Peabody Energy (BTU) 10-K25 Feb 152014 FY Annual reportFinancial data

Company Profile

Document_and_Entity_Informatio

Document and Entity Information Document Document (USD $)	12 Months Ended
In Billions, except Share data, unless otherwise specified	Dec. 31, 2014	Feb. 20, 2015	Jun. 30, 2014
Document Information [Line Items]
Entity Registrant Name	PEABODY ENERGY CORP
Entity Central Index Key	1064728
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Amendment Flag	FALSE
Entity Common Stock, Shares Outstanding		274,817,605
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$4.40

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues
Sales	$6,132.70	$6,380	$7,041.70
Other revenues	659.5	633.7	1,035.80
Total revenues	6,792.20	7,013.70	8,077.50
Costs and expenses
Operating costs and expenses (exclusive of items shown separately below)	5,716.90	5,729.10	5,932.70
Depreciation, depletion and amortization	655.7	740.3	663.4
Asset retirement obligation expenses	81	66.5	67
Selling and administrative expenses	227.1	244.2	268.8
Restructuring and pension settlement charges	26	11.9	0
Other operating (income) loss:
Net gain on disposal or exchange of assets	-41.4	-52.6	-17.1
Asset impairment and mine closure costs	154.4	528.3	929
Settlement charges related to the Patriot bankruptcy reorganization	0	30.6	0
Loss from equity affiliates	107.6	40.2	61.2
Operating (loss) profit	-135.1	-324.8	172.5
Interest expense	428.2	425.2	405.6
Interest income	-15.4	-15.7	-24.5
Loss from continuing operations before income taxes	-547.9	-734.3	-208.6
Income tax provision (benefit)	201.2	-448.3	262.3
Loss from continuing operations, net of income taxes	-749.1	-286	-470.9
Loss from discontinued operations, net of income taxes	-28.2	-226.6	-104.2
Net loss	-777.3	-512.6	-575.1
Less: Net income attributable to noncontrolling interests	9.7	12.3	10.6
Net loss attributable to common stockholders	($787)	($524.90)	($585.70)
Loss From Continuing Operations
Basic loss per share	($2.83)	($1.12)	($1.80)
Diluted loss per share	($2.83)	($1.12)	($1.80)
Net Loss Attributable to Common Stockholders
Basic loss per share	($2.94)	($1.97)	($2.19)
Diluted loss per share	($2.94)	($1.97)	($2.19)
Dividends declared per share	$0.34	$0.34	$0.34

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended								12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net loss	($513)	($149)	($71.20)	($44.10)	($561.20)	($19.10)	$87.10	($19.40)	($777.30)	($512.60)	($575.10)
Net change in unrealized (losses) gains on available-for-sale securities (net of respective tax (benefit) provision of ($0.5), $0.5 and $4.0)
Unrealized holding losses on available-for-sale securities									-3.7	-12.3	-15.5
Reclassification for realized losses included in net loss									2.9	12.8	22.5
Net change in unrealized (losses) gains on available-for-sale securities									-0.8	0.5	7
Net unrealized (losses) gains on cash flow hedges (net of respective tax benefit of ($54.6), ($300.0) and ($3.9))
(Decrease) increase in fair value of cash flow hedges									-195	-333.6	350.4
Reclassification for realized gains included in net loss									-10.2	-209.6	-298.6
Net unrealized (losses) gains on cash flow hedges									-205.2	-543.2	51.8
Postretirement plans and workers' compensation obligations (net of respective tax (benefit) provision of ($10.3), $121.7 and $43.9)
Prior service credit (cost) for the period									11.4	-1.4	20.1
Net actuarial (loss) gain for the period									-142.7	110.9	0
Amortization of actuarial loss and prior service cost included in net loss									32.7	95.7	55.4
Postretirement plans and workers' compensation obligations									-98.6	205.2	75.5
Foreign currency translation adjustment									-41	-92.7	19.1
Other comprehensive (loss) income, net of income taxes									-345.6	-430.2	153.4
Comprehensive loss									-1,122.90	-942.8	-421.7
Less: Comprehensive income attributable to noncontrolling interests									9.7	12.3	10.6
Comprehensive loss attributable to common stockholders									($1,132.60)	($955.10)	($432.30)

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Current assets
Cash and cash equivalents	$298	$444
Accounts receivable, net of allowance for doubtful accounts of $5.8 at December 31, 2014 and $7.4 at December 31, 2013	563.1	557.9
Inventories	406.5	506.7
Assets from coal trading activities, net	57.6	36.1
Deferred income taxes	80	66.4
Other current assets	305.8	381.6
Total current assets	1,711	1,992.70
Property, plant, equipment and mine development, net	10,577.30	11,082.50
Deferred income taxes	0.7	7.8
Investments and other assets	902.1	1,050.40
Total assets	13,191.10	14,133.40
Current liabilities
Current maturities of long-term debt	21.2	31.7
Liabilities from coal trading activities, net	32.7	6.1
Accounts payable and accrued expenses	1,809.20	1,764
Total current liabilities	1,863.10	1,801.80
Long-term debt, less current maturities	5,965.60	5,970.70
Deferred income taxes	89.1	40.9
Asset retirement obligations	722.3	691.8
Accrued postretirement benefit costs	781.9	684
Other noncurrent liabilities	1,042.60	996.3
Total liabilities	10,464.60	10,185.50
Stockholders' equity
Additional paid-in capital	2,383.30	2,340
Treasury shares, at cost - 14.0 shares as of December 31, 2014 and 13.8 shares as of December 31, 2013	-467.1	-464.7
Retained earnings	1,570.50	2,449.80
Accumulated other comprehensive loss	-764.8	-419.2
Peabody Energy Corporation's stockholders' equity	2,724.80	3,908.70
Noncontrolling interests	1.7	39.2
Total stockholders' equity	2,726.50	3,947.90
Total liabilities and stockholders' equity	13,191.10	14,133.40
Preferred Stock [Member]
Stockholders' equity
Preferred Stock	0	0
Perpetual Preferred Stock [Member]
Stockholders' equity
Preferred Stock	0	0
Series Common Stock [Member]
Stockholders' equity
Common Stock	0	0
Common Stock [Member]
Stockholders' equity
Common Stock	$2.90	$2.80

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash Flows From Operating Activities
Net loss	($777.30)	($512.60)	($575.10)
Loss from discontinued operations, net of income taxes	28.2	226.6	104.2
Loss from continuing operations, net of income taxes	-749.1	-286	-470.9
Adjustments to reconcile loss from continuing operations, net of income taxes to net cash provided by operating activities:
Depreciation, depletion and amortization	655.7	740.3	663.4
Noncash interest expense	23.6	32	20.7
Deferred income taxes	231.9	-434.1	-2.6
Share-based compensation	46.8	50.9	45.4
Asset impairment and mine closure costs	154.4	528.3	929
Settlement charges related to the Patriot bankruptcy reorganization	0	30.6	0
Net gain on disposal or exchange of assets	-41.4	-52.6	-17.1
Loss from equity affiliates	107.6	40.2	61.2
Monetization of foreign currency hedge positions	0	0	151.8
Gains on previously monetized foreign currency hedge positions	-136.9	0	0
Changes in current assets and liabilities:
Accounts receivable	55.4	104.8	285.3
Change in receivable from accounts receivable securitization program	-70	75	-125
Inventories	104.9	39.9	-112.9
Net assets from coal trading activities	-10.1	-83.7	125.2
Other current assets	7.7	3.1	10.3
Accounts payable and accrued expenses	-29.2	-108.9	-87.8
Asset retirement obligations	60.3	45.5	46.4
Workers' compensation obligations	2.2	7.3	9.4
Accrued postretirement benefit costs	9.6	17	38.9
Accrued pension costs	28.3	51.8	32.4
Other, net	-10.7	-21.3	-3.3
Net cash provided by continuing operations	441	780.1	1,599.80
Net cash used in discontinued operations	-104.4	-57.7	-84.7
Net cash provided by operating activities	336.6	722.4	1,515.10
Cash Flows From Investing Activities
Additions to property, plant, equipment and mine development	-194.4	-328.4	-986
Changes in accrued expenses related to capital expenditures	-16.6	-120.7	104.7
Federal coal lease expenditures	-276.7	-276.8	-276.5
Investment in Prairie State Energy Campus	0	0	-10.7
Proceeds from disposal of assets, net of notes receivable	203.7	178.3	147.9
Purchases of debt and equity securities	-15.1	-22.8	-46.7
Proceeds from sales and maturities of debt and equity securities	13.5	22.9	46.4
Purchases of short-term investments	0	0	-4.8
Maturity of short-term investments	0	4.8	0
Contributions to joint ventures	-529.8	-671.7	-824
Distributions from joint ventures	534.2	722.9	823
Advances to related parties	-33.7	-42.1	-148
Repayment of loans from related parties	5.4	25.2	110.8
Other, net	-5	-5.8	-6.2
Net cash used in continuing operations	-314.5	-514.2	-1,070.10
Net cash used in discontinued operations	0	-1.5	-22
Net cash used in investing activities	-314.5	-515.7	-1,092.10
Cash Flows From Financing Activities
Proceeds from long-term debt	1.1	1,188	0.8
Repayments of long-term debt	-21	-1,390.20	-415.8
Payment of deferred financing costs	-10.1	-22.8	-6.9
Dividends paid	-92.3	-91.7	-91.9
Common stock repurchase	0	0	-99.9
Excess tax benefit related to share-based compensation	0	0	8.3
Acquisition of MCG Coal Holdings Pty Ltd noncontrolling interests	0	0	-49.8
Restricted cash for distributions to noncontrolling interests	-42.5	0	0
Other, net	-3.3	-4.8	-8.1
Net cash used in financing activities	-168.1	-321.5	-663.3
Net change in cash and cash equivalents	-146	-114.8	-240.3
Cash and cash equivalents at beginning of year	444	558.8	799.1
Cash and cash equivalents at end of year	$298	$444	$558.80

Consolidated_Statements_of_Cha

Consolidated Statements of Changes in Stockholders' Equity (USD $)	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Noncontrolling Interests [Member]	Equity Award
In Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Noncontrolling Interests [Member]	Equity Award
Beginning Balance at Dec. 31, 2011	$5,515.80	$2.80	$2,234	($353.30)	$3,744	($142.40)	$30.70
Net loss	-575.1
Net loss attributable to common stockholders	-585.7				-585.7
Less: Net income attributable to noncontrolling interests	10.6						10.6
Net change in unrealized gains (losses) on available-for-sale securities, net of tax	7					7
Net unrealized gains (losses) on cash flow hedges	51.8					51.8
Postretirement plans and workers' compensation obligations	75.5					75.5
Foreign currency translation adjustment	19.1					19.1
Dividends paid	-91.9				-91.9
Share-based compensation	45.4		45.4					45.4
Excess (write-off) tax benefits related to share-based compensation	8.3		8.3
Stock options exercised	2.4		2.4
Employee stock purchases	7		7
Repurchase of employee common stock relinquished for tax withholding	-8.4		0	-8.4
Common stock repurchase	-99.9			-99.9			0
MCG Coal Holdings Pty Ltd noncontrolling interests at conversion	39						39
Acquisition of MCG Coal Holdings Pty Ltd noncontrolling interests	-49.8		-10.8				-39
Distributions to noncontrolling interests	-7.4						-7.4
Dividend payable to noncontrolling interests	0
Ending Balance at Dec. 31, 2012	4,938.80	2.8	2,286.30	-461.6	3,066.40	11	33.9
Net loss	-512.6
Net loss attributable to common stockholders	-524.9				-524.9
Less: Net income attributable to noncontrolling interests	12.3						12.3
Net change in unrealized gains (losses) on available-for-sale securities, net of tax	0.5					0.5
Net unrealized gains (losses) on cash flow hedges	-543.2					-543.2
Postretirement plans and workers' compensation obligations	205.2					205.2
Foreign currency translation adjustment	-92.7					-92.7
Dividends paid	-91.7				-91.7
Share-based compensation	50.9		50.9					50.9
Excess (write-off) tax benefits related to share-based compensation	-4.5	0	-4.5	0	0	0	0
Stock options exercised	1		1
Employee stock purchases	6.3		6.3
Repurchase of employee common stock relinquished for tax withholding	-3.1			-3.1
Common stock repurchase	0
Distributions to noncontrolling interests	-7						-7
Dividend payable to noncontrolling interests	0
Ending Balance at Dec. 31, 2013	3,947.90	2.8	2,340	-464.7	2,449.80	-419.2	39.2
Net loss	-777.3
Net loss attributable to common stockholders	-787				-787
Less: Net income attributable to noncontrolling interests	9.7						9.7
Net change in unrealized gains (losses) on available-for-sale securities, net of tax	-0.8					-0.8
Net unrealized gains (losses) on cash flow hedges	-205.2					-205.2
Postretirement plans and workers' compensation obligations	-98.6					-98.6
Foreign currency translation adjustment	-41					-41
Dividends paid	-92.3				-92.3
Share-based compensation	46.8		46.1					46.1
Excess (write-off) tax benefits related to share-based compensation	-8.3		-8.3
Stock options exercised	0.5		0.5
Employee stock purchases	5.1		5.1
Employee stock grants	0	0.1	-0.1	0	0	0	0
Repurchase of employee common stock relinquished for tax withholding	-2.4			-2.4
Common stock repurchase	0
Distributions to noncontrolling interests	-4.7	0	0	0	0	0	-4.7
Dividend payable to noncontrolling interests	-42.5	0	0	0	0	0	-42.5
Ending Balance at Dec. 31, 2014	$2,726.50	$2.90	$2,383.30	($467.10)	$1,570.50	($764.80)	$1.70

Comprehensive_Income_Parenthet

Comprehensive Income Parenthetical (Parentheticals) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net change in unrealized (losses) gains on available-for-sale securities, tax (benefit) provision	($0.50)	$0.50	$4
Net unrealized (losses) gains on cash flow hedges, tax benefit	-54.6	-300	-3.9
Postretirement plans and workers' compensation obligations, tax (benefit) provision	($10.30)	$121.70	$43.90

Balance_Sheet_Parenthetical_Pa

Balance Sheet Parenthetical (Parentheticals) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Current assets
Allowance for doubtful accounts	$5.80	$7.40
Stockholders' equity
Preferred Stock, par value	$0.01
Common Stock, par value	$0.01
Common Stock, shares authorized	800
Common Stock, shares outstanding	271.7	270.1
Treasury Stock, shares	14	13.8
Preferred Stock [Member]
Stockholders' equity
Preferred Stock, par value	$0.01	$0.01
Preferred Stock, shares authorized	10	10
Preferred Stock, shares issued	0	0
Preferred Stock, shares outstanding	0	0
Perpetual Preferred Stock Member
Stockholders' equity
Preferred Stock, shares authorized	0.8	0.8
Preferred Stock, shares issued	0	0
Preferred Stock, shares outstanding	0	0
Series Common Stock Member
Stockholders' equity
Common Stock, par value	$0.01	$0.01
Common Stock, shares authorized	40	40
Common Stock, shares issued	0	0
Common Stock, shares outstanding	0	0
Common Stock [Member]
Stockholders' equity
Common Stock, par value	$0.01	$0.01
Common Stock, shares authorized	800	800
Common Stock, shares issued	285.7	283.9
Common Stock, shares outstanding	271.7	270.1

Stockholders_Equity_Parentheti

Stockholders' Equity Parenthetical (Parentheticals) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stockholders' Equity Parenthetical [Abstract]
Net change in unrealized (losses) gains on available-for-sale securities, tax (benefit) provision	($0.50)	$0.50	$4
Net unrealized (losses) gains on cash flow hedges, tax benefit	-54.6	-300	-3.9
Postretirement plans and workers' compensation obligations, tax (benefit) provision	($10.30)	$121.70	$43.90

Summary_of_Significant_Account

Summary of Significant Accounting Policies Discussion	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Summary of Significant Accounting Policies Discussion	Summary of Significant Accounting Policies
	Basis of Presentation
	The consolidated financial statements include the accounts of Peabody Energy Corporation (the Company) and its affiliates. Interests in subsidiaries controlled by the Company are consolidated with any outside shareholder interests reflected as noncontrolling interests, except when the Company has an undivided interest in an unincorporated joint venture. In those cases, the Company includes its proportionate share in the assets, liabilities, revenues and expenses of the jointly controlled entities within each applicable line item of the consolidated financial statements. All intercompany transactions, profits and balances have been eliminated in consolidation. Certain amounts from prior years have been reclassified to conform with the 2014 presentation.
	Description of Business
	The Company is engaged in the mining of thermal coal for sale primarily to electric utilities and metallurgical coal for sale to industrial customers. The Company’s mining operations are located in the United States (U.S.) and Australia, including an equity-affiliate mining operation in Australia. The Company also markets and brokers coal from other coal producers, both as principal and agent, and trades coal and freight-related contracts through trading and business offices in Australia, China, Germany, India, Indonesia, the United Kingdom and the U.S. (listed alphabetically). The Company’s other energy-related commercial activities include participating in operations of a mine-mouth coal-fueled generating plant, managing its coal reserve and real estate holdings, evaluating Btu Conversion projects and supporting the development of clean coal technologies.
	Newly Adopted Accounting Standards
	Presentation of Unrecognized Tax Benefits. In July 2013, the Financial Accounting Standards Board (FASB) issued accounting guidance requiring entities to present unrecognized tax benefits as a reduction to any related deferred tax assets for net operating losses, similar tax losses or tax credit carryforwards if such settlement is required or expected in the event an uncertain tax position is disallowed. Previously effective U.S. GAAP did not provide explicit guidance on the topic. The new presentation guidance became effective for interim and annual periods beginning after December 15, 2013 (January 1, 2014 for the Company). The adoption of the guidance beginning January 1, 2014 had no material effect on the Company's results of operations, financial condition, cash flows or financial statement presentation.
	Accounting Standards Not Yet Implemented
	Going Concern. In August 2014, the FASB issued disclosure guidance that requires management to evaluate, at each annual and interim reporting period, whether substantial doubt exists about an entity's ability to continue as a going concern and, if applicable, to provide related disclosures. As outlined by that guidance, substantial doubt about an entity's ability to continue as a going concern exists when relevant conditions and events, considered in the aggregate, indicate that it is probable that an entity will be unable to meet its obligations as they become due within one year after the date that the financial statements are issued (or are available to be issued). The new guidance will be effective for annual reporting periods ending after December 15, 2016 (the year ending December 31, 2016 for the Company) and interim periods thereafter, with early adoption permitted.
	Revenue Recognition. In May 2014, the FASB issued a comprehensive revenue recognition standard that will supersede nearly all existing revenue recognition guidance under U.S. GAAP. The new standard provides a single principles-based, five-step model to be applied to all contracts with customers, which steps are to (1) identify the contract(s) with the customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract and (5) recognize revenue when each performance obligation is satisfied. More specifically, revenue will be recognized when promised goods or services are transferred to the customer in an amount that reflects the consideration expected in exchange for those goods or services. The standard also requires entities to disclose sufficient qualitative and quantitative information to enable financial statement users to understand the nature, amount, timing and uncertainty of revenues and cash flows arising from contracts with customers. The new guidance will be effective for interim and annual periods beginning after December 15, 2016 (January 1, 2017 for the Company) and the standard allows for either a full retrospective adoption or a modified retrospective adoption. The Company is in the process of evaluating the impact that the adoption of this guidance will have on its results of operations, financial condition, cash flows and financial statement presentation.
	Discontinued Operations. In April 2014, the FASB issued accounting guidance that raised the threshold for disposals to qualify as discontinued operations to a disposal of a component or group of components that is disposed of or is classified as held for sale and represents a strategic shift that has (or will have) a major effect on an entity's operations and financial results. Such a strategic shift may include the disposal of (1) a major geographical area of operations, (2) a major line of business, (3) a major equity method investment or (4) other major parts of an entity. Provided that the major strategic shift criterion is met, the new guidance does allow entities to have significant continuing involvement and continuing cash flows with the discontinued operation, unlike current U.S. GAAP. The new standard also requires additional disclosures for discontinued operations and new disclosures for individually material disposal transactions that do not meet the definition of a discontinued operation. The new guidance will apply prospectively to disposals that occur in interim and annual periods beginning on or after December 31, 2014 (January 1, 2015 for the Company). The impact to the Company's financial statements will depend on any disposal activity that occurs subsequent to adoption in 2015.
	Sales
	The Company’s revenue from coal sales is realized and earned when risk of loss passes to the customer. Under the typical terms of the Company’s coal supply agreements, title and risk of loss transfer to the customer at the mine or port, where coal is loaded to the transportation source(s) that serves each of the Company’s mines. The Company incurs certain “add-on” taxes and fees on coal sales. Reported coal sales include taxes and fees charged by various federal and state governmental bodies and the freight charged on destination customer contracts.
	Other Revenues
	"Other revenues" include net revenues from coal trading activities as discussed in Note 7. "Coal Trading," as well as coal sales revenues that were derived from the Company’s mining operations and sold through the Company’s coal trading business. Also included are revenues from contract termination or restructuring payments, royalties related to coal lease agreements, sales agency commissions, farm income, property and facility rentals and generation development activities. Royalty income generally results from the lease or sublease of mineral rights to third parties, with payments based upon a percentage of the selling price or an amount per ton of coal produced.
	Discontinued Operations and Assets Held for Sale
	The Company classifies items within discontinued operations in the consolidated financial statements when the operations and cash flows of a particular component of the Company have been (or will be) eliminated from the ongoing operations of the Company as a result of a disposal (by sale or otherwise) and the Company will no longer have any significant continuing involvement in the operation of that component. Refer to Note 3. "Discontinued Operations" for additional details related to discontinued operations.
	Cash and Cash Equivalents
	Cash and cash equivalents are stated at cost, which approximates fair value. Cash equivalents consist of highly liquid investments with original maturities of three months or less.
	Inventories
	Coal is reported as inventory at the point in time the coal is extracted from the mine. Raw coal represents coal stockpiles that may be sold in current condition or may be further processed prior to shipment to a customer. Saleable coal represents coal stockpiles which require no further processing prior to shipment to a customer.
	Coal inventory is valued at the lower of average cost or market. Coal inventory costs include labor, supplies, equipment (including depreciation thereto) and operating overhead and other related costs incurred at or on behalf of the mining location. Market represents the estimated net realizable value of the inventory, which considers the projected future sales price of the particular coal product, less applicable selling costs, and, in the case of raw coal, estimated remaining processing costs. The valuation of coal inventory is subject to several additional estimates, including those related to ground and aerial surveys used to measure quantities and processing recovery rates.
	Materials and supplies inventory is valued at the lower of average cost or market, less a reserve for obsolete or surplus items. This reserve incorporates several factors, such as anticipated usage, inventory turnover and inventory levels.
	Investments in Marketable Securities
	The Company’s short-term investments in marketable securities, which are included in "Other current assets" in the consolidated balance sheets, are defined as those investments with original maturities upon purchase of greater than three months and up to one year. Long-term investments, which are included in "Investments and other assets" in the consolidated balance sheets, are defined as those investments with original maturities upon purchase of greater than one year.
	The Company classifies its investments in debt securities as either held-to-maturity or available-for-sale at the time of purchase and reevaluates such designation periodically. Such investments are classified as held-to-maturity when the Company has the intent and ability to hold the securities to maturity. Investments in debt securities not classified as held-to-maturity and investments in marketable equity securities are classified as available-for-sale. Available-for-sale securities are carried at fair value, with unrealized gains and losses, net of income taxes, generally reported in “Accumulated other comprehensive loss” in the consolidated balance sheets. Realized gains and losses, determined on a specific identification method, are included in “Interest income” in the consolidated statements of operations.
	At each reporting date, the Company performs separate evaluations of its marketable securities to determine if any unrealized losses present are other-than-temporary. Such evaluations involve the consideration of several factors, including, but not limited to, the length of time the market value has been less than cost, the financial condition and near-term prospects of the issuer of the securities and whether the Company has the positive intent and ability to hold the securities until recovery. Refer to Note 2. "Asset Impairment and Mine Closure Costs" and Note 5. "Investments" for details regarding other-than-temporary impairment losses of $4.7 million, $21.5 million and $35.5 million recognized during the years ended December 31, 2014, 2013 and 2012, respectively, related to the Company's marketable equity securities holdings.
	Property, Plant, Equipment and Mine Development
	Property, plant, equipment and mine development are recorded at cost. Interest costs applicable to major asset additions are capitalized during the construction period. Capitalized interest in 2014, 2013 and 2012 was immaterial. Expenditures which extend the useful lives of existing plant and equipment assets are capitalized. Maintenance and repairs are charged to operating costs as incurred. Costs incurred to develop coal mines or to expand the capacity of operating mines are capitalized. Costs incurred to maintain current production capacity at a mine are charged to operating costs as incurred. Costs to acquire computer hardware and the development and/or purchase of software for internal use are capitalized and depreciated over the estimated useful lives.
	Coal reserves are recorded at cost, or at fair value in the case of nonmonetary exchanges, of reserves or business acquisitions.
	Depletion of coal reserves and amortization of advance royalties is computed using the units-of-production method utilizing only proven and probable reserves (as adjusted for recoverability factors) in the depletion base. Mine development costs are principally amortized over the estimated lives of the mines using the straight-line method. Depreciation of plant and equipment is computed using the straight-line method over the shorter of the asset's estimated useful life or the life of the mine. The estimated useful lives by category of assets are as follows:


