New Financial Accounting Standards	12 Months Ended
Dec. 31, 2017
Accounting Changes and Error Corrections [Abstract]
New Financial Accounting Standards	New Financial Accounting Standards In January 2018, the Companies adopted Accounting Standards Update (ASU) No. 2014-09, “Revenue from Contracts with Customers (Topic 606),” including the amendments thereto, (the New Standard) using the modified retrospective approach the New Standard permitted. The New Standard supersedes the revenue recognition requirements within Accounting Standards Codification Topic 605, “Revenue Recognition,” and most industry-specific guidance (the Superseded Standard). The purpose of the New Standard is to create a consistent framework for revenue recognition. The New Standard 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. The New Standard also clarifies key areas including principal/agent considerations, performance obligations, licensing, sales taxes, noncash consideration, and contracts. The majority of Con Edison’s’ revenues and substantially all of CECONY’s revenues are derived from the provision of electric, gas, and steam service to customers pursuant to the terms of tariffs approved by the NYSPSC or NJBPU. For such service, the Companies expect that the revenue from contracts with customers for a period that will be recorded under the New Standard will be equivalent to the revenue for the period that would have been recorded under the Superseded Standard. Most of Con Edison’s other revenues are derived from the Clean Energy Businesses’ sale of energy-related products and services, operation of renewable and energy infrastructure projects, and sale of renewable energy credits. For such businesses, Con Edison expects that the revenue from contracts with customers for a period that will be recorded under the New Standard will not be materially different from the revenue for the period that would have been recorded under the Superseded Standard. Under the modified retrospective method of adoption, prior year reported results are not restated and a cumulative-effect adjustment, if applicable, is recorded to retained earnings at January 1, 2018. As of January 1, 2018, the cumulative-effect adjustment was not material to the Companies. The Companies also plan to use certain practical expedients including applying this guidance to open contracts at the date of adoption and recognizing revenues for certain contracts under the invoice practical expedient. Such expedients allow revenue recognition to be consistent with invoiced amounts (including estimated billings) provided certain criteria are met, including consideration of whether the invoiced amounts reasonably represent the value provided to customers. The adoption of the New Standard will not have a material impact on the Companies’ financial statements, results of operations, and liquidity, including the presentation of revenues in their consolidated income statements. The adoption of the New Standard will not require a change in the Companies’ internal control over financial reporting that is reasonably likely to materially affect their internal control over financial reporting. 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 depend on whether transactions are designated as operating leases or finance leases. In January 2018, the FASB issued amendments on the lease standard’s application to land easements through ASU No. 2018-01, “Leases (Topic 842): Land Easement Practical Expedient for Transition to Topic 842.” The amendments allow an entity to not evaluate under Topic 842 land easements that exist or expired before the entity’s adoption of Topic 842 and that were not previously accounted for as leases under the current lease standard. 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 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. 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. In February 2017, the FASB issued amendments to the guidance for other income through ASU 2017-05, “Other Income-Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets.” The amendments in this update clarify the scope of assets within Subtopic 610-20 and add guidance for partial sales of nonfinancial assets. The amendments are effective upon the adoption of ASU 2014-09, and therefore will be effective for reporting periods beginning after December 15, 2017. 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 2017, the FASB issued amendments to the guidance for retirement benefits through ASU 2017-07, “Compensation-Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost.” The amendments in this update modify the presentation of net benefit cost, where the service component must be disaggregated from the other components of net benefit cost and be presented in the same line item as current employee compensation costs. The remaining components of the net benefit cost should be presented outside of income from operations. Additionally, the update allows only the service cost component to be eligible for capitalization. For public entities, the amendments are effective for reporting periods beginning after December 15, 2017. The guidance allows a practical expedient that permits the use of amounts disclosed in prior-period financial statements as appropriate estimates when applying the presentation requirements retrospectively. The Companies have elected to use the practical expedient under ASU 2017-07. 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 2017, the FASB issued amendments to the guidance for debt securities through ASU 2017-08, “Receivables-Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities.” The amendments in this update shorten the amortization period for certain callable debt securities held at a premium. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. For public entities, the amendments are effective for reporting periods beginning after December 15, 2018. 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 May 2017, the FASB issued amendments to the guidance for stock compensation through ASU 2017-09, “Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting.” The amendments in this update specify that changes to value, vesting conditions, or classification of an existing share-based payment award require application of modification accounting in Topic 718. For public entities, the amendments are effective for reporting periods beginning after December 15, 2017.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 2017, the FASB issued amendments to the guidance for derivatives and hedging through ASU 2017-12, “Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities.” The amendments in this update provide greater clarification on hedge accounting for risk components, presentation and disclosure of hedging instruments, and overall targeted improvements to simplify hedge accounting. For public entities, the amendments are effective for reporting periods beginning after December 15, 2018. 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. In February 2018, the FASB issued amendments to the guidance for reporting comprehensive income through ASU 2018-02, “Income Statement-Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income.” The amendments allow a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the TCJA. For public entities, the amendments are effective for reporting periods beginning after December 15, 2018. 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.

