24 23 7 7  Interest cost 131 134 47 49  Participant contributions - - 19 17  Assumption of liabilities - - - 7  Plan amendments - - (78) -  Actuarial (gain) loss 201 106 154 10  Benefits paid (163) (157) (67) (62)  Projected benefit obligation at end of year $ 3,500 $ 3,307 $ 1,198 $ 1,116  Accumulated benefit obligation at end of year $ 3,387 $ 3,213 $ - $ -   Change in Plan Assets:  Fair value of assets at beginning of year $ 2,287 $ 2,252 $ 143 $ 141  Actual return (loss) on assets 327 188 23 9  Employer contributions 149 4 31 31  Assets related to assumed liabilities - - - 7  Participant contributions - - 19 17  Benefits paid (163) (157) (67) (62)  Fair value of assets at end of year $ 2,600 $ 2,287 $ 149 $ 143   Funded Status:  Projected benefit obligation at end of year $ (3,500) $ (3,307) $ (1,198) $ (1,116)  Fair value of assets at end of year 2,600 2,287 149 143  Funded status at end of year $ (900) $ (1,020) $ (1,049) $ (973) 
Schedule Of Amounts Recognized In Balance Sheet	  Pension Plans OPEB Plan  Year Ended December 31, Year Ended December 31,  2017 2016 2017 2016   Amounts Recognized in the Balance Sheet Consist of:  Liabilities:  Other current liabilities $ (4) $ (4) $ (12) $ -  Other noncurrent liabilities (896) (1,016) (1,037) (973)  Net liability recognized $ (900) $ (1,020) $ (1,049) $ (973)  Regulatory assets:  Net loss $ 538 $ 583 $ 402 $ 296  Prior service cost (credit) - - (86) (30)  Net regulatory asset recognized $ 538 $ 583 $ 316 $ 266  Accumulated other comprehensive net loss $ 124 $ 136 $ 3 $ 4 
Schedule Of Projected Benefit Obligations And Accumulated Benefit Obligations In Excess Of Plan Assets Fair Value	  At December 31,  2017 2016   Pension Plan with PBO and ABO in Excess of Plan Assets:  Projected benefit obligations $ 3,316 $ 3,137  Accumulated benefit obligations 3,207 3,051  Plan assets 2,409 2,112 
Schedule Of Target Asset Allocation Ranges By Asset Category	  Target Allocation Ranges  Asset Category Recoverable Non-recoverable   International equities 13% - 21% 5% - 9%  U.S. equities 16% - 24% 6% - 10%  Real estate 3% - 6% -  Credit strategies 5% - 9% 4% - 6%  Fixed income 45% - 57% 76% - 84% 
Schedule Of Expected Long-Term Rate Of Return On Assets Assumptions	  Pension Plans OPEB Plan  Asset Class Expected Long-Term Rate of Return Asset Class Expected Long-Term Rate of Return   International equity securities 7.33% 401(h) accounts 6.51%  U.S. equity securities 6.40% Life insurance VEBA 6.13%  Real estate 5.60% Union VEBA 6.13%  Credit strategies 5.03% Non-union VEBA 2.60%  Fixed income securities 4.20% Weighted average 6.20%  Weighted average (a) 5.48% _____________ (a) The 2018 expected long-term rate of return for the nonregulated portion of the Oncor Retirement Plan is 4.36% and 4.78% for Oncor's portion of the Vistra Retirement Plan. 
Schedule Of Contributions	  Year Ended December 31,  2017 2016 2015   Pension plans contributions $ 149 $ 4 $ 54  OPEB plan contributions 31 31 25  Total contributions $ 180 $ 35 $ 79 
Schedule Of Estimated Future Benefit Payments	  2018 2019 2020 2021 2022 2023-27   Pension plans $ 186 $ 187 $ 192 $ 197 $ 200 $ 1,050  OPEB plan $ 56 $ 59 $ 62 $ 65 $ 68 $ 351 
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Schedule Of Assets Fair Value Measured On Recurring Basis	  At December 31, 2017  Level 1 Level 2 Level 3 Total   Asset Category  Interest-bearing cash $ - $ 11 $ - $ 11  Equity securities:  U.S. 235 2 - 237  International 271 - - 271  Fixed income securities:  Corporate bonds (a) - 1,081 - 1,081  U.S. Treasuries - 251 - 251  Other (b) - 44 - 44  Real estate - - 3 3  Total assets in the fair value hierarchy $ 506 $ 1,389 $ 3 1,898  Total assets measured at net asset value (c) 702  Total fair value of plan assets $ 2,600   At December 31, 2016  Level 1 Level 2 Level 3 Total   Asset Category  Interest-bearing cash $ - $ 14 $ - $ 14  Equity securities:  U.S. 193 3 - 196  International 225 - - 225  Fixed income securities:  Corporate bonds (a) - 1,089 - 1,089  U.S. Treasuries - 223 - 223  Other (b) - 40 - 40  Real estate - - 5 5  Total assets in the fair value hierarchy $ 418 $ 1,369 $ 5 $ 1,792  Total assets measured at net asset value (c) 495  Total fair value of plan assets $ 2,287 _____________ (a) Substantially all corporate bonds are rated investment grade by a major ratings agency such as Moody’s. (b) Other consists primarily of municipal bonds, emerging market debt, bank loans and fixed income derivative instruments. (c) Fair value was measured using the net asset value (NAV) per share as a practical expedient as the investments did not have a readily determinable fair value and are not required to be classified in the fair value hierarchy. The NAV fair value amounts presented here are intended to permit a reconciliation to the total fair value of plan assets.
OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Schedule Of Assets Fair Value Measured On Recurring Basis	  At December 31, 2017  Level 1 Level 2 Level 3 Total   Asset Category  Interest-bearing cash $ 1 $ 1 $ - $ 2  Equity securities:  U.S. 35 - - 35  International 33 - - 33  Fixed income securities:  Corporate bonds (a) - 30 - 30  U.S. Treasuries - 3 - 3  Other (b) 28 1 - 29  Total assets in the fair value hierarchy $ 97 $ 35 $ - 132  Total assets measured at net asset value (c) 17  Total fair value of plan assets $ 149   At December 31, 2016  Level 1 Level 2 Level 3 Total   Asset Category  Interest-bearing cash $ 2 $ - $ - $ 2  Equity securities:  U.S. 41 - - 41  International 28 - - 28  Fixed income securities:  Corporate bonds (a) - 28 - 28  U.S. Treasuries - 2 - 2  Other (b) 28 - - 28  Total assets in the fair value hierarchy $ 99 $ 30 $ - 129  Total assets measured at net asset value (c) 14  Total fair value of plan assets $ 143 _____________ (a) Substantially all corporate bonds are rated investment grade by a major ratings agency such as Moody’s. (b) Other consists primarily of diversified bond mutual funds. (c) Fair value was measured using the net asset value (NAV) per share as a practical expedient as the investments did not have a readily determinable fair value and are not required to be classified in the fair value hierarchy. The NAV fair value amounts presented here are intended to permit a reconciliation to the total fair value of plan assets.
Postretirement Health Coverage [Member]
Defined Benefit Plan Disclosure [Line Items]
Schedule Of Assumptions Used	  Year Ended December 31,  2017 2016   Assumed Health Care Cost Trend Rates – Not Medicare Eligible:  Health care cost trend rate assumed for next year (a) 8.00% 5.80%  Rate to which the cost trend is expected to decline (the ultimate trend rate) 4.50% 5.00%  Year that the rate reaches the ultimate trend rate 2026 2024   Assumed Health Care Cost Trend Rates – Medicare Eligible:  Health care cost trend rate assumed for next year (b) 9.40% 5.70%  Rate to which the cost trend is expected to decline (the ultimate trend rate) 4.50% 5.00%  Year that the rate reaches the ultimate trend rate 2026 2024   (a) 2017 trend rates include weighting for prescription drugs. Comparable rate for 2016 is 6.80%.  (b) 2017 trend rates include weighting for prescription drugs. Comparable rate for 2016 is 8.40%.  1-Percentage Point Increase 1-Percentage Point Decrease   Sensitivity Analysis of Assumed Health Care Cost Trend Rates:  Effect on accumulated postretirement obligation $ 158 $ (131)  Effect on postretirement benefits cost 8 (6) 

