10-K/A

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, DC 20549

Form 10-K/A
(Amendment No. 1)

ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d)
OF THE SECURITIES EXCHANGE ACT OF 1934

For the fiscal year ended December 31, 2011

Commission file number: 1-13105

Arch Coal, Inc.
(Exact name of registrant as specified in its charter)

Delaware (State or other jurisdiction of incorporation or organization)	43-0921172 (I.R.S. Employer Identification Number)
One CityPlace Drive, Ste. 300, St. Louis, Missouri (Address of principal executive offices)	63141 (Zip code)

Registrant's telephone number, including area code: (314) 994-2700

Securities registered pursuant to Section 12(b) of the Act:

Title of Each Class	Name of Each Exchange on Which Registered
Common Stock, $.01 par value	New York Stock Exchange Chicago Stock Exchange

Securities registered pursuant to Section 12(g) of the Act: None

          Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes ý    No o

          Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes o    No ý

          Indicate by check mark whether the registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ý    No o

          Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such filed). Yes ý    No o

          Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of registrant's knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K. o

          Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of "large accelerated filer," "accelerated filer" and "smaller reporting company" in Rule 12b-2 of the Exchange Act. (Check one):

Large accelerated filer ý Accelerated filer o Non-accelerated filer o
(Do not check if a smaller reporting company) Smaller reporting company o

          Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes o    No ý

          The aggregate market value of the voting stock held by non-affiliates of the registrant (excluding outstanding shares beneficially owned by directors, officers and treasury shares) as of June 30, 2011 was approximately $5.6 billion.

          On February 15, 2012, 213,292,678 shares of the company's common stock, par value $0.01 per share, were outstanding.

          Portions of the registrant's definitive proxy statement for the annual stockholders' meeting to be held on April 26, 2012 are incorporated by reference into Part III of this Form 10-K.

EXPLANATORY NOTE

        Arch Coal, Inc. (the "Company") is filing this Amendment No. 1. (this "Amendment") to its Annual Report on Form 10-K for the fiscal year ended December 31, 2011, filed with the Securities and Exchange Commission on February 29, 2012 (the "Original Report"), for the sole purpose of correcting an error in Note 26 to the audited consolidated financial statements of the Company contained in the Original Report. The word "unaudited" inadvertently was used in the second sentence of the first paragraph in Note 26 to the audited consolidated financial statements of the Company contained in the Original Report, although the condensed consolidating financial information set forth in Note 26 was audited by the Company's independent registered public accounting firm. The Company is filing this Amendment solely to amend Note 26 to clarify that the condensed consolidating financial information set forth in Note 26 is audited. This Amendment amends and restates in their entirety Item 8 of Part II and Item 15 of Part IV of the Original Report.

        No other amendments, modifications, updates or changes are being made to the Original Report other than as described above. This Amendment speaks as of the date of the filing of the Original Report. The Company has not taken into account any other events occurring after the filing of the Original Report which might have affected any disclosures in the Original Report, nor has the Company amended, modified, updated or otherwise changed any disclosures to reflect any subsequent events.

PART II

ITEM 8.    FINANCIAL STATEMENTS AND SUPPLEMENTARY DATA.

        The consolidated financial statements and consolidated financial statement schedule of Arch Coal, Inc. and subsidiaries are included in this Annual Report on Form 10-K beginning on page F-1.

PART IV

ITEM 15.    EXHIBITS AND FINANCIAL STATEMENT SCHEDULES.

Financial Statements

        Reference is made to the index set forth on page F-1 of this report.

Financial Statement Schedules

        Financial statement schedules listed under SEC rules but not included in this report are omitted because they are not applicable or the required information is provided in the notes to our consolidated financial statements.

Exhibits

        Reference is made to the Exhibit Index beginning on page 3 of this report.

1

Signatures

        Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Arch Coal, Inc.

Steven F. Leer
Chairman and Chief Executive Officer
April 23, 2012

2

Exhibit Index

Exhibit		Description
	2.1	Purchase and Sale Agreement, dated as of December 31, 2005, by and between Arch Coal, Inc. and Magnum Coal Company (incorporated herein by reference to Exhibit 10.1 to the registrant's Current Report on Form 8-K filed on January 6, 2006).
	2.2	Amendment No. 1 to the Purchase and Sale Agreement, dated as of February 7, 2006, by and between Arch Coal, Inc. and Magnum Coal Company (incorporated by reference to Exhibit 2.1 to the registrant's Annual Report on Form 10-K for the year ended December 31, 2005).
	2.3	Amendment No. 2 to the Purchase and Sale Agreement, dated as of April 27, 2006, by and between Arch Coal, Inc. and Magnum Coal Company (incorporated herein by reference to Exhibit 2.1 to the registrant's Quarterly Report on Form 10-Q for the period ended June 30, 2006).
	2.4	Amendment No. 3 to the Purchase and Sale Agreement, dated as of August 29, 2007, by and between Arch Coal, Inc. and Magnum Coal Company (incorporated herein by reference to Exhibit 2.1 to the registrant's Quarterly Report on Form 10-Q for the period ended September 30, 2007).
	2.5	Agreement, dated as of March 27, 2008, by and between Arch Coal, Inc. and Magnum Coal Company (incorporated herein by reference to Exhibit 2.1 to the registrant's Quarterly Report on Form 10-Q for the period ended March 31, 2008).
	2.6	Amendment No. 1 to Agreement, dated as of February 5, 2009, by and between Arch Coal, Inc. and Magnum Coal Company (incorporated herein by reference to Exhibit 2.6 to the registrant's Annual Report on Form 10-K for the year ended December 31, 2008).
	2.7	Agreement and Plan of Merger, dated as of May 2, 2011, by and among Arch Coal, Inc., Atlas Acquisition Corp. and International Coal Group, Inc. (incorporated herein by reference to Exhibit 2.1 to the registrant's Current Report on Form 8-K filed on May 3, 2011).
	+2.8	Amendment to Agreement and Plan of Merger, dated as of May 26, 2011 among Arch Coal, Inc., Atlas Acquisition Corp. and International Coal Group, Inc.
	3.1	Restated Certificate of Incorporation of Arch Coal, Inc. (incorporated herein by reference to Exhibit 3.1 to the registrant's Current Report on Form 8-K filed on May 5, 2006).
	3.2	Arch Coal, Inc. Bylaws, as amended effective as of December 5, 2008 (incorporated herein by reference to Exhibit 3.1 to the registrant's Current Report on Form 8-K filed on December 10, 2008).
	4.1	Indenture, dated as of June 25, 2003, by and among Arch Western Finance, LLC, Arch Coal, Inc., Arch Western Resources, LLC, Arch of Wyoming, LLC, Mountain Coal Company, L.L.C., Thunder Basin Coal Company, L.L.C. and The Bank of New York, as trustee (incorporated herein by reference to Exhibit 4.1 to the Registration Statement on Form S-4 (Reg. No. 333-107569) filed by Arch Western Finance, LLC on August 1, 2003).
	4.2	First Supplemental Indenture dated October 22, 2004 among Arch Western Finance, LLC, Arch Western Resources, LLC, Arch of Wyoming, LLC, Arch Western Bituminous Group, LLC, Mountain Coal Company, L.L.C., Thunder Basin Coal Company, L.L.C., Triton Coal Company, LLC, and The Bank of New York, as trustee (incorporated herein by reference to Exhibit 4.4 to the registrant's Current Report on Form 8-K filed on October 28, 2004).
	4.3	Indenture, dated as of July 31, 2009 by and among Arch Coal, Inc., the subsidiary guarantors named therein and U.S. Bank National Association, as trustee (incorporated herein by reference to Exhibit 4.1 to the registrant's Current Report on Form 8-K filed on July 31, 2009).
	4.4	First Supplemental Indenture, dated as of February 8, 2010, by and among Arch Coal, Inc., the subsidiary guarantors named therein and U.S. Bank National Association, as trustee (incorporated herein by reference to Exhibit 4.1 to the registrant's Quarterly Report on Form 10-Q for the period ended March 31, 2010).

3

Exhibit		Description
	4.5	Second Supplemental Indenture, dated as of March 12, 2010, by and among Arch Coal, Inc., the subsidiary guarantors named therein and U.S. Bank National Association, as trustee (incorporated herein by reference to Exhibit 4.5 to the registrant's Registration Statement on Form S-4 filed on April 7, 2010).
	4.6	Third Supplemental Indenture, dated as of May 7, 2010, by and among Arch Coal, Inc., the subsidiary guarantors named therein and U.S. Bank National Association, as trustee (incorporated herein by reference to Exhibit 4.3 to the registrant's Quarterly Report on Form 10-Q for the period ended March 31, 2010).
	4.7	Fourth Supplemental Indenture, dated December 16, 2010, by and among Arch Coal West, LLC, Arch Coal, Inc., the subsidiary guarantors named therein and U.S. Bank National Association, as trustee (incorporated by reference to Exhibit 4.7 to the registrant's Annual Report on Form 10-K for the period ended December 31, 2010).
	+4.8	Fifth Supplemental Indenture, dated as of June 24, 2011, by and among Arch Coal, Inc., the subsidiary guarantors named therein and U.S. Bank National Association, as trustee.
	+4.9	Sixth Supplemental Indenture, dated as of October 7, 2011, by and among Arch Coal, Inc., the subsidiary guarantors named therein and U.S. Bank National Association, as trustee.
	4.10	Indenture, dated as of August 9, 2010, by and between Arch Coal, Inc. and U.S. Bank National Association, as trustee (incorporated herein by reference to Exhibit 4.1 to the registrant's Current Report on Form 8-K filed on August 9, 2010).
	4.11	First Supplemental Indenture, dated as of August 9, 2010, by and among Arch Coal, Inc., the subsidiary guarantors named therein, and U.S. Bank National Association, as trustee (incorporated herein by reference to Exhibit 4.2 to the registrant's Current Report on Form 8-K filed on August 9, 2010).
	4.12	Second Supplemental Indenture, dated as of December 16, 2010, by and among Arch Coal West, LLC, Arch Coal, Inc., the subsidiary guarantors named therein and U.S. Bank National Association, as trustee (incorporated herein by reference to Exhibit 4.7 to the registrant's Annual Report on Form 10-K for the period ended December 31, 2010).
	+4.13	Third Supplemental Indenture, dated as of June 24, 2011, by and among Arch Coal, Inc., the subsidiary guarantors named therein and U.S. Bank National Association, as trustee.
	+4.14	Fourth Supplemental Indenture, dated as of October 7, 2011, by and among Arch Coal, Inc., the subsidiary guarantors named therein and U.S. Bank National Association, as trustee.
	4.15	Indenture, dated as of June 14, 2011, by and among Arch Coal, Inc., the subsidiary guarantors named therein and UMB Bank National Association, as trustee (incorporated herein by reference to Exhibit 4.1 to the registrant's Current Report on Form 8-K filed on June 14, 2011).
	+4.16	First Supplemental Indenture, dated as of July 5, 2011, by and among Arch Coal, Inc., the subsidiary guarantors named therein and UMB Bank National Association, as trustee.
	+4.17	Second Supplemental Indenture, dated as of October 7, 2011, by and among Arch Coal, Inc., the subsidiary guarantors named therein and UMB Bank National Association, as trustee.
	4.18	Registration Rights Agreement, dated as of June 14, 2011, by and among Arch Coal, Inc., the subsidiary guarantors named therein, Morgan Stanley & Co. LLC, PNC Capital Markets LLC, Merrill Lynch, Pierce, Fenner & Smith Incorporated, RBS Securities Inc. and Citigroup Global Markets Inc. as representatives of the initial purchasers named therein (incorporated herein by reference to Exhibit 4.4 to the registrant's Current Report on Form 8-K filed on June 14, 2011).
	10.1	Amended and Restated Credit Agreement, dated as of June 14, 2011, by and among the Company, the lenders party thereto, PNC Bank, National Association, as administrative agent and Bank of America, N.A., The Royal Bank of Scotland PLC and Citibank, N.A., as co-documentation agents (incorporated herein by reference to Exhibit 10.1 to the Current Report on Form 8-K filed by the registrant on June 17, 2011).

4

Exhibit		Description
	10.2*	Employment Agreement, dated November 10, 2006, between Arch Coal, Inc. and Steven F. Leer (incorporated by reference to Exhibit 10.1 to the Current Report on Form 8-K filed by the registrant on November 16, 2006).
	10.3*	Form of Employment Agreement for Executive Officers of Arch Coal, Inc. (other than Steven F. Leer) (for employment agreements entered into up to 2011) (incorporated by reference to Exhibit 10.2 to the Current Report on Form 8-K filed by the registrant on November 16, 2006).
	+10.4*	Form of Employment Agreement for Executive Officers of Arch Coal, Inc. (other than Steven F. Leer) (for employment agreements entered into beginning in 2011).
	10.5	Coal Lease Agreement dated as of March 31, 1992, among Allegheny Land Company, as lessee, and UAC and Phoenix Coal Corporation, as lessors, and related guarantee (incorporated herein by reference to the Current Report on Form 8-K filed by Ashland Coal, Inc. on April 6, 1992).
	10.6	Federal Coal Lease dated as of June 24, 1993 between the U.S. Department of the Interior and Southern Utah Fuel Company (incorporated herein by reference to Exhibit 10.17 to the registrant's Annual Report on Form 10-K for the year ended December 31, 1998).
	10.7	Federal Coal Lease between the U.S. Department of the Interior and Utah Fuel Company (incorporated herein by reference to Exhibit 10.18 to the registrant's Annual Report on Form 10-K for the year ended December 31, 1998).
	10.8	Federal Coal Lease dated as of July 19, 1997 between the U.S. Department of the Interior and Canyon Fuel Company, LLC (incorporated herein by reference to Exhibit 10.19 to the registrant's Annual Report on Form 10-K for the year ended December 31, 1998).
	10.9	Federal Coal Lease dated as of January 24, 1996 between the U.S. Department of the Interior and the Thunder Basin Coal Company (incorporated herein by reference to Exhibit 10.20 to the registrant's Annual Report on Form 10-K for the year ended December 31, 1998).
	10.10	Federal Coal Lease Readjustment dated as of November 1, 1967 between the U.S. Department of the Interior and the Thunder Basin Coal Company (incorporated herein by reference to Exhibit 10.21 to the registrant's Annual Report on Form 10-K for the year ended December 31, 1998).
	10.11	Federal Coal Lease effective as of May 1, 1995 between the U.S. Department of the Interior and Mountain Coal Company (incorporated herein by reference to Exhibit 10.22 to the registrant's Annual Report on Form 10-K for the year ended December 31, 1998).
	10.12	Federal Coal Lease dated as of January 1, 1999 between the Department of the Interior and Ark Land Company (incorporated herein by reference to Exhibit 10.23 to the registrant's Annual Report on Form 10-K for the year ended December 31, 1998).
	10.13	Federal Coal Lease dated as of October 1, 1999 between the U.S. Department of the Interior and Canyon Fuel Company, LLC (incorporated herein by reference to Exhibit 10 to the registrant's Quarterly Report on Form 10-Q for the quarter ended September 30, 1999).
	10.14	Federal Coal Lease effective as of March 1, 2005 by and between the United States of America and Ark Land LT, Inc. covering the tract of land known as "Little Thunder" in Campbell County, Wyoming (incorporated by reference to Exhibit 99.1 to the Current Report on Form 8-K filed by the registrant on February 10, 2005).
	10.15	Modified Coal Lease (WYW71692) executed January 1, 2003 by and between the United States of America, through the Bureau of Land Management, as lessor, and Triton Coal Company, LLC, as lessee, covering a tract of land known as "North Rochelle" in Campbell County, Wyoming (incorporated by reference to Exhibit 10.24 to the registrant's Annual Report on Form 10-K for the year ended December 31, 2004).
	10.16	Coal Lease (WYW127221) executed January 1, 1998 by and between the United States of America, through the Bureau of Land Management, as lessor, and Triton Coal Company, LLC, as lessee, covering a tract of land known as "North Roundup" in Campbell County, Wyoming (incorporated by reference to Exhibit 10.24 to the registrant's Annual Report on Form 10-K for the year ended December 31, 2004).

5

Exhibit		Description
	10.17	State Coal Lease executed October 1, 2004 by and between The State of Utah, Thru School & Institutional Trust Lands Admin, as lessor, and Ark Land Company and Arch Coal, Inc., as lessees, covering a tract of land located in Seiever County, Utah (incorporated by reference to Exhibit 10.20 to the registrant's Annual Report on Form 10-K for the year ended December 31, 2006).
	10.18	State Coal Lease executed September 1, 2000 by and between The State of Utah, Thru School & Institutional Trust Lands Admin, as lessor, and Canyon Fuel Company, LLC, as lessee, for lands located in Carbon County, Utah (incorporated by reference to Exhibit 10.21 to the registrant's Annual Report on Form 10-K for the year ended December 31, 2006).
	10.19	Federal Coal Lease executed September 1, 1996 by and between the Bureau of Land Management, as lessor, and Canyon Fuel Company, LLC, as lessee, covering a tract of land known as "The North Lease" in Carbon County, Utah (incorporated by reference to Exhibit 10.22 to the registrant's Annual Report on Form 10-K for the year ended December 31, 2006).
	10.20	State Coal Lease executed January 18, 2008 by and between The State of Utah, Thru School & Institutional Trust Lands Admin, as lessor, and Ark Land Company, as lessee, for lands located in Emery County, Utah (incorporated by reference to Exhibit 10.21 to the registrant's Annual Report on Form 10-K for the year ended December 31, 2008).
	10.21	Form of Indemnity Agreement between Arch Coal, Inc. and Indemnitee (as defined therein) (incorporated herein by reference to Exhibit 10.15 to the Registration Statement on Form S-4 (Registration No. 333-28149) filed by the registrant on May 30, 1997).
	10.22*	Arch Coal, Inc. Incentive Compensation Plan For Executive Officers (incorporated herein by reference to Appendix B to the proxy statement on Schedule 14A filed by the registrant on March 22, 2010).
	10.23*	Arch Coal, Inc. Deferred Compensation Plan (incorporated herein by reference to Exhibit 10.3 to the registrant's Current Report on Form 8-K filed on December 11, 2008).
	10.24*	Arch Coal, Inc. 1997 Stock Incentive Plan (as amended and restated on October 21, 2010) (incorporated herein by reference to Exhibit 10.1 to the registrant's Current Report on Form 8-K filed on October 27, 2010).
	10.25*	Arch Mineral Corporation 1996 ERISA Forfeiture Plan (incorporated herein by reference to Exhibit 10.20 to the Registration Statement on Form S-4 (Registration No. 333-28149) filed by the registrant on May 30, 1997).
	10.26*	Arch Coal, Inc. Outside Directors' Deferred Compensation Plan (incorporated herein by reference to Exhibit 10.4 of the registrant's Current Report on Form 8-K filed on December 11, 2008).
	10.27*	Arch Coal, Inc. Supplemental Retirement Plan (as amended on December 5, 2008) (incorporated herein by reference to Exhibit 10.2 to the registrant's Current Report on Form 8-K filed on December 11, 2008).
	10.28*	Form of Restricted Stock Unit Contract (incorporated herein by reference to Exhibit 10.5 to the registrant's Current Report on Form 8-K filed on February 24, 2006).
	10.29*	Form of Non-Qualified Stock Option Agreement (for stock options granted prior to February 21, 2008) (incorporated herein by reference to Exhibit 10.35 to the registrant's Annual Report on Form 10-K for the year ended December 31, 2006).
	10.30*	Form of 2008 Restricted Stock Unit Contract for Messrs. Leer and Eaves (incorporated herein by reference to Exhibit 10.3 to the registrant's Current Report on Form 8-K filed on February 27, 2008).
	10.31*	Form of 2008 Non-Qualified Stock Option Agreement for Messrs. Leer and Eaves (incorporated herein by reference to Exhibit 10.4 to the registrant's Current Report on Form 8-K filed on February 27, 2008).
	10.32*	Form of Non-Qualified Stock Option Agreement (for stock options granted on or after February 21, 2008) (incorporated herein by reference to Exhibit 10.5 to the registrant's Current Report on Form 8-K filed on February 27, 2008).

6

Exhibit		Description
	10.33*	Form of Performance Unit Contract (incorporated herein by reference to Exhibit 10.2 to the registrant's Current Report on Form 8-K filed on February 23, 2009).
	10.34*	Form of Director Indemnity Agreement (incorporated herein by reference to Exhibit 10.40 to the registrant's Annual Report on Form 10-K for the period ended December 31, 2010).
	10.35	Amended and Restated Receivables Purchase Agreement, dated as of February 24, 2020, among Arch Receivable Company, LLC, Arch Coal Sales Company, Inc., Market Street Funding LLC, as issuer, the financial institutions from time to time party thereto, as LC Participants, and PNC Bank, National Association, as Administrator on behalf of the Purchasers and as LC Bank (incorporated herein by reference to Exhibit 10.2 to the registrant's Quarterly Report on Form 10-Q for the period ended March 31, 2010).
	10.36	First Amendment to Amended and Restated Receivables Purchase Agreement, dated January 31, 2011, among Arch Receivable Company, LLC, Arch Coal Sales Company, Inc. and the other parties thereto (incorporated by reference to Exhibit 10.41 to the registrant's Annual Report on Form 10-K for the period ended December 31, 2010).
	10.37	Second Amendment to Amended and Restated Receivables Purchase Agreement dated June 15, 2011 (incorporated by reference to Exhibit 10.5 to the registrant's Quarterly Report on Form 10-Q for the period ended June 30, 2011).
	+10.38	Third Amendment to Amended and Restated Receivables Purchase Agreement dated November 21, 2011, among Arch Receivable Company, LLC, Arch Coal Sales Company, Inc. and the other parties thereto.
	+10.39	Fourth Amendment to Amended and Restated Receivables Purchase Agreement dated December 13, 2011, among Arch Receivable Company, LLC, Arch Coal Sales Company, Inc. and the other parties thereto.
	+12.1	Computation of ratio of earnings to combined fixed charges and preference dividends.
	+21.1	Subsidiaries of the registrant.
	23.1	Consent of Ernst & Young LLP.
	+23.2	Consent of Weir International, Inc.
	+24.1	Power of Attorney.
	31.1	Rule 13a-14(a)/15d-14(a) Certification of Steven F. Leer.
	31.2	Rule 13a-14(a)/15d-14(a) Certification of John T. Drexler.
	32.1	Section 1350 Certification of Steven F. Leer.
	32.2	Section 1350 Certification of John T. Drexler.
	+95	Mine Safety Disclosure Exhibit.
	101	Interactive Data File (Form 10-K for the year ended December 31, 2011 furnished in XBRL).

*

Denotes management contract or compensatory plan arrangements.

+

Previously filed as an exhibit to Arch Coal, Inc.'s Annual Report on Form 10-K for the fiscal year ended December 31, 2011, as filed on February 29, 2012.

7

FINANCIAL STATEMENTS AND SUPPLEMENTARY DATA

        The consolidated financial statements of Arch Coal, Inc. and subsidiaries and reports of independent registered public accounting firm follow.

Index to Consolidated Financial Statements

Reports of Independent Registered Public Accounting Firm	F-2
Report of Management and Management's Report on Internal Control over Financial Reporting	F-4
Consolidated Statements of Income for the Years Ended December 31, 2011, 2010 and 2009	F-5
Consolidated Balance Sheets at December 31, 2011 and 2010	F-6
Consolidated Statements of Stockholders' Equity for the Years Ended December 31, 2011, 2010 and 2009	F-7
Consolidated Statements of Cash Flows for the Years Ended December 31, 2011, 2010 and 2009	F-8
Notes to Consolidated Financial Statements	F-9
Financial Statement Schedules	F-55

F-1

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

The Board of Directors and Shareholders of Arch Coal, Inc.

We have audited the accompanying consolidated balance sheets of Arch Coal, Inc. (the Company) as of December 31, 2011 and 2010, and the related consolidated statements of income, stockholders' equity, and cash flows for each of the three years in the period ended December 31, 2011. Our audits also included the financial statement schedule listed in the Index at Item 15. These financial statements and schedule are the responsibility of the Company's management. Our responsibility is to express an opinion on these financial statements and schedule based on our audits.

We conducted our audits in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement. An audit includes examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements. An audit also includes assessing the accounting principles used and significant estimates made by management, as well as evaluating the overall financial statement presentation. We believe that our audits provide a reasonable basis for our opinion.

In our opinion, the financial statements referred to above present fairly, in all material respects, the consolidated financial position of Arch Coal, Inc. at December 31, 2011 and 2010, and the consolidated results of its operations and its cash flows for each of the three years in the period ended December 31, 2011, in conformity with U.S. generally accepted accounting principles. Also, in our opinion, the related financial statement schedule, when considered in relation to the basic financial statements taken as a whole, presents fairly, in all material respects, the information set forth therein.

We also have audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States), Arch Coal, Inc.'s internal control over financial reporting as of December 31, 2011, based on criteria established in Internal Control — Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission, and our report dated February 29, 2012, expressed an unqualified opinion thereon.

St. Louis, Missouri
February 29, 2012

F-2

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

The Board of Directors and Shareholders of Arch Coal, Inc.

We have audited Arch Coal, Inc.'s (the Company's) internal control over financial reporting as of December 31, 2011, based on criteria established in Internal Control — Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission (the COSO criteria). The Company's management is responsible for maintaining effective internal control over financial reporting and for its assessment of the effectiveness of internal control over financial reporting included in the accompanying Management's Report on Internal Control Over Financial Reporting. Our responsibility is to express an opinion on the company's internal control over financial reporting based on our audit.

We conducted our audit in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audit to obtain reasonable assurance about whether effective internal control over financial reporting was maintained in all material respects. Our audit included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, testing and evaluating the design and operating effectiveness of internal control based on the assessed risk, and performing such other procedures as we considered necessary in the circumstances. We believe that our audit provides a reasonable basis for our opinion.

A company's internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company's internal control over financial reporting includes those policies and procedures that (1) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (2) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (3) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use or disposition of the company's assets that could have a material effect on the financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

As indicated in the accompanying Report of Management and Management's Report on Internal Control Over Financial Reporting, management's assessment of and conclusion on the effectiveness of internal control over financial reporting did not include the internal controls of International Coal Group, Inc. which is included in the 2011 consolidated financial statements of Arch Coal, Inc. and constituted $3.8 billion and $3.1 billion of total and net assets, respectively, as of December 31, 2011 and $606.9 million and $14.6 million of revenues and net income, respectively, for the year then ended. Our audit of internal control over financial reporting of Arch Coal, Inc. also did not include an evaluation of the internal control over financial reporting of International Coal Group, Inc.

In our opinion, Arch Coal, Inc. maintained, in all material respects, effective internal control over financial reporting as of December 31, 2011, based on the COSO criteria.

We also have audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States), the consolidated balance sheets of Arch Coal, Inc. as of December 31, 2011 and 2010, and the related consolidated statements of income, stockholders' equity, and cash flows for each of the three years in the period ended December 31, 2011, and our report dated February 29, 2011, expressed an unqualified opinion thereon.

St. Louis, Missouri
February 29, 2012

F-3

REPORT OF MANAGEMENT

        The management of Arch Coal, Inc. (the "Company") is responsible for the preparation of the consolidated financial statements and related financial information in this annual report. The financial statements are prepared in accordance with accounting principles generally accepted in the United States and necessarily include some amounts that are based on management's informed estimates and judgments, with appropriate consideration given to materiality.

        The Company maintains a system of internal accounting controls designed to provide reasonable assurance that financial records are reliable for purposes of preparing financial statements and that assets are properly accounted for and safeguarded. The concept of reasonable assurance is based on the recognition that the cost of a system of internal accounting controls should not exceed the value of the benefits derived. The Company has a professional staff of internal auditors who monitor compliance with and assess the effectiveness of the system of internal accounting controls.

        The Audit Committee of the Board of Directors, comprised of independent directors, meets regularly with management, the internal auditors, and the independent auditors to discuss matters relating to financial reporting, internal accounting control, and the nature, extent and results of the audit effort. The independent auditors and internal auditors have full and free access to the Audit Committee, with and without management present.

MANAGEMENT'S REPORT ON INTERNAL CONTROL OVER FINANCIAL REPORTING

        The management of Arch Coal, Inc. (the "Company") is responsible for establishing and maintaining adequate internal control over financial reporting, as defined in Securities Exchange Act Rule 13a-15(f). Under the supervision and with the participation of the Company's management, including its principal executive officer and principal financial officer, the Company conducted an evaluation of the effectiveness of its internal control over financial reporting based on the criteria set forth in Internal Control — Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission. Based on its evaluation, management concluded that the Company's internal control over financial reporting is effective as of December 31, 2011. On June 15, 2011, the Company acquired International Coal Group, Inc. (ICG), whose total assets and revenues constitute approximately 14% and 37%, respectively, of the amounts reflected in the accompanying consolidated financial statements for the year ended December 31, 2011. As permitted by the guidance the SEC, we have excluded ICG from our annual assessment of the effectiveness of internal control over financial reporting for the year ended December 31, 2011, the year of acquisition.

        The Company's independent registered public accounting firm, Ernst & Young LLP, has issued an audit report on the Company's internal control over financial reporting.

Steven F. Leer Chairman and Chief Executive Officer	John T. Drexler Senior Vice President and Chief Financial Officer

F-4

CONSOLIDATED STATEMENTS OF INCOME

	Year Ended December 31
	2011			2010			2009
	(In thousands, except per share data)
REVENUES	$	4,285,895		$	3,186,268		$	2,576,081
COSTS, EXPENSES AND OTHER
Cost of sales		3,267,910			2,395,812			2,070,715
Depreciation, depletion and amortization		466,587			365,066			301,608
Amortization of acquired sales contracts, net		(22,069	)		35,606			19,623
Selling, general and administrative expenses		119,056			118,177			97,787
Change in fair value of coal derivatives and coal trading activities, net		(2,907	)		8,924			(12,056	)
Acquisition and transition costs		54,676			—			13,726
Gain on Knight Hawk transaction		—			(41,577	)		—
Other operating income, net		(10,934	)		(19,724	)		(39,036	)
		3,872,319			2,862,284			2,452,367
Income from operations		413,576			323,984			123,714
Interest expense, net:
Interest expense		(230,186	)		(142,549	)		(105,932	)
Interest income		3,309			2,449			7,622
		(226,877	)		(140,100	)		(98,310	)
Other non-operating expense:
Bridge financing costs related to ICG		(49,490	)		—			—
Net loss resulting from early retirement of debt		(1,958	)		(6,776	)		—
		(51,448	)		(6,776	)		—
Income before income taxes		135,251			177,108			25,404
Provision for (benefit from) income taxes		(7,589	)		17,714			(16,775	)
Net income		142,840			159,394			42,179
Less: Net income attributable to noncontrolling interest		(1,157	)		(537	)		(10	)
Net income attributable to Arch Coal, Inc.	$	141,683		$	158,857		$	42,169
EARNINGS PER COMMON SHARE
Basic earnings per common share	$	0.75		$	0.98		$	0.28
Diluted earnings per common share	$	0.74		$	0.97		$	0.28
Basic weighted average shares outstanding		190,086			162,398			150,963
Diluted weighted average shares outstanding		190,905			163,210			151,272
Dividends declared per common share	$	0.43		$	0.39		$	0.36

The accompanying notes are an integral part of the consolidated financial statements.

F-5

CONSOLIDATED BALANCE SHEETS

	December 31
	2011			2010
	(In thousands, except per share data)
ASSETS
Current assets:
Cash and cash equivalents	$	138,149		$	93,593
Restricted cash		10,322			—
Trade accounts receivable		380,595			208,060
Other receivables		88,584			44,260
Inventories		377,490			235,616
Prepaid royalties		21,944			33,932
Deferred income taxes		42,051			—
Coal derivative assets		13,335			15,191
Other		110,304			104,262
Total current assets		1,182,774			734,914
Property, plant and equipment:
Coal lands and mineral rights		6,578,430			2,523,172
Plant and equipment		3,225,985			2,397,444
Deferred mine development		1,064,279			872,329
		10,868,694			5,792,945
Less accumulated depreciation, depletion and amortization		(2,919,544	)		(2,484,053	)
Property, plant and equipment, net		7,949,150			3,308,892
Other assets:
Prepaid royalties		86,626			66,525
Goodwill		596,103			114,963
Deferred income taxes		—			361,556
Equity investments		225,605			177,451
Other		173,701			116,468
Total other assets		1,082,035			836,963
Total assets	$	10,213,959		$	4,880,769
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities:
Accounts payable	$	383,782		$	198,216
Coal derivative liabilities		7,828			4,947
Deferred income taxes		—			7,775
Accrued expenses and other current liabilities		348,207			245,411
Current maturities of debt and short-term borrowings		280,851			70,997
Total current liabilities		1,020,668			527,346
Long-term debt		3,762,297			1,538,744
Asset retirement obligations		446,784			334,257
Accrued pension benefits		48,244			49,154
Accrued postretirement benefits other than pension		42,309			37,793
Accrued workers' compensation		71,948			35,290
Deferred income taxes		976,753			—
Other noncurrent liabilities		255,382			110,234
Total liabilities		6,624,385			2,632,818
Redeemable noncontrolling interest		11,534			10,444
Stockholders' equity:
Common stock, $0.01 par value, authorized 260,000 shares, issued 213,183 and 164,117 shares at December 31, 2011 and 2010, respectively		2,136			1,645
Paid-in capital		3,015,349			1,734,709
Treasury stock, 1,512 shares at December 31, 2011 and 2010, at cost		(53,848	)		(53,848	)
Retained earnings		622,353			561,418
Accumulated other comprehensive loss		(7,950	)		(6,417	)
Total stockholders' equity		3,578,040			2,237,507
Total liabilities and stockholders' equity	$	10,213,959		$	4,880,769

The accompanying notes are an integral part of the consolidated financial statements.

F-6

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY
Three Years Ended December 31, 2011

	Common Stock		Paid-In Capital			Treasury Stock, at Cost			Retained Earnings			Accumulated Other Comprehensive Loss			Total
	(In thousands, except per share data)
BALANCE AT JANUARY 1, 2009	$	1,447	$	1,381,496		$	(53,848	)	$	478,734		$	(79,096	)	$	1,728,733
Comprehensive income:
Net income attributable to Arch Coal, Inc.										42,169						42,169
Pension, postretirement and other post-employment benefits													12,176			12,176
Net amount reclassified to income													718			718
Unrealized losses on available-for- sale securities													(86	)		(86	)
Unrealized gains on derivatives													2,436			2,436
Net amount reclassified to income													43,999			43,999
Total comprehensive income																101,412
Dividends on common shares ($0.36 per share)										(54,969	)					(54,969	)
Issuance of 19,550 common shares		196		326,256												326,452
Issuance of 45 shares of common stock under the stock incentive plan — restricted stock and restricted stock units		0		0												0
Issuance of 13 shares of common stock under the stock incentive plan — stock options including income tax benefits		0		84												84
Employee stock-based compensation expense				13,394												13,394
BALANCE AT DECEMBER 31, 2009		1,643		1,721,230			(53,848	)		465,934			(19,853	)		2,115,106
Comprehensive income:
Net income attributable to Arch Coal, Inc.										158,857						158,857
Pension, postretirement and other post-employment benefits													9,750			9,750
Net amount reclassified to income													110			110
Unrealized gains on available-for- sale securities													1,841			1,841
Unrealized gains on derivatives													221			221
Net amount reclassified to income													1,514			1,514
Total comprehensive income																172,293
Dividends on common shares ($0.39 per share)										(63,373	)					(63,373	)
Issuance of 9 shares of common stock under the stock incentive plan — restricted stock and restricted stock units, net of forfeitures		0		0												0
Issuance of 155 shares of common stock under the stock incentive plan — stock options including income tax benefits		2		1,762												1,764
Employee stock-based compensation expense				11,717												11,717
BALANCE AT DECEMBER 31, 2010		1,645		1,734,709			(53,848	)		561,418			(6,417	)		2,237,507
Comprehensive income:
Net income attributable to Arch Coal, Inc.										141,683						141,683
Pension, postretirement and other post-employment benefits													4,331			4,331
Net amount reclassified to income													1,672			1,672
Unrealized gains on available-for- sale securities													114			114
Unrealized gains on derivatives													2,913			2,913
Net amount reclassified to income													(10,563	)		(10,563	)
Total comprehensive income																140,150
Dividends on common shares ($0.43 per share)										(80,748	)					(80,748	)
Issuance of 48,705 common shares		487		1,267,446												1,267,933
Issuance of 162 shares of common stock under the stock incentive plan — restricted stock and restricted stock units, net of forfeitures		2		(2	)											0
Issuance of 199 shares of common stock under the stock incentive plan — stock options including income tax benefits		2		2,314												2,316
Employee stock-based compensation expense				10,882												10,882
BALANCE AT DECEMBER 31, 2011	$	2,136	$	3,015,349		$	(53,848	)	$	622,353		$	(7,950	)	$	3,578,040

The accompanying notes are an integral part of the consolidated financial statements.

F-7

CONSOLIDATED STATEMENTS OF CASH FLOWS

	Year Ended December 31
	2011			2010			2009
	(In thousands)
OPERATING ACTIVITIES
Net income	$	142,840		$	159,394		$	42,179
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation, depletion and amortization		466,587			365,066			301,608
Amortization of acquired sales contracts, net		(22,069	)		35,606			19,623
Bridge financing costs related to ICG		49,490			—			—
Write down of assets acquired from ICG		7,316			—			—
Prepaid royalties expensed		34,842			34,605			29,746
Employee stock-based compensation		10,882			11,717			13,394
Amortization relating to financing activities		14,067			10,398			6,741
Gain on Knight Hawk transaction		—			(41,577	)		—
Net loss resulting from early retirement of debt		1,958			6,776			—
Changes in operating assets and liabilities:
Receivables		(74,914	)		(7,287	)		47,794
Inventories		(50,900	)		5,160			(28,518	)
Coal derivative assets and liabilities		6,079			9,554			32,266
Accounts payable, accrued expenses and other current liabilities		52,191			87,807			(44,764	)
Income taxes payable/receivable		(21,759	)		(1,364	)		2,100
Deferred income taxes		10,519			(12,405	)		(34,668	)
Asset retirement obligations		3,868			23,997			18,741
Other		11,245			9,700			(23,262	)
Cash provided by operating activities		642,242			697,147			382,980
INVESTING ACTIVITIES
Acquisitions of businesses, net of cash acquired		(2,894,339	)		—			(768,819	)
Decrease in restricted cash		5,167			—			—
Capital expenditures		(540,936	)		(314,657	)		(323,150	)
Proceeds from dispositions of property, plant and equipment		25,887			330			825
Additions to prepaid royalties		(29,957	)		(27,355	)		(26,755	)
Purchases of investments and advances to affiliates		(61,909	)		(46,185	)		(10,925	)
Consideration paid related to prior business acquisitions		(829	)		(1,262	)		(4,767	)
Reimbursement of deposits on equipment		—			—			3,209
Cash used in investing activities		(3,496,916	)		(389,129	)		(1,130,382	)
FINANCING ACTIVITIES
Proceeds from the issuance of senior notes		2,000,000			500,000			584,784
Proceeds from the issuance of common stock, net		1,267,933			—			326,452
Payments to retire debt		(605,178	)		(505,627	)		—
Net increase (decrease) in borrowings under lines of credit and commercial paper program		424,396			(196,549	)		(85,815	)
Net proceeds from (payments on) other debt		5,334			82			(2,986	)
Debt financing costs		(114,823	)		(12,751	)		(29,659	)
Dividends paid		(80,748	)		(63,373	)		(54,969	)
Issuance of common stock under incentive plans		2,316			1,764			84
Contribution from noncontrolling interest		—			891			—
Cash provided by (used in) financing activities		2,899,230			(275,563	)		737,891
Increase (decrease) in cash and cash equivalents		44,556			32,455			(9,511	)
Cash and cash equivalents, beginning of year		93,593			61,138			70,649
Cash and cash equivalents, end of year	$	138,149		$	93,593		$	61,138
SUPPLEMENTAL CASH FLOW INFORMATION:
Cash paid during the year for interest	$	213,697		$	134,866		$	76,801
Cash paid during the year for income taxes	$	7,094		$	36,765		$	17,482

The accompanying notes are an integral part of the consolidated financial statements.

F-8

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

1.    Accounting Policies

Basis of Presentation

        The consolidated financial statements include the accounts of Arch Coal, Inc. and its subsidiaries and controlled entities ("the Company"). The Company produces coal from surface and underground mines located throughout the United States for sale to domestic and international customers as steam coal to power plants and industrial facilities and metallurgical coal used in steel production. The Company expanded further into metallurgical coal markets with the acquisition of International Coal Group, Inc. ("ICG") on June 15, 2011, as described in Note 3, "Business Combinations." The Company operates 23 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 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.

Accounting Pronouncements

        There were no accounting pronouncements whose adoption had, or is expected to have, a material impact on the Company's consolidated financial statements.

Accounting Estimates

        The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and revenues and expenses in the accompanying consolidated financial statements and the disclosure of contingent assets and liabilities. Actual results could differ from those estimates.

Cash and Cash Equivalents

        Cash and cash equivalents are stated at cost. Cash equivalents consist of highly-liquid investments with an original maturity of three months or less when purchased. At December 31, 2011 and 2010, the carrying amounts of cash and cash equivalents approximate their fair value.

Allowance for Uncollectible Receivables

        The Company establishes an allowance for uncollectible receivables for the amounts of trade accounts receivable and other receivables that are not expected to be collected, based on past collection history, the economic environment and specified risks identified in the receivables portfolio. Receivables are considered past due if the full payment is not received by the contractual due date. At December 31, 2011 and 2010, there was either no allowance or an insignificant allowance for uncollectible receivables.

Inventories

        Coal and supplies inventories are valued at the lower of average cost or market. Coal inventory costs include labor, supplies, equipment costs, transportation costs incurred prior to the transfer of title to customers and operating overhead. The costs of removing overburden, called stripping costs, incurred during the production phase of the mine are considered variable production costs and are included in the cost of the coal extracted during the period the stripping costs are incurred.

F-9

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Investments and Membership Interests in Joint Ventures

        Investments and membership interests in joint ventures are accounted for under the equity method of accounting if the Company has the ability to exercise significant influence, but not control, over the entity. The Company's share of the entity's income is reflected in other operating income, net in the consolidated statements of income. Information about investment activity is provided in Note 8, "Equity Investments and Membership Interests in Joint Ventures."

        Marketable equity securities held by the Company that do not qualify for equity method accounting are classified as available-for-sale and are recorded at their fair value on the balance sheet. Unrealized gains and losses on these investments are recorded in other comprehensive income. A decline in the value of an investment that is considered other-than-temporary is recognized in income.

Prepaid Royalties

        Leased mineral rights are often acquired through royalty payments. When royalty payments represent prepayments recoupable against future production, they are recorded as a prepaid asset, with amounts expected to be recouped within one year classified as current. When the coal is mined under these leases the royalties are recouped and the prepayment is charged to cost of sales.

Acquired Sales Contracts

        Coal supply agreements (sales contracts) acquired in a business combination are capitalized at their fair value and amortized over the tons of coal shipped during the term of the contract. The fair value of a sales contract is determined by discounting the cash flows attributable to the difference between the contract price and the prevailing forward prices for the tons under contract at the date of acquisition. See Note 6, "Acquired Sales Contracts" for further information related to the Company's acquired sales contracts.

Exploration Costs

        Costs to acquire permits for exploration activities are capitalized. Drilling and other costs related to locating coal deposits and evaluating the economic viability of such deposits are expensed as incurred.

Property, Plant and Equipment

Plant and Equipment

        Plant and equipment are recorded at cost. Interest costs incurred during the construction period for major asset additions are capitalized. Expenditures that extend the useful lives of existing plant and equipment or increase the productivity of the asset are capitalized. The cost of maintenance and repairs that do not extend the useful life or increase the productivity of the asset are expensed as incurred.

        Preparation plants and loadouts are depreciated using the units-of-production method over the estimated recoverable reserves, subject to a minimum level of depreciation. Other plant and equipment are depreciated principally using the straight-line method over the estimated useful lives of the assets, limited by the remaining life of the mine. The useful lives of mining equipment, including longwalls, draglines and shovels, range from 5 to 32 years. The useful lives of buildings and leasehold improvements generally range from 10 to 30 years.

Deferred Mine Development

        Costs of developing new mines or significantly expanding the capacity of existing mines are capitalized and amortized using the units-of-production method over the estimated recoverable reserves that are associated with the

F-10

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

property being benefited. Costs may include construction permits and licenses; mine design; construction of access roads, shafts, slopes and main entries; and removing overburden to access reserves in a new pit. Additionally, deferred mine development includes the asset cost associated with asset retirement obligations.

Coal Lands and Mineral Rights

        Rights to coal reserves may be acquired directly through governmental or private entities. A significant portion of the Company's coal reserves are controlled through leasing arrangements. The net book value of the Company's leased coal interests was $1.6 billion at December 31, 2011 and 2010. Payments to acquire royalty lease agreements and lease bonus payments are capitalized as a cost of the underlying mineral reserves and depleted over the life of proven and probable reserves. Coal lease rights are depleted using the units-of-production method, and the rights are assumed to have no residual value. Lease agreements are generally long-term in nature (original terms range from 10 to 50 years), and substantially all of the leases contain provisions that allow for automatic extension of the lease term providing certain requirements are met. See Note 2, "Property Transactions" for further disclosures on coal lease agreements.

Impairment

        If facts and circumstances suggest that the carrying value of a long-lived asset or asset group may not be recoverable, the asset or asset group is reviewed for potential impairment. If this review indicates that the carrying amount of the asset will not be recoverable through projected undiscounted cash flows generated by the asset and its related asset group over its remaining life, then an impairment loss is recognized by reducing the carrying value of the asset to its fair value. The Company may, under certain circumstances, idle mining operations in response to market conditions or other factors. Because an idling is not a permanent closure, it is not considered an automatic indicator of impairment.

Goodwill

        In a business combination, goodwill represents the excess of the purchase price over the fair value assigned to the net tangible and identifiable intangible assets acquired. The Company tests goodwill for impairment annually as of the beginning of the fourth quarter, or when circumstances indicate a possible impairment may exist. If the results of the testing indicate that the carrying amount of a reporting unit exceeds the fair value of the reporting unit, the fair value of goodwill must be calculated. An impairment loss generally would be recognized when the carrying amount of goodwill exceeds the implied fair value of goodwill, determined by subtracting the fair value of the other assets and liabilities associated with the reporting unit from the total fair value of the reporting unit. The fair value of a reporting unit is determined using a discounted cash flow ("DCF") technique. A number of significant assumptions and estimates are involved in the application of the DCF analysis to forecast operating cash flows, including the discount rate and projections of selling prices and costs to produce.

Deferred Financing Costs

        The Company capitalizes costs incurred in connection with new borrowings, the establishment or enhancement of credit facilities and the issuance of debt securities. These costs are amortized as an adjustment to interest expense over the life of the borrowing or term of the credit facility using the interest method. The unamortized balance of deferred financing costs was $90.5 million and $37.6 million at December 31, 2011 and 2010, respectively. Amounts classified as current were $15.8 million and $9.6 million at December 31, 2011 and 2010, respectively. Current amounts are recorded in other current assets and noncurrent amounts are recorded in other assets in the accompanying consolidated balance sheets.

F-11

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Revenue Recognition

        Revenues include sales to customers of coal produced at Company operations and coal purchased from third parties. The Company recognizes revenue at the time risk of loss passes to the customer at contracted amounts. Transportation costs are included in cost of sales and amounts billed by the Company to its customers for transportation are included in revenues.

Other Operating Income, Net

        Other operating income, net in the accompanying consolidated statements of income reflects income and expense from sources other than physical coal sales, including: bookouts, the practice of offsetting purchase and sale contracts for shipping convenience purposes, and contract settlements; royalties earned from properties leased to third parties; income from equity investments; gains and losses from dispositions of assets; and realized gains and losses on derivatives that do not qualify for hedge accounting and are not held for trading purposes.

Asset Retirement Obligations

        The Company's legal obligations associated with the retirement of long-lived assets are recognized at fair value at the time the obligations are incurred. Accretion expense is recognized through the expected settlement date of the obligation. Obligations are incurred at the time development of a mine commences for underground and surface mines or construction begins for support facilities, refuse areas and slurry ponds. The obligation's fair value is determined using a DCF technique and is based upon permit requirements and various estimates and assumptions that would be used by market participants, including estimates of disturbed acreage, reclamation costs and assumptions regarding equipment productivity. Upon initial recognition of a liability, a corresponding amount is capitalized as part of the carrying value of the related long-lived asset.

        The Company reviews its asset retirement obligation at least annually and makes necessary adjustments for permit changes as granted by state authorities and for revisions of estimates of the amount and timing of costs. For ongoing operations, adjustments to the liability result in an adjustment to the corresponding asset. For idle operations, adjustments to the liability are recognized as income or expense in the period the adjustment is recorded. Any difference between the recorded obligation and the actual cost of reclamation is recorded in profit or loss in the period the obligation is settled. See additional discussion in Note 14, "Asset Retirement Obligations."

Derivative Instruments

        The Company generally utilizes derivative instruments to manage exposures to commodity prices. Additionally, the Company may hold certain coal derivative instruments for trading purposes. Derivative financial instruments are recognized in the balance sheet at fair value. Certain coal contracts may meet the definition of a derivative instrument, but because they provide for the physical purchase or sale of coal in quantities expected to be used or sold by the Company over a reasonable period in the normal course of business, they are not recognized on the balance sheet.

        Certain derivative instruments are designated as the hedge instrument in a hedging relationship. In a fair value hedge, the Company hedges the risk of changes in the fair value of a firm commitment, typically a fixed-price coal sales contract. Changes in both the hedged firm commitment and the fair value of a derivative used as a hedge instrument in a fair value hedge are recorded in earnings. In a cash flow hedge, the Company hedges the risk of changes in future cash flows related to a forecasted purchase or sale. Changes in the fair value of the derivative instrument used as a hedge instrument in a cash flow hedge are recorded in other comprehensive income. Amounts in other comprehensive income are reclassified to earnings when the hedged transaction affects earnings and are classified in a manner consistent with the transaction being hedged. The Company formally documents the

F-12

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

relationships between hedging instruments and the respective hedged items, as well as its risk management objectives for hedge transactions.

        The Company evaluates the effectiveness of its hedging relationships both at the hedge's inception and on an ongoing basis. Any ineffective portion of the change in fair value of a derivative instrument used as a hedge instrument in a fair value or cash flow hedge is recognized immediately in earnings. The ineffective portion is based on the extent to which exact offset is not achieved between the change in fair value of the hedge instrument and the cumulative change in expected future cash flows on the hedged transaction from inception of the hedge in a cash flow hedge or the change in the fair value. Ineffectiveness was insignificant for the years ended December 31, 2011, 2010 and 2009. See Note 10, "Derivative Instruments" for further disclosures related to the Company's derivative instruments.

Fair Value

        Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly hypothetical transaction between market participants at a given measurement date. Valuation techniques used must maximize the use of observable inputs and minimize the use of unobservable inputs. See Note 13, "Fair Values of Financial Instruments" for further disclosures related to the Company's fair value estimates.

Income Taxes

        Deferred income taxes are provided for temporary differences arising from differences between the financial statement amount and tax basis of assets and liabilities existing at each balance sheet date using enacted tax rates anticipated to be in effect when the related taxes are expected to be paid or recovered. A valuation allowance is established if it is more likely than not that a deferred tax asset will not be realized. In determining the need for a valuation allowance, the Company considers projected realization of tax benefits based on expected levels of future taxable income, available tax planning strategies and its overall deferred tax position. See Note 12, "Taxes" for further disclosures about income taxes.

Benefit Plans

        The Company has non-contributory defined benefit pension plans covering most of its salaried and hourly employees. Benefits are generally based on the employee's age and compensation. The Company also currently provides certain postretirement medical and life insurance coverage for eligible employees. The cost of providing these benefits are determined on an actuarial basis and accrued over the employee's period of active service.

        The Company recognizes the overfunded or underfunded status of these plans as determined on an actuarial basis on the balance sheet and the changes in the funded status are recognized in other comprehensive income. See Note 16, "Employee Benefit Plans" for additional disclosures relating to these obligations.

Stock-Based Compensation

        The compensation cost of all stock-based awards is determined based on the grant-date fair value of the award, and is recognized in income over the requisite service period. The grant-date fair value of option awards is determined using a Black-Scholes option pricing model. Compensation cost for an award with performance conditions is accrued if it is probable that the conditions will be met. See further discussion in Note 18, "Stock Based Compensation and Other Incentive Plans."

F-13

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

2.    Property Transactions

        On December 14, 2011, the Company was awarded a federal coal lease for the South Hilight tract in Wyoming for a price of $300.0 million. The bid price will be paid in five equal installments, with the first one made in December 2011. The coal lease will give the Company the right to mine an estimated 222 million tons of coal reserves. The South Hilight tract is contiguous to the Company's Black Thunder mining complex.

        On November 12, 2009, the Company entered into a lease of coal reserves and other coal resources from Great Northern Properties Limited Partnership in Montana for $73.1 million. On March 18, 2010, the Company was awarded a Montana state coal lease for the Otter Creek tracts for a price of $85.8 million. These two transactions gave the Company the right to mine approximately 1.4 billion tons of coal reserves in the Montana's Otter Creek area.

        The total of the Company's future lease bonus payments due are $23.4 million in 2012, $83.4 million in 2013, $67.3 million in 2014, $60.0 million in 2015 and $60.0 million in 2016.

3.    Business Combinations

        On June 15, 2011, the Company completed its acquisition of ICG, a leading coal producer, adding 12 mining complexes in Appalachia, one complex in the Illinois Basin and one mine under development in Appalachia, along with other coal reserves not currently in development. The Company acquired all of ICG's outstanding shares of common stock. The acquisition was financed with the proceeds from the Company's sale of common stock and issuance of senior notes. See Note 5, "Debt and Financing Arrangements" and Note 17, "Capital Stock" for further information about these transactions.

        The following table summarizes the consideration paid for ICG and the recognized amounts of assets acquired and liabilities assumed at the acquisition date:

	(In millions)
Consideration paid, net of cash acquired	$	2,894.4
Recognized amounts of net tangible and intangible assets acquired and liabilities assumed:
Restricted cash		15.5
Receivables		113.2
Inventories		91.0
Net property, plant and equipment, including mineral rights		4,582.6
Goodwill		480.3
Other assets		35.9
Accounts payable		(86.0	)
Other accrued expenses and current liabilities		(59.1	)
Debt		(604.8	)
Litigation accrual		(108.9	)
Accrued postretirement benefits		(47.7	)
Asset retirement obligation		(112.7	)
Coal supply agreements, net		(91.0	)
Deferred income taxes, net		(1,278.9	)
Other		(35.0	)
Net tangible and intangible assets acquired	$	2,894.4

        The Company is awaiting the receipt of the final valuation report from a third party valuation services firm. As a result the fair values for mineral rights, goodwill and deferred taxes may not be final.

F-14

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

        The revenues and income before income taxes related to the acquired operations reflected in the consolidated statements of income since the date of acquisition were $606.9 million and $14.6 million, respectively.

        The following unaudited pro forma information has been prepared for illustrative purposes and assumes that the business combination occurred on January 1, 2010. The unaudited pro forma results have been prepared based upon ICG's historical results and estimates of the ongoing effects of the transactions that the Company believes are reasonable and supportable. The results are not necessarily reflective of the consolidated results of operations had the acquisition actually occurred on January 1, 2010, nor are they indicative of future operating results.

