Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2016
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The Companies’ consolidated financial statements include the accounts of their respective majority-owned subsidiaries, and variable interest entities (see Note Q), as required. All intercompany balances and transactions have been eliminated.
Accounting Policies	Accounting Policies The accounting policies of Con Edison and its subsidiaries conform to generally accepted accounting principles in the United States of America (GAAP). For the Utilities, these accounting principles include the accounting rules for regulated operations and the accounting requirements of the Federal Energy Regulatory Commission (FERC) and the state regulators having jurisdiction. The accounting rules for regulated operations specify the economic effects that result from the causal relationship of costs and revenues in the rate-regulated environment and how these effects are to be accounted for by a regulated enterprise. Revenues intended to cover some costs may be recorded either before or after the costs are incurred. If regulation provides assurance that incurred costs will be recovered in the future, these costs would be recorded as deferred charges or “regulatory assets” under the accounting rules for regulated operations. If revenues are recorded for costs that are expected to be incurred in the future, these revenues would be recorded as deferred credits or “regulatory liabilities” under the accounting rules for regulated operations. The Utilities’ principal regulatory assets and liabilities are detailed in Note B. The Utilities are receiving or being credited with a return on all of their regulatory assets for which a cash outflow has been made, and are paying or being charged with a return on all of their regulatory liabilities for which a cash inflow has been received. The Utilities’ regulatory assets and liabilities will be recovered from customers, or applied for customer benefit, in accordance with rate provisions approved by the applicable state regulators.
Plant and Depreciation and Non-Utility Plant	Plant and Depreciation Utility Plant Utility plant is stated at original cost. The cost of repairs and maintenance is charged to expense and the cost of betterments is capitalized. The capitalized cost of additions to utility plant includes indirect costs such as engineering, supervision, payroll taxes, pensions, other benefits and an allowance for funds used during construction (AFUDC). The original cost of property is charged to expense over the estimated useful lives of the assets. Upon retirement, the original cost of property is charged to accumulated depreciation. See Note R. Rates used for AFUDC include the cost of borrowed funds and a reasonable rate of return on the Utilities’ own funds when so used, determined in accordance with regulations of the FERC or the state public utility regulatory authority having jurisdiction. The rate is compounded semiannually, and the amounts applicable to borrowed funds are treated as a reduction of interest charges, while the amounts applicable to the Utilities’ own funds are credited to other income (deductions). The AFUDC rates for CECONY were 4.7 percent, 4.4 percent and 1.6 percent for 2016, 2015 and 2014, respectively. The AFUDC rates for O&R were 3.5 percent, 0.4 percent and 2.6 percent for 2016, 2015 and 2014, respectively. The Utilities generally compute annual charges for depreciation using the straight-line method for financial statement purposes, with rates based on average service lives and net salvage factors. The average depreciation rates for CECONY were 3.1 percent for 2016, 2015 and 2014. The average depreciation rates for O&R were 2.9 percent, 3.0 percent and 2.9 percent for 2016, 2015 and 2014, respectively. The estimated lives for utility plant for CECONY range from 5 to 85 years for electric and gas, 5 to 80 years for steam and 5 to 55 years for general plant. For O&R, the estimated lives for utility plant range from 5 to 75 years for electric and gas and 5 to 50 years for general plant. Non-Utility Plant Non-utility plant is stated at original cost. For Con Edison, non-utility plant consists primarily of the Clean Energy Businesses’ renewable electric production and gas storage. For the Utilities, non-utility plant consists of land and conduit for telecommunication use. Depreciation on these assets is computed using the straight-line method for financial statement purposes over their estimated useful lives, which range from 3 to 30 years.
Goodwill	Goodwill Con Edison tests goodwill for impairment at least annually or whenever there is a triggering event. There is an option to first make a qualitative assessment of whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount before applying a two-step, quantitative goodwill impairment test. However, Con Edison has not elected to perform the qualitative assessment and exclusively applies the two-step quantitative approach. The first step of the goodwill impairment test compares the estimated fair value of a reporting unit with its carrying value, including goodwill. If the estimated fair value of a reporting unit exceeds its carrying value, goodwill of the reporting unit is considered not impaired. If the carrying value exceeds the estimated fair value of the reporting unit, the second step is performed to measure the amount of impairment loss, if any. The second step requires a calculation of the implied fair value of goodwill.
