Matters Related to the Bankruptcy of Patriot Coal Corporation (Patriot) (Notes)	3 Months Ended
Mar. 31, 2017
Matters Related to the Bankruptcy of Patriot Coal Corporation (Patriot) [Abstract]
Matters Related to the Bankruptcy of Patriot Coal Corporation (Patriot) [Table Text Block]	Matters Related to the Bankruptcy of Patriot Coal Corporation In 2012, Patriot filed voluntary petitions for relief under Chapter 11 of Title 11 of the U.S. Code. In 2013, the Company entered into a definitive settlement agreement (2013 Agreement) with Patriot and the UMWA, on behalf of itself, its represented Patriot employees and its represented Patriot retirees, to resolve all then disputed issues related to Patriot’s bankruptcy. In May 2015, Patriot again filed voluntary petitions for relief under Chapter 11 of Title 11 of the U.S. Code in the Eastern District of Virginia and subsequently initiated a process to sell some or all of their assets to qualified bidders. On October 9, 2015, Patriot's bankruptcy court entered an order confirming Patriot's plan of reorganization, which provides, among other things, for the sale of substantially all of Patriot's assets to two different buyers. Credit Support As part of the 2013 Agreement, the Company provided certain credit support to Patriot. The Company has recorded $20.9 million of credit support provided to Patriot as a liability on the Company's condensed consolidated balance sheet as of March 31, 2017, of which $15.7 million was supported by letters of credit. Black Lung Occupational Disease Liabilities Patriot has federal and state black lung occupational disease liabilities related to workers employed in periods prior to Patriot’s spin-off from the Company in 2007. Upon spin-off, Patriot indemnified the Company against any claim relating to these liabilities, which amounted to approximately $150 million at that time. The indemnification included any claim made by the U.S. Department of Labor (DOL) against the Company with respect to these obligations as a potentially liable operator under the Federal Coal Mine Health and Safety Act of 1969. The 2013 Agreement included Patriot’s affirmance of indemnities provided in the spin-off agreements, including the indemnity relating to such black lung liabilities. By statute, the Company remains secondarily liable for the black lung liabilities related to Patriot’s workers employed by former subsidiaries of the Company. Whether the Company will ultimately be required to fund certain of those obligations in the future as a result of Patriot’s May 2015 bankruptcy remains uncertain. The amount of the liability at March 31, 2017 was $124.1 million. While the Company has recorded a liability, it intends to review each claim on a case-by-case basis and contest liability as appropriate. The amount of the Company's recorded liability reflects only Patriot workers employed by former subsidiaries of the Company that are presently retired, disabled or otherwise not actively employed. The Company cannot reliably estimate the potential liabilities for Patriot's workers employed by former subsidiaries of the Company that are presently active in the workforce because of the potential for such workers to continue to work for another coal operator that is a going concern. The Company's accounting for the black lung liabilities related to Patriot is based on an interpretation of applicable statutes. Management believes that there exist inconsistencies among the applicable statutes, regulations promulgated under those statutes and the Department of Labor’s interpretative guidance. The Company may seek clarification from the Department of Labor regarding these inconsistencies and the accounting for these liabilities could change in the future depending on the Department of Labor’s responses to inquiries. UMWA VEBA Payments In connection with the 2013 Agreement, the Company was required to provide total payments of $310.0 million, payable over four years through 2017, to partially fund the newly established voluntary employee beneficiary association (VEBA) and settle all Patriot and UMWA claims involving the Patriot bankruptcy. After making scheduled payments to Patriot and the VEBA amounting to $165 million through 2015, the parties agreed to a settlement of the Company’s obligations for payment of the remaining VEBA payments (2016 Settlement Agreement), which was approved by the Missouri and Virginia Bankruptcy Courts in January 2016. Under this settlement, the Company agreed to pay $75 million to the VEBA, payable in equal monthly installments of $7.5 million beginning on January 4, 2016. The remaining monthly installments were due at the beginning of each successive month ending October 2016, and the obligations were supported in full by a letter of credit. As a result of the Company’s Chapter 11 Cases, the Company’s obligations to the VEBA under the 2016 Settlement Agreement were satisfied by monthly draws on the letter of credit by the VEBA trustees. As part of the settlement, the Company recognized a gain of $68.1 million during the three months ended March 31, 2016, which was classified in "Operating costs and expenses" in the unaudited condensed consolidated statement of operations and is included in the Company's Corporate and Other segment results. UMWA 1974 Pension Plan (UMWA Plan) Litigation On July 16, 2015, a lawsuit was filed by the UMWA Plan, the UMWA 1974 Pension Trust (Trust) and the Trustees of the UMWA Plan and Trust (Trustees) in the United States District Court for the District of Columbia, against PEC, PHC, a subsidiary of the Company, and Arch Coal, Inc. (Arch). The plaintiffs sought, pursuant to ERISA and the Multiemployer Pension Plan Amendments Act of 1980 (MPPAA), a declaratory judgment that the defendants were obligated to arbitrate any opposition to the Trustees’ determination that the defendants have statutory withdrawal liability as a result of the 2015 Patriot bankruptcy. The plaintiffs' lawsuit claimed that the defendants' withdrawal liability would result in at least $767 million owed to the UMWA Plan. After a legal and arbitration process and with the approval of the Bankruptcy Court, on January 25, 2017, the UMWA Plan and the Debtors agreed to a settlement of the claim whereby the UMWA Plan will be entitled to $75 million to be paid by the Company as follows: $5 million which was paid on the Effective Date, $10 million paid 90 days after the Effective Date, $15 million paid one year after the previous payment and $15 million per year for the following three years. In exchange, the UMWA Plan will release PEC and all members of the PEC control group (as defined under ERISA) from any cause of action regarding withdrawal liability. In connection with the settlement, the Company recorded a liability representing the present value of the installments of $54.3 million and recognized an equivalent charge to "Loss from discontinued operations, net of income taxes" during 2016. The accreted balance of the liability was $56.0 million at March 31, 2017.