        The unaudited supplemental pro forma financial information of the combined entity follows:

	Year Ended December 31,
	2011		2010
	(In millions)
Total revenues
As reported	$	4,285.9	$	3,186.3
Pro forma	$	4,825.6	$	4,299.9
Net income attributable to Arch Coal
As reported	$	141.7	$	158.9
Pro forma	$	113.5	$	(1.2	)

        The pro forma income before income taxes includes adjustments to operating costs to reflect the new basis in assets acquired and interest expense to reflect the debt incurred to finance the acquisition. In addition, the following pre-tax costs and expenses reflected in the accompanying consolidated statement of income for the year ended December 31, 2011 are reflected in the pro forma results above as of January 1, 2010.

	(In millions)
Costs of completing the acquisition	$	31.6
Severance costs		15.8
Write off of acquired assets		7.3
Bridge financing fees		49.5
	$	104.2

        Severance costs represent both change in control payments to executives and severance for employees terminated after the acquisition. The acquired asset write-off relates to a preparation plant and loadout of an acquired ICG mining operation. The acquired operation was combined with an existing operation of the Company, and utilizes an existing facility.

        Synergies from the acquisition are not reflected in the pro forma results.

        In conjunction with the acquisition, the Company had $10.3 million of restricted cash at December 31, 2011 to fund change in control payments for executives.

        On October 1, 2009 the Company purchased the Jacobs Ranch mining operations for a purchase price of $768.8 million. The acquired operations included approximately 345 million tons of coal reserves. The acquired mining operations were integrated into the Company's Black Thunder mining operations in its Powder River Basin segment. To finance the acquisition, the Company sold shares of its common stock and issued senior notes. See Note 5, "Debt and Financing Arrangements" and Note 17 "Capital Stock" for further information about these transactions.

F-15

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

4.    Goodwill

        Changes in the carrying value of goodwill for the years ended December 31, 2011, 2010 and 2009 are as follows:

	(In thousands)
Balance at January 1, 2009	$	46,832
Consideration paid related to prior business acquisitions		4,767
Acquisition of Jacobs Ranch		62,102
Balance at December 31, 2009		113,701
Consideration paid related to prior business acquisitions		1,262
Balance at December 31, 2010		114,963
Consideration paid related to prior business acquisitions		829
Acquisition of ICG		480,311
Balance at December 31, 2011	$	596,103

        Goodwill of $115.8 million has been allocated to the Company's Powder River Basin segment and goodwill of $480.3 million has allocated to the Company's Appalachia segment for impairment testing purposes. The goodwill recognized in the ICG acquisition relates to the impact of volatility in the pricing for metallurgical coal and geological and technical efforts prior to the acquisition relating to the mine development project in progress. The goodwill related to the acquisition of ICG is not expected to be deductible for income tax purposes; however, the remaining goodwill is expected to be deductible. The consideration paid related to prior business acquisitions represents ongoing adjustments to the purchase price of a previous acquisition resulting from a 2008 tax settlement.

5.    Debt and Financing Arrangements

        Debt consists of the following:

	December 31,
	2011		2010
	(In thousands)
Commercial paper	$	—	$	56,904
Indebtedness to banks under credit facilities		481,300		—
6.75% senior notes ($450.0 million face value) due July 1, 2013		450,971		451,618
8.75% senior notes ($600.0 million face value) due August 1, 2016		588,974		587,126
7.00% senior notes due June 15, 2019 at par		1,000,000		—
7.25% senior notes due October 1, 2020 at par		500,000		500,000
7.25% senior notes due June 15, 2021 at par		1,000,000		—
Other		21,903		14,093
		4,043,148		1,609,741
Less current maturities of debt and short-term borrowings		280,851		70,997
Long-term debt	$	3,762,297	$	1,538,744

        The current maturities of debt include contractual maturities, as well as amounts borrowed that are supported by credit facilities that have a term of less than one year and amounts borrowed under credit facilities with terms longer than one year that the Company does not intend to refinance on a long-term basis, based on cash projections and management's plans.

F-16

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

ICG Debt

        Upon the closing of the ICG acquisition, the Company gave a 30-day redemption notice to the Trustee of ICG's 9.125% senior notes and legally discharged its obligation under the 9.125% senior notes by depositing $260.7 million with the Trustee to redeem the debt. On July 14, 2011, all of the outstanding 9.125% senior notes were redeemed at an aggregate price of $251.4 million, including the required make-whole premium, plus accrued interest of $5.2 million, and the remainder of the deposit was returned to the Company.

        At the acquisition date, ICG's 4.00% convertible senior notes with a fair value of $298.5 million and 9.00% convertible senior notes with a fair value of $1.7 million ("convertible notes") became convertible into cash, pursuant to the amended indentures governing the convertible notes, at a calculated conversion rate of $2,614.6848 for each $1,000 in principal amount surrendered for conversion for the 4.00% convertible notes and $2,392.73414 for the 9.00% convertible notes for conversions occurring prior to August 17, 2011.

        At the acquisition date, other ICG debt had a fair value of approximately $54.0 million and consisted mainly of equipment notes and insurance notes payable.

        The Company recognized a net loss of $2.0 million during the year ended December 31, 2011 on the early extinguishment of ICG's debt, including the conversions of the 4.00% and 9.00% convertible notes described above. The remaining amounts outstanding under the convertible notes and other ICG debt is included in "other" in the debt table above.

Credit Facilities

        On June 14, 2011, the Company amended and restated its secured credit facility to allow for up to $2.0 billion in borrowings. The Company paid and deferred $21.1 million in financing fees related to the amendment of this agreement. Borrowings under this credit facility bear interest at a floating rate based on LIBOR determined by reference to the Company's leverage ratio, as calculated in accordance with the credit agreement. The credit facility has a five-year term that expires on June 14, 2016 and is secured by substantially all of the Company's assets as well as its ownership interests in substantially all of its subsidiaries, excluding its ownership interests in Arch Western and its subsidiaries. Commitment fees of 0.50% per annum are payable on the average unused daily balance of the revolving credit facility. The weighted-average interest rate of the Company's outstanding borrowings under the credit facility was 3.04% at December 31, 2011. Financial covenant requirements may restrict the amount of unused capacity available to the Company for borrowings and letters of credit.

        The Company maintains an accounts receivable securitization program under which eligible trade receivables are sold, without recourse, to a multi-seller, asset-backed commercial paper conduit. The entity through which these receivables are sold is consolidated into the Company's financial statements. The Company may borrow and draw letters of credit against the facility, and pays facility fees, program fees and letter of credit fees (based on amounts of outstanding letters of credit) at rates that vary with its leverage ratio, as defined under the program. The Company entered into an amendment to its accounts receivable program in November of 2011 to increase the eligible receivables pool, as defined by the agreement, to include receivables generated from the acquired ICG subsidiaries. On December 13, 2011, the Company entered into another amendment to its accounts receivable securitization program to increase the size of the program to allow for aggregate borrowings and letters of credit of up to $250.0 million from $175.0 million. The total aggregate borrowings and letters of credit are limited by eligible accounts receivable, as defined under the terms of the agreement. The credit facility supporting the borrowings under the program is subject to renewal annually, and expires on December 11, 2012. The interest rate in effect as of December 31, 2011 was 0.73%.

        On June 14, 2011, the Company terminated its commercial paper placement program and the supporting credit facility.

F-17

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

        The Company's average borrowing level under these programs was approximately $234.2 million and $132.0 million for the years ended December 31, 2011 and 2010, respectively.

Availability

        As of December 31, 2011, the Company had $375.0 million of borrowings outstanding under the amended and restated secured credit facility and $106.3 million of borrowings outstanding under its accounts receivable securitization program. The Company also had $146.6 million of outstanding letters of credit at December 31, 2011. As of December 31, 2011, the Company had availability of $901.4 million under all lines of credit, as limited by customary financial covenants that may limit the Company's total debt based on defined earnings measurements.

2013 Senior Notes

        The 6.75% senior notes due in 2013 ("2013 Notes") were issued by the Company's subsidiary, Arch Western Finance LLC ("Arch Western Finance"), under an indenture dated June 25, 2003. The Company redeemed $500.0 million aggregate principal amount of the 2013 Notes on September 8, 2010. The Company recognized a loss on the redemption of $6.8 million, including the payment of the $5.6 million redemption premium and the write-off of $3.3 million of unamortized debt financing costs, partially offset by the write-off of $2.1 million of the original issue premium. The senior notes are guaranteed by Arch Western and certain of its subsidiaries and are secured by an intercompany note from Arch Coal, Inc. to Arch Western. The terms of the senior notes contain restrictive covenants that limit Arch Western's ability to, among other things, incur additional debt, sell or transfer assets, and make certain investments. Of the aggregate principal outstanding at December 31, 2011 and 2010, $118.4 million of the 2013 Notes were issued at a premium of 104.75% of par. The premium is amortized over the term of the notes. Interest is payable on the notes on January 1 and July 1 of each year. The notes are redeemable at any time at their face value.

2016 Senior Notes

        On July 31, 2009, the Company issued $600.0 million in aggregate principal amount of 8.75% senior unsecured notes due 2016 ("2016 Notes") at an initial issue price of 97.464% of the face amount. The Company incurred issue costs of $14.5 million in association with the 2016 Notes. Interest is payable on the notes on February 1 and August 1 of each year. At any time on or after August 1, 2013, the Company may redeem some or all of the notes. The redemption price, reflected as a percentage of the principal amount, is: 104.375% for notes redeemed between August 1, 2013 and July 31, 2014; 102.188% for notes redeemed between August 1, 2014 and July 31, 2015; and 100% for notes redeemed on or after August 1, 2015. In addition, at any time and on one or more occasions prior to August 1, 2012, the Company may redeem an aggregate principal amount of senior notes not to exceed 35% of the original aggregate principal amount of the senior notes outstanding with the proceeds of one or more public equity offerings, at a redemption price equal to 108.750%.

2020 Senior Notes

        On August 9, 2010, we issued $500.0 million in aggregate principal amount of 7.25% senior unsecured notes due in 2020 ("2020 Notes") at par. Interest is payable on the 2020 Notes on April 1 and October 1 of each year. At any time on or after October 1, 2015, the Company may redeem some or all of the notes. The redemption price reflected as a percentage of the principal amount is: 103.625% for notes redeemed between October 1, 2015 and September 30, 2016; 102.417% for notes redeemed between October 1, 2016 and September 30, 2017; 101.208% for notes redeemed between October 1, 2017 and September 30, 2018; and 100% for notes redeemed on or after October 1, 2018. In addition, at any time and on one or more occasions prior to October 1, 2013, the Company may redeem an aggregate principal amount of senior notes not to exceed 35% of the original aggregate principal

F-18

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

amount of the senior notes outstanding with the proceeds of one or more public equity offerings, at a redemption price equal to 107.250%.

2019 and 2021 Senior Notes

        On June 14, 2011, the Company entered into an indenture in conjunction with the issuance of the 7.00% unsecured senior notes due 2019 ("2019 Notes") and the 7.25% unsecured senior notes due 2021 ("2021 Notes") as discussed in Note 3, "Business Combinations." Interest is payable on the 2019 Notes and 2021 Notes on June 15 and December 15 of each year.

        At any time prior to June 15, 2014, the Company may redeem up to 35% of the original aggregate principal amount of each of the 2019 Notes and 2021 Notes, plus accrued and unpaid interest, with the net proceeds from certain equity offerings, at a redemption price, reflected as a percentage of the principal amount, equal to 107.0% and 107.25%, respectively. The Company may redeem the 2019 Notes prior to June 15, 2015 and the 2021 Notes prior to June 15, 2016 at the respective make-whole prices set forth in the indenture. On or after June 15, 2015, the Company may redeem the 2019 Notes at redemption prices, reflected as a percentage of the principal amount, of: 103.5% from June 15, 2015 through June 14, 2016; 101.75% from June 15, 2016 through June 14, 2017; and 100% beginning on June 15, 2017. On or after June 15, 2016, the Company may redeem the 2021 Notes at redemption prices, reflected as a percentage of the principal amount, of: 103.625% from June 15, 2016 through June 14, 2017; 102.417% from June 15, 2017 through June 14, 2018; 101.208% from June 15, 2018 through June 14, 2019 and 100% beginning on June 15, 2019. In each case, accrued and unpaid interest at the redemption date is due upon redemption. Upon a change in control, the Company is required to make a tender offer for both series of notes at a price of 101% of the principal amount. The Company incurred issue costs of $44.2 million related to the issuance of these notes.

        The Company and the guarantor subsidiaries entered into a registration rights agreement (the "Registration Rights Agreement") in connection with the issuance and sale of the 2019 Notes and 2021 Notes. Pursuant to the Registration Rights Agreement, the Company and the guarantor subsidiaries agreed to file a registration statement with the Securities and Exchange Commission to register an exchange offer pursuant to which the Company will offer to exchange a like aggregate principal amount of senior notes identical in all material respects to the 2019 Notes and 2021 Notes, except for terms relating to additional interest and transfer restrictions, for any or all of the outstanding 2019 Notes and 2021 Notes. Pursuant to the Registration Rights Agreement, the Company must use commercially reasonable efforts to cause the registration statement to become effective as soon as practicable and to complete the exchange offer no later than June 13, 2012. Should those events not occur within the specified time frame, the applicable interest rates on the 2019 Notes and the 2021 Notes shall be increased by one-quarter of one percent per annum for the first 90 days following the occurrence of such failure. Such interest rate will increase by an additional one-quarter of one percent per annum thereafter at the end of each subsequent 90-day period up to a maximum aggregate increase of one percent per annum. Once any of the required events occur, the interest rates will revert to the rate specified in the indenture governing the 2019 Notes and 2021 Notes.

        The 2016, the 2019, the 2020 and the 2021 unsecured senior notes are guaranteed by substantially all of the Company's subsidiaries, including the newly acquired subsidiaries of ICG and excluding Arch Western, its subsidiaries and Arch Receivable Company, LLC and the Company's subsidiaries outside the U.S.

        Expected aggregate maturities of debt for the next five years are $280.9 million in 2012, $672.4 in 2013, $0 in 2014, $0 in 2015 and $600.0 million in 2016.

        Terms of the Company's credit facilities and leases contain financial and other covenants that limit the ability of the Company to, among other things, acquire, dispose, merge or consolidate assets; incur additional debt; pay dividends and make distributions or repurchase stock; make investments; create liens; issue and sell capital stock of

F-19

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

subsidiaries; enter into restrictions affecting the ability of restricted subsidiaries to make distributions, loans or advances to the Company; engage in transactions with affiliates and enter into sale and leaseback transactions. The terms also require the Company to, among other things, maintain various financial ratios and comply with various other financial covenants, including an interest coverage ratio test, as defined in the indentures. In addition, the covenants require the Company to pledge assets to collateralize the revolving credit facility. The assets pledged include equity interests in wholly-owned subsidiaries, certain real property interests, accounts receivable and inventory of the Company. Failure by the Company to comply with such covenants could result in an event of default, which, if not cured or waived, could have a material adverse effect on the Company. The Company complied with all financial covenants at December 31, 2011.

6.    Acquired Sales Contracts

        The acquired sales contracts reflected in the consolidated balance sheets are as follows:

	December 31, 2011						December 31, 2010
	Assets			Liabilities			Assets			Liabilities
	(In thousands)						(In thousands)
Acquired fair value	$	149,457		$	166,697		$	114,453		$	40,654
Accumulated amortization		(115,322	)		(69,699	)		(82,376	)		(14,613	)
Total	$	34,135		$	96,998		$	32,077		$	26,041
Net total				$	(62,863	)	$	6,036
Balance Sheet classification:
Other current	$	18,929		$	38,441		$	25,063		$	5,615
Other noncurrent	$	15,206		$	58,557		$	7,014		$	20,426

        Above-market contracts with a fair value of $35.0 million and below-market contracts with a fair value of $126.0 million were acquired from ICG. See Note 3, "Business Combinations" for discussion of purchase price adjustments.

        The Company anticipates amortization income of all acquired sales contracts, based upon expected shipments in the next five years, to be approximately $18.5 million in 2012, $5.2 million in 2013, $3.3 million in 2014, $12.7 million in 2015 and $7.7 million in 2016.

7.    Accumulated Other Comprehensive Income (Loss)

        Other comprehensive income (loss) includes transactions recorded in stockholders' equity during the year, excluding net income and transactions with stockholders. Following are the items included in accumulated other comprehensive income (loss):

	Derivative Instruments			Pension, Postretirement and Other Post- Employment Benefits			Available-for- Sale Securities			Accumulated Other Comprehensive Loss
	(In thousands)
Balance at January 1, 2009	$	(45,249	)	$	(33,433	)	$	(414	)	$	(79,096	)
2009 activity, before tax		72,553			20,124			(136	)		92,541
2009 activity, tax effect		(26,118	)		(7,230	)		50			(33,298	)
Balance at December 31, 2009		1,186			(20,539	)		(500	)		(19,853	)
2010 activity, before tax		2,711			15,406			2,877			20,994
2010 activity, tax effect		(976	)		(5,546	)		(1,036	)		(7,558	)
Balance at December 31, 2010		2,921			(10,679	)		1,341			(6,417	)
2011 activity, before tax		(11,951	)		9,345			176			(2,430	)
2011 activity, tax effect		4,301			(3,342	)		(62	)		897
Balance at December 31, 2011	$	(4,729	)	$	(4,676	)	$	1,455		$	(7,950	)

F-20

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

8.    Equity Investments and Membership Interests in Joint Ventures

        Below are the equity method investments reflected in the consolidated balance sheets:

	Knight Hawk			DKRW			DTA			Tenaska			Millennium			Tongue River		Total
	(In thousands)
Balance at January 1 , 2009	$	48,093		$	25,124		$	14,544		$	—		$	—		$	—	$	87,761
Advances to (distributions from) affiliates, net		(5,164	)		—			2,925			—			—			—		(2,239	)
Equity in comprehensive income (loss)		6,674			(1,535	)		(3,393	)		—			—			—		1,746
Balance at December 31, 2009		49,603			23,589			14,076			—			—			—		87,268
Investments in affiliates		77,637			—			—			9,768			—			—		87,405
Advances to (distributions from) affiliates, net		(12,639	)		—			4,264			—			—			—		(8,375	)
Equity in comprehensive income (loss)		16,649			(1,628	)		(3,868	)		—			—			—		11,153
Balance at December 31, 2010	$	131,250		$	21,961		$	14,472		$	9,768		$	—		$	—	$	177,451
Investments in affiliates		—			—			—			5,500			25,000			12,989		43,489
Advances to (distributions from) affiliates, net		(16,621	)		—			6,498			—			3,477			—		(6,646	)
Equity in comprehensive income (loss)		20,596			(2,246	)		(4,884	)		(2	)		(2,153	)		—		11,311
Balance at December 31, 2011	$	135,225		$	19,715		$	16,086		$	15,266		$	26,324		$	12,989	$	225,605
Notes receivable from investees:
Balance at December 31, 2010	$	1,700		$	18,100		$	—		$	4,100		$	—		$	—	$	23,900
Balance at December 31, 2011		—			30,751			—			5,059			—			—		35,810

        The Company holds an equity interest in Knight Hawk Holdings, LLC ("Knight Hawk"), a coal producer in the Illinois Basin. In June 2010, the Company exchanged 68.4 million tons of coal reserves in the Illinois Basin for an additional 9% ownership interest, increasing the Company's ownership in Knight Hawk to 42% from 33¹/3%. The Company recognized a gain of $41.6 million on the transaction, representing the difference between the fair value and the $12.1 million net book value of the coal reserves, adjusted for the Company's retained ownership interest in the reserves through its investment in Knight Hawk. In December 2010, the Company increased its ownership interest in Knight Hawk to 49% for $26.6 million in cash.

        The Company holds a 24% equity interest in DKRW Advanced Fuels LLC ("DKRW"), a company engaged in developing coal-to-liquids facilities. Under a coal reserve purchase option with DKRW, DKRW could purchase reserves from the Company, which the Company would then mine on a contract basis for DKRW. DKRW may borrow funds from the Company under a convertible secured promissory note. Amounts borrowed are due and payable in cash or in additional equity interests on the earlier of April 15, 2012 or upon the closing of DKRW's next financing, bear interest at the rate of 1.25% per month, and are secured by DKRW's equity interests in Medicine Bow Fuel & Power LLC. As of December 31, 2011, DKRW had borrowed the maximum amount allowed under the note. The note balances above are reflected in other receivables on the consolidated balance sheets.

        The Company holds a general partnership interest of 21.875% in Dominion Terminal Associates ("DTA"), which is accounted for under the equity method. DTA operates a ground storage-to-vessel coal transloading facility in Newport News, Virginia for use by the partners. Under the terms of a throughput and handling agreement with DTA, each partner is charged its share of cash operating and debt-service costs in exchange for the right to use the facility's loading capacity and is required to make periodic cash advances to DTA to fund such costs.

        The Company holds a 35% ownership interest in Tenaska Trailblazer Partners, LLC ("Tenaska"), the developer of the Trailblazer Energy Center, a fossil-fuel-based electric power plant near Sweetwater, Texas. The plant, fueled by low sulfur coal, will capture and store carbon dioxide for enhanced oil recovery applications. Additional future payments are due upon the achievement of project milestones to maintain the Company's interest. The Company made a milestone payment of $5.5 million in 2011. The Company will also pay 35% of the future development

F-21

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

costs of the project, not to exceed $12.5 million without prior approval from the Company. The receivables for these development costs, shown above, are reflected in the consolidated balance sheets in other noncurrent assets, as the development costs will either be reimbursed when the project receives construction financing, or they will be considered an additional capital contribution, with ownership percentages adjusted accordingly.

        In January 2011, the Company purchased a 38% ownership interest in Millennium Bulk Terminals-Longview, LLC ("Millennium"), the owner of a brownfield bulk commodity terminal on the Columbia River near Longview, Washington, for $25.0 million, plus additional future consideration upon the completion of certain project milestones. Millennium continues to work on obtaining the required approvals and necessary permits to complete dredging and other upgrades to enable coal, alumina and cementitious material shipments through the terminal. The Company will control 38% of the terminal's throughput and storage capacity, in order to facilitate export shipments of coal off the west coast of the United States.

        In July 2011, the Company purchased a 33% membership interest in the Tongue River Holding Company, LLC ("Tongue River") joint venture. Tongue River will develop and construct a railway line near Miles City, Montana and the Company's Otter Creek reserves. The Company has the right, upon the receipt of permits and approval for construction or under other prescribed circumstances, to require the other investors to purchase all of the Company's units in the venture at an amount equal to the capital contributions made by the Company at that time, less any distributions received.

        Under development financing agreements with certain investees, the Company may be required to make future contingent payments of up to $74.4 million, including milestone payments. The Company's obligation to make these payments, as well as the timing of any payments required, is contingent upon a number of factors, including project development progress, receipt of permits and construction financing.

        Summarized financial information of the Company's equity method investees follows:

	December 31
	2011		2010		2009
	(In thousands)
Condensed combined income statement information:
Revenues	$	184,358	$	172,933	$	166,152
Gross profit		19,495		25,203		15,426
Income from operations		13,180		20,243		1,611
Net income (loss)		6,788		16,015		(1,797	)
Condensed combined balance sheet information:
Current assets	$	94,644	$	48,202
Noncurrent assets		331,848		276,125
Total assets	$	426,492	$	324,327
Current liabilities	$	51,674	$	39,237
Noncurrent liabilities		120,494		99,350
Equity		254,163		185,639
Noncontrolling interest		161		101
Total liabilities and equity	$	426,492	$	324,327

F-22

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

9.    Inventories

        Inventories consist of the following:

	December 31
	2011		2010
	(In thousands)
Coal	$	206,517	$	115,647
Repair parts and supplies		163,527		119,969
Work-in-process		7,446		—
	$	377,490	$	235,616

        The work-in-process is related to the Company's ADDCAR subsidiary acquired with ICG, which manufactures and sells its patented highwall mining system. The repair parts and supplies are stated net of an allowance for slow-moving and obsolete inventories of $13.1 million and $12.7 million at December 31, 2011 and 2010, respectively.

10.    Derivative Instruments

Diesel fuel price risk management

        The Company is exposed to price risk with respect to diesel fuel purchased for use in its operations. The Company anticipates purchasing approximately 80 to 90 million gallons of diesel fuel for use in its operations during 2012. To reduce the volatility in the price of diesel fuel for its operations, the Company uses forward physical diesel purchase contracts, as well as heating oil swaps and purchased call options. At December 31, 2011, the Company had protected the price of approximately 82% of its expected purchases for fiscal year 2012.

        At December 31 2011, the Company held heating oil swaps and purchased call options for approximately 69 million gallons for the purpose of managing the price risk associated with future diesel purchases. Since the changes in the price of heating oil highly correlate to changes in the price of the hedged diesel fuel purchases, the heating oil swaps and purchased call options qualify for cash flow hedge accounting.

        The Company also purchased heating oil call options to hedge the fuel surcharges on its barge and rail shipments that cover increases in diesel fuel prices. These positions reduce the Company's risk of cash flow fluctuations related to these surcharges but the positions are not accounted for as hedges. At December 31, 2011, Company held purchased call options for approximately 19.1 million gallons for the purpose of managing the fluctuations in cash flows associated with fuel surcharges on future shipments.

Coal risk management positions

        The Company may sell or purchase forward contracts, swaps and options in the over-the-counter coal market in order to manage its exposure to coal prices. The Company has exposure to the risk of fluctuating coal prices related to forecasted sales or purchases of coal or to the risk of changes in the fair value of a fixed price physical sales contract. Certain derivative contracts may be designated as hedges of these risks.

        At December 31, 2011, the Company held derivatives for risk management purposes that are expected to settle in the following years :

	2012		2013		2014		2015
(Tons in thousands)
Coal sales		2,416		1,117		1,440		720
Coal purchases		254		—		—		—

F-23

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Coal trading positions

        The Company may sell or purchase forward contracts, swaps and options in the over-the-counter coal market for trading purposes. The Company is exposed to the risk of changes in coal prices on the value of its coal trading portfolio. The estimated future realization of the value of the trading portfolio is $2.6 million of losses in 2012 and $1.8 million of losses in 2013.

Tabular derivatives disclosures

        The Company's contracts with certain of its counterparties allow for the settlement of contracts in an asset position with contracts in a liability position in the event of default or termination. Such netting arrangements reduce the Company's credit exposure related to these counterparties. For classification purposes, the Company records the net fair value of all the positions with a given counterparty as a net asset or liability in the consolidated balance sheets. The amounts shown in the table below represent the fair value position of individual contracts, regardless of the net position presented in the accompanying consolidated balance sheets. The fair value and location of derivatives reflected in the accompanying consolidated balance sheets are as follows:

	December 31, 2011								December 31, 2010
Fair Value of Derivatives (In thousands)	Asset Derivative			Liability Derivative					Asset Derivative			Liability Derivative
Derivatives Designated as Hedging Instruments
Heating oil — diesel purchases	$	8,997		$	—				$	13,475		$	—
Coal		1,109			—					2,009			(2,350	)
Total		10,106			—					15,484			(2,350	)
Derivatives Not Designated as Hedging Instruments
Heating oil — fuel surcharges		1,797			—					—			—
Coal — held for trading purposes		15,505			(19,927	)				34,445			(24,087	)
Coal		14,855			(6,035	)				1,139			(912	)
Total		32,157			(25,962	)				35,584			(24,999	)
Total derivatives		42,263			(25,962	)				51,068			(27,349	)
Effect of counterparty netting		(18,134	)		18,134					(22,402	)		22,402
Net derivatives as classified in the balance sheets	$	24,129		$	(7,828	)	$	16,301	$	28,666		$	(4,947	)	$	23,719

		December 31
		2011			2010
Net derivatives as reflected on the balance sheets
Heating oil	Other current assets	$	10,794		$	13,475
Coal	Coal derivative assets		13,335			15,191
	Coal derivative liabilities		(7,828	)		(4,947	)
		$	16,301		$	23,719

        The Company had a current asset for the right to reclaim cash collateral of $12.4 million and $10.3 million at December 31, 2011 and December 31, 2010, respectively. These amounts are not included with the derivatives

F-24

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

presented in the table above and are included in "other current assets" in the accompanying consolidated balance sheets.

        The effects of derivatives on measures of financial performance are as follows:

Year Ended December 31, (In thousands)
	Gain on Derivatives Used in Fair Value Hedge Relationships									Hedged Items in Fair Value Hedge Relationships	Loss on Hedged Items In Fair Value Hedge Relationships
Derivatives used in Fair Value Hedging Relationships
	2011			2010			2009				2011			2010			2009
	(In thousands)										(In thousands)
Coal	$	—	(3)	$	—	(3)	$	2,586	(3)	Firm commitments	$	—	(3)	$	—	(3)	$	(2,586	)(3)
Derivatives used in Cash Flow Hedging Relationships	Gain (Loss) Recognized in OCI (Effective Portion)										Gains (Losses) Reclassified from OCI into Income (Effective Portion)
	2011			2010			2009				2011			2010			2009
Heating oil — diesel purchases	$	1,294		$	(149	)	$	10,309			$	14,866	(2)	$	437	(2)	$	(49,055	)(2)
Coal sales		4,923			(4,714	)		(7,441	)			1,572	(1)		(1,602	)(1)		(6,999	)(1)
Coal purchases		(2,009	)		5,145			1,089				—	(2)		(1,202	)(2)		(13,181	)(2)
Totals	$	4,208		$	282		$	3,957			$	16,438		$	(2,367	)	$	(69,235	)
Derivatives used in Cash Flow Hedging Relationships	Gain (Loss) Recognized in Income (Ineffective Portion and Amount Excluded from Effectiveness Testing)
	2011			2010			2009
Heating oil — diesel purchases	$	—		$	—		$	—
Coal sales		—			—			—
Coal purchases		—			—			—
Totals	$	—		$	—		$	—
Derivatives Not Designated as Hedging Instruments											Gain (Loss)
											2011			2010			2009
Coal — unrealized											$	6,438	(3)	$	(10,991	)(3)	$	9,673	(3)
Coal — realized											$	(7	)(4)	$	4,542	(4)	$	—	(4)
Heating oil — fuel surcharges — unrealized											$	(2,906	)(4)	$	—	(4)	$	—	(4)

Location in Statement of Income:
(1) — Revenues
(2) — Cost of sales
(3)  — Change in fair value of coal derivatives and coal trading activities, net
(4) — Other operating income, net

        The Company recognized net unrealized and realized losses of $3.5 million during the year ended December 31, 2011 and net unrealized and realized gains of $2.1 million and $2.4 million, during the years ended December 31, 2010 and 2009, respectively, related to its trading portfolio (including derivative and non-derivative contracts). These balances are included in the caption "Change in fair value of coal derivatives and coal trading activities, net" in the accompanying consolidated statements of income and are not included in the previous table.

F-25

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

        During the next twelve months, based on fair values at December 31, 2011, gains on derivative contracts designated as hedge instruments in cash flow hedges of approximately $9.2 million are expected to be reclassified from other comprehensive income into earnings.

11.    Accrued Expenses and Other Current Liabilities

        Accrued expenses and other current liabilities consist of the following:

	December 31
	2011		2010
	(In thousands)
Payroll and employee benefits	$	65,323	$	51,327
Taxes other than income taxes		133,331		107,969
Interest		55,266		52,843
Acquired sales contracts (see Note 6)		38,441		5,615
Workers' compensation (see Note 15)		11,666		6,659
Asset retirement obligations (see Note 14)		27,119		8,862
Other		17,061		12,136
	$	348,207	$	245,411

12.    Taxes

        The Company is subject to U.S. federal income tax as well as income tax in multiple state jurisdictions. The tax years 2005 through 2011 remain open to examination for U.S. federal income tax matters and 1998 through 2011 remain open to examination for various state income tax matters.

        Significant components of the provision for (benefit from) income taxes are as follows:

	Year Ended December 31
	2011			2010			2009
	(In thousands)
Current:
Federal	$	(20,164	)	$	34,304		$	21,295
State		1,212			2,283			864
Total current		(18,952	)		36,587			22,159
Deferred:
Federal		13,214			(18,506	)		(39,492	)
State		(1,851	)		(367	)		558
Total deferred		11,363			(18,873	)		(38,934	)
	$	(7,589	)	$	17,714		$	(16,775	)

F-26

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

        A reconciliation of the statutory federal income tax expense on the Company's pretax income to the actual provision for (benefit from) income taxes follows:

	Year Ended December 31
	2011			2010			2009
	(In thousands)
Income tax expense at statutory rate	$	46,933		$	61,800		$	8,888
Percentage depletion allowance		(61,971	)		(49,152	)		(29,463	)
State taxes, net of effect of federal taxes		(3,055	)		2,299			(61	)
Change in valuation allowance		2,416			(383	)		725
Other, net		8,088			3,150			3,136
	$	(7,589	)	$	17,714		$	(16,775	)

        In 2011, 2010 and 2009, compensatory stock options and other equity based compensation awards were exercised resulting in a tax expense (benefit) of $(0.4) million, $(0.8) million and $0.2 million, respectively. The tax benefit will be recorded in paid-in capital at such point in time when a cash tax benefit is recognized.

        Significant components of the Company's deferred tax assets and liabilities that result from carryforwards and temporary differences between the financial statement basis and tax basis of assets and liabilities are summarized as follows:

	December 31
	2011			2010
	(In thousands)
Deferred tax assets:
Alternative minimum tax credit carryforwards	$	151,404		$	170,592
Net operating loss carryforwards		324,393			102,355
Reclamation and mine closure		93,914			71,533
Advance royalties		—			38,557
Plant and equipment		—			19,846
Acquired sales contracts		44,717			20,120
Other, primarily accrued liabilities		171,715			90,412
Gross deferred tax assets		786,143			513,415
Valuation allowance		(2,831	)		(737	)
Total deferred tax assets		783,312			512,678
Deferred tax liabilities
Plant and equipment		1,566,769			—
Deferred development		67,728			76,690
Investment in tax partnerships		66,502			68,538
Other		17,015			13,669
Total deferred tax liabilities		1,718,014			158,897
Net deferred tax asset (liability)		(934,702	)		353,781
Current asset (liability)		42,051			(7,775	)
Non-current deferred tax asset (liability)	$	(976,753	)	$	361,556

F-27

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

        The Company has federal net operating loss carryforwards for regular income tax purposes of $779.1 million at December 31, 2011 that will expire between 2012 and 2031. The Company has an alternative minimum tax credit carryforward of $151.4 million at December 31, 2011, which has no expiration date and can be used to offset future regular tax in excess of the alternative minimum tax.

        During 2008, the Company reached a settlement with the IRS regarding the Company's treatment of the acquisition of the coal operations of Atlantic Richfield Company ("ARCO") and the simultaneous combination of the acquired ARCO operations and the Company's Wyoming operations into the Arch Western joint venture. The settlement did not result in a net change in deferred tax assets, but involved a re-characterization of deferred tax assets, including an increase in net operating loss carryforwards of $145.1 million and other amortizable assets which will provide additional tax deductions through 2013. A portion of these future cash tax benefits accrue to ARCO pursuant to the original purchase agreement, including $0.8 million, $1.3 million and $4.8 million paid in 2011, 2010 and 2009, respectively, that was recorded as goodwill.

        The Company has recorded a valuation allowance for a portion of its deferred tax assets that management believes, more likely than not, will not be realized. Management reassesses the ability to realize its deferred tax assets annually in the fourth quarter or when circumstances indicate that the ability to realize deferred tax assets has changed. In determining the appropriate valuation allowance, the assessment takes into account expected future taxable income and available tax planning strategies. This review resulted in increases (decreases) in the valuation allowance of $2.1 million, $(0.4) million and $0.7 million in 2011, 2010 and 2009, respectively. The valuation allowance relates to certain state and foreign net operating loss benefits.

        A reconciliation of the beginning and ending amounts of gross unrecognized tax benefits is as follows (in thousands):

Balance at January 1, 2009	$	4,878
Additions based on tax positions related to the current year		1,593
Additions for tax positions of prior years		205
Reductions for tax positions of prior years		(6	)
Balance at December 31, 2009		6,670
Additions based on tax positions related to the current year		1,493
Additions for tax positions of prior years		85
Reductions for tax positions of prior years		(3,830	)
Balance at December 31, 2010		4,418
Additions based on tax positions related to the current year		1,626
Additions for tax positions of prior years		2,754
Balance at December 31, 2011	$	8,798

        If recognized, the entire amount of the gross unrecognized tax benefits at December 31, 2011 would affect the effective tax rate.

        The Company recognizes interest and penalties accrued related to unrecognized tax benefits in income tax expense. The Company had accrued interest and penalties of $0.8 million and $0.6 million at December 31, 2011 and 2010, respectively, of which $0.2 million and $0.1 million was recognized as expense during 2011 and 2010, respectively. No gross unrecognized tax benefits are expected to be reduced in the next 12 months due to the expiration of the statute of limitations.

F-28

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

13.    Fair Values of Financial Instruments

        The hierarchy of fair value measurements prioritizes the inputs to valuation techniques used to measure fair value. The levels of the hierarchy, as defined below, give the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities and the lowest priority to unobservable inputs.

•

Level 1 is defined as observable inputs such as quoted prices in active markets for identical assets. Level 1 assets include available-for-sale equity securities and coal futures that are submitted for clearing on the New York Mercantile Exchange.

•

Level 2 is defined as observable inputs other than Level 1 prices. These include quoted prices for similar assets or liabilities in an active market, quoted prices for identical assets and liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. The Company's level 2 assets and liabilities include commodity contracts (coal and heating oil) with fair values derived from quoted prices in over-the-counter markets or from prices received from direct broker quotes.

•

Level 3 is defined as unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions. These include the Company's commodity option contracts (primarily coal and heating oil) valued using modeling techniques, such as Black-Scholes, that require the use of inputs, particularly volatility, that are rarely observable.

        The table below sets forth, by level, the Company's financial assets and liabilities that are recorded at fair value in the accompanying consolidated balance sheet:

	Fair Value at December 31, 2011
	Total		Level 1		Level 2		Level 3
	(In thousands)
Assets:
Investments in equity securities	$	7,540	$	7,540	$	—	$	—
Derivatives		24,129		12,361		1,450		10,318
Total assets	$	31,669	$	19,901	$	1,450	$	10,318
Liabilities:
Derivatives	$	7,828	$	—	$	3,721	$	4,107

        The Company's contracts with certain of its counterparties allow for the settlement of contracts in an asset position with contracts in a liability position in the event of default or termination. For classification purposes, the Company records the net fair value of all the positions with these counterparties as a net asset or liability. Each level in the table above displays the underlying contracts according to their classification in the accompanying consolidated balance sheet, based on this counterparty netting.

F-29

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

        The following table summarizes the change in the fair values of financial instruments categorized as level 3.

	Year Ended December 31, 2011
	(In thousands)
Balance, beginning of period	$	9,183
Realized and unrealized losses recognized in earnings, net		(16,727	)
Realized and unrealized losses recognized in other comprehensive income, net		(4,122	)
Purchases		23,867
Issuances		(2,160	)
Settlements		(3,830	)
Balance, end of period	$	6,211

        Net unrealized losses during the twelve months ended December 31, 2011 related to level 3 financial instruments held on December 31, 2011 were $13.1 million.

Fair Value of Long-Term Debt

        At December 31, 2011 and December 31, 2010, the fair value of the Company's senior notes and other long-term debt, including amounts classified as current, was $4.2 billion and $1.7 billion, respectively. Fair values are based upon observed prices in an active market when available or from valuation models using market information.

14.    Asset Retirement Obligations

        The Company's asset retirement obligations arise from the Federal Surface Mining Control and Reclamation Act of 1977 and similar state statutes, which require that mine property be restored in accordance with specified standards and an approved reclamation plan. The required reclamation activities to be performed are outlined in the Company's mining permits. These activities include reclaiming the pit and support acreage at surface mines, sealing portals at underground mines, and reclaiming refuse areas and slurry ponds.

        The following table describes the changes to the Company's asset retirement obligation liability:

	Year Ended December 31
	2011			2010
	(In thousands)
Balance at January 1 (including current portion)	$	343,119		$	310,409
Accretion expense		33,601			26,615
Obligations incurred or acquired		115,019			—
Adjustments to the liability from changes in estimates		11,176			8,934
Liabilities settled		(29,012	)		(2,839	)
Balance at December 31	$	473,903		$	343,119
Current portion included in accrued expenses		(27,119	)		(8,862	)
Noncurrent liability	$	446,784		$	334,257

        Liabilities settled of $29.0 million in 2011 related to reclamation activities at the Black Thunder mining complex related to a pit acquired with the Jacobs Ranch operations in 2009.

        As of December 31, 2011, the Company had $263.0 million in surety bonds outstanding and $420.5 million in self-bonding to secure reclamation obligations.

F-30

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

15.    Accrued Workers' Compensation

        The Company is liable under the Federal Mine Safety and Health Act of 1969, as subsequently amended, to provide for pneumoconiosis (occupational disease) benefits to eligible employees, former employees, and dependents. The Company is also liable under various states' statutes for occupational disease benefits. The Company currently provides for federal and state claims principally through a self-insurance program. The occupational disease benefit obligation represents the present value of the actuarially computed present and future liabilities for such benefits over the employees' applicable years of service.

        In addition, the Company is liable for workers' compensation benefits for traumatic injuries that are accrued as injuries are incurred. Traumatic claims are either covered through self-insured programs or through state-sponsored workers' compensation programs.

        Workers' compensation expense consists of the following components:

	Year Ended December 31
	2011			2010			2009
	(In thousands)
Self-insured occupational disease benefits:
Service cost	$	2,059		$	727		$	531
Interest cost		1,799			675			558
Net amortization		(493	)		(1,860	)		(2,879	)
Total occupational disease		3,365			(458	)		(1,790	)
Traumatic injury claims and assessments		16,979			9,263			8,904
Total workers' compensation expense	$	20,344		$	8,805		$	7,114

        The increase in total workers' compensation expense for the year ended 2011 is related to the acquisition of ICG.

        The reconciliation of changes in the benefit obligation of the occupational disease liability is as follows:

	December 31
	2011			2010
	(In thousands)
Beginning of year obligation	$	17,412		$	9,702
Service cost		2,059			727
Interest cost		1,799			675
Actuarial loss		7,081			6,993
Benefit and administrative payments		(1,097	)		(685	)
Acquisition of ICG		26,930			—
Net obligation at end of year	$	54,184		$	17,412

        At December 31, 2011 and 2010, accumulated losses of $5.5 million and accumulated gains of $2.0 million, respectively, were not yet recognized in occupational disease cost and were recorded in accumulated other comprehensive income. The expected accumulated loss that will be amortized from accumulated other comprehensive income into occupational disease cost in 2012 is $1.1 million.

F-31

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

        The following table provides the assumptions used to determine the projected occupational disease obligation:

	Year Ended December 31
	2011			2010			2009
Weighted average assumptions:
Discount rate		5.10	%		5.96	%		6.11	%
Cost escalation rate		3.00	%		3.00	%		3.00	%

        Summarized below is information about the amounts recognized in the accompanying consolidated balance sheets for workers' compensation benefits:

	December 31
	2011		2010
	(In thousands)
Occupational disease costs	$	54,184	$	17,412
Traumatic and other workers' compensation claims		29,430		24,537
Total obligations		83,614		41,949
Less amount included in accrued expenses		11,666		6,659
Noncurrent obligations	$	71,948	$	35,290

        As of December 31, 2011, the Company had $60.1 million in surety bonds and letters of credit outstanding to secure workers' compensation obligations.

16.    Employee Benefit Plans

Defined Benefit Pension and Other Postretirement Benefit Plans

        The Company provides funded and unfunded non-contributory defined benefit pension plans covering certain of its salaried and hourly employees. Benefits are generally based on the employee's age and compensation. The Company funds the plans in an amount not less than the minimum statutory funding requirements or more than the maximum amount that can be deducted for U.S. federal income tax purposes.

        The Company also currently provides certain postretirement medical and life insurance coverage for eligible employees. Generally, covered employees who terminate employment after meeting eligibility requirements are eligible for postretirement coverage for themselves and their dependents. The salaried employee postretirement benefit plans are contributory, with retiree contributions adjusted annually, and contain other cost-sharing features such as deductibles and coinsurance. The Company's current funding policy is to fund the cost of all postretirement benefits as they are paid.

        Employees acquired with the ICG acquisition were brought over in their existing plan. Subsequently, the terms of the plan were amended to change vesting periods, coverage caps, and eligible ages, resulting in a reduction of the benefit obligation of $55.5 million.

        During 2009, the Company notified participants of the retiree medical plan of a plan change increasing the retirees' responsibility for medical costs. This change resulted in a remeasurement of the postretirement benefit obligation, which included a decrease in the discount rate from 6.85% to 5.68%. The remeasurement resulted in a decrease in the liability of $21.0 million, with a corresponding increase to other comprehensive income, and will result in future reductions in costs under the plan.

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

        Obligations and Funded Status.    Summaries of the changes in the benefit obligations, plan assets and funded status of the plans are as follows:

	Pension Benefits						Other Postretirement Benefits
	2011			2010			2011			2010
	(In thousands)
CHANGE IN BENEFIT OBLIGATIONS
Benefit obligations at January 1	$	297,707		$	280,693		$	39,633		$	46,445
Service cost		16,490			15,870			3,917			1,509
Interest cost		16,253			15,822			3,279			2,083
Plan amendments		(3,235	)		(92	)		(55,542	)		—
Benefits paid		(18,848	)		(15,924	)		(1,669	)		(1,845	)
Acquisition of ICG		—			—			48,441			—
Other-primarily actuarial loss (gain)		25,584			1,338			7,070			(8,559	)
Benefit obligations at December 31	$	333,951		$	297,707		$	45,129		$	39,633
CHANGE IN PLAN ASSETS
Value of plan assets at January 1	$	247,713		$	211,899		$	—		$	—
Actual return on plan assets		9,443			34,401			—			—
Employer contributions		46,766			17,337			1,669			1,845
Benefits paid		(18,848	)		(15,924	)		(1,669	)		(1,845	)
Value of plan assets at December 31	$	285,074		$	247,713		$	—		$	—
Accrued benefit cost	$	(48,877	)	$	(49,994	)	$	(45,129	)	$	(39,633	)
ITEMS NOT YET RECOGNIZED AS A COMPONENT OF NET PERIODIC BENEFIT COST
Prior service credit (cost)	$	1,736		$	(1,310	)	$	62,920		$	9,742
Accumulated gain (loss)		(68,302	)		(39,099	)		1,795			11,965
	$	(66,566	)	$	(40,409	)	$	64,715		$	21,707
BALANCE SHEET AMOUNTS
Current liability	$	(633	)	$	(840	)	$	(2,820	)	$	(1,840	)
Noncurrent liability	$	(48,244	)	$	(49,154	)	$	(42,309	)	$	(37,793	)
	$	(48,877	)	$	(49,994	)	$	(45,129	)	$	(39,633	)

Pension Benefits

        The accumulated benefit obligation for all pension plans was $314.7 million and $280.4 million at December 31, 2011 and 2010, respectively. The accumulated benefit obligation differs from the benefit obligation in that it includes no assumption about future compensation levels.

        The benefit obligation and the accumulated benefit obligation for the Company's unfunded pension plan were $8.2 million and $7.1 million, respectively, at December 31, 2011.

        The prior service credit and net loss that will be amortized from accumulated other comprehensive income into net periodic benefit cost in 2012 are $0.1 million and $14.3 million, respectively.

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Other Postretirement Benefits

        The prior service credit and net gain that will be amortized from accumulated other comprehensive income into net periodic benefit cost in 2012 is $12.0 million and $0.4 million, respectively.

        Components of Net Periodic Benefit Cost.    The following table details the components of pension and other postretirement benefit costs.

	Pension Benefits									Other Postretirement Benefits
Year Ended December 31,	2011			2010			2009			2011			2010			2009
	(In thousands)
Service cost	$	16,490		$	15,870		$	13,444		$	3,917		$	1,509		$	2,954
Interest cost		16,253			15,822			15,946			3,279			2,083			3,667
Expected return on plan assets*		(21,812	)		(19,392	)		(17,719	)		—			—			—
Amortization of prior service cost (credit)		(189	)		173			193			(2,364	)		(2,364	)		2,161
Amortization of other actuarial losses (gains)		8,748			7,130			3,967			(3,100	)		(2,918	)		(2,897	)
Curtailments		—			—			585			—			—			—
Net benefit cost	$	19,490		$	19,603		$	16,416		$	1,732		$	(1,690	)	$	5,885

*

The Company does not fund its other postretirement benefit obligations.

        The differences generated from changes in assumed discount rates and returns on plan assets are amortized into earnings over a five-year period.

        Assumptions.    The following table provides the assumptions used to determine the actuarial present value of projected benefit obligations at December 31.

	Pension Benefits						Other Postretirement Benefits
	2011			2010			2011			2010
Weighted average assumptions:
Discount rate		4.91	%		5.71	%		4.52	%		5.23	%
Rate of compensation increase		3.39	%		3.39	%		N/A			N/A

        The following table provides the assumptions used to determine net periodic benefit cost for years ended December 31.

	Pension Benefits									Other Postretirement Benefits
	2011			2010			2009			2011			2010			2009
Weighted average assumptions:
Discount rate		5.71	%		5.97	%		6.85	%		5.23	%		5.67	%	6.85%/5.68%
Rate of compensation increase		3.39	%		3.39	%		3.39	%		N/A			N/A		N/A
Expected return on plan assets		8.50	%		8.50	%		8.50	%		N/A			N/A		N/A

        The Company establishes the expected long-term rate of return at the beginning of each fiscal year based upon historical returns and projected returns on the underlying mix of invested assets. The Company utilizes modern portfolio theory modeling techniques in the development of its return assumptions. This technique projects rates of return that can be generated through various asset allocations that lie within the risk tolerance set forth by members of the Company's pension committee (the "Pension Committee"). The risk assessment provides a link

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

between a pension's risk capacity, management's willingness to accept investment risk and the asset allocation process, which ultimately leads to the return generated by the invested assets.

        The health care cost trend rate assumed for 2012 is 7.7% and is expected to reach an ultimate trend rate of 4.5% by 2028. A one-percentage-point increase in the health care cost trend rate would have increased the postretirement benefit obligation at December 31, 2011 by $0.5 million. A one-percentage-point decrease in the health care cost trend rate would have decreased the postretirement benefit obligation at December 31, 2011 by $0.4 million. The effect of these changes would have had an insignificant impact on the net periodic postretirement benefit costs.

Plan Assets

        The Pension Committee is responsible for overseeing the investment of pension plan assets. The Pension Committee is responsible for determining and monitoring appropriate asset allocations and for selecting or replacing investment managers, trustees and custodians. The pension plan's current investment targets are 65% equity, 30% fixed income securities and 5% cash. The Pension Committee reviews the actual asset allocation in light of these targets on a periodic basis and rebalances among investments as necessary. The Pension Committee evaluates the performance of investment managers as compared to the performance of specified benchmarks and peers and monitors the investment managers to ensure adherence to their stated investment style and to the plan's investment guidelines.

        The Company's pension plan assets at December 31, 2011 and 2010, respectively, are categorized below according to the fair value hierarchy as defined in Note 13, "Fair Values of Financial Instruments":

	Total				Level 1				Level 2				Level 3
	2011		2010		2011		2010		2011		2010		2011		2010
	(In thousands)
Equity securities:(A)
U.S. small-cap	$	11,178	$	10,647	$	11,178	$	10,647	$	—	$	—	$	—	$	—
U.S. mid-cap		50,264		46,851		23,474		21,163		26,790		25,688		—		—
U.S. large-cap		91,561		77,632		44,820		38,397		46,741		39,235		—		—
Non-U.S.		22,509		24,995		—		—		22,509		24,995		—		—
Fixed income securities:
U.S. government securities(B)		13,454		3,053		12,738		2,492		716		561		—		—
Non-U.S. government securities(C)		2,968		3,469		—		—		2,968		3,469		—		—
U.S. government asset and mortgage backed securities(D)		800		1,073		—		—		800		1,073		—		—
Corporate fixed income(E)		14,004		13,737		—		—		14,004		13,737		—		—
State and local government securities(F)		18,416		13,679		—		—		18,416		13,679		—		—
Other fixed income(G)		51,470		45,628		—		—		51,470		45,628		—		—
Short-term investments(H)		8,029		6,110		—		—		8,029		6,110		—		—
Other investments(I)		421		839		—		—		421		839		—		—
Total	$	285,074	$	247,713	$	92,210	$	72,699	$	192,864	$	175,014	$	—	$	—

(A)

Equity securities includes investments in 1) common stock, 2) preferred stock and 3) mutual funds. Investments in common and preferred stocks are valued using quoted market prices multiplied by the number

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

of shares owned. Investments in mutual funds are valued at the net asset value per share multiplied by the number of shares held as of the measurement date and are traded on listed exchanges.

(B)

U.S. government securities includes agency and treasury debt. These investments are valued using dealer quotes in an active market.

(C)

Non-U.S. government securities includes debt securities issued by foreign governments and are valued utilizing a price spread basis valuation technique with observable sources from investment dealers and research vendors.

(D)

U.S. government asset and mortgage backed securities includes government-backed mortgage funds which are valued utilizing an income approach that includes various valuation techniques and sources such as discounted cash flows models, benchmark yields and securities, reported trades, issuer trades and/or other applicable data.

(E)

Corporate fixed income is primarily comprised of corporate bonds and certain corporate asset-backed securities that are denominated in the U.S. dollar and are investment-grade securities. These investments are valued using dealer quotes.

(F)

State and local government securities include different U.S. state and local municipal bonds and asset backed securities, these investments are valued utilizing a market approach that includes various valuation techniques and sources such as value generation models, broker quotes, benchmark yields and securities, reported trades, issuer trades and/or other applicable data.

(G)

Other fixed income investments are actively managed fixed income vehicles that are valued at the net asset value per share multiplied by the number of shares held as of the measurement date.

(H)

Short-term investments include governmental agency funds, government repurchase agreements, commingled funds, and pooled funds and mutual funds. Governmental agency funds are valued utilizing an option adjusted spread valuation technique and sources such as interest rate generation processes, benchmark yields and broker quotes. Investments in governmental repurchase agreements, commingled funds and pooled funds and mutual funds are valued at the net asset value per share multiplied by the number of shares held as of the measurement date.

(I)

Other investments includes cash, forward contracts, derivative instruments, credit default swaps, interest rate swaps and mutual funds. Investments in interest rate swaps are valued utilizing a market approach that includes various valuation techniques and sources such as value generation models, broker quotes in active and non-active markets, benchmark yields and securities, reported trades, issuer trades and/or other applicable data. Forward contracts and derivative instruments are valued at their exchange listed price or broker quote in an active market. The mutual funds are valued at the net asset value per share multiplied by the number of shares held as of the measurement date and are traded on listed exchanges.

        Cash Flows.    In order to achieve a desired funded status, the Company expects to make contributions of $24.5 million to the pension plans in 2012.

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

        The following represents expected future benefit payments, which reflect expected future service, as appropriate:

	Pension Benefits		Other Postretirement Benefits
	(In thousands)
2012	$	17,898	$	3,411
2013		20,854		3,787
2014		22,803		4,060
2015		22,492		4,406
2016		26,185		4,694
Years 2017-2021		164,788		25,122
	$	275,020	$	45,480

Other Plans

        The Company sponsors savings plans which were established to assist eligible employees provide for their future retirement needs. The Company's expense, representing its contributions to the plans, was $25.9 million, $18.1million and $15.9 million for the years ended December 31, 2011, 2010 and 2009, respectively.