		Years

	Building and improvements	1 to 37
	Machinery and equipment	1 to 37
	Leasehold improvements	Shorter of Useful Life or Remaining Life of Lease
	Equity and Cost Method Investments
	The Company accounts for its investments in less than majority owned corporate joint ventures under either the equity or cost method. The Company applies the equity method to investments in joint ventures when it has the ability to exercise significant influence over the operating and financial policies of the joint venture. Investments accounted for under the equity method are initially recorded at cost and any difference between the cost of the Company’s investment and the underlying equity in the net assets of the joint venture at the investment date is amortized over the lives of the related assets that gave rise to the difference. The Company’s pro-rata share of the operating results of joint ventures and basis difference amortization is reported in the consolidated statements of operations in “Loss from equity affiliates.” Similarly, the Company's pro-rata share of the cumulative foreign currency translation adjustment of its equity method investments whose functional currency is not the U.S. dollar is reported in the consolidated balance sheet as a component of "Accumulated other comprehensive loss," with periodic changes thereto reflected in the consolidated statements of comprehensive income.
	The Company monitors its equity and cost method investments for indicators that a decrease in investment value has occurred that is other than temporary. Examples of such indicators include a sustained history of operating losses and adverse changes in earnings and cash flow outlook. In the absence of quoted market prices for an investment, discounted cash flow projections are used to assess fair value, the underlying assumptions to which are generally considered unobservable Level 3 inputs under the fair value hierarchy. If the fair value of an investment is determined to be below its carrying value and that loss in fair value is deemed other than temporary, an impairment loss is recognized. No such impairment losses were recorded during the year ended December 31, 2014. Refer to Note 2. "Asset Impairment and Mine Closure Costs" and Note 5. "Investments" for details regarding other-than-temporary impairment losses of $43.2 million and $39.4 million recorded during the years ended December 31, 2013 and 2012, respectively, related to certain of the Company's equity and cost method investments.
	Asset Retirement Obligations
	The Company’s asset retirement obligation (ARO) liabilities primarily consist of spending estimates for surface land reclamation and support facilities at both surface and underground mines in accordance with applicable reclamation laws in the U.S. and Australia as defined by each mining permit.
	The Company estimates its ARO liabilities for final reclamation and mine closure based upon detailed engineering calculations of the amount and timing of the future cash spending for a third party to perform the required work. Spending estimates are escalated for inflation and then discounted at the credit-adjusted, risk-free rate. The Company records an ARO asset associated with the discounted liability for final reclamation and mine closure. The obligation and corresponding asset are recognized in the period in which the liability is incurred. The ARO asset is amortized on the units-of-production method over its expected life and the ARO liability is accreted to the projected spending date. As changes in estimates occur (such as mine plan revisions, changes in estimated costs or changes in timing of the performance of reclamation activities), the revisions to the obligation and asset are recognized at the appropriate credit-adjusted, risk-free rate. The Company also recognizes an obligation for contemporaneous reclamation liabilities incurred as a result of surface mining. Contemporaneous reclamation consists primarily of grading, topsoil replacement and re-vegetation of backfilled pit areas.
	Contingent Liabilities
	From time to time, the Company is subject to legal and environmental matters related to our continuing and discontinued operations and certain historical, non-coal producing operations. In connection with such matters, the Company is required to assess the likelihood of any adverse judgments or outcomes, as well as potential ranges of probable losses.
	A determination of the amount of reserves required for these matters is made after considerable analysis of each individual issue. The Company accrues for legal and environmental matters within "Operating costs and expenses" when it is probable that a liability has been incurred and the amount of the loss can be reasonably estimated. The Company provides disclosure surrounding loss contingencies when it believes that it is at least reasonably possible that a material loss may be incurred or an exposure to loss in excess of amounts already accrued may exist. Adjustments to contingent liabilities are made when additional information becomes available that affects the amount of estimated loss, which information may include changes in facts and circumstances, changes in interpretations of law in the relevant courts, the results of new or updated environmental remediation cost studies and the ongoing consideration of trends in environmental remediation costs.
	Accrued contingent liabilities exclude claims against third parties and are not discounted. The current portion of these accruals is included in “Accounts payables and accrued expenses” and the long-term portion is included in “Other noncurrent liabilities” in the consolidated balance sheets. In general, legal fees related to environmental remediation and litigation are charged to expense. The Company includes the interest component of any litigation-related penalties within "Interest expense" in the consolidated statements of operations.
	Income Taxes
	Income taxes are accounted for using a balance sheet approach. The Company accounts for deferred income taxes by applying statutory tax rates in effect at the reporting date of the balance sheet to differences between the book and tax basis of assets and liabilities. A valuation allowance is established if it is “more likely than not” that the related tax benefits will not be realized. Significant weight is given to evidence that can be objectively verified including history of tax attribute expiration and cumulative income or loss. In determining the appropriate valuation allowance, the Company considers the projected realization of tax benefits based on expected levels of future taxable income, available tax planning strategies, reversals of existing taxable temporary differences and taxable income in carryback years.
	The Company recognizes the tax benefit from uncertain tax positions only if it is “more likely than not” the tax position will be sustained on examination by the taxing authorities based on the technical merits of the position. The tax benefits recognized from such a position are measured based on the largest benefit that has a greater than fifty percent likelihood of being realized upon ultimate settlement. To the extent the Company’s assessment of such tax positions changes, the change in estimate will be recorded in the period in which the determination is made. Tax-related interest and penalties are classified as a component of income tax expense.
	Postretirement Health Care and Life Insurance Benefits
	The Company accounts for postretirement benefits other than pensions by accruing the costs of benefits to be provided over the employees’ period of active service. These costs are determined on an actuarial basis. The Company’s consolidated balance sheets reflect the accumulated postretirement benefit obligations of its postretirement benefit plans. The Company accounts for changes in its postretirement benefit obligations as a settlement when an irrevocable action has been effected that relieves the Company of its actuarially-determined liability to individual plan participants and removes substantial risk surrounding the nature, amount and timing of the obligation’s funding and the assets used to effect the settlement. See Note 15. "Postretirement Health Care and Life Insurance Benefits" for information related to postretirement benefits.
	Pension Plans
	The Company sponsors non-contributory defined benefit pension plans accounted for by accruing the cost to provide the benefits over the employees’ period of active service. These costs are determined on an actuarial basis. The Company’s consolidated balance sheets reflect the funded status of the defined benefit pension plans. See Note 16. "Pension and Savings Plans" for information related to pension plans.
	Restructuring Activities
	From time to time, the Company initiates restructuring activities in connection with its repositioning efforts to appropriately align its cost structure or optimize its coal production relative to prevailing global coal industry conditions. Costs associated with restructuring actions can include early mine closures, voluntary and involuntary workforce reductions, office closures and other related activities. Costs associated with restructuring activities are recognized in the period incurred.
	Included as a component of "Restructuring and pension settlement charges" in the the Company's consolidated statements of operations for the years ended December 31, 2014 and 2013 were aggregate restructuring charges of $15.7 million and $11.9 million, respectively, primarily associated with voluntary and involuntary workforce reductions. The majority of the cash expenditures associated with the charges recognized in 2014 are expected to be paid in the first quarter of 2015.
	In 2013, the Company ceased production and commenced with the early closure of the Wilkie Creek Mine in the Surat Basin in Queensland, Australia. In 2012, we initiated two early mine closures in the U.S.: the Air Quality Mine in Indiana and Willow Lake Mine in Illinois. See Note 2. "Asset Impairment and Mine Closure Costs" and Note 3. "Discontinued Operations" for information related to those early mine closures. No mines were closed in advance of the anticipated exhaustion of reserves in 2014.
	Derivatives
	The Company recognizes at fair value all contracts meeting the definition of a derivative as assets or liabilities in the consolidated balance sheets, with the exception of certain coal trading contracts for which the Company has elected to apply a normal purchases and normal sales exception.
	With respect to derivatives used in hedging activities, the Company assesses, both at inception and at least quarterly thereafter, whether such derivatives are highly effective at offsetting the changes in the anticipated exposure of the hedged item. The effective portion of the change in the fair value of derivatives designated as a cash flow hedge is recorded in “Accumulated other comprehensive loss” until the hedged transaction impacts reported earnings, at which time any gain or loss is reclassified to earnings. To the extent that periodic changes in the fair value of derivatives deemed highly effective exceeds such changes in the hedged item, the ineffective portion of the periodic non-cash changes are recorded in earnings in the period of the change. If the hedge ceases to qualify for hedge accounting, the Company prospectively recognizes changes in the fair value of the instrument in earnings in the period of the change. The potential for hedge ineffectiveness is present in the design of certain of the Company’s cash flow hedge relationships and is discussed in detail in Note 6. "Derivatives and Fair Value Measurements" and Note 7. "Coal Trading." Gains or losses from derivative financial instruments designated as fair value hedges are recognized immediately in earnings, along with the offsetting gain or loss related to the underlying hedged item.
	The Company’s asset and liability derivative positions are offset on a counterparty-by-counterparty basis if the contractual agreement provides for the net settlement of contracts with the counterparty in the event of default or termination of any one contract.
	Non-derivative contracts and derivative contracts for which the Company has elected to apply the normal purchases and normal sales exception are accounted for on an accrual basis.
Business Combinations
The Company accounts for business combinations using the purchase method of accounting. The purchase method requires the Company to determine the fair value of all acquired assets, including identifiable intangible assets and all assumed liabilities. The total cost of acquisitions is allocated to the underlying identifiable net assets, based on their respective estimated fair values. Determining the fair value of assets acquired and liabilities assumed requires management's judgment and the utilization of independent valuation experts, and often involves the use of significant estimates and assumptions, including assumptions with respect to future cash inflows and outflows, discount rates and asset lives, among other items.
Impairment of Long-Lived Assets
The Company evaluates its long-lived assets held and used in operations for impairment as events and changes in circumstances indicate that the carrying amount of such assets might not be recoverable. Factors that would indicate potential impairment to be present include, but are not limited to, a sustained history of operating or cash flow losses, an unfavorable change in earnings and cash flow outlook, prolonged adverse industry or economic trends and a significant adverse change in the extent or manner in which a long-lived asset is being used or in its physical condition. The Company generally does not view short-term declines in thermal and metallurgical coal prices in the markets in which it sells those products as a triggering event for conducting impairment tests because such markets have a history of price volatility. However, the Company generally does view a sustained trend of depressed coal market pricing (for example, over periods exceeding one year) as an indicator of potential impairment.
Assets are grouped at the lowest level for which there are identifiable cash flows that are largely independent of the cash flows of other groups of assets. For its active mining operations, the Company generally groups such assets at the mine level, or the mining complex level for mines that share infrastructure, with the exception of impairment evaluations triggered by mine closures. In those cases involving mine closures, the related assets are evaluated at the individual asset level for remaining economic life based on transferability to ongoing operating sites and for use in reclamation-related activities, or for expected salvage. For its development and exploration properties and portfolio of surface land and coal reserve holdings, the Company considers several factors to determine whether to evaluate those assets individually or on a grouped basis for purposes of impairment testing. Such factors include geographic proximity to one another, the expectation of shared infrastructure upon development based on future mining plans and whether it would be most advantageous to bundle such assets in the event of sale to a third party.
When indicators of impairment are present, the Company evaluates its long-lived assets for recoverability by comparing the estimated undiscounted cash flows expected to be generated by those assets under various assumptions to their carrying amounts. If such undiscounted cash flows indicate that the carrying value of the asset group is not recoverable, impairment losses are measured by comparing the estimated fair value of the asset group to its carrying amount. As quoted market prices are unavailable for the Company's individual mining operations, fair value is determined through the use of an expected present value technique based on the income approach, except for non-strategic coal reserves, surface lands and undeveloped coal properties excluded from the Company's long-range mine planning. In those cases, a market approach is utilized based on the most comparable market multiples available. The estimated future cash flows and underlying assumptions used to assess recoverability and, if necessary, measure the fair value of the Company's long-lived mining assets are derived from those developed in connection with the Company's planning and budgeting process. The Company believes its assumptions to be consistent with those a market participant would use for valuation purposes. The most critical assumptions underlying the Company's projections and fair value estimates include those surrounding future tons sold, coal prices for unpriced coal, production costs (including costs for labor, commodity supplies and contractors), transportation costs, foreign currency exchange rates and a risk-adjusted, after-tax cost of capital (all of which generally constitute unobservable Level 3 inputs under the fair value hierarchy), in addition to market multiples for non-strategic coal reserves, surface lands and undeveloped coal properties excluded from the Company's long-range mine planning (which generally constitute Level 2 inputs under the fair value hierarchy).
Refer to Note 2. "Asset Impairment and Mine Closure Costs" for details regarding impairment charges related to long-lived assets of $149.7 million, $463.6 million and $833.6 million recognized during the years ended December 31, 2014, 2013 and 2012, respectively.
Fair Value
For assets and liabilities that are recognized or disclosed at fair value in the consolidated financial statements, the Company defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date.
Foreign Currency
Functional currency is determined by the primary economic environment in which an entity operates, which for the Company's foreign operations is generally the U.S. dollar because sales prices in international coal markets and the Company's sources of financing those operations is denominated in that currency. Accordingly, substantially all of the Company’s consolidated foreign subsidiaries utilize the U.S. dollar as their functional currency. Monetary assets and liabilities are remeasured at year-end exchange rates while non-monetary items are remeasured at historical rates. Income and expense accounts are remeasured at the average rates in effect during the year, except for those expenses related to balance sheet amounts that are remeasured at historical exchange rates. Gains and losses from foreign currency remeasurement related to tax balances are included as a component of "Income tax (benefit) provision," while all other remeasurement gains and losses are included in "Operating costs and expenses." The total impact of foreign currency remeasurement on the consolidated statements of operations was a net loss of $1.3 million for the year ended December 31, 2014 and a net gain of $34.1 million and $4.8 million for the years ended December 31, 2013 and 2012, respectively.
The Company owns a 50% equity interest Middlemount Coal Pty Ltd. (Middlemount), which owns the Middlemount Mine in Queensland, Australia. Middlemount utilizes the Australian dollar as its functional currency. Accordingly, the assets and liabilities of that equity investee are translated to U.S. dollars at the year-end exchange rate and income and expense accounts are translated at the average rate in effect during the year. The Company's pro-rata share of the translation gains and losses of the equity investee are recorded as a component of "Accumulated other comprehensive loss." Australian dollar denominated shareholder loans to the Middlemount Mine, which are long term in nature, are considered part of the Company's net investment in that operation. Accordingly, foreign currency gains or losses on those loans are recorded as a component of foreign currency translation adjustment. The Company recorded foreign currency translation losses of $41.0 million and $92.7 million for the years ended December 31, 2014 and 2013, respectively, and a translation gain of $19.1 million for the year ended December 31, 2012.
Share-Based Compensation
The Company accounts for share-based compensation at the grant date fair value of awards and recognizes the related expense over the service period of the awards. See Note 18. "Share-Based Compensation" for information related to share-based compensation.
Exploration and Drilling Costs
Exploration expenditures are charged to operating costs as incurred, including costs related to drilling and study costs incurred to convert or upgrade mineral resources to reserves.
Advance Stripping Costs
Pre-production. At existing surface operations, additional pits may be added to increase production capacity in order to meet customer requirements. These expansions may require significant capital to purchase additional equipment, expand the workforce, build or improve existing haul roads and create the initial pre-production box cut to remove overburden (that is, advance stripping costs) for new pits at existing operations. If these pits operate in a separate and distinct area of the mine, the costs associated with initially uncovering coal (that is, advance stripping costs incurred for the initial box cuts) for production are capitalized and amortized over the life of the developed pit consistent with coal industry practices.
Post-production. Advance stripping costs related to post-production are expensed as incurred. Where new pits are routinely developed as part of a contiguous mining sequence, the Company expenses such costs as incurred. The development of a contiguous pit typically reflects the planned progression of an existing pit, thus maintaining production levels from the same mining area utilizing the same employee group and equipment.
Use of Estimates in the Preparation of the Consolidated Financial Statements
The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Asset_Impairment_and_Mine_Clos

Asset Impairment and Mine Closure Costs	12 Months Ended
	Dec. 31, 2014
Asset Impairment and Mine Closure Costs [Abstract]
Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block]	Asset Impairment and Mine Closure Costs
	Year Ended December 31, 2014
	The following costs are reflected in "Asset impairment and mine closure costs" in the consolidated statement of operations for the year ended December 31, 2014:


			Reportable Segment
			Australian			Western			Corporate			Consolidated
			Mining			U.S. Mining			and Other
			(Dollars in millions)
	Asset impairment charges:
	Long-lived assets		$	78.6		$	2.7		$	68.4		$	149.7

	Marketable securities		—			—			4.7			4.7

	Total		$	78.6		$	2.7		$	73.1		$	154.4

	Long-Lived Assets
	Australian Mining. In 2014, the Company observed continued weakness in seaborne metallurgical and thermal coal pricing that has persisted longer than the Company previously anticipated and, accordingly, conducted a review of its Australian Mining segment assets for recoverability. Based on that evaluation, the Company determined that the carrying values of one of its active surface mines that produces metallurgical and thermal coal and two non-strategic undeveloped coal properties were not recoverable and correspondingly recognized an aggregate impairment charge of $78.6 million to write those assets down from their carrying value to their estimated fair value. In addition to the impairment indicators surrounding the Australian Mining segment as a whole, the fair value of the impaired surface mining operation was affected by a short remaining economic life compared to those of other operations and the incremental cost associated with utilizing a contractor to operate the mine.
	Corporate and Other. The Company identified indicators of impairment to be present in 2014 for certain of its non-strategic undeveloped coal properties in Indiana and Colorado due to a lack of observed interest from potential buyers in acquiring those assets, properties that are no longer part of the Company's long-term mining plan and, in the case of certain of the assets, an election by the Company to terminate or allow the lapse of mining-related leases. The Company determined the carrying value of those holdings to not be recoverable and recognized an aggregate impairment charge of $68.4 million to write down the carrying value of the related properties.
	Marketable Securities
	Refer to Note 5. "Investments" for additional details surrounding an other-than-temporary impairment charge of $4.7 million recorded during the fourth quarter of 2014 related to the Company's investment in the marketable equity securities of Winsway Enterprises Holdings Limited (Winsway), formally referred to as Winsway Coking Coal Holdings Limited.
	Risks and Uncertainties
	The Company's mining and exploration assets and mining-related investments may be adversely affected by numerous uncertain factors that may cause the Company to be unable to recover all or a portion of the carrying value of those assets. The Company generally does not view short-term declines in thermal and metallurgical coal prices in the markets in which it sells its products as an indicator of impairment. However, the Company generally does view a sustained trend (for example, over periods exceeding one year) of adverse coal market pricing or unfavorable changes thereto as a potential indicator of impairment. Because of the volatile and cyclical nature of U.S. and international seaborne coal markets, it is reasonably possible that prices in those market segments may decrease and/or fail to improve in the near term, which may result in the need for future adjustments to the carrying value of the Company's long-lived mining assets and mining-related investments.
	The Company's assets whose recoverability and values are most sensitive to near-term pricing include certain non-strategic Australian undeveloped coal properties and mining-related investments. Such assets had an aggregate carrying value of $124.1 million as of December 31, 2014. The Company conducted a review of those assets for recoverability as of December 31, 2014 and determined that, other than the charges related to the Australian Mining segment described above, no further impairment charge was necessary as of that date.
	Year Ended December 31, 2013
	The following costs are reflected in "Asset impairment and mine closure costs" in the consolidated statement of operations for the year ended December 31, 2013:


			Reportable Segment
			Australian			Corporate			Consolidated
			Mining			and Other
			(Dollars in millions)
	Asset impairment charges:
	Long-lived assets		$	390.8		$	72.8		$	463.6

	Equity method investment		—			43.2			43.2

	Marketable securities		—			21.5			21.5

	Total		$	390.8		$	137.5		$	528.3

	Long-Lived Assets
	Australian Mining. In 2013, the Company determined that the long-lived assets of one of its active surface mines that produces metallurgical and thermal coal, one of its surface mining development projects that the Company instead decided to pursue as an underground operation and an exploration tenement were not recoverable, in whole or in part, and correspondingly recognized an aggregate impairment charge of $390.8 million to write each of those assets down from its carrying value to its estimated fair value. In addition to weakness in seaborne metallurgical and thermal coal pricing, the fair value of the impaired surface mining operation was affected by a short remaining economic life compared to those of other operations and site-specific adverse changes in 2013 surrounding realized coal quality yields, contractor performance and contract mining terms, the latter of which were amended during the fourth quarter of that period. With respect to the exploration tenement, the Company determined the fair value of that asset based on an indicative sale offer received in December 2013, which constituted a Level 2 input under the fair value hierarchy. That sale was executed in January 2014, as described further in Note 20. "Resource Management and Other Commercial Events."
	Corporate and Other. In December 2013, contract mining at a coal reserve property in the Eastern U.S. substantially ended upon completion of mining within the existing permit area and new permits were not obtained for the remaining reserves at that property due to new permitting conditions that the Company deemed unacceptable and projected poor near-term economic performance. As a result of that decision and a lack of observed interest from certain financial and strategic buyers in acquiring the remaining coal reserves, the Company recorded an impairment charge of $66.3 million to write down the carrying value of the related reserves. Also, in connection with a review of its portfolio of surface land and coal reserve holdings, the Company determined the carrying value of one of its coal reserve holdings leased to a third-party underground miner to not be fully recoverable and recognized an impairment charge of $6.5 million to write down the carrying value of those reserves to their estimated fair value.
	Mine Closures
	Wilkie Creek Mine. In December 2013, the Company approved a decision to cease production at the Wilkie Creek Mine in the Surat Basin in Queensland, Australia, and commenced with the closure of that mine. The results of that mine are reported as a discontinued operation for all periods presented because the operations and cash flows of the mine have been eliminated from the ongoing operations of the Company as a result of its closure. Refer to Note 3. "Discontinued Operations" for additional details regarding charges recognized during the year ended December 31, 2013 related to this mine closure.
	Equity Method Investment
	Refer to Note 5. "Investments" for additional details surrounding an other-than-temporary impairment charge of $43.2 million recognized in 2013 associated with the Company's 50% equity interest in Middlemount.
	Marketable Securities
	Refer to Note 5. "Investments" for additional details surrounding an other-than-temporary impairment charge of $21.5 million recorded during the second quarter of 2013 related to the Company's investment in Winsway marketable equity securities.
	Year Ended December 31, 2012
	The following costs are reflected in "Asset impairment and mine closure costs" in the consolidated statement of operations for the year ended December 31, 2012:


			Reportable Segment
			Australian			Western			Midwestern			Corporate			Consolidated
			Mining			U.S. Mining			U.S. Mining			and Other
			(Dollars in millions)
	Charges related to mine closures:
	Impairment of long-lived assets		$	—		$	—		$	26.9		$	—		$	26.9

	Acceleration of asset retirement obligations		—			—			7.1			—			7.1

	Employee termination benefits		—			—			6.7			—			6.7

Other		—			—			4.3			—			4.3

Other asset impairment charges:

Long-lived assets		806.7			—			—			—			806.7

Marketable securities		—			—			—			35.5			35.5

Cost method investments		—			—			—			39.4			39.4

Other		—			2.4			—			—			2.4

Total		$	806.7		$	2.4		$	45		$	74.9		$	929

Long-Lived Assets
Australian Mining. In 2012, the Company determined that the long-lived assets of three of its surface mines that produce metallurgical coal (in whole or in part) were not fully recoverable and recognized an impairment charge of $806.7 million to write each of those mines down from its carrying value to its estimated fair value. The fair values of those assets were each adversely affected in that period by a general weakening in international coal market conditions, a sustained trend of depressed coal prices and a persistent strengthening of the Australian dollar compared to the U.S. dollar.
Mine Closures
Willow Lake Mine. In November 2012, the Company announced the permanent closure of its Willow Lake Mine in Illinois due to a continued failure by the site to meet standards for safety, compliance and operating performance deemed acceptable by the Company. Because the performance obligations under the customer coal supply agreements previously serviced by the site were migrated to other mines within the Western and Midwestern U.S. Mining segments, the Willow Lake Mine continued to be classified in continuing operations for all periods presented. The results of that mine, prior to closing, were included in the Midwestern U.S. Mining segment. The Company recognized total charges of $45.0 million in the fourth quarter of 2012 in connection with the shutdown of this mine, which were primarily related to the impairment of long-lived assets, an acceleration in the timing of asset retirement obligations and employee termination benefits.
Air Quality Mine. In September 2012, the Company announced it had permanently ceased production at its Air Quality Mine in Indiana due to uneconomic market conditions for the type of coal product previously produced at that site. The results of that mine, which were previously included within the Midwestern U.S. Mining reportable segment, have been reported as a discontinued operation for all periods presented because the operations and cash flows of the mine and the related coal product was eliminated from the ongoing operations of the Company as a result of the mine closure. Refer to Note 3. "Discontinued Operations" for additional details regarding charges recognized during the year ended December 31, 2012 associated with this mine closure.
Marketable Securities
Refer to Note 5. "Investments" for additional details surrounding an other-than-temporary impairment charge of $35.5 million recorded during the fourth quarter of 2012 related to the Company's investment in Winsway marketable equity securities.
Cost Method Investments
During the year ended December 31, 2012, the Company evaluated the commercial viability of the partnership projects underlying certain of its investments accounted for under the cost method due to adverse changes in the operating and regulatory environment surrounding those projects. As a result of that review, the Company concluded there to be significant doubt as to the ability of those projects to continue development and recorded an aggregate charge of $39.4 million to fully impair the carrying value of those investments.