Related-Party Transactions (Tab

Related-Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2017
Related-Party Transactions [Abstract]
Schedule Of Related Party Transactions	Amounts payable to (receivable from) members related to income taxes under the agreement and reported on our balance sheet consisted of the following:    At December 31, 2017 At December 31, 2016  EFH Corp. Texas Transmission Total EFH Corp. Texas Transmission Total   Federal income taxes receivable $ (21) $ (5) $ (26) $ (62) $ (18) $ (80)  Texas margin taxes payable 21 - 21 20 - 20  Net payable (receivable) $ - $ (5) $ (5) $ (42) $ (18) $ (60)  Cash payments made to (received from) members related to income taxes consisted of the following:   Year Ended December 31, 2017 Year Ended December 31, 2016 Year Ended December 31, 2015  EFH Corp. Texas Transm. Total EFH Corp. Texas Transm. Total EFH Corp. Texas Transm. Total   Federal income taxes $ (102) $ (12) $ (114) $ - $ - $ - $ 108 $ 27 $ 135  Texas margin taxes 20 - 20 20 - 20 24 - 24  Total payments (receipts) $ (82) $ (12) $ (94) $ 20 $ - $ 20 $ 132 $ 27 $ 159 

Supplementary Financial Infor32

Supplementary Financial Information (Tables)	12 Months Ended
	Dec. 31, 2017
Supplementary Financial Information [Abstract]
Schedule Of Other Income And (Deductions)	Other Income and Deductions  Year Ended December 31,  2017 2016 2015   Accretion of fair value adjustment (discount) to regulatory assets due to acquisition accounting $ - $ 1 $ 5  Professional fees (15) (15) (19)  Non-recoverable pension and OPEB (Note 9) (5) (2) (9)  Interest income 6 2 -  Other (1) (1) 1  Total other income and (deductions) - net $ (15) $ (15) $ (22) 
Schedule Of Interest Expense And Related Charges	  Year Ended December 31,  2017 2016 2015   Interest $ 351 $ 341 $ 335  Amortization of debt issuance costs and discounts 3 3 3  Less allowance for funds used during construction – capitalized interest portion (12) (8) (5)  Total interest expense and related charges $ 342 $ 336 $ 333 
Schedule Of Trade Accounts And Other Receivables	  At December 31,  2017 2016   Gross trade accounts and other receivables $ 638 $ 548  Allowance for uncollectible accounts (3) (3)  Trade accounts receivable – net $ 635 $ 545 
Summary of Investments And Other Property	  At December 31,  2017 2016   Assets related to employee benefit plans, including employee savings programs $ 111 $ 98  Land 2 2  Total investments and other property $ 113 $ 100 
Schedule Of Property, Plant And Equipment	  Composite Depreciation Rate/ At December 31,  Avg. Life at December 31, 2017 2017 2016  Assets in service:  Distribution 2.9% / 34.3 years $ 12,467 $ 11,369  Transmission 2.9% / 34.7 years 7,870 7,734  Other assets 7.1% / 14.1 years 1,380 1,131  Total 21,717 20,234  Less accumulated depreciation 7,255 6,836  Net of accumulated depreciation 14,462 13,398  Construction work in progress 402 416  Held for future use 15 15  Property, plant and equipment – net $ 14,879 $ 13,829 
Schedule Of Intangible Assets	  At December 31, 2017 At December 31, 2016  Gross Gross  Carrying Accumulated Carrying Accumulated  Amount Amortization Net Amount Amortization Net  Identifiable intangible assets subject to amortization:  Land easements $ 453 $ 96 $ 357 $ 491 $ 94 $ 397  Capitalized software 679 339 340 470 326 144  Total $ 1,132 $ 435 $ 697 $ 961 $ 420 $ 541 
Schedule Of Estimated Aggregate Amortization Expenses	  Year Amortization Expense   2018 $ 47  2019 44  2020 43  2021 43  2022 43 
Schedule Of Employee Benefit Obligations And Other	  At December 31,  2017 2016   Retirement plans and other employee benefits $ 2,035 $ 2,092  Uncertain tax positions (including accrued interest) - 3  Investment tax credits 10 12  Other 57 61  Total employee benefit obligations and other $ 2,102 $ 2,168 
Schedule Of Supplemental Cash Flow Information	  Year Ended December 31,  2017 2016 2015  Cash payments related to:   Interest $ 345 $ 336 $ 346  Less capitalized interest (12) (8) (5)  Interest payments (net of amounts capitalized) $ 333 $ 328 $ 341   Amount in lieu of income taxes:  Federal $ (114) $ - $ 135  State 20 20 43  Total payments (refunds) in lieu of income taxes $ (94) $ 20 $ 178   Noncash Sharyland Asset Exchange costs $ 383 $ - $ -  Noncash construction expenditures (a) $ 129 $ 122 $ 56 ______________ (a) Represents end-of-period accruals.
Schedule Of Quarterly Information	  2017 First Quarter Second Quarter Third Quarter Fourth Quarter  Operating revenues $ 935 $ 964 $ 1,068 $ 991  Operating income 160 197 247 184  Net income 73 112 157 77   2016 First Quarter Second Quarter Third Quarter Fourth Quarter  Operating revenues $ 943 $ 948 $ 1,071 $ 958  Operating income 169 196 250 162  Net income 81 110 163 77 

Description Of Business and S33

Description Of Business and Significant Accounting Policies (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)entity	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2004USD ($)	Dec. 31, 2003USD ($)
Business And Significant Accounting Polices [Line Items]
Number of entities that would possibly be bankrupt | entity	1
Long-lived assets and goodwill impairments	$ 0	$ 0	$ 0
Accounting Standards Update 2014-09 [Member]
Business And Significant Accounting Polices [Line Items]
Alternative revenue program	$ 20
Oncor Holdings [Member]
Business And Significant Accounting Polices [Line Items]
Ownership	80.03%
Texas Transmission [Member]
Business And Significant Accounting Polices [Line Items]
Percentage of membership interest owned by non-controlling owners	19.75%
Bondco [Member]
Business And Significant Accounting Polices [Line Items]
Principal amount of transition bonds issued				$ 1,300	$ 1,300
Sales [Member] | TCEH [Member]
Business And Significant Accounting Polices [Line Items]
Concentration risk percentage	22.00%	23.00%	25.00%
Sales [Member] | Vistra [Member]
Business And Significant Accounting Polices [Line Items]
Concentration risk percentage	22.00%	23.00%	25.00%

EFH Bankruptcy Proceedings (Nar

EFH Bankruptcy Proceedings (Narrative) (Details) - USD ($) $ in Millions	Nov. 27, 2017	Aug. 15, 2017	Jul. 28, 2017	Oct. 30, 2016	Dec. 31, 2017	Jul. 07, 2017
Bankruptcy [Line Items]
Assumed debt to equity ratio, debt	57.50%				60.00%
Assumed debt to equity ratio, equity	42.50%				40.00%
Regulatory capitalization ratio, debt					59.40%
Regulatory capitalization ratio, equity					40.60%
Sempra Energy [Member]
Bankruptcy [Line Items]
Percent increase or decrease for disinterested directors to approve any budget					10.00%
Minimum aggregate capital expenditures					$ 7,500
Transaction or transition costs					$ 0
Membership interests owned					51.00%
Required time for holding owndership interests					5 years
Percent of savings for bill credits					90.00%
Period of bill credits					1 year
EFH Corp [Member] | Berkshire Hathaway Energy Company (BHE) [Member]
Bankruptcy [Line Items]
Membership interests owned						80.03%
EFH Corp [Member] | Sempra Energy [Member]
Bankruptcy [Line Items]
Percent of outstanding equity interests required		80.03%
Texas Holdings Group [Member]
Bankruptcy [Line Items]
Amount receivable from related party					$ 129
Texas Holdings Group [Member] | NEE Merger Agreement [Member]
Bankruptcy [Line Items]
Percent of outstanding equity interests required			19.75%
Texas Holdings Group [Member] | TTI Merger Agreement [Member]
Bankruptcy [Line Items]
Percent of outstanding equity interests required				19.75%
Purchase price				$ 2,400