17.    Capital Stock

        On March 14, 2006, the Company filed a registration statement on Form S-3 with the SEC. The registration statement allows the Company to offer, from time to time, an unlimited amount of debt securities, preferred stock, depositary shares, purchase contracts, purchase units, common stock and related rights and warrants.

Common Stock

        On June 8, 2011, the Company sold 48 million shares of its common stock at a public offering price of $27.00 per share. The $1.25 billion in net proceeds from the issuance were used to finance the acquisition of ICG. On July 8, 2011, the Company issued an additional 0.7 million shares of its common stock under the same terms and conditions to cover underwriters' over-allotments for net proceeds of $18.4 million.

        On July 31, 2009, the Company sold 17 million shares of its common stock at a public offering price of $17.50 per share and on August 6, 2009, the Company issued an additional 2.55 million shares of its common stock under the same terms and conditions to cover underwriters' over-allotments. The net proceeds received from the issuance of common stock were $326.5 million, which was used primarily to finance the purchase of the Jacobs Ranch mining complex in 2009.

Stock Repurchase Plan

        The Company's share repurchase program allows for the purchase of up to 14,000,000 shares of the Company's common stock. At December 31, 2011, 10,925,800 shares of common stock were available for repurchase under the plan. There were no purchases made under the plan during 2011, 2010 or 2009. There is no expiration date on the program. Any future repurchases under the plan will be made at management's discretion and will depend on market conditions and other factors.

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

18.    Stock Based Compensation and Other Incentive Plans

        Under the Company's Stock Incentive Plan (the "Incentive Plan"), 18,000,000 shares of the Company's common stock are reserved for awards to officers and other selected key management employees of the Company. The Incentive Plan provides the Board of Directors with the flexibility to grant stock options, stock appreciation rights, restricted stock awards, restricted stock units, performance stock or units, merit awards, phantom stock awards and rights to acquire stock through purchase under a stock purchase program ("Awards"). Awards the Board of Directors elects to pay out in cash do not count against the 18,000,000 shares authorized in the Incentive Plan. The Incentive Plan calls for the adjustment of shares awarded under the plan in the event of a split.

        As of December 31, 2011, the Company had stock options, restricted stock and restricted stock units outstanding under the Incentive Plan.

Stock Options

        Stock options are granted at a price equal to the closing market price of the Company's common stock on the date of grant and are generally subject to vesting provisions of at least one year from the date of grant. Information regarding stock option activity under the Incentive Plan follows for the year ended December 31, 2011:

	Common Shares			Weighted Average Exercise Price		Aggregate Intrinsic Value		Average Contract Life
	(In thousands)					(In thousands)
Options outstanding at January 1		4,544		$	25.18
Granted		728			32.18
Exercised		(199	)		11.61
Canceled		(88	)		23.74
Expired		(32	)		52.69
Options outstanding at December 31		4,953			26.60	$	4,107		5.76
Options exercisable at December 31		3,157			27.59		3,887		4.35

        The aggregate intrinsic value of options exercised during the years ended December 31, 2011, 2010 and 2009 was $2.6 million, $3.0 million and $0.1 million, respectively.

        Information regarding changes in stock options outstanding and not yet vested and the related grant-date fair value under the Incentive Plan follows for the year ended December 31, 2011:

	Common Shares			Weighted Average Grant-Date Fair Value
	(In thousands)
Unvested options at January 1		1,901		$	10.61
Granted		728			14.18
Vested		(746	)		13.28
Canceled		(87	)		10.35
Unvested options at December 31		1,796			10.96

        Compensation expense related to stock options for the years ended December 31, 2011, 2010 and 2009 was $8.8 million, $10.6 million and $11.8 million, respectively. As of December 31, 2011, there was $8.2 million of unrecognized compensation cost related to the unvested stock options. The total grant-date fair value of options vested during the years ended December 31, 2011, 2010 and 2009 was $9.9 million, $10.6 million and $9.1 million, respectively. The options provide for the continuation of vesting for retirement-eligible recipients that meet certain criteria. The expense for these options is recognized through the date that the employee first becomes

F-38

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

eligible to retire and is no longer required to provide service to earn part or all of the award. The majority of the cost relating to the stock-based compensation plans is included primarily in selling, general and administrative expenses in the accompanying consolidated statements of income.

        Weighted average assumptions used in the Black-Scholes option pricing model for granted options follow:

	Year Ended December 31
	2011			2010			2009
Weighted average grant-date fair value per share of options granted	$	14.18		$	9.43		$	6.63
Assumptions (weighted average):
Risk-free interest rate		1.92	%		2.16	%		1.75	%
Expected dividend yield		1.25	%		1.99	%		2.56	%
Expected volatility		57.4	%		57.1	%		69.3	%
Expected life (in years)		4.5			4.5			4.5

        Expected volatilities are based on historical stock price movement and implied volatility from traded options on the Company's stock. The expected life of the option was determined based on historical exercise activity. Most options granted vest over a period of four years.

Restricted Stock and Restricted Stock Unit Awards

        The Company may issue restricted stock and restricted stock units, which require no payment from the employee. Restricted stock cliff-vests at various dates and restricted stock units typically vest ratably over three years. Compensation expense is based on the fair value on the grant date and is recorded ratably over the vesting period. During the vesting period, the employee receives cash compensation equal to the amount of dividends that would have been paid on the underlying shares.

        Information regarding restricted stock and restricted stock unit activity and weighted average grant-date fair value follows for the year ended December 31, 2011:

	Restricted Stock					Restricted Stock Units
	Common Shares			Weighted Average Grant-Date Fair Value		Common Shares			Weighted Average Grant-Date Fair Value
	(In thousands)					(In thousands)
Outstanding at January 1		74		$	24.69		54		$	52.69
Granted		140			30.42		—			—
Vested		(27	)		39.77		(27	)		52.69
Canceled		(5	)		32.49		—			—
Outstanding at December 31		182			26.68		27			52.69

        The weighted average fair value of restricted stock granted during 2010 and 2009 was $22.03 and $14.05, respectively. There were no restricted stock units granted during 2010 or 2009. The total grant-date fair value of restricted stock that vested during 2011, 2010 and 2009 was $1.1 million, $0.4 million and $1.5 million, respectively. The total grant-date fair value of restricted stock units that vested during 2011 and 2009 was $1.4 million and $0.4 million, respectively. There were no restricted stock units that vested during 2010. Unearned compensation of $3.4 million will be recognized over the remaining vesting period of the outstanding restricted stock and restricted stock units. The Company recognized expense of approximately $2.1 million, $1.1 million and $1.7 million related to restricted stock and restricted stock units for the years ended December 31, 2011, 2010 and 2009, respectively, primarily in selling, general and administrative expenses.

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Long-Term Incentive Compensation

        The Company has a long-term incentive program that allows for the award of performance units. The total number of units earned by a participant is based on financial and operational performance measures, and may be paid out in cash or in shares of the Company's common stock. The Company recognizes compensation expense over the three year term of the grant. The liabilities are remeasured quarterly. The Company recognized $2.7 million, $3.8 million and $2.6 million for the years ended December 31, 2011, 2010 and 2009, respectively. The expense is included primarily in selling, general and administrative expenses in the accompanying consolidated statements of income. Amounts accrued under the plan were $9.6 million and $6.4 million at December 31, 2011 and 2010, respectively.

Deferred Compensation Plan

        The Company maintains a deferred compensation plan that allows eligible employees to defer receipt of compensation until the dates elected by the participant. Participants in the plan may defer up to 85% of their base salaries and up to 100% of their annual incentive awards. The plan also allows participants to defer receipt of up to 100% of the shares under any restricted stock unit or performance-contingent stock awards. The amounts deferred are invested in accounts that mirror the gains and losses of a number of different investment funds, including a hypothetical investment in shares of the Company's common stock. Participants are always vested in their deferrals to the plan and any related earnings. The Company has established a grantor trust to fund the obligations under the plan. The trust has purchased corporate-owned life insurance to offset these obligations. The net cash surrender values of the policies of $35.8 million and $40.7 million at December 31, 2011 and 2010, respectively, are included in other noncurrent assets in the accompanying consolidated balance sheets. The participants have an unsecured contractual commitment by the Company to pay the amounts due under the plan. Any assets placed in trust by the Company to fund future obligations of the plan are subject to the claims of creditors in the event of insolvency or bankruptcy, and participants are general creditors of the company as to their deferred compensation in the plans.

        Under the plan, the Company credits each participant's account with the number of units equal to the number of shares or units that the participant could purchase or receive with the amount of compensation deferred, based upon the fair market value of the underlying investment on that date. The amount the employee will receive from the plan will be based on the number of units credited to each participant's account, valued on the basis of the fair market value of an equivalent number of shares or units of the underlying investment on that date. The liability under the plan was $32.7 million at December 31, 2011 and $38.5 million at December 31, 2010.

        The Company's net income (expense) related to the deferred compensation plan for the years ended December 31, 2011, 2010 and 2009 was $6.2 million, $(2.8) million and $4.1 million, respectively, most of which is included in selling, general and administrative expenses in the accompanying consolidated statements of income.

19.    Risk Concentrations

Credit Risk and Major Customers

        The Company has a formal written credit policy that establishes procedures to determine creditworthiness and credit limits for trade customers and counterparties in the over-the-counter coal market. Generally, credit is extended based on an evaluation of the customer's financial condition. Collateral is not generally required, unless credit cannot be established. Credit losses are provided for in the financial statements and historically have been minimal.

        The Company markets its steam coal principally to electric utilities in the United States and its metallurgical coal to domestic and foreign steel producers. Revenues from export sales were $920.0 million, $471.5 million and $194.4 million for the years ended December 31, 2011, 2010 and 2009, respectively. The increasing export sales are primarily the result of an increase in metallurgical-quality coal sales volumes, although steam coal exports also increased. As of December 31, 2011 and 2010, accounts receivable from electric utilities located in the United

F-40

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

States totaled $261.2 million and $183.1 million, respectively, or 69% and 88% of total trade receivables, respectively. As of December 31, 2011 and 2010, accounts receivable from sales of metallurgical-quality coal totaled $117.4 million and $24.9 million, respectively, or 31% and 12%, of total trade receivables, respectively.

        The Company uses shipping destination as the basis for attributing revenue to individual countries. The Company's foreign revenues by geographical location for the year ended December 31, 2011, follows:

	December 31, 2011
	(In thousands)
Europe	$	427,514
South America		120,842
North America		97,255
Asia		61,308
Brokered sales		213,087
Total	$	920,006

        The Company is committed under long-term contracts to supply steam coal that meets certain quality requirements at specified prices. These prices are generally adjusted based on indices. Quantities sold under some of these contracts may vary from year to year within certain limits at the option of the customer. The Company sold approximately 156.9 million tons of coal in 2011. Approximately 72% of this tonnage (representing approximately 57% of the Company's revenue) was sold under long-term contracts (contracts having a term of greater than one year). Long-term contracts range in remaining life from one to nine years. Sales (including spot sales) to the Company's largest customer, Tennessee Valley Authority, were $266.8 million, $301.4 million and $278.8 million for the years ended December 31, 2011, 2010 and 2009, respectively.

Third-party sources of coal

        The Company uses independent contractors to mine coal at certain mining complexes. The Company also purchases coal from third parties that it sells to customers. Factors beyond the Company's control could affect the availability of coal produced for or purchased by the Company. Disruptions in the quantities of coal produced for or purchased by the Company could impair its ability to fill customer orders or require it to purchase coal from other sources at prevailing market prices in order to satisfy those orders.

Transportation

        The Company depends upon barge, rail, truck and belt transportation systems to deliver coal to its customers. Disruption of these transportation services due to weather-related problems, mechanical difficulties, strikes, lockouts, bottlenecks, and other events could temporarily impair the Company's ability to supply coal to its customers, resulting in decreased shipments. In the past, disruptions in rail service have resulted in missed shipments and production interruptions.

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

20.    Earnings per Common Share

        The following table provides the basis for earnings per share calculations by reconciling basic and diluted weighted average shares outstanding:

	Year Ended December 31
	2011		2010		2009
	(In thousands)
Weighted average shares outstanding:
Basic weighted average shares outstanding		190,086		162,398		150,963
Effect of common stock equivalents under incentive plans		819		812		309
Diluted weighted average shares outstanding		190,905		163,210		151,272

        The effect of options to purchase 2.6 million, 2.5 million and 2.2 million shares of common stock were excluded from the calculation of diluted weighted average shares outstanding for the years ended December 31, 2011, 2010 and 2009, respectively, because the exercise price of these options exceeded the average market price of the Company's common stock for this period.

21.    Leases

        The Company leases equipment, land and various other properties under non-cancelable long-term leases, expiring at various dates. Certain leases contain options that would allow the Company to extend the lease or purchase the leased asset at the end of the base lease term. In addition, the Company enters into various non-cancelable royalty lease agreements under which future minimum payments are due.

        Minimum payments due in future years under these agreements in effect at December 31, 2011 are as follows:

	Operating Leases		Royalties
	(In thousands)
2012	$	28,903	$	24,378
2013		27,610		25,595
2014		25,119		25,810
2015		17,641		27,565
2016		9,648		24,397
Thereafter		12,640		114,371
	$	121,561	$	242,116

        Rental expense, including amounts related to these operating leases and other shorter-term arrangements, amounted to $43.9 million in 2011, $41.6 million in 2010 and $43.3 million in 2009.

        Royalties are paid to lessors either as a fixed price per ton or as a percentage of the gross sales price of the mined coal. Royalties under the majority of the Company's significant leases are paid on a percentage royalty basis. Royalty expense, including production royalties, was $349.0 million in 2011, $286.8 million in 2010 and $230.5 million in 2009.

        As of December 31, 2011, certain of the Company's lease obligations were secured by outstanding surety bonds totaling $64.6 million.

F-42

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

22.    Guarantees and Commitments

        The Company has agreed to continue to provide surety bonds and letters of credit for the reclamation and retiree healthcare obligations of Magnum Coal Company ("Magnum") related to the properties the Company sold to Magnum on December 31, 2005. Patriot Coal Corporation ("Patriot") acquired Magnum in July 2008. The purchase agreement requires Magnum to reimburse the Company for costs related to the surety bonds and letters of credit and to use commercially reasonable efforts to replace the obligations. If the surety bonds and letters of credit related to the reclamation obligations are not replaced by Magnum within a specified period of time, Magnum must post a letter of credit in favor of the Company in the amounts of the reclamation obligations. As of December 31, 2011, Patriot had replaced $48.9 million of the surety bonds and posted letters of credit of $16.1 million in the Company's favor. At December 31, 2011, the Company had $38.5 million of surety bonds remaining related to properties sold to Magnum. The surety bonding amounts are mandated by the state and are not directly related to the estimated cost to reclaim the properties.

        Magnum also acquired certain coal supply contracts with customers who did not consent to the assignment of the contract from the Company to Magnum. The Company has committed to purchase coal from Magnum to fulfill these contracts at the same price it is charging the customers for the sale. In addition, certain contracts were assigned to Magnum, but the Company has guaranteed Magnum's performance under the contracts. The longest of the coal supply contracts extends to the year 2017. If Magnum is unable to supply the coal for these coal sales contracts then the Company would be required to purchase coal on the open market or supply contracts from its existing operations. At market prices effective at December 31, 2011, the cost of purchasing 9.8 million tons of coal to supply over their duration the contracts that were not assigned would exceed the sales price under the contracts by approximately $199.4 million, and the cost of purchasing 0.7 million tons of coal to supply over their duration the assigned and guaranteed contracts would exceed the sales price under the contracts by approximately $15.3 million. As the Company does not believe that it is probable that it would have to purchase replacement coal, no losses have been recorded in the consolidated financial statements as of December 31, 2011. However, if the Company would have to perform under these guarantees, it could potentially have a material adverse effect on the business, results of operations and financial condition of the Company.

        In connection with the Company's acquisition of the coal operations of ARCO and the simultaneous combination of the acquired ARCO operations and the Company's Wyoming operations into the Arch Western joint venture, the Company agreed to indemnify the other member of Arch Western against certain tax liabilities in the event that such liabilities arise prior to June 1, 2013 as a result of certain actions taken, including the sale or other disposition of certain properties of Arch Western, the repurchase of certain equity interests in Arch Western by Arch Western or the reduction under certain circumstances of indebtedness incurred by Arch Western in connection with the acquisition. If the Company were to become liable, the maximum amount of potential future tax payments was $19.3 million at December 31, 2011, which is not recorded as a liability in the Company's consolidated financial statements. Since the indemnification is dependent upon the initiation of activities within the Company's control and the Company does not intend to initiate such activities, it is remote that the Company will become liable for any obligation related to this indemnification. However, if such indemnification obligation were to arise, it could potentially have a material adverse effect on the business, results of operations and financial condition of the Company.

        The Company has unconditional purchase obligations relating to purchases of coal, materials and supplies and capital commitments, other than reserve acquisitions, and is also a party to transportation capacity commitments. The future commitments under these agreements total $487.5 million in 2012, $139.2 million in 2013, $175.0 million in 2014, $163.9 million in 2015, $128.3 million in 2016 and $154.8 million thereafter. These commitments include the cost of coal purchases from Magnum as discussed above. During the years ended December 31, 2011, 2010 and 2009, the Company fulfilled its commitments under agreements containing unconditional obligations.

F-43

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

23.    Contingencies

        The following matters relate to certain claims and legal actions involving ICG and/or its subsidiaries.

        Allegheny Energy Supply ("Allegheny"), the sole customer of coal produced at our subsidiary Wolf Run Mining Company's ("Wolf Run") Sycamore No. 2 mine, filed a lawsuit against Wolf Run, Hunter Ridge Holdings, Inc. ("Hunter Ridge"), and ICG in state court in Allegheny County, Pennsylvania on December 28, 2006, and amended its complaint on April 23, 2007. Allegheny claimed that Wolf Run breached a coal supply contract when it declared force majeure under the contract upon idling the Sycamore No. 2 mine in the third quarter of 2006, and that Wolf Run continued to breach the contract by failing to ship in volumes referenced in the contract. The Sycamore No. 2 mine was idled after encountering adverse geologic conditions and abandoned gas wells that were previously unidentified and unmapped. After extensive searching for gas wells and rehabilitation of the mine, it was re-opened in 2007, but with notice to Allegheny that it would necessarily operate at reduced volumes in order to safely and effectively avoid the many gas wells within the reserve. The amended complaint also alleged that the production stoppages constitute a breach of the guarantee agreement by Hunter Ridge and breach of certain representations made upon entering into the contract in early 2005. Allegheny voluntarily dropped the breach of representation claims later. Allegheny claimed that it would incur costs in excess of $100 million to purchase replacement coal over the life of the contract. ICG, Wolf Run and Hunter Ridge answered the amended complaint on August 13, 2007, disputing all of the remaining claims.

        On November 3, 2008, ICG, Wolf Run and Hunter Ridge filed an amended answer and counterclaim against the plaintiffs seeking to void the coal supply agreement due to, among other things, fraudulent inducement and conspiracy. On September 23, 2009, Allegheny filed a second amended complaint alleging several alternative theories of liability in its effort to extend contractual liability to ICG, which was not a party to the original contract and did not exist at the time Wolf Run and Allegheny entered into the contract. No new substantive claims were asserted. ICG answered the second amended complaint on October 13, 2009, denying all of the new claims. The Company's counterclaim was dismissed on motion for summary judgment entered on May 11, 2010. Allegheny's claims against ICG were also dismissed by summary judgment, but the claims against Wolf Run and Hunter Ridge were not. The court conducted a non-jury trial of this matter beginning on January 10, 2011 and concluding on February 1, 2011. At the trial, Allegheny presented its evidence for breach of contract and claimed that it is entitled to past and future damages in the aggregate of between $228 million and $377 million. Wolf Run and Hunter Ridge presented their defense of the claims, including evidence with respect to the existence of force majeure conditions and excuse under the contract and applicable law. Wolf Run and Hunter Ridge presented evidence that Allegheny's damages calculations were significantly inflated because it did not seek to determine damages as of the time of the breach and in some instances artificially assumed future nondelivery or did not take into account the apparent requirement to supply coal in the future. On May 2, 2011, the trial court entered a Memorandum and Verdict determining that Wolf Run had breached the coal supply contract and that the performance shortfall was not excused by force majeure. ICG and Allegheny filed post-verdict motions in the trial court and on August 23, 2011, the court denied the parties' motions. The court entered a final judgment on August 25, 2011, in the amount of $104.1 million, which included pre-judgment interest. The parties appealed the lower court's decision to the Superior Court of Pennsylvania. Wolf Run and Hunter Ridge have filed an appeal bond in the amount of $124.9 million. Briefing is underway and will be completed in early 2012.

        As of December 31, 2011, the Company has accrued $108.3 million for this lawsuit, including $3.4 million of interest recognized post-acquisition. The ultimate resolution of this matter could result in an outcome which may be materially different than what the Company has accrued.

        In addition, the Company is a party to numerous claims and lawsuits with respect to various matters. The Company provides for costs related to contingencies when a loss is probable and the amount is reasonably determinable. After conferring with counsel, it is the opinion of management that the ultimate resolution of pending claims, other than as noted above, will not have a material adverse effect on the consolidated financial condition, results of operations or liquidity of the Company.

F-44

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

24.    Segment Information

        The Company has three reportable business segments, which are based on the major coal producing basins in which the Company operates. Each of these reportable business segments includes a number of mine complexes. The Company manages its coal sales by coal basin, not by individual mine complex. Geology, coal transportation routes to customers, regulatory environments and coal quality are characteristic to a basin. Accordingly, market and contract pricing have developed by coal basin. Mine operations are evaluated based on their per-ton operating costs (defined as including all mining costs but excluding pass-through transportation expenses), as well as on other non-financial measures, such as safety and environmental performance. The Company's reportable segments are the Powder River Basin (PRB) segment, with operations in Wyoming; the Western Bituminous (WBIT) segment, with operations in Utah, Colorado and southern Wyoming; the Appalachia (APP) segment, with operations in West Virginia, Kentucky, Maryland and Virginia. The Appalachia segment includes the acquired ICG operations in Appalachia, as well as the Company's previous Central Appalachia segment. The "Other" operating segment represents primarily the Company's Illinois operations and ADDCAR subsidiary, which manufactures and sells its patented highwall mining system.

        Operating segment results for the years ended December 31, 2011, 2010 and 2009 are presented below. Results for the reportable segments include all direct costs of mining, including all depreciation, depletion and amortization related to the mining operations, even if the assets are not recorded at the operating segment level. See discussion of segment assets below. Corporate, Other and Eliminations includes the change in fair value of coal derivatives and coal trading activities, net; corporate overhead; land management; other support functions; and the elimination of intercompany transactions.

        The asset amounts below represent an allocation of assets used in the segments' cash-generating activities. The amounts in Corporate, Other and Eliminations represent primarily corporate assets (cash, receivables, investments, plant, property and equipment) as well as unassigned coal reserves, above-market acquired sales contracts and other unassigned assets.

	PRB		APP			WBIT			Other Operating Segments			Corporate, Other and Eliminations			Consolidated
	(In thousands)
December 31, 2011
Revenues	$	1,646,947	$	1,915,090		$	672,766		$	51,092		$	—		$	4,285,895
Income (loss) from operations		180,730		283,404			119,665			(4,685	)		(165,538	)		413,576
Total assets		2,307,783		4,740,723			681,393			581,040			1,903,020			10,213,959
Depreciation, depletion and amortization		171,693		203,759			81,235			7,876			2,024			466,587
Amortization of acquired sales contracts, net		19,458		(39,988	)		—			(1,539	)		—			(22,069	)
Capital expenditures		110,999		217,435			66,356			28,243			117,903			540,936
December 31, 2010
Revenues	$	1,606,236	$	1,042,490		$	537,542		$	—		$	—		$	3,186,268
Income from operations		146,555		193,943			58,082			—			(74,596	)		323,984
Total assets		2,295,786		706,624			677,611			—			1,200,748			4,880,769
Depreciation, depletion and amortization		185,218		97,764			80,497			—			1,587			365,066
Amortization of acquired sales contracts, net		35,606		—			—			—			—			35,606
Capital expenditures		38,142		70,839			65,470			—			140,206			314,657
December 31, 2009
Revenues	$	1,205,492	$	829,895		$	540,694		$	—		$	—		$	2,576,081
Income from operations		82,341		105,241			29,722			—			(93,590	)		123,714
Total assets		2,421,917		734,309			687,873			—			996,497			4,840,596
Depreciation, depletion and amortization		127,378		88,409			83,781			—			2,040			301,608
Amortization of acquired sales contracts, net		19,934		—			(311	)		—			—			19,623
Capital expenditures		58,275		48,673			67,299			—			148,903			323,150

F-45

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

        A reconciliation of segment income from operations to consolidated income before income taxes follows:

	Year Ended December 31
	2011			2010			2009
	(In thousands)
Income from operations	$	413,576		$	323,984		$	123,714
Interest expense		(230,186	)		(142,549	)		(105,932	)
Interest income		3,309			2,449			7,622
Bridge financing costs related to ICG		(49,490	)		—			—
Loss on early extinguishment of debt		(1,958	)		(6,776	)		—
Income before income taxes	$	135,251		$	177,108		$	25,404

25.    Quarterly Financial Information (Unaudited)

        Quarterly financial data for the years ended December 31, 2011 and 2010 is summarized below:

	March 31			June 30		September 30		December 31
				(a)(b)		(a)(b)		(a)
	(In thousands, except per share data)
2011:
Revenues	$	872,938		$	985,528	$	1,198,673	$	1,228,756
Gross profit		129,773			171,440		118,974		153,280
Income from operations		102,238			95,354		76,256		139,728
Net income		55,874			6,630		9,121		71,215
Basic earnings per common share		0.34			0.04		0.04		0.34
Diluted earnings per common share		0.34			0.04		0.04		0.33
	March 31			June 30		September 30		December 31
				(c)		(d)
	(In thousands, except per share data)
2010:
Revenues	$	711,874		$	764,295	$	874,705	$	835,394
Gross profit		61,852			100,461		119,957		107,514
Income from operations		32,200			106,499		98,347		86,938
Net income (loss)		(1,770	)		66,274		46,859		48,031
Basic earnings (loss) per common share		(0.01	)		0.41		0.29		0.29
Diluted earnings (loss) per common share		(0.01	)		0.41		0.29		0.29

(a)

The Company expensed costs related to the acquisition of ICG $98.2 million, $4.7 million and $1.3 million in the second, third and fourth quarters of 2011, respectively.

(b)

The amounts above differ from those previously reported because of fair value adjustments related to the ICG acquisition made in the fourth quarter of 2011 and pushed back to the respective reporting periods. Net income in the second quarter of 2011 decreased $4.8 million, using an effective tax rate of 37%, from what was originally reported due to increases in cost of sales and depreciation, depletion and amortization expense and net income in the third quarter of 2011 decreased $10.2 million, using an effective tax rate of 37%, from what was originally reported due to an increase in depreciation, depletion and amortization expense.

(c)

In the second quarter of 2010, the Company exchanged 68.4 million tons of coal reserves in the Illinois Basin for an additional 9% ownership interest in Knight Hawk. The Company recognized a gain of $41.6 million on the transaction.

(d)

The Company's Dugout Canyon mine in Carbon County, Utah suspended operations on April 29, 2010 after an increase in carbon monoxide levels resulted from a heating event in a previously mined area. After permanently sealing the area, full coal production resumed on May 21, 2010. On June 22, 2010, an ignition event at the longwall resulted in a second evacuation of all underground employees at the mine. All employees were safely evacuated in both events. The resumption of mining required rendering the mine's atmosphere inert, ventilating the longwall area, determining the cause of the ignition, implementing preventive measures, and securing an MSHA-approved longwall ventilation plan. The longwall system resumed production at normalized levels by the end of September.

F-46

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

CONDENSED CONSOLIDATING STATEMENTS OF INCOME
Year Ended December 31, 2011

26.    Supplemental Condensed Consolidating Financial Information

        Pursuant to the indentures governing Arch Coal, Inc.'s senior notes, certain wholly-owned subsidiaries of the Company have fully and unconditionally guaranteed the senior notes on a joint and several basis. The following tables present condensed consolidating financial information for (i) the Company, (ii) the issuer of the senior notes, (iii) the guarantors under the senior notes, and (iv) the entities which are not guarantors under the senior notes (Arch Western Resources, LLC and its subsidiaries, Arch Receivable Company, LLC and the Company's subsidiaries outside the U.S.):

	Parent/Issuer			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
REVENUES	$	—		$	2,024,168		$	2,261,727		$	—		$	4,285,895
COSTS, EXPENSES AND OTHER
Cost of sales		22,925			1,537,697			1,812,461			(105,173	)		3,267,910
Depreciation, depletion and amortization		2,883			304,742			158,962			—			466,587
Amortization of acquired sales contracts, net		—			(41,527	)		19,458			—			(22,069	)
Selling, general and administrative expenses		74,591			13,860			37,839			(7,234	)		119,056
Change in fair value of coal derivatives and coal trading activities, net		—			(2,907	)		—			—			(2,907	)
Acquisition and transition costs		54,676			—			—			—			54,676
Other operating (income) expense, net		(23,306	)		(118,767	)		18,732			112,407			(10,934	)
		131,769			1,693,098			2,047,452			—			3,872,319
Income from investment in subsidiaries		556,448			—			—			(556,448	)		—
Income from operations		424,679			331,070			214,275			(556,448	)		413,576
Interest income (expense), net:
Interest expense		(256,220	)		(5,062	)		(43,728	)		74,824			(230,186	)
Interest income		16,282			759			61,092			(74,824	)		3,309
		(239,938	)		(4,303	)		17,364			—			(226,877	)
Other non-operating expense
Bridge financing costs related to ICG		(49,490	)		—			—			—			(49,490	)
Net loss resulting from early retirement of debt		—			(1,958	)		—			—			(1,958	)
		(49,490	)		(1,958	)		—			—			(51,448	)
Income before income taxes		135,251			324,809			231,639			(556,448	)		135,251
Benefit from income taxes		(7,589	)		—			—			—			(7,589	)
Net income		142,840			324,809			231,639			(556,448	)		142,840
Less: Net income attributable to noncontrolling interest		(1,157	)		—			—			—			(1,157	)
Net income attributable to Arch Coal	$	141,683		$	324,809		$	231,639		$	(556,448	)	$	141,683

F-47

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

CONDENSED CONSOLIDATING STATEMENTS OF INCOME
Year Ended December 31, 2010

	Parent/Issuer			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
REVENUES	$	—		$	1,137,980		$	2,048,288		$	—		$	3,186,268
COSTS, EXPENSES AND OTHER
Cost of sales		11,526			797,917			1,679,872			(93,503	)		2,395,812
Depreciation, depletion and amortization		2,933			194,847			167,286			—			365,066
Amortization of acquired sales contracts, net		—			—			35,606			—			35,606
Selling, general and administrative expenses		79,580			7,355			38,496			(7,254	)		118,177
Change in fair value of coal derivatives and coal trading activities, net		—			8,924			—			—			8,924
Gain on Knight Hawk transaction		—			(41,577	)		—			—			(41,577	)
Other operating (income) expense, net		(10,259	)		(115,994	)		5,772			100,757			(19,724	)
		83,780			851,472			1,927,032			—			2,862,284
Income from investment in subsidiaries		393,366			—			—			(393,366	)		—
Income from operations		309,586			286,508			121,256			(393,366	)		323,984
Interest expense, net:
Interest expense		(143,606	)		(2,763	)		(64,463	)		68,283			(142,549	)
Interest income		11,128			456			59,148			(68,283	)		2,449
		(132,478	)		(2,307	)		(5,315	)		—			(140,100	)
Other non-operating expense
Net loss resulting from early retirement of debt		—			—			(6,776	)		—			(6,776	)
		—			—			(6,776	)		—			(6,776	)
Income before income taxes		177,108			284,201			109,165			(393,366	)		177,108
Provision for income taxes		17,714			—			—			—			17,714
Net income		159,394			284,201			109,165			(393,366	)		159,394
Less: Net income attributable to noncontrolling interest		(537	)		—			—			—			(537	)
Net income attributable to Arch Coal	$	158,857		$	284,201		$	109,165		$	(393,366	)	$	158,857

F-48

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

CONDENSED CONSOLIDATING STATEMENTS OF INCOME
Year Ended December 31, 2009

	Parent/Issuer			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
REVENUES	$	—		$	924,692		$	1,651,389		$	—		$	2,576,081
COSTS, EXPENSES AND OTHER
Cost of sales		7,481			713,782			1,398,663			(49,211	)		2,070,715
Depreciation, depletion and amortization		3,678			138,125			159,805			—			301,608
Amortization of acquired sales contracts, net		—			—			19,623			—			19,623
Selling, general and administrative expenses		49,672			7,504			46,563			(5,952	)		97,787
Change in fair value of coal derivatives and coal trading activities, net		—			(12,056	)		—			—			(12,056	)
Acquisition and transition costs		13,726			—			—			—			13,726
Other operating (income) expense, net		(12,909	)		(85,460	)		4,170			55,163			(39,036	)
		61,648			761,895			1,628,824			—			2,452,367
Income from investment in subsidiaries		165,183			—			—			(165,183	)		—
Income from operations		103,535			162,797			22,565			(165,183	)		123,714
Interest expense, net:
Interest expense		(92,371	)		(2,442	)		(70,668	)		59,549			(105,932	)
Interest income		14,240			720			52,211			(59,549	)		7,622
		(78,131	)		(1,722	)		(18,457	)		—			(98,310	)
Income before income taxes		25,404			161,075			4,108			(165,183	)		25,404
Benefit from income taxes		(16,775	)		—			—			—			(16,775	)
Net income		42,179			161,075			4,108			(165,183	)		42,179
Less: Net income attributable to noncontrolling interest		(10	)		—			—			—			(10	)
Net income attributable to Arch Coal	$	42,169		$	161,075		$	4,108		$	(165,183	)	$	42,169

F-49

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

CONDENSED CONSOLIDATING BALANCE SHEETS
December 31, 2011

	Parent/Issuer			Guarantor Subsidiaries		Non-Guarantor Subsidiaries		Eliminations			Consolidated
	(In thousands)
ASSETS
Cash and cash equivalents	$	61,375		$	332	$	76,442	$	—		$	138,149
Restricted cash		10,322			—		—		—			10,322
Receivables		65,187			22,037		383,572		(1,617	)		469,179
Inventories		—			207,050		170,440		—			377,490
Other		81,732			83,122		22,780		—			187,634
Total current assets		218,616			312,541		653,234		(1,617	)		1,182,774
Property, plant and equipment, net		21,241			6,403,658		1,524,251		—			7,949,150
Investment in subsidiaries		8,805,731			—		—		(8,805,731	)		—
Intercompany receivables		(1,457,864	)		7,010		1,450,854		—			—
Note receivable from Arch Western		225,000			—		—		(225,000	)		—
Other		184,266			884,613		13,156		—			1,082,035
Total other assets		7,757,133			891,623		1,464,010		(9,030,731	)		1,082,035
Total assets	$	7,996,990		$	7,607,822	$	3,641,495		(9,032,348	)	$	10,213,959
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable	$	25,409		$	175,196	$	183,177	$	—		$	383,782
Accrued expenses and other current liabilities		75,133			115,685		166,834		(1,617	)		356,035
Current maturities of debt and short-term borrowings		172,564			1,987		106,300		—			280,851
Total current liabilities		273,106			292,868		456,311		(1,617	)		1,020,668
Long-term debt		3,308,674			2,652		450,971					3,762,297
Note payable to Arch Coal		—			—		225,000		(225,000	)		—
Asset retirement obligations		877			140,861		305,046		—			446,784
Accrued pension benefits		19,198			4,203		24,843		—			48,244
Accrued postretirement benefits other than pension		13,843			6,271		22,195		—			42,309
Accrued workers' compensation		17,272			48,111		6,565		—			71,948
Deferred income taxes		621,483			355,270		—		—			976,753
Other noncurrent liabilities		152,963			64,795		37,624		—			255,382
Total liabilities		4,407,416			915,031		1,528,555		(226,617	)		6,624,385
Redeemable noncontrolling interest		11,534			—		—		—			11,534
Stockholders' equity		3,578,040			6,692,791		2,112,940		(8,805,731	)		3,578,040
Total liabilities and stockholders' equity	$	7,996,990		$	7,607,822	$	3,641,495	$	(9,032,348	)	$	10,213,959

F-50

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

CONDENSED CONSOLIDATING BALANCE SHEETS
December 31, 2010

	Parent/Issuer			Guarantor Subsidiaries		Non-Guarantor Subsidiaries		Eliminations			Consolidated
	(In thousands)
ASSETS
Cash and cash equivalents	$	13,713		$	64	$	79,816	$	—		$	93,593
Receivables		31,458			12,740		210,075		(1,953	)		252,320
Inventories		—			85,196		150,420		—			235,616
Other		29,575			102,375		21,435		—			153,385
Total current assets		74,746			200,375		461,746		(1,953	)		734,914
Property, plant and equipment, net		9,817			1,800,578		1,498,497		—			3,308,892
Investment in subsidiaries		4,555,233			—		—		(4,555,233	)		—
Intercompany receivables		(1,807,902	)		508,624		1,299,278		—			—
Note receivable from Arch Western		225,000			—		—		(225,000	)		—
Other		481,345			344,698		10,920		—			836,963
Total other assets		3,453,676			853,322		1,310,198		(4,780,233	)		836,963
Total assets	$	3,538,239		$	2,854,275	$	3,270,441	$	(4,782,186	)	$	4,880,769
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable	$	10,753		$	65,793	$	121,670	$	—		$	198,216
Accrued expenses and other current liabilities		75,746			31,123		153,217		(1,953	)		258,133
Current maturities of debt and short-term borrowings		14,093			—		56,904		—			70,997
Total current liabilities		100,592			96,916		331,791		(1,953	)		527,346
Long-term debt		1,087,126			—		451,618		—			1,538,744
Note payable to Arch Coal		—			—		225,000		(225,000	)		—
Asset retirement obligations		873			32,029		301,355		—			334,257
Accrued pension benefits		20,843			4,407		23,904		—			49,154
Accrued postretirement benefits other than pension		14,284			—		23,509		—			37,793
Accrued workers' compensation		15,383			13,805		6,102		—			35,290
Other noncurrent liabilities		51,187			22,135		36,912		—			110,234
Total liabilities		1,290,288			169,292		1,400,191		(226,953	)		2,632,818
Redeemable noncontrolling interest		10,444			—		—		—			10,444
Stockholders' equity		2,237,507			2,684,983		1,870,250		(4,555,233	)		2,237,507
Total liabilities and stockholders' equity	$	3,538,239		$	2,854,275	$	3,270,441	$	(4,782,186	)	$	4,880,769

F-51

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS
Year Ended December 31, 2011

	Parent/Issuer			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
				(In thousands)
Cash provided by (used in) operating activities	$	(561,704	)	$	801,201		$	402,745		$	—		$	642,242
Investing Activities
Acquisitions of businesses, net of cash acquired		(2,894,339	)		—			—			—			(2,894,339	)
Decrease in restricted cash		5,167			—			—			—			5,167
Capital expenditures		(12,809	)		(353,441	)		(174,686	)		—			(540,936	)
Proceeds from dispositions of property, plant and equipment		—			25,730			157			—			25,887
Additions to prepaid royalties		—			(25,982	)		(3,975	)		—			(29,957	)
Purchases of investments and advances to affiliates		(633,534	)		(33,553	)		—			605,178			(61,909	)
Consideration paid related to prior business acquisitions		(829	)		—			—			—			(829	)
Cash used in investing activities		(3,536,344	)		(387,246	)		(178,504	)		605,178			(3,496,916	)
Financing Activities
Proceeds from the issuance of senior notes		2,000,000			—			—			—			2,000,000
Proceeds from the issuance of common stock, net		1,267,933			—			—			—			1,267,933
Contributions from parent		—			605,178			—			(605,178	)		—
Payments to retire debt		—			(605,178	)		—			—			(605,178	)
Net increase (decrease) in borrowings under lines of credit and commercial paper program		481,300			—			(56,904	)		—			424,396
Net proceeds from other debt		5,334			—			—			—			5,334
Debt financing costs		(114,799	)		—			(24	)		—			(114,823	)
Dividends paid		(80,748	)		—			—			—			(80,748	)
Issuance of common stock under incentive plans		2,316			—			—			—			2,316
Transactions with affiliates, net		584,374			(413,687	)		(170,687	)		—			—
Cash provided by (used in) financing activities		4,145,710			(413,687	)		(227,615	)		(605,178	)		2,899,230
Increase (decrease) in cash and cash equivalents		47,662			268			(3,374	)		—			44,556
Cash and cash equivalents, beginning of period		13,713			64			79,816			—			93,593
Cash and cash equivalents, end of period	$	61,375		$	332		$	76,442		$	—		$	138,149

F-52

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS
Year Ended December 31, 2010

	Parent/Issuer			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Consolidated
	(In thousands)
Cash provided by (used in) operating activities	$	(238,736	)	$	503,766		$	432,117		$	697,147
Investing Activities
Capital expenditures		(4,814	)		(198,243	)		(111,600	)		(314,657	)
Proceeds from dispositions of property, plant and equipment		—			251			79			330
Additions to prepaid royalties		—			(24,381	)		(2,974	)		(27,355	)
Purchases of investments and advances to affiliates		(40,421	)		(5,764	)		—			(46,185	)
Consideration paid related to prior business acquisitions		(1,262	)		—			—			(1,262	)
Cash used in investing activities		(46,497	)		(228,137	)		(114,495	)		(389,129	)
Financing Activities
Proceeds from the issuance of senior notes		500,000			—			—			500,000
Payments to retire debt		—			—			(505,627	)		(505,627	)
Net decrease in borrowings under lines of credit and commercial paper program		(120,000	)		—			(76,549	)		(196,549	)
Net proceeds from other debt		82			—			—			82
Debt financing costs		(12,022	)		—			(729	)		(12,751	)
Dividends paid		(63,373	)		—			—			(63,373	)
Issuance of common stock under incentive plans		1,764									1,764
Contribution from noncontrolling interest		—			—			891			891
Transactions with affiliates, net		(61,760	)		(275,629	)		337,389			—
Cash provided by (used in) financing activities		244,691			(275,629	)		(244,625	)		(275,563	)
Increase (decrease) in cash and cash equivalents		(40,542	)		—			72,997			32,455
Cash and cash equivalents, beginning of period		54,255			64			6,819			61,138
Cash and cash equivalents, end of period	$	13,713		$	64		$	79,816		$	93,593

F-53

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS
Year Ended December 31, 2009

	Parent/Issuer			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Consolidated
	(In thousands)
Cash provided by (used in) operating activities	$	(168,427	)	$	338,956		$	212,451		$	382,980
Investing Activities
Acquisitions of businesses, net of cash acquired		(768,819	)		—			—			(768,819	)
Capital expenditures		(2,940	)		(194,756	)		(125,454	)		(323,150	)
Proceeds from dispositions of property, plant and equipment		—			734			91			825
Additions to prepaid royalties		—			(23,991	)		(2,764	)		(26,755	)
Purchases of investments and advances to affiliates		(8,000	)		(2,925	)		—			(10,925	)
Consideration paid related to prior business acquisitions		(4,767	)		—			—			(4,767	)
Reimbursement of deposits on equipment		—			—			3,209			3,209
Cash used in investing activities		(784,526	)		(220,938	)		(124,918	)		(1,130,382	)
Financing Activities
Proceeds from the issuance of senior notes		584,784			—			—			584,784
Proceeds from the sale of common stock, net		326,452			—			—			326,452
Net decrease in borrowings under lines of credit and commercial paper program		(85,000	)		—			(815	)		(85,815	)
Net payments on other debt		(2,986	)		—			—			(2,986	)
Debt financing costs		(29,456	)		—			(203	)		(29,659	)
Dividends paid		(54,969	)		—			—			(54,969	)
Issuance of common stock under incentive plans		84			—			—			84
Transactions with affiliates, net		200,562			(118,015	)		(82,547	)		—
Cash provided by (used in) financing activities		939,471			(118,015	)		(83,565	)		737,891
Increase (decrease) in cash and cash equivalents		(13,482	)		3			3,968			(9,511	)
Cash and cash equivalents, beginning of period		67,737			61			2,851			70,649
Cash and cash equivalents, end of period	$	54,255		$	64		$	6,819		$	61,138

F-54

Schedule II

Arch Coal, Inc. and Subsidiaries

Valuation and Qualifying Accounts

	Balance at Beginning of Year		Additions (Reductions) Charged to Costs and Expenses			Charged to Other Accounts		Deductions(a)		Balance at End of Year
	(In thousands)
Year ended December 31, 2011
Reserves deducted from asset accounts:
Other assets — other notes and accounts receivable	$	—	$	17		$	—	$	—	$	17
Current assets — supplies and inventory		12,701		1,755			—		1,349		13,107
Deferred income taxes		737		2,416			—		322		2,831
Year ended December 31, 2010
Reserves deducted from asset accounts:
Other assets — other notes and accounts receivable	$	109	$	—		$	—	$	109	$	—
Current assets — supplies and inventory		13,406		1,962			—		2,667		12,701
Deferred income taxes		1,120		(383	)		—		—		737
Year ended December 31, 2009
Reserves deducted from asset accounts:
Other assets — other notes and accounts receivable	$	225	$	(17	)	$	—	$	99	$	109
Current assets — supplies and inventory		12,760		1,302			—		656		13,406
Deferred income taxes		395		725			—		—		1,120

(a)

Reserves utilized, unless otherwise indicated.

F-55

EX-23.1

Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

We consent to the incorporation by reference in the following Registration Statements:

(1)Registration Statement (Form S-3 Nos. 333-157880 and 333-179841) of Arch Coal, Inc. and in the related Prospectus,

(2)Registration Statement (Form S-4 No. 333-179842) of Arch Coal, Inc. and in the related Prospectus

(3)Registration Statements (Form S-8 Nos. 333-30565 and 333-112536) pertaining to the Arch Coal, Inc. 1997 Stock Incentive Plan and in the related Prospectus,

(4)Registration Statement (Form S-8 Nos. 333-32777 and 333-156593) pertaining to the Arch Coal, Inc. and Subsidiaries Employee Thrift Plan and in the related Prospectus,

(5)Registration Statements (Form S-8 Nos. 333-68131 and 333-147459) pertaining to the Arch Coal, Inc. Deferred Compensation Plan and in the related Prospectus, and

(6)Registration Statements (Form S-8 Nos. 333-112537 and 333-127548) pertaining to the Arch Coal, Inc. Retirement Account Plan,

of our reports dated February 29, 2012, with respect to the consolidated financial statements and schedule of Arch Coal, Inc. and the effectiveness of internal control over financial reporting of Arch Coal, Inc. included in this Annual Report (Form 10-K/A) for the year ended December 31, 2011.

St. Louis, Missouri

April 23, 2012

EX-31.1

Exhibit 31.1

Certification

I, Steven F. Leer, certify that:

1. I have reviewed this Amendment No. 1 to Annual Report on Form 10-K/A of Arch Coal, Inc.;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

(a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

(c) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

(d) Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

(a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

(b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

	/s/ Steven F. Leer
	Steven F. Leer
	Chairman and Chief Executive Officer
Date: April 23, 2012

EX-31.2

Exhibit 31.2

Certification

I, John T. Drexler, certify that:

1. I have reviewed this Amendment No. 1 to Annual Report on Form 10-K/A of Arch Coal, Inc.;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

(a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

(c) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

(d) Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

(a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

(b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

	/s/ John T. Drexler
	John T. Drexler
	Senior Vice President and Chief Financial Officer
Date: April 23, 2012

EX-32.1

Exhibit 32.1

CERTIFICATION OF CHIEF EXECUTIVE OFFICER

OF ARCH COAL, INC. PURSUANT TO 18. U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO SECTION 906 OF THE

SARBANES-OXLEY ACT OF 2002

I, Steven F. Leer, Chairman and Chief Executive Officer of Arch Coal, Inc., certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that:

(1) Amendment No. 1 to the Annual Report on Form 10-K/A for the year ended December 31, 2011 (the “Periodic Report”) which this statement accompanies fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934 (15 U.S.C. 78m or 78o(d)); and

(2) information contained in the Periodic Report fairly presents, in all material respects, the financial condition and results of operations of Arch Coal, Inc.

/s/ Steven F. Leer

Steven F. Leer

Chairman and Chief Executive Officer

Date: April 23, 2012

EX-32.2

Exhibit 32.2

CERTIFICATION OF CHIEF FINANCIAL OFFICER

OF ARCH COAL, INC. PURSUANT TO 18. U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO SECTION 906 OF THE

SARBANES-OXLEY ACT OF 2002

I, John T. Drexler, Senior Vice President and Chief Financial Officer of Arch Coal, Inc., certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that:

(1) Amendment No. 1 to the Annual Report on Form 10-K/A for the year ended December 31, 2011 (the “Periodic Report”) which this statement accompanies fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934 (15 U.S.C. 78m or 78o(d)); and

(2) information contained in the Periodic Report fairly presents, in all material respects, the financial condition and results of operations of Arch Coal, Inc.