Matters Related to the Bankruptcy of Patriot Coal Corporation

In 2012, Patriot filed voluntary petitions for relief under Chapter 11 of Title 11 of the U.S. Code. In 2013, the Company entered into a definitive settlement agreement (2013 Agreement) with Patriot and the UMWA, on behalf of itself, its represented Patriot employees and its represented Patriot retirees, to resolve all then disputed issues related to Patriot’s bankruptcy. In May 2015, Patriot again filed voluntary petitions for relief under Chapter 11 of Title 11 of the U.S. Code in the Eastern District of Virginia and subsequently initiated a process to sell some or all of their assets to qualified bidders. On October 9, 2015, Patriot's bankruptcy court entered an order confirming Patriot's plan of reorganization, which provides, among other things, for the sale of substantially all of Patriot's assets to two different buyers.

Credit Support

As part of the 2013 Agreement, the Company provided certain credit support to Patriot. The Company has recorded $20.9 million of credit support provided to Patriot as a liability on the Company's condensed consolidated balance sheet as of March 31, 2017, of which $15.7 million was supported by letters of credit.

Black Lung Occupational Disease Liabilities

Patriot has federal and state black lung occupational disease liabilities related to workers employed in periods prior to Patriot’s spin-off from the Company in 2007. Upon spin-off, Patriot indemnified the Company against any claim relating to these liabilities, which amounted to approximately $150 million at that time. The indemnification included any claim made by the U.S. Department of Labor (DOL) against the Company with respect to these obligations as a potentially liable operator under the Federal Coal Mine Health and Safety Act of 1969. The 2013 Agreement included Patriot’s affirmance of indemnities provided in the spin-off agreements, including the indemnity relating to such black lung liabilities.

