Impairment Charges (Notes)	9 Months Ended
Sep. 30, 2014
Restructuring Costs and Asset Impairment Charges [Abstract]
Restructuring, Impairment, and Other Activities Disclosure	5. Impairment Charges In the face of weak coal markets, the Company idled a higher-cost mining complex in the third quarter of 2014 in order to concentrate on metallurgical coal production from its lowest-cost and highest-margin operations. Closure charges of $5.1 million were recognized during the three months ended September 30, 2014 relating to the idling. As a result of the weak thermal coal markets in Appalachia, the Company assessed in the third quarter of 2013 whether the carrying values of certain assets were recoverable through future cash flows. The Company determined that the carrying amounts of certain assets associated with the Hazard mining complex in Kentucky and the Company's ADDCAR subsidiary, which manufactures and sells its patented highwall mining system, could not be recovered through future cash flows expected to be generated from use of the assets and their ultimate disposal. An impairment loss of $142.8 million was recognized to write the carrying value of the assets to their fair value of $71.3 million. During the second quarter of 2013, Tenaska Trailblazer Partners, LLC announced that it was discontinuing its development plans for the Trailblazer Energy Center in Texas. As a result, the Company recorded a $20.5 million impairment charge, which consisted of its 35% equity investment of $15.3 million and a $5.2 million receivable balance related to reimbursements for development work. The Company recorded an impairment charge of $57.7 million in the third quarter of 2013 related to its investment in DKRW Advanced Fuels, LLC ("DKRW"), a company engaged in developing coal-to-liquids facilities. DKRW had previously entered into an Engineering, Procurement and Construction Agreement with a Chinese company to construct and commission the Medicine Bow coal-to-liquids facility. The project did not progress to the next stage of development, and the impairment charge included the Company's 24% equity investment of $13.7 million and a $44.0 million loan receivable balance. The impairment and closure charges are included on the line "Asset impairment and mine closure costs" in the condensed consolidated statement of operations.

5. Impairment Charges

In the face of weak coal markets, the Company idled a higher-cost mining complex in the third quarter of 2014 in order to concentrate on metallurgical coal production from its lowest-cost and highest-margin operations. Closure charges of $5.1 million were recognized during the three months ended September 30, 2014 relating to the idling.

As a result of the weak thermal coal markets in Appalachia, the Company assessed in the third quarter of 2013 whether the carrying values of certain assets were recoverable through future cash flows. The Company determined that the carrying amounts of certain assets associated with the Hazard mining complex in Kentucky and the Company's ADDCAR subsidiary, which manufactures and sells its patented highwall mining system, could not be recovered through future cash flows expected to be generated from use of the assets and their ultimate disposal. An impairment loss of $142.8 million was recognized to write the carrying value of the assets to their fair value of $71.3 million.

During the second quarter of 2013, Tenaska Trailblazer Partners, LLC announced that it was discontinuing its development plans for the Trailblazer Energy Center in Texas. As a result, the Company recorded a $20.5 million impairment charge, which consisted of its 35% equity investment of $15.3 million and a $5.2 million receivable balance related to reimbursements for development work.

The Company recorded an impairment charge of $57.7 million in the third quarter of 2013 related to its investment in DKRW Advanced Fuels, LLC ("DKRW"), a company engaged in developing coal-to-liquids facilities. DKRW had previously entered into an Engineering, Procurement and Construction Agreement with a Chinese company to construct and commission the Medicine Bow coal-to-liquids facility. The project did not progress to the next stage of development, and the impairment charge included the Company's 24% equity investment of $13.7 million and a $44.0 million loan receivable balance.

The impairment and closure charges are included on the line "Asset impairment and mine closure costs" in the condensed consolidated statement of operations.