/s/ John T. Drexler

John T. Drexler

Senior Vice President and Chief Financial Officer

Date: April 23, 2012

XML

Acquired Sales Contracts (Tables)

12 Months Ended

Dec. 31, 2011

Acquired Sales Contracts [Abstract]

Schedule Of Acquired Sales Contracts

		December 31, 2011				December 31, 2010
		Assets		Liabilities		Assets		Liabilities
		(In thousands)				(In thousands)
Acquired fair value	$	149,457	$	166,697	$	114,453	$	40,654
Accumulated amortization		(115,322)		(69,699)		(82,376)		(14,613)
Total	$	34,135	$	96,998	$	32,077	$	26,041
Net total			$	(62,863)	$	6,036
Balance Sheet classification:
Other current	$	18,929	$	38,441	$	25,063	$	5,615
Other noncurrent	$	15,206	$	58,557	$	7,014	$	20,426

XML

Segment Information (Schedule Of Operating Segment Results) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Segment Reporting Information [Line Items]
Revenues									$ 4,285,895	$ 3,186,268	$ 2,576,081
Income (loss) from operations	139,728	76,256	95,354	102,238	86,938	98,347	106,499	32,200	413,576	323,984	123,714
Total assets	10,213,959				4,880,769				10,213,959	4,880,769	4,840,596
Depreciation, depletion and amortization									466,587	365,066	301,608
Amortization of acquired sales contacts, net									(22,069)	35,606	19,623
Capital expenditures									540,936	314,657	323,150
Number of reportable business segments									three
PRB [Member]
Segment Reporting Information [Line Items]
Revenues									1,646,947	1,606,236	1,205,492
Income (loss) from operations									180,730	146,555	82,341
Total assets	2,307,783				2,295,786				2,307,783	2,295,786	2,421,917
Depreciation, depletion and amortization									171,693	185,218	127,378
Amortization of acquired sales contacts, net									19,458	35,606	19,934
Capital expenditures									110,999	38,142	58,275
APP [Member]
Segment Reporting Information [Line Items]
Revenues									1,915,090	1,042,490	829,895
Income (loss) from operations									283,404	193,943	105,241
Total assets	4,740,723				706,624				4,740,723	706,624	734,309
Depreciation, depletion and amortization									203,759	97,764	88,409
Amortization of acquired sales contacts, net									(39,988)
Capital expenditures									217,435	70,839	48,673
WBIT [Member]
Segment Reporting Information [Line Items]
Revenues									672,766	537,542	540,694
Income (loss) from operations									119,665	58,082	29,722
Total assets	681,393				677,611				681,393	677,611	687,873
Depreciation, depletion and amortization									81,235	80,497	83,781
Amortization of acquired sales contacts, net											(311)
Capital expenditures									66,356	65,470	67,299
Other [Member]
Segment Reporting Information [Line Items]
Revenues									51,092
Income (loss) from operations									(4,685)
Total assets	581,040								581,040
Depreciation, depletion and amortization									7,876
Amortization of acquired sales contacts, net									(1,539)
Capital expenditures									28,243
Corporate, Other And Eliminations [Member]
Segment Reporting Information [Line Items]
Income (loss) from operations									(165,538)	(74,596)	(93,590)
Total assets	1,903,020				1,200,748				1,903,020	1,200,748	996,497
Depreciation, depletion and amortization									2,024	1,587	2,040
Capital expenditures									$ 117,903	$ 140,206	$ 148,903

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Segment Information (Tables)

12 Months Ended

Dec. 31, 2011

Segment Information [Abstract]

Schedule Of Operating Segment Results

	PRB	APP	WBIT		Other Operating Segments		Corporate, Other and Eliminations		Consolidated
	(In thousands)
December 31, 2011
Revenues	$  1,646,947	$  1,915,090		$  672,766		$   51,092		$                —		$  4,285,895
Income (loss) from operations	180,730	283,404		119,665		(4,685)		(165,538)		413,576
Total assets	2,307,783	4,740,723		681,393		581,040		1,903,020		10,213,959
Depreciation, depletion and amortization	171,693	203,759		81,235		7,876		2,024		466,587
Amortization of acquired sales contracts, net	19,458	(39,988)		—		(1,539)		—		(22,069)
Capital expenditures	110,999	217,435		66,356		28,243		117,903		540,936
December 31, 2010
Revenues	$  1,606,236	$  1,042,490		$  537,542		$                —		$               —		$  3,186,268
Income from operations	146,555	193,943		58,082		—		(74,596)		323,984
Total assets	2,295,786	706,624		677,611		—		1,200,748		4,880,769
Depreciation, depletion and amortization	185,218	97,764		80,497		—		1,587		365,066
Amortization of acquired sales contracts, net	35,606	—		—		—		—		35,606
Capital expenditures	38,142	70,839		65,470		—		140,206		314,657
December 31, 2009
Revenues	$  1,205,492	$      829,895		$  540,694		$                —		$                —		$  2,576,081
Income from operations	82,341	105,241		29,722		—		(93,590)		123,714
Total assets	2,421,917	734,309		687,873		—		996,497		4,840,596
Depreciation, depletion and amortization	127,378	88,409		83,781		—		2,040		301,608
Amortization of acquired sales contracts, net	19,934	—		(311)		—		—		19,623
Capital expenditures	58,275	48,673		67,299		—		148,903		323,150

Reconciliation Statement Of Segment Income From Operations To Consolidated Income Before Income Taxes

	Year Ended December 31
	2011	2010	2009
	(In thousands)
Income from operations	$    413,576	$    323,984	$  123,714
Interest expense	(230,186)	(142,549)	(105,932)
Interest income	3,309	2,449	7,622
Bridge financing costs related to ICG	(49,490)	—	—
Loss on early extinguishment of debt	(1,958)	(6,776)	—
Income before income taxes	$      135,251	$      177,108	$     25,404

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Accrued Workers' Compensation (Tables)

12 Months Ended

Dec. 31, 2011

Accrued Workers Compensation [Line Items]

Workers' Compensation Expense

	Year Ended December 31
	2011	2010	2009
	(In thousands)
Self-insured occupational disease benefits:
Service cost	$    2,059	$       727	$        531
Interest cost	1,799	675	558
Net amortization	(493)	(1,860)	(2,879)
Total occupational disease	3,365	(458)	(1,790)
Traumatic injury claims and assessments	16,979	9,263	8,904
Total workers' compensation expense	$  20,344	$    8,805	$     7,114

Workers' Compensation [Member]

Accrued Workers Compensation [Line Items]

Schedule Of Changes in Projected Benefit Obligations

	December 31
	2011	2010
	(In thousands)
Beginning of year obligation	$  17,412	$  9,702
Service cost	2,059	727
Interest cost	1,799	675
Actuarial loss	7,081	6,993
Benefit and administrative payments	(1,097)	(685)
Acquisition of ICG	26,930	—
Net obligation at end of year	$  54,184	$ 17,412

Schedule of Occupational Disease Obligation

	Year Ended December 31
	2011	2010	2009
Weighted average assumptions:
Discount rate	5.10%	5.96%	6.11%
Cost escalation rate	3.00%	3.00%	3.00%

Schedule Of Amounts Recognized In Balance Sheet

	December 31
	2011	2010
	(In thousands)
Occupational disease costs	$  54,184	$  17,412
Traumatic and other workers' compensation claims	29,430	24,537
Total obligations	83,614	41,949
Less amount included in accrued expenses	11,666	6,659
Noncurrent obligations	$  71,948	$  35,290

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Accumulated Other Comprehensive Income (Loss) (Components Of Accumulated Other Comprehensive Income (Loss)) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Accumulated Other Comprehensive Income (Loss) [Abstract]
Derivative Instruments, beginning balance	$ (4,729)	$ 2,921	$ 1,186	$ (45,249)
Derivative Instruments, before tax	(11,951)	2,711	72,553
Derivative Instruments, tax effect	4,301	(976)	(26,118)
Derivative Instruments, ending balance	(4,729)	2,921	1,186	(45,249)
Pension, Postretirement and Other Post-Employment Benefits, beginning balance	(4,676)	(10,679)	(20,539)	(33,433)
Pension, Postretirement and Other Post-Employment Benefits, before tax	9,345	15,406	20,124
Pension, Postretirement and Other Post-Employment Benefits, tax effect	(3,342)	(5,546)	(7,230)
Pension, Postretirement and Other Post-Employment Benefits, ending balance	(4,676)	(10,679)	(20,539)	(33,433)
Available-for-Sale Securities, beginning balance	1,455	1,341	(500)	(414)
Available-for-Sale Securities, before tax	176	2,877	(136)
Available-for-Sale Securities, tax effect	(62)	(1,036)	50
Available-for-Sale Securities, ending balance	1,455	1,341	(500)	(414)
Accumulated Other Comprehensive Loss, beginning balance	(7,950)	(6,417)	(19,853)	(79,096)
Accumulated Other Comprehensive Loss, before tax	(2,430)	20,994	92,541
Accumulated Other Comprehensive Loss, tax effect	897	(7,558)	(33,298)
Accumulated Other Comprehensive Loss, ending balance	$ (7,950)	$ (6,417)	$ (19,853)	$ (79,096)

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Quarterly Financial Information (Tables)

12 Months Ended

Dec. 31, 2011

Quarterly Financial Information [Abstract]

Quarterly Financial Information

	March 31	June 30	September 30	December 31
		(a)(b)	(a)(b)	(a)
	(In thousands, except per share data)
2011:
Revenues	$  872,938	$  985,528	$ 1,198,673	$  1,228,756
Gross profit	129,773	171,440	118,974	153,280
Income from operations	102,238	95,354	76,256	139,728
Net income	55,874	6,630	9,121	71,215
Basic earnings per common share	0.34	0.04	0.04	0.34
Diluted earnings per common share	0.34	0.04	0.04	0.33

	March 31	June 30	September 30	December 31
		(c)	(d)
	(In thousands, except per share data)
2010:
Revenues	$  711,874	$  764,295	$  874,705	$  835,394
Gross profit	61,852	100,461	119,957	107,514
Income from operations	32,200	106,499	98,347	86,938
Net income (loss)	(1,770)	66,274	46,859	48,031
Basic earnings (loss) per common share	(0.01)	0.41	0.29	0.29
Diluted earnings (loss) per common share	(0.01)	0.41	0.29	0.29

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Derivative Instruments (Net Derivatives As Reflected On The Balance Sheets) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Derivative [Line Items]
Derivative assets	$ 42,263	$ 51,068
Net derivatives as reflected on the balance sheet	16,301	23,719
Coal [Member]
Derivative [Line Items]
Coal derivative assets	13,335	15,191
Coal derivative liabilities	(7,828)	(4,947)
Other Current Assets [Member] | Heating Oil [Member]
Derivative [Line Items]
Derivative assets	$ 10,794	$ 13,475

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Stock Based Compensation And Other Incentive Plans (Changes In Stock Options Outstanding And Not Yet Vested And Related Grant-Date Fair Value Under The Incentive Plan) (Details) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Stock Based Compensation And Other Incentive Plans [Abstract]
Unvested options at January 1	1,901
Granted, Common Shares	728
Vested, Common Shares	(746)
Cancelled, Common Shares	(87)
Unvested options at December 31	1,796
Unvested options at January 1, Weighted Average Grant-Date Fair Value	10.61
Granted , Weighted Average Grant-Date Fair Value	14.18
Vested, Weighted Average Grant-Date Fair Value	13.28
Canceled, Weighted Average Grant-Date Fair Value	10.35
Unvested options at December 31, Weighted Average Grant-Date Fair Value	10.96

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Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2011

Fair Value Measurements [Abstract]

Summary Of Financial Assets And Liabilities Accounted For At Fair Value

	Fair Value at December 31, 2011
	Total		Level 1		Level 2		Level 3
	(In thousands)
Assets:
Investments in equity securities	$	7,540	$	7,540	$	—	$	—
Derivatives	24,129		12,361		1,450		10,318
Total assets	$	31,669	$	19,901	$	1,450	$	10,318
Liabilities:
Derivatives	$	7,828	$	—	$	3,721	$	4,107

Summary Of Change In The Fair Values Of Financial Instruments Categorized As Level 3

		Year Ended December 31, 2011
	(In thousands)
Balance, beginning of period		$	9,183
Realized and unrealized losses recognized in earnings, net		(16,727		)
Realized and unrealized losses recognized in other comprehensive income, net		(4,122		)
Purchases		23,867
Issuances		(2,160		)
Settlements		(3,830		)
Balance, end of period		$	6,211

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Supplemental Condensed Consolidating Financial Information

12 Months Ended

Dec. 31, 2011

Supplemental Condensed Consolidating Financial Information [Abstract]

Supplemental Condensed Consolidating Financial Information

26.  Supplemental Condensed Consolidating Financial Information

Pursuant to the indentures governing Arch Coal, Inc.'s senior notes, certain wholly-owned subsidiaries of the Company have fully and unconditionally guaranteed the senior notes on a joint and several basis. The following tables present condensed consolidating financial information for (i) the Company, (ii) the issuer of the senior notes, (iii) the guarantors under the senior notes, and (iv) the entities which are not guarantors under the senior notes (Arch Western Resources, LLC and its subsidiaries, Arch Receivable Company, LLC and the Company's subsidiaries outside the U.S.):

CONDENSED CONSOLIDATING STATEMENTS OF INCOME

Year Ended December 31, 2011

Parent/Issuer	Guarantor   Subsidiaries	Non-Guarantor Subsidiaries	Eliminations	Consolidated
(In thousands)

Revenues	$                  –	$2,024,168	$  2,261,727	$             –	$   4,285,895
Costs, expenses and other
Cost of sales	22,925	1,537,697	1,812,461	(105,173)	3,267,910
Depreciation, depletion and amortization	2,883	304,742	158,962	–	466,587
Amortization of acquired sales contracts, net	–	(41,527)	19,458	–	(22,069)
Selling, general and administrative expenses	74,591	13,860	37,839	(7,234)	119,056
Change in fair value of coal derivatives and coal trading activities, net	–	(2,907)	–	–	(2,907)
Acquisition and transition costs	54,676	–	–	–	54,676
Other operating (income) expense, net	(23,306)	(118,767)	18,732	112,407	(10,934)
	131,769	1,693,098	2,047,452	-	3,872,319
Income from investment in subsidiaries	556,448	–	–	(556,448)	–
Income from operations	424,679	331,070	214,275	(556,448)	413,576
Interest income (expense), net:
Interest expense	(256,220)	(5,062)	(43,728)	74,824	(230,186)
Interest income	16,282	759	61,092	(74,824)	3,309
	(239,938)	(4,303)	17,364	–	(226,877)
Other non-operating expense
Bridge financing costs related to ICG	(49,490)	-	-	-	(49,490)
Net loss resulting from early retirement of debt	–	(1,958)	-	–	(1,958)
	(49,490)	(1,958)	-	–	(51,448)
Income before income taxes	135,251	324,809	231,639	(556,448)	135,251
Benefit from income taxes	(7,589)	–	–	–	(7,589)
Net income	142,840	324,809	231,639	(556,448)	142,840
Less:  Net income attributable to noncontrolling interest	(1,157)	–	–	–	(1,157)
Net income attributable to Arch Coal	$  141,683	$  324,809	$   231,639	$(556,448)	$141,683

CONDENSED CONSOLIDATING STATEMENTS OF INCOME

Year Ended December 31, 2010

	Parent/Issuer	Guarantor   Subsidiaries	Non-Guarantor  Subsidiaries	Eliminations	Consolidated
	(In thousands)
Revenues	$               —	$  1,137,980	$     2,048,288	$               —	$  3,186,268
Costs, expenses and other
Cost of sales	11,526	797,917	1,679,872	(93,503)	2,395,812
Depreciation, depletion and amortization	2,933	194,847	167,286	—	365,066
Amortization of acquired sales contracts, net	—	—	35,606	—	35,606
Selling, general and administrative expenses	79,580	7,355	38,496	(7,254)	118,177
Change in fair value of coal derivatives and coal trading activities, net	—	8,924	—	—	8,924
Gain on Knight Hawk transaction	—	(41,577)	—	—	(41,577)
Other operating (income) expense, net	(10,259)	(115,994)	5,772	100,757	(19,724)
	83,780	851,472	1,927,032	—	2,862,284
Income from investment in subsidiaries	393,366	—	—	(393,366)	—
Income from operations	309,586	286,508	121,256	(393,366)	323,984
Interest expense, net:
Interest expense	(143,606)	(2,763)	(64,463)	68,283	(142,549)
Interest income	11,128	456	59,148	(68,283)	2,449
	(132,478)	(2,307)	(5,315)	—	(140,100)
Other non-operating expense
Net loss resulting from early retirement of debt	—	—	(6,776)	—	(6,776)
	—	—	(6,776)	—	(6,776)
Income before income taxes	177,108	284,201	109,165	(393,366)	177,108
Provision for income taxes	17,714	—	—	—	17,714
Net income	159,394	284,201	109,165	(393,366)	159,394
Less: Net income attributable to noncontrolling interest	(537)	—	—	—	(537)
Net income attributable to Arch Coal	$    158,857	$      284,201	$        109,165	$   (393,366)	$      158,857

CONDENSED CONSOLIDATING STATEMENTS OF INCOME

Year Ended December 31, 2009

	Parent/Issuer	Guarantor Subsidiaries	Non-Guarantor  Subsidiaries	Eliminations	Consolidated
	(In thousands)
Revenues	$             —	$  924,692	$     1,651,389	$               —	$  2,576,081
Costs, expenses and other
Cost of sales	7,481	713,782	1,398,663	(49,211)	2,070,715
Depreciation, depletion and amortization	3,678	138,125	159,805	—	301,608
Amortization of acquired sales contracts, net	—	—	19,623	—	19,623
Selling, general and administrative expenses	49,672	7,504	46,563	(5,952)	97,787
Change in fair value of coal derivatives and coal trading activities, net	—	(12,056)	—	—	(12,056)
Acquisition and transition costs	13,726	—	—	—	13,726
Other operating (income) expense, net	(12,909)	(85,460)	4,170	55,163	(39,036)
	61,648	761,895	1,628,824	—	2,452,367
Income from investment in subsidiaries	165,183	—	—	(165,183)	—
Income from operations	103,535	162,797	22,565	(165,183)	123,714
Interest expense, net:
Interest expense	(92,371)	(2,442)	(70,668)	59,549	(105,932)
Interest income	14,240	720	52,211	(59,549)	7,622
	(78,131)	(1,722)	(18,457)	—	(98,310)
Income before income taxes	25,404	161,075	4,108	(165,183)	25,404
Benefit from income taxes	(16,775)	—	—	—	(16,775)
Net income	42,179	161,075	4,108	(165,183)	42,179
Less: Net income attributable to noncontrolling interest	(10)	—	—	—	(10)
Net income attributable to Arch Coal	$     42,169	$  161,075	$             4,108	$   (165,183)	$        42,169

CONDENSED CONSOLIDATING BALANCE SHEETS

December 31, 2011

	Parent/Issuer	Guarantor  Subsidiaries	Non-Guarantor  Subsidiaries	Eliminations	Consolidated
	(In thousands)
ASSETS
Cash and cash equivalents	$  61,375	$    332	$     76,442	$         –	$  138,149
Restricted cash	10,322	–	–	–	10,322
Receivables	65,187	22,037	383,572	(1,617)	469,179
Inventories	–	207,050	170,440	–	377,490
Other	81,732	83,122	22,780	–	187,634
Total current assets	218,616	312,541	653,234	(1,617)	1,182,774
Property, plant and equipment, net	21,241	6,403,658	1,524,251	–	7,949,150
Investment in subsidiaries	8,805,731	–	–	(8,805,731)	–
Intercompany receivables	(1,457,864)	7,010	1,450,854	–	–
Note receivable from Arch Western	225,000	–	–	(225,000)	–
Other	184,266	884,613	13,156	–	1,082,035
Total other assets	7,757,133	891,623	1,464,010	(9,030,731)	1,082,035
Total assets	$  7,996,990	$7,607,822	$  3,641,495	(9,032,348)	$10,213,959
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable	$   25,409	$ 175,196	$ 183,177	$    –	$  383,782
Accrued expenses and other current liabilities	75,133	115,685	166,834	(1,617)	356,035
Current maturities of debt and short-term borrowings	172,564	1,987	106,300	–	280,851
Total current liabilities	273,106	292,868	456,311	(1,617)	1,020,668
Long-term debt	3,308,674	2,652	450,971		3,762,297
Note payable to Arch Coal	–	–	225,000	(225,000)	–
Asset retirement obligations	877	140,861	305,046	–	446,784
Accrued pension benefits	19,198	4,203	24,843	–	48,244
Accrued postretirement benefits other than pension	13,843	6,271	22,195	–	42,309
Accrued workers' compensation	17,272	48,111	6,565	–	71,948
Deferred income taxes	621,483	355,270	–	–	976,753
Other noncurrent liabilities	152,963	64,795	37,624	–	255,382
Total liabilities	4,407,416	915,031	1,528,555	(226,617)	6,624,385
Redeemable noncontrolling interest	11,534	–	–	–	11,534
Stockholders' equity	3,578,040	6,692,791	2,112,940	(8,805,731)	3,578,040
Total liabilities and stockholders' equity	$  7,996,990	$7,607,822	$ 3,641,495	$ (9,032,348)	$10,213,959

CONDENSED CONSOLIDATING BALANCE SHEETS

December 31, 2010

	Parent/Issuer	Guarantor  Subsidiaries	Non-Guarantor   Subsidiaries	Eliminations	Consolidated
	(In thousands)
ASSETS
Cash and cash equivalents	$          13,713	$                64	$        79,816	$                  —	$        93,593
Receivables	31,458	12,740	210,075	(1,953)	252,320
Inventories	—	85,196	150,420	—	235,616
Other	29,575	102,375	21,435	—	153,385
Total current assets	74,746	200,375	461,746	(1,953)	734,914
Property, plant and equipment, net	9,817	1,800,578	1,498,497	—	3,308,892
Investment in subsidiaries	4,555,233	—	—	(4,555,233)	—
Intercompany receivables	(1,807,902)	508,624	1,299,278	—	—
Note receivable from Arch Western	225,000	—	—	(225,000)	—
Other	481,345	344,698	10,920	—	836,963
Total other assets	3,453,676	853,322	1,310,198	(4,780,233)	836,963
Total assets	$    3,538,239	$  2,854,275	$  3,270,441	$   (4,782,186)	$  4,880,769
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable	$          10,753	$        65,793	$      121,670	$                  —	$     198,216
Accrued expenses and other current liabilities	75,746	31,123	153,217	(1,953)	258,133
Current maturities of debt and short-term borrowings	14,093	—	56,904	—	70,997
Total current liabilities	100,592	96,916	331,791	(1,953)	527,346
Long-term debt	1,087,126	—	451,618	—	1,538,744
Note payable to Arch Coal	—	—	225,000	(225,000)	—
Asset retirement obligations	873	32,029	301,355	—	334,257
Accrued pension benefits	20,843	4,407	23,904	—	49,154
Accrued postretirement benefits other than pension	14,284	—	23,509	—	37,793
Accrued workers' compensation	15,383	13,805	6,102	—	35,290
Other noncurrent liabilities	51,187	22,135	36,912	—	110,234
Total liabilities	1,290,288	169,292	1,400,191	(226,953)	2,632,818
Redeemable noncontrolling interest	10,444	—	—	—	10,444
Stockholders' equity	2,237,507	2,684,983	1,870,250	(4,555,233)	2,237,507
Total liabilities and stockholders' equity	$    3,538,239	$  2,854,275	$  3,270,441	$   (4,782,186)	$  4,880,769

CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS

Year Ended December 31, 2011

	Parent/Issuer	Guarantor   Subsidiaries	Non-Guarantor   Subsidiaries	Eliminations	Consolidated
		(In thousands)
Cash provided by (used in) operating activities	$ (561,704)	$801,201	$ 402,745	$          –	$ 642,242
Investing Activities
Acquisitions of businesses, net of cash acquired	(2,894,339)	–	–	–	(2,894,339)
Decrease in restricted cash	5,167	–	–	–	5,167
Capital expenditures	(12,809)	(353,441)	(174,686)	–	(540,936)
Proceeds from dispositions of property, plant and equipment	–	25,730	157	–	25,887
Additions to prepaid royalties	-	(25,982)	(3,975)	-	(29,957)
Purchases of investments and advances to affiliates	(633,534)	(33,553)	-	605,178	(61,909)
Consideration paid related to prior business acquisitions	(829)	–	–	–	(829)
Cash used in investing activities	(3,536,344)	(387,246)	(178,504)	605,178	(3,496,916)
Financing Activities
Proceeds from the issuance of senior notes	2,000,000	–	–	–	2,000,000
Proceeds from the issuance of common stock, net	1,267,933	–	–	–	1,267,933
Contributions from parent	–	605,178	–	(605,178)	–
Payments to retire debt	–	(605,178)	–	–	(605,178)
Net increase (decrease) in borrowings under lines of credit and commercial paper program	481,300	–	(56,904)	–	424,396
Net proceeds from other debt	5,334	–	–	–	5,334
Debt financing costs	(114,799)	–	(24)	–	(114,823)
Dividends paid	(80,748)	–	–	–	(80,748)
Issuance of common stock under incentive plans	2,316	–	–	–	2,316
Transactions with affiliates, net	584,374	(413,687)	(170,687)	–	–
Cash provided by (used in) financing activities	4,145,710	(413,687)	(227,615)	(605,178)	2,899,230
Increase (decrease) in cash and cash equivalents	47,662	268	(3,374)	–	44,556
Cash and cash equivalents, beginning of period	13,713	64	79,816	–	93,593
Cash and cash equivalents, end of period	$  61,375	$   332	$   76,442	$               –	$   138,149

CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS

Year Ended December 31, 2010

	Parent/Issuer	Guarantor  Subsidiaries	Non-Guarantor   Subsidiaries	Consolidated
	(In thousands)
Cash provided by (used in) operating activities	$   (238,736)	$    503,766	$    432,117	$    697,147
Investing Activities
Capital expenditures	(4,814)	(198,243)	(111,600)	(314,657)
Proceeds from dispositions of property, plant and equipment	—	251	79	330
Additions to prepaid royalties	—	(24,381)	(2,974)	(27,355)
Purchases of investments and advances to affiliates	(40,421)	(5,764)	—	(46,185)
Consideration paid related to prior business acquisitions	(1,262)	—	—	(1,262)
Cash used in investing activities	(46,497)	(228,137)	(114,495)	(389,129)
Financing Activities
Proceeds from the issuance of senior notes	500,000	—	—	500,000
Payments to retire debt	—	—	(505,627)	(505,627)
Net decrease in borrowings under lines of credit and commercial paper program	(120,000)	—	(76,549)	(196,549)
Net proceeds from other debt	82	—	—	82
Debt financing costs	(12,022)	—	(729)	(12,751)
Dividends paid	(63,373)	—	—	(63,373)
Issuance of common stock under incentive plans	1,764			1,764
Contribution from noncontrolling interest	—	—	891	891
Transactions with affiliates, net	(61,760)	(275,629)	337,389	—
Cash provided by (used in) financing activities	244,691	(275,629)	(244,625)	(275,563)
Increase (decrease) in cash and cash equivalents	(40,542)	—	72,997	32,455
Cash and cash equivalents, beginning of period	54,255	64	6,819	61,138
Cash and cash equivalents, end of period	$      13,713	$              64	$      79,816	$      93,593

CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS

Year Ended December 31, 2009

	Parent/Issuer	Guarantor  Subsidiaries	Non-Guarantor Subsidiaries	Consolidated
	(In thousands)
Cash provided by (used in) operating activities	$   (168,427)	$    338,956	$    212,451	$       382,980
Investing Activities
Acquisitions of businesses, net of cash acquired	(768,819)	—	—	(768,819)
Capital expenditures	(2,940)	(194,756)	(125,454)	(323,150)
Proceeds from dispositions of property, plant and equipment	—	734	91	825
Additions to prepaid royalties	—	(23,991)	(2,764)	(26,755)
Purchases of investments and advances to affiliates	(8,000)	(2,925)	—	(10,925)
Consideration paid related to prior business acquisitions	(4,767)	—	—	(4,767)
Reimbursement of deposits on equipment	—	—	3,209	3,209
Cash used in investing activities	(784,526)	(220,938)	(124,918)	(1,130,382)
Financing Activities
Proceeds from the issuance of senior notes	584,784	—	—	584,784
Proceeds from the sale of common stock, net	326,452	—	—	326,452
Net decrease in borrowings under lines of credit and commercial paper program	(85,000)	—	(815)	(85,815)
Net payments on other debt	(2,986)	—	—	(2,986)
Debt financing costs	(29,456)	—	(203)	(29,659)
Dividends paid	(54,969)	—	—	(54,969)
Issuance of common stock under incentive plans	84	—	—	84
Transactions with affiliates, net	200,562	(118,015)	(82,547)	—
Cash provided by (used in) financing activities	939,471	(118,015)	(83,565)	737,891
Increase (decrease) in cash and cash equivalents	(13,482)	3	3,968	(9,511)
Cash and cash equivalents, beginning of period	67,737	61	2,851	70,649
Cash and cash equivalents, end of period	$      54,255	$              64	$        6,819	$          61,138

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Derivatives (Effects Of Derivatives On Measures Of Financial Performance) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Derivative [Line Items]
Gain (Loss) Recognized in OCI (Effective Portion)	$ 4,208	$ 282	$ 3,957
Gains (Losses) Reclassified from OCI into Income (Effective Portion)	16,438	(2,367)	(69,235)
Coal Purchases [Member]
Derivative [Line Items]
Gain (Loss) Recognized in OCI (Effective Portion)	(2,009)	5,145	1,089
Gains (Losses) Reclassified from OCI into Income (Effective Portion)		(1,202)	(13,181)
Coal Sales [Member]
Derivative [Line Items]
Gain (Loss) Recognized in OCI (Effective Portion)	4,923	(4,714)	(7,441)
Gains (Losses) Reclassified from OCI into Income (Effective Portion)	1,572	(1,602)	(6,999)
Coal [Member] | Change In Fair Value Of Coal Derivatives And Coal Trading Activities Net [Member]
Derivative [Line Items]
Derivatives Not Designated as Hedging Instruments, Gains (Losses), Unrealized	6,438	(10,991)	9,673
Gain on Derivatives Used in Fair Value Hedge Relationships			2,586
Coal [Member] | Other Operating Income, Net [Member]
Derivative [Line Items]
Derivatives Not Designated as Hedging Instruments, Gain, Realized		4,542
Derivatives Not Designated as Hedging Instruments, Losses, Realized	(7)
Heating Oil - Diesel Purchases [Member]
Derivative [Line Items]
Gain (Loss) Recognized in OCI (Effective Portion)	1,294	(149)	10,309
Heating Oil - Diesel Purchases [Member] | Coal Purchases [Member]
Derivative [Line Items]
Gains (Losses) Reclassified from OCI into Income (Effective Portion)	14,866	437	(49,055)
Heating Oil - Fuel Surcharges [Member] | Other Operating Income, Net [Member]
Derivative [Line Items]
Derivatives Not Designated as Hedging Instruments, Gains (Losses), Unrealized	(2,906)
Firm Commitments [Member] | Change In Fair Value Of Coal Derivatives And Coal Trading Activities Net [Member]
Derivative [Line Items]
Loss on Hedged Items in Fair Value Hedge Relationships			$ (2,586)

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Schedule II - Valuation And Qualifying Accounts (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Other Assets - Other Notes And Accounts Receivable [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year			$ 109		$ 225
Additions (Reductions) Charged to Costs and Expenses	17				(17)
Charged to Other Accounts
Deductions			109	[1]	99	[1]
Balance at End of Year	17				109
Current Assets - Supplies And Inventory [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	12,701		13,406		12,760
Additions (Reductions) Charged to Costs and Expenses	1,755		1,962		1,302
Charged to Other Accounts
Deductions	1,349	[1]	2,667	[1]	656	[1]
Balance at End of Year	13,107		12,701		13,406
Deferred Income Taxes [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	737		1,120		395
Additions (Reductions) Charged to Costs and Expenses	2,416		(383)		725
Charged to Other Accounts
Deductions	322	[1]				[1]
Balance at End of Year	$ 2,831		$ 737		$ 1,120

[1] Reserves utilized, unless otherwise indicated.

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Equity Investments And Membership Interests In Joint Ventures (Summarized Financial Information Of Equity Method Investments) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Equity Investments And Membership Interests In Joint Ventures [Abstract]
Revenues	$ 184,358	$ 172,933	$ 166,152
Gross profit	19,495	25,203	15,426
Income from operations	13,180	20,243	1,611
Net income (loss)	6,788	16,015	(1,797)
Current assets	94,644	48,202
Noncurrent assets	331,848	276,125
Total assets	426,492	324,327
Current liabilities	51,674	39,237
Noncurrent liabilities	120,494	99,350
Equity	254,163	185,639
Noncontrolling interest	161	101
Total liabilities and equity	$ 426,492	$ 324,327

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Asset Retirement Obligations (Schedule Of Asset Retirement Obligations) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Asset Retirement Obligations [Abstract]
Balance at January 1 (including current portion)	$ 343,119	$ 310,409
Accretion expense	33,601	26,615
Obligations incurred or acquired	115,019
Adjustments to the liability from changes in estimates	11,176	8,934
Liabilities settled	(29,012)	(2,839)
Balance at December 31	473,903	343,119
Current portion included in accrued expenses	(27,119)	(8,862)
Noncurrent liability	$ 446,784	$ 334,257

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Valuation And Qualifying Accounts (Tables)

12 Months Ended

Dec. 31, 2011

Valuation And Qualifying Accounts [Abstract]

Valuation And Qualifying Accounts

	Balance at Beginning    of Year	Additions     (Reductions) Charged to Costs and Expenses	Charged to        Other    Accounts	Deductions(a)	Balance at End of Year
	(In thousands)
Year ended December 31, 2011
Reserves deducted from asset accounts:
Other assets — other notes and accounts receivable	$           —	$            17	$          —	$        —	$          17
Current assets — supplies and inventory	12,701	1,755	—	1,349	13,107
Deferred income taxes	737	2,416	—	322	2,831
Year ended December 31, 2010
Reserves deducted from asset accounts:
Other assets — other notes and accounts receivable	$        109	$            —	$          —	$      109	$           —
Current assets — supplies and inventory	13,406	1,962	—	2,667	12,701
Deferred income taxes	1,120	(383)	—	—	737
Year ended December 31, 2009
Reserves deducted from asset accounts:
Other assets — other notes and accounts receivable	$        225	$           (17)	$          —	$        99	$        109
Current assets — supplies and inventory	12,760	1,302	—	656	13,406
Deferred income taxes	395	725	—	—	1,120

____________

(a) Reserves utilized, unless otherwise indicated.

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Leases (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Operating Leased Assets [Line Items]
Rental expense	$ 43,900,000	$ 41,600,000	$ 43,300,000
Royalty expense	349,000,000	286,800,000	230,500,000
Surety bonds outstanding	263,000,000
Secured lease obligation outstanding	263,000,000
Operating Lease [Member]
Operating Leased Assets [Line Items]
2011	28,903,000
2012	27,610,000
2013	25,119,000
2014	17,641,000
2015	9,648,000
Thereafter	12,640,000
Total	121,561,000
Leases [Member]
Operating Leased Assets [Line Items]
Surety bonds outstanding	64,600,000
Secured lease obligation outstanding	64,600,000
Royalty Agreements [Member] | Royalties [Member]
Operating Leased Assets [Line Items]
2011	24,378,000
2012	25,595,000
2013	25,810,000
2014	27,565,000
2015	24,397,000
Thereafter	114,371,000
Total	$ 242,116,000

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Derivative Instruments (Derivative For Risk Management Purposes) (Details)	Dec. 31, 2011
Coal Purchases [Member] | One Year From Balance Sheet Date [Member]
Derivative [Line Items]
Quantities under derivative contracts, tons	254,000
Coal Purchases [Member] | More Than One And Within Two Years From Balance Sheet Date [Member]
Derivative [Line Items]
Quantities under derivative contracts, tons
Coal Purchases [Member] | More Than Two And Within Three Years From Balance Sheet Date [Member]
Derivative [Line Items]
Quantities under derivative contracts, tons
Coal Purchases [Member] | More Than Three And Within Four Years From Balance Sheet Date [Member]
Derivative [Line Items]
Quantities under derivative contracts, tons
Coal Sales [Member] | One Year From Balance Sheet Date [Member]
Derivative [Line Items]
Quantities under derivative contracts, tons	2,416,000
Coal Sales [Member] | More Than One And Within Two Years From Balance Sheet Date [Member]
Derivative [Line Items]
Quantities under derivative contracts, tons	1,117,000
Coal Sales [Member] | More Than Two And Within Three Years From Balance Sheet Date [Member]
Derivative [Line Items]
Quantities under derivative contracts, tons	1,440,000
Coal Sales [Member] | More Than Three And Within Four Years From Balance Sheet Date [Member]
Derivative [Line Items]
Quantities under derivative contracts, tons	720,000

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Fair Value Measurements (Summary Of Financial Assets And Liabilities Accounted For At Fair Value) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Assets:
Investments in equity securities	$ 7,540
Derivatives	24,129	28,666
Total assets	31,669
Liabilities:
Derivatives	7,828	4,947
Level 1 [Member]
Assets:
Investments in equity securities	7,540
Derivatives	12,361
Total assets	19,901
Liabilities:
Derivatives
Level 2 [Member]
Assets:
Investments in equity securities
Derivatives	1,450
Total assets	1,450
Liabilities:
Derivatives	3,721
Level 3 [Member]
Assets:
Derivatives	10,318
Total assets	10,318
Liabilities:
Derivatives	$ 4,107

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Taxes (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Taxes [Abstract]
Stock options and other equity based compensation, tax expense (benefit)	$ (0.4)	$ (0.8)	$ 0.2
Operating loss carryforwards	779.1			145.1
Operating loss carryforwards, expiration dates		expire between 2012 and 2031
Tax credit carryforward	151.4
Future cash tax benefits accrue	0.8	1.3	4.8
Increases (decreases) in valuation allowance	2.1	(0.4)	0.7
Interest and penalties accrued related to unrecognized tax benefits	0.8	0.6
Interest and penalties recognized	$ 0.2	$ 0.1

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Fair Value Measurements (Summary Of Change In The Fair Values Of Financial Instruments Categorized As Level 3) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Fair Value Measurements [Abstract]
Balance, beginning of period	$ 9,183
Realized and unrealized losses recognized in earnings, net	(16,727)
Realized and unrealized losses recognized in other comprehensive income, net	(4,122)
Purchases	23,867
Issuances	(2,160)
Settlements	(3,830)
Balance, end of period	$ 6,211

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Derivative Instruments (Disclosure Of Fair Value Of Derivatives) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Derivative [Line Items]
Asset Derivative	$ 42,263	$ 51,068
Liability Derivative	(25,962)	(27,349)
Effect of counterparty netting, Asset Derivative	(18,134)	(22,402)
Effect of counterparty netting, Liability Derivative	18,134	22,402
Net derivative assets as classified in the balance sheet	24,129	28,666
Net derivative liabilities as classified in the balance sheet	(7,828)	(4,947)
Net derivatives as classified in the balance sheet	16,301	23,719
Designated As Hedging Instrument [Member]
Derivative [Line Items]
Asset Derivative	10,106	15,484
Liability Derivative		(2,350)
Designated As Hedging Instrument [Member] | Heating Oil - Diesel Purchases [Member]
Derivative [Line Items]
Asset Derivative	8,997	13,475
Liability Derivative
Designated As Hedging Instrument [Member] | Coal [Member]
Derivative [Line Items]
Asset Derivative	1,109	2,009
Liability Derivative		(2,350)
Not Designated As Hedging Instrument [Member]
Derivative [Line Items]
Asset Derivative	32,157	35,584
Liability Derivative	(25,962)	(24,999)
Not Designated As Hedging Instrument [Member] | Heating Oil - Fuel Surcharges [Member]
Derivative [Line Items]
Asset Derivative	1,797
Liability Derivative
Not Designated As Hedging Instrument [Member] | Coal Held For Trading Purposes [Member]
Derivative [Line Items]
Asset Derivative	15,505	34,445
Liability Derivative	(19,927)	(24,087)
Not Designated As Hedging Instrument [Member] | Coal [Member]
Derivative [Line Items]
Asset Derivative	14,855	1,139
Liability Derivative	$ (6,035)	$ (912)

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Equity Investments And Membership Interests In Joint Ventures (Narrative) (Details) (USD $)	3 Months Ended	12 Months Ended				1 Months Ended		3 Months Ended	12 Months Ended					12 Months Ended				12 Months Ended				12 Months Ended				1 Months Ended	12 Months Ended				12 Months Ended
	Jun. 30, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2010 Knight Hawk [Member]	Jun. 30, 2010 Knight Hawk [Member]	Jun. 30, 2010 Knight Hawk [Member]	Dec. 31, 2011 Knight Hawk [Member]	Dec. 31, 2010 Knight Hawk [Member]	Dec. 31, 2009 Knight Hawk [Member]	May 31, 2010 Knight Hawk [Member]	Dec. 31, 2008 Knight Hawk [Member]	Dec. 31, 2011 DKRW [Member]	Dec. 31, 2010 DKRW [Member]	Dec. 31, 2009 DKRW [Member]	Dec. 31, 2008 DKRW [Member]	Dec. 31, 2011 DTA [Member]	Dec. 31, 2010 DTA [Member]	Dec. 31, 2009 DTA [Member]	Dec. 31, 2008 DTA [Member]	Dec. 31, 2011 Tenaska [Member]	Dec. 31, 2010 Tenaska [Member]	Dec. 31, 2009 Tenaska [Member]	Dec. 31, 2008 Tenaska [Member]	Jan. 31, 2011 Millennium [Member]	Dec. 31, 2011 Millennium [Member]	Dec. 31, 2010 Millennium [Member]	Dec. 31, 2009 Millennium [Member]	Dec. 31, 2008 Millennium [Member]	Dec. 31, 2011 Tongue River [Member]	Dec. 31, 2010 Tongue River [Member]	Dec. 31, 2009 Tongue River [Member]	Jul. 31, 2011 Tongue River [Member]	Dec. 31, 2008 Tongue River [Member]	Jun. 30, 2010 Reserves [Member] Knight Hawk [Member]	Jun. 30, 2010 Goods and Services Exchanged for Equity Instrument [Member] Knight Hawk [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest						49.00%	42.00%	42.00%		49.00%		33.33%		24.00%				21.875%				35.00%				38.00%								33.00%
Tons Of Coal																																				68,400,000
Additional ownership interest							9.00%	9.00%
Nonmonetary Transaction, Gain (Loss) Recognized on Transfer	$ 41,600,000		$ 41,577,000				$ 41,600,000
Mineral Properties, Net																																					12,100,000
Investments in and Advances to Affiliates, at Fair Value, Period Increase (Decrease)		(6,646,000)	(8,375,000)	(2,239,000)					(16,621,000)	(12,639,000)	(5,164,000)							6,498,000	4,264,000	2,925,000							3,477,000
Investments in and Advances to Affiliates, at Fair Value, Gross Additions		43,489,000	87,405,000			26,600,000				77,637,000												5,500,000	9,768,000			25,000,000	25,000,000				12,989,000
Interest Rate on Note Receivable														1.25%
Notes receivable from investees		35,810,000	23,900,000			1,700,000				1,700,000				30,751,000	18,100,000							5,059,000	4,100,000
Future development costs, percentage																						35.00%
Future development costs, maximum limit		74,400,000																				12,500,000
Equity investments		$ 225,605,000	$ 177,451,000	$ 87,268,000	$ 87,761,000	$ 131,250,000			$ 135,225,000	$ 131,250,000	$ 49,603,000		$ 48,093,000	$ 19,715,000	$ 21,961,000	$ 23,589,000	$ 25,124,000	$ 16,086,000	$ 14,472,000	$ 14,076,000	$ 14,544,000	$ 15,266,000	$ 9,768,000				$ 26,324,000				$ 12,989,000

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Stock Based Compensation And Other Incentive Plans

12 Months Ended

Dec. 31, 2011

Stock Based Compensation And Other Incentive Plans [Abstract]

Stock Based Compensation And Other Incentive Plans

18.  Stock Based Compensation and Other Incentive Plans

Under the Company's Stock Incentive Plan (the "Incentive Plan"), 18,000,000 shares of the Company's common stock are reserved for awards to officers and other selected key management employees of the Company. The Incentive Plan provides the Board of Directors with the flexibility to grant stock options, stock appreciation rights, restricted stock awards, restricted stock units, performance stock or units, merit awards, phantom stock awards and rights to acquire stock through purchase under a stock purchase program ("Awards"). Awards the Board of Directors elects to pay out in cash do not count against the 18,000,000 shares authorized in the Incentive Plan. The Incentive Plan calls for the adjustment of shares awarded under the plan in the event of a split.

As of December 31, 2011, the Company had stock options, restricted stock and restricted stock units outstanding under the Incentive Plan.

Stock Options

Stock options are granted at a price equal to the closing market price of the Company's common stock on the date of grant and are generally subject to vesting provisions of at least one year from the date of grant. Information regarding stock option activity under the Incentive Plan follows for the year ended December 31, 2011:

	Common       Shares	Weighted Average Exercise Price	Aggregate      Intrinsic        Value	Average Contract     Life
	(In thousands)		(In thousands)
Options outstanding at January 1	4,544	$  25.18
Granted	728	32.18
Exercised	(199)	11.61
Canceled	(88)	23.74
Expired	(32)	52.69
Options outstanding at December 31	4,953	26.60	$     4,107	5.76
Options exercisable at December 31	3,157	27.59	3,887	4.35

The aggregate intrinsic value of options exercised during the years ended December 31, 2011, 2010 and 2009 was $2.6 million, $3.0 million and $0.1 million, respectively.

Information regarding changes in stock options outstanding and not yet vested and the related grant-date fair value under the Incentive Plan follows for the year ended December 31, 2011:

	Common Shares	Weighted Average Grant-Date Fair Value
	(In thousands)
Unvested options at January 1	1,901	$  10.61
Granted	728	14.18
Vested	(746)	13.28
Canceled	(87)	10.35
Unvested options at December 31	1,796	10.96

Compensation expense related to stock options for the years ended December 31, 2011, 2010 and 2009 was $8.8 million, $10.6 million and $11.8 million, respectively. As of December 31, 2011, there was $8.2 million of unrecognized compensation cost related to the unvested stock options. The total grant-date fair value of options vested during the years ended December 31, 2011, 2010 and 2009 was $9.9 million, $10.6 million and $9.1 million, respectively. The options provide for the continuation of vesting for retirement-eligible recipients that meet certain criteria. The expense for these options is recognized through the date that the employee first becomes eligible to retire and is no longer required to provide service to earn part or all of the award. The majority of the cost relating to the stock-based compensation plans is included primarily in selling, general and administrative expenses in the accompanying consolidated statements of income.

Weighted average assumptions used in the Black-Scholes option pricing model for granted options follow:

	Year Ended December 31
	2011	2010	2009
Weighted average grant-date fair value per share of options granted	$ 14.18	$  9.43	$     6.63
Assumptions (weighted average):
Risk-free interest rate	1.92%	2.16%	1.75%
Expected dividend yield	1.25%	1.99%	2.56%
Expected volatility	57.4%	57.1%	69.3%
Expected life (in years)	4.5	4.5	4.5

Expected volatilities are based on historical stock price movement and implied volatility from traded options on the Company's stock. The expected life of the option was determined based on historical exercise activity. Most options granted vest over a period of four years.

Restricted Stock and Restricted Stock Unit Awards

The Company may issue restricted stock and restricted stock units, which require no payment from the employee. Restricted stock cliff-vests at various dates and restricted stock units typically vest ratably over three years. Compensation expense is based on the fair value on the grant date and is recorded ratably over the vesting period. During the vesting period, the employee receives cash compensation equal to the amount of dividends that would have been paid on the underlying shares.

Information regarding restricted stock and restricted stock unit activity and weighted average grant-date fair value follows for the year ended December 31, 2011:

	Restricted Stock		Restricted Stock Units
	Common       Shares	Weighted Average Grant-Date Fair Value	Common       Shares	Weighted Average Grant-Date Fair Value
	(In thousands)		(In thousands)
Outstanding at January 1	74	$  24.69	54	$  52.69
Granted	140	30.42	—	—
Vested	(27)	39.77	(27)	52.69
Canceled	(5)	32.49	—	—
Outstanding at December 31	182	26.68	27	52.69

The weighted average fair value of restricted stock granted during 2010 and 2009 was $22.03 and $14.05, respectively. There were no restricted stock units granted during 2010 or 2009. The total grant-date fair value of restricted stock that vested during 2011, 2010 and 2009 was $1.1 million, $0.4 million and $1.5 million, respectively. The total grant-date fair value of restricted stock units that vested during 2011 and 2009 was $1.4 million and $0.4 million, respectively. There were no restricted stock units that vested during 2010. Unearned compensation of $3.4 million will be recognized over the remaining vesting period of the outstanding restricted stock and restricted stock units. The Company recognized expense of approximately $2.1 million, $1.1 million and $1.7 million related to restricted stock and restricted stock units for the years ended December 31, 2011, 2010 and 2009, respectively, primarily in selling, general and administrative expenses.

Long-Term Incentive Compensation

The Company has a long-term incentive program that allows for the award of performance units. The total number of units earned by a participant is based on financial and operational performance measures, and may be paid out in cash or in shares of the Company's common stock. The Company recognizes compensation expense over the three year term of the grant. The liabilities are remeasured quarterly. The Company recognized $2.7 million, $3.8 million and $2.6 million for the years ended December 31, 2011, 2010 and 2009, respectively. The expense is included primarily in selling, general and administrative expenses in the accompanying consolidated statements of income. Amounts accrued under the plan were $9.6 million and $6.4 million at December 31, 2011 and 2010, respectively.

Deferred Compensation Plan

The Company maintains a deferred compensation plan that allows eligible employees to defer receipt of compensation until the dates elected by the participant. Participants in the plan may defer up to 85% of their base salaries and up to 100% of their annual incentive awards. The plan also allows participants to defer receipt of up to 100% of the shares under any restricted stock unit or performance-contingent stock awards. The amounts deferred are invested in accounts that mirror the gains and losses of a number of different investment funds, including a hypothetical investment in shares of the Company's common stock. Participants are always vested in their deferrals to the plan and any related earnings. The Company has established a grantor trust to fund the obligations under the plan. The trust has purchased corporate-owned life insurance to offset these obligations. The net cash surrender values of the policies of $35.8 million and $40.7 million at December 31, 2011 and 2010, respectively, are included in other noncurrent assets in the accompanying consolidated balance sheets. The participants have an unsecured contractual commitment by the Company to pay the amounts due under the plan. Any assets placed in trust by the Company to fund future obligations of the plan are subject to the claims of creditors in the event of insolvency or bankruptcy, and participants are general creditors of the company as to their deferred compensation in the plans.

Under the plan, the Company credits each participant's account with the number of units equal to the number of shares or units that the participant could purchase or receive with the amount of compensation deferred, based upon the fair market value of the underlying investment on that date. The amount the employee will receive from the plan will be based on the number of units credited to each participant's account, valued on the basis of the fair market value of an equivalent number of shares or units of the underlying investment on that date. The liability under the plan was $32.7 million at December 31, 2011 and $38.5 million at December 31, 2010.

The Company's net income (expense) related to the deferred compensation plan for the years ended December 31, 2011, 2010 and 2009 was $6.2 million, $(2.8) million and $4.1 million, respectively, most of which is included in selling, general and administrative expenses in the accompanying consolidated statements of income.

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Stock Based Compensation And Other Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2011

Stock Based Compensation And Other Incentive Plans [Abstract]

Schedule Of Stock Option Activity Under Incentive Plan

	Common       Shares	Weighted Average Exercise Price	Aggregate      Intrinsic        Value	Average Contract     Life
	(In thousands)		(In thousands)
Options outstanding at January 1	4,544	$  25.18
Granted	728	32.18
Exercised	(199)	11.61
Canceled	(88)	23.74
Expired	(32)	52.69
Options outstanding at December 31	4,953	26.60	$     4,107	5.76
Options exercisable at December 31	3,157	27.59	3,887	4.35

Changes In Stock Options Outstanding And Not Yet Vested And Related Grant-Date Fair Value Under The Incentive Plan

	Common Shares	Weighted Average Grant-Date Fair Value
	(In thousands)
Unvested options at January 1	1,901	$  10.61
Granted	728	14.18
Vested	(746)	13.28
Canceled	(87)	10.35
Unvested options at December 31	1,796	10.96

Weighted Average Assumptions Used In Option Pricing

	Year Ended December 31
	2011	2010	2009
Weighted average grant-date fair value per share of options granted	$ 14.18	$  9.43	$     6.63
Assumptions (weighted average):
Risk-free interest rate	1.92%	2.16%	1.75%
Expected dividend yield	1.25%	1.99%	2.56%
Expected volatility	57.4%	57.1%	69.3%
Expected life (in years)	4.5	4.5	4.5

Restricted Stock And Restricted Stock Unit Activity And Weighted Average Grant-Date Fair Value

	Restricted Stock		Restricted Stock Units
	Common       Shares	Weighted Average Grant-Date Fair Value	Common       Shares	Weighted Average Grant-Date Fair Value
	(In thousands)		(In thousands)
Outstanding at January 1	74	$  24.69	54	$  52.69
Granted	140	30.42	—	—
Vested	(27)	39.77	(27)	52.69
Canceled	(5)	32.49	—	—
Outstanding at December 31	182	26.68	27	52.69

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Inventories (Tables)

12 Months Ended

Dec. 31, 2011

Inventories [Abstract]

Inventories

	December 31
	2011	2010
	(In thousands)
Coal	$  206,517	$  115,647
Repair parts and supplies	163,527	119,969
Work-in-process	7,446	—
	$  377,490	$  235,616

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Derivative Instruments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Derivative [Line Items]
Percent of diesel purchases hedged	82.00%
Net unrealized and realized gains (losses) related to trading portfolio	$ (3.5)	$ 2.1	$ 2.4
Gain on derivative contracts designated as hedge instruments in cash flow hedges to be reclassified from OCI into earnings during the next twelve months	9.2
Minimum Purchase [Member]
Derivative [Line Items]
Gallons of diesel fuel purchased annually	80,000,000
Maximum Purchase [Member]
Derivative [Line Items]
Gallons of diesel fuel purchased annually	90,000,000
2012 [Member]
Derivative [Line Items]
Value of trading portfolio realized	(2.6)
2013 [Member]
Derivative [Line Items]
Value of trading portfolio realized	(1.8)
Heating Oil - Fuel Surcharges [Member]
Derivative [Line Items]
Quantities under derivative contracts, tons	19,100,000
Current Assets [Member]
Derivative [Line Items]
Current asset for the right to reclaim cash collateral	$ 12.4	$ 10.3
Heating Oil [Member] | Heating Oil - Diesel Purchases [Member]
Derivative [Line Items]
Quantities under derivative contracts, tons	69,000,000

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Employee Benefit Plans (Schedule Of Assumptions Used To Calculate Benefit Obligation) (Details)	Dec. 31, 2011	Dec. 31, 2010
Pension Benefits [Member]
Discount rate	4.91%	5.71%
Rate of compensation increase	3.39%	3.39%
Other Postretirement Benefits [Member]
Discount rate	4.52%	5.23%
Rate of compensation increase	0.00%	0.00%

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Goodwill (Tables)

12 Months Ended

Dec. 31, 2011

Goodwill [Abstract]

Schedule Of Goodwill

		(In thousands)
Balance at January 1, 2009	$	46,832
Consideration paid related to prior business acquisitions		4,767
Acquisition of Jacobs Ranch		62,102
Balance at December 31, 2009		113,701
Consideration paid related to prior business acquisitions		1,262
Balance at December 31, 2010		114,963
Consideration paid related to prior business acquisitions		829
Acquisition of ICG		480,311
Balance at December 31, 2011	$	596,103

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Earnings Per Common Share (Tables)

12 Months Ended

Dec. 31, 2011

Earnings Per Common Share [Abstract]

Earnings Per Share

	Year Ended December 31
	2011	2010	2009
	(In thousands)
Weighted average shares outstanding:
Basic weighted average shares outstanding	190,086	162,398	150,963
Effect of common stock equivalents under incentive plans	819	812	309
Diluted weighted average shares outstanding	190,905	163,210	151,272

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Debt And Financing Arrangements (Schedule Of Debt) (Details) (USD $)			12 Months Ended					12 Months Ended		12 Months Ended		12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 7.00% Senior Notes Due June 15, 2019 [Member]	Dec. 31, 2011 7.25% Senior Notes Due June 15, 2021 [Member]	Jun. 14, 2011 9.125% Senior Notes Due April 1, 2018 [Member]	Jun. 14, 2011 4.00% Convertible Senior Notes Due April 1, 2017 [Member]	Jun. 14, 2011 9.00% Convertible Senior Notes Due August 1, 2012 [Member]	Dec. 31, 2011 6.75% Senior Notes Due July 1, 2013 [Member]	Dec. 31, 2010 6.75% Senior Notes Due July 1, 2013 [Member]	Dec. 31, 2011 8.75% Senior Notes Due August 1, 2016 [Member]	Dec. 31, 2010 8.75% Senior Notes Due August 1, 2016 [Member]	Dec. 31, 2011 7.25% Senior Notes Due October 10, 2020 [Member]	Dec. 31, 2010 7.25% Senior Notes Due October 10, 2020 [Member]
Debt Instrument [Line Items]
Commercial paper		$ 56,904,000
Indebtedness to banks under credit facilities	481,300,000
Senior notes			1,000,000,000	1,000,000,000				450,971,000	451,618,000	588,974,000	587,126,000	500,000,000	500,000,000
Other	21,903,000	14,093,000
Total	4,043,148,000	1,609,741,000
Less current maturities of debt and short-term borrowings	280,851,000	70,997,000
Long-term debt	3,762,297,000	1,538,744,000
Face value of senior notes								$ 450,000,000		$ 600,000,000
Senior notes interest rate			7.00%	7.25%	9.125%	4.00%	9.00%	6.75%		8.75%		7.25%
Due date of senior notes			Jun. 15, 2019	Jun. 15, 2021				Jul. 01, 2013		Aug. 01, 2016		Oct. 01, 2020

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Contingencies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Loss Contingencies [Line Items]
Purchase replacement coal	$ 100
Damages and interest awarded	104.1
Appeal bond	124.9
Amount accrued	108.3
Interest recognized post-acquisition	3.4
Minimum [Member]
Loss Contingencies [Line Items]
Aggregate amount of past and future damages	228.0
Maximum [Member]
Loss Contingencies [Line Items]
Aggregate amount of past and future damages	$ 377.0

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Business Combinations (Summary Of Purchase Price Allocation) (Details) (USD $)	0 Months Ended	12 Months Ended
	Jun. 15, 2011	Dec. 31, 2011	Dec. 31, 2009	Dec. 31, 2010
Business Acquisition [Line Items]
Acquisitions of businesses, net of cash acquired	$ 2,894,400,000	$ 2,894,339,000	$ 768,819,000
Restricted cash	15,500,000
Receivables	113,200,000
Inventories	91,000,000
Net property, plant and equipment, including mineral rights	4,582,600,000
Goodwill	480,300,000
Other assets	35,900,000
Accounts payable	(86,000,000)
Other accrued expenses and current liabilities	(59,100,000)
Debt	(604,800,000)
Litigation accrual	(108,900,000)
Accrued postretirement benefits	(47,700,000)
Asset retirement obligation	(112,700,000)
Coal Supply Agreement Obligation Net		96,998,000		26,041,000
Coal supply agreements, net				(6,036,000)
Deferred income taxes, net	(1,278,900,000)
Other	(35,000,000)
Net tangible and intangible assets acquired	2,894,400,000
ICG [Member]
Business Acquisition [Line Items]
Coal Supply Agreement Obligation Net	$ 91,000,000

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Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2011

Asset Retirement Obligations [Abstract]

Schedule Of Asset Retirement Obligations

	Year Ended December 31
	2011	2010
	(In thousands)
Balance at January 1 (including current portion)	$  343,119	$  310,409
Accretion expense	33,601	26,615
Obligations incurred or acquired	115,019	—
Adjustments to the liability from changes in estimates	11,176	8,934
Liabilities settled	(29,012)	(2,839)
Balance at December 31	$  473,903	$  343,119
Current portion included in accrued expenses	(27,119)	(8,862)
Noncurrent liability	$  446,784	$  334,257

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Property Transactions

12 Months Ended

Dec. 31, 2011

Property Transactions [Abstract]

Property Transactions

2.  Property Transactions

On December 14, 2011, the Company was awarded a federal coal lease for the South Hilight tract in Wyoming for a price of $300.0 million.The bid price will be paid in five equal installments, with the first one made in December 2011.The coal lease will give the Company the right to mine an estimated 222 million tons of coal reserves.The South Hilight tract is contiguous to the Company's Black Thunder mining complex.

On November 12, 2009, the Company entered into a lease of coal reserves and other coal resources from Great Northern Properties Limited Partnership in Montana for $73.1 million. On March 18, 2010, the Company was awarded a Montana state coal lease for the Otter Creek tracts for a price of $85.8 million. These two transactions gave the Company the right to mine approximately 1.4 billion tons of coal reserves in the Montana's Otter Creek area.

The total of the Company's future lease bonus payments due are $23.4 million in 2012, $83.4 million in 2013, $67.3 million in 2014, $60.0 million in 2015 and $60.0 million in 2016.