Long-Lived and Intangible Assets	Long-Lived and Intangible Assets Con Edison evaluates the impairment of long-lived assets and intangible assets with definite lives, based on projections of undiscounted future cash flows, whenever events or changes in circumstances indicate that the carrying amounts of such assets may not be recoverable. In the event an evaluation indicates that such cash flows cannot be expected to be sufficient to fully recover the assets, the assets are written down to their estimated fair value.
Revenues	Revenues The Utilities recognize and, until the sale of its retail electric supply business in September 2016 (see Note U), Con Edison Solutions recognized revenues for energy service on a monthly billing cycle basis. The Utilities defer over a 12-month period net interruptible gas revenues, other than those authorized by the NYSPSC to be retained by the Utilities, for refund to firm gas sales and transportation customers. The Utilities accrue and Con Edison Solutions accrued revenues at the end of each month for estimated energy service not yet billed to customers. CECONY’s electric and gas rate plans and O&R’s New York electric and gas rate plans each contain a revenue decoupling mechanism under which the company’s actual energy delivery revenues are compared with the authorized delivery revenues and the difference accrued, with interest, for refund to, or recovery from, customers, as applicable. See “Rate Plans” in Note B. The NYSPSC requires utilities to record gross receipts tax revenues and expenses on a gross income statement presentation basis (i.e., included in both revenue and expense). The recovery of these taxes is generally provided for in the revenue requirement within each of the respective NYSPSC approved rate plans.
Recoverable Energy Costs/New York Independent System Operator (NYISO)	Recoverable Energy Costs The Utilities generally recover all of their prudently incurred fuel, purchased power and gas costs, including hedging gains and losses, in accordance with rate provisions approved by the applicable state public utility regulators. If the actual energy supply costs for a given month are more or less than the amounts billed to customers for that month, the difference in most cases is recoverable from or refundable to customers. Differences between actual and billed electric and steam supply costs and costs of its electric demand management programs are generally deferred for charge or refund to customers during the next billing cycle (normally within one or two months). For the Utilities’ gas costs, differences between actual and billed gas costs during the 12-month period ending each August are charged or refunded to customers during a subsequent 12-month period. New York Independent System Operator (NYISO) The Utilities purchase electricity through the wholesale electricity market administered by the NYISO. The difference between purchased power and related costs initially billed to the Utilities by the NYISO and the actual cost of power subsequently calculated by the NYISO is refunded by the NYISO to the Utilities, or paid to the NYISO by the Utilities. The reconciliation payments or receipts are recoverable from or refundable to the Utilities’ customers. Certain other payments to or receipts from the NYISO are also subject to reconciliation, with shortfalls or amounts in excess of specified rate allowances recoverable from or refundable to customers. These include proceeds from the sale through the NYISO of transmission rights on CECONY’s transmission system (transmission congestion contracts or TCCs).
Temporary Cash Investments	Temporary Cash Investments Temporary cash investments are short-term, highly-liquid investments that generally have maturities of three months or less at the date of purchase. They are stated at cost, which approximates market. The Companies consider temporary cash investments to be cash equivalents.
Investments	Investments Investments consist primarily of the investments of Con Edison Transmission and the Clean Energy Businesses that are accounted for under the equity method and the fair value of the Utilities’ supplemental retirement income plan and deferred income plan assets.
Pension and Other Postretirement Benefits	Pension and Other Postretirement Benefits The accounting rules for retirement benefits require an employer to recognize an asset or liability for the overfunded or underfunded status of its pension and other postretirement benefit plans. For a pension plan, the asset or liability is the difference between the fair value of the plan’s assets and the projected benefit obligation. For any other postretirement benefit plan, the asset or liability is the difference between the fair value of the plan’s assets and the accumulated postretirement benefit obligation. The accounting rules generally require employers to recognize all unrecognized prior service costs and credits and unrecognized actuarial gains and losses in accumulated other comprehensive income/(loss) (OCI), net of tax. Such amounts will be adjusted as they are subsequently recognized as components of total periodic benefit cost or income pursuant to the current recognition and amortization provisions. For the Utilities’ pension and other postretirement benefit plans, regulatory accounting treatment is generally applied in accordance with the accounting rules for regulated operations. Unrecognized prior service costs or credits and unrecognized actuarial gains and losses are recorded to regulatory assets or liabilities, rather than OCI. See Notes E and F. The total periodic benefit costs are recognized in accordance with the accounting rules for retirement benefits. Investment gains and losses are recognized in expense over a 15-year period and other actuarial gains and losses are recognized in expense over a 10-year period, subject to the deferral provisions in the rate plans. In accordance with the Statement of Policy issued by the NYSPSC and its current electric, gas and steam rate plans, CECONY defers for payment to or recovery from customers the difference between such expenses and the amounts for such expenses reflected in rates. Generally, O&R also defers such difference pursuant to its rate plans. See Note B. The Companies calculate the expected return on pension and other postretirement benefit plan assets by multiplying the expected rate of return on plan assets by the market-related value (MRV) of plan assets at the beginning of the year, taking into consideration anticipated contributions and benefit payments that are to be made during the year. The accounting rules allow the MRV of plan assets to be either fair value or a calculated value that recognizes changes in fair value in a systematic and rational manner over not more than five years. The Companies use a calculated value when determining the MRV of the plan assets that adjusts for 20 percent of the difference between fair value and expected MRV of plan assets. This calculated value has the effect of stabilizing variability in assets to which the Companies apply the expected return.