Discontinued_Operations

Discontinued Operations	12 Months Ended
	Dec. 31, 2014
Discontinued Operations and Disposal Groups [Abstract]
Disposal Groups, Including Discontinued Operations, Disclosure [Text Block]	Discontinued Operations
	Discontinued operations include former Australian Mining and Midwestern U.S. Mining segment assets that have ceased production and other previously divested legacy operations.
	Summarized Results of Discontinued Operations
	Results from discontinued operations were as follows during the years ended December 31, 2014, 2013 and 2012:


		Year Ended December 31,
		2014			2013			2012
		(Dollars in millions)
	Loss from discontinued operations before income taxes	$	(23.8	)	$	(329.7	)	$	(163.9	)
	Income tax (provision) benefit	(4.4		)	103.1			59.7

	Loss from discontinued operations, net of income taxes	$	(28.2	)	$	(226.6	)	$	(104.2	)
	There were no significant revenues from discontinued operations during the year ended December 31, 2014. Total revenues associated with discontinued operations amounted to $136.5 million and $229.1 million during the years ended December 31, 2013 and 2012, respectively.
	Settlement Agreement with Patriot and the UMWA. Loss from discontinued operations for the year ended December 31, 2014 included a charge of $34.1 million related to changes in the fair value of credit support provided to Patriot Coal Corporation (Patriot) following its 2013 bankruptcy reorganization. Loss from discontinued operations for the year ended December 31, 2013 included before- and after-tax charges charges associated with the settlement of claims and litigation related to the bankruptcy reorganization of Patriot of $98.0 million and $61.8 million, respectively. Refer to Note 25. "Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation" for additional information surrounding those matters.
	Wilkie Creek Mine. In December 31, 2013, the Company ceased production and commenced the reclamation of the Wilkie Creek Mine in Queensland, Australia and correspondingly accrued for contractual liabilities and certain other exit costs at that time. The following table summarizes the changes in those liabilities for the year ended December 31, 2014:


		Contractual Liabilities			Other Exit Costs			Total
		(Dollars in millions)
	Liability balance at December 31, 2013	$	33.9		$	2.7		$	36.6

	Change in estimate	(5.0		)	(0.2		)	(5.2		)
	Cash payments	(28.4		)	(2.5		)	(30.9		)
	Foreign currency loss	0.3			—			0.3

	Liability balance at December 31, 2014	$	0.8		$	—		$	0.8

	In addition to the closure-related liabilities detailed above, the Company's consolidated balance sheet at December 31, 2014 included $47.5 million of asset retirement obligations related to Wilkie Creek.
	In May 2014, the Company entered into an agreement to sell the Wilkie Creek Mine in exchange for approximately $70 million in cash and the assumption of port and rail obligations and asset retirement obligations, with the closing of the sale subject to certain conditions. In August 2014, the Company terminated that agreement as the potential buyer was unable to meet its obligations for closing. In connection with the termination, the Company recognized a net gain of $4.6 million, comprised of a non-refundable payment made by the potential buyer towards the purchase, partially offset by transaction costs. The net gain on termination was classified in "Loss from discontinued operations, net of income taxes" in the consolidated statement of operations for the year ended December 31, 2014.
	Reflected in the results from discontinued operations for the year ended December 31, 2013 are total before- and after-tax charges of $167.4 million and $117.2 million, respectively, including before- and after-tax impairment charges of $107.0 million and $74.9 million, respectively, recognized in connection with the Company's previous efforts to sell the Wilkie Creek Mine in Queensland, Australia and the ultimate shutdown of that site.
	Air Quality Mine. Reflected in the results from discontinued operations for the year ended December 31, 2012 are total before- and after-tax charges of $116.7 million and $75.0 million, respectively, including before- and after-tax impairment charges of $108.9 million and $68.8 million, respectively, recognized in connection with the shutdown of the Air Quality Mine in Indiana.
	Refer to Note 2. "Asset Impairment and Mine Closure Costs" for additional details surrounding these mine closures.
	Assets and Liabilities of Discontinued Operations
	Assets and liabilities classified as discontinued operations included in the Company's consolidated balance sheets were as follows:


		December 31,
		2014			2013
		(Dollars in millions)
	Assets:
	Other current assets	$	0.3		$	38.6

	Investments and other assets	16.3			47.4

	Total assets classified as discontinued operations	$	16.6		$	86


	Liabilities:
	Accounts payable and accrued expenses	$	12.5		$	133.1

	Other noncurrent liabilities	109.8			84.9

	Total liabilities classified as discontinued operations	$	122.3		$	218

Inventories

Inventories	12 Months Ended
	Dec. 31, 2014
Inventory Disclosure [Abstract]
Inventories	Inventories
	Inventories as of December 31, 2014 and December 31, 2013 consisted of the following:


		December 31,
		2014		2013
		(Dollars in millions)
	Materials and supplies	$	143.6	$	166.8

	Raw coal	115		122.6

	Saleable coal	147.9		217.3

	Total	$	406.5	$	506.7

	Materials and supplies inventories presented above have been shown net of reserves of $4.6 million and $7.4 million as of December 31, 2014 and 2013, respectively.

Investments_Investments_Notes

Investments Investments (Notes)	12 Months Ended
	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block]	Investments
	Investments in Marketable Securities
	Investments in available-for-sale securities at December 31, 2014 were as follows:


	Available-for-sale securities		Amortized Cost				Gross				Gross				Fair Value
							Unrealized				Unrealized
							Gains				Losses
			(Dollars in millions)
	Current:
	U.S. corporate bonds		$	11.2			$	—			$	—			$	11.2

	Noncurrent:
	Marketable equity securities		6.2				—				—				6.2

	Federal government securities		32				—				—				32

	U.S. corporate bonds		12.4				—				—				12.4

	Total		$	61.8			$	—			$	—			$	61.8

	Investments in available-for-sale securities at December 31, 2013 were as follows:


	Available-for-sale securities		Amortized Cost				Gross				Gross				Fair Value
							Unrealized				Unrealized
							Gains				Losses
							(Dollars in millions)
	Current:
	Federal government securities		$	2.8			$	—			$	—			$	2.8

	U.S. corporate bonds		2.4				—				—				2.4

	Noncurrent:
	Marketable equity securities		10.9				1.3				—				12.2

	Federal government securities		28.8				—				(0.1		)		28.7

	U.S. corporate bonds		20.8				0.1				—				20.9

	Total		$	65.7			$	1.4			$	(0.1	)		$	67

	The Company’s investments in marketable equity securities consist of an investment in Winsway.
	Contractual maturities for available-for-sale investments in debt securities at December 31, 2014 were as shown below. Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.


	Contractual maturities for available-for-sale securities		Cost				Fair Value
			(Dollars in millions)
	Due in one year or less		$	11.2			$	11.2

	Due in one to five years		44.4				44.4

	Total		$	55.6			$	55.6

	Proceeds from sales and maturities of available-for-sale debt securities amounted to $13.5 million, $22.9 million and $17.2 million for the years ended December 31, 2014, 2013 and 2012, respectively. The Company realized zero net gains associated with those sales and maturities as of December 31, 2014 and $0.2 million and $0.1 million for the years ended December 31, 2013 and 2012, respectively.
	In addition to the securities described above, the Company previously held investments in debt and equity securities related to the Company's pro-rata share of funding in the Newcastle Coal Infrastructure Group (NCIG), which was included in "Investments and other assets" in the consolidated balance sheets. The debt securities were recorded at cost, which approximated fair value, and were denominated in U.S. dollars. The Company received proceeds from the sale of NCIG securities of $29.2 million for the year ended December 31, 2012 and recognized a corresponding loss on those sales of $0.2 million during that period. There were no NCIG securities held during the years ended December 31, 2014 and 2013.
	At each reporting date, the Company performs separate evaluations of debt and equity securities to determine if any unrealized losses are other-than-temporary. Given the duration and severity of the market losses incurred and in certain historical periods in connection with Winsway's credit downgrades, the Company recognized other-than-temporary impairment losses of $4.7 million, $21.5 million and $35.5 million during the fourth quarter of 2014, second quarter of 2013 and fourth quarter of 2012, respectively, each time resetting the cost basis of the Company's investment.
	In November 2012, the Company purchased $4.8 million of time deposits denominated in Chinese Renminbi with six month maturities. Proceeds from the maturity of those investments amounted to $4.8 million in the year ended December 31, 2013. The Company had no held-to-maturity securities at December 31, 2014 and 2013.
	Equity Method Investments
	The Company’s equity method investments include its joint venture interest in the Middlemount, which was acquired in connection with the 2011 acquisition of PEA-PCI (formerly Macarthur Coal Limited), in addition to certain other equity method investments. The table below summarizes the book value of those investments, which is reported in “Investments and other assets” in the consolidated balance sheets, and the related loss from equity affiliates:


		Book Value at December 31,								Loss from Equity
										Affiliates for the Year Ended
December 31,
										2014				2013				2014	2013	2012
	(Dollars in millions)
Equity interest in Middlemount Coal Pty Ltd	$	58			$	173.4			$	98.5			$	33.5			$	52.1

Other equity method investments	7.3				6.7				9.1				6.7				9.1

Total equity method investments	$	65.3			$	180.1			$	107.6			$	40.2			$	61.2

During the years ended December 31, 2014, 2013 and 2012, Middlemount generated revenues of approximately $165 million, $157 million and $118 million (on a 50% basis). During the year ended December 31, 2014, the Company recorded to "Loss from equity affiliates" its pro-rata share of a valuation allowance of $52.3 million on Middlemount's Australian net deferred tax assets. Based on a Middlemount's history of operating losses driven by sustained weakness in seaborne metallurgical coal prices, and considering available sources of taxable income, it was determined in 2014 that the net deferred tax assets are no longer considered more likely than not of being realized.
In 2013, due to a sustained weakness in seaborne metallurgical coal prices, a history of operating losses at the mine and the magnitude of the difference between the estimated fair value and the carrying value of its equity investment, the Company determined the carrying value of its equity investment in Middlemount to be other-than-temporarily impaired. Correspondingly, the Company recorded an impairment charge of $43.2 million during the year ended December 31, 2013 to write down the carrying value of its equity investment, which was reflected in "Asset impairment and mine closure costs" in the consolidated statement of operations for that period.
The remaining unamortized basis difference as of December 31, 2014 between the amount at which the Company's equity investment in Middlemount is carried and the amount of underlying equity in net assets of Middlemount is $96.1 million. Including the impact of basis difference, Middlemount had current assets, noncurrent assets, current liabilities and noncurrent liabilities of $27.8 million, $424.4 million, $382.9 million and $11.3 million, respectively, as of December 31, 2014 and $30.9 million, $525.3 million, $365.6 million and $17.2 million, respectively, as of December 31, 2013 (on a 50% basis).
In addition to its equity method investment, the Company periodically makes loans to Middlemount pursuant to the related shareholders' agreement. Refer to Note 8. "Financing Receivables" for additional details surrounding those loans.

Derivatives_and_Fair_Value_Mea

Derivatives and Fair Value Measurements (Notes)	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Derivatives and Fair Value Measurements	Derivatives and Fair Value Measurements
	Risk Management — Non Coal Trading Activities
	The Company is exposed to various types of risk in the normal course of business, including foreign currency exchange rate risk for non-U.S. dollar expenditures and balances, price risk on commodities utilized in the Company's mining operations and interest rate risk on long-term debt. The Company manages commodity price risk (excluding coal trading activities) related to the sale of coal, in part, through the use of long-term coal supply agreements (those with terms longer than one year) to the extent possible, rather than through the use of derivative instruments. In order to manage its exposure related to price risk on certain commodities used in production, as well as for foreign currency exchange rate and interest rate risk, the Company utilizes derivative financial instruments. These risks are actively monitored in an effort to ensure compliance with the risk management policies of the Company.
	Foreign Currency Hedges. The Company is exposed to foreign currency exchange rate risk, primarily on Australian dollar expenditures made in its Australian Mining segment. This risk is managed through the use of forward contracts and options that the Company designates as cash flow hedges, with the objective of reducing the variability of cash flows associated with forecasted foreign currency expenditures.
	Diesel Fuel Hedges. The Company is exposed to commodity price risk associated with diesel fuel and explosives utilized in production in the U.S. and Australia. This risk is managed through the use of derivatives, primarily swaps, and to a lesser extent through the use of cost pass-through contracts. The Company generally designates the swap contracts as cash flow hedges, with the objective of reducing the variability of cash flows associated with forecasted diesel fuel purchases.
	Explosives Hedges. The Company is also exposed to commodity price risk associated with explosives utilized in production in the U.S. and Australia. From time to time, this risk is managed through the use of derivatives, primarily swaps. This risk is also managed through the use of cost pass-through contracts. When swap contracts are used, the Company generally designates those contracts as cash flow hedges, with the objective of reducing the variability of cash flows associated with forecasted explosives purchases. As of December 31, 2014, the Company had no swaps in place associated with explosives hedges.
	Interest Rate Swaps. The Company is exposed to interest rate risk on its fixed rate and variable rate long-term debt. From time to time, the Company manages the interest rate risk associated with the fair value of its fixed rate borrowings using fixed-to-floating interest rate swaps to effectively convert a portion of the underlying cash flows on the debt into variable rate cash flows. The Company designates these swaps as fair value hedges, with the objective of hedging against adverse changes in the fair value of the fixed rate debt that result from market interest rate changes. In addition, from time to time, interest rate risk associated with the Company’s variable rate borrowings is managed using floating-to-fixed interest rate swaps. The Company designates these swaps as cash flow hedges, with the objective of reducing the variability of cash flows associated with market interest rate changes. As of December 31, 2014, the Company had no interest rate swaps in place.
	Notional Amounts and Fair Value. The following summarizes the Company’s foreign currency and commodity positions at December 31, 2014:


		Notional Amount by Year of Maturity
		Total				2015				2016				2017
	Foreign Currency

	A$:US$ hedge contracts (A$ millions)	$	3,191.10			$	1,661.10			$	1,007.00			$	523

	Commodity Contracts

	Diesel fuel hedge contracts (million gallons)	201.5				103.4				67.5				30.6



		Instrument Classification by
		Cash				Fair				Economic					Fair Value
		Flow				Value				Hedge					of Net Liability
		Hedge				Hedge
															(Dollars in millions)
	Foreign Currency

	A$:US$ hedge contracts (A$ millions)	$	3,191.10			$	—			$	—				$	(410.0	)

	Commodity Contracts

	Diesel fuel hedge contracts (million gallons)	201.5				—				—					(167.1		)

	Based on the net fair value of the Company’s non-coal trading commodity contract hedge positions held in “Accumulated other comprehensive loss” at December 31, 2014, the Company expects to reclassify net unrealized losses associated with the Company’s diesel fuel hedge programs of approximately $100 million from comprehensive income into earnings over the next 12 months. Based on net unrealized losses associated with the Company's foreign currency hedge contract portfolio, partially offset by unrecognized realized gains related to foreign currency cash flow hedge contracts monetized in the fourth quarter of 2012 held in "Accumulated other comprehensive loss" at December 31, 2014, the net loss expected to be reclassified from comprehensive income to earnings over the next 12 months associated with that hedge program is approximately $226 million. As these realized and unrealized gains and losses are associated with derivative instruments that represent hedges of forecasted transactions, the amounts reclassified to earnings are expected to partially offset the effect of any changes in the hedged exposure related to the underlying transaction, when realized.
	Hedge Ineffectiveness. A measure of ineffectiveness is inherent in hedging future diesel fuel purchases with derivative positions based on refined petroleum products as a result of location and/or product differences. Transportation surcharges, which may vary over time, for purchased diesel fuel in certain regions can also result in ineffectiveness, though such surcharges have historically changed infrequently and comprise a small portion of the total cost of delivered diesel.
	The Company’s derivative positions for the hedging of forecasted foreign currency expenditures contain a small measure of ineffectiveness due to timing differences between the hedge settlement and the purchase transaction, which could differ by less than a day and up to a maximum of 30 days.
	The tables below show the classification and amounts of pre-tax gains and losses related to the Company’s non-coal trading hedges during the years ended December 31, 2014, 2013 and 2012:


					Year Ended December 31, 2014
			Income Statement Classification		Loss				Loss				Loss
			Losses - Realized		recognized in				reclassified				reclassified
					other				from other				from other
					comprehensive				comprehensive				comprehensive
					income on				income into				income into
					derivative				income (effective				income
					(effective portion)				portion) (1)				(ineffective
	Financial Instrument												portion)
					(Dollars in millions)
	Commodity swap contracts		Operating costs and expenses		$	(194.5	)		$	(20.6	)		$	(1.7	)
	Foreign currency forward contracts		Operating costs and expenses		(100.9		)		(27.3		)		—

	Total				$	(295.4	)		$	(47.9	)		$	(1.7	)

	(1)	Includes the reclassification from "Accumulated other comprehensive loss" into earnings of $136.9 million of previously unrecognized gains on foreign currency cash flow hedge contracts monetized in the fourth quarter of 2012.


					Year Ended December 31, 2013
			Income Statement Classification		Gain (loss)				Gain				Loss
			Gains (Losses) - Realized		recognized in				reclassified				reclassified
					other				from other				from other
					comprehensive				comprehensive				comprehensive
			income on			income into			income into
			derivative			income			income
			(effective portion)			(effective			(ineffective
Financial Instrument										portion)				portion)
					(Dollars in millions)
Commodity swap contracts		Operating costs and expenses			$	12.5				$	11.9			$	(0.5	)

Foreign currency forward contracts		Operating costs and expenses		(597.8		)		162.4				—

Total				$	(585.3	)		$	174.3			$	(0.5	)



				Year Ended December 31, 2012
		Income Statement Classification		Gain				Gain				Loss
		Gains (Losses) - Realized		recognized in				reclassified				reclassified
				other				from other				from other
				comprehensive				comprehensive				comprehensive
				income on				income into				income into
				derivative				income				income
				(effective portion)				(effective				(ineffective
Financial Instrument								portion)				portion)
				(Dollars in millions)
Commodity swap contracts		Operating costs and expenses		$	14.5			$	48.3			$	(4.7	)

Foreign currency forward contracts		Operating costs and expenses		148				351.7				—

Total				$	162.5			$	400			$	(4.7	)


Cash Flow Presentation. The Company classifies the cash effects of its non-coal trading derivatives within the "Cash Flows From Operating Activities" section of the consolidated statements of cash flows during the period of settlement for those instruments. In November 2012, with the Australian dollar trading at elevated levels against the U.S. dollar, the Company terminated certain of its Australian dollar forward contracts in exchange for aggregate realized cash proceeds of $151.8 million. Prior to discontinuation, those contracts comprised an aggregate notional amount of $1.9 billion originally contracted for settlement during 2014 and 2015 and were designated as cash flow hedges of Australian dollar expenditures forecasted to occur at those times. Upon termination, the Company executed at-market Australian dollar forward contracts with notional amounts and forward settlement dates identical to the terminated contracts and designated those replacement contracts as cash flow hedges of the anticipated future Australian dollar expenditures previously hedged by the terminated contracts. Because those forecasted expenditures remained probable of occurring upon termination, the Company continued to reflect the effective portion of the realized gains on the terminated forward contracts in "Accumulated other comprehensive loss." During the year ended December 31, 2014, the Company reclassified $136.9 million of those gains from "Accumulated other comprehensive loss" into earnings, with the remaining gains expected to be reclassified in 2015.
Offsetting and Balance Sheet Presentation
The Company's non-coal trading derivative financial instruments are transacted in over-the-counter (OTC) markets with financial institutions under International Swaps and Derivatives Association (ISDA) Master Agreements. Those agreements contain symmetrical default provisions which allow for the net settlement of amounts owed by either counterparty in the event of default or contract termination. The Company offsets its non-coal trading asset and liability derivative positions on a counterparty-by-counterparty basis in the condensed consolidated balance sheets, with the fair values of those respective derivatives reflected in “Other current assets,” “Investments and other assets,” “Accounts payable and accrued expenses” and “Other noncurrent liabilities." Though the symmetrical default provisions associated with the Company's non-coal trading derivatives exist at the overall counterparty level across its foreign currency and diesel fuel hedging strategy derivative contract portfolios, it is the Company's accounting policy to apply counterparty offsetting separately within those derivative contract portfolios for presentation in the condensed consolidated balance sheets because that application is more consistent with the fact that the Company generally net settles its non-coal trading derivatives with each counterparty by derivative contract portfolio on a routine basis.
The classification and amount of non-coal trading derivative financial instruments presented on a gross and net basis as of December 31, 2014 and 2013 are presented in the tables that follow.



		Fair Value of Liabilities Presented in the Consolidated Balance Sheet as of December 31, 2014 (1)
Financial Instrument

Current Liabilities:
Commodity swap contracts		$	100.1

Foreign currency forward contracts		241

Total		$	341.1


Noncurrent Liabilities:
Commodity swap contracts		$	67

Foreign currency forward contracts		169

Total		$	236


(1)	All commodity swap contracts and foreign currency forward contracts were in a liability position as of December 31, 2014.



		Fair Value of Assets as of December 31, 2013
		Gross Amounts Recognized				Gross Amounts Offset in the Consolidated Balance Sheet				Net Amounts Presented in the Consolidated Balance Sheet				Derivatives Not Offset in the Consolidated Balance Sheet (1)				Net Amount
Financial Instrument
		(Dollars in millions)
Current Assets:
Commodity swap contracts		$	8.7			$	(2.3	)		$	6.4			n.a.				n.a.

Foreign currency forward contracts		—				—				—				n.a.				n.a.

Total		$	8.7			$	(2.3	)		$	6.4			$	(5.0	)		$	1.4


Noncurrent Assets:
Commodity swap contracts		$	2.8			$	(0.9	)		$	1.9			n.a.				n.a.

Foreign currency forward contracts		0.2				(0.2		)		—				n.a.				n.a.

Total		$	3			$	(1.1	)		$	1.9			$	(1.3	)		$	0.6


-1	Adjustments relate to the further netting of derivative contracts with a common counterparty across the Company's foreign currency, diesel fuel and explosives hedging strategy derivative contract portfolios that would be contractually enforceable in the event of default.


		Fair Value of Liabilities as of December 31, 2013
		Gross Amounts Recognized				Gross Amounts Offset in the Consolidated Balance Sheet				Net Amounts Presented in the Consolidated Balance Sheet				Derivatives Not Offset in the Consolidated Balance Sheet (1)				Net Amount
Financial Instrument
		(Dollars in millions)
Current Liabilities:
Commodity swap contracts		$	3.9			$	(1.9	)		$	2			n.a.				n.a.

Foreign currency forward contracts		211.9				—				211.9				n.a.				n.a.

Total		$	215.8			$	(1.9	)		$	213.9			$	(5.4	)		$	208.5


Noncurrent Liabilities:
Commodity swap contracts		$	2.5			$	(1.3	)		$	1.2			n.a.				n.a.

Foreign currency forward contracts		261.6				(0.2		)		261.4				n.a.				n.a.

Total		$	264.1			$	(1.5	)		$	262.6			$	(0.9	)		$	261.7


-1	Adjustments relate to the further netting of derivative contracts with a common counterparty across the Company's foreign currency, diesel fuel and explosives hedging strategy derivative contract portfolios that would be contractually enforceable in the event of default.
See Note 7. "Coal Trading" for information on balance sheet offsetting related to the Company’s coal trading activities.
Fair Value Measurements
The Company uses a three-level fair value hierarchy that categorizes assets and liabilities measured at fair value based on the observability of the inputs utilized in the valuation. These levels include: Level 1 - inputs are quoted prices in active markets for the identical assets or liabilities; Level 2 - inputs are other than quoted prices included in Level 1 that are directly or indirectly observable through market-corroborated inputs; and Level 3 - inputs are unobservable, or observable but cannot be market-corroborated, requiring the Company to make assumptions about pricing by market participants.
Financial Instruments Measured on a Recurring Basis. The following tables set forth the hierarchy of the Company’s net financial asset (liability) positions for which fair value is measured on a recurring basis:


	December 31, 2014
	Level 1				Level 2				Level 3				Total
					(Dollars in millions)
Investments in debt and equity securities	$	26.1			$	35.7			$	—			$	61.8

Commodity swap contracts	—				(167.1		)		—				(167.1		)

Foreign currency forward contracts	—				(410.0		)		—				(410.0		)

Total net financial assets (liabilities)	$	26.1			$	(541.4	)		$	—			$	(515.3	)



	December 31, 2013
	Level 1				Level 2				Level 3				Total
					(Dollars in millions)
Investments in debt and equity securities	$	28.8			$	38.2			$	—			$	67

Commodity swap contracts	—				5.1				—				5.1

Foreign currency forward contracts	—				(473.3		)		—				(473.3		)

Total net financial assets (liabilities)	$	28.8			$	(430.0	)		$	—			$	(401.2	)

For Level 1 and 2 financial assets and liabilities, the Company utilizes both direct and indirect observable price quotes, including interest rate yield curves, exchange indices, broker/dealer quotes, published indices, issuer spreads, benchmark securities and other market quotes. In the case of certain debt securities, fair value is provided by a third-party pricing service. Below is a summary of the Company’s valuation techniques for Level 1 and 2 financial assets and liabilities:

•	Investments in debt and equity securities: U.S. government securities and marketable equity securities are valued based on quoted prices in active markets (Level 1) and investment-grade corporate bonds and U.S. government agency securities are valued based on the various inputs listed above that may preclude the security from being measured using an identical asset in an active market (Level 2).

•	Commodity swap contracts — diesel fuel and explosives: valued based on a valuation that is corroborated by the use of market-based pricing (Level 2).

•	Foreign currency forward and option contracts: valued utilizing inputs obtained in quoted public markets (Level 2).
The Company did not have any transfers between levels during the years ended December 31, 2014, 2013 or 2012 for its non-coal trading positions. The Company’s policy is to value all transfers between levels using the beginning of period valuation.
Other Financial Instruments. The following methods and assumptions were used by the Company in estimating fair values for other financial instruments as of December 31, 2014 and 2013:

•	Cash and cash equivalents, accounts receivable, including those within the Company’s accounts receivable securitization program, notes receivable and accounts payable have carrying values which approximate fair value due to the short maturity or the liquid nature of these instruments.

•	Long-term debt fair value estimates are based on observed prices for securities with an active trading market when available (Level 2), and otherwise on estimated borrowing rates to discount the cash flows to their present value (Level 3).
The carrying amounts and estimated fair values of the Company’s long-term debt are summarized as follows:


	December 31, 2014								December 31, 2013
	Carrying				Estimated				Carrying				Estimated
	Amount				Fair Value				Amount				Fair Value
					(Dollars in millions)
Long-term debt	$	5,986.80			$	5,227.90			$	6,002.40			$	6,167.50

Credit and Nonperformance Risk
The fair value of the Company’s non-coal trading derivative assets and liabilities reflects adjustments for credit risk. The Company manages its counterparty risk through established credit standards, diversification of counterparties, utilization of investment grade commercial banks, adherence to established tenor limits based on counterparty creditworthiness and continual monitoring of that creditworthiness. To reduce its credit exposure for these hedging activities, the Company seeks to enter into netting agreements with counterparties that permit the Company to offset asset and liability positions with such counterparties in the event of default. The Company also continually monitors counterparties for nonperformance risk, if present, on a case-by-case basis.