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Supplemental Condensed Consolidating Financial Information (Schedule Of Condensed Consolidating Balance Sheets) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Assets
Cash and cash equivalents	$ 138,149	$ 93,593	$ 61,138	$ 70,649
Restricted cash	10,322
Receivables	469,179	252,320
Inventories	377,490	235,616
Other	187,634	153,385
Total current assets	1,182,774	734,914
Property, plant and equipment, net	7,949,150	3,308,892
Other	1,082,035	836,963
Total other assets	1,082,035	836,963
Total assets	10,213,959	4,880,769	4,840,596
Liabilities and Stockholders' Equity
Accounts payable	383,782	198,216
Accrued expenses and other current liabilities	356,035	258,133
Current maturities of debt and short-term borrowings	280,851	70,997
Total current liabilities	1,020,668	527,346
Long-term debt	3,762,297	1,538,744
Asset retirement obligations	446,784	334,257
Accrued pension benefits	48,244	49,154
Accrued postretirement benefits other than pension	42,309	37,793
Accrued workers' compensation	71,948	35,290
Deferred income taxes	976,753
Other noncurrent liabilities	255,382	110,234
Total liabilities	6,624,385	2,632,818
Redeemable noncontrolling interest	11,534	10,444
Stockholders' equity	3,578,040	2,237,507	2,115,106	1,728,733
Total liabilities and stockholders' equity	10,213,959	4,880,769
Parent/Issuer [Member]
Assets
Cash and cash equivalents	61,375	13,713	54,255	67,737
Restricted cash	10,322
Receivables	65,187	31,458
Other	81,732	29,575
Total current assets	218,616	74,746
Property, plant and equipment, net	21,241	9,817
Investment in subsidiaries	8,805,731	4,555,233
Intercompany receivables	(1,457,864)	(1,807,902)
Note receivable from Arch Western	225,000	225,000
Other	184,266	481,345
Total other assets	7,757,133	3,453,676
Total assets	7,996,990	3,538,239
Liabilities and Stockholders' Equity
Accounts payable	25,409	10,753
Accrued expenses and other current liabilities	75,133	75,746
Current maturities of debt and short-term borrowings	172,564	14,093
Total current liabilities	273,106	100,592
Long-term debt	3,308,674	1,087,126
Asset retirement obligations	877	873
Accrued pension benefits	19,198	20,843
Accrued postretirement benefits other than pension	13,843	14,284
Accrued workers' compensation	17,272	15,383
Deferred income taxes	621,483
Other noncurrent liabilities	152,963	51,187
Total liabilities	4,407,416	1,290,288
Redeemable noncontrolling interest	11,534	10,444
Stockholders' equity	3,578,040	2,237,507
Total liabilities and stockholders' equity	7,996,990	3,538,239
Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents	332	64	64	61
Receivables	22,037	12,740
Inventories	207,050	85,196
Other	83,122	102,375
Total current assets	312,541	200,375
Property, plant and equipment, net	6,403,658	1,800,578
Intercompany receivables	7,010	508,624
Other	884,613	344,698
Total other assets	891,623	853,322
Total assets	7,607,822	2,854,275
Liabilities and Stockholders' Equity
Accounts payable	175,196	65,793
Accrued expenses and other current liabilities	115,685	31,123
Current maturities of debt and short-term borrowings	1,987
Total current liabilities	292,868	96,916
Long-term debt	2,652
Asset retirement obligations	140,861	32,029
Accrued pension benefits	4,203	4,407
Accrued postretirement benefits other than pension	6,271
Accrued workers' compensation	48,111	13,805
Deferred income taxes	355,270
Other noncurrent liabilities	64,795	22,135
Total liabilities	915,031	169,292
Stockholders' equity	6,692,791	2,684,983
Total liabilities and stockholders' equity	7,607,822	2,854,275
Non-Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents	76,442	79,816	6,819	2,851
Receivables	383,572	210,075
Inventories	170,440	150,420
Other	22,780	21,435
Total current assets	653,234	461,746
Property, plant and equipment, net	1,524,251	1,498,497
Intercompany receivables	1,450,854	1,299,278
Other	13,156	10,920
Total other assets	1,464,010	1,310,198
Total assets	3,641,495	3,270,441
Liabilities and Stockholders' Equity
Accounts payable	183,177	121,670
Accrued expenses and other current liabilities	166,834	153,217
Current maturities of debt and short-term borrowings	106,300	56,904
Total current liabilities	456,311	331,791
Long-term debt	450,971	451,618
Note payable to Arch Coal	225,000	225,000
Asset retirement obligations	305,046	301,355
Accrued pension benefits	24,843	23,904
Accrued postretirement benefits other than pension	22,195	23,509
Accrued workers' compensation	6,565	6,102
Other noncurrent liabilities	37,624	36,912
Total liabilities	1,528,555	1,400,191
Stockholders' equity	2,112,940	1,870,250
Total liabilities and stockholders' equity	3,641,495	3,270,441
Eliminations [Member]
Assets
Receivables	(1,617)	(1,953)
Total current assets	(1,617)	(1,953)
Investment in subsidiaries	(8,805,731)	(4,555,233)
Note receivable from Arch Western	(225,000)	(225,000)
Total other assets	(9,030,731)	(4,780,233)
Total assets	(9,032,348)	(4,782,186)
Liabilities and Stockholders' Equity
Accrued expenses and other current liabilities	(1,617)	(1,953)
Total current liabilities	(1,617)	(1,953)
Note payable to Arch Coal	(225,000)	(225,000)
Total liabilities	(226,617)	(226,953)
Stockholders' equity	(8,805,731)	(4,555,233)
Total liabilities and stockholders' equity	$ (9,032,348)	$ (4,782,186)

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Business Combinations (Summary Of Unaudited Pro Forma) (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Business Combinations [Abstract]
Revenues	$ 1,228,756,000	$ 1,198,673,000	$ 985,528,000	$ 872,938,000	$ 835,394,000	$ 874,705,000	$ 764,295,000	$ 711,874,000	$ 4,285,895,000	$ 3,186,268,000	$ 2,576,081,000
Total revenues pro forma									4,825,600,000	4,299,900,000
Income (loss) before income taxes									135,251,000	177,108,000	25,404,000
Income (loss) before income taxes pro forma									$ 113,500,000	$ (1,200,000)

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Derivative Instruments (Tables)

12 Months Ended

Dec. 31, 2011

Derivative Instruments [Abstract]

Derivative For Risk Management Purposes

	2012	2013	2014	2015
(Tons in thousands)
Coal sales	2,416	1,117	1,440	720
Coal purchases	254	—	—	—

Disclosure Of Fair Value Of Derivatives

Fair Value of Derivatives

(In thousands)

	December 31, 2011								December 31, 2010
	Asset Derivative			Liability Derivative					Asset Derivative			Liability Derivative
Derivatives Designated as Hedging Instruments
Heating oil – diesel purchases	$	8,997		$	—				$	13,475		$	—
Coal	1,109			—					2,009			(2,350		)
Total	10,106			—					15,484			(2,350		)
Derivatives Not Designated as Hedging Instruments
Heating oil  – fuel surcharges	1,797			—					—			—
Coal — held for trading purposes	15,505			(19,927		)			34,445			(24,087		)
Coal	14,855			(6,035		)			1,139			(912		)
Total	32,157			(25,962		)			35,584			(24,999		)
Total derivatives	42,263			(25,962		)			51,068			(27,349		)
Effect of counterparty netting	(18,134		)	18,134					(22,402		)	22,402
Net derivatives as classified in the balance sheets	$	24,129		$	(7,828	)	$	16,301	$	28,666		$	(4,947	)	$	23,719

Net derivatives as reflected on the balance sheets

		December 31, 2011			December 31, 2010
Heating oil	Other current assets	$	10,794		$	13,475
Coal	Coal derivative assets	13,335			15,191
	Coal derivative liabilities	(7,828		)	(4,947		)
		$	16,301		$	23,719

The Company had a current asset for the right to reclaim cash collateral of $12.4 million and $10.3 million at December 31, 2011 and December 31, 2010, respectively. These amounts are not included with the derivatives presented in the table above and are included in "other current assets" in the accompanying consolidated balance sheets.

Effects Of Derivatives On Measures Of Financial Performance

Derivatives used in Fair Value Hedging	Gain on Derivatives Used in						Hedged Items in Fair Value Hedge	Loss on Hedged Items In Fair Value
Relationships	Fair Value Hedge Relationships						Relationships	Hedge Relationships
	2011		2010		2009			2011		2010		2009
	(In thousands)							(In thousands)
Coal	$        —	(3)	$     —	(3)	$      2,586	(3)	Firm commitments	$                      —	(3)	$     —	(3)	$  (2,586)	(3)

Derivatives used inCash Flow Hedging	Gain (Loss) Recognized in OCI (Effective Portion)										Gains (Losses) Reclassified from OCI into Income (Effective Portion)
Relationships	2011			2010			2009			2011				2010			2009
Heating oil – diesel purchases	$	1,294		$	(149	)	$	10,309		$		14,866	(2)	$	437	(2)	$	(49,055	)	(2)
Coal sales	4,923			(4,714		)	(7,441		)	1,572			(1)	(1,602)		(1)	(6,999		)	(1)
Coal purchases	(2,009		)	5,145			1,089			—			(2)	(1,202)		(2)	(13,181		)	(2)
Totals	$	4,208		$	282		$	3,957		$		16,438		$	(2,367	)	$	(69,235)

Derivatives used inCash Flow Hedging	Gain (Loss) Recognized in Income (Ineffective Portion and Amount Excluded from Effectiveness Testing)
Relationships	2011		2010		2009
Heating oil – diesel purchases	$	—	$	—	$                —
Coal sales	—		—		—
Coal purchases	—		—		—
Totals	$	—	$	—	$	—

Derivatives Not Designated as	Gain (Loss)
Hedging Instruments	2011			2010			2009
Coal — unrealized	$	6,438	(3)	$	(10,991)	(3)	$           9,673	(3)
Coal — realized	$	(7)	(4)	$	4,542	(4)	$                 —	(4)
Heating oil — fuel surcharges — unrealized	$	(2,906)	(4)	$	—	(4)	$                 —	(4)

Location in Statement of Income:

(1)Revenues

(2)Cost of sales

(3)Change in fair value of coal derivatives and coal trading activities, net

(4)Other operating income, net

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Guarantees and Commitments

12 Months Ended

Dec. 31, 2011

Guarantees [Abstract]

Guarantees and Commitments

22.  Guarantees and Commitments

The Company has agreed to continue to provide surety bonds and letters of credit for the reclamation and retiree healthcare obligations of Magnum Coal Company ("Magnum") related to the properties the Company sold to Magnum on December 31, 2005. Patriot Coal Corporation ("Patriot") acquired Magnum in July 2008. The purchase agreement requires Magnum to reimburse the Company for costs related to the surety bonds and letters of credit and to use commercially reasonable efforts to replace the obligations. If the surety bonds and letters of credit related to the reclamation obligations are not replaced by Magnum within a specified period of time, Magnum must post a letter of credit in favor of the Company in the amounts of the reclamation obligations. As of December 31, 2011, Patriot had replaced $48.9 million of the surety bonds and posted letters of credit of $16.1 million in the Company's favor. At December 31, 2011, the Company had $38.5 million of surety bonds remaining related to properties sold to Magnum. The surety bonding amounts are mandated by the state and are not directly related to the estimated cost to reclaim the properties.

Magnum also acquired certain coal supply contracts with customers who did not consent to the assignment of the contract from the Company to Magnum. The Company has committed to purchase coal from Magnum to fulfill these contracts at the same price it is charging the customers for the sale. In addition, certain contracts were assigned to Magnum, but the Company has guaranteed Magnum's performance under the contracts. The longest of the coal supply contracts extends to the year 2017. If Magnum is unable to supply the coal for these coal sales contracts then the Company would be required to purchase coal on the open market or supply contracts from its existing operations. At market prices effective at December 31, 2011, the cost of purchasing 9.8 million tons of coal to supply over their duration the contracts that were not assigned would exceed the sales price under the contracts by approximately $199.4 million, and the cost of purchasing 0.7 million tons of coal to supply over their duration the assigned and guaranteed contracts would exceed the sales price under the contracts by approximately $15.3 million. As the Company does not believe that it is probable that it would have to purchase replacement coal, no losses have been recorded in the consolidated financial statements as of December 31, 2011. However, if the Company would have to perform under these guarantees, it could potentially have a material adverse effect on the business, results of operations and financial condition of the Company.

In connection with the Company's acquisition of the coal operations of ARCO and the simultaneous combination of the acquired ARCO operations and the Company's Wyoming operations into the Arch Western joint venture, the Company agreed to indemnify the other member of Arch Western against certain tax liabilities in the event that such liabilities arise prior to June 1, 2013 as a result of certain actions taken, including the sale or other disposition of certain properties of Arch Western, the repurchase of certain equity interests in Arch Western by Arch Western or the reduction under certain circumstances of indebtedness incurred by Arch Western in connection with the acquisition. If the Company were to become liable, the maximum amount of potential future tax payments was $19.3 million at December 31, 2011, which is not recorded as a liability in the Company's consolidated financial statements. Since the indemnification is dependent upon the initiation of activities within the Company's control and the Company does not intend to initiate such activities, it is remote that the Company will become liable for any obligation related to this indemnification. However, if such indemnification obligation were to arise, it could potentially have a material adverse effect on the business, results of operations and financial condition of the Company.

The Company has unconditional purchase obligations relating to purchases of coal, materials and supplies and capital commitments, other than reserve acquisitions, and is also a party to transportation capacity commitments. The future commitments under these agreements total $487.5 million in 2012, $139.2 million in 2013, $175.0 million in 2014, $163.9 million in 2015, $128.3 million in 2016 and $154.8 million thereafter. These commitments include the cost of coal purchases from Magnum as discussed above. During the years ended December 31, 2011, 2010 and 2009, the Company fulfilled its commitments under agreements containing unconditional obligations.

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Leases

12 Months Ended

Dec. 31, 2011

Leases [Abstract]

Leases

21.  Leases

The Company leases equipment, land and various other properties under non-cancelable long-term leases, expiring at various dates. Certain leases contain options that would allow the Company to extend the lease or purchase the leased asset at the end of the base lease term. In addition, the Company enters into various non-cancelable royalty lease agreements under which future minimum payments are due.

Minimum payments due in future years under these agreements in effect at December 31, 2011 are as follows:

	Operating      Leases	Royalties
	(In thousands)
2012	$    28,903	$    24,378
2013	27,610	25,595
2014	25,119	25,810
2015	17,641	27,565
2016	9,648	24,397
Thereafter	12,640	114,371
	$  121,561	$  242,116

Rental expense, including amounts related to these operating leases and other shorter-term arrangements, amounted to $43.9 million in 2011, $41.6 million in 2010 and $43.3 million in 2009.

Royalties are paid to lessors either as a fixed price per ton or as a percentage of the gross sales price of the mined coal. Royalties under the majority of the Company's significant leases are paid on a percentage royalty basis. Royalty expense, including production royalties, was $349.0 million in 2011, $286.8 million in 2010 and $230.5 million in 2009.

As of December 31, 2011, certain of the Company's lease obligations were secured by outstanding surety bonds totaling $64.6 million.

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Employee Benefit Plans (Summary Of Estimated Future Benefit Payments) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
2012	$ 17,898
2013	20,854
2014	22,803
2015	22,492
2016	26,185
Years 2017-2021	164,788
Defined benefit plan expected future benefit payments total	275,020
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
2012	3,411
2013	3,787
2014	4,060
2015	4,406
2016	4,694
Years 2017-2021	25,122
Defined benefit plan expected future benefit payments total	$ 45,480

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Supplemental Condensed Consolidating Financial Information (Tables)

12 Months Ended

Dec. 31, 2011

Supplemental Condensed Consolidating Financial Information [Abstract]

Schedule Of Condensed Consolidating Statements Of Income

CONDENSED CONSOLIDATING STATEMENTS OF INCOME

Year Ended December 31, 2011

Parent/Issuer	Guarantor   Subsidiaries	Non-Guarantor   Subsidiaries	Eliminations	Consolidated
(In thousands)

Revenues	$                  –	$2,024,168	$  2,261,727	$               –	$   4,285,895
Costs, expenses and other
Cost of sales	22,925	1,537,697	1,812,461	(105,173)	3,267,910
Depreciation, depletion and amortization	2,883	304,742	158,962	–	466,587
Amortization of acquired sales contracts, net	–	(41,527)	19,458	–	(22,069)
Selling, general and administrative expenses	74,591	13,860	37,839	(7,234)	119,056
Change in fair value of coal derivatives and coal trading activities, net	–	(2,907)	–	–	(2,907)
Acquisition and transition costs	54,676	–	–	–	54,676
Other operating (income) expense, net	(23,306)	(118,767)	18,732	112,407	(10,934)
	131,769	1,693,098	2,047,452	-	3,872,319
Income from investment in subsidiaries	556,448	–	–	(556,448)	–
Income from operations	424,679	331,070	214,275	(556,448)	413,576
Interest income (expense), net:
Interest expense	(256,220)	(5,062)	(43,728)	74,824	(230,186)
Interest income	16,282	759	61,092	(74,824)	3,309
	(239,938)	(4,303)	17,364	–	(226,877)
Other non-operating expense
Bridge financing costs related to ICG	(49,490)	-	-	-	(49,490)
Net loss resulting from early retirement of debt	–	(1,958)	-	–	(1,958)
	(49,490)	(1,958)	-	–	(51,448)
Income before income taxes	135,251	324,809	231,639	(556,448)	135,251
Benefit from income taxes	(7,589)	–	–	–	(7,589)
Net income	142,840	324,809	231,639	(556,448)	142,840
Less:  Net income attributable to noncontrolling interest	(1,157)	–	–	–	(1,157)
Net income attributable to Arch Coal	$  141,683	$  324,809	$   231,639	$(556,448)	$141,683

CONDENSED CONSOLIDATING STATEMENTS OF INCOME

Year Ended December 31, 2010

	Parent/Issuer	Guarantor    Subsidiaries	Non-Guarantor    Subsidiaries	Eliminations	Consolidated
	(In thousands)
Revenues	$               —	$  1,137,980	$     2,048,288	$               —	$  3,186,268
Costs, expenses and other
Cost of sales	11,526	797,917	1,679,872	(93,503)	2,395,812
Depreciation, depletion and amortization	2,933	194,847	167,286	—	365,066
Amortization of acquired sales contracts, net	—	—	35,606	—	35,606
Selling, general and administrative expenses	79,580	7,355	38,496	(7,254)	118,177
Change in fair value of coal derivatives and coal trading activities, net	—	8,924	—	—	8,924
Gain on Knight Hawk transaction	—	(41,577)	—	—	(41,577)
Other operating (income) expense, net	(10,259)	(115,994)	5,772	100,757	(19,724)
	83,780	851,472	1,927,032	—	2,862,284
Income from investment in subsidiaries	393,366	—	—	(393,366)	—
Income from operations	309,586	286,508	121,256	(393,366)	323,984
Interest expense, net:
Interest expense	(143,606)	(2,763)	(64,463)	68,283	(142,549)
Interest income	11,128	456	59,148	(68,283)	2,449
	(132,478)	(2,307)	(5,315)	—	(140,100)
Other non-operating expense
Net loss resulting from early retirement of debt	—	—	(6,776)	—	(6,776)
	—	—	(6,776)	—	(6,776)
Income before income taxes	177,108	284,201	109,165	(393,366)	177,108
Provision for income taxes	17,714	—	—	—	17,714
Net income	159,394	284,201	109,165	(393,366)	159,394
Less: Net income attributable to noncontrolling interest	(537)	—	—	—	(537)
Net income attributable to Arch Coal	$    158,857	$      284,201	$        109,165	$   (393,366)	$      158,857

CONDENSED CONSOLIDATING STATEMENTS OF INCOME

Year Ended December 31, 2009

	Parent/Issuer	Guarantor Subsidiaries	Non-Guarantor    Subsidiaries	Eliminations	Consolidated
	(In thousands)
Revenues	$             —	$  924,692	$     1,651,389	$               —	$  2,576,081
Costs, expenses and other
Cost of sales	7,481	713,782	1,398,663	(49,211)	2,070,715
Depreciation, depletion and amortization	3,678	138,125	159,805	—	301,608
Amortization of acquired sales contracts, net	—	—	19,623	—	19,623
Selling, general and administrative expenses	49,672	7,504	46,563	(5,952)	97,787
Change in fair value of coal derivatives and coal trading activities, net	—	(12,056)	—	—	(12,056)
Acquisition and transition costs	13,726	—	—	—	13,726
Other operating (income) expense, net	(12,909)	(85,460)	4,170	55,163	(39,036)
	61,648	761,895	1,628,824	—	2,452,367
Income from investment in subsidiaries	165,183	—	—	(165,183)	—
Income from operations	103,535	162,797	22,565	(165,183)	123,714
Interest expense, net:
Interest expense	(92,371)	(2,442)	(70,668)	59,549	(105,932)
Interest income	14,240	720	52,211	(59,549)	7,622
	(78,131)	(1,722)	(18,457)	—	(98,310)
Income before income taxes	25,404	161,075	4,108	(165,183)	25,404
Benefit from income taxes	(16,775)	—	—	—	(16,775)
Net income	42,179	161,075	4,108	(165,183)	42,179
Less: Net income attributable to noncontrolling interest	(10)	—	—	—	(10)
Net income attributable to Arch Coal	$     42,169	$  161,075	$             4,108	$   (165,183)	$        42,169

Schedule Of Condensed Consolidating Balance Sheets

CONDENSED CONSOLIDATING BALANCE SHEETS

December 31, 2011

	Parent/Issuer	Guarantor  Subsidiaries	Non-Guarantor   Subsidiaries	Eliminations	Consolidated
	(In thousands)
ASSETS
Cash and cash equivalents	$  61,375	$    332	$     76,442	$         –	$  138,149
Restricted cash	10,322	–	–	–	10,322
Receivables	65,187	22,037	383,572	(1,617)	469,179
Inventories	–	207,050	170,440	–	377,490
Other	81,732	83,122	22,780	–	187,634
Total current assets	218,616	312,541	653,234	(1,617)	1,182,774
Property, plant and equipment, net	21,241	6,403,658	1,524,251	–	7,949,150
Investment in subsidiaries	8,805,731	–	–	(8,805,731)	–
Intercompany receivables	(1,457,864)	7,010	1,450,854	–	–
Note receivable from Arch Western	225,000	–	–	(225,000)	–
Other	184,266	884,613	13,156	–	1,082,035
Total other assets	7,757,133	891,623	1,464,010	(9,030,731)	1,082,035
Total assets	$  7,996,990	$7,607,822	$  3,641,495	(9,032,348)	$10,213,959
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable	$   25,409	$ 175,196	$ 183,177	$    –	$  383,782
Accrued expenses and other current liabilities	75,133	115,685	166,834	(1,617)	356,035
Current maturities of debt and short-term borrowings	172,564	1,987	106,300	–	280,851
Total current liabilities	273,106	292,868	456,311	(1,617)	1,020,668
Long-term debt	3,308,674	2,652	450,971		3,762,297
Note payable to Arch Coal	–	–	225,000	(225,000)	–
Asset retirement obligations	877	140,861	305,046	–	446,784
Accrued pension benefits	19,198	4,203	24,843	–	48,244
Accrued postretirement benefits other than pension	13,843	6,271	22,195	–	42,309
Accrued workers' compensation	17,272	48,111	6,565	–	71,948
Deferred income taxes	621,483	355,270	–	–	976,753
Other noncurrent liabilities	152,963	64,795	37,624	–	255,382
Total liabilities	4,407,416	915,031	1,528,555	(226,617)	6,624,385
Redeemable noncontrolling interest	11,534	–	–	–	11,534
Stockholders' equity	3,578,040	6,692,791	2,112,940	(8,805,731)	3,578,040
Total liabilities and stockholders' equity	$  7,996,990	$7,607,822	$ 3,641,495	$ (9,032,348)	$10,213,959

CONDENSED CONSOLIDATING BALANCE SHEETS

December 31, 2010

	Parent/Issuer	Guarantor   Subsidiaries	Non-Guarantor    Subsidiaries	Eliminations	Consolidated
	(In thousands)
ASSETS
Cash and cash equivalents	$          13,713	$                64	$        79,816	$                  —	$        93,593
Receivables	31,458	12,740	210,075	(1,953)	252,320
Inventories	—	85,196	150,420	—	235,616
Other	29,575	102,375	21,435	—	153,385
Total current assets	74,746	200,375	461,746	(1,953)	734,914
Property, plant and equipment, net	9,817	1,800,578	1,498,497	—	3,308,892
Investment in subsidiaries	4,555,233	—	—	(4,555,233)	—
Intercompany receivables	(1,807,902)	508,624	1,299,278	—	—
Note receivable from Arch Western	225,000	—	—	(225,000)	—
Other	481,345	344,698	10,920	—	836,963
Total other assets	3,453,676	853,322	1,310,198	(4,780,233)	836,963
Total assets	$    3,538,239	$  2,854,275	$  3,270,441	$   (4,782,186)	$  4,880,769
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable	$          10,753	$        65,793	$      121,670	$                  —	$     198,216
Accrued expenses and other current liabilities	75,746	31,123	153,217	(1,953)	258,133
Current maturities of debt and short-term borrowings	14,093	—	56,904	—	70,997
Total current liabilities	100,592	96,916	331,791	(1,953)	527,346
Long-term debt	1,087,126	—	451,618	—	1,538,744
Note payable to Arch Coal	—	—	225,000	(225,000)	—
Asset retirement obligations	873	32,029	301,355	—	334,257
Accrued pension benefits	20,843	4,407	23,904	—	49,154
Accrued postretirement benefits other than pension	14,284	—	23,509	—	37,793
Accrued workers' compensation	15,383	13,805	6,102	—	35,290
Other noncurrent liabilities	51,187	22,135	36,912	—	110,234
Total liabilities	1,290,288	169,292	1,400,191	(226,953)	2,632,818
Redeemable noncontrolling interest	10,444	—	—	—	10,444
Stockholders' equity	2,237,507	2,684,983	1,870,250	(4,555,233)	2,237,507
Total liabilities and stockholders' equity	$    3,538,239	$  2,854,275	$  3,270,441	$   (4,782,186)	$  4,880,769

Schedule Of Condensed Consolidating Statements Of Cash Flows

CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS

Year Ended December 31, 2011

	Parent/Issuer	Guarantor   Subsidiaries	Non-Guarantor   Subsidiaries	Eliminations	Consolidated
		(In thousands)
Cash provided by (used in) operating activities	$ (561,704)	$801,201	$ 402,745	$          –	$ 642,242
Investing Activities
Acquisitions of businesses, net of cash acquired	(2,894,339)	–	–	–	(2,894,339)
Decrease in restricted cash	5,167	–	–	–	5,167
Capital expenditures	(12,809)	(353,441)	(174,686)	–	(540,936)
Proceeds from dispositions of property, plant and equipment	–	25,730	157	–	25,887
Additions to prepaid royalties	-	(25,982)	(3,975)	-	(29,957)
Purchases of investments and advances to affiliates	(633,534)	(33,553)	-	605,178	(61,909)
Consideration paid related to prior business acquisitions	(829)	–	–	–	(829)
Cash used in investing activities	(3,536,344)	(387,246)	(178,504)	605,178	(3,496,916)
Financing Activities
Proceeds from the issuance of senior notes	2,000,000	–	–	–	2,000,000
Proceeds from the issuance of common stock, net	1,267,933	–	–	–	1,267,933
Contributions from parent	–	605,178	–	(605,178)	–
Payments to retire debt	–	(605,178)	–	–	(605,178)
Net increase (decrease) in borrowings under lines of credit and commercial paper program	481,300	–	(56,904)	–	424,396
Net proceeds from other debt	5,334	–	–	–	5,334
Debt financing costs	(114,799)	–	(24)	–	(114,823)
Dividends paid	(80,748)	–	–	–	(80,748)
Issuance of common stock under incentive plans	2,316	–	–	–	2,316
Transactions with affiliates, net	584,374	(413,687)	(170,687)	–	–
Cash provided by (used in) financing activities	4,145,710	(413,687)	(227,615)	(605,178)	2,899,230
Increase (decrease) in cash and cash equivalents	47,662	268	(3,374)	–	44,556
Cash and cash equivalents, beginning of period	13,713	64	79,816	–	93,593
Cash and cash equivalents, end of period	$  61,375	$   332	$   76,442	$               –	$   138,149

CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS

Year Ended December 31, 2010

	Parent/Issuer	Guarantor  Subsidiaries	Non-Guarantor   Subsidiaries	Consolidated
	(In thousands)
Cash provided by (used in) operating activities	$   (238,736)	$    503,766	$    432,117	$    697,147
Investing Activities
Capital expenditures	(4,814)	(198,243)	(111,600)	(314,657)
Proceeds from dispositions of property, plant and equipment	—	251	79	330
Additions to prepaid royalties	—	(24,381)	(2,974)	(27,355)
Purchases of investments and advances to affiliates	(40,421)	(5,764)	—	(46,185)
Consideration paid related to prior business acquisitions	(1,262)	—	—	(1,262)
Cash used in investing activities	(46,497)	(228,137)	(114,495)	(389,129)
Financing Activities
Proceeds from the issuance of senior notes	500,000	—	—	500,000
Payments to retire debt	—	—	(505,627)	(505,627)
Net decrease in borrowings under lines of credit and commercial paper program	(120,000)	—	(76,549)	(196,549)
Net proceeds from other debt	82	—	—	82
Debt financing costs	(12,022)	—	(729)	(12,751)
Dividends paid	(63,373)	—	—	(63,373)
Issuance of common stock under incentive plans	1,764			1,764
Contribution from noncontrolling interest	—	—	891	891
Transactions with affiliates, net	(61,760)	(275,629)	337,389	—
Cash provided by (used in) financing activities	244,691	(275,629)	(244,625)	(275,563)
Increase (decrease) in cash and cash equivalents	(40,542)	—	72,997	32,455
Cash and cash equivalents, beginning of period	54,255	64	6,819	61,138
Cash and cash equivalents, end of period	$      13,713	$              64	$      79,816	$      93,593

CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS

Year Ended December 31, 2009

	Parent/Issuer	Guarantor   Subsidiaries	Non-Guarantor    Subsidiaries	Consolidated
	(In thousands)
Cash provided by (used in) operating activities	$   (168,427)	$    338,956	$    212,451	$       382,980
Investing Activities
Acquisitions of businesses, net of cash acquired	(768,819)	—	—	(768,819)
Capital expendiutres	(2,940)	(194,756)	(125,454)	(323,150)
Proceeds from dispositions of property, plant and equipment	—	734	91	825
Additions to prepaid royalties	—	(23,991)	(2,764)	(26,755)
Purchases of investments and advances to affiliates	(8,000)	(2,925)	—	(10,925)
Consideration paid related to prior business acquisitions	(4,767)	—	—	(4,767)
Reimbursement of deposits on equipment	—	—	3,209	3,209
Cash used in investing activities	(784,526)	(220,938)	(124,918)	(1,130,382)
Financing Activities
Proceeds from the issuance of senior notes	584,784	—	—	584,784
Proceeds from the sale of common stock, net	326,452	—	—	326,452
Net decrease in borrowings under lines of credit and commercial paper program	(85,000)	—	(815)	(85,815)
Net payments on other debt	(2,986)	—	—	(2,986)
Debt financing costs	(29,456)	—	(203)	(29,659)
Dividends paid	(54,969)	—	—	(54,969)
Issuance of common stock under incentive plans	84	—	—	84
Transactions with affiliates, net	200,562	(118,015)	(82,547)	—
Cash provided by (used in) financing activities	939,471	(118,015)	(83,565)	737,891
Increase (decrease) in cash and cash equivalents	(13,482)	3	3,968	(9,511)
Cash and cash equivalents, beginning of period	67,737	61	2,851	70,649
Cash and cash equivalents, end of period	$      54,255	$              64	$        6,819	$          61,138

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Accrued Expenses And Other Current Liabilities (Tables)

12 Months Ended

Dec. 31, 2011

Accrued Expenses And Other Current Liabilities [Abstract]

Accrued Expenses and Other Current Liabilities

		December 31
	2011		2010
		(In thousands)
Payroll and employee benefits	$	65,323	$	51,327
Taxes other than income taxes		133,331		107,969
Interest		55,266		52,843
Acquired sales contracts (see Note 6)		38,441		5,615
Workers' compensation (see Note 15)		11,666		6,659
Asset retirement obligations (see Note 14)		27,119		8,862
Other		17,061		12,136
	$	348,207	$	245,411

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Contingencies

12 Months Ended

Dec. 31, 2011

Contingencies [Abstract]

Contingencies

23.  Contingencies

The following matters relate to certain claims and legal actions involving ICG and/or its subsidiaries.

Allegheny Energy Supply ("Allegheny"), the sole customer of coal produced at the Company's subsidiary Wolf Run Mining Company's ("Wolf Run") Sycamore No. 2 mine, filed a lawsuit against Wolf Run, Hunter Ridge Holdings, Inc. ("Hunter Ridge"), and ICG in state court in Allegheny County, Pennsylvania on December 28, 2006, and amended its complaint on April 23, 2007. Allegheny claimed that Wolf Run breached a coal supply contract when it declared force majeure under the contract upon idling the Sycamore No. 2 mine in the third quarter of 2006, and that Wolf Run continued to breach the contract by failing to ship in volumes referenced in the contract. The Sycamore No. 2 mine was idled after encountering adverse geologic conditions and abandoned gas wells that were previously unidentified and unmapped. After extensive searching for gas wells and rehabilitation of the mine, it was re-opened in 2007, but with notice to Allegheny that it would necessarily operate at reduced volumes in order to safely and effectively avoid the many gas wells within the reserve. The amended complaint also alleged that the production stoppages constitute a breach of the guarantee agreement by Hunter Ridge and breach of certain representations made upon entering into the contract in early 2005. Allegheny voluntarily dropped the breach of representation claims later. Allegheny claimed that it would incur costs in excess of $100 million to purchase replacement coal over the life of the contract. ICG, Wolf Run and Hunter Ridge answered the amended complaint on August 13, 2007, disputing all of the remaining claims.

On November 3, 2008, ICG, Wolf Run and Hunter Ridge filed an amended answer and counterclaim against the plaintiffs seeking to void the coal supply agreement due to, among other things, fraudulent inducement and conspiracy. On September 23, 2009, Allegheny filed a second amended complaint alleging several alternative theories of liability in its effort to extend contractual liability to ICG, which was not a party to the original contract and did not exist at the time Wolf Run and Allegheny entered into the contract. No new substantive claims were asserted. ICG answered the second amended complaint on October 13, 2009, denying all of the new claims. ICG's counterclaim was dismissed on motion for summary judgment entered on May 11, 2010. Allegheny's claimsagainst ICG were also dismissed by summary judgment, but the claims against Wolf Run and Hunter Ridge were not. The court conducted a non-jury trial of this matter beginning on January 10, 2011 and concluding on February 1, 2011. At the trial, Allegheny presented its evidence for breach of contract and claimed that it is entitled to past and future damages in the aggregate of between $228.0 million and $377.0 million. Wolf Run and Hunter Ridge presented their defense of the claims, including evidence with respect to the existence of force majeure conditions and excuse under the contract and applicable law. Wolf Run and Hunter Ridge presented evidence that Allegheny's damages calculations were significantly inflated because it did not seek to determine damages as of the time of the breach and in some instances artificially assumed future non-delivery or did not take into account the apparent requirement to supply coal in the future. On May 2, 2011, the trial court entered a Memorandum and Verdict determining that Wolf Run had breached the coal supply contract and that the performance shortfall was not excused by force majeure. ICG and Allegheny filed post-verdict motions in the trial court and on August 23, 2011, the court denied the parties' motions. The court entered a final judgment on August 25, 2011, in the amount of $104.1 million, which included pre-judgment interest. The parties appealed the lower court's decision to the Superior Court of Pennsylvania. Wolf Run and Hunter Ridge have filed an appeal bond in the amount of $124.9 million. Briefing is scheduled to begin on October 24, 2011, to be completed in early 2012.

As of December 31, 2011, the Company has accrued $108.3 million for this lawsuit, including $3.4 million of interest recognized post-acquisition. The ultimate resolution of this matter could result in an outcome which may be materially different than what the Company has accrued.

In addition, the Company is a party to numerous claims and lawsuits with respect to various matters. The Company provides for costs related to contingencies when a loss is probable and the amount is reasonably determinable. After conferring with counsel, it is the opinion of management that the ultimate resolution of pending claims, other than as noted above, will not have a material adverse effect on the consolidated financial condition, results of operations or liquidity of the Company.

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Segment Information

12 Months Ended

Dec. 31, 2011

Segment Information [Abstract]

Segment Information

24.  Segment Information

The Company has three reportable business segments, which are based on the major coal producing basins in which the Company operates. Each of these reportable business segments includes a number of mine complexes. The Company manages its coal sales by coal basin, not by individual mine complex. Geology, coal transportation routes to customers, regulatory environments and coal quality are characteristic to a basin. Accordingly, market and contract pricing have developed by coal basin. Mine operations are evaluated based on their per-ton operating costs (defined as including all mining costs but excluding pass-through transportation expenses), as well as on other non-financial measures, such as safety and environmental performance. The Company's reportable segments are the Powder River Basin (PRB) segment, with operations in Wyoming; the Western Bituminous (WBIT) segment, with operations in Utah, Colorado and southern Wyoming; the Appalachia (APP) segment, with operations in West Virginia, Kentucky, Maryland and Virginia. The Appalachia segment includes the acquired ICG operations in Appalachia, as well as the Company's previous Central Appalachia segment. The "Other" operating segment represents primarily the Company's Illinois operations and ADDCAR subsidiary, which manufactures and sells its patented highwall mining system.

Operating segment results for the years ended December 31, 2011, 2010 and 2009 are presented below. Results for the reportable segments include all direct costs of mining, including all depreciation, depletion and amortization related to the mining operations, even if the assets are not recorded at the operating segment level. See discussion of segment assets below. Corporate, Other and Eliminations includes the change in fair value of coal derivatives and coal trading activities, net; corporate overhead; land management; other support functions; and the elimination of intercompany transactions.

The asset amounts below represent an allocation of assets used in the segments' cash-generating activities. The amounts in Corporate, Other and Eliminations represent primarily corporate assets (cash, receivables, investments, plant, property and equipment) as well as unassigned coal reserves, above-market acquired sales contracts and other unassigned assets.

	PRB	APP	WBIT		Other Operating Segments		Corporate, Other and Eliminations		Consolidated
	(In thousands)
December 31, 2011
Revenues	$  1,646,947	$  1,915,090		$  672,766		$   51,092		$                —		$  4,285,895
Income (loss) from operations	180,730	283,404		119,665		(4,685)		(165,538)		413,576
Total assets	2,307,783	4,740,723		681,393		581,040		1,903,020		10,213,959
Depreciation, depletion and amortization	171,693	203,759		81,235		7,876		2,024		466,587
Amortization of acquired sales contracts, net	19,458	(39,988)		—		(1,539)		—		(22,069)
Capital expenditures	110,999	217,435		66,356		28,243		117,903		540,936
December 31, 2010
Revenues	$  1,606,236	$  1,042,490		$  537,542		$                —		$               —		$  3,186,268
Income from operations	146,555	193,943		58,082		—		(74,596)		323,984
Total assets	2,295,786	706,624		677,611		—		1,200,748		4,880,769
Depreciation, depletion and amortization	185,218	97,764		80,497		—		1,587		365,066
Amortization of acquired sales contracts, net	35,606	—		—		—		—		35,606
Capital expenditures	38,142	70,839		65,470		—		140,206		314,657
December 31, 2009
Revenues	$  1,205,492	$      829,895		$  540,694		$                —		$                —		$  2,576,081
Income from operations	82,341	105,241		29,722		—		(93,590)		123,714
Total assets	2,421,917	734,309		687,873		—		996,497		4,840,596
Depreciation, depletion and amortization	127,378	88,409		83,781		—		2,040		301,608
Amortization of acquired sales contracts, net	19,934	—		(311)		—		—		19,623
Capital expenditures	58,275	48,673		67,299		—		148,903		323,150

A reconciliation of segment income from operations to consolidated income before income taxes follows:

	Year Ended December 31
	2011	2010	2009
	(In thousands)
Income from operations	$    413,576	$    323,984	$  123,714
Interest expense	(230,186)	(142,549)	(105,932)
Interest income	3,309	2,449	7,622
Bridge financing costs related to ICG	(49,490)	—	—
Loss on early extinguishment of debt	(1,958)	(6,776)	—
Income before income taxes	$      135,251	$      177,108	$     25,404

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Accounting Policies

12 Months Ended

Dec. 31, 2011

Accounting Policies [Abstract]

Accounting Policies

1.  Accounting Policies

Basis of Presentation

The consolidated financial statements include the accounts of Arch Coal, Inc. and its subsidiaries and controlled entities ("the Company"). The Company produces coal from surface and underground mines located throughout the United States for sale to domestic and international customers as steam coal to power plants and industrial facilities and metallurgical coal used in steel production. The Company expanded further into metallurgical coal markets with the acquisition of International Coal Group, Inc. ("ICG") on June 15, 2011, as described in Note 3, "Business Combinations." The Company operates 23 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 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.

 Accounting Pronouncements

There were no accounting pronouncements whose adoption had, or is expected to have, a material impact on the Company's consolidated financial statements.

  

Accounting Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and revenues and expenses in the accompanying consolidated financial statements and the disclosure of contingent assets and liabilities. Actual results could differ from those estimates.

Cash and Cash Equivalents

Cash and cash equivalents are stated at cost. Cash equivalents consist of highly-liquid investments with an original maturity of three months or less when purchased. At December 31, 2011 and 2010, the carrying amounts of cash and cash equivalents approximate their fair value.

Allowance for Uncollectible Receivables

The Company establishes an allowance for uncollectible receivables for the amounts of trade accounts receivable and other receivables that are not expected to be collected, based on past collection history, the economic environment and specified risks identified in the receivables portfolio. Receivables are considered past due if the full payment is not received by the contractual due date. At December 31, 2011 and 2010, there was either no allowance or an insignificant allowance for uncollectible receivables.

Inventories

Coal and supplies inventories are valued at the lower of average cost or market. Coal inventory costs include labor, supplies, equipment costs, transportation costs incurred prior to the transfer of title to customers and operating overhead. The costs of removing overburden, called stripping costs, incurred during the production phase of the mine are considered variable production costs and are included in the cost of the coal extracted during the period the stripping costs are incurred.

Investments and Membership Interests in Joint Ventures

Investments and membership interests in joint ventures are accounted for under the equity method of accounting if the Company has the ability to exercise significant influence, but not control, over the entity. The Company's share of the entity's income is reflected in other operating income, net in the consolidated statements of income. Information about investment activity is provided in Note 8, "Equity Investments and Membership Interests in Joint Ventures."

Marketable equity securities held by the Company that do not qualify for equity method accounting are classified as available-for-sale and are recorded at their fair value on the balance sheet. Unrealized gains and losses on these investments are recorded in other comprehensive income. A decline in the value of an investment that is considered other-than-temporary is recognized in income.

Prepaid Royalties

Leased mineral rights are often acquired through royalty payments. When royalty payments represent prepayments recoupable against future production, they are recorded as a prepaid asset, with amounts expected to be recouped within one year classified as current. When the coal is mined under these leases the royalties are recouped and the prepayment is charged to cost of sales.

Acquired Sales Contracts

Coal supply agreements (sales contracts) acquired in a business combination are capitalized at their fair value and amortized over the tons of coal shipped during the term of the contract. The fair value of a sales contract is determined by discounting the cash flows attributable to the difference between the contract price and the prevailing forward prices for the tons under contract at the date of acquisition. See Note 6, "Acquired Sales Contracts" for further information related to the Company's acquired sales contracts.

Exploration Costs

Costs to acquire permits for exploration activities are capitalized. Drilling and other costs related to locating coal deposits and evaluating the economic viability of such deposits are expensed as incurred.

 

Property, Plant and Equipment

Plant and Equipment

Plant and equipment are recorded at cost. Interest costs incurred during the construction period for major asset additions are capitalized. Expenditures that extend the useful lives of existing plant and equipment or increase the productivity of the asset are capitalized. The cost of maintenance and repairs that do not extend the useful life or increase the productivity of the asset are expensed as incurred.

Preparation plants and loadouts are depreciated using the units-of-production method over the estimated recoverable reserves, subject to a minimum level of depreciation. Other plant and equipment are depreciated principally using the straight-line method over the estimated useful lives of the assets, limited by the remaining life of the mine. The useful lives of mining equipment, including longwalls, draglines and shovels, range from 5 to 32 years. The useful lives of buildings and leasehold improvements generally range from 10 to 30 years.

Deferred Mine Development

Costs of developing new mines or significantly expanding the capacity of existing mines are capitalized and amortized using the units-of-production method over the estimated recoverable reserves that are associated with the property being benefited. Costs may include construction permits and licenses; mine design; construction of access roads, shafts, slopes and main entries; and removing overburden to access reserves in a new pit. Additionally, deferred mine development includes the asset cost associated with asset retirement obligations.

Coal Lands and Mineral Rights

Rights to coal reserves may be acquired directly through governmental or private entities. A significant portion of the Company's coal reserves are controlled through leasing arrangements. The net book value of the Company's leased coal interests was $1.6 billion at December 31, 2011 and 2010. Payments to acquire royalty lease agreements and lease bonus payments are capitalized as a cost of the underlying mineral reserves and depleted over the life of proven and probable reserves. Coal lease rights are depleted using the units-of-production method, and the rights are assumed to have no residual value. Lease agreements are generally long-term in nature (original terms range from 10 to 50 years), and substantially all of the leases contain provisions that allow for automatic extension of the lease term providing certain requirements are met. See Note 2, "Property Transactions" for further disclosures on coal lease agreements.

Impairment

      If facts and circumstances suggest that the carrying value of a long-lived asset or asset group may not be recoverable, the asset or asset group is reviewed for potential impairment. If this review indicates that the carrying amount of the asset will not be recoverable through projected undiscounted cash flows generated by the asset and its related asset group over its remaining life, then an impairment loss is recognized by reducing the carrying value of the asset to its fair value. The Company may, under certain circumstances, idle mining operations in response to market conditions or other factors. Because an idling is not a permanent closure, it is not considered an automatic indicator of impairment.

 Goodwill

In a business combination, goodwill represents the excess of the purchase price over the fair value assigned to the net tangible and identifiable intangible assets acquired. The Company tests goodwill for impairment annually as of the beginning of the fourth quarter, or when circumstances indicate a possible impairment may exist. If the results of the testing indicate that the carrying amount of a reporting unit exceeds the fair value of the reporting unit, the fair value of goodwill must be calculated. An impairment loss generally would be recognized when the carrying amount of goodwill exceeds the implied fair value of goodwill, determined by subtracting the fair value of the other assets and liabilities associated with the reporting unit from the total fair value of the reporting unit. The fair value of a reporting unit is determined using a discounted cash flow ("DCF") technique. A number of significant assumptions and estimates are involved in the application of the DCF analysis to forecast operating cash flows, including the discount rate and projections of selling prices and costs to produce.

  

Deferred Financing Costs

The Company capitalizes costs incurred in connection with new borrowings, the establishment or enhancement of credit facilities and the issuance of debt securities. These costs are amortized as an adjustment to interest expense over the life of the borrowing or term of the credit facility using the interest method. The unamortized balance of deferred financing costs was $90.5 million and $37.6 million at December 31, 2011 and 2010, respectively. Amounts classified as current were $15.8 million and $9.6 million at December 31, 2011 and 2010, respectively. Current amounts are recorded in other current assets and noncurrent amounts are recorded in other assets in the accompanying consolidated balance sheets.

Revenue Recognition

Revenues include sales to customers of coal produced at Company operations and coal purchased from third parties. The Company recognizes revenue at the time risk of loss passes to the customer at contracted amounts. Transportation costs are included in cost of sales and amounts billed by the Company to its customers for transportation are included in revenues.

Other Operating Income, Net

Other operating income, net in the accompanying consolidated statements of income reflects income and expense from sources other than physical coal sales, including: bookouts, the practice of offsetting purchase and sale contracts for shipping convenience purposes, and contract settlements; royalties earned from properties leased to third parties; income from equity investments; gains and losses from dispositions of assets; and realized gains and losses on derivatives that do not qualify for hedge accounting and are not held for trading purposes.

Asset Retirement Obligations

The Company's legal obligations associated with the retirement of long-lived assets are recognized at fair value at the time the obligations are incurred. Accretion expense is recognized through the expected settlement date of the obligation. Obligations are incurred at the time development of a mine commences for underground and surface mines or construction begins for support facilities, refuse areas and slurry ponds. The obligation's fair value is determined using a DCF technique and is based upon permit requirements and various estimates and assumptions that would be used by market participants, including estimates of disturbed acreage, reclamation costs and assumptions regarding equipment productivity. Upon initial recognition of a liability, a corresponding amount is capitalized as part of the carrying value of the related long-lived asset.

The Company reviews its asset retirement obligation at least annually and makes necessary adjustments for permit changes as granted by state authorities and for revisions of estimates of the amount and timing of costs. For ongoing operations, adjustments to the liability result in an adjustment to the corresponding asset. For idle operations, adjustments to the liability are recognized as income or expense in the period the adjustment is recorded. Any difference between the recorded obligation and the actual cost of reclamation is recorded in profit or loss in the period the obligation is settled. See additional discussion in Note 14, "Asset Retirement Obligations."

Derivative Instruments

The Company generally utilizes derivative instruments to manage exposures to commodity prices. Additionally, the Company may hold certain coal derivative instruments for trading purposes. Derivative financial instruments are recognized in the balance sheet at fair value. Certain coal contracts may meet the definition of a derivative instrument, but because they provide for the physical purchase or sale of coal in quantities expected to be used or sold by the Company over a reasonable period in the normal course of business, they are not recognized on the balance sheet.

Certain derivative instruments are designated as the hedge instrument in a hedging relationship. In a fair value hedge, the Company hedges the risk of changes in the fair value of a firm commitment, typically a fixed-price coal sales contract. Changes in both the hedged firm commitment and the fair value of a derivative used as a hedge instrument in a fair value hedge are recorded in earnings. In a cash flow hedge, the Company hedges the risk of changes in future cash flows related to a forecasted purchase or sale. Changes in the fair value of the derivative instrument used as a hedge instrument in a cash flow hedge are recorded in other comprehensive income. Amounts in other comprehensive income are reclassified to earnings when the hedged transaction affects earnings and are classified in a manner consistent with the transaction being hedged. The Company formally documents the relationships between hedging instruments and the respective hedged items, as well as its risk management objectives for hedge transactions.

The Company evaluates the effectiveness of its hedging relationships both at the hedge's inception and on an ongoing basis. Any ineffective portion of the change in fair value of a derivative instrument used as a hedge instrument in a fair value or cash flow hedge is recognized immediately in earnings. The ineffective portion is based on the extent to which exact offset is not achieved between the change in fair value of the hedge instrument and the cumulative change in expected future cash flows on the hedged transaction from inception of the hedge in a cash flow hedge or the change in the fair value. Ineffectiveness was insignificant for the years ended December 31, 2011, 2010 and 2009. See Note 10, "Derivative Instruments" for further disclosures related to the Company's derivative instruments.

   

Fair Value

Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly hypothetical transaction between market participants at a given measurement date. Valuation techniques used must maximize the use of observable inputs and minimize the use of unobservable inputs. See Note 13, "Fair Values of Financial Instruments" for further disclosures related to the Company's fair value estimates.

Income Taxes

Deferred income taxes are provided for temporary differences arising from differences between the financial statement amount and tax basis of assets and liabilities existing at each balance sheet date using enacted tax rates anticipated to be in effect when the related taxes are expected to be paid or recovered. A valuation allowance is established if it is more likely than not that a deferred tax asset will not be realized. In determining the need for a valuation allowance, the Company considers projected realization of tax benefits based on expected levels of future taxable income, available tax planning strategies and its overall deferred tax position. See Note 12, "Taxes" for further disclosures about income taxes.

Benefit Plans

The Company has non-contributory defined benefit pension plans covering most of its salaried and hourly employees. Benefits are generally based on the employee's age and compensation. The Company also currently provides certain postretirement medical and life insurance coverage for eligible employees. The cost of providing these benefits are determined on an actuarial basis and accrued over the employee's period of active service.

The Company recognizes the overfunded or underfunded status of these plans as determined on an actuarial basis on the balance sheet and the changes in the funded status are recognized in other comprehensive income. See Note 16, "Employee Benefit Plans" for additional disclosures relating to these obligations.

Stock-Based Compensation

The compensation cost of all stock-based awards is determined based on the grant-date fair value of the award, and is recognized in income over the requisite service period. The grant-date fair value of option awards is determined using a Black-Scholes option pricing model. Compensation cost for an award with performance conditions is accrued if it is probable that the conditions will be met. See further discussion in Note 18, "Stock Based Compensation and Other Incentive Plans."

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Quarterly Financial Information

12 Months Ended

Dec. 31, 2011

Quarterly Financial Information [Abstract]

Quarterly Financial Information

25.  Quarterly Financial Information (Unaudited)

Quarterly financial data for the years ended December 31, 2011 and 2010 is summarized below:

	March 31	June 30	September 30	December 31
		(a)(b)	(a)(b)	(a)
	(In thousands, except per share data)
2011:
Revenues	$  872,938	$  985,528	$ 1,198,673	$  1,228,756
Gross profit	129,773	171,440	118,974	153,280
Income from operations	102,238	95,354	76,256	139,728
Net income	55,874	6,630	9,121	71,215
Basic earnings per common share	0.34	0.04	0.04	0.34
Diluted earnings per common share	0.34	0.04	0.04	0.33

	March 31	June 30	September 30	December 31
		(c)	(d)
	(In thousands, except per share data)
2010:
Revenues	$  711,874	$  764,295	$  874,705	$  835,394
Gross profit	61,852	100,461	119,957	107,514
Income from operations	32,200	106,499	98,347	86,938
Net income (loss)	(1,770)	66,274	46,859	48,031
Basic earnings (loss) per common share	(0.01)	0.41	0.29	0.29
Diluted earnings (loss) per common share	(0.01)	0.41	0.29	0.29

____________

(a)	The Company expensed costs related to the acquisition of ICG $98.2 million, $4.7 million and $1.3 million in the second, third and fourth quarters of 2011, respectively.
(b)	The amounts above differ from those previously reported because of fair value adjustments related to the ICG acquisition made in the fourth quarter of 2011 and pushed back to the respective reporting periods.  Net income in the second quarter of 2011 decreased $4.8 million, using an effective tax rate of 37%, from what was originally reported due to increases in cost of sales and depreciation, depletion and amortization expense and net income in the third quarter of 2011 decreased $10.2 million, using an effective tax rate of 37%, from what was originally reported due to an increase in depreciation, depletion and amortization expense.
(c)	In the second quarter of 2010, the Company exchanged 68.4 million tons of coal reserves in the Illinois Basin for an additional 9% ownership interest in Knight Hawk. The Company recognized a gain of $41.6 million on the transaction.
(d)	The Company's Dugout Canyon mine in Carbon County, Utah suspended operations on April 29, 2010 after an increase in carbon monoxide levels resulted from a heating event in a previously mined area. After permanently sealing the area, full coal production resumed on May 21, 2010. On June 22, 2010, an ignition event at the longwall resulted in a second evacuation of all underground employees at the mine. All employees were safely evacuated in both events. The resumption of mining required rendering the mine's atmosphere inert, ventilating the longwall area, determining the cause of the ignition, implementing preventive measures, and securing an MSHA-approved longwall ventilation plan. The longwall system resumed production at normalized levels by the end of September.