Federal Income Tax/State Income Tax	Federal Income Tax In accordance with accounting rules for income taxes, the Companies have recorded an accumulated deferred federal income tax liability at current tax rates for temporary differences between the book and tax basis of assets and liabilities. In accordance with rate plans, the Utilities have recovered amounts from customers for a portion of the tax liability they will pay in the future as a result of the reversal or “turn-around” of these temporary differences. As to the remaining tax liability, the Utilities have established regulatory assets for the net revenue requirements to be recovered from customers for the related future tax expense. See Notes B and L. In 1993, the NYSPSC issued a Policy Statement approving accounting procedures consistent with accounting rules for income taxes and providing assurances that these future increases in taxes will be recoverable in rates. See Note L. Accumulated deferred investment tax credits are amortized ratably over the lives of the related properties and applied as a reduction to future federal income tax expense. Con Edison and its subsidiaries file a consolidated federal income tax return. The consolidated income tax liability is allocated to each member of the consolidated group using the separate return method. Each member pays or receives an amount based on its own taxable income or loss in accordance with a consolidated tax allocation agreement. Tax loss and tax credit carryforwards are allocated among members in accordance with consolidated tax return regulations. State Income Tax Con Edison and its subsidiaries file a combined New York State Corporation Business Franchise Tax Return. Similar to a federal consolidated income tax return, the income of all entities in the combined group is subject to New York State taxation, after adjustments for differences between federal and New York law and apportionment of income among the states in which the company does business. Each member’s share of the New York State tax is based on its own New York State taxable income or loss.
Research and Development Costs	Research and Development Costs Research and development costs are charged to operating expenses as incurred.
Reclassification	Reclassification Certain prior year amounts have been reclassified to conform with the current year presentation.
Earnings Per Common Share	Earnings Per Common Share Con Edison presents basic and diluted earnings per share on the face of its consolidated income statement. Basic earnings per share (EPS) are calculated by dividing earnings available to common shareholders (“Net income” on Con Edison’s consolidated income statement) by the weighted average number of Con Edison common shares outstanding during the period. In the calculation of diluted EPS, weighted average shares outstanding are increased for additional shares that would be outstanding if potentially dilutive securities were converted to common stock. Potentially dilutive securities for Con Edison consist of restricted stock units, deferred stock units and stock options for which the average market price of the common shares for the period was greater than the exercise price.
