1.0.0.3 false Concentration of Credit Risk and Major Customers false 1 $ false false USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDEPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 2 Concentration of Credit Risk and Major Customers [Abstract] 0 anr_ConcentrationOfCreditRiskAndMajorCustomersAbstract anr false na duration string Concentration of Credit Risk and Major Customers. false false false false false true false false false 1 false false 0 0 false false Concentration of Credit Risk and Major Customers. false 3 Concentration of Credit Risk and Major Customers 1 us-gaap_ConcentrationRiskDisclosureTextBlock us-gaap true na duration string No definition available. false false false false false false false false false 1 false false 0 0   <div style="font-family: 'Times New Roman',Times,serif; margin-left: .25in; width: 7.20in"> <div align="left" style="font-size: 10pt; margin-top: 10pt"><b>(21) Concentration of Credit Risk and Major Customers</b> </div> <div align="left" style="font-size: 10pt; margin-top: 10pt; text-indent: 4%">The Company markets its coal principally to electric utilities in the United States and international and domestic steel producers. As of December 31, 2009 and 2008, trade accounts receivable from electric utilities totaled approximately $86,270 and $59,398, respectively. Credit is extended based on an evaluation of the customer’s financial condition and collateral is generally not required. Credit losses are provided for in the consolidated financial statements and historically have been minimal. The Company is committed under long-term contracts to supply coal that meets certain quality requirements at specified prices. The prices for some multi-year contracts are adjusted based on economic indices or the contract may include year-to-year specified price changes. Qualities and volume for coal are stipulated in coal supply agreements, and may vary from year to year within certain limits at the option of the customer. For the years ended December 31, 2009, 2008, and 2007, the Company’s 10 largest customers accounted for approximately 47%, 54% and 42% of <i>Total revenues</i>, respectively. Sales to the Company’s largest customer accounted for approximately 12% of <i>Total revenues </i>for the years ended December 31, 2009 and 2008 and less than 10% for the year ended December 31, 2007. </div> </div>  <!-- Begin Block Tagged Note false false No definition available. No authoritative reference available. false false 1 2 false UnKnown UnKnown UnKnown false true