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Taxes (Schedule Of Effective Income Tax Rate Reconciliation) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Taxes [Abstract]
Income tax expense at statutory rate	$ 46,933	$ 61,800	$ 8,888
Percentage depletion allowance	(61,971)	(49,152)	(29,463)
State taxes, net of effect of federal taxes	(3,055)	2,299	(61)
Change in valuation allowance	2,416	(383)	725
Other, net	8,088	3,150	3,136
Provision for (benefit from) income taxes	$ (7,589)	$ 17,714	$ (16,775)

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Quarterly Financial Information (Details) (USD $)	3 Months Ended								12 Months Ended							3 Months Ended			1 Months Ended	3 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Parent/Issuer [Member]	Dec. 31, 2010 Parent/Issuer [Member]	Dec. 31, 2009 Parent/Issuer [Member]	Oct. 01, 2009 Jacobs Ranch Mining Operations [Member]	Dec. 31, 2011 ICG [Member]	Sep. 30, 2011 ICG [Member]	Jun. 30, 2011 ICG [Member]	Jun. 30, 2010 Knight Hawk [Member]	Jun. 30, 2010 Knight Hawk [Member]	Jun. 30, 2010 Reserves [Member] Knight Hawk [Member]
Quarterly Financial Information [Line Items]
Revenues	$ 1,228,756,000	$ 1,198,673,000	$ 985,528,000	$ 872,938,000	$ 835,394,000	$ 874,705,000	$ 764,295,000	$ 711,874,000	$ 4,285,895,000	$ 3,186,268,000	$ 2,576,081,000
Gross profit	153,280,000	118,974,000	171,440,000	129,773,000	107,514,000	119,957,000	100,461,000	61,852,000
Income (loss) from operations	139,728,000	76,256,000	95,354,000	102,238,000	86,938,000	98,347,000	106,499,000	32,200,000	413,576,000	323,984,000	123,714,000	424,679,000	309,586,000	103,535,000
Net income	71,215,000	9,121,000	6,630,000	55,874,000	48,031,000	46,859,000	66,274,000	(1,770,000)	142,840,000	159,394,000	42,179,000	142,840,000	159,394,000	42,179,000
Basic earnings (loss) per common share	$ 0.34	$ 0.04	$ 0.04	$ 0.34	$ 0.29	$ 0.29	$ 0.41	$ (0.01)	$ 0.75	$ 0.98	$ 0.28
Diluted earnings (loss) per common share	$ 0.33	$ 0.04	$ 0.04	$ 0.34	$ 0.29	$ 0.29	$ 0.41	$ (0.01)	$ 0.74	$ 0.97	$ 0.28
Tons Of Coal															345,000,000						68,400,000
Additional ownership interest																			9.00%	9.00%
Gain on Knight Hawk transaction							41,600,000			41,577,000									41,600,000
Expensed costs related to acquisition																		98,200,000
Acquisition and transition costs									54,676,000							1,300,000	4,700,000
Quarterly Financial Information, Quarterly Charges and Credits, Amount Reconciling to Previously Reported Results		$ 10,200,000	$ 4,800,000
Effective tax rate (in hundredths)		37.00%	37.00%

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Accumulated Other Comprehensive Income (Loss) (Tables)

12 Months Ended

Dec. 31, 2011

Accumulated Other Comprehensive Income (Loss) [Abstract]

Components Of Accumulated Other Comprehensive Income (Loss)

	Derivative Instruments	Pension, Postretirement    and Other         Post-   Employment      Benefits	Available-for- Sale Securities	Accumulated         Other Comprehensive          Loss
	(In thousands)
Balance at January 1, 2009	$   (45,249)	$                     (33,433)	$         (414)	$       (79,096)
2009 activity, before tax	72,553	20,124	(136)	92,541
2009 activity, tax effect	(26,118)	(7,230)	50	(33,298)
Balance at December 31, 2009	1,186	(20,539)	(500)	(19,853)
2010 activity, before tax	2,711	15,406	2,877	20,994
2010 activity, tax effect	(976)	(5,546)	(1,036)	(7,558)
Balance at December 31, 2010	2,921	(10,679)	1,341	(6,417)
2011 activity, before tax	(11,951)	9,345	176	(2,430)
2011 activity, tax effect	4,301	(3,342)	(62)	897
Balance at December 31, 2011	$     (4,729)	$     (4,676)	$    1,455	$       (7,950)

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Leases (Tables)

12 Months Ended

Dec. 31, 2011

Leases [Abstract]

Schedule Of Operating Lease And Royalties Future Minimum Payments

	Operating      Leases	Royalties
	(In thousands)
2012	$    28,903	$    24,378
2013	27,610	25,595
2014	25,119	25,810
2015	17,641	27,565
2016	9,648	24,397
Thereafter	12,640	114,371
	$  121,561	$  242,116

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Equity Investments And Membership Interests In Joint Ventures (Schedule Of Equity Method Investments) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended			1 Months Ended	12 Months Ended												1 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2010 Knight Hawk [Member]	Dec. 31, 2011 Knight Hawk [Member]	Dec. 31, 2010 Knight Hawk [Member]	Dec. 31, 2009 Knight Hawk [Member]	Dec. 31, 2011 DKRW [Member]	Dec. 31, 2010 DKRW [Member]	Dec. 31, 2009 DKRW [Member]	Dec. 31, 2011 DTA [Member]	Dec. 31, 2010 DTA [Member]	Dec. 31, 2009 DTA [Member]	Dec. 31, 2011 Tenaska [Member]	Dec. 31, 2010 Tenaska [Member]	Dec. 31, 2009 Tenaska [Member]	Jan. 31, 2011 Millennium [Member]	Dec. 31, 2011 Millennium [Member]	Dec. 31, 2010 Millennium [Member]	Dec. 31, 2009 Millennium [Member]	Dec. 31, 2011 Tongue River [Member]	Dec. 31, 2010 Tongue River [Member]	Dec. 31, 2009 Tongue River [Member]
Schedule of Equity Method Investments [Line Items]
Beginning, Balance	$ 177,451	$ 87,268	$ 87,761		$ 131,250	$ 49,603	$ 48,093	$ 21,961	$ 23,589	$ 25,124	$ 14,472	$ 14,076	$ 14,544	$ 9,768
Investments in affiliates	43,489	87,405		26,600		77,637								5,500	9,768		25,000	25,000			12,989
Advances to (distributions from) affiliates, net	(6,646)	(8,375)	(2,239)		(16,621)	(12,639)	(5,164)				6,498	4,264	2,925					3,477
Equity in comprehensive income (loss)	11,311	11,153	1,746		20,596	16,649	6,674	(2,246)	(1,628)	(1,535)	(4,884)	(3,868)	(3,393)	(2)				(2,153)
Ending, Balance	225,605	177,451	87,268	131,250	135,225	131,250	49,603	19,715	21,961	23,589	16,086	14,472	14,076	15,266	9,768			26,324			12,989
Balance at December 31, 2010	23,900				1,700			18,100						4,100
Balance at December 31, 2011	$ 35,810	$ 23,900		$ 1,700		$ 1,700		$ 30,751	$ 18,100					$ 5,059	$ 4,100

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Consolidated Statements Of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Consolidated Statements Of Income [Abstract]
REVENUES	$ 1,228,756	$ 1,198,673	$ 985,528	$ 872,938	$ 835,394	$ 874,705	$ 764,295	$ 711,874	$ 4,285,895	$ 3,186,268	$ 2,576,081
COSTS, EXPENSES AND OTHER
Cost of sales									3,267,910	2,395,812	2,070,715
Depreciation, depletion and amortization									466,587	365,066	301,608
Amortization of acquired sales contracts, net									(22,069)	35,606	19,623
Selling, general and administrative expenses									119,056	118,177	97,787
Change in fair value of coal derivatives and coal trading activities, net									(2,907)	8,924	(12,056)
Acquisition and transition costs									54,676
Gain on Knight Hawk transaction							(41,600)			(41,577)
Other operating income, net									(10,934)	(19,724)	(39,036)
Total operating expenses									3,872,319	2,862,284	2,452,367
Income from operations	139,728	76,256	95,354	102,238	86,938	98,347	106,499	32,200	413,576	323,984	123,714
Interest expense, net:
Interest expense									(230,186)	(142,549)	(105,932)
Interest income									3,309	2,449	7,622
Interest expense, net									(226,877)	(140,100)	(98,310)
Other non-operating expense:
Bridge financing costs related to ICG									(49,490)
Net loss resulting from early retirement of debt									(1,958)	(6,776)
Other non-operating expense, Total									(51,448)	(6,776)
Income before income taxes									135,251	177,108	25,404
Provision for (benefit from) income taxes									(7,589)	17,714	(16,775)
Net income	71,215	9,121	6,630	55,874	48,031	46,859	66,274	(1,770)	142,840	159,394	42,179
Less: Net income attributable to noncontrolling interest									(1,157)	(537)	(10)
Net income attributable to Arch Coal, Inc.									$ 141,683	$ 158,857	$ 42,169
EARNINGS PER COMMON SHARE
Basic earnings per common share	$ 0.34	$ 0.04	$ 0.04	$ 0.34	$ 0.29	$ 0.29	$ 0.41	$ (0.01)	$ 0.75	$ 0.98	$ 0.28
Diluted earnings per common share	$ 0.33	$ 0.04	$ 0.04	$ 0.34	$ 0.29	$ 0.29	$ 0.41	$ (0.01)	$ 0.74	$ 0.97	$ 0.28
Basic weighted average shares outstanding									190,086	162,398	150,963
Diluted weighted average shares outstanding									190,905	163,210	151,272
Dividends declared per common share									$ 0.43	$ 0.39	$ 0.36

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Taxes (Tables)

12 Months Ended

Dec. 31, 2011

Taxes [Abstract]

Schedule Of Components Of Income Tax

	Year Ended December 31
	2011	2010	2009
	(In thousands)
Current:
Federal	$   (20,164)	$    34,304	$    21,295
State	1,212	2,283	864
Total current	(18,952)	36,587	22,159
Deferred:
Federal	13,214	(18,506)	(39,492)
State	(1,851)	(367)	558
Total deferred	11,363	(18,873)	(38,934)
	$     (7,589)	$    17,714	$   (16,775)

Schedule Of Effective Income Tax Rate Reconciliation

	Year Ended December 31
	2011	2010	2009
	(In thousands)
Income tax expense at statutory rate	$    46,933	$     61,800	$       8,888
Percentage depletion allowance	(61,971)	(49,152)	(29,463)
State taxes, net of effect of federal taxes	(3,055)	2,299	(61)
Change in valuation allowance	2,416	(383)	725
Other, net	8,088	3,150	3,136
	$     (7,589)	$      17,714	$    (16,775)

Schedule Of Deferred Tax Assets And Liabilities

	December 31
	2011	2010
	(In thousands)
Deferred tax assets:
Alternative minimum tax credit carryforwards	$   151,404	$   170,592
Net operating loss carryforwards	324,393	102,355
Reclamation and mine closure	93,914	71,533
Advance royalties	—	38,557
Plant and equipment	—	19,846
Acquired sales contracts	44,717	20,120
Other, primarily accrued liabilities	171,715	90,412
Gross deferred tax assets	786,143	513,415
Valuation allowance	(2,831)	(737)
Total deferred tax assets	783,312	512,678
Deferred tax liabilities
Plant and equipment	1,566,769	—
Deferred development	67,728	76,690
Investment in tax partnerships	66,502	68,538
Other	17,015	13,669
Total deferred tax liabilities	1,718,014	158,897
Net deferred tax asset (liability)	(934,702)	353,781
Current asset (liability)	42,051	(7,775)
Non-current deferred tax asset (liability)	$     (976,753)	$  361,556

Schedule Of Unrecognized Tax Benefits

Balance at January 1, 2009	$    4,878
Additions based on tax positions related to the current year	1,593
Additions for tax positions of prior years	205
Reductions for tax positions of prior years	(6)
Balance at December 31, 2009	6,670
Additions based on tax positions related to the current year	1,493
Additions for tax positions of prior years	85
Reductions for tax positions of prior years	(3,830)
Balance at December 31, 2010	4,418
Additions based on tax positions related to the current year	1,626
Additions for tax positions of prior years	2,754
Balance at December 31, 2011	$    8,798

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Employee Benefit Plans (Schedule Of Net Benefit Costs) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 16,490		$ 15,870		$ 13,444
Interest cost	16,253		15,822		15,946
Expected return on plan assets	(21,812)	[1]	(19,392)	[1]	(17,719)	[1]
Amortization of prior service cost (credit)	(189)		173		193
Amortization of other actuarial (gains) losses	8,748		7,130		3,967
Curtailments					585
Net benefit cost	19,490		19,603		16,416
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	3,917		1,509		2,954
Interest cost	3,279		2,083		3,667
Expected return on plan assets		[1]		[1]		[1]
Amortization of prior service cost (credit)	(2,364)		(2,364)		2,161
Amortization of other actuarial (gains) losses	(3,100)		(2,918)		(2,897)
Net benefit cost	$ 1,732		$ (1,690)		$ 5,885

[1] The Company does not fund its other postretirement benefit obligations.

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Segment Information (Reconciliation Statement Of Segment Income From Operations To Consolidated Income Before Income Taxes) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Segment Information [Abstract]
Income (loss) from operations	$ 139,728	$ 76,256	$ 95,354	$ 102,238	$ 86,938	$ 98,347	$ 106,499	$ 32,200	$ 413,576	$ 323,984	$ 123,714
Interest expense									(230,186)	(142,549)	(105,932)
Interest income									3,309	2,449	7,622
Bridge financing costs related to ICG									(49,490)
Net loss resulting from early retirement of debt									(1,958)	(6,776)
Income before income taxes									$ 135,251	$ 177,108	$ 25,404

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Consolidated Statements Of Stockholders' Equity (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Common dividends, per share	$ 0.43	$ 0.39	$ 0.36
Stock issued during period, shares, new issues	48,705		19,550
Issuance of shares of common stock under the stock incentive plan - restricted stock and restricted stock units	162	9	45
Issuance of shares of common stock under the stock incentive plan - stock options including income tax benefits	199	155	13
Common Stock [Member]
Stock issued during period, shares, new issues	48,705		19,550
Issuance of shares of common stock under the stock incentive plan - restricted stock and restricted stock units	162	9	45
Issuance of shares of common stock under the stock incentive plan - stock options including income tax benefits	199	155	13
Paid-In Capital [Member]
Stock issued during period, shares, new issues	48,705		19,550
Issuance of shares of common stock under the stock incentive plan - restricted stock and restricted stock units	162	9	45
Issuance of shares of common stock under the stock incentive plan - stock options including income tax benefits	199	155	13
Retained Earnings [Member]
Common dividends, per share	$ 0.43	$ 0.39	$ 0.36

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Employee Benefit Plans (Narrative) (Details) (USD $)	12 Months Ended				12 Months Ended			12 Months Ended			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Pension Benefits [Member]	Dec. 31, 2010 Pension Benefits [Member]	Dec. 31, 2009 Pension Benefits [Member]	Dec. 31, 2011 Other Postretirement Benefits [Member]	Dec. 31, 2010 Other Postretirement Benefits [Member]	Dec. 31, 2009 Other Postretirement Benefits [Member]	Dec. 31, 2011 Other Pension Plans, Postretirement or Supplemental Plans, Defined Benefit [Member]	Dec. 31, 2010 Other Pension Plans, Postretirement or Supplemental Plans, Defined Benefit [Member]	Dec. 31, 2009 Other Pension Plans, Postretirement or Supplemental Plans, Defined Benefit [Member]	Dec. 31, 2009 Post-Remeasurement [Member]	Dec. 31, 2009 Pre-Remeasurement [Member]
Defined Benefit Plan Disclosure [Line Items]
Amendment to benefit plan, adjustment to benefit obligation		$ 55,500,000		$ 21,000,000
Postretirement benefit obligation, decrease in discount rate					4.91%	5.71%		4.52%	5.23%					5.68%	6.85%
Accumulated benefit obligation of pension plans		314,700,000	280,400,000
Benefit obligation for the unfunded pension plan		8,200,000
Accumulated benefit obligation for the unfunded pension plan		7,100,000
Benefit obligations					333,951,000	297,707,000	280,693,000	45,129,000	39,633,000	46,445,000
Amortization of net prior service cost					(100,000)			(12,000,000)
Defined Benefit Plan, Amortization of Net Gains (Losses)					(14,300,000)			400,000
Defined benefit plan amortization period		5
Health care cost trend rate assumed		7.70%
Ultimate trend rate		4.50%
Defined Benefit Plan, Year that Rate Reaches Ultimate Trend Rate		2028
Effect of one-percentage-point increase in health care cost trend rate		500,000
Effect of one-percentage-point decrease in health care cost trend rate		400,000
Percentage of plan assets, equity securities		65.00%
Percentage of plan assets, fixed income securities		30.00%
Percentage of plan assets, cash		5.00%
Contributions to the pension plans	24,500,000
Other postretirement benefits payments											$ 25,900,000	$ 18,100,000	$ 15,900,000

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Property Transactions (Details) (USD $) In Millions, unless otherwise specified	Mar. 18, 2010 Montana Otter Creek [Member]	Nov. 12, 2009 Great Northern Properties Limited Partnership [Member]	Dec. 14, 2011 South Hilight [Member]	Dec. 31, 2011 Reserves [Member] Montana Otter Creek [Member]	Dec. 31, 2011 Reserves [Member] South Hilight [Member]	Dec. 31, 2011 Capital Additions [Member]
Property, Plant and Equipment [Line Items]
Mining operations purchase price	$ 85.8	$ 73.1	$ 300.0
Coal reserve in tons				1,400,000,000	222,000,000
Unrecorded Unconditional Purchase Obligation Due Current						23.4
Unrecorded Unconditional Purchase Obligation Due in Two Years						83.4
Unrecorded Unconditional Purchase Obligation Due in Three Years						67.3
Unrecorded Unconditional Purchase Obligation Due in Four Years						60.0
Unrecorded Unconditional Purchase Obligation Due in Five Years						$ 60.0

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Employee Benefit Plans (Schedule Of Allocation Of Plan Assets) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 285,074		$ 247,713
U.S. Small-Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11,178	[1]	10,647	[1]
U.S. Mid-Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	50,264	[1]	46,851	[1]
U.S. Large-Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	91,561	[1]	77,632	[1]
Non-U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	22,509	[1]	24,995	[1]
U.S. Government Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13,454	[2]	3,053	[2]
State And Local Government Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	18,416	[3]	13,679	[3]
Non-U.S. Government Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,968	[4]	3,469	[4]
U.S. Government Asset And Mortgage Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	800	[5]	1,073	[5]
Other Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	51,470	[6]	45,628	[6]
Short-term Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8,029	[7]	6,110	[7]
Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	421	[8]	839	[8]
Corporate fixed income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14,004	[9]	13,737	[9]
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	92,210		72,699
Level 1 [Member] | U.S. Small-Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11,178	[1]	10,647	[1]
Level 1 [Member] | U.S. Mid-Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	23,474	[1]	21,163	[1]
Level 1 [Member] | U.S. Large-Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	44,820	[1]	38,397	[1]
Level 1 [Member] | U.S. Government Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	12,738	[2]	2,492	[2]
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	192,864		175,014
Level 2 [Member] | U.S. Mid-Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	26,790	[1]	25,688	[1]
Level 2 [Member] | U.S. Large-Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	46,741	[1]	39,235	[1]
Level 2 [Member] | Non-U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	22,509	[1]	24,995	[1]
Level 2 [Member] | U.S. Government Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	716	[2]	561	[2]
Level 2 [Member] | State And Local Government Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	18,416	[3]	13,679	[3]
Level 2 [Member] | Non-U.S. Government Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,968	[4]	3,469	[4]
Level 2 [Member] | U.S. Government Asset And Mortgage Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	800	[5]	1,073	[5]
Level 2 [Member] | Other Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	51,470	[6]	45,628	[6]
Level 2 [Member] | Short-term Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8,029	[7]	6,110	[7]
Level 2 [Member] | Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	421	[8]	839	[8]
Level 2 [Member] | Corporate fixed income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14,004	[9]	13,737	[9]
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
Level 3 [Member] | U.S. Small-Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		[1]		[1]
Level 3 [Member] | U.S. Mid-Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		[1]		[1]
Level 3 [Member] | U.S. Large-Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		[1]		[1]
Level 3 [Member] | Non-U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		[1]		[1]
Level 3 [Member] | U.S. Government Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		[2]		[2]
Level 3 [Member] | State And Local Government Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		[3]		[3]
Level 3 [Member] | Non-U.S. Government Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		[4]		[4]
Level 3 [Member] | U.S. Government Asset And Mortgage Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		[5]		[5]
Level 3 [Member] | Other Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		[6]		[6]
Level 3 [Member] | Short-term Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		[7]		[7]
Level 3 [Member] | Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		[8]		[8]
Level 3 [Member] | Corporate fixed income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		[9]		[9]

[1] Equity securities includes investments in 1) common stock, 2) preferred stock and 3) mutual funds. Investments in common and preferred stocks are valued using quoted market prices multiplied by the number of shares owned. Investments in mutual funds are valued at the net asset value per share multiplied by the number of shares held as of the measurement date and are traded on listed exchanges.

[2] U.S. government securities includes agency and treasury debt. These investments are valued using dealer quotes in an active market.

[3] State and local government securities include different U.S. state and local municipal bonds and asset backed securities, these investments are valued utilizing a market approach that includes various valuation techniques and sources such as value generation models, broker quotes, benchmark yields and securities, reported trades, issuer trades and/or other applicable data.

[4] Non-U.S. government securities includes debt securities issued by foreign governments and are valued utilizing a price spread basis valuation technique with observable sources from investment dealers and research vendors.

[5] U.S. government asset and mortgage backed securities includes government-backed mortgage funds which are valued utilizing an income approach that includes various valuation techniques and sources such as discounted cash flows models, benchmark yields and securities, reported trades, issuer trades and/or other applicable data.

[6] Other fixed income investments are actively managed fixed income vehicles that are valued at the net asset value per share multiplied by the number of shares held as of the measurement date.

[7] Short-term investments include governmental agency funds, government repurchase agreements, commingled funds, and pooled funds and mutual funds. Governmental agency funds are valued utilizing an option adjusted spread valuation technique and sources such as interest rate generation processes, benchmark yields and broker quotes. Investments in governmental repurchase agreements, commingled funds and pooled funds and mutual funds are valued at the net asset value per share multiplied by the number of shares held as of the measurement date.

[8] Other investments includes cash, forward contracts, derivative instruments, credit default swaps, interest rate swaps and mutual funds. Investments in interest rate swaps are valued utilizing a market approach that includes various valuation techniques and sources such as value generation models, broker quotes in active and non-active markets, benchmark yields and securities, reported trades, issuer trades and/or other applicable data. Forward contracts and derivative instruments are valued at their exchange listed price or broker quote in an active market. The mutual funds are valued at the net asset value per share multiplied by the number of shares held as of the measurement date and are traded on listed exchanges.

[9] Corporate fixed income is primarily comprised of corporate bonds and certain corporate asset-backed securities that are denominated in the U.S. dollar and are investment-grade securities. These investments are valued using dealer quotes.

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Accounting Policies (Policy)

12 Months Ended

Dec. 31, 2011

Accounting Policies [Abstract]

Basis Of Presentation

Basis of Presentation

The consolidated financial statements include the accounts of Arch Coal, Inc. and its subsidiaries and controlled entities ("the Company"). The Company produces coal from surface and underground mines located throughout the United States for sale to domestic and international customers as steam coal to power plants and industrial facilities and metallurgical coal used in steel production. The Company expanded further into metallurgical coal markets with the acquisition of International Coal Group, Inc. ("ICG") on June 15, 2011, as described in Note 3, "Business Combinations." The Company operates 23 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 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.

Accounting Pronouncements Adopted And New Pronouncements Not Yet Implemented

 Accounting Pronouncements

There were no accounting pronouncements whose adoption had, or is expected to have, a material impact on the Company's consolidated financial statements.

Accounting Estimates

Accounting Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and revenues and expenses in the accompanying consolidated financial statements and the disclosure of contingent assets and liabilities. Actual results could differ from those estimates.

Cash And Cash Equivalents

Cash and Cash Equivalents

Cash and cash equivalents are stated at cost. Cash equivalents consist of highly-liquid investments with an original maturity of three months or less when purchased. At December 31, 2011 and 2010, the carrying amounts of cash and cash equivalents approximate their fair value.

Allowance For Uncollectible Receivables

Allowance for Uncollectible Receivables

The Company establishes an allowance for uncollectible receivables for the amounts of trade accounts receivable and other receivables that are not expected to be collected, based on past collection history, the economic environment and specified risks identified in the receivables portfolio. Receivables are considered past due if the full payment is not received by the contractual due date. At December 31, 2011 and 2010, there was either no allowance or an insignificant allowance for uncollectible receivables.

Inventories

Inventories

Coal and supplies inventories are valued at the lower of average cost or market. Coal inventory costs include labor, supplies, equipment costs, transportation costs incurred prior to the transfer of title to customers and operating overhead. The costs of removing overburden, called stripping costs, incurred during the production phase of the mine are considered variable production costs and are included in the cost of the coal extracted during the period the stripping costs are incurred.

Investments And Membership Interests In Joint Ventures

Investments and Membership Interests in Joint Ventures

Investments and membership interests in joint ventures are accounted for under the equity method of accounting if the Company has the ability to exercise significant influence, but not control, over the entity. The Company's share of the entity's income is reflected in other operating income, net in the consolidated statements of income. Information about investment activity is provided in Note 8, "Equity Investments and Membership Interests in Joint Ventures."

Marketable equity securities held by the Company that do not qualify for equity method accounting are classified as available-for-sale and are recorded at their fair value on the balance sheet. Unrealized gains and losses on these investments are recorded in other comprehensive income. A decline in the value of an investment that is considered other-than-temporary is recognized in income.

Prepaid Royalties

Prepaid Royalties

Leased mineral rights are often acquired through royalty payments. When royalty payments represent prepayments recoupable against future production, they are recorded as a prepaid asset, with amounts expected to be recouped within one year classified as current. When the coal is mined under these leases the royalties are recouped and the prepayment is charged to cost of sales.

Acquired Sales Contracts

Acquired Sales Contracts

Coal supply agreements (sales contracts) acquired in a business combination are capitalized at their fair value and amortized over the tons of coal shipped during the term of the contract. The fair value of a sales contract is determined by discounting the cash flows attributable to the difference between the contract price and the prevailing forward prices for the tons under contract at the date of acquisition. See Note 6, "Acquired Sales Contracts" for further information related to the Company's acquired sales contracts.

Exploration Costs

Exploration Costs

Costs to acquire permits for exploration activities are capitalized. Drilling and other costs related to locating coal deposits and evaluating the economic viability of such deposits are expensed as incurred.

Property, Plant And Equipment

 

Property, Plant and Equipment

Plant and Equipment

Plant and equipment are recorded at cost. Interest costs incurred during the construction period for major asset additions are capitalized. Expenditures that extend the useful lives of existing plant and equipment or increase the productivity of the asset are capitalized. The cost of maintenance and repairs that do not extend the useful life or increase the productivity of the asset are expensed as incurred.

Preparation plants and loadouts are depreciated using the units-of-production method over the estimated recoverable reserves, subject to a minimum level of depreciation. Other plant and equipment are depreciated principally using the straight-line method over the estimated useful lives of the assets, limited by the remaining life of the mine. The useful lives of mining equipment, including longwalls, draglines and shovels, range from 5 to 32 years. The useful lives of buildings and leasehold improvements generally range from 10 to 30 years.

Deferred Mine Development

Costs of developing new mines or significantly expanding the capacity of existing mines are capitalized and amortized using the units-of-production method over the estimated recoverable reserves that are associated with the property being benefited. Costs may include construction permits and licenses; mine design; construction of access roads, shafts, slopes and main entries; and removing overburden to access reserves in a new pit. Additionally, deferred mine development includes the asset cost associated with asset retirement obligations.

Coal Lands and Mineral Rights

Rights to coal reserves may be acquired directly through governmental or private entities. A significant portion of the Company's coal reserves are controlled through leasing arrangements. The net book value of the Company's leased coal interests was $1.6 billion at December 31, 2011 and 2010. Payments to acquire royalty lease agreements and lease bonus payments are capitalized as a cost of the underlying mineral reserves and depleted over the life of proven and probable reserves. Coal lease rights are depleted using the units-of-production method, and the rights are assumed to have no residual value. Lease agreements are generally long-term in nature (original terms range from 10 to 50 years), and substantially all of the leases contain provisions that allow for automatic extension of the lease term providing certain requirements are met. See Note 2, "Property Transactions" for further disclosures on coal lease agreements.

Impairment

      If facts and circumstances suggest that the carrying value of a long-lived asset or asset group may not be recoverable, the asset or asset group is reviewed for potential impairment. If this review indicates that the carrying amount of the asset will not be recoverable through projected undiscounted cash flows generated by the asset and its related asset group over its remaining life, then an impairment loss is recognized by reducing the carrying value of the asset to its fair value. The Company may, under certain circumstances, idle mining operations in response to market conditions or other factors. Because an idling is not a permanent closure, it is not considered an automatic indicator of impairment.

Goodwill

 Goodwill

In a business combination, goodwill represents the excess of the purchase price over the fair value assigned to the net tangible and identifiable intangible assets acquired. The Company tests goodwill for impairment annually as of the beginning of the fourth quarter, or when circumstances indicate a possible impairment may exist. If the results of the testing indicate that the carrying amount of a reporting unit exceeds the fair value of the reporting unit, the fair value of goodwill must be calculated. An impairment loss generally would be recognized when the carrying amount of goodwill exceeds the implied fair value of goodwill, determined by subtracting the fair value of the other assets and liabilities associated with the reporting unit from the total fair value of the reporting unit. The fair value of a reporting unit is determined using a discounted cash flow ("DCF") technique. A number of significant assumptions and estimates are involved in the application of the DCF analysis to forecast operating cash flows, including the discount rate and projections of selling prices and costs to produce.

Deferred Financing Costs

Deferred Financing Costs

The Company capitalizes costs incurred in connection with new borrowings, the establishment or enhancement of credit facilities and the issuance of debt securities. These costs are amortized as an adjustment to interest expense over the life of the borrowing or term of the credit facility using the interest method. The unamortized balance of deferred financing costs was $90.5 million and $37.6 million at December 31, 2011 and 2010, respectively. Amounts classified as current were $15.8 million and $9.6 million at December 31, 2011 and 2010, respectively. Current amounts are recorded in other current assets and noncurrent amounts are recorded in other assets in the accompanying consolidated balance sheets.

Revenue Recognition

Revenue Recognition

Revenues include sales to customers of coal produced at Company operations and coal purchased from third parties. The Company recognizes revenue at the time risk of loss passes to the customer at contracted amounts. Transportation costs are included in cost of sales and amounts billed by the Company to its customers for transportation are included in revenues.

Other Operating Income, Net

Other Operating Income, Net

Other operating income, net in the accompanying consolidated statements of income reflects income and expense from sources other than physical coal sales, including: bookouts, the practice of offsetting purchase and sale contracts for shipping convenience purposes, and contract settlements; royalties earned from properties leased to third parties; income from equity investments; gains and losses from dispositions of assets; and realized gains and losses on derivatives that do not qualify for hedge accounting and are not held for trading purposes.

Asset Retirement Obligations

Asset Retirement Obligations

The Company's legal obligations associated with the retirement of long-lived assets are recognized at fair value at the time the obligations are incurred. Accretion expense is recognized through the expected settlement date of the obligation. Obligations are incurred at the time development of a mine commences for underground and surface mines or construction begins for support facilities, refuse areas and slurry ponds. The obligation's fair value is determined using a DCF technique and is based upon permit requirements and various estimates and assumptions that would be used by market participants, including estimates of disturbed acreage, reclamation costs and assumptions regarding equipment productivity. Upon initial recognition of a liability, a corresponding amount is capitalized as part of the carrying value of the related long-lived asset.

The Company reviews its asset retirement obligation at least annually and makes necessary adjustments for permit changes as granted by state authorities and for revisions of estimates of the amount and timing of costs. For ongoing operations, adjustments to the liability result in an adjustment to the corresponding asset. For idle operations, adjustments to the liability are recognized as income or expense in the period the adjustment is recorded. Any difference between the recorded obligation and the actual cost of reclamation is recorded in profit or loss in the period the obligation is settled. See additional discussion in Note 14, "Asset Retirement Obligations."

Derivative Instruments

Derivative Instruments

The Company generally utilizes derivative instruments to manage exposures to commodity prices. Additionally, the Company may hold certain coal derivative instruments for trading purposes. Derivative financial instruments are recognized in the balance sheet at fair value. Certain coal contracts may meet the definition of a derivative instrument, but because they provide for the physical purchase or sale of coal in quantities expected to be used or sold by the Company over a reasonable period in the normal course of business, they are not recognized on the balance sheet.

Certain derivative instruments are designated as the hedge instrument in a hedging relationship. In a fair value hedge, the Company hedges the risk of changes in the fair value of a firm commitment, typically a fixed-price coal sales contract. Changes in both the hedged firm commitment and the fair value of a derivative used as a hedge instrument in a fair value hedge are recorded in earnings. In a cash flow hedge, the Company hedges the risk of changes in future cash flows related to a forecasted purchase or sale. Changes in the fair value of the derivative instrument used as a hedge instrument in a cash flow hedge are recorded in other comprehensive income. Amounts in other comprehensive income are reclassified to earnings when the hedged transaction affects earnings and are classified in a manner consistent with the transaction being hedged. The Company formally documents the relationships between hedging instruments and the respective hedged items, as well as its risk management objectives for hedge transactions.

The Company evaluates the effectiveness of its hedging relationships both at the hedge's inception and on an ongoing basis. Any ineffective portion of the change in fair value of a derivative instrument used as a hedge instrument in a fair value or cash flow hedge is recognized immediately in earnings. The ineffective portion is based on the extent to which exact offset is not achieved between the change in fair value of the hedge instrument and the cumulative change in expected future cash flows on the hedged transaction from inception of the hedge in a cash flow hedge or the change in the fair value. Ineffectiveness was insignificant for the years ended December 31, 2011, 2010 and 2009. See Note 10, "Derivative Instruments" for further disclosures related to the Company's derivative instruments.

Fair Value

Fair Value

Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly hypothetical transaction between market participants at a given measurement date. Valuation techniques used must maximize the use of observable inputs and minimize the use of unobservable inputs. See Note 13, "Fair Values of Financial Instruments" for further disclosures related to the Company's fair value estimates.

Income Taxes

Income Taxes

Deferred income taxes are provided for temporary differences arising from differences between the financial statement amount and tax basis of assets and liabilities existing at each balance sheet date using enacted tax rates anticipated to be in effect when the related taxes are expected to be paid or recovered. A valuation allowance is established if it is more likely than not that a deferred tax asset will not be realized. In determining the need for a valuation allowance, the Company considers projected realization of tax benefits based on expected levels of future taxable income, available tax planning strategies and its overall deferred tax position. See Note 12, "Taxes" for further disclosures about income taxes.

Benefit Plans

Benefit Plans

The Company has non-contributory defined benefit pension plans covering most of its salaried and hourly employees. Benefits are generally based on the employee's age and compensation. The Company also currently provides certain postretirement medical and life insurance coverage for eligible employees. The cost of providing these benefits are determined on an actuarial basis and accrued over the employee's period of active service.

The Company recognizes the overfunded or underfunded status of these plans as determined on an actuarial basis on the balance sheet and the changes in the funded status are recognized in other comprehensive income. See Note 16, "Employee Benefit Plans" for additional disclosures relating to these obligations.

Stock-Based Compensation

Stock-Based Compensation

The compensation cost of all stock-based awards is determined based on the grant-date fair value of the award, and is recognized in income over the requisite service period. The grant-date fair value of option awards is determined using a Black-Scholes option pricing model. Compensation cost for an award with performance conditions is accrued if it is probable that the conditions will be met. See further discussion in Note 18, "Stock Based Compensation and Other Incentive Plans."

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Goodwill (Schedule Of Goodwill) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Goodwill [Line Items]
Goodwill, Beginning Balance	$ 114,963	$ 113,701	$ 46,832
Consideration paid related to prior business acquisitions	829	1,262	4,767
Goodwill, Ending Balance	596,103	114,963	113,701
Parent/Issuer [Member]
Goodwill [Line Items]
Consideration paid related to prior business acquisitions	829	1,262	4,767
Jacobs Ranch [Member]
Goodwill [Line Items]
Acquisition during period			62,102
ICG [Member]
Goodwill [Line Items]
Acquisition during period	$ 480,311

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Accrued Workers' Compensation

12 Months Ended

Dec. 31, 2011

Accrued Workers' Compensation [Abstract]

Accrued Workers' Compensation

15.  Accrued Workers' Compensation

The Company is liable under the Federal Mine Safety and Health Act of 1969, as subsequently amended, to provide for pneumoconiosis (occupational disease) benefits to eligible employees, former employees, and dependents. The Company is also liable under various states' statutes for occupational disease benefits. The Company currently provides for federal and state claims principally through a self-insurance program. The occupational disease benefit obligation represents the present value of the actuarially computed present and future liabilities for such benefits over the employees' applicable years of service.

In addition, the Company is liable for workers' compensation benefits for traumatic injuries that are accrued as injuries are incurred. Traumatic claims are either covered through self-insured programs or through state-sponsored workers' compensation programs.

Workers' compensation expense consists of the following components:

	Year Ended December 31
	2011	2010	2009
	(In thousands)
Self-insured occupational disease benefits:
Service cost	$    2,059	$       727	$        531
Interest cost	1,799	675	558
Net amortization	(493)	(1,860)	(2,879)
Total occupational disease	3,365	(458)	(1,790)
Traumatic injury claims and assessments	16,979	9,263	8,904
Total workers' compensation expense	$  20,344	$    8,805	$     7,114

The increase in total workers' compensation expense for the year ended 2011 is related to the acquisition of ICG.

The reconciliation of changes in the benefit obligation of the occupational disease liability is as follows:

	December 31
	2011	2010
	(In thousands)
Beginning of year obligation	$  17,412	$  9,702
Service cost	2,059	727
Interest cost	1,799	675
Actuarial loss	7,081	6,993
Benefit and administrative payments	(1,097)	(685)
Acquisition of ICG	26,930	—
Net obligation at end of year	$  54,184	$ 17,412

At December 31, 2011 and 2010, accumulated losses of $5.5 million and accumulated gains of $2.0 million, respectively, were not yet recognized in occupational disease cost and were recorded in accumulated other comprehensive income. The expected accumulated loss that will be amortized from accumulated other comprehensive income into occupational disease cost in 2012 is $1.1 million.

The following table provides the assumptions used to determine the projected occupational disease obligation:

	Year Ended December 31
	2011	2010	2009
Weighted average assumptions:
Discount rate	5.10%	5.96%	6.11%
Cost escalation rate	3.00%	3.00%	3.00%

Summarized below is information about the amounts recognized in the accompanying consolidated balance sheets for workers' compensation benefits:

	December 31
	2011	2010
	(In thousands)
Occupational disease costs	$  54,184	$  17,412
Traumatic and other workers' compensation claims	29,430	24,537
Total obligations	83,614	41,949
Less amount included in accrued expenses	11,666	6,659
Noncurrent obligations	$  71,948	$  35,290

As of December 31, 2011, the Company had $60.1 million in surety bonds and letters of credit outstanding to secure workers' compensation obligations.

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Business Combination (Tables)

12 Months Ended

Dec. 31, 2011

Business Combinations [Abstract]

Summary Of Purchase Price Allocation

	(In millions)
Consideration paid, net of cash acquired	$	2,894.4
Recognized amounts of net tangible and intangible assets acquired and liabilities assumed:
Restricted cash	15.5
Receivables	113.2
Inventories	91.0
Net property, plant and equipment, including mineral rights	4,582.6
Goodwill	480.3
Other assets	35.9
Accounts payable	(86.0		)
Other accrued expenses and current liabilities	(59.1		)
Debt	(604.8		)
Litigation accrual	(108.9		)
Accrued postretirement benefits	(47.7		)
Asset retirement obligation	(112.7		)
Coal supply agreements, net	(91.0		)
Deferred income taxes, net	(1,278.9		)
Other	(35.0		)
Net tangible and intangible assets acquired	$	2,894.4

Summary Of Unaudited Pro Forma

		Year Ended December 31,
		2011				2010
			(In millions)
Total revenues
As reported	$	4,285.9		$	3,186.3
Pro forma	$	4,825.6		$	4,299.9
Net income attributable to Arch Coal
As reported	$	141.7		$	158.9
Pro forma	$	113.5		$	(1.2)

Schedule Of Costs And Expenses Reflected In The Income Before Income Taxes

		(In millions)
Costs of completing the acquisition	$	31.6
Severance costs		15.8
Write off of acquired assets		7.3
Bridge financing fees		49.5
	$	104.2

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Employee Benefit Plans (Schedule Of Assumptions Used) (Details)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plan Disclosure [Line Items]
Discount rate			0.00%
Rate of compensation increase	0.00%	0.00%	0.00%
Expected return on plan assets	0.00%	0.00%	0.00%
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	5.71%	5.97%	6.85%
Rate of compensation increase	3.39%	3.39%	3.39%
Expected return on plan assets	8.50%	8.50%	8.50%
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	5.23%	5.67%
Pre-Remeasurement [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate			6.85%
Post-Remeasurement [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate			5.68%

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Capital Stock

12 Months Ended

Dec. 31, 2011

Capital Stock [Abstract]

Capital Stock

17.  Capital Stock

On March 14, 2006, the Company filed a registration statement on Form S-3 with the SEC. The registration statement allows the Company to offer, from time to time, an unlimited amount of debt securities, preferred stock, depositary shares, purchase contracts, purchase units, common stock and related rights and warrants.

Common Stock

On June 8, 2011, the Company sold 48 million shares of its common stock at a public offering price of $27.00 per share. The $1.25 billion in net proceeds from the issuance were used to finance the acquisition of ICG. On July 8, 2011, the Company issued an additional 0.7 million shares of its common stock under the same terms and conditions to cover underwriters' over-allotments for net proceeds of $18.4 million.

On July 31, 2009, the Company sold 17 million shares of its common stock at a public offering price of $17.50 per share and on August 6, 2009, the Company issued an additional 2.55 million shares of its common stock under the same terms and conditions to cover underwriters' over-allotments. The net proceeds received from the issuance of common stock were $326.5 million, which was used primarily to finance the purchase of the Jacobs Ranch mining complex in 2009.

Stock Repurchase Plan

The Company's share repurchase program allows for the purchase of up to 14,000,000 shares of the Company's common stock. At December 31, 2011, 10,925,800 shares of common stock were available for repurchase under the plan. There were no purchases made under the plan during 2011, 2010 or 2009. There is no expiration date on the program. Any future repurchases under the plan will be made at management's discretion and will depend on market conditions and other factors.

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Acquired Sales Contracts (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Acquired Sales Contracts [Abstract]
Coal supply agreement asset, purchase price allocation	$ 35.0
Coal supply agreement liability, purchase price allocation	126.0
Amortization expense (income) of acquired sales contracts, year 2012	18.5
Amortization expense (income) of acquired sales contracts, year 2013	5.2
Amortization expense (income) of acquired sales contracts, year 2014	3.3
Amortization expense (income) of acquired sales contracts, year 2015	12.7
Amortization expense (income) of acquired sales contracts, year 2016	$ 7.7

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Earnings Per Common Share (Details)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Earnings Per Common Share [Abstract]
Basic weighted average shares outstanding	190,086,000	162,398,000	150,963,000
Effect of common stock equivalents under incentive plans	819,000	812,000	309,000
Diluted weighted average shares outstanding	190,905,000	163,210,000	151,272,000
Effect of options to purchase common stock	2,600,000	2,500,000	2,200,000

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Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
OPERATING ACTIVITIES
Net income	$ 142,840	$ 159,394	$ 42,179
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation, depletion and amortization	466,587	365,066	301,608
Amortization of acquired sales contracts, net	(22,069)	35,606	19,623
Bridge financing costs related to ICG	49,490
Write down of assets acquired from ICG	7,316
Prepaid royalties expensed	34,842	34,605	29,746
Employee stock-based compensation	10,882	11,717	13,394
Amortization relating to financing activities	14,067	10,398	6,741
Gain on Knight Hawk transaction		(41,577)
Net loss resulting from early retirement of debt	1,958	6,776
Changes in operating assets and liabilities:
Receivables	(74,914)	(7,287)	47,794
Inventories	(50,900)	5,160	(28,518)
Coal derivative assets and liabilities	6,079	9,554	32,266
Accounts payable, accrued expenses and other current liabilities	52,191	87,807	(44,764)
Income tax payable/receivable	(21,759)	(1,364)	2,100
Deferred income taxes	10,519	(12,405)	(34,668)
Asset retirement obligations	3,868	23,997	18,741
Other	11,245	9,700	(23,262)
Cash provided by operating activities	642,242	697,147	382,980
INVESTING ACTIVITIES
Acquisitions of businesses, net of cash acquired	(2,894,339)		(768,819)
Increase in restricted cash	5,167
Capital expenditures	(540,936)	(314,657)	(323,150)
Proceeds from dispositions of property, plant and equipment	25,887	330	825
Additions to prepaid royalties	(29,957)	(27,355)	(26,755)
Purchases of investments and advances to affiliates	(61,909)	(46,185)	(10,925)
Consideration paid related to prior business acquisitions	(829)	(1,262)	(4,767)
Reimbursement of deposits on equipment			3,209
Cash used in investing activities	(3,496,916)	(389,129)	(1,130,382)
FINANCING ACTIVITIES
Proceeds from the issuance of senior notes	2,000,000	500,000	584,784
Proceeds from the issuance of common stock, net	1,267,933		326,452
Payments to retire debt	(605,178)	(505,627)
Net increase (decrease) in borrowings under lines of credit and commercial paper program	424,396	(196,549)	(85,815)
Net proceeds from (payments on) other debt	5,334	82	(2,986)
Debt financing costs	(114,823)	(12,751)	(29,659)
Dividends paid	(80,748)	(63,373)	(54,969)
Issuance of common stock under incentive plans	2,316	1,764	84
Contribution from noncontrolling interest		891
Cash provided by (used in) financing activities	2,899,230	(275,563)	737,891
Increase (decrease) in cash and cash equivalents	44,556	32,455	(9,511)
Cash and cash equivalents, beginning of year	93,593	61,138	70,649
Cash and cash equivalents, end of year	138,149	93,593	61,138
SUPPLEMENTAL CASH FLOW INFORMATION:
Cash paid during the year for interest	213,697	134,866	76,801
Cash paid during the year for income taxes	$ 7,094	$ 36,765	$ 17,482

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Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Current assets:
Cash and cash equivalents	$ 138,149	$ 93,593
Restricted cash	10,322
Trade accounts receivable	380,595	208,060
Other receivables	88,584	44,260
Inventories	377,490	235,616
Prepaid royalties	21,944	33,932
Deferred income taxes	42,051
Coal derivative assets	13,335	15,191
Other	110,304	104,262
Total current assets	1,182,774	734,914
Property, plant and equipment:
Coal lands and mineral rights	6,578,430	2,523,172
Plant and equipment	3,225,985	2,397,444
Deferred mine development	1,064,279	872,329
Property, plant and equipment	10,868,694	5,792,945
Less accumulated depreciation, depletion and amortization	(2,919,544)	(2,484,053)
Property, plant and equipment, net	7,949,150	3,308,892
Other assets:
Prepaid royalties	86,626	66,525
Goodwill	596,103	114,963
Deferred income taxes	(976,753)	361,556
Equity investments	225,605	177,451
Other	173,701	116,468
Total other assets	1,082,035	836,963
Total assets	10,213,959	4,880,769
Current liabilities:
Accounts payable	383,782	198,216
Coal derivative liabilities	7,828	4,947
Deferred income taxes	(42,051)	7,775
Accrued expenses and other current liabilities	348,207	245,411
Current maturities of debt and short-term borrowings	280,851	70,997
Total current liabilities	1,020,668	527,346
Long-term debt	3,762,297	1,538,744
Asset retirement obligations	446,784	334,257
Accrued pension benefits	48,244	49,154
Accrued postretirement benefits other than pension	42,309	37,793
Accrued workers' compensation	71,948	35,290
Deferred income taxes	976,753
Other noncurrent liabilities	255,382	110,234
Total liabilities	6,624,385	2,632,818
Redeemable noncontrolling interest	11,534	10,444
Stockholders' equity:
Common stock, $0.01 par value, authorized 260,000 shares, issued 213,183 and 164,117 shares at December 31, 2011 and 2010, respectively	2,136	1,645
Paid-in capital	3,015,349	1,734,709
Treasury stock, 1,512 shares at December 31, 2011 and 2010, at cost	(53,848)	(53,848)
Retained earnings	622,353	561,418
Accumulated other comprehensive loss	(7,950)	(6,417)
Total stockholders' equity	3,578,040	2,237,507
Total liabilities and stockholders' equity	$ 10,213,959	$ 4,880,769

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Derivative Instruments

12 Months Ended

Dec. 31, 2011

Derivative Instruments [Abstract]

Derivative Instruments

10.  Derivative Instruments

Diesel fuel price risk management

The Company is exposed to price risk with respect to diesel fuel purchased for use in its operations. The Company anticipates purchasing approximately 80 to 90 million gallons of diesel fuel for use in its operations during 2012. To reduce the volatility in the price of diesel fuel for its operations, the Company uses forward physical diesel purchase contracts, as well as heating oil swaps and purchased call options. At December 31, 2011, the Company had protected the price of approximately 82% of its expected purchases for fiscal year 2012.

At December 31 2011, the Company held heating oil swaps and purchased call options for approximately 69 million gallons for the purpose of managing the price risk associated with future diesel purchases. Since the changes in the price of heating oil highly correlate to changes in the price of the hedged diesel fuel purchases, the heating oil swaps and purchased call options qualify for cash flow hedge accounting.

The Company also purchased heating oil call options to hedge the fuel surcharges on its barge and rail shipments that cover increases in diesel fuel prices. These positions reduce the Company's risk of cash flow fluctuations related to these surcharges but the positions are not accounted for as hedges. At December 31, 2011, Company held purchased call options for approximately 19.1 million gallons for the purpose of managing the fluctuations in cash flows associated with fuel surcharges on future shipments.

Coal risk management positions

The Company may sell or purchase forward contracts, swaps and options in the over-the-counter coal market in order to manage its exposure to coal prices. The Company has exposure to the risk of fluctuating coal prices related to forecasted sales or purchases of coal or to the risk of changes in the fair value of a fixed price physical sales contract. Certain derivative contracts may be designated as hedges of these risks.

At December 31, 2011, the Company held derivatives for risk management purposes that are expected to settle in the following years :

	2012	2013	2014	2015
(Tons in thousands)
Coal sales	2,416	1,117	1,440	720
Coal purchases	254	—	—	—

Coal trading positions

The Company may sell or purchase forward contracts, swaps and options in the over-the-counter coal market for trading purposes. The Company is exposed to the risk of changes in coal prices on the value of its coal trading portfolio. The estimated future realization of the value of the trading portfolio is $2.6 million of losses in 2012 and $1.8 million of losses in 2013.

Tabular derivatives disclosures

The Company's contracts with certain of its counterparties allow for the settlement of contracts in an asset position with contracts in a liability position in the event of default or termination. Such netting arrangements reduce the Company's credit exposure related to these counterparties. For classification purposes, the Company records the net fair value of all the positions with a given counterparty as a net asset or liability in the consolidated balance sheets. The amounts shown in the table below represent the fair value position of individual contracts, regardless of the net position presented in the accompanying consolidated balance sheets. The fair value and location of derivatives reflected in the accompanying consolidated balance sheets are as follows:

Fair Value of Derivatives

(In thousands)

	December 31, 2011								December 31, 2010
	Asset Derivative			Liability Derivative					Asset Derivative			Liability Derivative
Derivatives Designated as Hedging Instruments
Heating oil – diesel purchases	$	8,997		$	—				$	13,475		$	—
Coal	1,109			—					2,009			(2,350		)
Total	10,106			—					15,484			(2,350		)
Derivatives Not Designated as Hedging Instruments
Heating oil  – fuel surcharges	1,797			—					—			—
Coal — held for trading purposes	15,505			(19,927		)			34,445			(24,087		)
Coal	14,855			(6,035		)			1,139			(912		)
Total	32,157			(25,962		)			35,584			(24,999		)
Total derivatives	42,263			(25,962		)			51,068			(27,349		)
Effect of counterparty netting	(18,134		)	18,134					(22,402		)	22,402
Net derivatives as classified in the balance sheets	$	24,129		$	(7,828	)	$	16,301	$	28,666		$	(4,947	)	$	23,719

Net derivatives as reflected on the balance sheets

		December 31, 2011			December 31, 2010
Heating oil	Other current assets	$	10,794		$	13,475
Coal	Coal derivative assets	13,335			15,191
	Coal derivative liabilities	(7,828		)	(4,947		)
		$	16,301		$	23,719

The Company had a current asset for the right to reclaim cash collateral of $12.4 million and $10.3 million at December 31, 2011 and December 31, 2010, respectively. These amounts are not included with the derivatives presented in the table above and are included in "other current assets" in the accompanying consolidated balance sheets.

The effects of derivatives on measures of financial performance are as follows:

Year Ended December 31,

(In thousands)

Derivatives used in Fair Value Hedging	Gain on Derivatives Used in						Hedged Items in Fair Value Hedge	Loss on Hedged Items In Fair Value
Relationships	Fair Value Hedge Relationships						Relationships	Hedge Relationships
	2011		2010		2009			2011		2010		2009
	(In thousands)							(In thousands)
Coal	$        —	(3)	$     —	(3)	$      2,586	(3)	Firm commitments	$                      —	(3)	$     —	(3)	$  (2,586)	(3)

Derivatives used inCash Flow Hedging	Gain (Loss) Recognized in OCI (Effective Portion)										Gains (Losses) Reclassified from OCI into Income (Effective Portion)
Relationships	2011			2010			2009			2011				2010			2009
Heating oil – diesel purchases	$	1,294		$	(149	)	$	10,309		$		14,866	(2)	$	437	(2)	$	(49,055	)	(2)
Coal sales	4,923			(4,714		)	(7,441		)	1,572			(1)	(1,602)		(1)	(6,999		)	(1)
Coal purchases	(2,009		)	5,145			1,089			—			(2)	(1,202)		(2)	(13,181		)	(2)
Totals	$	4,208		$	282		$	3,957		$		16,438		$	(2,367	)	$	(69,235)

Derivatives used inCash Flow Hedging	Gain (Loss) Recognized in Income (Ineffective Portion and Amount Excluded from Effectiveness Testing)
Relationships	2011		2010		2009
Heating oil – diesel purchases	$	—	$	—	$                —
Coal sales	—		—		—
Coal purchases	—		—		—
Totals	$	—	$	—	$	—

Derivatives Not Designated as	Gain (Loss)
Hedging Instruments	2011			2010			2009
Coal — unrealized	$	6,438	(3)	$	(10,991)	(3)	$           9,673	(3)
Coal — realized	$	(7)	(4)	$	4,542	(4)	$                 —	(4)
Heating oil — fuel surcharges — unrealized	$	(2,906)	(4)	$	—	(4)	$                 —	(4)

Location in Statement of Income:

(1)Revenues

(2)Cost of sales

(3)Change in fair value of coal derivatives and coal trading activities, net

(4)Other operating income, net

The Company recognized net unrealized and realized losses of $3.5 million during the year ended December 31, 2011 and net unrealized and realized gains of $2.1 million and $2.4 million, during the years ended December 31, 2010 and 2009, respectively, related to its trading portfolio (including derivative and non-derivative contracts). These balances are included in the caption "Change in fair value of coal derivatives and coal trading activities, net" in the accompanying consolidated statements of income and are not included in the previous table.