New Financial Accounting Standards

In January 2018, the Companies adopted Accounting Standards Update (ASU) No. 2014-09, “Revenue from Contracts with Customers (Topic 606),” including the amendments thereto, (the New Standard) using the modified retrospective approach the New Standard permitted. The New Standard supersedes the revenue recognition requirements within Accounting Standards Codification Topic 605, “Revenue Recognition,” and most industry-specific guidance (the Superseded Standard). The purpose of the New Standard is to create a consistent framework for revenue recognition. The New Standard 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. The New Standard also clarifies key areas including principal/agent considerations, performance obligations, licensing, sales taxes, noncash consideration, and contracts.

The majority of Con Edison’s’ revenues and substantially all of CECONY’s revenues are derived from the provision of electric, gas, and steam service to customers pursuant to the terms of tariffs approved by the NYSPSC or NJBPU. For such service, the Companies expect that the revenue from contracts with customers for a period that will be recorded under the New Standard will be equivalent to the revenue for the period that would have been recorded under the Superseded Standard. Most of Con Edison’s other revenues are derived from the Clean Energy Businesses’ sale of energy-related products and services, operation of renewable and energy infrastructure projects, and sale of renewable energy credits. For such businesses, Con Edison expects that the revenue from contracts with customers for a period that will be recorded under the New Standard will not be materially different from the revenue for the period that would have been recorded under the Superseded Standard.

Under the modified retrospective method of adoption, prior year reported results are not restated and a cumulative-effect adjustment, if applicable, is recorded to retained earnings at January 1, 2018. As of January 1, 2018, the cumulative-effect adjustment was not material to the Companies. The Companies also plan to use certain practical expedients including applying this guidance to open contracts at the date of adoption and recognizing revenues for certain contracts under the invoice practical expedient. Such expedients allow revenue recognition to be consistent with invoiced amounts (including estimated billings) provided certain criteria are met, including consideration of whether the invoiced amounts reasonably represent the value provided to customers.

The adoption of the New Standard will not have a material impact on the Companies’ financial statements, results of operations, and liquidity, including the presentation of revenues in their consolidated income statements. The adoption of the New Standard will not require a change in the Companies’ internal control over financial reporting that is reasonably likely to materially affect their internal control over financial reporting.

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 depend on whether transactions are designated as operating leases or finance leases. In January 2018, the FASB issued amendments on the lease standard’s application to land easements through ASU No. 2018-01, “Leases (Topic 842): Land Easement Practical Expedient for Transition to Topic 842.” The amendments allow an entity to not evaluate under Topic 842 land easements that exist or expired before the entity’s adoption of Topic 842 and that were not previously accounted for as leases under the current lease standard. 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 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. 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.

In February 2017, the FASB issued amendments to the guidance for other income through ASU 2017-05, “Other Income-Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets.” The amendments in this update clarify the scope of assets within Subtopic 610-20 and add guidance for partial sales of nonfinancial assets. The amendments are effective upon the adoption of ASU 2014-09, and therefore will be effective for reporting periods beginning after December 15, 2017. 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 2017, the FASB issued amendments to the guidance for retirement benefits through ASU 2017-07, “Compensation-Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost.” The amendments in this update modify the presentation of net benefit cost, where the service component must be disaggregated from the other components of net benefit cost and be presented in the same line item as current employee compensation costs. The remaining components of the net benefit cost should be presented outside of income from operations. Additionally, the update allows only the service cost component to be eligible for capitalization. For public entities, the amendments are effective for reporting periods beginning after December 15, 2017. The guidance allows a practical expedient that permits the use of amounts disclosed in prior-period financial statements as appropriate estimates when applying the presentation requirements retrospectively. The Companies have elected to use the practical expedient under ASU 2017-07. 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 2017, the FASB issued amendments to the guidance for debt securities through ASU 2017-08, “Receivables-Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities.” The amendments in this update shorten the amortization period for certain callable debt securities held at a premium. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. For public entities, the amendments are effective for reporting periods beginning after December 15, 2018. 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 May 2017, the FASB issued amendments to the guidance for stock compensation through ASU 2017-09, “Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting.” The amendments in this update specify that changes to value, vesting conditions, or classification of an existing share-based payment award require application of modification accounting in Topic 718. For public entities, the amendments are effective for reporting periods beginning after December 15, 2017.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 2017, the FASB issued amendments to the guidance for derivatives and hedging through ASU 2017-12, “Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities.” The amendments in this update provide greater clarification on hedge accounting for risk components, presentation and disclosure of hedging instruments, and overall targeted improvements to simplify hedge accounting. For public entities, the amendments are effective for reporting periods beginning after December 15, 2018. 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.

In February 2018, the FASB issued amendments to the guidance for reporting comprehensive income through ASU 2018-02, “Income Statement-Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income.” The amendments allow a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the TCJA. For public entities, the amendments are effective for reporting periods beginning after December 15, 2018. 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.