Regulatory Matters (Narrative)

Regulatory Matters (Narrative) (Details) $ in Millions	Nov. 27, 2017USD ($)	Nov. 09, 2017USD ($)miitem	Dec. 31, 2017USD ($)
Public Utilities, General Disclosures [Line Items]
Requested base rate revenue before intercompany eliminations	$ 65
Authorized return on equity	9.80%		10.25%
Authorized regulatory capital structure, debt	57.50%		60.00%
Authorized regulatory capital structure, equity	42.50%		40.00%
Cash paid			$ 25
Sharyland Merger Agreement [Member]
Public Utilities, General Disclosures [Line Items]
Transmission of assets		$ 383
Number of assets transferred in circuit miles | mi		517
Number of transmission lines transferred | item		345
Cash paid		$ 25
Purchase price		$ 408

Provision In Lieu Of Income T36

Provision In Lieu Of Income Taxes (Narrative) (Details) - USD ($) $ in Millions	Dec. 22, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
U.S. federal statutory rate			35.00%	35.00%	35.00%
Re-measurement of liability in lieu of deferred income taxes	$ 1,600		$ 21
Increase (decrease) in liability for deferred income taxes	$ 3
Net liability in lieu of deferred income taxes			1,517	$ 2,788
Uncertain tax positions related to timing of recognition				3	$ 3
Accrued interest			0	0
Benefit (expense) from interest and penalties			$ 0	$ 0	$ 0
Scenario, Plan [Member]
Related Party Transaction [Line Items]
U.S. federal statutory rate		21.00%

Provision In Liew Of Income Tax

Provision In Liew Of Income Taxes (Schedule Of Components Of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Provision In Lieu Of Income Taxes [Abstract]
Deferred tax assets, Employee benefit liabilities	$ 253	$ 413
Deferred tax assets, Regulatory liabilities	15	26
Deferred tax assets, Other	7	79
Total	275	518
Deferred tax liabilities, Property, plant and equipment	1,551	2,892
Deferred tax liabilities, Regulatory assets	240	412
Deferred Tax Liabilities, Other	1	2
Total	1,792	3,306
Liability in lieu of deferred income taxes - net	$ 1,517	$ 2,788

Provision In Lieu Of Income T38

Provision In Lieu Of Income Taxes (Components Of Income Tax Provisions (Benefits)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Provision In Lieu Of Income Taxes [Abstract]
Current: U.S. federal	$ (55)	$ 60	$ 189
Current: State	20	20	32
Deferred: U.S. federal	292	181	55
Deferred: State			(13)
Amortization of investment tax credits	(2)	(2)	(3)
Total reported in operating expenses	255	259	260
U.S. federal	(5)	(5)	(7)
Deferred federal	17		(1)
Total reported in other income and deductions	12	(5)	(8)
Total provision in lieu of income taxes	$ 267	$ 254	$ 252

Provision In Lieu Of Income T39

Provision In Lieu Of Income Taxes (Schedule Of Income Tax Reconciliation) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income before provision in lieu of income taxes		$ 686	$ 685	$ 684
Provision in lieu of income taxes at the U.S. federal statutory rate of 35%		240	240	239
Amortization of investment tax credits - net of deferred tax effect		(2)	(2)	(3)
Amortization (under regulatory accounting) of statutory tax rate changes		(1)	(1)	(1)
Impact of federal statutory rate change 35% to 21%		21
Texas margin tax, net of federal tax benefit		13	13	13
Nontaxable gains on benefit plan investments		(4)
Other, including audit settlements			4	4
Total provision in lieu of income taxes		$ 267	$ 254	$ 252
Effective rate		38.90%	37.10%	36.80%
U.S. federal statutory rate		35.00%	35.00%	35.00%
Scenario, Plan [Member]
U.S. federal statutory rate	21.00%

Provision In Lieu Of Income T40

Provision In Lieu Of Income Taxes (Schedule Of Changes To Uncertain Tax Positions) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Provision In Lieu Of Income Taxes [Abstract]
Balance at January 1, excluding interest and penalties	$ 3	$ 3	$ 2
Additions based on tax positions related to prior years
Reductions based on tax positions related to prior years	(3)
Settlements with taxing authorities, increase			1
Balance at December 31, excluding interest and penalties		$ 3	$ 3

Regulatory Assets And Liabili41

Regulatory Assets And Liabilities (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)$ / mo	Dec. 31, 2016USD ($)
Regulatory Assets And Liabilities [Line Items]
Expected surcharge | $	$ 1,023
Recovery period	11 years
Net regulatory asset | $	$ (627)	$ 1,118
Residential Retail Customer [Member]
Regulatory Assets And Liabilities [Line Items]
Cost recovery factor	2.19
Minimum [Member] | Non-Residential Retail Customer [Member]
Regulatory Assets And Liabilities [Line Items]
Cost recovery factor	2.39
Maximum [Member] | Non-Residential Retail Customer [Member]
Regulatory Assets And Liabilities [Line Items]
Cost recovery factor	5.15
Deferred AMS Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Recovery period	10 years

Regulatory Assets And Liabili42

Regulatory Assets And Liabilities (Components Of Regulatory Assets And Liabilities) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Regulatory Assets And Liabilities [Line Items]
Carrying Amount, Regulatory Assets		$ 2,180	$ 1,974
Carrying Amount, Regulatory Liabilities		2,807	856
Net regulatory asset		$ (627)	1,118
Estimated Net Removal Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Remaining Rate Recovery/Amortization Period		Lives of related assets
Carrying Amount, Regulatory Liabilities		$ 954	819
Protected Excess Deferred Taxes And Investment Tax Credit [Member]
Regulatory Assets And Liabilities [Line Items]
Remaining Rate Recovery/Amortization Period		Various
Carrying Amount, Regulatory Liabilities		$ 1,595	3
Unprotected Excess Deferred Taxes [Member]
Regulatory Assets And Liabilities [Line Items]
Remaining Rate Recovery/Amortization Period		Various
Carrying Amount, Regulatory Liabilities		$ 194
Over-Recovered Wholesale Transmission Service Expense [Member]
Regulatory Assets And Liabilities [Line Items]
Remaining Rate Recovery/Amortization Period	[1]	1 year or less
Carrying Amount, Regulatory Liabilities	[1]	$ 47	10
Other Regulatory Liabilities [Member]
Regulatory Assets And Liabilities [Line Items]
Remaining Rate Recovery/Amortization Period		Various
Carrying Amount, Regulatory Liabilities		$ 17	24
Employee Retirement Costs Being Amortized [Member]
Regulatory Assets And Liabilities [Line Items]
Remaining Rate Recovery/Amortization Period		10 years
Carrying Amount, Regulatory Assets		$ 331	23
Unrecovered Employee Retirement Costs Incurred Since The Last Rate Review Period [Member]
Regulatory Assets And Liabilities [Line Items]
Remaining Rate Recovery/Amortization Period	[2]	To be determined
Carrying Amount, Regulatory Assets	[2]	$ 30	327
Employee Retirement Liability [Member]
Regulatory Assets And Liabilities [Line Items]
Remaining Rate Recovery/Amortization Period	[1],[2],[3]	To be determined
Carrying Amount, Regulatory Assets	[1],[2],[3]	$ 854	849
Self-Insurance Reserve (Primarily Storm Recovery Costs) Being Amortized [Member]
Regulatory Assets And Liabilities [Line Items]
Remaining Rate Recovery/Amortization Period		10 years
Carrying Amount, Regulatory Assets		$ 394	64
Unrecovered Self-Insurance Reserve Incurred Since The Last Rate Review Period [Member]
Regulatory Assets And Liabilities [Line Items]
Remaining Rate Recovery/Amortization Period	[2]	To be determined
Carrying Amount, Regulatory Assets	[2]	$ 49	367
Securities Reacquisition Costs (Post-Industry Restructure) [Member]
Regulatory Assets And Liabilities [Line Items]
Remaining Rate Recovery/Amortization Period		Lives of related debt
Carrying Amount, Regulatory Assets		$ 12	13
Deferred Conventional Meter And Metering Facilities Depreciation [Member]
Regulatory Assets And Liabilities [Line Items]
Remaining Rate Recovery/Amortization Period		3 years
Carrying Amount, Regulatory Assets		$ 57	78
Under-recovered AMS Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Remaining Rate Recovery/Amortization Period		10 years
Carrying Amount, Regulatory Assets		$ 206	209
Unprotected Excess Deferred Taxes [Member]
Regulatory Assets And Liabilities [Line Items]
Carrying Amount, Regulatory Assets		$ 197
Energy Efficiency Performance Bonus [Member]
Regulatory Assets And Liabilities [Line Items]
Remaining Rate Recovery/Amortization Period	[1]	1 year or less
Carrying Amount, Regulatory Assets	[1]	$ 12	10
Other Regulatory Assets [Member]
Regulatory Assets And Liabilities [Line Items]
Remaining Rate Recovery/Amortization Period		Various
Carrying Amount, Regulatory Assets		$ 38	$ 34
[1]	Not earning a return in the regulatory rate-setting process.
[2]	Recovery is specifically authorized by statute or by the PUCT, subject to reasonableness review.
[3]	Represents unfunded liabilities recorded in accordance with pension and OPEB accounting standards.