During the next twelve months, based on fair values at December 31, 2011, gains on derivative contracts designated as hedge instruments in cash flow hedges of approximately $9.2 million are expected to be reclassified from other comprehensive income into earnings.

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Stock Based Compensation And Other Incentive Plans (Schedule Of Stock Option Activity Under Incentive Plan) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Stock Based Compensation And Other Incentive Plans [Abstract]
Options outstanding at January 1	4,544
Granted, Common Shares	728
Exercised, Common Shares	(199)	(155)	(13)
Cancelled, Common Shares	(88)
Expired, Common Shares	(32)
Options outstanding at December 31	4,953	4,544
Options exercisable at December 31	3,157
Options outstanding at January 1, Weighted Average Exercise Price	$ 25.18
Granted, Weighted Average Exercise Price	$ 32.18
Exercised, Weighted Average Exercise Price	$ 11.61
Cancelled, Weighted Average Exercise Price	$ 23.74
Expired, Weighted Average Exercise Price	$ 52.69
Options outstanding at December 31, Weighted Average Exercise Price	$ 26.60	$ 25.18
Options exercisable at December 31, Weighted Average Exercise Price	$ 27.59
Options outstanding at December 31, Aggregate Intrinsic Value	$ 4,107
Options exercisable at December 31, Aggregate Intrinsic Value	$ 3,887
Options outstanding at December 31, Average Contract Life	5.76
Options exercisable at December 31 , Average Contract Life	4.35

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Accrued Workers' Compensation (Schedule Of Amounts Recognized In Balance Sheet) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Accrued Workers Compensation [Line Items]
Less amount included in accrued expenses	$ 11,666,000	$ 6,659,000
Noncurrent obligations	71,948,000	35,290,000
Workers' Compensation [Member]
Accrued Workers Compensation [Line Items]
Occupational disease costs	29,430,000	24,537,000
Total obligations	83,614,000	41,949,000
Less amount included in accrued expenses	11,666,000	6,659,000
Noncurrent obligations	71,948,000	35,290,000
Surety bonds and letters of credit outstanding	60,100,000
Occupational Disease [Member]
Accrued Workers Compensation [Line Items]
Occupational disease costs	$ 54,184,000	$ 17,412,000

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Accrued Workers' Compensation (Schedule Of Changes in Projected Benefit Obligations) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Accrued Workers Compensation [Line Items]
Accumulated gain (loss)	$ (5,500,000)	$ 2,000,000
Workers' Compensation [Member]
Accrued Workers Compensation [Line Items]
Benefit obligations at January 1	17,412,000	9,702,000
Service cost	2,059,000	727,000	531,000
Interest cost	1,799,000	675,000	558,000
Actuarial loss	7,081,000	6,993,000
Benefit and administrative payments	(1,097,000)	(685,000)
Acquisition of ICG	26,930,000
Benefit obligations at December 31	54,184,000	17,412,000	9,702,000
Amortization of net gains (losses)	$ 1,100,000

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Document And Entity Information (USD $) In Billions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Feb. 15, 2012	Jun. 30, 2011
Document And Entity Information [Abstract]
Entity Registrant Name	ARCH COAL INC
Entity Central Index Key	0001037676
Document Type	10-K
Document Period End Date	Dec. 31, 2011
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	FY
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 5.6
Entity Common Stock, Shares Outstanding		213,292,678

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Accrued Expenses And Other Current Liabilities

12 Months Ended

Dec. 31, 2011

Accrued Expenses And Other Current Liabilities [Abstract]

Accrued Expenses And Other Current Liabilities

11.  Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consist of the following:

		December 31
	2011		2010
		(In thousands)
Payroll and employee benefits	$	65,323	$	51,327
Taxes other than income taxes		133,331		107,969
Interest		55,266		52,843
Acquired sales contracts (see Note 6)		38,441		5,615
Workers' compensation (see Note 15)		11,666		6,659
Asset retirement obligations (see Note 14)		27,119		8,862
Other		17,061		12,136
	$	348,207	$	245,411

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Accrued Expenses And Other Current Liabilities (Accrued Expenses And Other Current Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Accrued Expenses And Other Current Liabilities [Abstract]
Payroll and employee benefits	$ 65,323	$ 51,327
Taxes other than income taxes	133,331	107,969
Interest	55,266	52,843
Coal Supply Agreement Liability	38,441	5,615
Workers' compensation	11,666	6,659
Asset retirement obligations	27,119	8,862
Other	17,061	12,136
Accrued expenses and other current liabilities, total	$ 348,207	$ 245,411

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Accrued Workers' Compensation (Worker's Compensation Expense) (Details) (Workers' Compensation [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Workers' Compensation [Member]
Accrued Workers Compensation [Line Items]
Service cost	$ 2,059	$ 727	$ 531
Interest cost	1,799	675	558
Net amortization	(493)	(1,860)	(2,879)
Total occupational disease	3,365	(458)	(1,790)
Traumatic injury claims and assessments	16,979	9,263	8,904
Total workers' compensation expense	$ 20,344	$ 8,805	$ 7,114

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Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Stockholders' equity:
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	260,000	260,000
Additional common stock, shares issued	213,183	164,117
Treasury stock, shares	1,512	1,512

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Debt And Financing Arrangements

12 Months Ended

Dec. 31, 2011

Debt And Financing Arrangements [Abstract]

Debt And Financing Arrangements

5.  Debt and Financing Arrangements

Debt consists of the following:

		December 31,
		2011			2010
		(In thousands)
Commercial paper	$		—	$		56,904
Indebtedness to banks under credit facilities			481,300			—
6.75% senior notes ($450.0 million face value) due July 1, 2013			450,971			451,618
8.75% senior notes ($600.0 million face value) due August 1, 2016			588,974			587,126
7.00% senior notes due June 15, 2019 at par			1,000,000			—
7.25% senior notes due October 1, 2020 at par			500,000			500,000
7.25% senior notes due June 15, 2021 at par			1,000,000			—
Other			21,903			14,093
			4,043,148			1,609,741
Less current maturities of debt and short-term borrowings			280,851			70,997
Long-term debt	$		3,762,297	$		1,538,744

The current maturities of debt include contractual maturities, as well as amounts borrowed that are supported by credit facilities that have a term of less than one year and amounts borrowed under credit facilities with terms longer than one year that the Company does not intend to refinance on a long-term basis, based on cash projections and management's plans.

ICG Debt

Upon the closing of the ICG acquisition, the Company gave a 30-day redemption notice to the Trustee of ICG's 9.125% senior notes and legally discharged its obligation under the 9.125% senior notes by depositing $260.7 million with the Trustee to redeem the debt. On July 14, 2011, all of the outstanding 9.125% senior notes were redeemed at an aggregate price of $251.4 million, including the required make-whole premium, plus accrued interest of $5.2 million, and the remainder of the deposit was returned to the Company.

At the acquisition date, ICG's 4.00% convertible senior notes with a fair value of $298.5 million and 9.00% convertible senior notes with a fair value of $1.7 million ("convertible notes") became convertible into cash, pursuant to the amended indentures governing the convertible notes, at a calculated conversion rate of $2,614.6848 for each $1,000 in principal amount surrendered for conversion for the 4.00% convertible notes and $2,392.73414 for the 9.00% convertible notes for conversions occurring prior to August 17, 2011.

At the acquisition date, other ICG debt had a fair value of approximately $54.0 million and consisted mainly of equipment notes and insurance notes payable.

The Company recognized a net loss of $2.0 million during the year ended December 31, 2011 on the early extinguishment of ICG's debt, including the conversions of the 4.00% and 9.00% convertible notes described above. The remaining amounts outstanding under the convertible notes and other ICG debt is included in "other" in the debt table above.

Credit Facilities

On June 14, 2011, the Company amended and restated its secured credit facility to allow for up to $2.0 billion in borrowings. The Company paid and deferred $21.1 million in financing fees related to the amendment of this agreement. Borrowings under this credit facility bear interest at a floating rate based on LIBOR determined by reference to the Company's leverage ratio, as calculated in accordance with the credit agreement. The credit facility has a five-year term that expires on June 14, 2016 and is secured by substantially all of the Company's assets as well as its ownership interests in substantially all of its subsidiaries, excluding its ownership interests in Arch Western and its subsidiaries. Commitment fees of 0.50% per annum are payable on the average unused daily balance of the revolving credit facility. The weighted-average interest rate of the Company's outstanding borrowings under the credit facility was 3.04% at December 31, 2011. Financial covenant requirements may restrict the amount of unused capacity available to the Company for borrowings and letters of credit.

The Company maintains an accounts receivable securitization program under which eligible trade receivables are sold, without recourse, to a multi-seller, asset-backed commercial paper conduit. The entity through which these receivables are sold is consolidated into the Company's financial statements. The Company may borrow and draw letters of credit against the facility, and pays facility fees, program fees and letter of credit fees (based on amounts of outstanding letters of credit) at rates that vary with its leverage ratio, as defined under the program. The Company entered into an amendment to its accounts receivable program in November of 2011 to increase the eligible receivables pool, as defined by the agreement, to include receivables generated from the acquired ICG subsidiaries. On December 13, 2011, the Company entered into another amendment to its accounts receivable securitization program to increase the size of the program to allow for aggregate borrowings and letters of credit of up to $250.0 million from $175.0 million. The total aggregate borrowings and letters of credit are limited by eligible accounts receivable, as defined under the terms of the agreement. The credit facility supporting the borrowings under the program is subject to renewal annually, and expires on December 11, 2012. The interest rate in effect as of December 31, 2011 was 0.73%.

On June 14, 2011, the Company terminated its commercial paper placement program and the supporting credit facility.

The Company's average borrowing level under these programs was approximately $234.2 million and $132.0 million for the years ended December 31, 2011 and 2010, respectively.

Availability

As of December 31, 2011, the Company had $375.0 million of borrowings outstanding under the amended and restated secured credit facility and $106.3 million of borrowings outstanding under its accounts receivable securitization program.  The Company also had $146.6 million of outstanding letters of credit at December 31, 2011.  As of December 31, 2011, the Company had availability of approximately $901.4 million under all lines of credit, as limited by customary financial covenants that may limit the Company's total debt based on defined earnings measurements.  

2013 Senior Notes

The 6.75% senior notes due in 2013 ("2013 Notes") were issued by the Company's subsidiary, Arch Western Finance LLC ("Arch Western Finance"), under an indenture dated June 25, 2003. The Company redeemed $500.0 million aggregate principal amount of the 2013 Notes on September 8, 2010.  The Company recongized a loss on the redemption of $6.8 million, including the payment of the $5.6 million redeption premium and the write-off of $3.3 million of unamortized debt financing costs, partially off set by the write-off of $2.1 million of the orgional issue premium.  The senior notes are guaranteed by Arch Western and certain of its subsidiaries and are secured by an intercompany notes from Arch Coal, Inc. to Arch Western. The terms of the senior notes contain restrictive covenants that limit Arch Western's ability to, among other things, incur additional debt, sell or transfer assets, and make certain investments. Of the aggregate principal outstanding at December 31, 2011 and 2010, $118.4 million of the 2013 Notes were issued at a premium of 104.75% of par. The premium is amortized over the term of the notes. Interest is payable on the notes on January 1 and July 1 of each year. The notes are redeemable at any time at their face value.

2016 Senior Notes

On July 31, 2009, the Company issued $600.0 million in aggregate principal amount of 8.75% senior unsecured notes due 2016 ("2016 Notes") at an initial issue price of 97.464% of the face amount. The Company incurred issue costs of $14.5 million in association with the 2016 Notes. Interest is payable on the notes on February 1 and August 1 of each year. At any time on or after August 1, 2013, the Company may redeem some or all of the notes. The redemption price, reflected as a percentage of the principal amount, is: 104.375% for notes redeemed between August 1, 2013 and July 31, 2014; 102.188% for notes redeemed between August 1, 2014 and July 31, 2015; and 100% for notes redeemed on or after August 1, 2015. In addition, at any time and on one or more occasions prior to August 1, 2012, the Company may redeem an aggregate principal amount of senior notes not to exceed 35% of the original aggregate principal amount of the senior notes outstanding with the proceeds of one or more public equity offerings, at a redemption price equal to 108.750%.

2020 Senior Notes

     On August 9, 2010, we issued $500.0 million in aggregate principal amount of 7.25% senior unsecured notes due in 2020 ("2020 Notes") at par.  Interest is payable on the 2020 Notes on April 1 and October 1 of each year.  At any time on or after October 1, 2015, the Company may redeem some or all of the notes. The redemption price reflected as a percentage of the principal amount is: 103.625% for notes redeemed between October 1, 2015 and September 30, 2016; 102.417% for notes redeemed between October 1, 2016 and September 30, 2017; 101.208% for notes redeemed between October 1, 2017 and September 30, 2018; and 100% for notes redeemed on or after October 1, 2018. In addition, at any time and on one or more occasions prior to October 1, 2013, the Company may redeem an aggregate principal amount of senior notes not to exceed 35% of the original aggregate principal amount of the senior notes outstanding with the proceeds of one or more public equity offerings, at a redemption price equal to 107.250%.

2019 and 2021 Senior Notes

On June 14, 2011, the Company entered into an indenture in conjunction with the issuance of the 7.00% unsecured senior notes due 2019 ("2019 Notes") and the 7.25% unsecured senior notes due 2021 ("2021 Notes") as discussed in Note 3, "Business Combinations." Interest is payable on the 2019 Notes and 2021 Notes on June 15 and December 15 of each year.

At any time prior to June 15, 2014, the Company may redeem up to 35% of the original aggregate principal amount of each of the 2019 Notes and 2021 Notes, plus accrued and unpaid interest, with the net proceeds from certain equity offerings, at a redemption price, reflected as a percentage of the principal amount, equal to 107.0% and 107.25%, respectively. The Company may redeem the 2019 Notes prior to June 15, 2015 and the 2021 Notes prior to June 15, 2016 at the respective make-whole prices set forth in the indenture. On or after June 15, 2015, the Company may redeem the 2019 Notes for cash at redemption prices, reflected as a percentage of the principal amount, of: 103.5% from June 15, 2015 through June 14, 2016; 101.75% from June 15, 2016 through June 14, 2017; and 100% beginning on June 15, 2017. On or after June 15, 2016, the Company may redeem the 2021 Notes for cash at redemption prices, reflected as a percentage of the principal amount, of: 103.625% from June 15, 2016 through June 14, 2017; 102.417% from June 15, 2017 through June 14, 2018; 101.208% from June 15, 2018 through June 14, 2019 and 100% beginning on June 15, 2019. In each case, accrued and unpaid interest at the redemption date is due upon redemption. Upon a change in control, the Company is required to make a tender offer for both series of notes at a price of 101% of the principal amount. The Company incurred issue costs of $44.2 million related to the issuance of these notes.

The Company and the guarantor subsidiaries entered into a registration rights agreement (the "Registration Rights Agreement") in connection with the issuance and sale of the 2019 Notes and 2021 Notes. Pursuant to the Registration Rights Agreement, the Company and the guarantor subsidiaries agreed to file a registration statement with the Securities and Exchange Commission to register an exchange offer pursuant to which the Company will offer to exchange a like aggregate principal amount of senior notes identical in all material respects to the 2019 Notes and 2021 Notes, except for terms relating to additional interest and transfer restrictions, for any or all of the outstanding 2019 Notes and 2021 Notes. Pursuant to the Registration Rights Agreement, the Company must use commercially reasonable efforts to cause the registration statement to become effective as soon as practicable and to complete the exchange offer no later than June 13, 2012. Should those events not occur within the specified time frame, the applicable interest rates on the 2019 Notes and the 2021 Notes shall be increased by one-quarter of one percent per annum for the first 90 days following the occurrence of such failure. Such interest rate will increase by an additional one-quarter of one percent per annum thereafter at the end of each subsequent 90-day period up to a maximum aggregate increase of one percent per annum. Once any of the required events occur, the interest rates will revert to the rate specified in the indenture governing the 2019 Notes and 2021 Notes.

The 2016, the 2020, the 2019 and the 2021 unsecured senior notes are guaranteed by substantially all of the Company's subsidiaries, including the newly acquired subsidiaries of ICG and excluding Arch Western, its subsidiaries and Arch Receivable Company, LLC and the Company's subsidiaries outside the U.S.

Expected aggregate maturities of debt for the next five years are $280.9 million in 2012, $672.4 in 2013, $0 in 2014, $0 in 2015 and $600.0 million in 2016.

Terms of the Company's credit facilities and leases contain financial and other covenants that limit the ability of the Company to, among other things, acquire, dispose, merge or consolidate assets; incur additional debt; pay dividends and make distributions or repurchase stock; make investments; create liens; issue and sell capital stock of subsidiaries; enter into restrictions affecting the ability of restricted subsidiaries to make distributions, loans or advances to the Company; engage in transactions with affiliates and enter into sale and leaseback transactions. The terms also require the Company to, among other things, maintain various financial ratios and comply with various other financial covenants, including an interest coverage ratio test, as defined in the indentures. In addition, the covenants require the Company to pledge assets to collateralize the revolving credit facility. The assets pledged include equity interests in wholly-owned subsidiaries, certain real property interests, accounts receivable and inventory of the Company. Failure by the Company to comply with such covenants could result in an event of default, which, if not cured or waived, could have a material adverse effect on the Company. The Company complied with all financial covenants at December 31, 2011.

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Goodwill

12 Months Ended

Dec. 31, 2011

Goodwill [Abstract]

Goodwill

4.  Goodwill

Changes in the carrying value of goodwill for the years ended December 31, 2011, 2010 and 2009 are as follows:

		(In thousands)
Balance at January 1, 2009	$	46,832
Consideration paid related to prior business acquisitions		4,767
Acquisition of Jacobs Ranch		62,102
Balance at December 31, 2009		113,701
Consideration paid related to prior business acquisitions		1,262
Balance at December 31, 2010		114,963
Consideration paid related to prior business acquisitions		829
Acquisition of ICG		480,311
Balance at December 31, 2011	$	596,103

Goodwill of $115.8 million has been allocated to the Company's Powder River Basin segment and goodwill of $480.3 million has allocated to the Company's Appalachia segment, for impairment testing purposes. The goodwill related to the acquisition of ICG is not expected to be deductible for income tax purposes; however, the remaining goodwill is expected to be deductible. The consideration paid related to prior business acquisitions represents ongoing adjustments to the purchase price of a previous acquisition resulting from a 2008 tax settlement.

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Employee Benefit Plans

12 Months Ended

Dec. 31, 2011

Employee Benefit Plans [Abstract]

Employee Benefit Plans

16.  Employee Benefit Plans

Defined Benefit Pension and Other Postretirement Benefit Plans

The Company provides funded and unfunded non-contributory defined benefit pension plans covering certain of its salaried and hourly employees. Benefits are generally based on the employee's age and compensation. The Company funds the plans in an amount not less than the minimum statutory funding requirements or more than the maximum amount that can be deducted for U.S. federal income tax purposes.

The Company also currently provides certain postretirement medical and life insurance coverage for eligible employees. Generally, covered employees who terminate employment after meeting eligibility requirements are eligible for postretirement coverage for themselves and their dependents. The salaried employee postretirement benefit plans are contributory, with retiree contributions adjusted annually, and contain other cost-sharing features such as deductibles and coinsurance. The Company's current funding policy is to fund the cost of all postretirement benefits as they are paid.

Employees acquired with the ICG acquisition were brought over in their existing plan. Subsequently, the terms of the plan were amended to change vesting periods, coverage caps, and eligible ages, resulting in a reduction of the benefit obligation of $55.5 million.

During 2009, the Company notified participants of the retiree medical plan of a plan change increasing the retirees' responsibility for medical costs. This change resulted in a remeasurement of the postretirement benefit obligation, which included a decrease in the discount rate from 6.85% to 5.68%. The remeasurement resulted in a decrease in the liability of $21.0 million, with a corresponding increase to other comprehensive income, and will result in future reductions in costs under the plan.

Obligations and Funded Status.  Summaries of the changes in the benefit obligations, plan assets and funded status of the plans are as follows:

	Pension Benefits		Other Postretirement                Benefits
	2011	2010	2011	2010
	(In thousands)
CHANGE IN BENEFIT OBLIGATIONS
Benefit obligations at January 1	$  297,707	$  280,693	$    39,633	$    46,445
Service cost	16,490	15,870	3,917	1,509
Interest cost	16,253	15,822	3,279	2,083
Plan amendments	(3,235)	(92)	(55,542)	—
Benefits paid	(18,848)	(15,924)	(1,669)	(1,845)
Acquisition of ICG	—	—	48,441	—
Other-primarily actuarial loss (gain)	25,584	1,338	7,070	(8,559)
Benefit obligations at December 31	$  333,951	$  297,707	$    45,129	$    39,633
CHANGE IN PLAN ASSETS
Value of plan assets at January 1	$  247,713	$  211,899	$            —	$            —
Actual return on plan assets	9,443	34,401	—	—
Employer contributions	46,766	17,337	1,669	1,845
Benefits paid	(18,848)	(15,924)	(1,669)	(1,845)
Value of plan assets at December 31	$  285,074	$  247,713	$            —	$            —
Accrued benefit cost	$   (48,877)	$   (49,994)	$   (45,129)	$   (39,633)
ITEMS NOT YET RECOGNIZED AS A COMPONENT OF NET PERIODIC BENEFIT COST
Prior service credit (cost)	$       1,736	$      (1,310)	$    62,920	$      9,742
Accumulated gain (loss)	(68,302)	(39,099)	1,795	11,965
	$   (66,566)	$   (40,409)	$    64,715	$    21,707
BALANCE SHEET AMOUNTS
Current liability	$         (633)	$         (840)	$     (2,820)	$     (1,840)
Noncurrent liability	$   (48,244)	$   (49,154)	$   (42,309)	$   (37,793)
	$   (48,877)	$   (49,994)	$   (45,129)	$   (39,633)

Pension Benefits

The accumulated benefit obligation for all pension plans was $314.7 million and $280.4 million at December 31, 2011 and 2010, respectively. The accumulated benefit obligation differs from the benefit obligation in that it includes no assumption about future compensation levels.

The benefit obligation and the accumulated benefit obligation for the Company's unfunded pension plan were $8.2 million and $7.1 million, respectively, at December 31, 2011.

The prior service credit and net loss that will be amortized from accumulated other comprehensive income into net periodic benefit cost in 2012 are $0.1 million and $14.3 million, respectively.

Other Postretirement Benefits

The prior service credit and net gain that will be amortized from accumulated other comprehensive income into net periodic benefit cost in 2012 is $12.0 million and $0.4 million, respectively.

Components of Net Periodic Benefit Cost.  The following table details the components of pension and other postretirement benefit costs.

	Pension Benefits			Other Postretirement Benefits
Year Ended December 31,	2011	2010	2009	2011	2010	2009
	(In thousands)
Service cost	$    16,490	$    15,870	$    13,444	$    3,917	$    1,509	$    2,954
Interest cost	16,253	15,822	15,946	3,279	2,083	3,667
Expected return on plan assets*	(21,812)	(19,392)	(17,719)	—	—	—
Amortization of prior service cost (credit)	(189)	173	193	(2,364)	(2,364)	2,161
Amortization of other actuarial losses (gains)	8,748	7,130	3,967	(3,100)	(2,918)	(2,897)
Curtailments	—	—	585	—	—	—
Net benefit cost	$    19,490	$    19,603	$    16,416	$    1,732	$   (1,690)	$    5,885

____________

* The Company does not fund its other postretirement benefit obligations.

The differences generated from changes in assumed discount rates and returns on plan assets are amortized into earnings over a five-year period.

Assumptions.  The following table provides the assumptions used to determine the actuarial present value of projected benefit obligations at December 31.

	Pension        Benefits		Other Postretirement        Benefits
	2011	2010	2011	2010
Weighted average assumptions:
Discount rate	4.91%	5.71%	4.52%	5.23%
Rate of compensation increase	3.39%	3.39%	N/A	N/A

The following table provides the assumptions used to determine net periodic benefit cost for years ended December 31.

	Pension Benefits			Other Postretirement Benefits
	2011	2010	2009	2011	2010	2009
Weighted average assumptions:
Discount rate	5.71%	5.97%	6.85%	5.23%	5.67%	6.85%/5.68%
Rate of compensation increase	3.39%	3.39%	3.39%	N/A	N/A	N/A
Expected return on plan assets	8.50%	8.50%	8.50%	N/A	N/A	N/A

The Company establishes the expected long-term rate of return at the beginning of each fiscal year based upon historical returns and projected returns on the underlying mix of invested assets. The Company utilizes modern portfolio theory modeling techniques in the development of its return assumptions. This technique projects rates of return that can be generated through various asset allocations that lie within the risk tolerance set forth by members of the Company's pension committee (the "Pension Committee"). The risk assessment provides a link between a pension's risk capacity, management's willingness to accept investment risk and the asset allocation process, which ultimately leads to the return generated by the invested assets.

The health care cost trend rate assumed for 2012 is 7.7% and is expected to reach an ultimate trend rate of 4.5% by 2028. A one-percentage-point increase in the health care cost trend rate would have increased the postretirement benefit obligation at December 31, 2011 by $0.5 million. A one-percentage-point decrease in the health care cost trend rate would have decreased the postretirement benefit obligation at December 31, 2011 by $0.4 million. The effect of these changes would have had an insignificant impact on the net periodic postretirement benefit costs.

Plan Assets

The Pension Committee is responsible for overseeing the investment of pension plan assets. The Pension Committee is responsible for determining and monitoring appropriate asset allocations and for selecting or replacing investment managers, trustees and custodians. The pension plan's current investment targets are 65% equity, 30% fixed income securities and 5% cash. The Pension Committee reviews the actual asset allocation in light of these targets on a periodic basis and rebalances among investments as necessary. The Pension Committee evaluates the performance of investment managers as compared to the performance of specified benchmarks and peers and monitors the investment managers to ensure adherence to their stated investment style and to the plan's investment guidelines.

The Company's pension plan assets at December 31, 2011 and 2010, respectively, are categorized below according to the fair value hierarchy as defined in Note 13, "Fair Values of Financial Instruments":

	Total		Level 1				Level 2		Level 3
	2011	2010		2011	2010	2011		2010		2011	2010
	(In thousands)
Equity securities:(A)
U.S. small-cap	$11,178	$10,647		$11,178	$10,647	$ —		$ —		$ —	$ —
U.S. mid-cap	50,264	46,851		23,474	21,163	26,790		25,688		—	—
U.S. large-cap	91,561	77,632		44,820	38,397	46,741		39,235		—	—
Non-U.S.	22,509	24,995		—	—	22,509		24,995		—	—
Fixed income securities:
U.S. government securities(B)	13,454	3,053		12,738	2,492	716		561		—	—
Non-U.S. government securities(C)	2,968	3,469		—	—	2,968		3,469		—	—
U.S. government asset and mortgage backed securities(D)	800	1,073		—	—	800		1,073		—	—
Corporate fixed income(E)	14,004	13,737		—	—	14,004		13,737		—	—
State and local government securities(F)	18,416	13,679		—	—	18,416		13,679		—	—
Other fixed income(G)	51,470	45,628		—	—	51,470		45,628		—	—
Short-term investments(H)	8,029	6,110		—	—	8,029		6,110		—	—
Other investments(I)	421	839		—	—	421		839		—	—
Total	$285,074	$247,713		$92,210	$72,699	$192,864		$175,014		$ —	$ —

____________

(A)	Equity securities includes investments in 1) common stock, 2) preferred stock and 3) mutual funds. Investments in common and preferred stocks are valued using quoted market prices multiplied by the number of shares owned. Investments in mutual funds are valued at the net asset value per share multiplied by the number of shares held as of the measurement date and are traded on listed exchanges.
(B)	U.S. government securities includes agency and treasury debt. These investments are valued using dealer quotes in an active market.
(C)	Non-U.S. government securities includes debt securities issued by foreign governments and are valued utilizing a price spread basis valuation technique with observable sources from investment dealers and research vendors.
(D)	U.S. government asset and mortgage backed securities includes government-backed mortgage funds which are valued utilizing an income approach that includes various valuation techniques and sources such as discounted cash flows models, benchmark yields and securities, reported trades, issuer trades and/or other applicable data.
(E)	Corporate fixed income is primarily comprised of corporate bonds and certain corporate asset-backed securities that are denominated in the U.S. dollar and are investment-grade securities. These investments are valued using dealer quotes.
(F)	State and local government securities include different U.S. state and local municipal bonds and asset backed securities, these investments are valued utilizing a market approach that includes various valuation techniques and sources such as value generation models, broker quotes, benchmark yields and securities, reported trades, issuer trades and/or other applicable data.
(G)	Other fixed income investments are actively managed fixed income vehicles that are valued at the net asset value per share multiplied by the number of shares held as of the measurement date.
(H)	Short-term investments include governmental agency funds, government repurchase agreements, commingled funds, and pooled funds and mutual funds. Governmental agency funds are valued utilizing an option adjusted spread valuation technique and sources such as interest rate generation processes, benchmark yields and broker quotes. Investments in governmental repurchase agreements, commingled funds and pooled funds and mutual funds are valued at the net asset value per share multiplied by the number of shares held as of the measurement date.
(I)	Other investments includes cash, forward contracts, derivative instruments, credit default swaps, interest rate swaps and mutual funds. Investments in interest rate swaps are valued utilizing a market approach that includes various valuation techniques and sources such as value generation models, broker quotes in active and non-active markets, benchmark yields and securities, reported trades, issuer trades and/or other applicable data. Forward contracts and derivative instruments are valued at their exchange listed price or broker quote in an active market. The mutual funds are valued at the net asset value per share multiplied by the number of shares held as of the measurement date and are traded on listed exchanges.

Cash Flows.  In order to achieve a desired funded status, the Company expects to make contributions of $24.5 million to the pension plans in 2012.

The following represents expected future benefit payments, which reflect expected future service, as appropriate:

	Pension    Benefits	Other Postretirement      Benefits
	(In thousands)
2012	$    17,898	$     3,411
2013	20,854	3,787
2014	22,803	4,060
2015	22,492	4,406
2016	26,185	4,694
Years 2017-2021	164,788	25,122
	$  275,020	$  45,480

Other Plans

The Company sponsors savings plans which were established to assist eligible employees provide for their future retirement needs. The Company's expense, representing its contributions to the plans, was $25.9 million, $18.1 million and $15.9 million for the years ended December 31, 2011, 2010 and 2009, respectively.

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Taxes

12 Months Ended

Dec. 31, 2011

Taxes [Abstract]

Taxes

12.  Taxes

The Company is subject to U.S. federal income tax as well as income tax in multiple state jurisdictions. The tax years 2005 through 2011 remain open to examination for U.S. federal income tax matters and 1998 through 2011 remain open to examination for various state income tax matters.

Significant components of the provision for (benefit from) income taxes are as follows:

	Year Ended December 31
	2011	2010	2009
	(In thousands)
Current:
Federal	$   (20,164)	$    34,304	$    21,295
State	1,212	2,283	864
Total current	(18,952)	36,587	22,159
Deferred:
Federal	13,214	(18,506)	(39,492)
State	(1,851)	(367)	558
Total deferred	11,363	(18,873)	(38,934)
	$     (7,589)	$    17,714	$   (16,775)

A reconciliation of the statutory federal income tax expense on the Company's pretax income to the actual provision for (benefit from) income taxes follows:

	Year Ended December 31
	2011	2010	2009
	(In thousands)
Income tax expense at statutory rate	$    46,933	$     61,800	$       8,888
Percentage depletion allowance	(61,971)	(49,152)	(29,463)
State taxes, net of effect of federal taxes	(3,055)	2,299	(61)
Change in valuation allowance	2,416	(383)	725
Other, net	8,088	3,150	3,136
	$     (7,589)	$      17,714	$    (16,775)

In 2011, 2010 and 2009, compensatory stock options and other equity based compensation awards were exercised resulting in a tax expense (benefit) of $(0.4) million, $(0.8) million and $0.2 million, respectively. The tax benefit will be recorded in paid-in capital at such point in time when a cash tax benefit is recognized.

Significant components of the Company's deferred tax assets and liabilities that result from carryforwards and temporary differences between the financial statement basis and tax basis of assets and liabilities are summarized as follows:

	December 31
	2011	2010
	(In thousands)
Deferred tax assets:
Alternative minimum tax credit carryforwards	$   151,404	$   170,592
Net operating loss carryforwards	324,393	102,355
Reclamation and mine closure	93,914	71,533
Advance royalties	—	38,557
Plant and equipment	—	19,846
Acquired sales contracts	44,717	20,120
Other, primarily accrued liabilities	171,715	90,412
Gross deferred tax assets	786,143	513,415
Valuation allowance	(2,831)	(737)
Total deferred tax assets	783,312	512,678
Deferred tax liabilities
Plant and equipment	1,566,769	—
Deferred development	67,728	76,690
Investment in tax partnerships	66,502	68,538
Other	17,015	13,669
Total deferred tax liabilities	1,718,014	158,897
Net deferred tax asset (liability)	(934,702)	353,781
Current asset (liability)	42,051	(7,775)
Non-current deferred tax asset (liability)	$     (976,753)	$  361,556

The Company has federal net operating loss carryforwards for regular income tax purposes of $779.1 million at December 31, 2011 that will expire between 2012 and 2031. The Company has an alternative minimum tax credit carryforward of $151.4 million at December 31, 2011, which has no expiration date and can be used to offset future regular tax in excess of the alternative minimum tax.

During 2008, the Company reached a settlement with the IRS regarding the Company's treatment of the acquisition of the coal operations of Atlantic Richfield Company ("ARCO") and the simultaneous combination of the acquired ARCO operations and the Company's Wyoming operations into the Arch Western joint venture. The settlement did not result in a net change in deferred tax assets, but involved a re-characterization of deferred tax assets, including an increase in net operating loss carryforwards of $145.1 million and other amortizable assets which will provide additional tax deductions through 2013. A portion of these future cash tax benefits accrue to ARCO pursuant to the original purchase agreement, including $0.8 million, $1.3 million and $4.8 million paid in 2011, 2010 and 2009, respectively, that was recorded as goodwill.

The Company has recorded a valuation allowance for a portion of its deferred tax assets that management believes, more likely than not, will not be realized. Management reassesses the ability to realize its deferred tax assets annually in the fourth quarter or when circumstances indicate that the ability to realize deferred tax assets has changed. In determining the appropriate valuation allowance, the assessment takes into account expected future taxable income and available tax planning strategies. This review resulted in increases (decreases) in the valuation allowance of $2.1 million, $(0.4) million and $0.7 million in 2011, 2010 and 2009, respectively. The valuation allowance relates to certain state and foreign net operating loss benefits.

A reconciliation of the beginning and ending amounts of gross unrecognized tax benefits is as follows (in thousands):

Balance at January 1, 2009	$    4,878
Additions based on tax positions related to the current year	1,593
Additions for tax positions of prior years	205
Reductions for tax positions of prior years	(6)
Balance at December 31, 2009	6,670
Additions based on tax positions related to the current year	1,493
Additions for tax positions of prior years	85
Reductions for tax positions of prior years	(3,830)
Balance at December 31, 2010	4,418
Additions based on tax positions related to the current year	1,626
Additions for tax positions of prior years	2,754
Balance at December 31, 2011	$    8,798

If recognized, the entire amount of the gross unrecognized tax benefits at December 31, 2011 would affect the effective tax rate.

The Company recognizes interest and penalties accrued related to unrecognized tax benefits in income tax expense. The Company had accrued interest and penalties of $0.8 million and $0.6 million at December 31, 2011 and 2010, respectively, of which $0.2 million and $0.1 million was recognized as expense during 2011 and 2010, respectively. No gross unrecognized tax benefits are expected to be reduced in the next 12 months due to the expiration of the statute of limitations.

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Taxes (Schedule Of Deferred Tax Assets And Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Taxes [Abstract]
Alternative minimum tax credit carryforwards	$ 151,404	$ 170,592
Net operating loss carryforwards	324,393	102,355
Reclamation and mine closure	93,914	71,533
Advance royalties		38,557
Plant and equipment		19,846
Acquired sales contracts	44,717	20,120
Other	171,715	90,412
Gross deferred tax assets	786,143	513,415
Valuation allowance	(2,831)	(737)
Total deferred tax assets	783,312	512,678
Deferred tax liabilities, plant and equipment	1,566,769
Deferred development	67,728	76,690
Investment in tax partnerships	66,502	68,538
Other	17,015	13,669
Total deferred tax liabilities	1,718,014	158,897
Net deferred tax asset	(934,702)	353,781
Current liability	42,051	(7,775)
Long-term deferred tax asset	$ (976,753)	$ 361,556

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Equity Investments And Membership Interests In Joint Ventures

12 Months Ended

Dec. 31, 2011

Equity Investments And Membership Interests In Joint Ventures [Abstract]

Equity Investments And Membership Interests In Joint Ventures

8. Equity Investments and Membership Interests in Joint Ventures

Below are the equity method investments reflected in the consolidated balance sheets:

	Knight Hawk	DKRW	DTA	Tenaska	Millennium	Tongue River	Total
	(In thousands)
Balance at January 1 , 2009	$     48,093	$  25,124	$  14,544	$        —	$             —	$           —	$     87,761
Advances to (distributions from) affiliates, net	(5,164)	—	2,925	—	—	—	(2,239)
Equity in comprehensive income (loss)	6,674	(1,535)	(3,393)	—	—	—	1,746
Balance at December 31, 2009	49,603	23,589	14,076	—	—	—	87,268
Investments in affiliates	77,637	—	—	9,768	—	—	87,405
Advances to (distributions from) affiliates, net	(12,639)	—	4,264	—	—	—	(8,375)
Equity in comprehensive income (loss)	16,649	(1,628)	(3,868)	—	—	—	11,153
Balance at December 31, 2010	$ 131,250	$  21,961	$  14,472	$   9,768	$           —	$           —	$  177,451
Investments in affiliates	—	—	—	5,500	25,000	12,989	43,489
Advances to (distributions from) affiliates, net	(16,621)	—	6,498	—	3,477	—	(6,646)
Equity in comprehensive income (loss)	20,596	(2,246)	(4,884)	(2)	(2,153)	—	11,311
Balance at December 31, 2011	$ 135,225	$  19,715	$  16,086	$ 15,266	$  26,324	$   12,989	$  225,605
Notes receivable from investees:
Balance at December 31, 2010	$        1,700	$ 18,100	$         —	$   4,100	$           —	$           —	$   23,900
Balance at December 31, 2011	—	30,751	—	5,059	—	—	35,810

The Company holds an equity interest in Knight Hawk Holdings, LLC ("Knight Hawk"), a coal producer in the Illinois Basin. In June 2010, the Company exchanged 68.4 million tons of coal reserves in the Illinois Basin for an additional 9% ownership interest, increasing the Company's ownership in Knight Hawk to 42% from 33 1/3%. The Company recognized a gain of $41.6 million on the transaction, representing the difference between the fair value and the $12.1 million net book value of the coal reserves, adjusted for the Company's retained ownership interest in the reserves through its investment in Knight Hawk. In December 2010, the Company increased its ownership interest in Knight Hawk to 49% for $26.6 million in cash.

The Company holds a 24% equity interest in DKRW Advanced Fuels LLC ("DKRW"), a company engaged in developing coal-to-liquids facilities. Under a coal reserve purchase option with DKRW, DKRW could purchase reserves from the Company, which the Company would then mine on a contract basis for DKRW. DKRW may borrow funds from the Company under a convertible secured promissory note. Amounts borrowed are due and payable in cash or in additional equity interests on the earlier of April 15, 2012 or upon the closing of DKRW's next financing, bear interest at the rate of 1.25% per month, and are secured by DKRW's equity interests in Medicine Bow Fuel & Power LLC. As of December 31, 2011, DKRW had borrowed the maximum amount allowed under the note. The note balances above are reflected in other receivables on the consolidated balance sheets.

The Company holds a general partnership interest of 21.875% in Dominion Terminal Associates ("DTA"), which is accounted for under the equity method. DTA operates a ground storage-to-vessel coal transloading facility in Newport News, Virginia for use by the partners. Under the terms of a throughput and handling agreement with DTA, each partner is charged its share of cash operating and debt-service costs in exchange for the right to use the facility's loading capacity and is required to make periodic cash advances to DTA to fund such costs.

The Company holds a 35% ownership interest in Tenaska Trailblazer Partners, LLC ("Tenaska"), the developer of the Trailblazer Energy Center, a fossil-fuel-based electric power plant near Sweetwater, Texas. The plant, fueled by low sulfur coal, will capture and store carbon dioxide for enhanced oil recovery applications. Additional future payments are due upon the achievement of project milestones to maintain the Company's interest. The Company made a milestone payment of $5.5 million in 2011. The Company will also pay 35% of the future development costs of the project, not to exceed $12.5 million without prior approval from the Company. The receivables for these development costs, shown above, are reflected in the consolidated balance sheets in other noncurrent assets, as the development costs will either be reimbursed when the project receives construction financing, or they will be considered an additional capital contribution, with ownership percentages adjusted accordingly.

In January 2011, the Company purchased a 38% ownership interest in Millennium Bulk Terminals-Longview, LLC ("Millennium"), the owner of a brownfield bulk commodity terminal on the Columbia River near Longview, Washington, for $25.0 million, plus additional future consideration upon the completion of certain project milestones. Millennium continues to work on obtaining the required approvals and necessary permits to complete dredging and other upgrades to enable coal, alumina and cementitious material shipments through the terminal. The Company will control 38% of the terminal's throughput and storage capacity, in order to facilitate export shipments of coal off the west coast of the United States.

In July 2011, the Company purchased a 33% membership interest in the Tongue River Holding Company, LLC ("Tongue River") joint venture.  Tongue River will develop and construct a railway line near Miles City, Montana and the Company's Otter Creek reserves.  The Company has the right, upon the receipt of permits and approval for construction or under other prescribed circumstances, to require the other investors to purchase all of the Company's units in the venture at an amount equal to the capital contributions made by the Company at that time, less any distributions received.    

Under development financing agreements with certain investees, the Company may be required to make future contingent payments of up to $74.4 million, including milestone payments. The Company's obligation to make these payments, as well as the timing of any payments required, is contingent upon a number of factors, including project development progress, receipt of permits and construction financing.

Summarized financial information of the Company's equity method investees follows:

	December 31
	2011	2010	2009
Condensed combined income statement information:	(In thousands)
Revenues	$  184,358	$  172,933	$  166,152
Gross profit	19,495	25,203	15,426
Income from operations	13,180	20,243	1,611
Net income (loss)	6,788	16,015	(1,797)
Condensed combined balance sheet information:
Current assets	$    94,644	$    48,202
Noncurrent assets	331,848	276,125
Total assets	$  426,492	$  324,327
Current liabilities	$    51,674	$    39,237
Noncurrent liabilities	120,494	99,350
Equity	254,163	185,639
Noncontrolling interest	161	101
Total liabilities and equity	$  426,492	$  324,327

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Business Combinations (Narrative) (Details) (USD $) Share data in Thousands, unless otherwise specified	12 Months Ended			0 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Jun. 15, 2011 Number Of Mining Complexes - Appalachia [Member]	Jun. 15, 2011 Number Of Mining Complexes - Illinois [Member]	Oct. 01, 2009 Jacobs Ranch Mining Operations [Member]
Business Acquisition [Line Items]
Number of mining complexes operated				12	one
Number of mining complexes being developed				one
Proceeds from the issuance of common stock, net	$ 1,267,933,000		$ 326,452,000
Number of shares sold	48,705		19,550
Proceeds from issuance of aggregate principal amount of senior notes	2,000,000,000	500,000,000	584,784,000
Revenues related to the acquired operations included in the statement of income since acquisition	606,900,000
Income before income taxes related to the acquired operations included in the statement of income since acquisition		14,600,000
Restricted cash	10,300,000
Business Acquisition, Cost of Acquired Entity, Purchase Price						$ 768,800,000
Tons Of Coal						345,000,000

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Guarantees (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Magnum [Member]
Guarantees and Commitments
Guarantee obligations, maximum exposure, undiscounted	$ 15.3
Excess of the current market cost of purchasing coal over the selling price	199.4
Volume of purchased coal in tons	9,800,000
Performance Guarantee [Member] | Magnum [Member]
Guarantees and Commitments
Volume of purchased coal in tons	700,000
Bonding Requirements [Member] | Magnum [Member]
Guarantees and Commitments
Surety bonds posted in the company's favor	48.9
Letters of credit posted in the Company's favor	16.1
Guarantee obligations, maximum exposure, undiscounted	38.5
Indemnification Agreement [Member]
Guarantees and Commitments
Guarantee obligations, maximum exposure, undiscounted	19.3
Coal, materials and supplies and capital commitments, other than reserve acquisitions, and transportation capacity agreements [Member]
Guarantees and Commitments
Unrecorded Unconditional Purchase Obligation Due Current	487.5
Unrecorded Unconditional Purchase Obligation Due in Two Years	139.2
Unrecorded Unconditional Purchase Obligation Due in Three Years	175.0
Unrecorded Unconditional Purchase Obligation Due in Four Years	163.9
Unrecorded Unconditional Purchase Obligation Due in Five Years	128.3
Unrecorded Unconditional Purchase Obligation, Due after Five Years	$ 154.8

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Acquired Sales Contracts

12 Months Ended

Dec. 31, 2011

Acquired Sales Contracts [Abstract]

Acquired Sales Contracts

6. Acquired Sales Contracts

The acquired sales contracts reflected in the condensed consolidated balance sheets are as follows:

		December 31, 2011				December 31, 2010
		Assets		Liabilities		Assets		Liabilities
		(In thousands)				(In thousands)
Acquired fair value	$	149,457	$	166,697	$	114,453	$	40,654
Accumulated amortization		(115,322)		(69,699)		(82,376)		(14,613)
Total	$	34,135	$	96,998	$	32,077	$	26,041
Net total			$	(62,863)	$	6,036
Balance Sheet classification:
Other current	$	18,929	$	38,441	$	25,063	$	5,615
Other noncurrent	$	15,206	$	58,557	$	7,014	$	20,426

Above-market contracts with a fair value of $35.0 million and below-market contracts with a fair value of $126.0 million were acquired from ICG. See Note 3, "Business Combinations" for discussion of purchase price adjustments.

The Company anticipates amortization income of all acquired sales contracts, based upon expected shipments in the next five years, to be approximately $18.5 million in 2012, $5.2 million in 2013, $3.3 million in 2014, $12.7 million in 2015 and $7.7 million in 2016.

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Accumulated Other Comprehensive Income (Loss)

12 Months Ended

Dec. 31, 2011

Accumulated Other Comprehensive Income (Loss) [Abstract]

Accumulated Other Comprehensive Income (Loss)

7.  Accumulated Other Comprehensive Income (Loss)

Other comprehensive income (loss) includes transactions recorded in stockholders' equity during the year, excluding net income and transactions with stockholders. Following are the items included in accumulated other comprehensive income (loss):

	Derivative Instruments	Pension, Postretirement    and Other         Post-   Employment      Benefits	Available-for- Sale Securities	Accumulated         Other Comprehensive          Loss
	(In thousands)
Balance at January 1, 2009	$   (45,249)	$                     (33,433)	$         (414)	$       (79,096)
2009 activity, before tax	72,553	20,124	(136)	92,541
2009 activity, tax effect	(26,118)	(7,230)	50	(33,298)
Balance at December 31, 2009	1,186	(20,539)	(500)	(19,853)
2010 activity, before tax	2,711	15,406	2,877	20,994
2010 activity, tax effect	(976)	(5,546)	(1,036)	(7,558)
Balance at December 31, 2010	2,921	(10,679)	1,341	(6,417)
2011 activity, before tax	(11,951)	9,345	176	(2,430)
2011 activity, tax effect	4,301	(3,342)	(62)	897
Balance at December 31, 2011	$     (4,729)	$     (4,676)	$    1,455	$       (7,950)

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Inventories

12 Months Ended

Dec. 31, 2011

Inventories [Abstract]

Inventories

9.  Inventories

Inventories consist of the following:

	December 31
	2011	2010
	(In thousands)
Coal	$  206,517	$  115,647
Repair parts and supplies	163,527	119,969
Work-in-process	7,446	—
	$  377,490	$  235,616

The work-in-process is related the Company's ADDCAR subsidiary acquired with ICG, which manufactures and sells its patented highwall mining system. The repair parts and supplies are stated net of an allowance for slow-moving and obsolete inventories of $13.1 million and $12.7 million at December 31, 2011 and 2010, respectively.

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Goodwill (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Goodwill [Line Items]
Goodwill	$ 596,103	$ 114,963	$ 113,701	$ 46,832
Powder River Basin Segment [Member]
Goodwill [Line Items]
Goodwill	115,800
Appalachia Segment [Member]
Goodwill [Line Items]
Goodwill	$ 480,300

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Fair Value Measurements (Narrative) (Details) (USD $)			12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Level 3 [Member]
Fair Value Measurements [Line Items]
Net unrealized losses related to level 3 financial instruments			$ 13,100,000
Fair value of senior notes and other long-term debt, including amounts classified as current	$ 4,200,000,000	$ 1,700,000,000

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Debt And Financing Arrangements (Narrative) (Details) (USD $)

12 Months Ended

12 Months Ended

12 Months Ended

12 Months Ended

0 Months Ended

0 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

12 Months Ended

0 Months Ended

Dec. 31, 2011

Dec. 31, 2010

Dec. 31, 2009

Jun. 15, 2011

Dec. 31, 2011

7.00% Senior Notes Due June 15, 2019 [Member]

Dec. 31, 2011

7.25% Senior Notes Due 2021 [Member]

Dec. 31, 2011

2019 and 2021 Notes [Member]

Dec. 31, 2011

Revolving Credit Facility [Member]

Dec. 31, 2011

Accounts Receivable Securitization Program [Member]

Dec. 12, 2011

Accounts Receivable Securitization Program [Member]

Jul. 14, 2011

9.125% Senior Notes Due April 1, 2018 [Member]

Jun. 14, 2011

9.125% Senior Notes Due April 1, 2018 [Member]

Jun. 15, 2011

4.00% Convertible Senior Notes Due April 1, 2017 [Member]

Jun. 14, 2011

4.00% Convertible Senior Notes Due April 1, 2017 [Member]

Jun. 15, 2011

9.00% Convertible Senior Notes Due August 1, 2012 [Member]

Jun. 14, 2011

9.00% Convertible Senior Notes Due August 1, 2012 [Member]

Dec. 31, 2011

ICG Debt [Member]

Sep. 08, 2010

6.75% Senior Notes Due July 1, 2013 [Member]

Dec. 31, 2011

6.75% Senior Notes Due July 1, 2013 [Member]

Dec. 31, 2010

6.75% Senior Notes Due July 1, 2013 [Member]

Dec. 31, 2011

8.75% Senior Notes Due August 1, 2016 [Member]

Dec. 31, 2011

7.25% Senior Notes Due October 10, 2020 [Member]

Dec. 31, 2011

6.75% Senior Notes [Member]

Dec. 31, 2012

Secured Credit Facility [Member]

years

Dec. 31, 2011

Secured Credit Facility [Member]

Dec. 31, 2010

Secured Credit Facility [Member]

Dec. 31, 2011

Prior to June 15, 2014 [Member]

7.00% Senior Notes Due June 15, 2019 [Member]

Dec. 31, 2011

Prior to June 15, 2014 [Member]

7.25% Senior Notes Due 2021 [Member]

Dec. 31, 2011

Prior to June 15, 2014 [Member]

2019 and 2021 Notes [Member]

Dec. 31, 2011

June 15, 2015 Through June 14, 2016 [Member]

7.00% Senior Notes Due June 15, 2019 [Member]

Dec. 31, 2011

June 15, 2016 Through June 14, 2017 [Member]

7.00% Senior Notes Due June 15, 2019 [Member]

Dec. 31, 2011

June 15, 2016 Through June 14, 2017 [Member]

7.25% Senior Notes Due 2021 [Member]

Dec. 31, 2011

June 15, 2017 And Beyond [Member]

7.00% Senior Notes Due June 15, 2019 [Member]

Dec. 31, 2011

June 15, 2019 and Beyond [Member]

7.25% Senior Notes Due 2021 [Member]

Dec. 31, 2011

June 15, 2017 Through June 14, 2018 [Member]

7.25% Senior Notes Due 2021 [Member]

Dec. 31, 2011

June 15, 2018 Through June 14, 2019 [Member]

7.25% Senior Notes Due 2021 [Member]

Dec. 31, 2011

Redeemable Between August 1, 2013 And July 31, 2014 [Member]

8.75% Senior Notes Due August 1, 2016 [Member]

Dec. 31, 2011

Redeemable Between August 1, 2014 And July 31, 2015 [Member]

8.75% Senior Notes Due August 1, 2016 [Member]

Dec. 31, 2011

August 1, 2015 And Beyond [Member]

Dec. 31, 2011

Redeemable Between October 1, 2015 And September 30, 2016 [Member]

7.25% Senior Notes Due October 10, 2020 [Member]

Dec. 31, 2011

Redeemable Between October 1, 2016 And September 30, 2017 [Member]

7.25% Senior Notes Due October 10, 2020 [Member]

Dec. 31, 2011

Redeemable Between October 1, 2017 And September 30, 2018 [Member]

7.25% Senior Notes Due October 10, 2020 [Member]

Dec. 31, 2011

Redeemable On Or After October 1, 2018 [Member]

7.25% Senior Notes Due October 10, 2020 [Member]

Dec. 31, 2011

Redeemable Prior to October 1, 2013 [Member]

7.25% Senior Notes Due October 10, 2020 [Member]

Dec. 31, 2011

Redeemable Prior To August 1, 2012 [Member]

8.75% Senior Notes Due August 1, 2016 [Member]

Jul. 14, 2011

Repayment of Debt [Member]

9.125% Senior Notes Due April 1, 2018 [Member]

Debt Instrument [Line Items]

Debt instrument, interest rate, stated percentage

7.00%

7.25%

9.125%

4.00%

9.00%

6.75%

8.75%

7.25%

6.75%

Debt Instrument, Interest Rate at Period End

0.73%

Restricted cash

$ 10,322,000

$ 260,700,000

Subsequent event, senior notes redeemed

251,400,000

Accrued interest

213,697,000

134,866,000

76,801,000

5,200,000

Debt instrument, convertible, latest date

August 17, 2011

Debt assumed in acquisition

604,800,000

298,500,000

1,700,000

54,000,000

Calculated conversion rate

2,614.6848

2,392.73414

Principal amount increment for conversion

1,000

1,000

Net loss resulting from early retirement of debt

1,958,000

6,776,000

2,000,000

6,800,000

Maximum borrowing capacity

250,000,000

175,000,000

2,000,000,000

Line of credit facility, maturity term

5

Line of credit facility, expiration date

December 11, 2012

June 14, 2016

Line of credit facility, unused capacity, commitment fee percentage

0.50%

Weighted-average interest rate

3.04%

Secured revolving credit facility maximum borrowing amount

234,200,000

132,000,000

Letters of credit outstanding, amount

146,600,000

Incurred financing fees

90,500,000

37,600,000

14,500,000

21,100,000

Line of credit borrowings outstanding

375,000,000

106,300,000

Average borrowings

234,200,000

132,000,000

Line of credit facility, remaining borrowing capacity

901,400,000

Due date of senior notes

Jun. 15, 2019

Jul. 01, 2013

Aug. 01, 2016

Oct. 01, 2020

Amount of debt redeemed

500,000,000

Redemption premium on extinguishment of debt

5,600,000

Write off of Deferred Debt Issuance Cost

3,300,000

Debt Instrument, Unamortized Premium

2,100,000

Debt instrument, frequency of periodic payment

June 15 and December 15 of each year.