Estimates	Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
New Financial Accounting Standards	New Financial Accounting Standards In May 2014, the Financial Accounting Standards Board (FASB) and the International Accounting Standards Board jointly issued a revenue recognition standard that will supersede the revenue recognition requirements within Accounting Standards Codification Topic 605, “Revenue Recognition,” and most industry-specific guidance under the Codification through Accounting Standards Update (ASU) No. 2014-09, “Revenue from Contracts with Customers (Topic 606).” The purpose of the new guidance is to create a consistent framework for revenue recognition. The guidance clarifies how to measure and recognize revenue arising from customer contracts to depict the transfer of goods or services in an amount that reflects the consideration the entity expects to receive. Amendments were issued subsequently to clarify key areas including principal/agent considerations, performance obligations, licensing, sales taxes, noncash consideration, and contracts. The new standard is effective for reporting periods beginning after December 15, 2017. Early adoption is permitted for reporting periods beginning after December 15, 2016, however, the Companies plan to adopt the new standard for reporting periods beginning after December 15, 2017. Under the new standard, companies may use either of the following transition methods: (i) a full retrospective approach reflecting the application of the standard in each prior reporting period with the option to elect certain practical expedients, or (ii) a modified retrospective approach with the cumulative effect of initially adopting ASU 2014-09 recognized at the date of adoption (which includes additional footnote disclosures). The Companies anticipate using the modified retrospective approach. The Companies are currently in the process of evaluating the impact of the new standard on their various revenue streams. The majority of the Companies’ sales are derived from tariffs to provide electric, gas, and steam service to customers. For such tariffs, the Companies expect that the revenue from contracts with the customer under ASU 2014-09 will be equivalent to the electricity, gas, or steam supplied in that period which is consistent with current practice. Consequently, the Companies do not anticipate that the new standard will significantly impact the amount and/or timing of such revenues. The Companies continue to review the potential impacts of other revenue at the Utilities and the Clean Energy Businesses on the Companies' financial position, results of operations and liquidity as well as the additional disclosures required under the new standard. In January 2016, the FASB issued amendments on certain aspects of recognition, measurement, presentation, and disclosure of financial instruments through ASU No. 2016-01, “Financial Instruments (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities.” The amendments require changes to the accounting for equity investments, the presentation and disclosure requirements for financial liabilities under the fair value option, and the presentation and disclosure requirements for financial instruments. In addition, clarification was provided related to the valuation allowance assessment when recognizing deferred tax assets resulting from unrealized losses on available-for-sale debt securities. For public entities, the amendments are effective for reporting periods beginning after December 15, 2017. Early adoption is permitted for portions of the standard. The Companies are in the process of evaluating the potential impact of the new guidance on the Companies’ financial position, results of operations and liquidity. In February 2016, the FASB issued amendments on financial reporting of leasing transactions through ASU No. 2016-02, “Leases (Topic 842)." The amendments require lessees to recognize assets and liabilities on the balance sheet and disclose key information about leasing arrangements. Lessees will need to recognize a right-of-use asset and a lease liability for virtually all of their leases (other than leases that meet the definition of a short-term lease). Lessor accounting is similar to the current model, but updated to align with certain changes to the lessee model. For income statement purposes, the pattern of expense recognition will be dependent on whether transactions are designated as operating leases or finance leases. The amendments are effective for reporting periods beginning after December 15, 2018. Early adoption is permitted. The amendments must be adopted using a modified retrospective transition and provide for certain practical expedients. Based on the existing portfolio of leases at implementation, for leases currently classified as operating leases, the Companies expect to recognize on the statements of financial position right-of-use assets and lease liabilities. The Companies are in the process of evaluating the potential impact of the new guidance on the Companies’ results of operations and liquidity. In March 2016, the FASB issued amendments to the guidance for Derivatives and Hedging accounting through ASU 2016-05, “Derivatives and Hedging (Topic 815): Effect of Derivative Contract Novations on Existing Hedge Accounting Relationships." The amendments clarify that a change in the counterparty to a derivative instrument that has been designated as a hedging instrument under Topic 815 does not, in and of itself, require discontinuation of the application of hedge accounting. The amendments in this update are effective for financial statements issued for reporting periods beginning after December 15, 2016. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In March 2016, the FASB issued amendments to clarify the guidance for assessing whether contingent call (put) options that can accelerate the payment of principal on debt instruments are clearly and closely related to their debt hosts through ASU No. 2016-06, “Derivatives & Hedging (Topic 815): Contingent Put and Call Options in Debt Instruments.” An entity performing the assessment under the amendments is required to assess the embedded call (put) options solely in accordance with the four-step decision sequence. The amendments are effective for financial statements issued for reporting periods beginning after December 15, 2016. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In March 2016, the FASB issued amendments to eliminate the requirement to retroactively adopt the equity method of accounting when a company increases its level of ownership or degree of influence over an investment through ASU No. 2016-07, “Investments-Equity Method and Joint Ventures (Topic 323): Simplifying the Transition to the Equity Method of Accounting.” The amendments require that an entity that has an available-for-sale equity security that becomes qualified for the equity method of accounting recognize through earnings the unrealized holding gain or loss in Accumulated Other Comprehensive Income at the date the investment qualifies for the equity method. The amendments are effective for reporting periods beginning after December 15, 2016. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In March 2016, the FASB issued amendments to simplify several aspects of the accounting for share-based payment transactions through ASU No. 2016-09, “Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting.” The amendments simplify areas such as income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. The amendments are effective for reporting periods beginning after December 15, 2016. The company elected to early adopt this standard as permitted, and it did not have a material impact on the Companies’ financial position, results of operations and liquidity. In May 2016, the FASB issued amendments to the guidance on revenue recognition and derivatives and hedging through ASU 2016-11, “Revenue Recognition (Topic 605) and Derivatives and Hedging (Topic 815): Rescission of SEC Guidance Because of Accounting Standards Updates 2014-09 and 2014-16 Pursuant to Staff Announcements at the March 3, 2016 EITF Meeting (SEC Update).” The amendment rescinds certain SEC guidance superseded by the newly issued revenue recognition and hedging guidance (ASU 2014-09 and 2014-16 respectively). The amendments will be effective upon adoption of ASU 2014-09 and 2014-16. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In June 2016, the FASB issued amendments to the guidance for recognition of credit losses for financial instruments through ASU 2016-13, “Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments.” The amendment replaces the incurred loss impairment methodology which involved delayed recognition of credit losses. As the updated guidance now requires credit losses to be recognized when expected rather than when incurred, a broader range of reasonable and supportable information must be considered in developing the credit loss estimates. This includes financial instruments that are valued at amortized cost and available for sale. For public entities, the amendments are effective for reporting periods beginning after December 15, 2019. Early adoption is permitted for reporting periods beginning after December 15, 2018. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In August 2016, the FASB issued amendments to the guidance for the Statement of Cash Flows through ASU 2016-15, “Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (a consensus of the Emerging Issues Task Force).” The amendment specifies the classification and presentation of certain cash flow items to reduce diversity in practice. For public entities, the amendments are effective for reporting periods beginning after December 15, 2017. Early adoption is permitted. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In October 2016, the FASB issued amendments to the guidance for Income Taxes through ASU 2016-16, “Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory).” The amendment clarifies the tax treatment of intra-entity transfers of assets other than inventory. The updated guidance requires entities to recognize the income tax consequences of an intra-entity transfer of assets other than inventory when the transfer occurs. For public entities, the amendments are effective for reporting periods beginning after December 15, 2017. Early adoption is permitted. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In October 2016, the FASB issued amendments to the guidance for Consolidation through ASU 2016-17, “Consolidation (Topic 810): Interests Held through Related Parties That Are under Common Control.” The amendments in this update change how a single decision maker of a VIE will consider its indirect interests in a VIE held by related parties under common control when performing the primary beneficiary analysis. If a single decision maker and its related parties are under common control, the single decision maker must evaluate indirect interests on a proportionate basis when evaluating whether it is a primary beneficiary of the VIE. The guidance does not change the characteristics of a primary beneficiary under GAAP but has amended the considerations in the evaluation of determining the primary beneficiary of a VIE under common control. For public entities, the amendments are effective for reporting periods beginning after December 15, 2016. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In November 2016, the FASB issued amendments to the guidance for the Statement of Cash Flows through ASU 2016-18, “Update 2016-18-Statement of Cash Flows (Topic 230): Restricted Cash (a consensus of the FASB Emerging Issues Task Force).” The amendments in this update clarify the presentation of changes in restricted cash and restricted cash equivalents in the statement of cash flows. For public entities, the amendments are effective for reporting periods beginning after December 15, 2017. Early adoption is permitted. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In January 2017, the FASB issued amendments to the guidance for Business Combinations through ASU 2017-01, “Business Combinations (Topic 805): Clarifying the Definition of a Business.” The amendments in this update clarify the definition of a business and provide guidance on evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. For public entities, the amendments are effective for reporting periods beginning after December 15, 2017. Early adoption is permitted. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In January 2017, the FASB issued amendments to the guidance for the subsequent measurement of goodwill through ASU 2017-04, “Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment.” The amendments in this update simplify goodwill impairment testing by eliminating Step 2 of the goodwill impairment test wherein an entity has to compute the implied fair value of goodwill by performing procedures to determine the fair value of its assets and liabilities. Under the new guidance, an entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value up to the total amount of goodwill allocated to that reporting unit. For public entities, the amendments are effective for reporting periods beginning after December 15, 2019. Early adoption is permitted. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity.