Basis of Presentation	6 Months Ended
Jun. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements include the accounts of Arch Coal, Inc. ("Arch Coal") and its subsidiaries (the “Company”). Unless the context indicates otherwise, the terms “Arch” and the “Company” are used interchangeably in this Quarterly Report on Form 10-Q refer to both the Predecessor and Successor Company. The Company’s primary business is the production of thermal and metallurgical coal from surface and underground mines located throughout the United States, for sale to utility, industrial and steel producers both in the United States and around the world. The Company currently operates mining complexes in West Virginia, Kentucky, Virginia, Illinois, Wyoming and Colorado. All subsidiaries are wholly-owned. Intercompany transactions and accounts have been eliminated in consolidation. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States for interim financial reporting and U.S. Securities and Exchange Commission regulations. In the opinion of management, all adjustments, consisting of normal, recurring accruals considered necessary for a fair presentation, have been included. Results of operations for the three and six months ended June 30, 2017 are not necessarily indicative of results to be expected for the year ending December 31, 2017. These financial statements should be read in conjunction with the audited financial statements and related notes as of and for the year ended December 31, 2016 included in the Company’s Annual Report on Form 10-K filed with the U.S. Securities and Exchange Commission. On January 11, 2016 (the “Petition Date”), Arch Coal and substantially all of its wholly owned domestic subsidiaries (the “Filing Subsidiaries” and, together with Arch Coal, the “Debtors”; the Debtors, solely following the effective date of the Plan, the “Reorganized Debtors”) filed voluntary petitions for reorganization (collectively, the “Bankruptcy Petitions”) under Chapter 11 of Title 11 of the U.S. Code (the “Bankruptcy Code”) in the United States Bankruptcy Court for the Eastern District of Missouri (the “Court”). The Debtors’ Chapter 11 Cases (collectively, the “Chapter 11 Cases”) were jointly administered under the caption In re Arch Coal, Inc., et al. Case No. 16-40120 (lead case). During the Chapter 11 Cases, each Debtor operated its business as a “debtor in possession” under the jurisdiction of the Court and in accordance with the applicable provisions of the Bankruptcy Code and the orders of the Court. Upon emergence from bankruptcy on October 5, 2016, Arch Coal applied the provisions of fresh start accounting effective October 1, 2016 which resulted in Arch becoming a new entity for financial reporting purposes. Accordingly, the consolidated financial statements and accompanying footnotes on or after October 1, 2016 are not comparable to the consolidated financial statements prior to that date. References to “Successor” in the consolidated financial statements and footnotes are in reference to reporting dates on or after October 2, 2016; references to “Predecessor” in the consolidated financial statements and footnotes are in reference to reporting dates through October 1, 2016 which includes the impact of the Plan provisions and the application of fresh start accounting.

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements include the accounts of Arch Coal, Inc. ("Arch Coal") and its subsidiaries (the “Company”). Unless the context indicates otherwise, the terms “Arch” and the “Company” are used interchangeably in this Quarterly Report on Form 10-Q refer to both the Predecessor and Successor Company. The Company’s primary business is the production of thermal and metallurgical coal from surface and underground mines located throughout the United States, for sale to utility, industrial and steel producers both in the United States and around the world. The Company currently operates mining complexes in West Virginia, Kentucky, Virginia, Illinois, Wyoming and Colorado. All subsidiaries are wholly-owned. Intercompany transactions and accounts have been eliminated in consolidation.

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States for interim financial reporting and U.S. Securities and Exchange Commission regulations. In the opinion of management, all adjustments, consisting of normal, recurring accruals considered necessary for a fair presentation, have been included. Results of operations for the three and six months ended June 30, 2017 are not necessarily indicative of results to be expected for the year ending December 31, 2017. These financial statements should be read in conjunction with the audited financial statements and related notes as of and for the year ended December 31, 2016 included in the Company’s Annual Report on Form 10-K filed with the U.S. Securities and Exchange Commission.

On January 11, 2016 (the “Petition Date”), Arch Coal and substantially all of its wholly owned domestic subsidiaries (the “Filing Subsidiaries” and, together with Arch Coal, the “Debtors”; the Debtors, solely following the effective date of the Plan, the “Reorganized Debtors”) filed voluntary petitions for reorganization (collectively, the “Bankruptcy Petitions”) under Chapter 11 of Title 11 of the U.S. Code (the “Bankruptcy Code”) in the United States Bankruptcy Court for the Eastern District of Missouri (the “Court”). The Debtors’ Chapter 11 Cases (collectively, the “Chapter 11 Cases”) were jointly administered under the caption In re Arch Coal, Inc., et al. Case No. 16-40120 (lead case). During the Chapter 11 Cases, each Debtor operated its business as a “debtor in possession” under the jurisdiction of the Court and in accordance with the applicable provisions of the Bankruptcy Code and the orders of the Court.

Upon emergence from bankruptcy on October 5, 2016, Arch Coal applied the provisions of fresh start accounting effective October 1, 2016 which resulted in Arch becoming a new entity for financial reporting purposes. Accordingly, the consolidated financial statements and accompanying footnotes on or after October 1, 2016 are not comparable to the consolidated financial statements prior to that date. References to “Successor” in the consolidated financial statements and footnotes are in reference to reporting dates on or after October 2, 2016; references to “Predecessor” in the consolidated financial statements and footnotes are in reference to reporting dates through October 1, 2016 which includes the impact of the Plan provisions and the application of fresh start accounting.