Interest is payable on the notes on January 1 and July 1 of each year.

Interest is payable on the notes on February 1 and August 1 of each year

April 1 and October 1 of each year

Face value of senior notes

450,000,000

600,000,000

Debt instrument redemption period

June 15, 2015 through June 14, 2016

June 15, 2016 through June 14, 2017

June 15, 2016 through June 14, 2017

on June 15, 2017

on June 15, 2019

June 15, 2017 through June 14, 2018

June 15, 2018 through June 14, 2019

between August 1, 2013 and July 31, 2014

between August 1, 2014 and July 31, 2015

prior to October 1, 2013

prior to August 1, 2012

Debt instrument initial issue price percentage of face amount

104.75%

97.464%

Debt Instrument covenant terms

Terms of the Company's credit facilities and leases contain financial and other covenants that limit the ability of the Company to, among other things, acquire, dispose, merge or consolidate assets; incur additional debt; pay dividends and make distributions or repurchase stock; make investments; create liens; issue and sell capital stock of subsidiaries; enter into restrictions affecting the ability of restricted subsidiaries to make distributions, loans or advances to the Company; engage in transactions with affiliates and enter into sale and leaseback transactions. The terms also require the Company to, among other things, maintain various financial ratios and comply with various other financial covenants, including an interest coverage ratio test, as defined in the indentures. In addition, the covenants require the Company to pledge assets to collateralize the revolving credit facility. The assets pledged include equity interests in wholly-owned subsidiaries, certain real property interests, accounts receivable and inventory of the Company. Failure by the Company to comply with such covenants could result in an event of default, which, if not cured or waived, could have a material adverse effect on the Company. The Company complied with all financial covenants at December 31, 2011.

The terms of the senior notes contain restrictive covenants that limit Arch Western's ability to, among other things, incur additional debt, sell or transfer assets, and make certain investments.

Debt instrument, issuer

Arch Western Finance LLC ("Arch Western Finance"

Call premium

108.75%

107.00%

107.25%

103.50%

101.75%

103.625%

100.00%

100.00%

102.417%

101.208%

104.375%

102.188%

100.00%

103.625%

102.417%

101.208%

100.00%

107.25%

Principal Outstanding Issued At Premium

118,400,000

118,400,000

Percentage of maximum redemption aggregate principal amount from equity proceeds

35.00%

35.00%

35.00%

Tender offer price upon change in control

101.00%

Issue costs related to notes

44,200,000

Expected aggregate maturities in 2012

280,900,000

Expected aggregate maturities in 2013

672,400,000

Expected aggregate maturities in 2014

0

Expected aggregate maturities in 2015

0

Expected aggregate maturities in 2016

$ 600,000,000

Registration statement effective date deadline

June 13, 2012

Registration Rights agreement violation additional per annum penalty

0.25%

Registration Rights agreement violation maximum per annum penalty

1.00%

Registration Rights agreement violation per annum penalty in first 90 days

0.25%

Failed to file registration statement, interest rate

one-quarter of one percent

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Stock Based Compensation And Other Incentive Plans (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Share based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for Incentive Plan	18,000,000
Exercised, aggregate intrinsic value	$ 2,600,000	$ 3,000,000	$ 100,000
Stock options compensation expense	8,800,000	10,600,000	11,800,000
Options vested in period fair value	9,900,000	10,600,000	9,100,000
Share based awards vesting period	four years
Unrecognized compensation cost	8,200,000
Long term incentive plan amounts accrued	65,323,000	51,327,000
Participants maximum deferred amount in base salaries percentage	85.00%
Participants maximum deferred amount in annual incentive awards percentage	100.00%
Participants maximum deferred stock awards percentage	100
Net cash surrender values	35,800,000	40,700,000
Net income (expense) related to deferred compensation plan	6,200,000	(2,800,000)	4,100,000
Deferred compensation plan liability	32,700,000	38,500,000
Restricted Stock [Member]
Share based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based awards vesting period	three
Weighted average fair value of restricted stock granted	$ 30.42	$ 22.03	$ 14.05
Grant date fair value	1,100,000	400,000	1,500,000
Restricted Stock Units [Member]
Share based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based awards vesting period	three years
Grant date fair value	1,400,000		400,000
Restricted Stock And Restricted Stock Units [Member]
Share based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted compensation expense	2,100,000	1,100,000	1,700,000
Unrecognized compensation cost	3,400,000
Long-Term Incentive Plan [Member]
Share based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	2,700,000	3,800,000	2,600,000
Long term incentive plan amounts accrued	$ 9,600,000	$ 6,400,000
Employee Stock Options [Member]
Share based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based awards vesting period	one year

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Business Combination (Schedule Of Costs And Expenses Reflected In The Income Before Income Taxes) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011
Business Combinations [Abstract]
Costs of completing the acquisition	$ 31,600,000
Severance costs	15,800,000
Write off of acquired assets	7,300,000
Bridge financing fees	49,490,000
Total cost and expenses	$ 104,200,000

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Accrued Workers' Compensation (Schedule Of Assumptions Used) (Details) (Workers' Compensation [Member])	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Workers' Compensation [Member]
Accrued Workers Compensation [Line Items]
Discount rate	5.10%	5.96%	6.11%
Cost escalation rate	3.00%	3.00%	3.00%

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Valuation And Qualifying Accounts

12 Months Ended

Dec. 31, 2011

Valuation And Qualifying Accounts [Abstract]

Valuation And Qualifying Accounts

Arch Coal, Inc. and Subsidiaries

Valuation and Qualifying Accounts

	Balance at Beginning    of Year	Additions     (Reductions) Charged to Costs and Expenses	Charged to        Other    Accounts	Deductions(a)	Balance at End of Year
	(In thousands)
Year ended December 31, 2011
Reserves deducted from asset accounts:
Other assets — other notes and accounts receivable	$           —	$            17	$          —	$        —	$          17
Current assets — supplies and inventory	12,701	1,755	—	1,349	13,107
Deferred income taxes	737	2,416	—	322	2,831
Year ended December 31, 2010
Reserves deducted from asset accounts:
Other assets — other notes and accounts receivable	$        109	$            —	$          —	$      109	$           —
Current assets — supplies and inventory	13,406	1,962	—	2,667	12,701
Deferred income taxes	1,120	(383)	—	—	737
Year ended December 31, 2009
Reserves deducted from asset accounts:
Other assets — other notes and accounts receivable	$        225	$           (17)	$          —	$        99	$        109
Current assets — supplies and inventory	12,760	1,302	—	656	13,406
Deferred income taxes	395	725	—	—	1,120

____________

(a) Reserves utilized, unless otherwise indicated.

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Risk Concentrations (Tables)

12 Months Ended

Dec. 31, 2011

Segments, Geographical Areas [Abstract]

Schedule of Revenue from External Customers Attributed to Foreign Countries by Geographic Area

The Company uses shipping destination as the basis for attributing revenue to individual countries.   The Company's foreign revenues by geographical location for the year ended December 31, 2011, follows:

	December 31, 2011
	(In thousands)
Europe	$          427,514
South America	120,842
North America	97,255
Asia	61,308
Brokered sales	213,087
Total	$          920,006

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Asset Retirement Obligations

12 Months Ended

Dec. 31, 2011

Asset Retirement Obligations [Abstract]

Asset Retirement Obligations

14.  Asset Retirement Obligations

The Company's asset retirement obligations arise from the Federal Surface Mining Control and Reclamation Act of 1977 and similar state statutes, which require that mine property be restored in accordance with specified standards and an approved reclamation plan. The required reclamation activities to be performed are outlined in the Company's mining permits. These activities include reclaiming the pit and support acreage at surface mines, sealing portals at underground mines, and reclaiming refuse areas and slurry ponds.

The following table describes the changes to the Company's asset retirement obligation liability:

	Year Ended December 31
	2011	2010
	(In thousands)
Balance at January 1 (including current portion)	$  343,119	$  310,409
Accretion expense	33,601	26,615
Obligations incurred or acquired	115,019	—
Adjustments to the liability from changes in estimates	11,176	8,934
Liabilities settled	(29,012)	(2,839)
Balance at December 31	$  473,903	$  343,119
Current portion included in accrued expenses	(27,119)	(8,862)
Noncurrent liability	$  446,784	$  334,257

Liabilities settled of $29.0 million in 2011 related to reclamation activities at the Black Thunder mining complex related to a pit acquired with the Jacobs Ranch operations in 2009.

As of December 31, 2011, the Company had $263.0 million in surety bonds outstanding and $420.5 million in self-bonding to secure reclamation obligations.

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Supplemental Condensed Consolidating Financial Information (Schedule Of Condensed Consolidating Statements Of Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
REVENUES	$ 1,228,756	$ 1,198,673	$ 985,528	$ 872,938	$ 835,394	$ 874,705	$ 764,295	$ 711,874	$ 4,285,895	$ 3,186,268	$ 2,576,081
Costs, expenses and other
Cost of sales									3,267,910	2,395,812	2,070,715
Depreciation, depletion and amortization									466,587	365,066	301,608
Amortization of acquired sales contracts, net									(22,069)	35,606	19,623
Selling, general and administrative expenses									119,056	118,177	97,787
Change in fair value of coal derivatives and coal trading activities, net									(2,907)	8,924	(12,056)
Acquisition and transition costs									54,676		13,726
Gain on Knight Hawk transaction							(41,600)			(41,577)
Other operating (income) expense, net									(10,934)	(19,724)	(39,036)
Total operating expenses									3,872,319	2,862,284	2,452,367
Income from operations	139,728	76,256	95,354	102,238	86,938	98,347	106,499	32,200	413,576	323,984	123,714
Interest expense									(230,186)	(142,549)	(105,932)
Interest income									3,309	2,449	7,622
Interest expense, net									(226,877)	(140,100)	(98,310)
Bridge financing costs related to ICG									(49,490)
Net loss resulting from early retirement of debt									(1,958)	(6,776)
Other non-operating expense, Total									(51,448)	(6,776)
Income before income taxes									135,251	177,108	25,404
Provision for (benefit from) income taxes									(7,589)	17,714	(16,775)
Net income	71,215	9,121	6,630	55,874	48,031	46,859	66,274	(1,770)	142,840	159,394	42,179
Less: Net income attributable to noncontrolling interest									(1,157)	(537)	(10)
Net income attributable to Arch Coal, Inc.									141,683	158,857	42,169
Parent/Issuer [Member]
Costs, expenses and other
Cost of sales									22,925	11,526	7,481
Depreciation, depletion and amortization									2,883	2,933	3,678
Selling, general and administrative expenses									74,591	79,580	49,672
Acquisition and transition costs									54,676		13,726
Other operating (income) expense, net									(23,306)	(10,259)	(12,909)
Total operating expenses									131,769	83,780	61,648
Income from investment in subsidiaries									556,448	393,366	165,183
Income from operations									424,679	309,586	103,535
Interest expense									(256,220)	(143,606)	(92,371)
Interest income									16,282	11,128	14,240
Interest expense, net									(239,938)	(132,478)	(78,131)
Bridge financing costs related to ICG									(49,490)
Other non-operating expense, Total									(49,490)
Income before income taxes									135,251	177,108	25,404
Provision for (benefit from) income taxes									(7,589)	17,714	(16,775)
Net income									142,840	159,394	42,179
Less: Net income attributable to noncontrolling interest									(1,157)	(537)	(10)
Net income attributable to Arch Coal, Inc.									141,683	158,857	42,169
Guarantor Subsidiaries [Member]
REVENUES									2,024,168	1,137,980	924,692
Costs, expenses and other
Cost of sales									1,537,697	797,917	713,782
Depreciation, depletion and amortization									304,742	194,847	138,125
Amortization of acquired sales contracts, net									(41,527)
Selling, general and administrative expenses									13,860	7,355	7,504
Change in fair value of coal derivatives and coal trading activities, net									(2,907)	8,924	(12,056)
Gain on Knight Hawk transaction										(41,577)
Other operating (income) expense, net									(118,767)	(115,994)	(85,460)
Total operating expenses									1,693,098	851,472	761,895
Income from operations									331,070	286,508	162,797
Interest expense									(5,062)	(2,763)	(2,442)
Interest income									759	456	720
Interest expense, net									(4,303)	(2,307)	(1,722)
Net loss resulting from early retirement of debt									(1,958)
Other non-operating expense, Total									(1,958)
Income before income taxes									324,809	284,201	161,075
Net income									324,809	284,201	161,075
Net income attributable to Arch Coal, Inc.									324,809	284,201	161,075
Non-Guarantor Subsidiaries [Member]
REVENUES									2,261,727	2,048,288	1,651,389
Costs, expenses and other
Cost of sales									1,812,461	1,679,872	1,398,663
Depreciation, depletion and amortization									158,962	167,286	159,805
Amortization of acquired sales contracts, net									19,458	35,606	19,623
Selling, general and administrative expenses									37,839	38,496	46,563
Other operating (income) expense, net									18,732	5,772	4,170
Total operating expenses									2,047,452	1,927,032	1,628,824
Income from operations									214,275	121,256	22,565
Interest expense									(43,728)	(64,463)	(70,668)
Interest income									61,092	59,148	52,211
Interest expense, net									17,364	(5,315)	(18,457)
Net loss resulting from early retirement of debt										(6,776)
Other non-operating expense, Total										(6,776)
Income before income taxes									231,639	109,165	4,108
Net income									231,639	109,165	4,108
Net income attributable to Arch Coal, Inc.									231,639	109,165	4,108
Eliminations [Member]
Costs, expenses and other
Cost of sales									(105,173)	(93,503)	(49,211)
Selling, general and administrative expenses									(7,234)	(7,254)	(5,952)
Other operating (income) expense, net									112,407	100,757	55,163
Income from investment in subsidiaries									(556,448)	(393,366)	(165,183)
Income from operations									(556,448)	(393,366)	(165,183)
Interest expense									74,824	68,283	59,549
Interest income									(74,824)	(68,283)	(59,549)
Income before income taxes									(556,448)	(393,366)	(165,183)
Net income									(556,448)	(393,366)	(165,183)
Net income attributable to Arch Coal, Inc.									$ (556,448)	$ (393,366)	$ (165,183)

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Risk Concentrations

12 Months Ended

Dec. 31, 2011

Risk Concentrations [Abstract]

Risk Concentrations

19.  Risk Concentrations

Credit Risk and Major Customers

The Company has a formal written credit policy that establishes procedures to determine creditworthiness and credit limits for trade customers and counterparties in the over-the-counter coal market. Generally, credit is extended based on an evaluation of the customer's financial condition. Collateral is not generally required, unless credit cannot be established. Credit losses are provided for in the financial statements and historically have been minimal.

The Company markets its steam coal principally to electric utilities in the United States and its metallurgical coal to domestic and foreign steel producers. Revenues from export sales were $920.0 million, $471.5 million and $194.4 million for the years ended December 31, 2011, 2010 and 2009, respectively. The increasing export sales are primarily the result of an increase in metallurgical-quality coal sales volumes, although steam coal exports also increased.  As of December 31, 2011 and 2010, accounts receivable from electric utilities located in the United States totaled $261.2 million and $183.1 million, respectively, or 69% and 88% of total trade receivables, respectively.  As of December 31, 2011 and 2010, accounts receivable from sales of metallurgical-quality coal totaled $117.4 million and $24.9 million, respectively, or 31% and 12%, of total trade receivables, respectively.

The Company uses shipping destination as the basis for attributing revenue to individual countries.   The Company's foreign revenues by geographical location for the year ended December 31, 2011, follows:

	December 31, 2011
	(In thousands)
Europe	$          427,514
South America	120,842
North America	97,255
Asia	61,308
Brokered sales	213,087
Total	$          920,006

The Company is committed under long-term contracts to supply steam coal that meets certain quality requirements at specified prices. These prices are generally adjusted based on indices. Quantities sold under some of these contracts may vary from year to year within certain limits at the option of the customer. The Company sold approximately 156.9 million tons of coal in 2011. Approximately 72% of this tonnage (representing approximately 57% of the Company's revenue) was sold under long-term contracts (contracts having a term of greater than one year). Long-term contracts range in remaining life from one to nine years. Sales (including spot sales) to the Company's largest customer, Tennessee Valley Authority, were $266.8 million, $301.4 million and $278.8 million for the years ended December 31, 2011, 2010 and 2009, respectively.

Third-party sources of coal

The Company uses independent contractors to mine coal at certain mining complexes. The Company also purchases coal from third parties that it sells to customers. Factors beyond the Company's control could affect the availability of coal produced for or purchased by the Company. Disruptions in the quantities of coal produced for or purchased by the Company could impair its ability to fill customer orders or require it to purchase coal from other sources at prevailing market prices in order to satisfy those orders.

Transportation

The Company depends upon barge, rail, truck and belt transportation systems to deliver coal to its customers. Disruption of these transportation services due to weather-related problems, mechanical difficulties, strikes, lockouts, bottlenecks, and other events could temporarily impair the Company's ability to supply coal to its customers, resulting in decreased shipments. In the past, disruptions in rail service have resulted in missed shipments and production interruptions.

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Employee Benefit Plans (Schedule Of Defined Benefit Plans Disclosures) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plan Disclosure [Line Items]
Value of plan assets at December 31	$ 285,074	$ 247,713
Accumulated gain (loss)	5,500	(2,000)
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligations at January 1	297,707	280,693
Service cost	16,490	15,870	13,444
Interest cost	16,253	15,822	15,946
Plan amendments	(3,235)	(92)
Benefits paid	(18,848)	(15,924)
Acquisition of ICG
Other-primarily actuarial loss (gain)	25,584	1,338
Benefit obligations at December 31	333,951	297,707	280,693
Value of plan assets at January 1	247,713	211,899
Actual return on plan assets	9,443	34,401
Employer contributions	46,766	17,337
Value of plan assets at December 31	285,074	247,713	211,899
Accrued benefit cost	(48,877)	(49,994)
Prior service credit (cost)	1,736	(1,310)
Accumulated gain (loss)	(68,302)	(39,099)
Total not yet recognized as a component of net periodic benefit cost	(66,566)	(40,409)
Current liability	(633)	(840)
Noncurrent liability	(48,244)	(49,154)
Pension and other postretirement defined benefit plans, liabilities	(48,877)	(49,994)
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligations at January 1	39,633	46,445
Service cost	3,917	1,509	2,954
Interest cost	3,279	2,083	3,667
Plan amendments	(55,542)
Benefits paid	(1,669)	(1,845)
Acquisition of ICG	48,441
Other-primarily actuarial loss (gain)	7,070	(8,559)
Benefit obligations at December 31	45,129	39,633	46,445
Value of plan assets at January 1
Actual return on plan assets
Employer contributions	1,669	1,845
Value of plan assets at December 31
Accrued benefit cost	(45,129)	(39,633)
Prior service credit (cost)	62,920	9,742
Accumulated gain (loss)	1,795	11,965
Total not yet recognized as a component of net periodic benefit cost	64,715	21,707
Current liability	(2,820)	(1,840)
Noncurrent liability	(42,309)	(37,793)
Pension and other postretirement defined benefit plans, liabilities	$ (45,129)	$ (39,633)

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Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2011

Employee Benefit Plans [Abstract]

Schedule Of Defined Benefit Plans Disclosures

	Pension Benefits		Other Postretirement                Benefits
	2011	2010	2011	2010
	(In thousands)
CHANGE IN BENEFIT OBLIGATIONS
Benefit obligations at January 1	$  297,707	$  280,693	$    39,633	$    46,445
Service cost	16,490	15,870	3,917	1,509
Interest cost	16,253	15,822	3,279	2,083
Plan amendments	(3,235)	(92)	(55,542)	—
Benefits paid	(18,848)	(15,924)	(1,669)	(1,845)
Acquisition of ICG	—	—	48,441	—
Other-primarily actuarial loss (gain)	25,584	1,338	7,070	(8,559)
Benefit obligations at December 31	$  333,951	$  297,707	$    45,129	$    39,633
CHANGE IN PLAN ASSETS
Value of plan assets at January 1	$  247,713	$  211,899	$            —	$            —
Actual return on plan assets	9,443	34,401	—	—
Employer contributions	46,766	17,337	1,669	1,845
Benefits paid	(18,848)	(15,924)	(1,669)	(1,845)
Value of plan assets at December 31	$  285,074	$  247,713	$            —	$            —
Accrued benefit cost	$   (48,877)	$   (49,994)	$   (45,129)	$   (39,633)
ITEMS NOT YET RECOGNIZED AS A COMPONENT OF NET PERIODIC BENEFIT COST
Prior service credit (cost)	$       1,736	$      (1,310)	$    62,920	$      9,742
Accumulated gain (loss)	(68,302)	(39,099)	1,795	11,965
	$   (66,566)	$   (40,409)	$    64,715	$    21,707
BALANCE SHEET AMOUNTS
Current liability	$         (633)	$         (840)	$     (2,820)	$     (1,840)
Noncurrent liability	$   (48,244)	$   (49,154)	$   (42,309)	$   (37,793)
	$   (48,877)	$   (49,994)	$   (45,129)	$   (39,633)

Schedule Of Net Benefit Costs

	Pension Benefits			Other Postretirement Benefits
Year Ended December 31,	2011	2010	2009	2011	2010	2009
	(In thousands)
Service cost	$    16,490	$    15,870	$    13,444	$    3,917	$    1,509	$    2,954
Interest cost	16,253	15,822	15,946	3,279	2,083	3,667
Expected return on plan assets*	(21,812)	(19,392)	(17,719)	—	—	—
Amortization of prior service cost (credit)	(189)	173	193	(2,364)	(2,364)	2,161
Amortization of other actuarial losses (gains)	8,748	7,130	3,967	(3,100)	(2,918)	(2,897)
Curtailments	—	—	585	—	—	—
Net benefit cost	$    19,490	$    19,603	$    16,416	$    1,732	$   (1,690)	$    5,885

____________

* The Company does not fund its other postretirement benefit obligations.

Schedule Of Assumptions Used To Calculate Benefit Obligation

	Pension        Benefits		Other Postretirement        Benefits
	2011	2010	2011	2010
Weighted average assumptions:
Discount rate	4.91%	5.71%	4.52%	5.23%
Rate of compensation increase	3.39%	3.39%	N/A	N/A

Schedule Of Assumptions Used

	Pension Benefits			Other Postretirement Benefits
	2011	2010	2009	2011	2010	2009
Weighted average assumptions:
Discount rate	5.71%	5.97%	6.85%	5.23%	5.67%	6.85%/5.68%
Rate of compensation increase	3.39%	3.39%	3.39%	N/A	N/A	N/A
Expected return on plan assets	8.50%	8.50%	8.50%	N/A	N/A	N/A

Schedule Of Allocation Of Plan Assets

	Total		Level 1				Level 2		Level 3
	2011	2010		2011	2010	2011		2010		2011	2010
	(In thousands)
Equity securities:(A)
U.S. small-cap	$11,178	$10,647		$11,178	$10,647	$ —		$ —		$ —	$ —
U.S. mid-cap	50,264	46,851		23,474	21,163	26,790		25,688		—	—
U.S. large-cap	91,561	77,632		44,820	38,397	46,741		39,235		—	—
Non-U.S.	22,509	24,995		—	—	22,509		24,995		—	—
Fixed income securities:
U.S. government securities(B)	13,454	3,053		12,738	2,492	716		561		—	—
Non-U.S. government securities(C)	2,968	3,469		—	—	2,968		3,469		—	—
U.S. government asset and mortgage backed securities(D)	800	1,073		—	—	800		1,073		—	—
Corporate fixed income(E)	14,004	13,737		—	—	14,004		13,737		—	—
State and local government securities(F)	18,416	13,679		—	—	18,416		13,679		—	—
Other fixed income(G)	51,470	45,628		—	—	51,470		45,628		—	—
Short-term investments(H)	8,029	6,110		—	—	8,029		6,110		—	—
Other investments(I)	421	839		—	—	421		839		—	—
Total	$285,074	$247,713		$92,210	$72,699	$192,864		$175,014		$ —	$ —

____________

(A)	Equity securities includes investments in 1) common stock, 2) preferred stock and 3) mutual funds. Investments in common and preferred stocks are valued using quoted market prices multiplied by the number of shares owned. Investments in mutual funds are valued at the net asset value per share multiplied by the number of shares held as of the measurement date and are traded on listed exchanges.
(B)	U.S. government securities includes agency and treasury debt. These investments are valued using dealer quotes in an active market.
(C)	Non-U.S. government securities includes debt securities issued by foreign governments and are valued utilizing a price spread basis valuation technique with observable sources from investment dealers and research vendors.
(D)	U.S. government asset and mortgage backed securities includes government-backed mortgage funds which are valued utilizing an income approach that includes various valuation techniques and sources such as discounted cash flows models, benchmark yields and securities, reported trades, issuer trades and/or other applicable data.
(E)	Corporate fixed income is primarily comprised of corporate bonds and certain corporate asset-backed securities that are denominated in the U.S. dollar and are investment-grade securities. These investments are valued using dealer quotes.
(F)	State and local government securities include different U.S. state and local municipal bonds and asset backed securities, these investments are valued utilizing a market approach that includes various valuation techniques and sources such as value generation models, broker quotes, benchmark yields and securities, reported trades, issuer trades and/or other applicable data.
(G)	Other fixed income investments are actively managed fixed income vehicles that are valued at the net asset value per share multiplied by the number of shares held as of the measurement date.
(H)	Short-term investments include governmental agency funds, government repurchase agreements, commingled funds, and pooled funds and mutual funds. Governmental agency funds are valued utilizing an option adjusted spread valuation technique and sources such as interest rate generation processes, benchmark yields and broker quotes. Investments in governmental repurchase agreements, commingled funds and pooled funds and mutual funds are valued at the net asset value per share multiplied by the number of shares held as of the measurement date.
(I)	Other investments includes cash, forward contracts, derivative instruments, credit default swaps, interest rate swaps and mutual funds. Investments in interest rate swaps are valued utilizing a market approach that includes various valuation techniques and sources such as value generation models, broker quotes in active and non-active markets, benchmark yields and securities, reported trades, issuer trades and/or other applicable data. Forward contracts and derivative instruments are valued at their exchange listed price or broker quote in an active market. The mutual funds are valued at the net asset value per share multiplied by the number of shares held as of the measurement date and are traded on listed exchanges.

Summary Of Estimated Future Benefit Payments

	Pension    Benefits	Other Postretirement      Benefits
	(In thousands)
2012	$    17,898	$     3,411
2013	20,854	3,787
2014	22,803	4,060
2015	22,492	4,406
2016	26,185	4,694
Years 2017-2021	164,788	25,122
	$  275,020	$  45,480

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Stock-Based Compensation And Other Incentive Plans (Weighted Average Assumptions Used In Option Pricing) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011 years	Dec. 31, 2010 years	Dec. 31, 2009 years
Stock Based Compensation And Other Incentive Plans [Abstract]
Weighted average grant-date fair value per share of options granted	$ 14.18	$ 9.43	$ 6.63
Risk-free interest rate	1.92%	2.16%	1.75%
Expected dividend yield	1.25%	1.99%	2.56%
Expected volatility	57.40%	57.10%	69.30%
Expected life (in years)	4.5	4.5	4.5

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Equity Investments And Membership Interests In Joint Ventures (Tables)

12 Months Ended

Dec. 31, 2011

Equity Investments And Membership Interests In Joint Ventures [Abstract]

Schedule Of Equity Method Investments

	Knight Hawk	DKRW	DTA	Tenaska	Millennium	Tongue River	Total
	(In thousands)
Balance at January 1 , 2009	$     48,093	$  25,124	$  14,544	$        —	$             —	$           —	$     87,761
Advances to (distributions from) affiliates, net	(5,164)	—	2,925	—	—	—	(2,239)
Equity in comprehensive income (loss)	6,674	(1,535)	(3,393)	—	—	—	1,746
Balance at December 31, 2009	49,603	23,589	14,076	—	—	—	87,268
Investments in affiliates	77,637	—	—	9,768	—	—	87,405
Advances to (distributions from) affiliates, net	(12,639)	—	4,264	—	—	—	(8,375)
Equity in comprehensive income (loss)	16,649	(1,628)	(3,868)	—	—	—	11,153
Balance at December 31, 2010	$ 131,250	$  21,961	$  14,472	$   9,768	$           —	$           —	$  177,451
Investments in affiliates	—	—	—	5,500	25,000	12,989	43,489
Advances to (distributions from) affiliates, net	(16,621)	—	6,498	—	3,477	—	(6,646)
Equity in comprehensive income (loss)	20,596	(2,246)	(4,884)	(2)	(2,153)	—	11,311
Balance at December 31, 2011	$ 135,225	$  19,715	$  16,086	$ 15,266	$  26,324	$   12,989	$  225,605
Notes receivable from investees:
Balance at December 31, 2010	$        1,700	$ 18,100	$         —	$   4,100	$           —	$           —	$   23,900
Balance at December 31, 2011	—	30,751	—	5,059	—	—	35,810

Summarized Financial Information Of Equity Method Investments

	December 31
	2011	2010	2009
Condensed combined income statement information:	(In thousands)
Revenues	$  184,358	$  172,933	$  166,152
Gross profit	19,495	25,203	15,426
Income from operations	13,180	20,243	1,611
Net income (loss)	6,788	16,015	(1,797)
Condensed combined balance sheet information:
Current assets	$    94,644	$    48,202
Noncurrent assets	331,848	276,125
Total assets	$  426,492	$  324,327
Current liabilities	$    51,674	$    39,237
Noncurrent liabilities	120,494	99,350
Equity	254,163	185,639
Noncontrolling interest	161	101
Total liabilities and equity	$  426,492	$  324,327

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Risk Concentrations (Details) (USD $)	12 Months Ended
	Dec. 31, 2011 T	Dec. 31, 2010	Dec. 31, 2009
Concentration Risk [Line Items]
Sales to customers in foreign countries	$ 920,000,000	$ 471,500,000	$ 194,400,000
Trade accounts receivable	380,595,000	208,060,000
Receivables	469,179,000	252,320,000
Tons of coal sold	156,900,000
Percentage of tons sold	72.00%
Long-term contracts, life term, minimum (years)	one
Long term sales contract term, in years	to nine years
Electric Utilities [Member]
Concentration Risk [Line Items]
Percentage of total trade accounts receivable	69.00%	88.00%
Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Sales (including spot sales)	266,800,000	301,400,000	278,800,000
Domestic And Foreign Steel Producers [Member]
Concentration Risk [Line Items]
Trade accounts receivable	117,400,000	24,900,000
Trade receivables, percentage	31.00%	12.00%
Domestic Electric Utilities [Member]
Concentration Risk [Line Items]
Receivables	261,200,000	183,100,000
Long-term Contracts [Member]
Concentration Risk [Line Items]
Percentage of total revenue	57.00%
Europe [Member]
Concentration Risk [Line Items]
Sales to customers in foreign countries	427,514,000,000
South America [Member]
Concentration Risk [Line Items]
Sales to customers in foreign countries	120,842,000,000
North America [Member]
Concentration Risk [Line Items]
Sales to customers in foreign countries	97,255,000,000
Asia [Member]
Concentration Risk [Line Items]
Sales to customers in foreign countries	61,308,000,000
Brokered sales [Member]
Concentration Risk [Line Items]
Sales to customers in foreign countries	213,087,000,000
Total [Member]
Concentration Risk [Line Items]
Sales to customers in foreign countries	$ 920,006,000,000

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Consolidated Statements Of Stockholders' Equity (USD $) In Thousands, unless otherwise specified	Common Stock [Member]	Paid-In Capital [Member]	Treasury Stock, At Cost [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Total
BALANCE at Dec. 31, 2008	$ 1,447	$ 1,381,496	$ (53,848)	$ 478,734	$ (79,096)	$ 1,728,733
Comprehensive income:
Net income attributable to Arch Coal, Inc.				42,169		42,169
Pension, postretirement and other post-employment benefits					12,176	12,176
Net amount reclassified to income					718	718
Unrealized gains (losses) on available-for- sale securities					(86)	(86)
Unrealized gains (losses) on derivatives					2,436	2,436
Net amount reclassified to income					43,999	43,999
Total comprehensive income						101,412
Dividends:
Dividends on common shares ($0.36, 0.39 and 0.43 per share for the years 2009, 2010 and 2011 respectively)						(54,969)
Issuance of common shares (19,550 and 48,705 in 2009 and 2011 respectively)	196	326,256				326,452
Issuance of 45, 9 and 162 shares of common stock for the years 2009, 2010 and 2011 respectively under the stock incentive plan - restricted stock and restricted stock units, net of forfeitures	0	0				0
Issuance of 13, 155 and 199 shares of common stock for the years 2009, 2010 and 2011 respectively under the stock incentive plan - stock options including income tax benefits	0	84				84
Employee stock-based compensation expense		13,394				13,394
BALANCE at Dec. 31, 2009	1,643	1,721,230	(53,848)	465,934	(19,853)	2,115,106
Comprehensive income:
Net income attributable to Arch Coal, Inc.				158,857		158,857
Pension, postretirement and other post-employment benefits					9,750	9,750
Net amount reclassified to income					110	110
Unrealized gains (losses) on available-for- sale securities					1,841	1,841
Unrealized gains (losses) on derivatives					221	221
Net amount reclassified to income					1,514	1,514
Total comprehensive income						172,293
Dividends:
Dividends on common shares ($0.36, 0.39 and 0.43 per share for the years 2009, 2010 and 2011 respectively)				(63,373)		(63,373)
Issuance of 45, 9 and 162 shares of common stock for the years 2009, 2010 and 2011 respectively under the stock incentive plan - restricted stock and restricted stock units, net of forfeitures	0	0				0
Issuance of 13, 155 and 199 shares of common stock for the years 2009, 2010 and 2011 respectively under the stock incentive plan - stock options including income tax benefits	2	1,762				1,764
Employee stock-based compensation expense		11,717				11,717
BALANCE at Dec. 31, 2010	1,645	1,734,709	(53,848)	561,418	(6,417)	2,237,507
Comprehensive income:
Net income attributable to Arch Coal, Inc.				141,683		141,683
Pension, postretirement and other post-employment benefits					4,331	4,331
Net amount reclassified to income					1,672	1,672
Unrealized gains (losses) on available-for- sale securities					114	114
Unrealized gains (losses) on derivatives					2,913	2,913
Net amount reclassified to income					(10,563)	(10,563)
Total comprehensive income						140,150
Dividends:
Dividends on common shares ($0.36, 0.39 and 0.43 per share for the years 2009, 2010 and 2011 respectively)				(80,748)		(80,748)
Issuance of common shares (19,550 and 48,705 in 2009 and 2011 respectively)	487	1,267,446				1,267,933
Issuance of 45, 9 and 162 shares of common stock for the years 2009, 2010 and 2011 respectively under the stock incentive plan - restricted stock and restricted stock units, net of forfeitures	2	(2)				0
Issuance of 13, 155 and 199 shares of common stock for the years 2009, 2010 and 2011 respectively under the stock incentive plan - stock options including income tax benefits	2	2,314				2,316
Employee stock-based compensation expense		10,882				10,882
BALANCE at Dec. 31, 2011	$ 2,136	$ 3,015,349	$ (53,848)	$ 622,353	$ (7,950)	$ 3,578,040

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Asset Retirement Obligations (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Asset Retirement Obligations [Line Items]
Liabilities settled	$ (29,012,000)	$ (2,839,000)
Surety bonds outstanding	263,000,000
Asset Retirement Obligations [Member]
Asset Retirement Obligations [Line Items]
Self-bonding obligations	$ 420,500,000

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Business Combinations

12 Months Ended

Dec. 31, 2011

Business Combinations [Abstract]

Business Combinations

3. Business Combinations

On June 15, 2011, the Company completed its acquisition of ICG, a leading coal producer, adding 12 mining complexes in Appalachia, one complex in the Illinois Basin and one mine under development in Appalachia, along with other coal reserves not currently in development. The Company acquired all of ICG's outstanding shares of common stock. The acquisition was financed with the proceeds from the Company's sale of common stock and issuance of senior notes. See Note 5, "Debt and Financing Arrangements" and Note 17, "Capital Stock" for further information about these transactions.

The following table summarizes the consideration paid for ICG and the recognized amounts of assets acquired and liabilities assumed at the acquisition date:

	(In millions)
Consideration paid, net of cash acquired	$	2,894.4
Recognized amounts of net tangible and intangible assets acquired and liabilities assumed:
Restricted cash	15.5
Receivables	113.2
Inventories	91.0
Net property, plant and equipment, including mineral rights	4,582.6
Goodwill	480.3
Other assets	35.9
Accounts payable	(86.0		)
Other accrued expenses and current liabilities	(59.1		)
Debt	(604.8		)
Litigation accrual	(108.9		)
Accrued postretirement benefits	(47.7		)
Asset retirement obligation	(112.7		)
Coal supply agreements, net	(91.0		)
Deferred income taxes, net	(1,278.9		)
Other	(35.0		)
Net tangible and intangible assets acquired	$	2,894.4

The Company is awaiting the receipt of the final valuation report from a third party valuation services firm. As a result the fair values for mineral rights, goodwill and deferred taxes may not be final.

The revenues and income before income taxes related to the acquired operations reflected in the consolidated statements of income since the date of acquisition were $606.9 million and $14.6 million, respectively.

The following unaudited pro forma information has been prepared for illustrative purposes and assumes that the business combination occurred on January 1, 2010. The unaudited pro forma results have been prepared based upon ICG's historical results and estimates of the ongoing effects of the transactions that the Company believes are reasonable and supportable. The results are not necessarily reflective of the consolidated results of operations had the acquisition actually occurred on January 1, 2010, nor are they indicative of future operating results.

The unaudited supplemental pro forma financial information of the combined entity follows:

		Year Ended December 31,
		2011				2010
			(In millions)
Total revenues
As reported	$	4,285.9		$	3,186.3
Pro forma	$	4,825.6		$	4,299.9
Net income attributable to Arch Coal
As reported	$	141.7		$	158.9
Pro forma	$	113.5		$	(1.2)

The pro forma income before income taxes includes adjustments to operating costs to reflect the new basis in assets acquired and interest expense to reflect the debt incurred to finance the acquisition. In addition, the following pre-tax costs and expenses reflected in the accompanying consolidated statement of income for the year ended December 31, 2011 are reflected in the pro forma results above as of January 1, 2010.

		(In millions)
Costs of completing the acquisition	$	31.6
Severance costs		15.8
Write off of acquired assets		7.3
Bridge financing fees		49.5
	$	104.2

Severance costs represent both change in control payments to executives and severance for employees terminated after the acquisition. The acquired asset write-off relates to a preparation plant and loadout of an acquired ICG mining operation. The acquired operation was combined with an existing operation of the Company, and utilizes an existing facility.

Synergies from the acquisition are not reflected in the pro forma results.

In conjunction with the acquisition, the Company had $10.3 million of restricted cash at December 31, 2011 to fund change in control payments for executives.

On October 1, 2009 the Company purchased the Jacobs Ranch mining operations for a purchase price of $768.8 million. The acquired operations included approximately 345 million tons of coal reserves. The acquired mining operations were integrated into the Company's Black Thunder mining operations in its Powder River Basin segment. To finance the acquisition, the Company sold shares of its common stock and issued senior notes. See Note 5, "Debt and Financing Arrangements" and Note 17 "Capital Stock" for further information about these transactions.

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Accounting Policies (Details) (USD $)	12 Months Ended
	Dec. 31, 2011 years	Dec. 31, 2010
Accounting Policies [Line Items]
Company's membership interest percentage in joint venture	99.00%
Number of mining complexes operated	23
Net book value of leased coal interests	$ 10,868,694,000	$ 5,792,945,000
Minimum useful lives lease agreements	10
Minimum useful lives lease agreements	50
Incurred financing fees	90,500,000	37,600,000
Unamortized deferred financing costs, current	15,800,000	9,600,000
Buildings And Leasehold Improvements [Member]
Accounting Policies [Line Items]
Minimum useful life of mining equipment	10
Maximum useful life of mining equipment	30
Exploration And Production Equipment [Member]
Accounting Policies [Line Items]
Minimum useful life of mining equipment	5
Maximum useful life of mining equipment	32
Mining Properties And Mineral Rights [Member]
Accounting Policies [Line Items]
Net book value of leased coal interests	$ 1,600,000,000	$ 1,600,000,000

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Taxes (Schedule Of Components Of Income Tax) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Taxes [Abstract]
Current, Federal	$ (20,164)	$ 34,304	$ 21,295
Current, State	1,212	2,283	864
Total current	(18,952)	36,587	22,159
Deferred, Federal	13,214	(18,506)	(39,492)
Deferred, State	(1,851)	(367)	558
Total deferred	11,363	(18,873)	(38,934)
Provision for (benefit from) income taxes	$ (7,589)	$ 17,714	$ (16,775)

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Stock Based Compensation And Other Incentive Plans (Restricted Stock And Restricted Stock Unit Activity And Weighted Average Grant-Date Fair Value) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Restricted Stock [Member]
Share based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding as of January 1	74,000
Shares granted during the period	140,000
Vested	(27,000)
Canceled	(5,000)
Outstanding as of December 31	182,000	74,000
Outstanding as of January 1, Weighted Average Grant Price	$ 24.69
Granted, Weighted Average Grant-Date Fair Value	$ 30.42	$ 22.03	$ 14.05
Vested, Weighted Average Grant-Date Fair Value	$ 39.77
Canceled, Weighted Average Grant-Date Fair Value	$ 32.49
Outstanding as of December 31, Weighted Average Grant Price	$ 26.68	$ 24.69
Restricted Stock Units [Member]
Share based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding as of January 1	54,000.000
Vested	(27,000.000)
Outstanding as of December 31	27,000.000
Outstanding as of January 1, Weighted Average Grant Price	$ 52.69
Vested, Weighted Average Grant-Date Fair Value	$ 52.69
Outstanding as of December 31, Weighted Average Grant Price	$ 52.69

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Acquired Sales Contracts (Schedule Of Acquired Sales Contracts) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Acquired Finite-Lived Intangible Assets And Liabilities By Major Class [Line Items]
Acquired fair value, Assets	$ 149,457	$ 114,453
Acquired fair value, Liabilities	166,697	40,654
Accumulated amortization, Asset	(115,322)	(82,376)
Accumulated amortization, Liabilities	(69,699)	(14,613)
Total, Assets	34,135	32,077
Total, Liabilities	96,998	26,041
Net total, Assets		6,036
Net total, Liabilities	(62,863)
Coal supply agreement, Liabilities	38,441	5,615
Accrued Expenses and Other Current Liabilities [Member]
Acquired Finite-Lived Intangible Assets And Liabilities By Major Class [Line Items]
Coal supply agreement, Liabilities	38,441	5,615
Other Current Assets [Member]
Acquired Finite-Lived Intangible Assets And Liabilities By Major Class [Line Items]
Coal supply agreement, Assets	18,929	25,063
Other Noncurrent Liabilities [Member]
Acquired Finite-Lived Intangible Assets And Liabilities By Major Class [Line Items]
Coal supply agreement, Liabilities	58,557	20,426
Other Assets [Member]
Acquired Finite-Lived Intangible Assets And Liabilities By Major Class [Line Items]
Coal supply agreement, Assets	$ 15,206	$ 7,014

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Earnings Per Common Share

12 Months Ended

Dec. 31, 2011

Earnings Per Common Share [Abstract]

Earnings Per Common Share

20.  Earnings per Common Share

The following table provides the basis for earnings per share calculations by reconciling basic and diluted weighted average shares outstanding:

	Year Ended December 31
	2011	2010	2009
	(In thousands)
Weighted average shares outstanding:
Basic weighted average shares outstanding	190,086	162,398	150,963
Effect of common stock equivalents under incentive plans	819	812	309
Diluted weighted average shares outstanding	190,905	163,210	151,272

The effect of options to purchase 2.6 million, 2.5 million and 2.2 million shares of common stock were excluded from the calculation of diluted weighted average shares outstanding for the years ended December 31, 2011, 2010 and 2009, respectively, because the exercise price of these options exceeded the average market price of the Company's common stock for this period.

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Supplemental Condensed Consolidating Financial Information (Schedule Of Condensed Consolidating Statements Of Cash Flows) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash provided by (used in) operating activities	$ 642,242	$ 697,147	$ 382,980
Investing Activities
Acquisitions of businesses, net of cash acquired	(2,894,339)		(768,819)
Increase (decrease) in restricted cash	5,167
Capital expenditures	(540,936)	(314,657)	(323,150)
Proceeds from dispositions of property, plant and equipment	25,887	330	825
Additions to prepaid royalties	(29,957)	(27,355)	(26,755)
Purchases of investments and advances to affiliates	(61,909)	(46,185)	(10,925)
Consideration paid related to prior business acquisitions	(829)	(1,262)	(4,767)
Reimbursement of deposit on equipment			3,209
Cash used in investing activities	(3,496,916)	(389,129)	(1,130,382)
Financing Activities
Proceeds from the issuance of senior notes	2,000,000	500,000	584,784
Proceeds from the sale of common stock	1,267,933		326,452
Payments to retire debt	(605,178)	(505,627)
Net increase (decrease) in borrowings under lines of credit and commercial paper program	424,396	(196,549)	(85,815)
Net payments on other debt	5,334	82	(2,986)
Debt financing costs	(114,823)	(12,751)	(29,659)
Dividends paid	(80,748)	(63,373)	(54,969)
Issuance of common stock under incentive plans	2,316	1,764	84
Contribution from noncontrolling interest		891
Cash provided by (used in) financing activities	2,899,230	(275,563)	737,891
Increase (decrease) in cash and cash equivalents	44,556	32,455	(9,511)
Cash and cash equivalents, beginning of year	93,593	61,138	70,649
Cash and cash equivalents, end of year	138,149	93,593	61,138
Parent/Issuer [Member]
Cash provided by (used in) operating activities	(561,704)	(238,736)	(168,427)
Investing Activities
Acquisitions of businesses, net of cash acquired	(2,894,339)		(768,819)
Increase (decrease) in restricted cash	5,167
Capital expenditures	(12,809)	(4,814)	(2,940)
Purchases of investments and advances to affiliates	(633,534)	(40,421)	(8,000)
Consideration paid related to prior business acquisitions	(829)	(1,262)	(4,767)
Cash used in investing activities	(3,536,344)	(46,497)	(784,526)
Financing Activities
Proceeds from the issuance of senior notes	2,000,000	500,000	584,784
Proceeds from the sale of common stock	1,267,933		326,452
Net increase (decrease) in borrowings under lines of credit and commercial paper program	481,300	(120,000)	(85,000)
Net payments on other debt	5,334	82	(2,986)
Debt financing costs	(114,799)	(12,022)	(29,456)
Dividends paid	(80,748)	(63,373)	(54,969)
Issuance of common stock under incentive plans	2,316	1,764	84
Transactions with affiliates, net	584,374	(61,760)	200,562
Cash provided by (used in) financing activities	4,145,710	244,691	939,471
Increase (decrease) in cash and cash equivalents	47,662	(40,542)	(13,482)
Cash and cash equivalents, beginning of year	13,713	54,255	67,737
Cash and cash equivalents, end of year	61,375	13,713	54,255
Guarantor Subsidiaries [Member]
Cash provided by (used in) operating activities	801,201	503,766	338,956
Investing Activities
Capital expenditures	(353,441)	(198,243)	(194,756)
Proceeds from dispositions of property, plant and equipment	25,730	251	734
Additions to prepaid royalties	(25,982)	(24,381)	(23,991)
Purchases of investments and advances to affiliates	(33,553)	(5,764)	(2,925)
Cash used in investing activities	(387,246)	(228,137)	(220,938)
Financing Activities
Contributions from parent	605,178
Payments to retire debt	(605,178)
Transactions with affiliates, net	(413,687)	(275,629)	(118,015)
Cash provided by (used in) financing activities	(413,687)	(275,629)	(118,015)
Increase (decrease) in cash and cash equivalents	268		3
Cash and cash equivalents, beginning of year	64	64	61
Cash and cash equivalents, end of year	332	64	64
Non-Guarantor Subsidiaries [Member]
Cash provided by (used in) operating activities	402,745	432,117	212,451
Investing Activities
Capital expenditures	(174,686)	(111,600)	(125,454)
Proceeds from dispositions of property, plant and equipment	157	79	91
Additions to prepaid royalties	(3,975)	(2,974)	(2,764)
Reimbursement of deposit on equipment			3,209
Cash used in investing activities	(178,504)	(114,495)	(124,918)
Financing Activities
Payments to retire debt		(505,627)
Net increase (decrease) in borrowings under lines of credit and commercial paper program	(56,904)	(76,549)	(815)
Debt financing costs	(24)	(729)	(203)
Contribution from noncontrolling interest		891
Transactions with affiliates, net	(170,687)	337,389	(82,547)
Cash provided by (used in) financing activities	(227,615)	(244,625)	(83,565)
Increase (decrease) in cash and cash equivalents	(3,374)	72,997	3,968
Cash and cash equivalents, beginning of year	79,816	6,819	2,851
Cash and cash equivalents, end of year	76,442	79,816	6,819
Eliminations [Member]
Investing Activities
Purchases of investments and advances to affiliates	605,178
Cash used in investing activities	605,178
Financing Activities
Contributions from parent	(605,178)
Cash provided by (used in) financing activities	$ (605,178)

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Inventories (Details) (USD $)	Dec. 31, 2011	Dec. 31, 2010
Inventories [Abstract]
Coal	$ 206,517,000	$ 115,647,000
Repair parts and supplies	163,527,000	119,969,000
Work-in-process	7,446,000
Inventories	377,490,000	235,616,000
Repair parts and supplies stated net of an allowance for slow-moving and obsolete inventories	$ 13,100,000	$ 12,700,000

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Debt And Financing Arrangements (Tables)

12 Months Ended

Dec. 31, 2011

Debt And Financing Arrangements [Abstract]

Debt And Financing Arrangements

		December 31,
		2011			2010
		(In thousands)
Commercial paper	$		—	$		56,904
Indebtedness to banks under credit facilities			481,300			—
6.75% senior notes ($450.0 million face value) due July 1, 2013			450,971			451,618
8.75% senior notes ($600.0 million face value) due August 1, 2016			588,974			587,126
7.00% senior notes due June 15, 2019 at par			1,000,000			—
7.25% senior notes due October 1, 2020 at par			500,000			500,000
7.25% senior notes due June 15, 2021 at par			1,000,000			—
Other			21,903			14,093
			4,043,148			1,609,741
Less current maturities of debt and short-term borrowings			280,851			70,997
Long-term debt	$		3,762,297	$		1,538,744

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Fair Value Measurements

12 Months Ended

Dec. 31, 2011

Fair Value Measurements [Abstract]

Fair Value Measurements

13. Fair Value Measurements

The hierarchy of fair value measurements prioritizes the inputs to valuation techniques used to measure fair value. The levels of the hierarchy, as defined below, give the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities and the lowest priority to unobservable inputs.

·Level 1 is defined as observable inputs such as quoted prices in active markets for identical assets. Level 1 assets include available-for-sale equity securities and coal futures that are submitted for clearing on the New York Mercantile Exchange.

·Level 2 is defined as observable inputs other than Level 1 prices. These include quoted prices for similar assets or liabilities in an active market, quoted prices for identical assets and liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. The Company's level 2 assets and liabilities include commodity contracts (coal and heating oil) with fair values derived from quoted prices in over-the-counter markets or from prices received from direct broker quotes.

·Level 3 is defined as unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions. These include the Company's commodity option contracts (primarily coal and heating oil) valued using modeling techniques, such as Black-Scholes, that require the use of inputs, particularly volatility, that are rarely observable.

The table below sets forth, by level, the Company's financial assets and liabilities that are recorded at fair value in the accompanying condensed consolidated balance sheet:

	Fair Value at December 31, 2011
	Total		Level 1		Level 2		Level 3
	(In thousands)
Assets:
Investments in equity securities	$	7,540	$	7,540	$	—	$	—
Derivatives	24,129		12,361		1,450		10,318
Total assets	$	31,669	$	19,901	$	1,450	$	10,318
Liabilities:
Derivatives	$	7,828	$	—	$	3,721	$	4,107

The Company's contracts with certain of its counterparties allow for the settlement of contracts in an asset position with contracts in a liability position in the event of default or termination. For classification purposes, the Company records the net fair value of all the positions with these counterparties as a net asset or liability. Each level in the table above displays the underlying contracts according to their classification in the accompanying condensed consolidated balance sheet, based on this counterparty netting.

The following table summarizes the change in the fair values of financial instruments categorized as level 3.

		Year Ended December 31, 2011
	(In thousands)
Balance, beginning of period		$	9,183
Realized and unrealized losses recognized in earnings, net		(16,727		)
Realized and unrealized losses recognized in other comprehensive income, net		(4,122		)
Purchases		23,867
Issuances		(2,160		)
Settlements		(3,830		)
Balance, end of period		$	6,211

Net unrealized losses during the twelve months ended December 31, 2011 related to level 3 financial instruments held on December 31, 2011 were $13.1 million.

Fair Value of Long-Term Debt

At December 31, 2011 and December 31, 2010, the fair value of the Company's senior notes and other long-term debt, including amounts classified as current, was $4.2 billion and $1.7 billion, respectively. Fair values are based upon observed prices in an active market when available or from valuation models using market information.

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Capital Stock (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended		0 Months Ended		12 Months Ended	0 Months Ended	6 Months Ended
	Dec. 31, 2011	Dec. 31, 2009	Jul. 08, 2011 ICG [Member]	Jun. 08, 2011 ICG [Member]	Dec. 31, 2011 ICG [Member]	Aug. 06, 2009 Jacobs Ranch Mining Operations [Member]	Jul. 31, 2009 Jacobs Ranch Mining Operations [Member]	Jul. 31, 2011 Jacobs Ranch Mining Operations [Member]
Common stock issued	48,705,000	19,550,000	700,000	48,000,000		2,550,000	17,000,000
Common stock public offering price				$ 27.00				$ 17.50
Proceeds from the sale of common stock	$ 1,267,933	$ 326,452	$ 18,400		$ 1,250,000	$ 326,500
Stock repurchase authorized number	14,000,000
Outstanding shares available for repurchase	10,925,800

CORRESP

April 23, 2012

Mr. John Reynolds

Assistant Director

Division of Corporation Finance

Securities and Exchange Commission

100 F Street, N.E.

Washington, DC 20549

Re:	Arch Coal, Inc.
	Form 10-K for Fiscal Year Ended December 31, 2011
	Filed February 29, 2012
	File No. 001-13105

Dear Mr. Reynolds:

We are providing this letter in response to the comments of the staff of the Securities and Exchange Commission (the “Staff”) contained in your letter dated April 10, 2012 regarding the Annual Report on Form 10-K filed by Arch Coal, Inc. (“Arch Coal”) for Arch Coal’s fiscal year ended December 31, 2011 (the “Form 10-K”).  Set forth below are the Staff’s comments and our responses.  We also call to the Staff’s attention that Arch Coal has filed Amendment No. 1 to the Form 10-K on the date of this letter.

Form 10-K for Fiscal Year Ended December 31, 2011

Notes to the Consolidated Financial Statements

26.  Supplemental Condensed Consolidating Financial Information, page F-47

COMMENT NO. 1:

We have reviewed your response to our prior comment one noting that word “unaudited” was inadvertently utilized.  Please amend your disclosure to clearly present the condensed consolidated financial information as audited.

RESPONSE:

In response to the Staff’s comment, we have filed Amendment No. 1 to the Form 10-K (“Amendment No. 1”) on the date of this letter.  In Amendment No. 1, we have amended our disclosure in the Form 10-K to remove the word “unaudited” from Note 26 to our audited