Resource Management and Other Commercial Events (Notes)	9 Months Ended
Sep. 30, 2014
Resource Management, Acquisitions and Other Commercial Events [Abstract]
Resource Management And Other Commercial Events [Text Block]	Resource Management and Other Commercial Events Coal Supply Agreement During April 2014, the Company finalized pricing under a sales agreement for one of its Western U.S. Mining segment customers. As a result of that agreement, the Company recognized additional contract revenue and sales-related expenses totaling $33.5 million and $6.4 million, respectively, during the nine months ended September 30, 2014 and will continue to realize higher prices for coal supplied pursuant to that agreement in 2014. Divestitures In January 2014, the Company sold a non-strategic exploration tenement asset in Australia in exchange for cash proceeds of $62.6 million. The Company had previously recorded an impairment charge in December 2013 to write down the carrying value of that asset to its fair value. Accordingly, there was no gain or loss recognized on the disposal during the nine months ended September 30, 2014. In June 2013, the Company sold non-strategic coal reserves and surface lands located in Kentucky in exchange for cash proceeds of $35.0 million and short-term notes receivable totaling $35.0 million, which notes were subsequently collected in December 2013. The Company recognized a gain on sale of $40.3 million related to the transaction, which was classified in "Net gain on disposal or exchange of assets" in the unaudited condensed consolidated statement of operations for the nine months ended September 30, 2013.

Resource Management and Other Commercial Events

Coal Supply Agreement

During April 2014, the Company finalized pricing under a sales agreement for one of its Western U.S. Mining segment customers. As a result of that agreement, the Company recognized additional contract revenue and sales-related expenses totaling $33.5 million and $6.4 million, respectively, during the nine months ended September 30, 2014 and will continue to realize higher prices for coal supplied pursuant to that agreement in 2014.

Divestitures

In January 2014, the Company sold a non-strategic exploration tenement asset in Australia in exchange for cash proceeds of $62.6 million. The Company had previously recorded an impairment charge in December 2013 to write down the carrying value of that asset to its fair value. Accordingly, there was no gain or loss recognized on the disposal during the nine months ended September 30, 2014.

In June 2013, the Company sold non-strategic coal reserves and surface lands located in Kentucky in exchange for cash proceeds of $35.0 million and short-term notes receivable totaling $35.0 million, which notes were subsequently collected in December 2013. The Company recognized a gain on sale of $40.3 million related to the transaction, which was classified in "Net gain on disposal or exchange of assets" in the unaudited condensed consolidated statement of operations for the nine months ended September 30, 2013.