Short-Term Borrowings (Narrativ

Short-Term Borrowings (Narrative) (Details) $ in Millions	1 Months Ended	12 Months Ended
	Nov. 30, 2017USD ($)item	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Line of Credit Facility [Line Items]
Outstanding borrowing under the revolving credit facility		$ 950	$ 789
Outstanding borrowing, interest rate		2.62%	1.72%
Letters of credit		$ 9	$ 7
Commitment fee		0.125%
Borrowing capacity available under the credit facility		$ 1,041	$ 1,204
Maximum [Member]
Line of Credit Facility [Line Items]
Commitment fee		0.225%
Minimum [Member]
Line of Credit Facility [Line Items]
Commitment fee		0.075%
Letter of Credit [Member]
Line of Credit Facility [Line Items]
Outstanding borrowing, interest rate		1.325%
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 2,000
Number of revolving credit facilities extension options | item	2
Extension period for revolving line of credit	1 year
Expiration of revolving credit facility	Nov. 1, 2022
Revolving Credit Facility [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Additional increase in borrowing capacity amount	$ 100
Debt-to-capitalization ratio		1
Revolving Credit Facility [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Additional increase in borrowing capacity amount	$ 400
Debt-to-capitalization ratio		0.65
London Interbank Offered Rate (LIBOR) [Member]
Line of Credit Facility [Line Items]
Spread over variable rate		1.125%
London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Spread over variable rate		1.50%
London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Spread over variable rate		0.875%
Federal Funds Effective Rate [Member]
Line of Credit Facility [Line Items]
Spread over variable rate		0.50%
One-Month London Interbank Offered Rate [Member]
Line of Credit Facility [Line Items]
Spread over variable rate		1.00%
One-Month London Interbank Offered Rate [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Spread over variable rate		0.50%
One-Month London Interbank Offered Rate [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Spread over variable rate		0.00%

Long-Term Debt (Narrative) (Det

Long-Term Debt (Narrative) (Details) - USD ($)	1 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Aug. 31, 2016	Mar. 31, 2015
Long-Term Debt [Line Items]
Repayments of long-term debt		$ 324,000,000	$ 41,000,000	$ 639,000,000
Aggregate principal amount		$ 5,876,000,000	5,875,000,000
Percentage of fair value of cost of property additions certified to the Deed of Trust collateral agent		85.00%
Available bond credits		$ 3,038,000,000
Future debt subject to property additions to the Deed of Trust		2,458,000,000
Estimated fair value of our long-term debt including current maturities		$ 7,153,000,000	6,751,000,000
London Interbank Offered Rate (LIBOR) [Member]
Long-Term Debt [Line Items]
Spread over variable rate		1.125%
Federal Funds Effective Rate [Member]
Long-Term Debt [Line Items]
Spread over variable rate		0.50%
One-Month London Interbank Offered Rate [Member]
Long-Term Debt [Line Items]
Spread over variable rate		1.00%
5.000% Fixed Senior Notes Due September 30, 2017 [Member]
Long-Term Debt [Line Items]
Repayments of long-term debt		$ 324,000,000
Due date		Sep. 30, 2017
Aggregate principal amount			$ 324,000,000
Interest percentage		5.00%	5.00%
3.800% Fixed Senior Notes Due September 30, 2047 [Member]
Long-Term Debt [Line Items]
Due date		Sep. 30, 2047
Aggregate principal amount		$ 325,000,000
Interest percentage		3.80%	3.80%
Proceeds from sale of Notes	$ 321,000,000
Percentage of principal amount plus accrued and unpaid interest and make-whole premium		100.00%
Number of days after issuance date for exchange offer completion		315 days
Number of days after shelf registration filing obligation for filing to be effective		270 days
Increase in basis points per annum		0.50%
Term Loan Credit Agreement Due No Later Than March 26, 2019 [Member]
Long-Term Debt [Line Items]
Due date		Mar. 26, 2019
Interest percentage		2.452%
Term loan		$ 275,000,000
Loan term		18 months
Senior debt to capitalization ratio		0.65
Excess of principal amount for default		$ 100,000,000
Judgment for payment of money on term loan		$ 50,000,000
Time alloted for excess debt default to be discharged		60 days
Term Loan Credit Agreement Due No Later Than March 26, 2019 [Member] | London Interbank Offered Rate (LIBOR) [Member]
Long-Term Debt [Line Items]
Spread over variable rate		0.90%
Term Loan Credit Agreement Due No Later Than March 26, 2019 [Member] | Federal Funds Effective Rate [Member]
Long-Term Debt [Line Items]
Spread over variable rate		0.50%
Term Loan Credit Agreement Due No Later Than March 26, 2019 [Member] | One-Month London Interbank Offered Rate [Member]
Long-Term Debt [Line Items]
Spread over variable rate		1.00%
3.750% Fixed Senior Notes Due April 1, 2045 [Member]
Long-Term Debt [Line Items]
Due date		Apr. 1, 2045
Aggregate principal amount		$ 550,000,000	$ 550,000,000
Interest percentage		3.75%	3.75%
6.800% Fixed Senior Notes Due September 1, 2018 [Member]
Long-Term Debt [Line Items]
Due date		Sep. 1, 2018
Aggregate principal amount		$ 550,000,000	$ 550,000,000
Interest percentage		6.80%	6.80%
Additional 2045 Notes [Member]
Long-Term Debt [Line Items]
Due date		Oct. 1, 2044
Debt principal amount					$ 175,000,000	$ 375,000,000
Proceeds from sale of Notes		$ 185,000,000
Percentage of principal amount plus accrued and unpaid interest and make-whole premium		100.00%
Transition Bond [Member]
Long-Term Debt [Line Items]
Repayments of long-term debt		$ 41,000,000
Minimum [Member] | London Interbank Offered Rate (LIBOR) [Member]
Long-Term Debt [Line Items]
Spread over variable rate		0.875%
Minimum [Member] | One-Month London Interbank Offered Rate [Member]
Long-Term Debt [Line Items]
Spread over variable rate		0.00%
Maximum [Member] | London Interbank Offered Rate (LIBOR) [Member]
Long-Term Debt [Line Items]
Spread over variable rate		1.50%
Maximum [Member] | One-Month London Interbank Offered Rate [Member]
Long-Term Debt [Line Items]
Spread over variable rate		0.50%