Coal_Trading

Coal Trading	12 Months Ended
	Dec. 31, 2014
Coal Trading [Abstract]
Coal Trading	Coal Trading
	The Company engages in the direct and brokered trading of coal and freight-related contracts (coal trading). Except those for which the Company has elected to apply a normal purchases and normal sales exception, all derivative coal trading contracts are accounted for at fair value.
	The Company's policy is to include instruments associated with coal trading transactions as a part of its trading book. Trading revenues from such transactions are recorded in “Other revenues” in the consolidated statements of operations and include realized and unrealized gains and losses on derivative instruments, including those that arise from coal deliveries related to contracts accounted for on an accrual basis under the normal purchases and normal sales exception. Therefore, the Company has elected the trading exemption surrounding disclosures related to its coal trading activities.
	Trading revenues recognized during the years ended December 31, 2014, 2013 and 2012 were as follows:


			Year Ended December 31,
	Trading Revenue by Type of Instrument		2014				2013				2012
			(Dollars in millions)
	Commodity futures, swaps and options		$	92.3			$	183.9			$	159.9

	Physical commodity purchase/sale contracts		(33.9		)		(117.9		)		(8.1		)
	Total trading revenue		$	58.4			$	66			$	151.8

	Risk Management
	Hedge Ineffectiveness. In some instances, the Company has designated an existing coal trading derivative as a hedge and, thus, the derivative has a non-zero fair value at hedge inception. The “off-market” nature of these derivatives, which is best described as an embedded financing element within the derivative, is a source of ineffectiveness. In other instances, the Company uses a coal trading derivative that settles at a different time, has different quality specifications or has a different location basis than the occurrence of the cash flow being hedged. These collectively yield ineffectiveness to the extent that the derivative hedge contract does not exactly offset changes in the fair value or expected cash flows of the hedged item.
	The gross fair value of coal trading positions designated as cash flow hedges of forecasted sales was an asset of $44.3 million and $62.9 million as of December 31, 2014 and 2013, respectively. Based on the net fair value of the Company’s coal trading positions held in “Accumulated other comprehensive loss” at December 31, 2014, unrealized gains to be reclassified from comprehensive income to earnings over the next 12 months are expected to be approximately $45 million. As these unrealized gains are associated with derivative instruments that represent hedges of forecasted transactions, the amounts reclassified to earnings may partially offset the effect of the realized underlying transactions in the consolidated statements of operations.
	Forecasted Transactions No Longer Probable. During the year ended December 31, 2014, the Company reclassified gains of $2.0 million out of “Accumulated other comprehensive loss” to earnings as the underlying forecasted transactions were deemed no longer probable of occurring within an acceptable proximity to the timing contemplated at hedge designation.
	Offsetting and Balance Sheet Presentation
	The Company's coal trading assets and liabilities include financial instruments, such as swaps, futures and options, cleared through various commodities exchanges, which involve the daily net settlement of closed positions. The Company is required to post cash collateral, known as variation margin, on exchange-cleared positions that are in a net liability position and entitled to receive variation margin when in a net asset position. The Company also transacts in coal trading financial swaps and options through OTC markets with financial institutions and other non-financial trading entities under ISDA Master Agreements, which contain symmetrical default provisions. Certain of the Company's coal trading agreements with OTC counterparties also contain credit support provisions that may periodically require the Company to post, or entitle the Company to receive, variation margin. Physical coal and freight-related purchase and sale contracts included in the Company's coal trading assets and liabilities are executed pursuant to master purchase and sale agreements that also contain symmetrical default provisions and allow for the netting and setoff of receivables and payables that arise during the same time period. The Company offsets its coal trading asset and liability derivative positions, and variation margin related to those positions, on a counterparty-by-counterparty basis in the consolidated balance sheets, with the fair values of those respective derivatives reflected in “Assets from coal trading activities, net” and “Liabilities from coal trading activities, net."
	The fair value of assets and liabilities from coal trading activities presented on a gross and net basis as of December 31, 2014 and 2013 is set forth below:


	Affected line item in the consolidated balance sheets		Gross Amounts of Recognized Assets (Liabilities)				Gross Amounts Offset in the Consolidated Balance Sheets				Variation margin (held) posted (1)				Net Amounts of Assets (Liabilities) Presented in the Consolidated Balance Sheets
			(Dollars in millions)
			Fair Value as of December 31, 2014
	Assets from coal trading activities, net		$	342.5			$	(248.3	)		$	(36.6	)		$	57.6

	Liabilities from coal trading activities, net		(285.0		)		248.3				4				(32.7		)

	Total, Net		$	57.5			$	—			$	(32.6	)		$	24.9


			Fair Value as of December 31, 2013
	Assets from coal trading activities, net		$	418.8			$	(324.7	)		$	(58.0	)		$	36.1

	Liabilities from coal trading activities, net		(332.7		)		324.7				1.9				(6.1		)

	Total, Net		$	86.1			$	—			$	(56.1	)		$	30


	(1)	None and $42 million of the net variation margin held at December 31, 2014 and 2013, respectively, related to cash flow hedges.
	See Note 6. "Derivatives and Fair Value Measurements" for information on balance sheet offsetting related to the Company’s non-coal trading activities.
	Fair Value Measurements
	The following tables set forth the hierarchy of the Company’s net financial asset (liability) coal trading positions for which fair value is measured on a recurring basis as of December 31, 2014 and 2013:


		December 31, 2014
		Level 1				Level 2				Level 3				Total
		(Dollars in millions)
	Commodity futures, swaps and options	$	(0.2	)		$	32.6			$	—			$	32.4

	Physical commodity purchase/sale contracts	—				(9.6		)		2.1				(7.5		)

	Total net financial (liabilities) assets	$	(0.2	)		$	23			$	2.1			$	24.9



		December 31, 2013
		Level 1				Level 2				Level 3				Total
						(Dollars in millions)
	Commodity futures, swaps and options	$	—			$	26.4			$	—			$	26.4

	Physical commodity purchase/sale contracts	—				1.5				2.1				3.6

Total net financial assets	$	—			$	27.9			$	2.1			$	30

For Level 1 and 2 financial assets and liabilities, the Company utilizes both direct and indirect observable price quotes, including U.S. interest rate curves; LIBOR yield curves; Chicago Mercantile Exchange (CME) Group, Intercontinental Exchange (ICE), LCH.Clearnet (formerly known as the London Clearing House), NOS Clearing ASA and Singapore Exchange (SGX) contract prices; broker quotes; published indices and other market quotes. Below is a summary of the Company’s valuation techniques for Level 1 and 2 financial assets and liabilities:

•	Commodity futures, swaps and options: generally valued based on unadjusted quoted prices in active markets (Level 1) or a valuation that is corroborated by the use of market-based pricing (Level 2).

•	Physical commodity purchase/sale contracts: purchases and sales at locations with significant market activity corroborated by market-based information (Level 2).
Physical commodity purchase/sale contracts transacted in less liquid markets or contracts, such as long-term arrangements with limited price availability, are classified in Level 3. Indicators of less liquid markets are those with periods of low trade activity or wide pricing spreads between broker quotes.
The Company's risk management function, which is independent of the Company's commercial trading function, is responsible for valuation policies and procedures, with oversight from executive management. Generally, the Company's Level 3 instruments or contracts are valued using bid/ask price quotations and other market assessments obtained from multiple, independent third-party brokers or other transactional data incorporated into internally-generated discounted cash flow models. While the Company does not anticipate any decrease in the number of third-party brokers or market liquidity, the occurrence of such events could erode the quality of market information and therefore the valuation of its market positions. The Company's valuation techniques include basis adjustments to the foregoing price inputs for quality, such as heat rate and sulfur and ash content; location differentials, expressed as port and freight costs, and credit risk. The Company's risk management function independently validates the Company's valuation inputs, including unobservable inputs, with third-party information and settlement prices from other sources where available. A daily process is performed to analyze market price changes and changes to the portfolio. Further periodic validation occurs at the time contracts are settled with the counterparty. These valuation techniques have been consistently applied in all periods presented, and the Company believes it has obtained the most accurate information available for the types of derivative contracts held.
The following table summarizes the quantitative unobservable inputs utilized in the Company's internally-developed valuation models for physical commodity purchase/sale contracts classified as Level 3 as of December 31, 2014:


		Range						Weighted
Input		Low			High			Average
Quality adjustments		8	%		12	%		9	%
Location differentials		19	%		19	%		19	%
Significant increases or decreases in the inputs in isolation could result in a significantly higher or lower fair value measurement. The unobservable inputs do not have a direct interrelationship; therefore, a change in one unobservable input would not necessarily correspond with a change in another unobservable input.
The following table summarizes the changes in the Company’s recurring Level 3 net financial assets:


	Year Ended December 31,
	2014				2013				2012
	(Dollars in millions)
Beginning of year	$	2.1			$	5.2			$	8.7

Total gains realized/unrealized:

Included in earnings	6.7				0.3				17.5

Settlements	(6.7		)		(3.4		)		(21.0		)
End of year	$	2.1			$	2.1			$	5.2

The following table summarizes the changes in net unrealized gains (losses) relating to Level 3 net financial assets held both as of the beginning and the end of the period:


	Year Ended December 31,
	2014				2013				2012
	(Dollars in millions)
Changes in unrealized gains (losses) (1)	$	2.1			$	(0.4	)		$	4.1


(1)	Within the consolidated statements of operations and consolidated statements of comprehensive income for the periods presented, unrealized gains and losses from Level 3 items are combined with unrealized gains and losses on positions classified in Level 1 or 2, as well as other positions that have been realized during the applicable periods.
The Company did not have any significant transfers between Level 1 and Level 2 during 2014, 2013 or 2012, nor were there any transfers in or out of Level 3 during those periods. The Company’s policy is to value all transfers between levels using the beginning of period valuation.
As of December 31, 2014, the timing of the estimated future realization of the value of the Company’s trading portfolio was as follows:


		Percentage of
Year of Expiration		Portfolio Total

2015		77	%
2016		19	%
2017		3	%
2018		1	%
		100	%
Credit Risk and Nonperformance. The fair value of the Company’s coal derivative assets and liabilities reflects adjustments for credit risk. The Company’s exposure is substantially with electric utilities, energy marketers, steel producers and nonfinancial trading houses. The Company’s policy is to independently evaluate each customer’s creditworthiness prior to entering into transactions and to regularly monitor the credit extended. If the Company engages in a transaction with a counterparty that does not meet its credit standards, the Company seeks to protect its position by requiring the counterparty to provide an appropriate credit enhancement. Also, when appropriate (as determined by its credit management function), the Company has taken steps to reduce its exposure to customers or counterparties whose credit has deteriorated and who may pose a higher risk of failure to perform under their contractual obligations. These steps include obtaining letters of credit or cash collateral (margin), requiring prepayments for shipments or the creation of customer trust accounts held for the Company’s benefit to serve as collateral in the event of a failure to pay or perform. To reduce its credit exposure related to trading and brokerage activities, the Company seeks to enter into netting agreements with counterparties that permit the Company to offset asset and liability positions with such counterparties and, to the extent required, the Company will post or receive margin amounts associated with exchange-cleared and certain OTC positions. The Company also continually monitors counterparty and contract nonperformance risk, if present, on a case-by-case basis.
As of December 31, 2014, 75% of the Company’s credit exposure related to coal trading activities with investment grade counterparties, while 10% was with non-investment grade counterparties and 15% was with counterparties that are not rated.
Performance Assurances and Collateral
Certain of the Company’s derivative trading instruments require the parties to provide additional performance assurances whenever a material adverse event jeopardizes one party’s ability to perform under the instrument. If the Company was to sustain a material adverse event (using commercially reasonable standards), its counterparties could request collateralization on derivative trading instruments in net liability positions which, based on an aggregate fair value at December 31, 2014 and 2013, would have amounted to collateral postings to counterparties of approximately $31 million and $7 million, respectively. As of December 31, 2014 and 2013, no collateral was posted to counterparties for such positions.
Certain of the Company’s other derivative trading instruments require the parties to provide additional performance assurances whenever a credit downgrade occurs below a certain level, as specified in each underlying contract. The terms of such derivative trading instruments typically require additional collateralization, which is commensurate with the severity of the credit downgrade. During 2014, each of the three major credit rating agencies downgraded the Company's corporate credit rating by one notch. The Company was not required to post additional collateral as a result of those downgrades. Even if a credit downgrade were to have occurred below contractually specified levels, the Company’s additional collateral requirement owed to its counterparties would have been zero at December 31, 2014 and 2013 based on the aggregate fair value of all derivative trading instruments with such features. Accordingly, the Company had posted no margin related to such features as of December 31, 2014 and 2013.
The Company is required to post variation margin on positions that are in a net liability position and is entitled to receive and hold variation margin on positions that are in a net asset position with an exchange and certain of its OTC derivative contract counterparties. At December 31, 2014 and 2013, the Company held net variation margin of $32.6 million and $56.1 million, respectively.
In addition to the requirements surrounding variation margin, the Company is required by the exchanges upon which it transacts to post certain additional collateral, known as initial margin, which represents an estimate of potential future adverse price movements across the Company’s portfolio under normal market conditions. As of December 31, 2014 and 2013, the Company had posted initial margin of $15.2 million and $19.6 million, respectively, which is reflected in “Other current assets” in the consolidated balance sheets. The Company also posted $6.1 million and $1.0 million of margin in excess of the exchange-required variation and initial margin discussed above as of December 31, 2014 and 2013, respectively.

Financing_Receivables

Financing Receivables	12 Months Ended
	Dec. 31, 2014
Receivables [Abstract]
Financing Receivables	Financing Receivables
	The Company's total financing receivables as of December 31, 2014 and 2013 consisted of the following:


	Balance Sheet Classification	December 31, 2014		December 31, 2013
		(Dollars in millions)
	Accounts receivable, net	$	—	$	0.1

	Investments and other assets	347.2		351.7

	Total financing receivables	$	347.2	$	351.8


	The Company periodically assesses the collectability of accounts and loans receivable by considering factors such as specific evaluation of collectability, historical collection experience, the age of the receivable and other available evidence. Below is a description of the Company's financing receivables outstanding as of December 31, 2014.
	Codrilla Mine Project. In 2011, a wholly-owned subsidiary of PEA-PCI, then Macarthur Coal Limited, completed the sale of a portion of its 85% interest in the Codrilla Mine Project to the other participants of the Coppabella Moorvale Joint Venture, afterward retaining 73.3% ownership. The final outstanding installment payment of 40% of the sale price is due upon the earlier of the mine's first coal shipment or a specified date. The sales agreement was amended in the second quarter of 2013 to delay the specified date from March 31, 2015 to June 30, 2016, resulting in an adjustment to the discounted value of the note receivable in the amount of $1.6 million. This adjustment was recorded as a reduction to "Interest income" in the statements of operations for the year ended December 31, 2013. There are currently no indications of impairment on the remaining installment and the Company expects to receive full payment upon the earlier of the mine's first shipment or June 30, 2016. The remaining balance associated with these receivables was recorded in "Investments and other assets" in the consolidated balance sheets, which balance totaled $27.6 million and $28.5 million at December 31, 2014 and 2013, respectively.
	Middlemount Mine. The Company periodically makes loans to Middlemount, in which the Company owns a 50% equity interest, pursuant to the related shareholders' agreement for purposes of funding capital expenditures and working capital requirements. Middlemount is required to pay down the loans as excess cash is generated pursuant to its shareholders’ agreement. The loans bear interest at a rate equal to the monthly average 30-day Australian Bank Bill Swap Reference Rate plus 3.5% and expire on December 24, 2015. Based on the expected timing of repayment of these loans, which is projected to extend beyond the stated expiration date, the Company considers these loans to be of a long-term nature. As a result, the foreign currency impact related to the shareholder loans is included in foreign currency translation adjustment in the consolidated balance sheets and the consolidated statements of comprehensive income. As a result of the expected timing of interest repayments, interest income on these loans is recognized when cash is received. The Company recognized interest income related to these loans of $4.8 million and $6.4 million during the years ended December 31, 2014 and 2013, respectively. Interest income under a full accrual basis would have resulted in additional interest income of $6.4 million and $5.8 million during the years ended December 31, 2014 and 2013, respectively. The carrying value of these loans of $319.6 million and $323.2 million was reflected in "Investments and other assets" in the consolidated balance sheets as of December 31, 2014 and 2013, respectively.
	Other Financing Receivables. From time to time, the Company may enter into transactions resulting in accounts or notes receivable held by the Company, which have been reflected in "Accounts receivable, net." These notes are generally short term in nature with positive historical collection experience and do not represent a material credit risk to the Company.

Property_Plant_Equipment_and_M

Property, Plant, Equipment and Mine Development (Notes)	12 Months Ended
	Dec. 31, 2014
Property, Plant, Equipment and Mine Development [Abstract]
Property, Plant and Equipment Disclosure [Text Block]	Property, Plant, Equipment and Mine Development
	Property, plant, equipment and mine development, net, as of December 31, 2014 and December 31, 2013 consisted of the following:


		December 31,
		2014			2013
		(Dollars in millions)
	Land and coal interests	$	11,021.10		$	11,024.10

	Buildings and improvements	1,569.10			1,525.40

	Machinery and equipment	2,685.70			2,777.50

	Less: Accumulated depreciation, depletion and amortization	(4,698.6		)	(4,244.5		)
	Total, net	$	10,577.30		$	11,082.50

	The net book value of coal reserves totaled $6.2 billion as of December 31, 2014 and $6.3 billion as of December 31, 2013, which excludes the carrying value of acquired interests in mineral rights at certain Australian exploration properties of $1.3 billion at each date. The coal reserves include mineral rights for leased coal interests and advance royalties that had a net book value of $5.0 billion as of December 31, 2014 and $5.1 billion as of December 31, 2013. The remaining net book value of coal reserves of $1.2 billion at December 31, 2014 and 2013 relates to coal reserves held by fee ownership. Amounts attributable to coal reserves at properties where the Company was not currently engaged in mining operations or leasing to third parties and, therefore, the coal reserves were not currently being depleted, was $2.1 billion as of December 31, 2014 and $2.3 billion as of December 31, 2013.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes
	Loss from continuing operations before income taxes for the years ended December 31, 2014, 2013 and 2012 consisted of the following:


		Year Ended December 31,
		2014				2013				2012
		(Dollars in millions)
	U.S.	$	268.9			$	220.6			$	1,049.10

	Non-U.S.	(816.8		)		(954.9		)		(1,257.7		)
	Total	$	(547.9	)		$	(734.3	)		$	(208.6	)
	Total income tax provision (benefit) for the years ended December 31, 2014, 2013 and 2012 consisted of the following:


		Year Ended December 31,
		2014				2013				2012
		(Dollars in millions)
	Current:

	U.S. federal	$	27.1			$	(47.9	)		$	116.8

	Non-U.S.	(61.1		)		38.4				127.6

	State	3.3				(4.7		)		12.2

	Total current	(30.7		)		(14.2		)		256.6

	Deferred:

	U.S. federal	111				4.8				(32.7		)

	Non-U.S.	122.3				(440.3		)		28.8

	State	(1.4		)		1.4				9.6

	Total deferred	231.9				(434.1		)		5.7

	Total income tax provision (benefit)	$	201.2			$	(448.3	)		$	262.3

	The following is a reconciliation of the expected statutory federal income tax benefit to the Company’s income tax provision (benefit) for the years ended December 31, 2014, 2013 and 2012:


		Year Ended December 31,
		2014				2013				2012
		(Dollars in millions)
	Expected income tax benefit at U.S. federal statutory rate	$	(191.7	)		$	(257.0	)		$	(73.0	)
	Changes in valuation allowance, income tax	569.4				(29.4		)		521.5

	Changes in tax reserves	(81.5		)		8.8				24.5

	Excess depletion	(65.3		)		(72.7		)		(69.4		)
	Foreign earnings repatriation	(71.4		)		—				—

	Foreign earnings provision differential	28.8				62.7				(59.6		)

	General business tax credits	(19.2		)		(18.9		)		(17.4		)
	Minerals resource rent tax, net of federal tax	16.1				(87.4		)		77.2

	Remeasurement of foreign income tax accounts	(2.7		)		(44.3		)		7.9

	State income taxes, net of federal tax benefit	(2.3		)		(0.2		)		(1.1		)
	Capital loss	—				—				(118.1		)

	Other, net	21				(9.9		)		(30.2		)

Total income tax provision (benefit)	$	201.2			$	(448.3	)		$	262.3

Certain reconciliation items included in the above table exclude the remeasurement of foreign income tax accounts as these foreign currency effects are separately presented.
The tax effects of temporary differences that gave rise to significant portions of the deferred tax assets and liabilities as of December 31, 2014 and 2013 consisted of the following:


	December 31,
	2014				2013
	(Dollars in millions)
Deferred tax assets:

Tax credits and loss carryforwards	$	1,723.50			$	1,558.00

Minerals resource rent tax	—				993.2

Accrued postretirement benefit obligations	372.3				309.9

Asset retirement obligations	167				141.6

Employee benefits	70.7				88.5

Payable to voluntary employee beneficiary association for certain Patriot retirees (1)	79.2				84.4

Hedge activities	44.2				—

Environmental contingencies	29.9				23.6

Deferred revenue	29.1				3.2

Financial guarantees	16.9				16.9

Workers’ compensation obligations	6.2				10.4

Other	50.5				31.5

Total gross deferred tax assets	2,589.50				3,261.20

Deferred tax liabilities:

Property, plant, equipment and mine development, principally due to differences in depreciation, depletion and asset impairments	1,223.40				1,322.30

Unamortized discount on Convertible Junior Subordinated Debentures	131				131.8

Hedge activities	—				11.4

Investments and other assets	73.4				82

Other	1.1				46.3

Total gross deferred tax liabilities	1,428.90				1,593.80

Valuation allowance, income tax	(1,169.0		)		(656.4		)
Valuation allowance, minerals resource rent tax	—				(977.7		)

Net deferred tax (liability) asset	$	(8.4	)		$	33.3

Deferred taxes are classified as follows:

Current deferred income taxes	$	80			$	66.4

Noncurrent deferred income taxes	(88.4		)		(33.1		)
Net deferred tax (liability) asset	$	(8.4	)		$	33.3


(1)	Refer to Note 25. "Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation" herein for additional details related to this transaction.
The Company's tax credits and tax effected loss carryforwards included U.S. alternative minimum tax (AMT) credits of $290.3 million, foreign tax credits of $147.9 million, tax general business credits of $89.9 million, U.S. capital losses of $51.1 million, state net operating loss (NOL) carryforwards of $41.0 million and foreign NOL carryforwards of $1,103.3 million as of December 31, 2014. The AMT credits and foreign NOLs have no expiration date. The U.S. capital losses and state NOL's begin to expire in 2017 and 2018, respectively. The foreign tax credits and general business credits begin to expire in 2020 and 2027, respectively.
In assessing the near-term use of NOLs and tax credits and corresponding valuation allowance adjustments, the Company evaluated the expected level of future taxable income, available tax planning strategies, reversals of existing taxable temporary differences and taxable income in carryback years. During the year ended December 31, 2014, the Company recorded valuation allowance against net deferred tax asset positions in the U.S. and Australia of $351.2 million and $289.3 million, respectively. Recognition of those valuation allowances was driven by recent cumulative book losses, as determined by considering all sources of available income (including items classified as discontinued operations or recorded directly to "Accumulated other comprehensive loss"), which limited the Company’s ability to look to future taxable income in assessing the realizability of the related assets. The Company also continued to have a partial reserve for its foreign NOL's and certain deferred tax assets based on future realizable value as of December 31, 2014. Of the $351.2 million increase in U.S. valuation allowance during the year ended December 31, 2014, $280.1 million and $71.1 million were reflected in "Income tax provision (benefit)" and "Accumulated other comprehensive loss," respectively.
Due to the repeal of the Australian Minerals and Resource Rent Tax (MRRT) during the year ended December 31, 2014, the Company wrote-off its MRRT related deferred tax assets totaling $993.2 million, along with the corresponding valuation allowance of $977.7 million.
Unrecognized Tax Benefits
Net unrecognized tax benefits (excluding interest and penalties) were recorded as follows in the consolidated balance sheets as of December 31, 2014 and 2013:


	December 31,
	2014				2013
	(Dollars in millions)
Accounts payable and accrued expenses	$	—			$	20.3

Deferred income taxes	6.2				90.3

Other noncurrent liabilities	34.7				29.9

Net unrecognized tax benefits	$	40.9			$	140.5

Gross unrecognized tax benefits	$	44.5			$	143.9

The amount of the Company's gross unrecognized tax benefits decreased by $99.4 million since January 1, 2014 due to the finalization of Australian Tax Office (ATO) audits on the 2004 through 2012 tax years, offset by additions for current positions. The amount of the net unrecognized tax benefits that, if recognized, would directly affect the effective tax rate was $40.9 million and $140.5 million at December 31, 2014 and 2013, respectively. A reconciliation of the beginning and ending amount of gross unrecognized tax benefits for the years ended December 31, 2014, 2013 and 2012 is as follows:


	Year Ended December 31,
	2014				2013				2012
	(Dollars in millions)
Balance at beginning of period	$	143.9			$	122.8			$	119.6

Additions for current year tax positions	12				6.3				17.4

Additions for prior year tax positions	—				63.8				31.9

Reductions for settlements with tax authorities	(111.4		)		—				(46.1		)

Reductions for expirations of statutes of limitations	—				(49.0		)		—

Balance at end of period	$	44.5			$	143.9			$	122.8

The Company recognizes interest and penalties related to unrecognized tax benefits in its income tax provision. The Company (reversed) expensed gross interest and penalties of ($8.0) million, ($36.0) million and $21.2 million for the years ended December 31, 2014, 2013 and 2012, respectively. The Company had $3.4 million and $11.4 million of accrued gross interest and penalties related to unrecognized tax benefits at December 31, 2014 and 2013, respectively.
The Company believes during the next twelve months it is reasonably possible for a $28.6 million decrease in its net unrecognized tax benefits due to potential audit settlements and the expiration of statutes of limitations.
Tax Returns Subject to Examination
The Company's U.S. federal income tax returns are under examination by the IRS for the 2009 through 2012 income tax years. The Company's state income tax returns for the tax years 1999 and thereafter remain potentially subject to examination by various state taxing authorities due to NOL carryforwards. The ATO completed its audit of the Company's Australian income tax returns for the tax years 2004 through 2009 as well as its review of the tax years 2010 through 2012. Australian income tax returns for tax years 2010 through 2013 continue to be subject to potential examinations by the ATO.
Foreign Earnings
The Company had no undistributed earnings of foreign subsidiaries as of December 31, 2014. Historically, the Company has not provided for deferred taxes on undistributed earnings because such earnings are considered to be indefinitely reinvested outside of the U.S.
Tax Payments and Refunds
The following table summarizes the Company’s income tax (refunds) payments, net for the years ended December 31, 2014, 2013 and 2012:


	Year Ended December 31,
	2014				2013				2012
	(Dollars in millions)
U.S. — federal	$	(7.7	)		$	(0.8	)		$	63

U.S. — state and local	(6.8		)		2.9				11.8

Non-U.S.	(2.2		)		79.8				55.7

Total income tax (refunds) payments, net	$	(16.7	)		$	81.9			$	130.5

Accounts_Payable_and_Accrued_E

Accounts Payable and Accrued Expenses	12 Months Ended
	Dec. 31, 2014
Payables and Accruals [Abstract]
Accounts Payable and Accrued Expenses	Accounts Payable and Accrued Expenses
	Accounts payable and accrued expenses consisted of the following:


		December 31,
		2014		2013
		(Dollars in millions)
	Trade accounts payable	$	461.7	$	483

	Commodity and foreign currency hedge contracts	341.1		213.9

	Other accrued expenses	298.8		267.3

	Accrued payroll and related benefits	268.7		248

	Accrued taxes other than income	175.3		223.5

	Payable to voluntary employee beneficiary association for certain Patriot retirees (1)	75		20

	Accrued royalties	61.5		67.1

	Accrued interest	48.4		47.9

	Asset retirement obligations	30.2		21

	Accrued environmental cleanup-related costs	19.4		18.3

	Workers’ compensation obligations	10.9		10

	Income taxes payable	3.3		3.8

	Accrued health care insurance	2.4		7.1

	Liabilities associated with discontinued operations	12.5		133.1

	Total accounts payable and accrued expenses	$	1,809.20	$	1,764.00


	-1	Refer to Note 25. "Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation" herein for additional details related to this transaction.

