Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2015
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. Other significant accounting policies of the Companies are referenced below in this Note A and in the notes that follow.
Plant and Depreciation	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). Non-Utility Plant Non-utility plant is stated at original cost. For Con Edison, non-utility plant consists primarily of the competitive energy businesses’ renewable electric production and gas storage. For the Utilities, non-utility plant consists of land and conduit for telecommunication use.
Goodwill	Goodwill Con Edison tests goodwill for impairment at least annually. 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. See Note K.
Impairments	Impairments Con Edison evaluates the impairment of long-lived assets, 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 and Con Edison Solutions recognize 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 and Con Edison Solutions accrue 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’s competitive energy businesses, which are accounted for under the equity method (depending on the subsidiaries’ percentage ownership). Utilities’ investments are recorded at fair value and include the investments of the deferred income plan and the supplemental retirement income plan in trust-owned life insurance 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 (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 the 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, in accordance with the accounting rules for regulated operations, 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 the 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 tax sharing agreements among the members of the consolidated group. Tax loss 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 Generally 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 FASB and the International Accounting Standards Board (IASB) 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 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. In August 2015, the FASB issued amendments to defer the effective date of ASU No. 2014-09 to reporting periods beginning after December 15, 2017 through ASU No. 2015-14, “Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date”. Early adoption is permitted for reporting periods beginning after December 15, 2016. The Companies are in the process of evaluating the application and impact of the new guidance on the Companies’ financial position, results of operations and liquidity. In January 2015, the FASB issued amendments on income statement guidance through ASU No. 2015-01, “Income Statement—Extraordinary and Unusual Items (Subtopic 225-20).” The amendments eliminate from GAAP the concept of extraordinary items. The amendments are effective for reporting periods beginning after December 15, 2015. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In February 2015, the FASB issued amendments on consolidation guidance through ASU No. 2015-02, “Consolidation (Topic 810).” The amendments provide additional guidance for VIE accounting of limited partnerships and similar legal entities, fees paid to decision makers of a VIE, the effect of fee arrangements on primary beneficiary determination, and the effect of related parties on primary beneficiary determination. The amendments are effective prospectively for reporting periods beginning on or after December 15, 2015. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In April 2015, the FASB issued amendments on internal-use software guidance through ASU No. 2015-05, “Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement.” The amendments provide guidance to customers about whether a cloud computing arrangement should be accounted for as a license of internal use software or as a service contract. For public entities, the amendments are effective for reporting periods beginning on or after December 15, 2015. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In May 2015, the FASB issued amendments on disclosure guidance for investments using Net Asset Value per Share through ASU No. 2015-07, “Fair Value Measurement (Topic 820): Disclosures for Investments in Certain Entities That Calculate Net Asset Value per Share (or Its Equivalent).” The amendments remove the requirement to categorize investments in the fair value hierarchy if Net Asset Value per Share is used as a practical expedient to determine the fair value of the investment. For public entities, the amendments are effective for reporting periods beginning on or after December 15, 2015. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In July 2015, the FASB issued amendments on the measurement of first-in, first-out and average cost inventory through ASU No.2015-11, “Inventory (Topic 330): Simplifying the Measurement of Inventory.” The amendments require that inventory within the scope of the guidance be measured at the lower of cost and net realizable value rather than cost and market value. For public entities, the amendments are effective for reporting periods beginning on or after December 15, 2016. 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 September 2015, the FASB issued an amendment to guidance for business combinations through ASU No. 2015-16, “Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments.” The amendment requires that an acquirer recognize adjustments to provisional amounts that are identified during the measurement period in the reporting period in which the adjustment amounts are determined as opposed to recognizing retrospectively. The amendment also requires that the acquirer record, in the same period’s financial statements, the effect on earnings of changes in depreciation, amortization, or other income effects, if any, as a result of the change to the provisional amounts, calculated as if the accounting had been completed at the acquisition date. For public entities, the amendment is effective prospectively for reporting periods beginning after December 15, 2015. 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 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 fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Early adoption is permitted. 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.