Long-Term Debt (Schedule Of Lon

Long-Term Debt (Schedule Of Long-Term Debt) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Secured long-term debt	$ 5,876	$ 5,875
Total long-term debt	6,151	5,875
Unamortized discount and debt issuance costs	(34)	(36)
Less amount due currently	(550)	(324)
Long-term debt, less amounts due currently	$ 5,567	5,515
5.000% Fixed Senior Notes Due September 30, 2017 [Member]
Debt Instrument [Line Items]
Secured long-term debt		$ 324
Interest percentage	5.00%	5.00%
Due date	Sep. 30, 2017
6.800% Fixed Senior Notes Due September 1, 2018 [Member]
Debt Instrument [Line Items]
Secured long-term debt	$ 550	$ 550
Interest percentage	6.80%	6.80%
Due date	Sep. 1, 2018
2.150% Fixed Senior Notes Due June 1, 2019 [Member]
Debt Instrument [Line Items]
Secured long-term debt	$ 250	$ 250
Interest percentage	2.15%	2.15%
Due date	Jun. 1, 2019
5.750% Fixed Senior Notes Due September 30, 2020 [Member]
Debt Instrument [Line Items]
Secured long-term debt	$ 126	$ 126
Interest percentage	5.75%	5.75%
Due date	Sep. 30, 2020
4.100% Fixed Senior Notes Due June 1, 2022 [Member]
Debt Instrument [Line Items]
Secured long-term debt	$ 400	$ 400
Interest percentage	4.10%	4.10%
Due date	Jun. 1, 2022
7.000% Fixed Debentures Due September 1, 2022 [Member]
Debt Instrument [Line Items]
Secured long-term debt	$ 800	$ 800
Interest percentage	7.00%	7.00%
Due date	Sep. 1, 2022
2.950% Fixed Senior Notes Due April 1, 2025 [Member]
Debt Instrument [Line Items]
Secured long-term debt	$ 350	$ 350
Interest percentage	2.95%	2.95%
Due date	Apr. 1, 2025
7.000% Fixed Senior Notes Due May 1, 2032 [Member]
Debt Instrument [Line Items]
Secured long-term debt	$ 500	$ 500
Interest percentage	7.00%	7.00%
Due date	May 1, 2032
7.250% Fixed Senior Notes Due January 15, 2033 [Member]
Debt Instrument [Line Items]
Secured long-term debt	$ 350	$ 350
Interest percentage	7.25%	7.25%
Due date	Jan. 15, 2033
7.500% Fixed Senior Notes Due September 1, 2038 [Member]
Debt Instrument [Line Items]
Secured long-term debt	$ 300	$ 300
Interest percentage	7.50%	7.50%
Due date	Sep. 1, 2038
5.250% Fixed Senior Notes Due September 30, 2040 [Member]
Debt Instrument [Line Items]
Secured long-term debt	$ 475	$ 475
Interest percentage	5.25%	5.25%
Due date	Sep. 30, 2040
4.550% Fixed Senior Notes Due December 1, 2041 [Member]
Debt Instrument [Line Items]
Secured long-term debt	$ 400	$ 400
Interest percentage	4.55%	4.55%
Due date	Dec. 1, 2041
5.300% Fixed Senior Notes Due June 1, 2042 [Member]
Debt Instrument [Line Items]
Secured long-term debt	$ 500	$ 500
Interest percentage	5.30%	5.30%
Due date	Jun. 1, 2042
3.750% Fixed Senior Notes Due April 1, 2045 [Member]
Debt Instrument [Line Items]
Secured long-term debt	$ 550	$ 550
Interest percentage	3.75%	3.75%
Due date	Apr. 1, 2045
3.800% Fixed Senior Notes Due September 30, 2047 [Member]
Debt Instrument [Line Items]
Secured long-term debt	$ 325
Interest percentage	3.80%	3.80%
Due date	Sep. 30, 2047
Term Loan Credit Agreement Due No Later Than March 26, 2019 [Member]
Debt Instrument [Line Items]
Term loan	$ 275
Interest percentage	2.452%
Due date	Mar. 26, 2019

Long-Term Debt (Schedule Of L46

Long-Term Debt (Schedule Of Long-Term Debt Maturity) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Long-Term Debt [Abstract]
2,018	$ 550
2,019	525
2,020	126
2,022	1,200
Thereafter	3,750
Unamortized discount and debt issuance costs	(34)	$ (36)
Total	$ 6,117

Commitments And Contingencies47

Commitments And Contingencies (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies [Abstract]
Rent expenses	$ 27	$ 9	$ 8
2018 required efficiency spending amount	$ 50
Percentage of full time employees represented by labor union	19.00%
Expiration date of collective bargaining agreement	Oct. 25, 2018

Commitments And Contingencies48

Commitments And Contingencies (Schedule Of Future Miinimum Lease Payments Under Operating Leases) (Details) $ in Millions	Dec. 31, 2017USD ($)
Commitments and Contingencies [Abstract]
2,018	$ 32
2,019	21
2,020	14
2,021	11
2,022	10
Thereafter	1
Total future minimum lease payments	$ 89

Membership Interests (Narrative

Membership Interests (Narrative) (Details) - USD ($) $ in Millions	Nov. 27, 2017	Oct. 25, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Membership Interests [Abstract]
Assumed debt to equity ratio, debt	57.50%		60.00%
Assumed debt to equity ratio, equity	42.50%		40.00%
Regulatory capitalization ratio, debt			59.40%
Regulatory capitalization ratio, equity			40.60%
Cash distribution to members		$ 32	$ 237	$ 230	$ 436
Contingent equity distribution		$ 250

Membership Interests (Schedule

Membership Interests (Schedule Of Distributions Paid) (Details) - USD ($) $ in Millions	Oct. 25, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Dividends Payable [Line Items]
Amount	$ 32	$ 237	$ 230	$ 436
Payment One FY 2017 [Member]
Dividends Payable [Line Items]
Declaration Date		Jul. 26, 2017
Payment Date		Aug. 1, 2017
Amount		$ 65
Payment Two FY 2017 [Member]
Dividends Payable [Line Items]
Declaration Date		Apr. 26, 2017
Payment Date		Apr. 27, 2017
Amount		$ 86
Payment Three FY 2017 [Member]
Dividends Payable [Line Items]
Declaration Date		Mar. 22, 2017
Payment Date		Mar. 24, 2017
Amount		$ 86
Payment One FY 2016 [Member]
Dividends Payable [Line Items]
Declaration Date		Oct. 26, 2016
Payment Date		Oct. 27, 2016
Amount		$ 41
Payment Two FY 2016 [Member]
Dividends Payable [Line Items]
Declaration Date		Jul. 27, 2016
Payment Date		Aug. 11, 2016
Amount		$ 68
Payment Three FY 2016 [Member]
Dividends Payable [Line Items]
Declaration Date		Apr. 27, 2016
Payment Date		May 11, 2016
Amount		$ 65
Payment Four FY 2016 [Member]
Dividends Payable [Line Items]
Declaration Date		Feb. 24, 2016
Payment Date		Feb. 25, 2016
Amount		$ 56

Membership Interests (Schedul51

Membership Interests (Schedule Of Changes To Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	$ (111)	$ (113)	$ (107)
Balance at end of period	(101)	(111)	(113)
Cash Flow Hedges - Interest Rate Swap [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(20)	(22)	(24)
Defined benefit pension plans (net of tax)
Amounts reclassified from accumulated other comprehensive income (loss) and reported in interest expense and related charges	2	2	2
Balance at end of period	(18)	(20)	(22)
Defined Benefit Pension and OPEB Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(91)	(91)	(83)
Defined benefit pension plans (net of tax)	8		(8)
Amounts reclassified from accumulated other comprehensive income (loss) and reported in interest expense and related charges
Balance at end of period	(83)	(91)	(91)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(111)	(113)	(107)
Defined benefit pension plans (net of tax)	8		(8)
Amounts reclassified from accumulated other comprehensive income (loss) and reported in interest expense and related charges	2	2	2
Balance at end of period	$ (101)	$ (111)	$ (113)

Pension And OPEB Plans (Narrati

Pension And OPEB Plans (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)item	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Defined Benefit Plan Disclosure [Line Items]
Regulatory assets		$ 2,180	$ 1,974
Earning period		3 years
Rolling period		4 years
Percentage of gains and losses		25.00%
Second pool representation of total investments, percentage		31.00%
Cash contributions		$ 180	35	$ 79
Vistra [Member]
Defined Benefit Plan Disclosure [Line Items]
Unfunded liability		$ 111
Oncor Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of corporate bonds | item		1,029
Pension And OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Regulatory assets		$ 1,215	1,199
Defined Benefit Pension Plans [Member] | Scenario, Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of net actuarial loss	$ 45
Amortization of prior service cost	0
Defined Benefit Pension Plans [Member] | Scenario, Forecast [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of net actuarial loss	4
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Unfunded liability		(900)	(1,020)
Amortization of net actuarial loss		(45)	(41)	(63)
Expected funding, 2018		82
Expected funding, 2018 to 2022		556
Cash contributions		149	4	54
OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Unfunded liability		$ (1,049)	(973)
Number of corporate bonds | item		391
Amortization of net actuarial loss		$ (32)	(35)	(33)
Amortization of prior service cost		(20)	(20)	(20)
Expected funding, 2018		35
Expected funding, 2018 to 2022		178
Cash contributions		$ 31	31	25
OPEB Plan [Member] | Scenario, Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of net actuarial loss	56
Amortization of prior service cost	30
OPEB Plan [Member] | Scenario, Forecast [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of net actuarial loss	1
Amortization of prior service cost	$ 0
Oncor Cash Balance Formula Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of employee's contribution match by employer		100.00%
Percentage of employee's contribution matched 100% by employer		6.00%
Oncor Traditional Retirement Plan Formula Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of employee's contribution match by employer		75.00%
Percentage of employee's contribution matched 100% by employer		6.00%
Thrift Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Cash contributions		$ 17	$ 15	$ 14

Pension And OPEB Plans (Schedul

Pension And OPEB Plans (Schedule Of Pension And OPEB Plan Costs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Net costs	$ 143	$ 138	$ 157
Less amounts deferred principally as property or a regulatory asset	(98)	(100)	(113)
Net amounts recognized as expense	45	38	44
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net costs	85	76	104
Net amounts recognized as expense	29	76	78
OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net costs	58	62	53
Net amounts recognized as expense	$ 107	$ 57	$ 79

Pension And OPEB Plans (Sched54

Pension And OPEB Plans (Schedule Of Detailed Pension And OPEB Benefit Information) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Components of net OPEB costs:
Net costs	$ 143	$ 138	$ 157
Other Changes in Plan Assets and Benefit Obligations Recognized as Regulatory Assets or in Other Comprehensive Income:
Net amounts recognized as expense	$ 45	$ 38	$ 44
Pension Plan [Member]
Assumptions Used to Determine Net Periodic Pension and OPEB Costs:
Discount rate	4.05%	4.30%	3.96%
Expected return on plan assets	5.17%	5.54%	5.26%
Rate of compensation increase	3.33%	3.29%	3.29%
Components of net OPEB costs:
Service cost	$ 24	$ 23	$ 25
Interest cost	131	134	131
Expected return on assets	(115)	(122)	(115)
Amortization of net loss	45	41	63
Net costs	85	76	104
Other Changes in Plan Assets and Benefit Obligations Recognized as Regulatory Assets or in Other Comprehensive Income:
Net loss (gain)	(11)	41	37
Amortization of net loss	(45)	(41)	(63)
Plan amendments
Total recognized as regulatory assets or other comprehensive income	(56)		(26)
Net amounts recognized as expense	$ 29	$ 76	$ 78
OPEB Plan [Member]
Assumptions Used to Determine Net Periodic Pension and OPEB Costs:
Discount rate	4.35%	4.60%	4.23%
Expected return on plan assets	6.10%	6.30%	6.65%
Components of net OPEB costs:
Service cost	$ 7	$ 7	$ 7
Interest cost	47	49	43
Expected return on assets	(8)	(9)	(10)
Amortization of prior service cost (credit)	(20)	(20)	(20)
Amortization of net loss	32	35	33
Net costs	58	62	53
Other Changes in Plan Assets and Benefit Obligations Recognized as Regulatory Assets or in Other Comprehensive Income:
Net loss (gain)	139	10	39
Amortization of net loss	(32)	(35)	(33)
Plan amendments	(78)
Amortization of prior service cost (credit)	20	20	20
Total recognized as regulatory assets or other comprehensive income	49	(5)	26
Net amounts recognized as expense	$ 107	$ 57	$ 79

Pension And OPEB Plans (Assumpt

Pension And OPEB Plans (Assumptions Used To Determine Benefit Obligations) (Details)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.54%	4.05%	4.30%
Rate of compensation increase	4.46%	3.33%	3.29%
OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.73%	4.35%	4.60%

Pension And OPEB Plans (Change

Pension And OPEB Plans (Change In Project Benefit Obligations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation at beginning of year	$ 3,307	$ 3,201
Service cost	24	23	$ 25
Interest cost	131	134	131
Participant contributions
Assumption of liabilities
Plan amendments
Actuarial (gain) loss	201	106
Benefits paid	(163)	(157)
Projected benefit obligation at end of year	3,500	3,307	3,201
Accumulated benefit obligation at end of year	3,387	3,213
OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation at beginning of year	1,116	1,088
Service cost	7	7	7
Interest cost	47	49	43
Participant contributions	19	17
Assumption of liabilities		7
Plan amendments	(78)
Actuarial (gain) loss	154	10
Benefits paid	(67)	(62)
Projected benefit obligation at end of year	1,198	1,116	$ 1,088
Accumulated benefit obligation at end of year

Pension And OPEB Plans (Chang57

Pension And OPEB Plans (Change In Plan Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 180	$ 35	$ 79
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets at beginning of year	2,287	2,252
Actual return (loss) on assets	327	188
Employer contributions	149	4	54
Assets related to assumed liabilies
Participant contributions
Benefits paid	(163)	(157)
Fair value of assets at end of year	2,600	2,287	2,252
OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets at beginning of year	143	141
Actual return (loss) on assets	23	9
Employer contributions	31	31	25
Assets related to assumed liabilies		7
Participant contributions	19	17
Benefits paid	(67)	(62)
Fair value of assets at end of year	$ 149	$ 143	$ 141

Pension And OPEB Plans (Funded

Pension And OPEB Plans (Funded Status) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation at end of year	$ (3,500)	$ (3,307)	$ (3,201)
Fair value of assets at end of year	2,600	2,287	2,252
Funded status at end of year	(900)	(1,020)
OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation at end of year	(1,198)	(1,116)	(1,088)
Fair value of assets at end of year	149	143	$ 141
Funded status at end of year	$ (1,049)	$ (973)

Pension And OPEB Plans (Amounts

Pension And OPEB Plans (Amounts Recognized In Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Net regulatory asset recognized	$ 111	$ 98
Accumulated other comprehensive net loss	(101)	(111)	$ (113)	$ (107)
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Other current liabilities	(4)	(4)
Other noncurrent liabilities	(896)	(1,016)
Net liability recognized	(900)	(1,020)
Net loss	538	583
Net regulatory asset recognized	538	583
Accumulated other comprehensive net loss	124	136
OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Other current liabilities	(12)
Other noncurrent liabilities	(1,037)	(973)
Net liability recognized	(1,049)	(973)
Net loss	402	296
Prior service cost (credit)	(86)	(30)
Net regulatory asset recognized	316	266
Accumulated other comprehensive net loss	$ 3	$ 4

Pension And OPEB Plans (Sched60

Pension And OPEB Plans (Schedule Of Assumed Health Care Cost Trend Rates) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Effect on accumulated postretirement obligation, 1-Percentage Point Increase	$ 158
Effect on accumulated postretirement obligation, 1-Percentage Point Decrease		$ (131)
Effect on postretirement benefits cost, 1-Percentage Point Increase	$ 8
Effect on postretirement benefits cost, 1-Percentage Point Decrease		$ (6)
Not Medicare Eligible [Member]
Defined Benefit Plan Disclosure [Line Items]
Health care and prescription drug cost trend rate assumed for next year	8.00%	5.80%
Rate to which the cost trend is expected to decline (the ultimate trend rate)	4.50%	5.00%
Year that the rate reaches the ultimate trend rate	2,026	2,024
Medicare Eligible [Member]
Defined Benefit Plan Disclosure [Line Items]
Health care and prescription drug cost trend rate assumed for next year	9.40%	5.70%
Rate to which the cost trend is expected to decline (the ultimate trend rate)	4.50%	5.00%
Year that the rate reaches the ultimate trend rate	2,026	2,024