Debt

Debt	12 Months Ended
Debt	Dec. 31, 2014
Debt Disclosure [Abstract]
Debt Disclosure [Text Block]	Long-term Debt
	The Company’s total indebtedness as of December 31, 2014 and 2013 consisted of the following:


		December 31,
		2014			2013
		(Dollars in millions)
	2013 Term Loan Facility due September 2020	$	1,175.10		$	1,185.40
	2013 Term Loan Facility due September 2020	$	1,175.10		$	1,185.40
	7.375% Senior Notes due November 2016	650			650
	7.375% Senior Notes due November 2016	650			650
	6.00% Senior Notes due November 2018	1,518.80			1,518.80
	6.00% Senior Notes due November 2018	1,518.80			1,518.80
	6.50% Senior Notes due September 2020	650			650
	6.50% Senior Notes due September 2020	650			650
	6.25% Senior Notes due November 2021	1,339.60			1,339.60
	6.25% Senior Notes due November 2021	1,339.60			1,339.60
	7.875% Senior Notes due November 2026	247.6			247.5
	7.875% Senior Notes due November 2026	247.6			247.5
	Convertible Junior Subordinated Debentures due December 2066	382.3			379.7
		382.3			379.7
	Capital lease obligations	22.2			30.5
	Capital lease obligations	22.2			30.5
	Other	1.2			0.9
	Other	1.2			0.9
	Total	$	5,986.80		$	6,002.40
	Total	$	5,986.80		$	6,002.40
	The carrying amounts of the 2013 Term Loan Facility due September 2020, the 7.875% Senior Notes due December 2026 and the Convertible Junior Subordinated Debentures due December 2066 (the Debentures) have been presented above net of the respective unamortized original issue discounts.
	2013 Credit Facility
	On September 24, 2013, the Company entered into a secured credit agreement (as amended, the 2013 Credit Facility), which provides for a $1.65 billion revolving credit facility (the 2013 Revolver) and a $1.20 billion term loan facility (the 2013 Term Loan Facility). In connection with the closing of the 2013 Credit Facility, the Company borrowed $1.19 billion under the 2013 Term Loan Facility, net of original issue discount of $12.0 million that will be amortized over its seven-year term, and transferred $94.7 million of existing letters of credit from its unsecured credit agreement dated as of June 18, 2010 (as amended, the 2010 Credit Agreement). The 2013 Revolver commitment will mature on September 24, 2018, or on August 15, 2018 if the Company’s 6.00% Senior Notes due 2018 are still in existence on such date. The 2013 Term Loan Facility matures on September 24, 2020. The Company capitalized total deferred financing costs of $18.3 million and $10.1 million related to the 2013 Revolver and 2013 Term Loan Facility, respectively, to be amortized over the respective five- and seven-year terms of those facilities.
	Proceeds of the 2013 Term Loan Facility were used primarily to pay off amounts outstanding under the 2010 Credit Agreement and the Company's unsecured credit agreement dated October 28, 2011 (as amended), which had then-outstanding principal amounts of $301.8 million and $862.5 million, respectively. The Company recognized expense of $11.5 million on the write-off of previously deferred financing costs related to those facilities during the year, which was classified in "Interest expense" in the consolidated statement of operations.
	The obligations under the 2013 Credit Facility are guaranteed by the Company and substantially all of its domestic subsidiaries and are secured by (1) a pledge of 65% of the stock of Peabody Investments (Gibraltar) Limited, a holding company for the Australian operations of the Company, (2) a pledge of the stock of Peabody IC Funding Corp., whose assets are substantially comprised of intercompany debt owed to it by Peabody IC Holdings LLC, a holding company whose sole asset is intercompany debt owed to it by the top-level Gibraltar subsidiary of the Company’s Australian platform, an entity which previously owed such debt directly to Peabody IC Funding Corp. and (3) after the effectiveness of the Omnibus Amendment Agreement, dated as of February 5, 2015 (the First Amendment), substantially all of the Company’s U.S. assets and 65% of the equity interests of its first-tier foreign subsidiaries, subject to certain exceptions. The 2013 Credit Facility limits that amount of debt secured by “Principal Property” and “Capital Stock” (as such quoted terms are used in the Company’s Senior Notes indentures) in order for the Company to utilize the general liens basket in the Company’s Senior Notes indentures.
	All borrowings under the 2013 Credit Facility (other than swingline borrowings and borrowings denominated in currencies other than U.S. dollars) bear interest, at the Company’s option, at either a base rate (subject to a floor of 2.00% for borrowings under the 2013 Term Loan Facility) or a eurocurrency rate (subject to a floor of 1.00% for borrowings under the 2013 Term Loan Facility), each as defined in the 2013 Credit Agreement, plus: (1) in the case of the 2013 Term Loan Facility, a margin of 2.25% and 3.25% per year for borrowings bearing interest at the base rate and the eurocurrency rate, respectively; or (2) in the case of the 2013 Revolver, a margin dependent on the Company's consolidated net leverage ratio, as defined in the 2013 Credit Agreement, ranging from 0.75% to 1.50% and 1.75% to 2.50% per year for borrowings bearing interest at the base rate and eurocurrency rate, respectively.
	As of December 31, 2014 the Company had $1,175.1 million outstanding under the 2013 Term Loan Facility with an interest rate payable of LIBOR (with a floor of 1.00%) plus 3.25%, or 4.25% in total.
	The Company pays a usage-dependent commitment fee under the 2013 Revolver, which is dependent upon the Company's consolidated net leverage ratio, as defined in the 2013 Credit Agreement, and ranges from 0.375% to 0.500% of the available unused commitment. In addition, the Company pays a letter of credit fee, which is also dependent upon the Company's leverage ratio and ranges from 1.75% to 2.50% per year of the undrawn amount of each letter of credit, and a fronting fee equal to 0.125% per year of the face amount drawn under each letter of credit.
	The 2013 Term Loan Facility is subject to quarterly amortization of 0.25% per quarter that commenced on October 1, 2013, with the final payment of all amounts outstanding (including accrued interest) being due on September 24, 2020. Subject to customary reinvestment rights, the 2013 Credit Facility is subject to mandatory prepayment and permanent commitment reduction provisions. These provisions include a requirement to prepay the loans with total net proceeds from certain asset sales exceeding $500 million in the aggregate, including certain asset sales by domestic unrestricted subsidiaries or domestic joint ventures of 50% or more of their assets or equity individually or in the aggregate exceeding $200 million. To the extent that mandatory prepayments and or permanent commitment reductions are required, prepayments shall be applied to prepay the term loan borrowings and, once no term loan borrowings are outstanding, the revolving commitments shall be permanently reduced by an amount that depends on the amount of revolving commitments in existence at the time of such reduction.
	Under the 2013 Revolver, the Company must comply with two financial covenants on a quarterly basis, which are a maximum net first lien secured leverage ratio and a minimum interest coverage ratio. The Company was in compliance with those covenants as of December 31, 2014. The Company is permitted to pay dividends, buy and sell assets and make redemptions or repurchases of capital stock, subject to restrictions imposed by the 2013 Credit Facility. That agreement also imposes certain restrictions on the Company's ability to incur liens, incur debt, make investments (including acquisitions), engage in fundamental changes such as mergers and dissolutions, dispose of assets, change the nature of its business, enter into transactions with affiliates, enter into agreements that restrict the Company's ability to make dividends or distributions, enter into agreements with negative pledge clauses, make dividends from the top-level Gibraltar holding company of the Company's Australian operations to the Company's domestic subsidiaries in an amount in excess of $500 million per year and incur liens securing indebtedness on the Company’s “Principal Property” and “Capital Stock” (as such quoted terms are used in the Company’s Senior Notes indentures). It also contains customary events of default. The agreement generally does not restrict the Company’s ability to provide for loans and advances between the parent company and the subsidiaries that secure or guarantee the related indebtedness, provided that certain of such loans and advances are subordinated to the Company’s obligations under the 2013 Credit Agreement.
	The foregoing description of the 2013 Credit Facility addresses the terms of the First Amendment. The First Amendment also:

	•	amended the financial maintenance covenants to provide the Company with greater financial flexibility by lowering the interest coverage ratio and increasing the maximum net first lien secured leverage ratio for the term of the 2013 Credit Facility;

	•	amended a negative covenant in the 2013 Credit Facility to allow for second lien debt issuances, so long as the Company remains in compliance with the 2013 Credit Facility; and

	•	amended certain other negative covenants in the 2013 Credit Facility to (1) reduce the Company’s annual cash dividend payments allowable to a maximum of $27.5 million (with carryforward permitted) and the additional general restricted payments basket, which includes dividends, stock repurchases and certain investments, to a maximum of $100.0 million (which amount may increase based on positive earnings during the term of the agreement) and (2) further limit the Company’s ability to incur liens, incur debt and make investments.
	As of December 31, 2014, the Company had no borrowings under the 2013 Revolver, but had $114.9 million of letters of credit outstanding. The remaining capacity under the 2013 Revolver at December 31, 2014 was $1,535.1 million. The interest rate payable on the 2013 Revolver was LIBOR plus 2.25%, or 2.42% at December 31, 2014.
	6.00%, 6.25%, 6.50%, 7.375% and 7.875% Senior Notes (collectively the Senior Notes)
	The Senior Notes are senior unsecured obligations and rank senior in right of payment to any subordinated indebtedness; equally in right of payment with any senior indebtedness; are effectively junior in right of payment to the Company’s secured indebtedness, to the extent of the value of the collateral securing that indebtedness; and effectively junior to all the indebtedness and other liabilities of its subsidiaries that do not guarantee the notes.
	The Senior Notes are jointly and severally guaranteed by nearly all of the Company’s domestic subsidiaries, as defined in the note indentures. The note indentures contain covenants that, among other things, limit the Company’s ability to create liens and enter into sale and lease-back transactions. The Senior Notes are redeemable at a redemption price equal to 100% of the principal amount of the notes being redeemed plus a make-whole premium and any accrued unpaid interest to the redemption date. If the Company experiences specific kinds of changes in control and the credit rating assigned to the Senior Notes declines below specified levels within 90 days of that time, holders of such notes have the right to require the Company to repurchase their notes at a repurchase price equal to 101% of their principal amount, plus accrued and unpaid interest, if any, to the date of repurchase.
	Interest payments on the Senior Notes are scheduled to occur each year as follows:


	Senior Notes		Interest Payment Dates
	6.00% Senior Notes		May 15 and November 15
	6.25% Senior Notes		May 15 and November 15
	6.50% Senior Notes		March 15 and September 15
	7.375% Senior Notes		May 1 and November 1
	7.875% Senior Notes		May 1 and November 1
	On November 15, 2011, the Company completed a $1.6 billion offering of 6.00% Senior Notes due November 2018 (the 6.00% Senior Notes) and a $1.5 billion offering of 6.25% Senior Notes due November 2021 (the 6.25% Senior Notes), with the proceeds of the offering used, in part, to finance the acquisition of Macarthur. On the same date, the Company, the Guarantors and the initial purchasers of the 6.00% Senior Notes and the 6.25% Senior Notes entered into a registration rights agreement (the Registration Rights Agreement). During the second quarter of 2012, the Company repurchased $81.2 million and $160.4 million in aggregate principal amount of its 6.00% and 6.25% Senior Notes due 2018 and 2021, respectively, with existing cash on hand. The Company recognized a loss on debt extinguishment of $2.8 million associated with these repurchases, which was comprised of $3.4 million of expense related to the write-off of deferred financing costs and a gain of $0.6 million as the repurchases were made below par value. The loss is classified in "Interest expense" in the consolidated statement of operations for the year ended December 31, 2012. In the third quarter of 2012, the Company commenced an offer to exchange any and all of its 6.00% and 6.25% Senior Notes outstanding for substantially identical freely tradable debt securities registered under the Securities Act of 1933. The exchange offer was completed in October 2012 and did not affect the Company's indebtedness outstanding.
	Convertible Junior Subordinated Debentures
	As of December 31, 2014, the Company had $732.5 million aggregate principal outstanding of Debentures that generally require interest to be paid semiannually at a rate of 4.75% per year. The Debentures are convertible at any time on or prior to December 15, 2036 if any of the following conditions occur: (1) the Company’s closing common stock price exceeds 140% of the then applicable conversion price for the Debentures (currently $80.02 per share) for at least 20 of the final 30 trading days in any quarter; (2) a notice of redemption is issued with respect to the Debentures; (3) a change of control, as defined in the indenture governing the Debentures; (4) satisfaction of certain trading price conditions; and (5) other specified corporate transactions described in the indenture governing the Debentures. In addition, the Debentures are convertible at any time after December 15, 2036 to December 15, 2041, the scheduled maturity date. In the case of conversion following a notice of redemption or upon a non-stock change of control, as defined in the indenture governing the Debentures, holders may convert their Debentures into cash in the amount of the principal amount of their Debentures and shares of the Company’s common stock for any conversion value in excess of the principal amount. In all other conversion circumstances, holders will receive perpetual preferred stock (see Note 17. "Stockholders' Equity") with a liquidation preference equal to the principal amount of their Debentures, and any conversion value in excess of the principal amount will be settled with the Company’s common stock. As a result of the Patriot spin-off, the conversion rate was adjusted. The conversion rate has also been adjusted when there has been a change in the Company’s dividend distribution rate. The current conversion rate is 17.4967 shares of common stock per $1,000 principal amount of Debentures effective February 4, 2015. This adjusted conversion rate represents a conversion price of $57.15.
	Between December 20, 2011 and December 19, 2036, the Company may redeem the Debentures, in whole or in part, if for at least 20 out of the 30 consecutive trading days immediately prior to the date on which notice of redemption is given, the Company’s closing common stock price has exceeded 130% of the then applicable conversion price for the Debentures (currently $74.30 per share). On or after December 20, 2036, whether or not the redemption condition is satisfied, the Company may redeem the Debentures, in whole or in part. The Company may not redeem any Debentures unless (1) all accrued and unpaid interest on the Debentures has been paid in full on or prior to the redemption date and (2) if any perpetual preferred stock is outstanding, the Company has first given notice to redeem the perpetual preferred stock in the same proportion as the redemption of the Debentures. Any redemption of the Debentures will be at a cash redemption price of 100% of the principal amount of the Debentures to be redeemed, plus accrued and unpaid interest to the date of redemption.
	On December 15, 2041, the scheduled maturity date, the Company is required to use commercially reasonable efforts, subject to the occurrence of a market disruption event, as defined in the indenture governing the Debentures, to issue securities of equivalent equity content in an amount sufficient to pay the principal amount of the Debentures, together with accrued and unpaid interest. At the final maturity date of the Debentures on December 15, 2066, the entire principal amount will become due and payable, together with accrued and unpaid interest.
	In connection with the issuance of the Debentures, the Company entered into a Capital Replacement Covenant (the CRC). Pursuant to the CRC, the Company covenanted for the benefit of holders of covered debt, as defined in the CRC (currently the Company’s 7.875% Senior Notes, issued in an aggregate principal amount of $250.0 million), that neither the Company nor any of its subsidiaries shall repay, redeem or repurchase all or any part of the Debentures on or after December 15, 2041 and prior to December 15, 2046, except to the extent that the total repayment, redemption or repurchase price does not exceed the sum of: (1) 400% of the Company’s net cash proceeds from the sale of its common stock and rights to acquire its common stock (including common stock issued pursuant to the Company’s dividend reinvestment plan or employee benefit plans); (2) the Company’s net cash proceeds from the sale of its mandatorily convertible preferred stock, as defined in the CRC, or debt exchangeable for equity, as defined in the CRC; and (3) the Company’s net cash proceeds from the sale of other replacement capital securities, as defined in the CRC, in each case, during the six months prior to the notice date for the relevant payment, redemption or repurchase.
	The Debentures are unsecured obligations of the Company, ranking junior to all existing and future senior and subordinated debt (excluding trade accounts payable or accrued liabilities arising in the ordinary course of business) except for any future debt that ranks equal to or junior to the Debentures. The Debentures rank equal in right of payment with the Company’s obligations to trade creditors. In addition, the Debentures are effectively subordinated to all indebtedness of the Company’s subsidiaries. The indenture governing the Debentures places no limitation on the amount of additional indebtedness that the Company or any of the Company’s subsidiaries may incur, but do impose certain financial covenants. The Company was in compliance with all such covenants as of December 31, 2014.
In June 2014, the Company received sufficient consents from holders of the Debentures to amend the related indenture and eliminate the provisions relating to the mandatory and optional deferral of interest, thereby providing the Company greater financial and operational flexibility and increased ease of administration with respect to the Debentures. After receiving those consents, the Company entered into a supplemental indenture reflecting the amendments, which binds all holders of the Debentures. The eliminated provisions related to the mandatory deferral of interest (1) required that the Company defer interest payments on the Debentures under specified circumstances unless it obtained funds for those payments through the sale of qualifying warrants or qualifying preferred stock, (2) subject to limitations, required that the Company obtain the necessary funds through such a sale, and (3) prohibited the Company from making certain distributions (including dividends) with respect to its capital stock during any mandatory extension period (as defined in the original indenture governing the Debentures) and until the Company paid all accrued but unpaid interest on the Debentures. The eliminated provisions related to the optional deferral of interest allowed the Company to defer interest payments on the Debentures at its discretion, in certain circumstances.
Holders of the Debentures that validly consented to the amendments received a consent fee of $15.00 per $1,000 principal amount of the Debentures. The Company paid aggregate consent fees of $10.1 million in June 2014 in connection with the Debentures consent solicitation, which will be amortized over the remaining term of the Debentures. Additionally, the Company incurred $1.6 million in fees to third parties related to the consent solicitation and supplemental indenture, which were classified in "Interest expense" in the consolidated statement of operations for the year ended December 31, 2014.
The Company accounts for the liability and equity components of the Debentures in a manner that reflects the nonconvertible debt borrowing rate when recognizing interest cost in subsequent periods. The following table illustrates the carrying amount of the equity and debt components of the Debentures:


	December 31,
	2014			2013
	(Dollars in millions)
Carrying amount of the equity component	$	215.4		$	215.4
Carrying amount of the equity component	$	215.4		$	215.4

Principal amount of the liability component	$	732.5		$	732.5
Principal amount of the liability component	$	732.5		$	732.5
Unamortized discount	(350.2		)	(352.8		)
Net carrying amount	$	382.3		$	379.7
Net carrying amount	$	382.3		$	379.7
The following table illustrates the effective interest rate and the interest expense related to the Debentures:


	Year Ended December 31,
	2014			2013			2012
	(Dollars in millions)
Effective interest rate	4.9		%	4.9		%	4.9		%
Interest expense — contractual interest coupon	$	34.8		$	34.8		$	34.8
Interest expense — contractual interest coupon	$	34.8		$	34.8		$	34.8
Interest expense — amortization of debt discount	2.6			2.3			2.1
Interest expense — amortization of debt discount	2.6			2.3			2.1
The remaining period over which the discount will be amortized is 27 years as of December 31, 2014.
Capital Lease Obligations
In June 2013, the Company executed an amendment to its master equipment hire agreement with an unconsolidated equity affiliate in Australia to allow for the legal right of offset of receivables and payables due between parties. The operations of that equity affiliate are funded through equity interests and shareholder loans for the purpose of purchasing on behalf of and leasing equipment to its shareholders. Because the Company intends to use the right of offset provided by that amendment, $38.0 million of capital lease obligations due to that equity affiliate have been presented on a net basis in the consolidated balance sheet as of December 31, 2014 and offset against the related shareholder loans due from that equity affiliate included in "Investments and other assets." Prior to the amendment, such amounts were presented on a gross basis in the Company's consolidated financial statements.
Refer to Note 13. "Leases" for additional information associated with the Company's capital leases, which pertain to the financing of mining equipment used in operations.
Debt Maturities, Interest Paid and Financing Costs
The aggregate amounts of long-term debt maturities (including unamortized debt discounts) subsequent to December 31, 2014, including capital lease obligations, were as follows:




Year of Maturity		(Dollars in millions)
2015		$	21.2
2015		$	21.2
2016		669
2016		669
2017		12.9
2017		12.9
2018		1,530.90
2018		1,530.90
2019		12.1
2019		12.1
2020 and thereafter		3,740.70
2020 and thereafter		3,740.70
Total		$	5,986.80
Total		$	5,986.80
Interest paid on long-term debt was $404.4 million, $388.2 million and $396.1 million for the years ended December 31, 2014, 2013 and 2012, respectively.
Financing costs incurred with the issuance of the Company’s debt are being amortized to interest expense over the remaining term of the associated debt. The remaining balance at December 31, 2014 was $88.7 million, of which $62.4 million will be amortized to interest expense over the next five years.

Leases

Leases	12 Months Ended
	Dec. 31, 2014
Leases [Abstract]
Leases	Leases
	The Company leases equipment and facilities under various noncancelable lease agreements. Certain lease agreements require the maintenance of specified ratios and are subject to the restrictive covenants of the Company's credit facilities. Rental expense under operating leases, including expense related to short-term operating leases, was $306.0 million, $305.9 million and $247.5 million for the years ended December 31, 2014, 2013 and 2012, respectively. One of the Company's operating lease agreements for underground mining equipment in Australia entered into in 2013 requires contingent rent to be paid only if and when certain coal is mined at a specified margin as defined in the agreements. There was no contingent expense related to that arrangement for the years ended December 31, 2014 and 2013. The gross value of property, plant, and equipment under capital leases was $175.1 million as of December 31, 2014 and 2013, related primarily to the leasing of mining equipment. The accumulated depreciation for these items was $138.4 million and $111.3 million at December 31, 2014 and 2013, respectively, and changes thereto have been included in "Depreciation, depletion and amortization" in the consolidated statements of operations.
	The Company also leases coal reserves under agreements that require royalties to be paid as the coal is mined. Certain agreements also require minimum annual royalties to be paid regardless of the amount of coal mined during the year. Total royalty expense was $507.8 million, $546.0 million and $637.5 million for the years ended December 31, 2014, 2013 and 2012, respectively.
	A substantial amount of the coal mined by the Company is produced from mineral reserves leased from the owner. One of the major lessors is the U.S. government, from which the Company leases substantially all of the coal it mines in Wyoming under terms set by Congress and administered by the U.S. Bureau of Land Management. These leases are generally for an initial term of ten years but may be extended by diligent development and mining of the reserves until all economically recoverable reserves are depleted. The Company has met the diligent development requirements for substantially all of these federal leases either directly through production, by including the lease as a part of a logical mining unit with other leases upon which development has occurred, or by paying an advance royalty in lieu of continued operations. Annual production on these federal leases must total at least 1.0% of the leased reserve or the original amount of coal in the entire logical mining unit in which the leased reserve resides. In addition, royalties are payable monthly at a rate of 12.5% of the gross realization from the sale of the coal mined using surface mining methods and at a rate of 8.0% of the gross realization for coal produced using underground mining methods. The Company also leases coal reserves in Arizona from The Navajo Nation and the Hopi Tribe under leases that are administered by the U.S. Department of the Interior. These leases expire upon exhaustion of the leased reserves or upon the permanent ceasing of all mining activities on the related reserves as a whole. The royalty rates are also generally based upon a percentage of the gross realization from the sale of coal. These rates are subject to redetermination every ten years under the terms of the leases. The remainder of the leased coal is generally leased from state governments, land holding companies and various individuals. The duration of these leases varies greatly. Typically, the lease terms are automatically extended as long as active mining continues. Royalty payments are generally based upon a specified rate per ton or a percentage of the gross realization from the sale of the coal.
	Mining and exploration in Australia is generally conducted under leases, licenses or permits granted by state governments. Mining leases are typically for an initial term of up to 21 years (but may be renewed) and contain conditions relating to such matters as minimum annual expenditures, environmental compliance, restoration and rehabilitation. Royalties are paid to the state government as a percentage of the sales price (less certain allowable deductions in some cases). Generally landowners do not own the mineral rights or have the ability to grant rights to mine those minerals. These rights are retained by state governments. Compensation is often payable to landowners and occupiers for the loss of access to the land and any impact on the value of the land where the landowner retains the surface rights, and the amount and type of compensation can be determined by agreement or court determination, as provided by law. Surface rights may be acquired directly from landowners by mutual agreement.
	Future minimum lease and royalty payments as of December 31, 2014 are as follows:


		Capital		Operating		Coal Lease
		Leases		Leases		and
						Royalty
	Year Ending December 31,					Obligations
		(Dollars in millions)
	2015	$	9.5	$	207.2	$	284.6

	2016	6.9		196		253.3

	2017	1.4		178.9		22.3

	2018	0.5		104.3		20.5

	2019	0.5		51.3		18.2

	2020 and thereafter	10.6		64.3		29

	Total minimum lease payments	29.4		$	802	$	627.9

	Less interest	7.2

	Present value of minimum capital lease payments	$	22.2

	As of December 31, 2014, certain of the Company’s coal lease obligations were secured by outstanding surety bonds totaling $103.8 million.

