Acquisitions, Investments and Dispositions	12 Months Ended
Dec. 31, 2017
Business Combinations [Abstract]
Acquisitions, Investments and Dispositions	Acquisitions, Investments and Dispositions Acquisitions and Investments Texas Solar 7 In January 2016, Con Edison Development acquired a 100 percent equity interest in a company that is the owner of a 106 MW (AC) solar electric production project in Texas (Texas Solar 7) for $227 million, as to which $218 million was recorded as non-utility construction work in progress and the remaining $9 million was recorded as other receivables. The project commenced commercial operation in the third quarter of 2016. The project has been financed, in part, by debt secured by the project. Electricity generated by this project is to be purchased by the City of San Antonio pursuant to a long-term power purchase agreement. At December 31, 2017 and 2016, net assets of the project were approximately $137 million and $127 million, respectively, (including $41 million for an intangible asset pertaining to the value of the power purchase agreement). Con Edison's equity interest in Texas Solar 7 is consolidated in the financial statements. Mountain Valley Pipeline In January 2016, CET Gas acquired a 12.5 percent equity interest in MVP, a company developing a proposed gas transmission project in West Virginia and Virginia. The company's initial contribution to MVP was $18 million. At December 31, 2017 and 2016, CET Gas' investment in MVP was $98 million and $48 million, respectively. MVP has indicated that the project has an estimated total cost of $3,000 million to $3,500 million and is targeted to be fully in-service during the fourth quarter of 2018. Con Edison is accounting for its equity interest in MVP as an equity method investment. NY Transco In May 2016, CECONY transferred certain electric transmission projects to NY Transco, a company in which CET Electric has a 45.7 percent equity interest, for a purchase price of $122 million and an $8 million payment for associated easement rights. At December 31, 2017 and 2016, CET Electric's investment in NY Transco was $53 million and $51 million, respectively. Con Edison is accounting for its equity interest in NY Transco as an equity method investment. Stagecoach Gas Services In April 2016, a CET Gas subsidiary agreed with a subsidiary of Crestwood to form a joint venture to own, operate and further develop existing gas pipeline and storage businesses located in northern Pennsylvania and southern New York. The transaction was substantially completed in June 2016, and the remainder was completed in November 2016. Crestwood contributed businesses to a new entity, Stagecoach, and the CET Gas subsidiary contributed $974 million for a 50 percent equity interest in Stagecoach. At December 31, 2017 and 2016, CET Gas' investment in Stagecoach was $971 million and $992 million, respectively. Con Edison is accounting for its equity interest in Stagecoach as an equity method investment. Pilesgrove In June 2016, Con Edison Development recorded an $8 million ($5 million, net of taxes) impairment charge on its 50 percent equity interest in Pilesgrove Solar, LLC (Pilesgrove), which owns an 18 MW (AC) solar electric production project in New Jersey. In August 2016, Con Edison Development acquired the remaining 50 percent equity interest in Pilesgrove for a purchase price of approximately $16 million and recorded a bargain purchase gain of $8 million ($5 million, net of taxes); $45 million was recorded as non-utility property and the remaining $3 million was recorded as current assets. The impairment charge and bargain purchase gain are included in Investment and other income on Con Edison’s consolidated income statement. At December 31, 2017 and 2016, net assets of the project were approximately $45 million. Con Edison's equity interest in Pilesgrove is consolidated in the financial statements. Panoche Valley In October 2016, Con Edison Development, which owned a 50 percent equity interest, acquired the remaining 50 percent equity interest in Panoche Holdings, LLC (Panoche), which is developing a 240 MW (AC) solar electric production project in California, for cash consideration of $28 million and the release of Panoche from its obligation under a $242 million note payable to Con Edison Development. At the time of acquisition, $290 million was recorded as non-utility construction work in process, $22 million was recorded as other assets and $14 million was recorded as current liabilities. A part of the project commenced commercial operation in December 2017. At December 31, 2017 and 2016, net assets of the project were approximately $435 million and $388 million, respectively. Con Edison's equity interest in Panoche is consolidated in the financial statements. Coram Wind In December 2016, Con Edison Development acquired a 100 percent equity interest in Coram California Development, LP (Coram), which owns a 102 MW (AC) wind electric production project in California for $97 million, as to which $191 million was recorded as non-utility property, $78 million was recorded as an intangible asset, $8 million of restricted cash was recorded as other current assets, and $180 million was recorded as long term debt. In December 2017, an increase of $22 million was recorded to the intangible asset and a corresponding decrease was recorded to non-utility property. The intangible asset pertains to the value of the project's power purchase agreement, relative to current market rates, and is being amortized over the life of the agreement. The project commenced commercial operation in March 2012. At December 31, 2017 and 2016, net assets of the project were approximately $87 million and $96 million, respectively. Con Edison's equity interest in Coram is consolidated in the financial statements. Dispositions Pike County Light & Power Company (Pike) In October 2015, O&R entered into an agreement to sell Pike to Corning Natural Gas Holding Corporation (Corning). In August 2016, the sale was completed. O&R received cash consideration of $15 million for the sale. O&R has agreed to provide transition services to Corning for operations and customer support for a period of up to 18 months subsequent to the sale. In addition, O&R will continue to purchase and sell to Pike electric and gas commodity for three years. Pike has an option to extend the commodity procurement service for up to an additional three years. At September 30, 2015, O&R recorded an impairment charge of $5 million ($3 million, net of taxes), representing the difference between the carrying amount of Pike’s assets and the estimated sales proceeds. Con Edison Solutions' Retail Electric Supply Business In July 2016, Con Edison Solutions entered into an agreement to sell the assets of its retail electric supply business (including retail contracts, related derivative instruments, information systems, and accounts receivable) to a subsidiary of Exelon Corporation (Exelon). In September 2016, the sale was completed for cash consideration of $235 million, subject to working capital adjustments. The sale resulted in a gain of $104 million ($56 million, net of taxes), inclusive of a $65 million ($42 million, net of taxes) gain on derivative instruments. The tax effect of the sale included $16 million ($10 million, net of federal tax) of state taxes related to a change in the apportionment of state income taxes. Con Edison Solutions provided transition services to the Exelon subsidiary for operations and customer support through January 2018 during a portion of which period certain guarantees or other credit support provided by Con Edison in connection with the retail electric supply business continued in effect. See Note H. Upton 2 In May 2017, Con Edison Development sold Upton 2, a development stage solar electric production project, for $11 million to Vistra Asset Co. and recorded a $1 million gain on sale ($0.7 million, net of taxes). In addition, Con Edison Development agreed to perform the engineering, procurement and construction for the 180 MW (AC) project, which is expected to be substantially completed in 2018.