Pension And OPEB Plans (Sched61

Pension And OPEB Plans (Schedule Of Projected Benefit Obligations And Accumulated Benefit Obligations In Excess Of Plan Assets Fair Value) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Pension And OPEB Plans [Abstract]
Projected benefit obligations	$ 3,316	$ 3,137
Accumulated benefit obligations	3,207	3,051
Plan assets	$ 2,409	$ 2,112

Pension And OPEB Plans (Sched62

Pension And OPEB Plans (Schedule Of Target Asset Allocation Ranges By Asset Category) (Details)	Dec. 31, 2017
International Equities [Member] | Recoverable [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	13.00%
International Equities [Member] | Recoverable [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	21.00%
International Equities [Member] | Nonrecoverable [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	5.00%
International Equities [Member] | Nonrecoverable [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	9.00%
US Equities [Member] | Recoverable [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	16.00%
US Equities [Member] | Recoverable [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	24.00%
US Equities [Member] | Nonrecoverable [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	6.00%
US Equities [Member] | Nonrecoverable [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	10.00%
Real Estate [Member] | Recoverable [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	3.00%
Real Estate [Member] | Recoverable [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	6.00%
Credit Strategies [Member] | Recoverable [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	5.00%
Credit Strategies [Member] | Recoverable [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	9.00%
Credit Strategies [Member] | Nonrecoverable [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	4.00%
Credit Strategies [Member] | Nonrecoverable [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	6.00%
Fixed Income [Member] | Recoverable [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	45.00%
Fixed Income [Member] | Recoverable [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	57.00%
Fixed Income [Member] | Nonrecoverable [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	76.00%
Fixed Income [Member] | Nonrecoverable [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	84.00%

Pension And OPEB Plans (Sched63

Pension And OPEB Plans (Schedule Of Assets Fair Value Measured On Recurring Basis) (Details) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		$ 1,898	$ 1,792
Total assets measured at net asset value	[1]	702	495
Total fair value of plan assets		2,600	2,287	$ 2,252
OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets measured at net asset value	[1]	17	14
Total fair value of plan assets		149	143	$ 141
OPEB Plan [Member] | Accounting Standards Update 2015-07 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		132	129
US Equities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		237	196
US Equities [Member] | OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		35	41
International Equities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		271	225
International Equities [Member] | OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		33	28
Corporate Bond Securities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy	[2]	1,081	1,089
Corporate Bond Securities [Member] | OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy	[2]	30	28
US Treasury Securities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		251	223
US Treasury Securities [Member] | OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		3	2
Other [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy	[3]	44	40
Other [Member] | OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy	[4]	29	28
Real Estate [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		3	5
Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		506	418
Fair Value, Inputs, Level 1 [Member] | OPEB Plan [Member] | Accounting Standards Update 2015-07 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		97	99
Fair Value, Inputs, Level 1 [Member] | US Equities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		235	193
Fair Value, Inputs, Level 1 [Member] | US Equities [Member] | OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		35	41
Fair Value, Inputs, Level 1 [Member] | International Equities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		271	225
Fair Value, Inputs, Level 1 [Member] | International Equities [Member] | OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		33	28
Fair Value, Inputs, Level 1 [Member] | Other [Member] | OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy	[4]	28	28
Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		1,389	1,369
Fair Value, Inputs, Level 2 [Member] | OPEB Plan [Member] | Accounting Standards Update 2015-07 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		35	30
Fair Value, Inputs, Level 2 [Member] | US Equities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		2	3
Fair Value, Inputs, Level 2 [Member] | Corporate Bond Securities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy	[2]	1,081	1,089
Fair Value, Inputs, Level 2 [Member] | Corporate Bond Securities [Member] | OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy	[2]	30	28
Fair Value, Inputs, Level 2 [Member] | US Treasury Securities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		251	223
Fair Value, Inputs, Level 2 [Member] | US Treasury Securities [Member] | OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		3	2
Fair Value, Inputs, Level 2 [Member] | Other [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy	[3]	44	40
Fair Value, Inputs, Level 2 [Member] | Other [Member] | OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy	[4]	1
Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		3	5
Fair Value, Inputs, Level 3 [Member] | Real Estate [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		3	5
Interest-bearing Cash [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		11	14
Interest-bearing Cash [Member] | OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		2	2
Interest-bearing Cash [Member] | Fair Value, Inputs, Level 1 [Member] | OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		1	2
Interest-bearing Cash [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		11	$ 14
Interest-bearing Cash [Member] | Fair Value, Inputs, Level 2 [Member] | OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in the fair value hierarchy		$ 1
[1]	Fair value was measured using the net asset value (NAV) per share as a practical expedient as the investments did not have a readily determinable fair value and are not required to be classified in the fair value hierarchy. The NAV fair value amounts presented here are intended to permit a reconciliation to the total fair value of plan assets.
[2]	Substantially all corporate bonds are rated investment grade by a major ratings agency such as Moody's.
[3]	Other consists primarily of municipal bonds, emerging market debt, bank loans and fixed income derivative instruments.
[4]	Other consists primarily of diversified bond mutual funds.

Pension And OPEB Plans (Sched64

Pension And OPEB Plans (Schedule Of Expected Long-Term Rate Of Return On Assets Assumptions) (Details)	12 Months Ended
	Dec. 31, 2017
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted average expected long-term rate of return	5.48%	[1]
Pension Plan [Member] | International Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted average expected long-term rate of return	7.33%
Pension Plan [Member] | US Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted average expected long-term rate of return	6.40%
Pension Plan [Member] | Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted average expected long-term rate of return	5.60%
Pension Plan [Member] | Credit Strategies [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted average expected long-term rate of return	5.03%
Pension Plan [Member] | Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted average expected long-term rate of return	4.20%
Pension Plan [Member] | Oncor Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted average expected long-term rate of return	4.36%
OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted average expected long-term rate of return	6.20%
OPEB Plan [Member] | 401(h) Accounts [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted average expected long-term rate of return	6.51%
OPEB Plan [Member] | Life Insurance VEBA [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted average expected long-term rate of return	6.13%
OPEB Plan [Member] | Union VEBA [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted average expected long-term rate of return	6.13%
OPEB Plan [Member] | Non-union VEBA [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted average expected long-term rate of return	2.60%
OPEB Plan [Member] | Vistra Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted average expected long-term rate of return	4.78%
[1]	The 2018 expected long-term rate of return for the nonregulated portion of the Oncor Retirement Plan is 4.36%

Pension And OPEB Plans (Sched65

Pension And OPEB Plans (Schedule Of Contributions) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Total contributions	$ 180	$ 35	$ 79
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total contributions	149	4	54
OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total contributions	$ 31	$ 31	$ 25

Pension And OPEB Plans (Sched66

Pension And OPEB Plans (Schedule Of Estimated Future Benefit Payments) (Details) $ in Millions	Dec. 31, 2017USD ($)
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
2,018	$ 186
2,019	187
2,020	192
2,021	197
2,022	200
2023-27	1,050
OPEB Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
2,018	56
2,019	59
2,020	62
2,021	65
2,022	68
2023-27	$ 351

Stock-Based Compensation (Narra

Stock-Based Compensation (Narrative) (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	0
SARs Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend accrual compensation expense	$ 11
SARs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized dividend accretion and interest	$ 1	$ 1	$ 1

Related-Party Transactions (Nar

Related-Party Transactions (Narrative) (Details) - USD ($) $ in Millions	Oct. 02, 2016	Jan. 01, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Revenues from electricity delivery fees				$ 715	$ 955
TCEH [Member]
Related Party Transaction [Line Items]
Revenues from electricity delivery fees	$ 715	$ 715			$ 955
EFH Corp [Member]
Related Party Transaction [Line Items]
Administrative and services costs			$ 1	17
Shared facilities expense			3	4
Shared facilities payments received			$ 1	2
Sponsor Group [Member]
Related Party Transaction [Line Items]
Equity in existing vendor			16.00%
Cash payments to vendors related to Texas margin taxes			$ 219	188
Trade payables related parties			7	5
Sponsor Group [Member] | Capitalized [Member]
Related Party Transaction [Line Items]
Cash payments to vendors related to Texas margin taxes			210	180
Sponsor Group [Member] | Operating And Maintenance Expense [Member]
Related Party Transaction [Line Items]
Cash payments to vendors related to Texas margin taxes			$ 9	$ 8