Asset_Retirement_Obligations

Asset Retirement Obligations	12 Months Ended
	Dec. 31, 2014
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligations	Asset Retirement Obligations
	Reconciliations of the Company’s asset retirement obligations are as follows:


		December 31,
		2014			2013
		(Dollars in millions)
	Balance at beginning of year	$	712.8		$	687.5

	Liabilities incurred or acquired	22.7			—

	Liabilities settled or disposed	(19.7		)	(15.4		)
	Accretion expense	39.3			39.3

	Revisions to estimates	(2.6		)	1.4

	Balance at end of year	$	752.5		$	712.8

	Less: Current portion (included in "Accounts payable and accrued expenses")	30.2			21

	Noncurrent obligation (included in "Asset Retirement Obligations")	722.3			691.8

	Balance at end of year — active locations	$	676.2		$	660.8

	Balance at end of year — closed or inactive locations	$	76.3		$	52

	In 2014, the Company recognized an asset retirement obligation of $22.2 million due to the nonperformance of a contract miner at a coal reserve property in the Eastern U.S. Because mining operations have ceased at that operation, a corresponding charge was recorded to “Asset retirement obligation expenses” in the consolidated statement of operations for the year ended December 31, 2014.
	The credit-adjusted, risk-free interest rates were 6.82%, 6.44% and 6.28% at December 31, 2014, 2013 and 2012, respectively.
	As of December 31, 2014 and 2013, the Company had $645.0 million and $568.4 million, respectively, in surety bonds and bank guarantees outstanding to secure reclamation obligations. The amount of reclamation self-bonding in certain states in which the Company qualifies was $1,361.4 million and $1,365.1 million as of December 31, 2014 and 2013, respectively. Additionally, the Company had $17.6 million of letters of credit in support of reclamation obligations as of December 31, 2014 and 2013.

Postretirement_Health_Care_and

Postretirement Health Care and Life Insurance Benefits	12 Months Ended
	Dec. 31, 2014
Postretirement Health Care and LIfe Insurance Benefits [Abstract]
Postretirement Health Care and Life Insurance Benefits	Postretirement Health Care and Life Insurance Benefits
	The Company currently provides health care and life insurance benefits to qualifying salaried and hourly retirees and their dependents from benefit plans established by the Company. Plan coverage for health benefits is provided to future hourly and salaried retirees in accordance with the applicable plan document. Life insurance benefits are provided to future hourly retirees in accordance with the applicable labor agreement.
	Net periodic postretirement benefit cost included the following components:


		Year Ended December 31,
		2014				2013			2012
		(Dollars in millions)
	Service cost for benefits earned	$	12.2			$	15.8		$	14.9

	Interest cost on accumulated postretirement benefit obligation	36.4				41.8			54.9

	Amortization of prior service cost (credit)	1.3				(1.7		)	2.5

	Amortization of actuarial loss	14.5				24.1			32.8

	Settlement related to the Patriot bankruptcy reorganization (1)	—				63.2			—

	Special termination benefits (2)	1.6				0.9			—

	Net periodic postretirement benefit cost	$	66			$	144.1		$	105.1


	-1	Refer to Note 25. "Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation" herein for additional details related to this transaction.

	-2	Reflected in "Restructuring and pension settlement charges" in the consolidated statement of operations for the year ended December 31, 2014.
	The following includes pre-tax amounts recorded in "Accumulated other comprehensive loss":


		Year Ended December 31,
		2014				2013			2012
		(Dollars in millions)
	Net actuarial loss (gain) arising during year	$	115.8			$	(24.3	)	$	(68.3	)

	Prior service credit arising during year	(18.0		)		—			(31.9		)

	Amortization:

	Actuarial loss	(14.5		)		(24.1		)	(32.8		)
	Prior service (cost) credit	(1.3		)		1.7			(2.5		)

	Settlement related to the Patriot bankruptcy reorganization: (1)
	Actuarial loss	—				(61.3		)	—

	Prior service cost	—				(1.9		)	—

	Total recorded in other comprehensive loss (income)	$	82			$	(109.9	)	$	(135.5	)


	-1	Refer to Note 25. "Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation" herein for additional details related to this transaction.
	The Company amortizes actuarial gain and loss using a 0% corridor with an amortization period that covers the average future working lifetime of active employees (11.70 years and 11.96 years at January 1, 2015 and 2014, respectively). The estimated net actuarial loss and prior service credit that will be amortized from accumulated other comprehensive (loss)income into net periodic postretirement benefit cost during the year ending December 31, 2015 are $24.9 million and $6.8 million, respectively.
	The following table sets forth the plans' funded status reconciled with the amounts shown in the consolidated balance sheets:


		December 31,
		2014				2013
		(Dollars in millions)
	Change in benefit obligation:

	Accumulated postretirement benefit obligation at beginning of period	$	735.4			$	1,026.10

	Service cost	12.2				15.8

	Interest cost	36.4				41.8

Participant contributions	2.2				2.3

Plan changes(1)	(18.0		)		—

Benefits paid	(46.5		)		(66.5		)
Actuarial loss (gain) (2)	115.8				(24.3		)

Settlement related to the Patriot bankruptcy reorganization (3)	—				(260.7		)

Special termination benefits	1.6				0.9

Accumulated postretirement benefit obligation at end of period	839.1				735.4

Change in plan assets:

Fair value of plan assets at beginning of period	—				—

Employer contributions	44.3				64.2

Participant contributions	2.2				2.3

Benefits paid and administrative fees (net of Medicare Part D reimbursements)	(46.5		)		(66.5		)
Fair value of plan assets at end of period	—				—

Funded status at end of year	(839.1		)		(735.4		)
Less: Current portion (included in "Accounts payable and accrued expenses")	57.2				51.4

Noncurrent obligation (included in "Accrued postretirement benefit costs")	$	(781.9	)		$	(684.0	)

(1)	Includes the net impact of the following plan changes: a $45.4 million reduction to the benefit obligation related to various plan changes effective January 1, 2015 for certain plan participants that are designed to bring consistency amongst the various retiree medical programs; and a $27.6 million increase to the benefit obligation resulting from a plan change effective April 1, 2014 for certain plan participants' benefits no longer funded through a Medicare Advantage Program. The plan changes will not affect participant benefits.

(2)	During 2014, the Company reviewed its demographic assumptions (including mortality, retirements and terminations) in conjunction with the recently-issued mortality tables published by the Society of Actuaries, to select assumptions that are aligned with the Company’s experience. The updated demographic assumptions increased the December 31, 2014 benefit obligation by approximately $63 million.

(3)	Refer to Note 25. "Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation" herein for additional details related to this transaction.
The weighted-average assumptions used to determine the benefit obligations as of the end of each year were as follows:


	December 31,
	2014			2013
Discount rate	4.1	%		4.9	%
Measurement date	December 31, 2014			December 31, 2013

The weighted-average assumptions used to determine net periodic benefit cost during each year were as follows:


	Year Ended December 31,
	2014			2013			2012
Discount rate	4.9	%		4.21	%		5.05	%
Measurement date	December 31, 2013			December 31, 2012			December 31, 2011

The following presents information about the assumed health care cost trend rate:


	Year Ended December 31,
	2014			2013
Pre-Medicare:
Health care cost trend rate assumed for next year	7	%		6.26	%
Rate to which the cost trend is assumed to decline (the ultimate trend rate)	4.75	%		4.67	%
Year that the rate reaches the ultimate trend rate	2021			2023


Post-Medicare:
Health care cost trend rate assumed for next year	6	%		6.26	%
Rate to which the cost trend is assumed to decline (the ultimate trend rate)	4.75	%		4.67	%
Year that the rate reaches the ultimate trend rate	2021			2023

Assumed health care cost trend rates have a significant effect on the expense and liability amounts reported for health care plans. A one-percentage-point change in the assumed health care cost trend would have the following effects:


	One Percentage-				One Percentage-
	Point Increase				Point Decrease
	(Dollars in millions)
Effect on total service and interest cost components (1)	$	4.1			$	(3.8	)

Effect on total postretirement benefit obligation (1)	$	80.6			$	(70.3	)


(1)	In addition to the effect on total service and interest cost components of expense, changes in trend rates would also increase or decrease the actuarial gain or loss amortization expense component. The impact on actuarial gain or loss amortization would approximate the increase or decrease in the obligation divided by 11.70 years at January 1, 2015.
Plan Assets
The Company’s postretirement benefit plans are unfunded.
Estimated Future Benefit Payments
The following benefit payments (net of retiree contributions), which reflect expected future service, as appropriate, are expected to be paid by the Company:


	Postretirement
	Benefits
	(Dollars in millions)
2015	$	57.2

2016	59

2017	59.9

2018	60.4

2019	60.7

Years 2020-2024	297.6

Pension_and_Savings_Plans

Pension and Savings Plans	12 Months Ended
	Dec. 31, 2014
Pension and Savings Plans [Abstract]
Pension and Savings Plans	Pension and Savings Plans
	One of the Company’s subsidiaries, Peabody Investments Corp. (PIC), sponsors a defined benefit pension plan covering certain U.S. salaried employees and eligible hourly employees at certain PIC subsidiaries (the Peabody Plan). A subsidiary of PIC also has a defined benefit pension plan covering eligible employees who are represented by the United Mine Workers of America (UMWA) under the Western Surface Agreement (the Western Plan). PIC also sponsors an unfunded supplemental retirement plan to provide senior management with benefits in excess of limits under the federal tax law (collectively, the Plans).
	Effective May 31, 2008, the Peabody Plan was frozen in its entirety for both participation and benefit accrual purposes. The Company adopted an enhanced savings plan contribution structure in lieu of benefits formerly accrued under the Peabody Plan. In August 2014, the Company announced a program to offer voluntary lump-sum pension payout options to eligible former salaried employees in the Peabody Plan that, if accepted, would settle the Company’s obligation to them. The program provided participants with a one-time choice of electing to receive a lump-sum settlement of their pension benefit. As part of this voluntary lump-sum program, the Company settled $41.7 million of its pension obligations for U.S. salaried retirees and former salaried employees in the Peabody Plan with an equal amount paid from plan assets. As a result, the Company recorded a settlement charge of $8.7 million reflecting the accelerated recognition of unamortized actuarial losses in the Peabody Plan proportionate to the obligation that was settled. The settlement charge was reflected in “Restructuring and pension settlement charges” on the consolidated statement of operations with a corresponding reduction in “Accumulated other comprehensive loss” on the consolidated balance sheet.
	Net periodic pension cost included the following components:


		Year Ended December 31,
		2014				2013				2012
		(Dollars in millions)
	Service cost for benefits earned	$	2.1			$	2.2			$	2

	Interest cost on projected benefit obligation	45.4				42.2				46.7

	Expected return on plan assets	(54.3		)		(59.5		)		(63.7		)
	Amortization of prior service cost	1.3				1				1

	Amortization of net actuarial losses	30.2				65.7				48.6

	Settlement charge	8.7				—				—

	Total net periodic pension cost	$	33.4			$	51.6			$	34.6

	The following includes pre-tax amounts recorded in "Accumulated other comprehensive loss":


		Year Ended December 31,
		2014				2013				2012
		(Dollars in millions)
	Net actuarial loss (gain) arising during year	$	79.2			$	(133.8	)		$	67.6

	Prior service cost arising during year	—				2.2				—

	Amortization:

	Net actuarial loss	(30.2		)		(65.7		)		(48.6		)
	Prior service cost	(1.3		)		(1.0		)		(1.0		)
	Settlement charge	(8.7		)		—				—

	Total recorded in other comprehensive loss (income)	$	39			$	(198.3	)		$	18


	The Company amortizes actuarial gain and loss using a 5% corridor with a five-year amortization period. The estimated net actuarial loss and prior service cost that will be amortized from "Accumulated other comprehensive loss" into net periodic pension cost during the year ending December 31, 2015 are $39.6 million and $1.0 million, respectively.
	The following summarizes the change in benefit obligation, change in plan assets and funded status of the Plans:


		December 31,
		2014				2013
		(Dollars in millions)
	Change in benefit obligation:

	Projected benefit obligation at beginning of period	$	947.3			$	1,058.60

	Service cost	2.1				2.2

	Interest cost	45.4				42.2

	Benefits paid	(57.2		)		(59.1		)
	Actuarial loss (gain) (1)	106.6				(98.8		)

	Plan amendments	—				2.2

	Settlement	(41.7		)		—

	Projected benefit obligation at end of period	1,002.50				947.3

Change in plan assets:

Fair value of plan assets at beginning of period	851.4				813.7

Actual return on plan assets	81.7				94.5

Employer contributions	5.6				2.3

Benefits paid	(57.2		)		(59.1		)
Settlement	(41.7		)		—

Fair value of plan assets at end of period	839.8				851.4

Funded status at end of year	$	(162.7	)		$	(95.9	)
Amounts recognized in the consolidated balance sheets:

Current obligation (included in "Accounts payable and accrued expenses")	$	(1.7	)		$	(1.7	)
Noncurrent obligation (included in "Other noncurrent liabilities")	(161.0		)		(94.2		)
Net amount recognized	$	(162.7	)		$	(95.9	)
(1) During 2014, the Company reviewed its demographic assumptions (such as mortality, retirements and terminations) in conjunction with the recently-issued mortality tables published by the Society of Actuaries, to select assumptions that are aligned with the Company’s experience. The updated demographic assumptions increased the December 31, 2014 benefit obligation by approximately $36 million. The weighted-average assumptions used to determine the benefit obligations as of the end of each year were as follows:


	December 31,
	2014			2013
Discount rate	4.15	%		4.95	%
Measurement date	December 31, 2014			December 31, 2013

The weighted-average assumptions used to determine net periodic benefit cost during each year were as follows:


	Year Ended December 31,
	2014			2013			2012
Discount rate	4.95	%		4.1	%		5	%
Expected long-term return on plan assets	6.85	%		7.75	%		8	%
Measurement date	December 31, 2013			December 31, 2012			December 31, 2011

The expected rate of return on plan assets is determined by taking into consideration expected long-term returns associated with each major asset class based on long-term historical ranges, inflation assumptions and the expected net value from active management of the assets based on actual results. Effective January 1, 2015, the Company lowered its expected rate of return on plan assets from 6.85% to 6.25%, reflecting the impact of the Company's asset allocation and capital market expectations.
The projected benefit obligation and the accumulated benefit obligation exceeded plan assets for all plans as of December 31, 2014 and 2013. The accumulated benefit obligation for all plans was $1,002.5 million and $947.3 million as of December 31, 2014 and 2013, respectively.
Assets of the Plans
Assets of the PIC Master Trust (the Master Trust) are invested in accordance with investment guidelines established by the Peabody Plan Retirement Committee and the Western Plan Retirement Committee (collectively, the Retirement Committees) after consultation with outside investment advisors and actuaries.
The asset allocation targets have been set with the expectation that the assets of the Master Trust will be managed with an appropriate level of risk to fund each Plan's expected liabilities. To determine the appropriate target asset allocations, the Retirement Committees consider the demographics of each Plan's participants, the funded status of each Plan, the business and financial profile of the Company and other associated risk preferences. These allocation targets are reviewed by the Retirement Committees on a regular basis and revised as necessary. In 2013, the Retirement Committees developed and implemented a dynamic asset-liability management investment strategy (the Dynamic Investment Strategy) designed to reduce each Plan's funded status volatility risk as funded status increases resulting from changes in liabilities due to discount rates and other factors, investment returns and funding contributions. The Dynamic Investment Strategy adjusts allocations between return-seeking (i.e., equities and other similar investments) and liability hedging (i.e., fixed income duration and spread exposure) portfolios in a pre-established manner, with changes triggered when the Plans reach certain funded status thresholds. The Company sold equity securities and invested in various fixed income investments throughout 2013 in accordance with its Dynamic Investment Strategy. As of December 31, 2014 and 2013, the Master Trust assets’ investment portfolio reflected the Company's target asset mix of 35% equity securities and 65% fixed income investments. Master Trust assets also include funds invested in various real estate properties representing approximately 4% of total Master Trust assets as of December 31, 2014 and 2013. The Retirement Committees' intention is to liquidate these real estate holdings when allowable per the terms of the limited partnership agreements. Generally, dissolution and liquidation of the limited partnerships is required before the Master Trust’s real estate holdings can be liquidated and is estimated to occur at various times through 2021.
Assets of the Master Trust are either under active management by third-party investment advisors or in index funds, all of which are selected and monitored by the Retirement Committees. Specific investment guidelines have been established by the Retirement Committees for each major asset class including performance benchmarks, allowable and prohibited investment types and concentration limits. In general, investment guidelines do not permit leveraging the assets held in the Master Trust. However, investment managers may employ various strategies and derivative instruments in establishing overall portfolio characteristics consistent with the guidelines and investment objectives established by the Retirement Committees for their portfolios. Equity investment guidelines do not permit entering into put or call options (except as deemed appropriate to manage currency risk), and futures contracts are permitted only to the extent necessary to facilitate liquidity management. Fixed income investment guidelines only allow for exchange-traded derivatives if the investment manager deems the derivative vehicle to be more attractive than a similar direct investment in an underlying cash market or to manage the duration of the fixed income portfolio.
A financial instrument’s level within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. Following is a description of the valuation techniques and inputs used for investments measured at fair value, including the general classification of such investments pursuant to the valuation hierarchy.
U.S. equity securities. The Master Trust invests in U.S. equity securities for growth and diversification. Investment vehicles include a mutual fund (benchmarked against the performance of the S&P 500 Index) that invests in large-cap publicly traded common stocks and a common/collective trust (benchmarked against the performance of the Russell 2000 Index) that invests in small-cap publicly traded common stocks. The mutual fund, which is traded on a national securities exchange in an active market, is valued using daily publicly quoted net asset value (NAV) prices and accordingly classified within Level 1 of the valuation hierarchy. The common/collective trust (CCT), which is not publicly traded on a national securities exchange, is valued using a NAV that is based on a derived price in an active market and accordingly classified within Level 2 of the valuation hierarchy. U.S. equity securities are not subject to liquidity redemption restrictions.
International equity securities. The Master Trust invests in international equity securities for growth and diversification. Investment vehicles include a CCT that invests in publicly traded non-U.S. equity securities (the Equity CCT) and another CCT (benchmarked against the performance of the MSCI Emerging Markets Index) that primarily invests in equity index securities of companies in global emerging markets (the Equity Index CCT), collectively, the CCTs. Equity and equity index securities within both CCTs are valued using the closing price reported by their primary stock exchange and translated at each valuation date from local currency into U.S. dollars based on independently published currency exchange rates. The NAV is determined in U.S. dollars and calculated as of the last business day of each month for the Equity CCT and daily for the Equity Index CCT. Both CCTs are classified within the Level 2 valuation hierarchy since NAV is based on a derived price in an active market and is not traded on a national securities exchange. Redemptions for both CCTs are at NAV. Equity CCT redemptions can only occur on the first business day of each month subject to a notification period and minimum withdrawal limits. Equity Index CCT redemptions can occur daily.
Debt securities. The Master Trust invests in debt securities for diversification, volatility reduction of equity securities and to provide a hedge to interest rate movements affecting liabilities. Investment vehicles include numerous U.S. government and agency securities, investment-grade corporate bonds, U.S. municipal bonds, non-U.S. government bonds and an institutional mutual fund that holds a diversified portfolio of long-duration corporate fixed income investments. Fair value for these securities is provided by a third-party pricing service that utilizes various inputs such as benchmark yields, reported trades, broker/dealer quotes, issuer spreads and benchmark securities as well as other relevant economic measures. If fair value is based on quoted prices in active markets and traded on a national securities exchange, debt securities are classified within the Level 1 valuation hierarchy; otherwise, debt securities are classified within the Level 2 valuation hierarchy. NAV for the institutional mutual fund is calculated daily in actively traded markets and is classified within the Level 2 valuation hierarchy since fair value inputs are derived prices in active markets and the fund is not traded on a national securities exchange. Debt securities are not subject to liquidity redemption restrictions.
Short-term investments. The Master Trust invests in short-term investments to manage liquidity resulting from payment of participant benefits and certain administrative fees. Investment vehicles primarily include a non-interest bearing cash fund with an earnings credit allowance feature; an institutional mutual fund that consists of a diversified portfolio of liquid, short-term instruments of varying maturities; and various exchange-traded derivative instruments consisting of futures and interest rate swap agreements used to manage the duration of certain liability-hedging investments. The non-interest bearing cash fund is classified within the Level 1 valuation hierarchy. The institutional mutual fund is classified within the Level 2 valuation hierarchy since fair value inputs are derived prices in active markets and the fund is not traded on a national securities exchange. Exchange traded derivatives, such as options and futures, for which market quotations are readily available, are valued at the last reported sale price or official closing price on the primary market or exchange on which they are traded and are classified within the Level 1 valuation hierarchy. Short-term investments are not subject to liquidity redemption restrictions.
Interests in real estate. The Master Trust invests in real estate interests for diversification. Investments in real estate represent interests in several limited partnerships, which invest in various real estate properties. Interests in real estate are valued using various methodologies, including independent third party appraisals; fair value measurements are not developed by the Company. For some investments, little market activity may exist and determination of fair value is then based on the best information available in the circumstances. This involves a significant degree of judgment by taking into consideration a combination of internal and external factors. Accordingly, interests in real estate are classified within the Level 3 valuation hierarchy. Some limited partnerships issue dividends to their investors in the form of cash distributions that the Plans invest elsewhere within the Master Trust. Certain interests in real estate are subject to liquidity redemption restrictions and voluntary redemptions are generally not permitted. Upon liquidation of the limited partnerships, redemptions will generally be in the form of cash distributions and invested elsewhere within the Master Trust.
The methods described above may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. Furthermore, while the Company believes its valuation methods are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different fair value measurement at the reporting date. The inputs or methodologies used for valuing investments are not necessarily an indication of the risk associated with investing in those investments.
The following tables present the fair value of assets in the Master Trust by asset category and by fair value hierarchy:


	December 31, 2014
	Level 1				Level 2				Level 3				Total
	(Dollars in millions)
U.S. equity securities	$	141.7			$	48.6			$	—			$	190.3

International equity securities	—				69.8				—				69.8

U.S. debt securities	25.3				29.1				—				54.4

International debt securities	—				23.5				—				23.5

Corporate debt securities	—				447.8				—				447.8

Short-term investments	17.5				6.3				—				23.8

Interests in real estate	—				—				30.2				30.2

Total assets at fair value	$	184.5			$	625.1			$	30.2			$	839.8



	December 31, 2013
	Level 1				Level 2				Level 3				Total
	(Dollars in millions)
U.S. equity securities	$	141.8			$	54.2			$	—			$	196

International equity securities	—				80.6				—				80.6

U.S. debt securities	30.6				30.7				—				61.3

International debt securities	—				21.9				—				21.9

Corporate debt securities	—				424.3				—				424.3

Short-term investments	23.9				13.5				—				37.4

Interests in real estate	—				—				29.9				29.9

Total assets at fair value	$	196.3			$	625.2			$	29.9			$	851.4

The table below sets forth a summary of changes in the fair value of the Master Trust’s Level 3 investments:


	Year Ended December 31,
	2014				2013
	(Dollars in millions)
Balance, beginning of year	$	29.9			$	27.8

Realized gains	0.2				0.7

Unrealized gains relating to investments still held at the reporting date	4.9				2.6

Purchases, sales and settlements, net	(4.8		)		(1.2		)
Balance, end of year	$	30.2			$	29.9

Contributions
Annual contributions to qualified plans are made in accordance with minimum funding standards and the Company's agreement with the Pension Benefit Guaranty Corporation (PBGC). Funding decisions also consider certain funded status thresholds defined by the Pension Protection Act of 2006 (generally 80%). During the year ended December 31, 2014, the Company contributed $3.9 million and $1.7 million, respectively, to its qualified and non-qualified pension plans. As of December 31, 2014, the Company's qualified plans are expected to be at or above the Pension Protection Act thresholds and will therefore avoid benefit restrictions and at-risk penalties for 2015. On August 8, 2014, the Highway and Transportation Funding Act of 2014 (HATFA) was signed into law, which extends pension funding stabilization provisions that were part of the Moving Ahead for Progress in the 21st Century Act of 2012 (MAP-21) passed on July 6, 2012. Under HATFA, the pension funding stabilization provisions temporarily increased the interest rates used to determine pension liabilities for purposes of minimum funding requirements through 2017. Similar to MAP-21, HATFA is not expected to change the Company's total required cash contributions over the long term, but is expected to reduce the Company's required cash contributions through 2017 if current interest rate levels persist. Based upon revised minimum funding requirements in accordance with HATFA, the Company expects to contribute approximately $4.8 million to its pension plans to meet minimum funding requirements for its qualified plans and benefit payments for its non-qualified plans in 2015.
Estimated Future Benefit Payments
The following benefit payments, which reflect expected future service, as appropriate, are expected to be paid by the Master Trust:


	Pension Benefits
	(Dollars in millions)
2015	$	62.2

2016	63

2017	63.6

2018	64.2

2019	64.1

Years 2020-2024	327.7

Defined Contribution Plans
The Company sponsors employee retirement accounts under three 401(k) plans for eligible U.S. employees. The Company matches voluntary contributions to each plan up to specified levels. The expense for these plans was $44.7 million, $46.4 million and $51.1 million for the years ended December 31, 2014, 2013 and 2012, respectively. A performance contribution feature in one of the plans allows for additional contributions from the Company based upon meeting specified Company performance targets. Performance contributions paid during the years ended December 31, 2014, 2013 and 2012 were $18.3 million, $16.5 million and $22.5 million, respectively.

