Basis Of Presentation	6 Months Ended
Jun. 30, 2011
Basis Of Presentation
Basis Of Presentation	1. Basis of Presentation The accompanying unaudited condensed consolidated financial statements include the accounts of Arch Coal, Inc. and its subsidiaries and controlled entities (the "Company"). The Company's primary business is the production of steam and metallurgical coal from surface and underground mines located throughout the United States, for sale to utility, industrial and export markets. On June 15, 2011, the Company acquired International Coal Group, Inc. ("ICG"), as described in Note 3, "Business Combinations". The Company operates 24 mining complexes in West Virginia, Kentucky, Maryland, Virginia, Illinois, Wyoming, Colorado and Utah. All subsidiaries (except as noted below) 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 month periods ended June 30, 2011 are not necessarily indicative of results to be expected for the year ending December 31, 2011. 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, 2010 included in the Company's Annual Report on Form 10-K filed with the U.S. Securities and Exchange Commission. The Company owns a 99% membership interest in a joint venture named Arch Western Resources, LLC ("Arch Western") which operates coal mines in Wyoming, Colorado and Utah. The Company also acts as the managing member of Arch Western.

1. Basis of Presentation

The accompanying unaudited condensed consolidated financial statements include the accounts of Arch Coal, Inc. and its subsidiaries and controlled entities (the "Company"). The Company's primary business is the production of steam and metallurgical coal from surface and underground mines located throughout the United States, for sale to utility, industrial and export markets. On June 15, 2011, the Company acquired International Coal Group, Inc. ("ICG"), as described in Note 3, "Business Combinations". The Company operates 24 mining complexes in West Virginia, Kentucky, Maryland, Virginia, Illinois, Wyoming, Colorado and Utah. All subsidiaries (except as noted below) 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 month periods ended June 30, 2011 are not necessarily indicative of results to be expected for the year ending December 31, 2011. 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, 2010 included in the Company's Annual Report on Form 10-K filed with the U.S. Securities and Exchange Commission.

The Company owns a 99% membership interest in a joint venture named Arch Western Resources, LLC ("Arch Western") which operates coal mines in Wyoming, Colorado and Utah. The Company also acts as the managing member of Arch Western.