Acquisitions, Investments and Dispositions

Acquisitions and Investments

Texas Solar 7

In January 2016, Con Edison Development acquired a 100 percent equity interest in a company that is the owner of a 106 MW (AC) solar electric production project in Texas (Texas Solar 7) for $227 million, as to which $218 million was recorded as non-utility construction work in progress and the remaining $9 million was recorded as other receivables. The project commenced commercial operation in the third quarter of 2016. The project has been financed, in part, by debt secured by the project. Electricity generated by this project is to be purchased by the City of San Antonio pursuant to a long-term power purchase agreement. At December 31, 2017 and 2016, net assets of the project were approximately $137 million and $127 million, respectively, (including $41 million for an intangible asset pertaining to the value of the power purchase agreement). Con Edison's equity interest in Texas Solar 7 is consolidated in the financial statements.

Mountain Valley Pipeline

In January 2016, CET Gas acquired a 12.5 percent equity interest in MVP, a company developing a proposed gas transmission project in West Virginia and Virginia. The company's initial contribution to MVP was $18 million. At December 31, 2017 and 2016, CET Gas' investment in MVP was $98 million and $48 million, respectively. MVP has indicated that the project has an estimated total cost of $3,000 million to $3,500 million and is targeted to be fully in-service during the fourth quarter of 2018. Con Edison is accounting for its equity interest in MVP as an equity method investment.

NY Transco

In May 2016, CECONY transferred certain electric transmission projects to NY Transco, a company in which CET Electric has a 45.7 percent equity interest, for a purchase price of $122 million and an $8 million payment for associated easement rights. At December 31, 2017 and 2016, CET Electric's investment in NY Transco was $53 million and $51 million, respectively. Con Edison is accounting for its equity interest in NY Transco as an equity method investment.

Stagecoach Gas Services

In April 2016, a CET Gas subsidiary agreed with a subsidiary of Crestwood to form a joint venture to own, operate and further develop existing gas pipeline and storage businesses located in northern Pennsylvania and southern New York. The transaction was substantially completed in June 2016, and the remainder was completed in November 2016. Crestwood contributed businesses to a new entity, Stagecoach, and the CET Gas subsidiary contributed $974 million for a 50 percent equity interest in Stagecoach. At December 31, 2017 and 2016, CET Gas' investment in Stagecoach was $971 million and $992 million, respectively. Con Edison is accounting for its equity interest in Stagecoach as an equity method investment.