Stockholders_Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2014
Stockholders' Equity Attributable to Parent [Abstract]
Stockholders' Equity	Stockholders’ Equity
	Common Stock
	The Company has 800.0 million authorized shares of $0.01 par value common stock. Holders of common stock are entitled to one vote per share on all matters to be voted upon by the stockholders. The holders of common stock do not have cumulative voting rights in the election of directors. Holders of common stock are entitled to receive ratably dividends if, as and when dividends are declared from time to time by the Company’s Board of Directors out of funds legally available for that purpose, after payment of dividends required to be paid on outstanding preferred stock or series common stock, as described below. Upon liquidation, dissolution or winding up, any business combination or a sale or disposition of all or substantially all of the assets, the holders of common stock are entitled to receive ratably the assets available for distribution to the stockholders after payment of liabilities and accrued but unpaid dividends and liquidation preferences on any outstanding preferred stock or series common stock. The common stock has no preemptive or conversion rights and is not subject to further calls or assessment by the Company. There are no redemption or sinking fund provisions applicable to the common stock.
	The following table summarizes common stock activity from January 1, 2012 to December 31, 2014:


		2014		2013		2012
		(In millions)
	Shares outstanding at the beginning of the year	270.1		268.6		271.1

	Stock options exercised	—		0.1		0.2

	Stock grants to employees	1.3		1		1.5

	Employee stock purchases	0.5		0.5		0.3

	Shares relinquished	(0.2	)	(0.1	)	(0.3	)
	Shares repurchased	—		—		(4.2	)

	Shares outstanding at the end of the year	271.7		270.1		268.6

	Preferred Stock and Series Common Stock
	The Board of Directors is authorized to issue up to 10.0 million shares of preferred stock and up to 40.0 million shares of series common stock, both with a $0.01 per share par value. The Board of Directors can determine the terms and rights of each series, whether dividends (if any) will be cumulative or non-cumulative and the dividend rate of the series, redemption or sinking fund provisions, conversion terms, prices and rates and amounts payable on shares of the series in the event of any voluntary or involuntary liquidation, dissolution or winding up of the affairs of the Company and whether the shares of the series will be convertible into shares of any other class or series, or any other security, of the Company or any other corporation. The Board of Directors may also determine restrictions on the issuance of shares of the same series or of any other class or series, and the voting rights (if any) of the holders of the series. There were no outstanding shares of preferred stock or series common stock as of December 31, 2014.
	Perpetual Preferred Stock
	As discussed in Note 12. "Long-term Debt," the Company had $732.5 million aggregate principal amount of the Debentures outstanding as of December 31, 2014. Perpetual preferred stock issued upon a conversion of the Debentures will be fully paid and non-assessable, and holders will have no preemptive or preferential right to purchase any of the Company’s other securities. The perpetual preferred stock has a liquidation preference of $1,000 per share, is not convertible and is redeemable at the Company’s option at any time at a cash redemption price per share equal to the liquidation preference plus any accumulated dividends. Holders are entitled to receive cumulative dividends at an annual rate of 3.0875% if and when declared by the Company’s Board of Directors. If the Company fails to pay dividends on the perpetual preferred stock for five years, the Company generally must sell warrants or preferred stock with specified characteristics and use the funds from that sale to pay accumulated dividends after the payment in full of any deferred interest on the Debentures, subject to certain limitations. Additionally, holders of the perpetual preferred stock are entitled to elect two additional members to serve on the Company’s Board of Directors if (1) prior to any remarketing of the perpetual preferred stock, the Company fails to declare and pay dividends with respect to the perpetual preferred stock for 10 consecutive years or (2) after any successful remarketing or any final failed remarketing of the perpetual preferred stock, the Company fails to declare and pay six dividends thereon, whether or not consecutive. The perpetual preferred stock may be remarketed at the holder’s election after December 15, 2046 or earlier, upon the first occurrence of a change of control if the Company does not redeem the perpetual preferred stock. There were no outstanding shares of perpetual preferred stock as of December 31, 2014.
	Treasury Stock
	Share repurchases. The Company has a share repurchase program for its common stock with an authorized amount of $1.0 billion in which repurchases may be made from time to time based on an evaluation of the Company’s outlook and general business conditions, as well as alternative investment and debt repayment options (Repurchase Program). The Repurchase Program does not have an expiration date and may be discontinued at any time. Through December 31, 2014, the Company had made total repurchases of 7.7 million shares at a cost of $299.6 million ($199.8 million in 2008 and $99.8 million in 2006), leaving $700.4 million available under the Repurchase Program. No share repurchases were made under the Repurchase Program during the years ended December 31, 2014, 2013 and 2012.
	The Company’s Chairman and Chief Executive Officer had authority to direct the Company to repurchase up to $100.0 million of common stock outside of the share repurchase program. During the second quarter of 2012, the Company utilized existing cash on hand to repurchase 4.2 million shares of outstanding common stock for $99.9 million pursuant to that authority through open-market transactions.
	Shares relinquished. The Company routinely allows employees to relinquish common stock to pay estimated taxes upon the payout of performance units that are settled in common stock and the vesting of restricted stock. The number of shares of common stock relinquished was 0.2 million, 0.1 million and 0.3 million for the years ended December 31, 2014, 2013 and 2012, respectively. The value of the common stock tendered by employees was based upon the closing price on the dates of the respective transactions.

ShareBased_Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2014
Share-based Compensation [Abstract]
Share-Based Compensation	Share-Based Compensation
	The Company has an equity incentive plan for employees and non-employee directors that allows for the issuance of share-based compensation in the form of stock appreciation rights, restricted stock, performance awards, incentive stock options, nonqualified stock options, deferred stock units and restricted stock units. The plan made 14.0 million shares of the Company’s common stock available for grant, with 6.8 million shares available for grant as of December 31, 2014. The Company has two employee stock purchase plans that provide for the purchase of up to 6.0 million shares of the Company’s common stock, with 5.0 million shares authorized for purchase by U.S. employees and 1.0 million shares authorized for purchase by Australian employees.
	Share-Based Compensation Expense and Cash Flows
	The Company’s share-based compensation expense is recorded in “Selling and administrative expenses” in the consolidated statements of operations. Cash received by the Company upon the exercise of stock options and when employees purchase stock under the employee stock purchase plans is reflected as a financing activity in the consolidated statements of cash flows. Share-based compensation expense and cash flow amounts were as follows:


		Year Ended December 31,
		2014				2013				2012
		(Dollars in millions)
	Share-based compensation expense - equity classified awards	$	46.1			$	50.9			$	45.4

	Share-based compensation expense - liability classified awards	0.7				—				—

	Total share-based compensation expense	46.8				50.9				45.4

	Tax benefit	17.3				18.8				16.7

	Share-based compensation expense, net of tax benefit	29.5				32.1				28.7

	Cash received upon the exercise of stock options and from employee stock purchases	5.5				7.3				9.4

	(Write-off) excess tax benefits related to share-based compensation	(8.3		)		(4.5		)		8.3

	As of December 31, 2014, the total unrecognized compensation cost related to nonvested awards was $25.4 million, net of taxes, which is expected to be recognized over three years with a weighted-average period of 0.7 years.
	Deferred Stock Units
	In 2014, 2013 and 2012, the Company granted deferred stock units to each of its non-employee directors. The fair value of these units is equal to the market price of the Company’s common stock at the date of grant. These deferred stock units generally vest after one year and are settled in common stock on the specified distribution date elected by each non-employee director. Non-employee directors are also given the option to receive their total annual cash retainer in the form of additional deferred stock units (based on the fair market value of the Company's common stock on the date of grant). The additional grant of deferred stock units is subject to the same grant timing, vesting and distribution date elections as the annual equity compensation grant.
	Restricted Stock Awards
	The primary share-based compensation tool used by the Company for its employees is awards of restricted stock. The majority of restricted stock awards are granted in January of each year, with a lesser portion granted in the first month of the subsequent three quarters. Awards generally cliff vest after three years of service and only contain a service condition, with compensation cost recognized on a straight-line basis over the requisite service period, net of estimated forfeitures. For awards with service and performance conditions, the Company recognizes compensation cost using the graded-vesting method, net of estimated forfeitures. The fair value of restricted stock is equal to the market price of the Company’s common stock at the date of grant.
	A summary of restricted stock award activity is as follows:


		Year Ended			Weighted
		December 31,			Average
		2014			Grant-Date
					Fair Value
	Nonvested at December 31, 2013	2,493,046			$	34.6

	Granted	1,331,077			19.19

	Vested	(425,116	)		57.59

	Forfeited	(211,416	)		25.13

	Nonvested at December 31, 2014	3,187,591			$	25.63

	The total fair value of restricted stock awards granted during the years ended December 31, 2014, 2013 and 2012, was $25.5 million, $29.2 million and $44.4 million, respectively. The total fair value of restricted stock awards vested during the years ended December 31, 2014, 2013 and 2012, was $24.5 million, $13.2 million and $19.9 million, respectively.
	Restricted Stock Units
	In 2013, the Company began granting restricted stock units to certain senior management and non-senior management employees. One of the restricted stock unit grants contained market conditions valued utilizing a Monte Carlo simulation and was made as an inducement award for a certain senior management employee. The Monte Carlo simulation model incorporated the total stockholder return hurdles set for each grant and included the following assumptions: risk free interest rate of 1.7%; expected volatility of 48.1% and dividend yield of 1.6%. The Company grants restricted stock units to non-senior management employees who either met the Company's retirement eligibility guidelines or would meet the guidelines during the vesting period of the award. For units granted to both senior and non-senior management employees containing only service conditions, the fair value of the award is equal to the market price of the Company’s common stock at the date of grant. Units granted to non-senior management retirement-eligible employees vest quarterly. Units granted to senior management employees vest at various times (none of which exceed five years) in accordance with the underlying award agreement. Compensation cost for both senior and non-senior management employees is recognized on a straight-line basis over the requisite service period.
	A summary of restricted stock unit activity is as follows:


		Year Ended			Weighted
		December 31,			Average
		2014			Grant-Date
					Fair Value
	Nonvested at December 31, 2013	287,375			$	19.5

	Granted	218,017			19.48

	Vested	(3,261	)		23.56

	Forfeited	(5,025	)		21.4

	Nonvested at December 31, 2014	497,106			$	19.44

The total fair value of restricted stock units granted during the years ended December 31, 2014 and 2013 was $4.2 million and $7.6 million, respectively. The total fair value of restricted stock units vested during the years ended December 31, 2014 and 2013 was less than $0.1 million and $0.1 million, respectively.
Stock Options
The Company’s stock option awards have been primarily limited to senior management personnel. All stock options are granted at an exercise price equal to the market price of the Company’s common stock at the date of grant. Stock options generally vest in one-third increments over a period of three years or cliff vest after three years, and expire after 10 years from the date of grant. Expense is recognized ratably over the service period, net of estimated forfeitures. Option grants are typically made in January of each year or upon hire for eligible plan participants.
The Company used the Black-Scholes option pricing model to determine the fair value of stock options. The Company utilized U.S. Treasury yields as of the grant date for its risk-free interest rate assumption, matching the U.S. Treasury yield terms to the expected life of the option. The Company utilized historical company data to develop its dividend yield, expected volatility and expected option life assumptions.
A summary of outstanding option activity under the plans is as follows:


	Year Ended			Weighted				Weighted		Aggregate
	December 31,			Average				Average		Intrinsic
	2014			Exercise				Remaining		Value (in
				Price				Contractual		millions)
								Life
Options Outstanding at December 31, 2013	2,295,076			$	37.32			6		$	0.5

Granted	1,044,426			19.44

Exercised	(44,933	)		10.22

Forfeited	(278,556	)		36.9

Options Outstanding at December 31, 2014	3,016,013			$	31.57			6.39		$	—

Vested and Exercisable	1,594,695			$	40.2			4.37		$	—

During the years ended December 31, 2014, 2013 and 2012, the total intrinsic value of options exercised, defined as the excess fair value of the underlying stock over the exercise price of the options, was $0.4 million, $0.9 million and $4.2 million, respectively. The weighted-average fair values of the Company’s stock options and the assumptions used in applying the Black-Scholes option pricing model were as follows:


	Year Ended December 31,
	2014				2013				2012
Weighted-average fair value	$	7.38			$	12.13			$	18.59

Risk-free interest rate	1.7		%		0.7		%		0.9		%
Expected option life	5 years				5 years				5 years

Expected volatility	48.4		%		64.1		%		64		%
Dividend yield	1.7		%		1.2		%		0.6		%
Performance Units
Performance units are typically granted annually in January and vest over a three-year measurement period and are primarily limited to senior management personnel. The performance units are usually subject to the achievement of goals based on the following conditions or any combination thereof: three-year stock price performance compared to both an industry peer group and a S&P index (market condition) and/or three-year return on capital or mining asset targets (performance condition). Generally, three performance unit grants are outstanding for any given year. The payouts for active grants awarded in 2012 and 2013 will be settled in the Company’s common stock. All awards granted in 2014 will be settled in the Company's common stock with the exception of a grant awarded in 2014 to a certain senior management employee, which was later modified to be settled in cash instead of the Company's common stock. At the date of the modification, the Company reclassified the award from an equity award to a liability award. There was no incremental cost recognized since the fair value of the modified liability award at the modification date was less than the grant-date fair value of the original equity award. To the extent that the fair value of the modified liability award may exceed the recognized compensation cost associated with the grant-date fair value of the original equity award in the future, changes in the liability award’s fair value will be recognized as compensation cost prospectively.
A summary of performance unit activity is as follows:


	Year Ended			Weighted
	December 31,			Average
	2014			Remaining
				Contractual
				Life
Nonvested at December 31, 2013	463,317			1.6

Granted	644,412

Forfeited	(206,808	)
Vested	(150,769	)
Nonvested at December 31, 2014	750,152			1.5

As of December 31, 2014, there were 150,769 performance units vested that had an aggregate intrinsic value of $0.2 million and a conversion price per share of $7.98.
The performance condition awards were valued utilizing the grant date fair values of the Company’s stock adjusted for dividends foregone during the vesting period. The market condition awards were valued utilizing a Monte Carlo simulation which incorporates the total stockholder return hurdles set for each grant. The assumptions used in the valuations for grants were as follows:


	Year Ended December 31,
	2014			2013			2012
Risk-free interest rate	0.8	%		0.4	%		0.4	%
Expected volatility	45.3	%		47.3	%		52.8	%
Dividend yield	1.7	%		1.4	%		0.6	%
Employee Stock Purchase Plans
The Company’s eligible full-time and part-time employees are able to contribute up to 15% of their base compensation into the employee stock purchase plans, subject to an annual limit of $25,000 per person. Employees are able to purchase Company common stock at a 15% discount to the lower of the fair market value of the Company’s common stock on the initial or final trading dates of each six-month offering period. Offering periods begin on January 1 and July 1 of each year. The Company uses the Black-Scholes option pricing model to determine the fair value of employee stock purchase plan share-based payments. The fair value of the six-month “look-back” option in the Company’s employee stock purchase plans is estimated by adding the fair value of 0.15 of one share of stock to the fair value of 0.85 of an option on one share of stock. The Company utilized U.S. Treasury yields as of the grant date for its risk-free interest rate assumption, matching the Treasury yield terms to the six-month offering period. The Company utilized historical company data to develop its dividend yield and expected volatility assumptions.
Shares purchased under the plans were 0.5 million for each of the years ended December 31, 2014 and 2013, and 0.3 million for the year ended December 31, 2012.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2014
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive (Loss) Income
	The following table sets forth the after-tax components of comprehensive (loss) income:


		Foreign				Net				Prior Service			Cash Flow			Available-For-Sale Securities			Total
		Currency				Actuarial Loss				Cost Associated			Hedges						Accumulated
		Translation				Associated with				with									Other
		Adjustment				Postretirement				Postretirement									Comprehensive
						Plans and				Plans									(Loss) Income
						Workers’
						Compensation
						Obligations
		(Dollars in millions)
	December 31, 2011	$	3.1			$	(464.9	)		$	(9.6	)	$	335.7		$	(6.7	)	$	(142.4	)

	Net change in fair value	—				—				—			350.4			(15.5		)	334.9

	Reclassification from other comprehensive income to earnings	—				53.2				2.2			(298.6		)	22.5			(220.7		)

	Current period change	19.1				—				20.1			—			—			39.2

	December 31, 2012	22.2				(411.7		)		12.7			387.5			0.3			11

	Net change in fair value	—				—				—			(333.6		)	(12.3		)	(345.9		)

	Reclassification from other comprehensive income to earnings	—				95				0.7			(209.6		)	12.8			(101.1		)

	Current period change	(92.7		)		110.9				(1.4		)	—			—			16.8

	December 31, 2013	(70.5		)		(205.8		)		12			(155.7		)	0.8			(419.2		)

	Net change in fair value	—				—				—			(195.0		)	(3.7		)	(198.7		)

	Reclassification from other comprehensive income to earnings	—				31				1.7			(10.2		)	2.9			25.4

	Current period change	(41.0		)		(142.7		)		11.4			—			—			(172.3		)

	December 31, 2014	$	(111.5	)		$	(317.5	)		$	25.1		$	(360.9	)	$	—		$	(764.8	)

	The following table provides additional information regarding items reclassified out of "Accumulated other comprehensive (loss) income" into earnings during the year ended December 31, 2014:


			Year Ended December 31, 2014				Year Ended December 31, 2013
	Details about accumulated other comprehensive (loss) income components		Amount reclassified from accumulated other comprehensive (loss) income (1)				Amount reclassified from accumulated other comprehensive (loss) income (1)				Affected line item in the consolidated statement of operations
			(Dollars in millions)				(Dollars in millions)
	Net actuarial loss associated with postretirement plans and workers' compensation obligations:
	Postretirement health care and life insurance benefits		$	(14.5	)		$	(24.1	)		Operating costs and expenses
	Postretirement health care and life insurance benefits		—				(61.3		)		Settlement charges related to the Patriot bankruptcy reorganization

	Defined benefit pension plans		(24.8		)		(54.4		)		Operating costs and expenses
	Defined benefit pension plans		(8.7		)		—				Restructuring and pension settlement charges

	Defined benefit pension plans		(5.4		)		(11.3		)		Selling and administrative expenses
	Insignificant items		4.1				(1.1		)

			(49.3		)		(152.2		)		Total before income taxes
			18.3				57.2				Income tax benefit

			$	(31.0	)		$	(95.0	)		Total after income taxes

	Prior service credit (cost) associated with postretirement plans:
	Postretirement health care and life insurance benefits		$	(1.3	)		$	1.7			Operating costs and expenses

	Postretirement health care and life insurance benefits		—				(1.9		)		Settlement charges related to the Patriot bankruptcy reorganization

Defined benefit pension plans		(1.3		)		(1.0		)		Operating costs and expenses
		(2.6		)		(1.2		)		Total before income taxes
		0.9				0.5				Income tax benefit

		$	(1.7	)		$	(0.7	)		Total after income taxes

Cash flow hedges:
Foreign currency forward contracts		$	(27.3	)		$	162.4			Operating costs and expenses

Fuel and explosives commodity swaps		(22.3		)		11.4				Operating costs and expenses

Coal trading commodity futures, swaps and options		63.9				130.6				Other revenues

Insignificant items		(0.4		)		(0.5		)
		13.9				303.9				Total before income taxes

		(3.7		)		(94.3		)		Income tax provision
		$	10.2			$	209.6			Total after income taxes


Available-for-sale securities:
Debt securities		$	—			$	0.2			Interest income

Equity securities		(4.7		)		(21.5		)		Asset impairment and mine closure costs
		(4.7		)		(21.3		)		Total before income taxes
		1.8				8.5				Income tax benefit

		$	(2.9	)		$	(12.8	)		Total after income taxes
(1) Presented as gains (losses) in the consolidated statements of operations.
Comprehensive (loss) income differs from net (loss) income by the amount of unrealized gain or loss resulting from valuation changes of the Company’s cash flow hedges (see Note 6. "Derivatives and Fair Value Measurements" and Note 7. "Coal Trading" for information related to the Company’s cash flow hedges), changes in the fair value of available-for-sale securities (see Note 5. "Investments" for information related to the Company's investments in available-for-sale securities), the change in actuarial loss and prior service cost of postretirement plans and workers' compensation obligations (see Note 15. "Postretirement Health Care and Life Insurance Benefits," Note 16. "Pension and Savings Plans" and Note 25. "Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation" for information related to the Company's postretirement and pension plans) and foreign currency translation adjustment related to the Company's investments in Middlemount, whose functional currency is the Australian dollar. The values of the Company’s cash flow hedging instruments are primarily affected by the U.S. dollar/Australian dollar exchange rate and changes in the prices of certain coal and diesel fuel products.

Resource_Management_Acquisitio

Resource Management, Acquisitions and Other Commercial Events	12 Months Ended
	Dec. 31, 2014
Resource Management, Acquisitions and Other Commercial Events [Abstract]
Resource Management, Acquisitions and Other Commercial Events	Resource Management, Acquisitions 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 year ended December 31, 2014 and will continue to realize higher prices for coal supplied pursuant to that agreement.
	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 as discussed in Note 2. "Asset Impairment and Mine Closure Costs." Accordingly, there was no gain or loss recognized on the disposal during the year ended December 31, 2014.
	In December 2014, the Company sold non-strategic coal reserves located in Kentucky in exchange for cash proceeds of $29.6 million. The Company recognized a gain on sale of $13.6 million related to the transaction, which was classified in "Net gain on disposal or exchange of assets" in the consolidated statement of operations for the year ended December 31, 2014.
	In 2013, the Company received proceeds of $70.0 million and recognized a gain of $40.3 million for a similar transaction related to non-strategic coal reserves and surface lands located in Kentucky.
	Joint Venture
	In 2014, the Company agreed to establish an unincorporated joint venture project with Glencore plc (Glencore), in which each party will hold a 50% interest, to combine the existing operations of the Company's Wambo Open-Cut Mine in Australia with the adjacent coal reserves of Glencore's United Mine. The Company expects the project to result in several operation synergies, including improved mining productivity, lower per-unit operating costs and an extended mine life. The joint venture operations are expected to commence in 2017, subject to substantive contingencies, including the requisite regulatory and permitting approvals. At such time as those contingencies have been resolved or are no longer considered to be substantive, the Company will account for its beneficial interest in the combined operations at fair value.
	Acquisition
	Included in the Company's acquisition of PEA-PCI was a receivable from MCG Coal Holdings Pty Ltd (MCGH) that was initially measured based on the amount PEA-PCI loaned to MCGH. PEA-PCI had previously agreed to convert its receivable for a 90% equity interest in MCGH. The transaction was initially expected to be completed in May 2011. However, non-performance by a third party to the transaction resulted in PEA-PCI commencing litigation. The original loan balance was classified as a receivable pending the outcome of the legal proceedings. The loan receivable was subsequently adjusted downward during the measurement period based on the completion of a third-party valuation appraisal on the underlying net assets of MCGH, which were substantially comprised of mineral rights. In January 2012, the court ruled that the outstanding loan balance be converted to a 90% equity interest in MCGH, resulting in consolidation of MCGH and recognition of noncontrolling interests of $39.0 million at conversion. In June 2012, the Company acquired the remaining noncontrolling interests in MCGH for total consideration of $49.8 million. This acquisition was accounted for as an equity transaction as the Company previously maintained control of MCGH. Accordingly, the Company recorded a decrease to additional paid-in capital of $10.8 million related to this transaction, representing the difference between the consideration paid and the carrying value. As described in the foregoing "Divestitures" section, the Company completed the sale of the related exploration tenement in January 2014.