Related-Party Transactions (Sch

Related-Party Transactions (Schedule Of Related Party Transactions) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Federal income taxes receivable	$ (26)	$ (80)
Texas margin taxes payable	21	20
Net payable (receivable)	(5)	(60)
EFH Corp [Member]
Related Party Transaction [Line Items]
Federal income taxes receivable	(21)	(62)
Texas margin taxes payable	21	20
Net payable (receivable)		(42)
Texas Transmission Investment LLC [Member]
Related Party Transaction [Line Items]
Federal income taxes receivable	(5)	(18)
Net payable (receivable)	$ (5)	$ (18)

Related-Party Transactions (Cas

Related-Party Transactions (Cash Payments Made To (Received From) Members Related To Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Federal income taxes	$ (114)		$ 135
Texas margin taxes	20	$ 20	24
Total payments (receipts)	(94)	20	159
EFH Corp [Member]
Related Party Transaction [Line Items]
Federal income taxes	(102)		108
Texas margin taxes	20	20	24
Total payments (receipts)	(82)	$ 20	132
Texas Transmission Investment LLC [Member]
Related Party Transaction [Line Items]
Federal income taxes	(12)		27
Total payments (receipts)	$ (12)		$ 27

Supplementary Financial Infor71

Supplementary Financial Information (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2004	Dec. 31, 2003
Supplemental Financial Information [Line Items]
Face value of life insurance policies	$ 162	$ 153
Net cash surrender values	$ 84	$ 76
Depreciation expense as percentage of average depreciable property	3.40%	3.50%	3.60%
Aggregate amortization expenses	$ 57	$ 61	$ 64
Goodwill	$ 4,064	4,064
Bondco [Member]
Supplemental Financial Information [Line Items]
Principal amount of transition bonds issued				$ 1,300	$ 1,300
Financial support		$ 0
Sales [Member] | TCEH [Member]
Supplemental Financial Information [Line Items]
Concentration risk percentage	22.00%	23.00%	25.00%
Sales [Member] | Vistra [Member]
Supplemental Financial Information [Line Items]
Concentration risk percentage	22.00%	23.00%	25.00%
Sales [Member] | Nonaffiliated REP [Member]
Supplemental Financial Information [Line Items]
Concentration risk percentage	18.00%	17.00%	17.00%
Trade Accounts Receivable [Member] | Nonaffiliated REP [Member]
Supplemental Financial Information [Line Items]
Concentration risk percentage	12.00%	15.00%
Trade Accounts Receivable [Member] | Second Nonaffiliated REP [Member]
Supplemental Financial Information [Line Items]
Concentration risk percentage	10.00%	12.00%
Land Easements [Member]
Supplemental Financial Information [Line Items]
Weighted average remaining useful life	82 years
Capitalized Software [Member]
Supplemental Financial Information [Line Items]
Weighted average remaining useful life	8 years

Supplementary Financial Infor72

Supplementary Financial Information (Schedule Of Other Income And (Deductions)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplementary Financial Information [Abstract]
Accretion of fair value adjustment (discount) to regulatory assets due to acquisition accounting		$ 1	$ 5
Professional fees	$ (15)	(15)	(19)
Non-recoverable pension and OPEB (Note 9)	(5)	(2)	(9)
Interest income	6	2
Other	(1)	(1)
Other			1
Total other income and (deductions) - net	$ (15)	$ (15)	$ (22)

Supplementary Financial Infor73

Supplementary Financial Information (Schedule Of Interest Expense And Related Charges) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplementary Financial Information [Abstract]
Interest	$ 351	$ 341	$ 335
Amortization of debt issuance costs and discounts	3	3	3
Less allowance for funds used during construction — capitalized interest portion	(12)	(8)	(5)
Total interest expense and related charges	$ 342	$ 336	$ 333

Supplementary Financial Infor74

Supplementary Financial Information (Schedule Of Trade Accounts And Other Receivables) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Supplementary Financial Information [Abstract]
Gross trade accounts and other receivables	$ 638	$ 548
Allowance for uncollectible accounts	(3)	(3)
Trade accounts receivable - net	$ 635	$ 545

Supplementary Financial Infor75

Supplementary Financial Information (Summary of Investments And Other Property) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Supplementary Financial Information [Abstract]
Assets related to employee benefit plans, including employee savings programs	$ 111	$ 98
Land	2	2
Total investments and other property	$ 113	$ 100

Supplementary Financial Infor76

Supplementary Financial Information (Schedule Of Property, Plant And Equipment) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Property Plant and Equipment [Line Items]
Total assets in service	$ 21,717	$ 20,234
Less accumulated depreciation	7,255	6,836
Net of accumulated depreciation	14,462	13,398
Construction work in progress	402	416
Held for future use	15	15
Property, plant and equipment - net	14,879	13,829
Distribution [Member]
Property Plant and Equipment [Line Items]
Total assets in service	$ 12,467	11,369
Composite depreciation rate	2.90%
Avg. life	34 years 3 months 18 days
Transmission [Member]
Property Plant and Equipment [Line Items]
Total assets in service	$ 7,870	7,734
Composite depreciation rate	2.90%
Avg. life	34 years 8 months 12 days
Other Assets [Member]
Property Plant and Equipment [Line Items]
Total assets in service	$ 1,380	$ 1,131
Composite depreciation rate	7.10%
Avg. life	14 years 1 month 6 days

Supplementary Financial Infor77

Supplementary Financial Information (Schedule Of Intangible Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,132	$ 961
Accumulated Amortization	435	420
Net	697	541
Land Easements [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	453	491
Accumulated Amortization	96	94
Net	357	397
Capitalized Software [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	679	470
Accumulated Amortization	339	326
Net	$ 340	$ 144

Supplementary Financial Infor78

Supplementary Financial Information (Schedule Of Estimated Aggregate Amortization Expenses) (Details) $ in Millions	Dec. 31, 2017USD ($)
Supplementary Financial Information [Abstract]
2,018	$ 47
2,019	44
2,020	43
2,021	43
2,022	$ 43

Supplementary Financial Infor79

Supplementary Financial Information (Schedule Of Employee Benefit Obligations And Other) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Supplementary Financial Information [Abstract]
Retirement plans and other employee benefits	$ 2,035	$ 2,092
Uncertain tax positions (including accrued interest)		3
Investment tax credits	10	12
Other	57	61
Total employee benefit obligations and other	$ 2,102	$ 2,168

Supplementary Financial Infor80

Supplementary Financial Information (Schedule Of Supplemental Cash Flow Information) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplementary Financial Information [Abstract]
Interest		$ 345	$ 336	$ 346
Less capitalized interest		(12)	(8)	(5)
Interest payments (net of amounts capitalized)		333	328	341
Federal		(114)		135
State		20	20	43
Total amount in lieu of income taxes		(94)	20	178
Noncash Sharyland Asset Exchange costs		383
Noncash construction expenditures	[1]	$ 129	$ 122	$ 56
[1]	Represents end-of-period accruals.

Supplementary Financial Infor81

Supplementary Financial Information (Schedule Of Quarterly Information) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplementary Financial Information [Abstract]
Operating revenues	$ 991	$ 1,068	$ 964	$ 935	$ 958	$ 1,071	$ 948	$ 943	$ 3,958	$ 3,920	$ 3,878
Operating income	184	247	197	160	162	250	196	169	788	777	779
Net income	$ 77	$ 157	$ 112	$ 73	$ 77	$ 163	$ 110	$ 81	$ 419	$ 431	$ 432

Sharyland Asset Exchange (Narra

Sharyland Asset Exchange (Narrative) (Details) $ in Millions	Nov. 09, 2017USD ($)micustomeritem	Dec. 31, 2017USD ($)	Dec. 31, 2017USD ($)
Business Acquisition [Line Items]
Cash paid			$ 25
Sharyland Merger Agreement [Member]
Business Acquisition [Line Items]
Transmission of assets	$ 383
Miles of assets transferred | mi	258
Number of assets transferred in circuit miles | mi	517
Number of transmission lines transferred | item	345
Cash paid	$ 25
Purchase price	$ 408
Number of customers acquired | customer	55,000
Distribution revenues		$ 12