Pilesgrove

In June 2016, Con Edison Development recorded an $8 million ($5 million, net of taxes) impairment charge on its 50 percent equity interest in Pilesgrove Solar, LLC (Pilesgrove), which owns an 18 MW (AC) solar electric production project in New Jersey. In August 2016, Con Edison Development acquired the remaining 50 percent equity interest in Pilesgrove for a purchase price of approximately $16 million and recorded a bargain purchase gain of $8 million ($5 million, net of taxes); $45 million was recorded as non-utility property and the remaining $3 million was recorded as current assets. The impairment charge and bargain purchase gain are included in Investment and other income on Con Edison’s consolidated income statement. At December 31, 2017 and 2016, net assets of the project were approximately $45 million. Con Edison's equity interest in Pilesgrove is consolidated in the financial statements.

Panoche Valley

In October 2016, Con Edison Development, which owned a 50 percent equity interest, acquired the remaining 50 percent equity interest in Panoche Holdings, LLC (Panoche), which is developing a 240 MW (AC) solar electric production project in California, for cash consideration of $28 million and the release of Panoche from its obligation under a $242 million note payable to Con Edison Development. At the time of acquisition, $290 million was recorded as non-utility construction work in process, $22 million was recorded as other assets and $14 million was recorded as current liabilities. A part of the project commenced commercial operation in December 2017. At December 31, 2017 and 2016, net assets of the project were approximately $435 million and $388 million, respectively. Con Edison's equity interest in Panoche is consolidated in the financial statements.

Coram Wind

In December 2016, Con Edison Development acquired a 100 percent equity interest in Coram California Development, LP (Coram), which owns a 102 MW (AC) wind electric production project in California for $97 million, as to which $191 million was recorded as non-utility property, $78 million was recorded as an intangible asset, $8 million of restricted cash was recorded as other current assets, and $180 million was recorded as long term debt. In December 2017, an increase of $22 million was recorded to the intangible asset and a corresponding decrease was recorded to non-utility property. The intangible asset pertains to the value of the project's power purchase agreement, relative to current market rates, and is being amortized over the life of the agreement. The project commenced commercial operation in March 2012. At December 31, 2017 and 2016, net assets of the project were approximately $87 million and $96 million, respectively. Con Edison's equity interest in Coram is consolidated in the financial statements.

Dispositions

Pike County Light & Power Company (Pike)

In October 2015, O&R entered into an agreement to sell Pike to Corning Natural Gas Holding Corporation (Corning). In August 2016, the sale was completed. O&R received cash consideration of $15 million for the sale. O&R has agreed to provide transition services to Corning for operations and customer support for a period of up to 18 months subsequent to the sale. In addition, O&R will continue to purchase and sell to Pike electric and gas commodity for three years. Pike has an option to extend the commodity procurement service for up to an additional three years. At September 30, 2015, O&R recorded an impairment charge of $5 million ($3 million, net of taxes), representing the difference between the carrying amount of Pike’s assets and the estimated sales proceeds.

Con Edison Solutions' Retail Electric Supply Business

In July 2016, Con Edison Solutions entered into an agreement to sell the assets of its retail electric supply business (including retail contracts, related derivative instruments, information systems, and accounts receivable) to a subsidiary of Exelon Corporation (Exelon). In September 2016, the sale was completed for cash consideration of $235 million, subject to working capital adjustments. The sale resulted in a gain of $104 million ($56 million, net of taxes), inclusive of a $65 million ($42 million, net of taxes) gain on derivative instruments. The tax effect of the sale included $16 million ($10 million, net of federal tax) of state taxes related to a change in the apportionment of state income taxes. Con Edison Solutions provided transition services to the Exelon subsidiary for operations and customer support through January 2018 during a portion of which period certain guarantees or other credit support provided by Con Edison in connection with the retail electric supply business continued in effect. See Note H.

Upton 2

In May 2017, Con Edison Development sold Upton 2, a development stage solar electric production project, for $11 million to Vistra Asset Co. and recorded a $1 million gain on sale ($0.7 million, net of taxes). In addition, Con Edison Development agreed to perform the engineering, procurement and construction for the 180 MW (AC) project, which is expected to be substantially completed in 2018.