Separation from CNX Resources Corporation	12 Months Ended
Dec. 31, 2017
Business Combinations [Abstract]
Separation from CNX Resources Corporation	: In December 2016, CNX announced its intent to separate into two independent, publicly-traded companies - an independently traded coal company and an independently traded oil and natural gas exploration and production company focused on Appalachian area natural gas and liquids activities, including production, gathering, processing and acquisition of natural gas properties in the Appalachian Basin. In anticipation of the separation, CONSOL Energy was originally formed as CONSOL Mining Corporation in Delaware on June 21, 2017 to hold all of ParentCo’s Coal Business, including its interest in the Pennsylvania Mining Complex, and certain related coal assets, including ParentCo’s ownership interest in CNX Coal Resources LP, which owns a 25% undivided interest stake in PAMC, the CONSOL Marine Terminal and undeveloped coal reserves (Greenfield Reserves) located in the Northern Appalachian, Central Appalachian and Illinois basins and certain related coal assets and liabilities (the Coal Business). The Registration Statement on Form 10 (as amended) filed by the Company with the SEC describes the Company and the assets and liabilities that comprise the Coal Business that it now owns after completion of the separation and distribution. The Form 10 was declared effective by the SEC on November 3, 2017. The separation occurred on November 28, 2017, through the pro rata distribution by ParentCo of all of the outstanding common stock of CONSOL Mining Corporation to ParentCo’s shareholders. Following the separation and distribution, ParentCo continues to own the Gas Business. In connection with the separation, CONSOL Mining Corporation changed its name to CONSOL Energy Inc. and ParentCo changed its name to CNX Resources Corporation. In addition, CNX Coal Resources LP changed its name to CONSOL Coal Resources LP and its ticker to CCR. The separation was subject to a number of conditions, including, but not limited to: final approval by ParentCo’s Board of Directors; the continuing validity of the private letter ruling from the Internal Revenue Service regarding certain U.S. federal income tax matters relating to the transaction; receipt of an opinion of legal counsel regarding the qualification of the distribution, together with certain related transactions, as a transaction that is generally tax-free for U.S. federal income tax purposes; and the SEC declaring effective a Registration Statement on Form 10, as amended. The registration statement on Form 10 was declared effective on November 3, 2017. In connection with the separation and distribution, CONSOL Mining Corporation and ParentCo entered into a separation and distribution agreement on November 28, 2017 that identified the assets of the Coal Business that were transferred to CONSOL Mining Corporation, the liabilities that were assumed and the contracts that were transferred to each of CONSOL Mining Corporation and ParentCo as part of the separation into two companies. The agreement also implemented the legal and structural separation between the two companies. ParentCo and the Company also entered into additional ancillary agreements that govern the relationship between the two companies after the completion of the separation and distribution, and allocate between GasCo and the Company various assets, liabilities and obligations, including, among other things, employee benefits, environmental liabilities, intellectual property, and tax-related assets and liabilities. These additional agreements included a tax matters agreement, employee matters agreement, transition services agreement and certain agreements related to intellectual property.

In December 2016, CNX announced its intent to separate into two independent, publicly-traded companies - an independently traded coal company and an independently traded oil and natural gas exploration and production company focused on Appalachian area natural gas and liquids activities, including production, gathering, processing and acquisition of natural gas properties in the Appalachian Basin.

In anticipation of the separation, CONSOL Energy was originally formed as CONSOL Mining Corporation in Delaware on June 21, 2017 to hold all of ParentCo’s Coal Business, including its interest in the Pennsylvania Mining Complex, and certain related coal assets, including ParentCo’s ownership interest in CNX Coal Resources LP, which owns a 25% undivided interest stake in PAMC, the CONSOL Marine Terminal and undeveloped coal reserves (Greenfield Reserves) located in the Northern Appalachian, Central Appalachian and Illinois basins and certain related coal assets and liabilities (the Coal Business). The Registration Statement on Form 10 (as amended) filed by the Company with the SEC describes the Company and the assets and liabilities that comprise the Coal Business that it now owns after completion of the separation and distribution. The Form 10 was declared effective by the SEC on November 3, 2017.

The separation occurred on November 28, 2017, through the pro rata distribution by ParentCo of all of the outstanding common stock of CONSOL Mining Corporation to ParentCo’s shareholders. Following the separation and distribution, ParentCo continues to own the Gas Business. In connection with the separation, CONSOL Mining Corporation changed its name to CONSOL Energy Inc. and ParentCo changed its name to CNX Resources Corporation. In addition, CNX Coal Resources LP changed its name to CONSOL Coal Resources LP and its ticker to CCR.

The separation was subject to a number of conditions, including, but not limited to: final approval by ParentCo’s Board of Directors; the continuing validity of the private letter ruling from the Internal Revenue Service regarding certain U.S. federal income tax matters relating to the transaction; receipt of an opinion of legal counsel regarding the qualification of the distribution, together with certain related transactions, as a transaction that is generally tax-free for U.S. federal income tax purposes; and the SEC declaring effective a Registration Statement on Form 10, as amended. The registration statement on Form 10 was declared effective on November 3, 2017.

In connection with the separation and distribution, CONSOL Mining Corporation and ParentCo entered into a separation and distribution agreement on November 28, 2017 that identified the assets of the Coal Business that were transferred to CONSOL Mining Corporation, the liabilities that were assumed and the contracts that were transferred to each of CONSOL Mining Corporation and ParentCo as part of the separation into two companies. The agreement also implemented the legal and structural separation between the two companies. ParentCo and the Company also entered into additional ancillary agreements that govern the relationship between the two companies after the completion of the separation and distribution, and allocate between GasCo and the Company various assets, liabilities and obligations, including, among other things, employee benefits, environmental liabilities, intellectual property, and tax-related assets and liabilities. These additional agreements included a tax matters agreement, employee matters agreement, transition services agreement and certain agreements related to intellectual property.