By statute, the Company remains secondarily liable for the black lung liabilities related to Patriot’s workers employed by former subsidiaries of the Company. Whether the Company will ultimately be required to fund certain of those obligations in the future as a result of Patriot’s May 2015 bankruptcy remains uncertain. The amount of the liability at March 31, 2017 was $124.1 million. While the Company has recorded a liability, it intends to review each claim on a case-by-case basis and contest liability as appropriate. The amount of the Company's recorded liability reflects only Patriot workers employed by former subsidiaries of the Company that are presently retired, disabled or otherwise not actively employed. The Company cannot reliably estimate the potential liabilities for Patriot's workers employed by former subsidiaries of the Company that are presently active in the workforce because of the potential for such workers to continue to work for another coal operator that is a going concern.

The Company's accounting for the black lung liabilities related to Patriot is based on an interpretation of applicable statutes. Management believes that there exist inconsistencies among the applicable statutes, regulations promulgated under those statutes and the Department of Labor’s interpretative guidance. The Company may seek clarification from the Department of Labor regarding these inconsistencies and the accounting for these liabilities could change in the future depending on the Department of Labor’s responses to inquiries.

UMWA VEBA Payments

In connection with the 2013 Agreement, the Company was required to provide total payments of $310.0 million, payable over four years through 2017, to partially fund the newly established voluntary employee beneficiary association (VEBA) and settle all Patriot and UMWA claims involving the Patriot bankruptcy. After making scheduled payments to Patriot and the VEBA amounting to $165 million through 2015, the parties agreed to a settlement of the Company’s obligations for payment of the remaining VEBA payments (2016 Settlement Agreement), which was approved by the Missouri and Virginia Bankruptcy Courts in January 2016. Under this settlement, the Company agreed to pay $75 million to the VEBA, payable in equal monthly installments of $7.5 million beginning on January 4, 2016. The remaining monthly installments were due at the beginning of each successive month ending October 2016, and the obligations were supported in full by a letter of credit. As a result of the Company’s Chapter 11 Cases, the Company’s obligations to the VEBA under the 2016 Settlement Agreement were satisfied by monthly draws on the letter of credit by the VEBA trustees. As part of the settlement, the Company recognized a gain of $68.1 million during the three months ended March 31, 2016, which was classified in "Operating costs and expenses" in the unaudited condensed consolidated statement of operations and is included in the Company's Corporate and Other segment results.

UMWA 1974 Pension Plan (UMWA Plan) Litigation

On July 16, 2015, a lawsuit was filed by the UMWA Plan, the UMWA 1974 Pension Trust (Trust) and the Trustees of the UMWA Plan and Trust (Trustees) in the United States District Court for the District of Columbia, against PEC, PHC, a subsidiary of the Company, and Arch Coal, Inc. (Arch). The plaintiffs sought, pursuant to ERISA and the Multiemployer Pension Plan Amendments Act of 1980 (MPPAA), a declaratory judgment that the defendants were obligated to arbitrate any opposition to the Trustees’ determination that the defendants have statutory withdrawal liability as a result of the 2015 Patriot bankruptcy. The plaintiffs' lawsuit claimed that the defendants' withdrawal liability would result in at least $767 million owed to the UMWA Plan. After a legal and arbitration process and with the approval of the Bankruptcy Court, on January 25, 2017, the UMWA Plan and the Debtors agreed to a settlement of the claim whereby the UMWA Plan will be entitled to $75 million to be paid by the Company as follows: $5 million which was paid on the Effective Date, $10 million paid 90 days after the Effective Date, $15 million paid one year after the previous payment and $15 million per year for the following three years. In exchange, the UMWA Plan will release PEC and all members of the PEC control group (as defined under ERISA) from any cause of action regarding withdrawal liability. In connection with the settlement, the Company recorded a liability representing the present value of the installments of $54.3 million and recognized an equivalent charge to "Loss from discontinued operations, net of income taxes" during 2016. The accreted balance of the liability was $56.0 million at March 31, 2017.