Earnings_per_Share

Earnings per Share	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Earnings per Share	Earnings per Share (EPS)
	Basic and diluted EPS are computed using the two-class method, which is an earnings allocation that determines EPS for each class of common stock and participating securities according to dividends declared and participation rights in undistributed earnings. The Company’s restricted stock awards are considered participating securities because holders are entitled to receive non-forfeitable dividends during the vesting term. Diluted EPS includes securities that could potentially dilute basic EPS during a reporting period, for which the Company includes the Debentures and share-based compensation awards. Dilutive securities are not included in the computation of loss per share when a company reports a net loss from continuing operations as the impact would be anti-dilutive.
	For all but the performance units, the potentially dilutive impact of the Company’s share-based compensation awards is determined using the treasury stock method. Under the treasury stock method, awards are treated as if they had been exercised with any proceeds used to repurchase common stock at the average market price during the period. Any incremental difference between the assumed number of shares issued and purchased is included in the diluted share computation. For the Company’s performance units, their contingent features result in an assessment for any potentially dilutive common stock by using the end of the reporting period as if it were the end of the contingency period for all units granted. For further discussion of the Company’s share-based compensation awards, see Note 18. "Share-Based Compensation."
	A conversion of the Debentures may result in payment for any conversion value in excess of the principal amount of the Debentures in the Company’s common stock. For diluted EPS purposes, potential common stock is calculated based on whether the market price of the Company’s common stock at the end of each reporting period is in excess of the conversion price of the Debentures. For a full discussion of the conditions under which the Debentures may be converted, the conversion rate to common stock and the conversion price, see Note 12. "Long-term Debt." The effect of the Debentures was excluded from the calculation of diluted EPS for all periods presented herein because to do so would have been anti-dilutive for those periods.
	The computation of diluted EPS also excluded aggregate share-based compensation awards of approximately 3.2 million, 2.3 million and 1.2 million for the years ended December 31, 2014, 2013 and 2012, respectively, because to do so would have been anti-dilutive for those periods. Because the potential dilutive impact of such share-based compensation awards is calculated under the treasury stock method, anti-dilution generally occurs when the exercise prices or unrecognized compensation cost per share of such awards are higher than the Company’s average stock price during the applicable period.
	The following illustrates the earnings allocation method utilized in the calculation of basic and diluted EPS:


		Year Ended December 31,
		2014			2013			2012
		(In millions, except per share amounts)
	EPS numerator:

	Loss from continuing operations, net of income taxes	$	(749.1	)	$	(286.0	)	$	(470.9	)
	Less: Net income attributable to noncontrolling interests	9.7			12.3			10.6

	Loss from continuing operations attributable to common stockholders, before allocation of earnings to participating securities	(758.8		)	(298.3		)	(481.5		)
	Less: Earnings allocated to participating securities	1			0.8			0.7

	Loss from continuing operations attributable to common	(759.8		)	(299.1		)	(482.2		)
	stockholders, after allocation of earnings to participating securities
	Loss from discontinued operations attributable to common stockholders, after allocation of earnings to participating securities	(28.2		)	(226.6		)	(104.2		)
	Net loss attributable to common stockholders, after earnings	$	(788.0	)	$	(525.7	)	$	(586.4	)
	allocated to participating securities
	EPS denominator:

	Weighted average shares outstanding — basic and diluted	268.1			267.1			268

	Basic and diluted EPS attributable to common stockholders:

	Loss from continuing operations	$	(2.83	)	$	(1.12	)	$	(1.80	)
	Loss from discontinued operations	(0.11		)	(0.85		)	(0.39		)
	Net loss attributable to common stockholders	$	(2.94	)	$	(1.97	)	$	(2.19	)

Management_Labor_Relations

Management - Labor Relations	12 Months Ended
Management - Labor Relations	Dec. 31, 2014
Risk Management Labor Relations [Abstract]
Management - Labor Relations	Management — Labor Relations
	On December 31, 2014, the Company had approximately 8,300 employees worldwide, excluding those employees that were employed at operations classified as discontinued operations and including approximately 6,000 hourly employees. Approximately 39% of those hourly employees were represented by organized labor unions and were employed by mines that generated 20% of the Company's 2014 coal production from continuing operations. In the U.S., one surface mine is represented by an organized labor union. In Australia, the coal mining industry is unionized and the majority of hourly workers employed at the Company’s Australian Mining operations are members of trade unions. The Construction Forestry Mining and Energy Union generally represents the Company’s Australian subsidiaries’ hourly production and engineering employees, including those employed through contract mining relationships. The Company believes labor relations with its employees are good. Should that condition change, the Company could experience labor disputes, work stoppages or other disruptions in production that could negatively impact the Company’s results of operations and cash flows.
	The following table presents the Company's active mining operations as of December 31, 2014 in which the employees are represented by organized labor unions:


	Mine		Current Agreement Expiration Date

	U. S.
	Kayenta (1)		Sep-19

	Australia
	Owner-operated mines:
	Wambo Open-Cut (2)(3)		Aug-14
	North Wambo Underground (2)(3)		Apr-15
	North Goonyella (3)		May-15
	Metropolitan (3)		Aug-15
	Millennium (3)		Oct-15
	Wilpinjong		May-16
	Coppabella (4)		Oct-16
	Moorvale (4)		Jun-17

	Contractor-operated mines:
	Burton		Dec-16

	-1	Hourly workers at the Company’s Kayenta Mine in Arizona are represented by the UMWA under the Western Surface Agreement, which is effective through September 16, 2019. This agreement covers approximately 9% of the Company’s U.S. subsidiaries’ hourly employees, who generated approximately 4% of the Company’s U.S. production during the year ended December 31, 2014.

	-2	Employees of the Company's Wambo Coal Handling and Preparation Plant facility also operate under a separate enterprise agreement. That agreement expired in October 2014 and negotiations are underway. There have been no disruptions to the operations of the plant as a result of the expiration of the agreement.

	(3)	Negotiations for the Wambo Open-Cut, North Wambo Underground, North Goonyella, Metropolitan and Millennium mines are all underway or have been scheduled and the mines continue to operate. Hourly employees of these mines comprise approximately 56% of the Company's Australian subsidiaries hourly employees, who generated approximately 42% of the Company's Australian production during the year ended December 31, 2014.

	(4)	Employees of the Company's Coppabella/Moorvale Coal Handling and Preparation Plant facility also operate under a separate enterprise agreement. That agreement expired in March 2014 and negotiations are underway. There have been no disruptions to the operations of the plant as a result of the expiration of the agreement.

Financial_Instrumentsand_Guara

Financial Instrumentsand Guarantees with Off-Balance-Sheet Risk(Notes)	12 Months Ended
	Dec. 31, 2014
Financial Instruments And Guarantees With Off Balance Sheet Risk Disclosure [Abstract]
Financial Instruments and Guarantees with Off-Balance-Sheet Risk	Financial Instruments, Guarantees With Off-Balance-Sheet Risk and Other Guarantees
	In the normal course of business, the Company is a party to guarantees and financial instruments with off-balance-sheet risk, which are not reflected in the accompanying consolidated balance sheets. Such financial instruments are valued based on the amount of exposure under the instrument and the likelihood of required performance. In the Company’s past experience, virtually no claims have been made against these financial instruments. As of February 25, 2015, management does not expect any material losses to result from these guarantees or off-balance-sheet instruments in excess of liabilities provided for in the consolidated balance sheet as of December 31, 2014.
	Financial Instruments with Off-Balance Sheet Risk
	As of December 31, 2014, the Company had the following financial instruments with off-balance-sheet risk:


		Reclamation		Coal Lease		Workers’		Other(1)		Total
		Obligations		Obligations		Compensation
						Obligations
		(Dollars in millions)
	Self bonding	$	1,361.40	$	—	$	—	$	—	$	1,361.40

	Surety bonds	325.2		103.8		92.3		11.4		532.7

	Bank guarantees	319.8		—		—		117.4		437.2

	Letters of credit	17.6		—		34.1		100.9		152.6

		$	2,024.00	$	103.8	$	126.4	$	229.7	$	2,483.90


	(1)	Other includes the $79.7 million in letters of credit related to Dominion Terminal Associates and the PBGC, as described below, and an additional $150.0 million in bank guarantees, letters of credit and surety bonds related to road maintenance, performance guarantees and other operations.
	The Company owns a 37.5% interest in Dominion Terminal Associates, a partnership that operates a coal export terminal in Newport News, Virginia under a 30-year lease that permits the partnership to purchase the terminal at the end of the lease term for a nominal amount. The partners have severally (but not jointly) agreed to make payments under various agreements which in the aggregate provide the partnership with sufficient funds to pay rents and to cover the principal and interest payments on the floating-rate industrial revenue bonds issued by the Peninsula Ports Authority, and which are supported by letters of credit from a commercial bank. As of December 31, 2014, the Company’s maximum reimbursement obligation to the commercial bank was in turn supported by four letters of credit totaling $42.7 million.
	The Company is party to an agreement with the PBGC and TXU Europe Limited, an affiliate of the Company’s former parent corporation, under which the Company is required to make special contributions to two of the Company’s defined benefit pension plans and to maintain a $37.0 million letter of credit in favor of the PBGC. If the Company or the PBGC gives notice of an intent to terminate one or more of the covered pension plans in which liabilities are not fully funded, or if the Company fails to maintain the letter of credit, the PBGC may draw down on the letter of credit and use the proceeds to satisfy liabilities under the Employee Retirement Income Security Act of 1974, as amended. The PBGC, however, is required to first apply amounts received from a $110.0 million guarantee in place from TXU Europe Limited in favor of the PBGC before it draws on the Company’s letter of credit. On November 19, 2002, TXU Europe Limited was placed under the administration process in the U.K. (a process similar to bankruptcy proceedings in the U.S.) and continues under this process as of December 31, 2014. As a result of these proceedings, TXU Europe Limited may be liquidated or otherwise reorganized in such a way as to relieve it of its obligations under its guarantee.
	As of December 31, 2014, the Company's wholly-owned captive insurance subsidiary was party to a letter of credit arrangement for $22.7 million in relation to certain of its workers' compensation and other insurance-related obligations whereby that subsidiary has pledged $32.6 million of its investments in debt securities as collateral. This arrangement reduces the letters of credit drawn on the Company's 2013 Credit Facility and effectively lowers the fees associated with the related letters of credit.
	Patriot Bankruptcy Reorganization
	Refer to Note 25. "Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation" for a discussion of certain credit support provided to Patriot as part of the settlement agreement related to its emergence from bankruptcy, which support included $81.4 million of surety bonds and $22.4 million of letters of credit included in the table above, in addition to $18.4 million of corporate guarantees to Patriot beneficiaries as of December 31, 2014.
	Accounts Receivable Securitization
	The Company has an accounts receivable securitization program (securitization program) with a maximum capacity of $275.0 million through its wholly-owned, bankruptcy-remote subsidiary (Seller). At December 31, 2014, the Company had $204.0 million remaining capacity available under the securitization program, net of outstanding letters of credit and amounts drawn. Under the securitization program, the Company contributes trade receivables of most of the Company’s U.S. subsidiaries on a revolving basis to the Seller, which then sells the receivables in their entirety to a consortium of unaffiliated asset-backed commercial paper conduits and banks (the Conduits). After the sale, the Company, as servicer of the assets, collects the receivables on behalf of the Conduits for a nominal servicing fee. The Company utilizes proceeds from the sale of its accounts receivable as an alternative to short-term borrowings under the 2013 Revolver portion of the Company's 2013 Credit Facility, effectively managing its overall borrowing costs and providing an additional source for working capital. The securitization program will expire in April 2016.
	The Seller is a separate legal entity whose assets are available first and foremost to satisfy the claims of its creditors. Of the receivables sold to the Conduits, a portion of the amount due to the Seller is deferred until the ultimate collection of the underlying receivables. During the year ended December 31, 2014, the Company received total consideration of $4,257.2 million related to accounts receivable sold under the securitization program, including $2,775.5 million of cash up front from the sale of the receivables, an additional $1,272.3 million of cash upon the collection of the underlying receivables and $209.4 million that had not been collected at December 31, 2014 and was recorded at carrying value, which approximates fair value. The reduction in accounts receivable as a result of securitization activity with the Conduits was $30.0 million and $100.0 million at December 31, 2014 and 2013, respectively.
	The securitization activity has been reflected in the consolidated statements of cash flows as an operating activity because both the cash received from the Conduits upon sale of receivables as well as the cash received from the Conduits upon the ultimate collection of receivables are not subject to significantly different risks given the short-term nature of the Company’s trade receivables. The Company recorded expense associated with securitization transactions of $1.5 million, $1.5 million and $2.0 million for the years ended December 31, 2014, 2013 and 2012, respectively.
	Other
	Included in "Other noncurrent liabilities" in the Company's consolidated balance sheets as of December 31, 2014 and 2013 is a liability of $44.7 million and $45.6 million, respectively, related to reclamation, bonding commitments and worker's compensation provided on behalf of a third-party coal producer associated with a 2007 purchase of coal reserves and surface lands in the Illinois Basin.
	The Company is the lessee under numerous equipment and property leases. It is common in such commercial lease transactions for the Company, as the lessee, to agree to indemnify the lessor for the value of the property or equipment leased, should the property be damaged or lost during the course of the Company’s operations. The Company expects that losses with respect to leased property, if any, would be covered by insurance (subject to deductibles). The Company and certain of its subsidiaries have guaranteed other subsidiaries’ performance under various lease obligations. Aside from indemnification of the lessor for the value of the property leased, the Company’s maximum potential obligations under its leases are equal to the respective future minimum lease payments, and the Company assumes that no amounts could be recovered from third parties.
	The Company has provided financial guarantees under certain long-term debt agreements entered into by its subsidiaries and substantially all of the Company’s U.S. subsidiaries provide financial guarantees under long-term debt agreements entered into by the Company. The maximum amounts payable under the Company’s debt agreements are equal to the respective principal and interest payments.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies
	Commitments
	Unconditional Purchase Obligations
	As of December 31, 2014, purchase commitments for capital expenditures were $42.7 million, all of which is obligated within the next year. In Australia, the Company has generally secured the ability to transport coal through rail contracts and ownership interests in three east coast coal export terminals that are primarily funded through take-or-pay arrangements with terms ranging up to 25 years. In the U.S., the Company has entered into certain long-term coal export terminal agreements to secure export capacity through the Gulf Coast. As of December 31, 2014, these Australian and U.S. commitments under take-or-pay arrangements totaled $2,827.2 million, of which $329.5 million is obligated within the next year.
	Federal Coal Leases
	In the second quarter of 2012, the Company was named by the U.S. Department of the Interior, Bureau of Land Management (BLM) as the winning bidder for control of approximately 1.1 billion tons of federal coal reserves adjacent to its North Antelope Rochelle Mine in the Southern Powder River Basin of Wyoming, with a weighted average bid price of approximately $1.10 per mineable ton. Consequently, the Company made aggregate payments of $247.9 million during each of the years ended December 31, 2014, 2013 and 2012 pursuant to the two associated federal coal leases, with remaining annual payments of $247.9 million due in each of the next two years.
	In July 2011, the Company was named by the BLM as the winning bidder for control of approximately 220 million tons of federal coal reserves adjacent to its Caballo Mine in the Powder River Basin at a bid price of $0.95 per mineable ton, with payments of $42.1 million due annually in each of the years from 2011 through 2015 pursuant to the associated federal coal lease (the Belle Ayr North Lease). Similarly, in September 2011, a subsidiary of Alpha Natural Resources, Inc. (Alpha) was named by the BLM as the winning bidder for control of approximately 130 million tons of federal coal reserves in the Powder River Basin at a bid price of $1.10 per mineable ton, with contractual payments of $28.6 million due annually in each of the years from 2011 through 2015 under the associated federal coal lease (the Caballo West Lease). In July 2012, the Company and Alpha executed a lease exchange agreement with the BLM whereby the Company agreed to sell, assign and transfer its interest in the Belle Ayr North Lease in exchange for (1) Alpha's interest in the Caballo West Lease, (2) reimbursement of $13.5 million for the difference in the related federal coal lease payments made by each party in 2011 and (3) five annual true up payments of $3.9 million for the excess of the $1.10 bid price per mineable ton assumed under the Caballo West Lease over the $0.95 price under the transferred lease. An aggregate of $21.3 million was received from Alpha during the year ended December 31, 2012 for the reimbursement payment and first and second true up payments. The third and fourth true-up payments were received in 2013 and 2014, respectively. The one remaining true up payment is due from Alpha on November 1, 2015. Those cash receipts are classified in "Proceeds from disposal of assets, net of notes receivable" in the consolidated statement of cash flows.
	The federal coal leases executed with the BLM described above expire after a 20-year initial term, unless at such time there is ongoing production on the subject leases or within an active logical mining unit of which they are part.
	Contingencies
	From time to time, the Company or its subsidiaries are involved in legal proceedings arising in the ordinary course of business or related to indemnities or historical operations. The Company believes it has recorded adequate reserves for these liabilities and that there is no individual case pending that is likely to have a material adverse effect on the Company’s financial condition, results of operations or cash flows. The Company discusses its significant legal proceedings below, including ongoing proceedings and those that impacted the Company's results of operations for the periods presented.
	Litigation Relating to Continuing Operations
	Monto Coal Pty Limited, Monto Coal 2 Pty Ltd Limited and Macarthur Coal Limited. In October 2007, a statement of claim was delivered to Monto Coal Pty Ltd, a wholly-owned subsidiary of PEA-PCI, then Macarthur Coal Limited, and Monto Coal 2 Pty Ltd, an equity accounted investee, from the minority interest holders in the Monto Coal Joint Venture, alleging that Monto Coal 2 Pty Ltd breached the Monto Coal Joint Venture Agreement and Monto Coal Pty Ltd breached the Monto Coal Management Agreement. Monto Coal Pty Ltd is the manager of the Monto Coal Joint Venture pursuant to the Management Agreement. Monto Coal 2 Pty Ltd holds a 51% interest in the Monto Coal Joint Venture. The plaintiffs are Sanrus Pty Ltd, Edge Developments Pty Ltd and H&J Enterprises (Qld) Pty Ltd. An additional statement of claim was delivered to PEA-PCI in November 2010 from the same minority interest holders in the Monto Coal Joint Venture, alleging that PEA-PCI induced Monto Coal 2 Pty Ltd and Monto Coal Pty Ltd to breach the Monto Coal Joint Venture Agreement and the Monto Coal Management Agreement, respectively. These actions, which are pending before the Supreme Court of Queensland, Australia, seek damages from the three defendants collectively of $1,193.2 million Australian dollars, plus interest and costs. The defendants dispute the claims and are vigorously defending their positions. Based on the Company's evaluation of the issues and their potential impact, the amount of any future loss cannot be reasonably estimated. However, based on current information, the Company believes these claims are likely to be finalized without a material adverse effect on its financial condition, results of operations or cash flows.
	Sumiseki Materials Co. Ltd. In 2010, Sumiseki Materials Co. Ltd. (Sumiseki), the Class B shareholder (noncontrolling interest holder) in Wambo Coal Pty Ltd (Wambo), an Australian subsidiary of the Company, filed a lawsuit against Wambo in the Supreme Court of New South Wales, Australia, alleging that it was entitled to certain dividends from Wambo (subject to limited exceptions) and requested payment of those dividends for periods from 2009 to 2012. In March 2013, the Supreme Court ruled Sumiseki was entitled to the disputed dividends (subject to limited exceptions). In May 2013, the Supreme Court issued finalized orders, which included the amounts due for the disputed dividends including interest. Wambo appealed the Supreme Court's decision to the New South Wales Court of Appeal and obtained a stay of the Supreme Court judgment. In accordance with the terms of the stay, Wambo posted security with the court in an interest-bearing trust account jointly operated by the parties.
	On September 17, 2014, the Court of Appeal upheld the Supreme Court's ruling (with a minor exception), finding Sumiseki is entitled to the disputed dividends plus interest and costs. In its ruling, the Court of Appeal noted that while payment of dividends is usually a matter for a company's directors, the Class B dividend is a mandatory dividend, regardless of any decision by the directors, and that the amount of the dividend is based on a percentage of the company's net profit, unless there is a legal prohibition that precludes the dividend being paid. Wambo has filed an application for leave to appeal the ruling to the High Court of Australia. It is expected the application for leave to appeal to the High Court will be heard in the first quarter of 2015.
	Based on the results of the Court of Appeals proceedings, the Company reclassified the security posted with the court and the amount of dividends payable from "Cash and cash equivalents" and "Noncontrolling interests," respectively, as presented in the consolidated balance sheet as of December 31, 2013, to "Other current assets" and "Accounts payable and accrued expenses," respectively, in the consolidated balance sheet as of December 31, 2014. Amounts recorded included an aggregate liability of $50.1 million related to the dividends payable and related accrued interest in "Accounts payable and accrued expenses" in the consolidated balance sheet as of December 31, 2014. The Company reflected the portion of the reclassified security posted with the court related to dividends within the "Cash Flows From Financing Activities" section of the consolidated statement of cash flows for the year ended December 31, 2014.
	Eagle Mining, LLC Arbitration. On May 3, 2013, Eagle Mining, LLC (Eagle) filed an arbitration demand against a Company subsidiary under a contract mining agreement, asserting various claims for damages. An arbitration hearing was held in January 2014 before a single arbitrator. On March 18, 2014, the arbitrator awarded Eagle damages on some of its claims in the total amount of $23.4 million. In December 2013, prior to the arbitration hearing, the Company subsidiary established a reserve in the amount of $7.8 million, which amount represented the low end of the Company's previous estimated range of loss associated with the matter. The difference between the Company’s reserve amount and the amount of the award was primarily due to damages that were awarded on one of the claims at the high end of the Company’s previous estimated range of loss, and that were awarded on another claim for which the Company initially determined the probability of loss to be remote. As a result of the damages awarded to Eagle in arbitration, the Company recorded an additional charge of $15.6 million in "Operating costs and expenses" in the consolidated statement of operations for the year ended December 31, 2014. On April 18, 2014, the Company subsidiary filed a petition to partially vacate and modify the arbitration award in the United States District Court for the Southern District of West Virginia, Charleston Division.
	Contract Pricing Arbitration. In December 2014, the Company resolved an arbitration process with one of its U.S. customers related to the negotiated price of coal delivered pursuant to a long-term coal supply agreement. During the year ended December 31, 2014, the Company shipped 4.8 million tons subject to that agreement. In connection with the settlement, the Company agreed to provide the customer with a pricing rebate of $68.7 million, which represents a portion of the total amount that was invoiced and collected upon in 2014 based on contract prices in effect in 2013. The Company decreased revenue recognized for the year ended December 31, 2014 by the rebate amount and recorded a corresponding liability, which will be ratably relieved through credits against future customer billings through 2017.
	Queensland Bulk Handling Pty Ltd. On June 30, 2014, Queensland Bulk Handling Pty Ltd (QBH) filed a statement of claim with the Supreme Court of Queensland, Australia, against Peabody (Wilkie Creek) Pty Limited, an indirect wholly-owned subsidiary of the Company, alleging breach of a Coal Port Services Agreement between the parties. QBH originally sought damages of $113.1 million Australian dollars, plus interest and costs. QBH, however, later altered its claim and is no longer seeking a specific monetary award, but rather a declaration that the Company subsidiary had exercised an option to renew the contract for a further term. The Company believes that its subsidiary has strong legal defenses to this claim, and will defend its interests vigorously in this proceeding. The Company further believes this claim is likely to be resolved without a material adverse effect on its financial condition, results of operations or cash flows.
	Gulf Power Company. On June 22, 2006, Gulf Power Company (Gulf Power) filed a breach of contract lawsuit against a Company subsidiary in the U.S. District Court, Northern District of Florida, contesting the force majeure declaration by the Company's subsidiary under a coal supply agreement with Gulf Power and seeking damages for alleged past and future tonnage shortfalls of nearly five million tons under the agreement, which expired in 2007. After the proceedings, the District Court awarded Gulf Power damages of $20.6 million for its 2007 cover coal purchases and prejudgment interest of $6.9 million plus post-judgment interest. The Company's subsidiary and Gulf Power both appealed and, in June 2013, the U.S. Court of Appeals for the Eleventh Circuit issued its order affirming the District Court's judgment in all respects. The Company subsidiary and Gulf Power agreed not to seek judicial review of the Eleventh Circuit's order, and the Company subsidiary paid the judgment during the third quarter of 2013. In connection with the order, the Company recorded a charge for the judgment amount of $20.6 million in "Operating costs and expenses" and $6.9 million in "Interest expense" in the consolidated statements of operations for the year ended December 31, 2013.
	Environmental Claims and Litigation
	Claims Arising From Historical, Non-Coal Producing Operations. Gold Fields Mining, LLC (Gold Fields) is a dormant, non-coal producing entity that was previously managed and owned by Hanson plc, the Company's predecessor owner. In a February 1997 spin-off, Hanson plc transferred ownership of Gold Fields to the Company despite the fact that Gold Fields had no ongoing operations and the Company had no prior involvement in its past operations. Gold Fields is currently one of the Company's subsidiaries. The Company indemnified TXU Group with respect to certain claims relating to the historical operations of a former affiliate of Gold Fields.
	Environmental claims for remediation, past costs, future costs, and/or natural resource damages have been asserted against Gold Fields related to historical activities of Gold Fields or a former affiliate. Gold Fields or the former affiliate has been named a potentially responsible party (PRP) at five national priority list sites based on the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA). CERCLA claims were asserted at 13 additional sites, bringing the total to 18, which have since been reduced to 8 by completion of work, transfer or regulatory inactivity. The number of CERCLA sites alone is not a relevant measure of liability because the nature and extent of environmental concerns and costs varies by site, as does the estimated share of responsibility relative to other PRPs for Gold Fields or the former affiliate.
	Undiscounted liabilities for environmental cleanup-related costs for all of the sites noted above were $69.4 million as of December 31, 2014 and $63.8 million as of December 31, 2013, $19.4 million and $18.3 million of which was reflected as a current liability, respectively, in the consolidated balance sheets as of those dates. These amounts represent those costs that the Company believes are probable and reasonably estimable.
	Significant uncertainty exists as to whether claims will be pursued against Gold Fields or the former affiliate in all cases, and where they are pursued, the amount and timing of the eventual costs and liabilities, which could be greater or less than the liabilities recorded in the consolidated balance sheets. Changes to cost estimates associated with a particular site can occur for many reasons, including, but not limited to, the gathering of additional information at the site, the completion of the remedial design phase of the CERCLA remediation process, changes in anticipated remediation standards or labor and material costs or the reaching of a settlement agreement or consent order by the parties at the site. Based on the Company's evaluation of the issues and their potential impact, the total amount of any future loss cannot be reasonably estimated. However, based on current information, the Company believes these claims are likely to be resolved without a material adverse effect on its financial condition, results of operations or cash flows.
	Other
	In June 2007, the New York Office of the Attorney General (NYAG) served a letter and subpoena on the Company, seeking information and documents relating to the Company's disclosure to investors of risks associated with possible climate change and related legislation and regulations. The Company believes it has made full and proper disclosure of these potential risks. In late 2013, the NYAG submitted a letter to the Company requesting additional information and documents and the Company is in the process of complying with that request.
	In January 2013, the Securities and Exchange Commission (SEC) staff served a subpoena on the Company seeking information and documents relating to the development of Prairie State Energy Campus, a 1,600 megawatt coal-fueled electricity generation plant and adjacent coal mine in Illinois in which the Company owns a 5.06% undivided interest. The Company cooperated with the SEC's investigation and has not received any related communication from the SEC since August 2013.
	At times the Company becomes a party to other disputes, including those related to contract miner performance, claims, lawsuits, arbitration proceedings and administrative procedures in the ordinary course of business in the U.S., Australia and other countries where the Company does business. Based on current information, the Company believes that such other pending or threatened proceedings are likely to be resolved without a material adverse effect on its financial condition, results of operations or cash flows.

Matters_Related_to_the_Bankrup

Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation (Patriot) (Notes)	12 Months Ended
	Dec. 31, 2014
Matters Related to the Bankruptcy of Patriot Coal Corporation [Abstract]
Matters Related to the Bankruptcy of Patriot Coal Corporation [Text Block]	Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation
	Claims and Litigation
	On October 31, 2007, the Company spun-off companies that constituted portions of its former Eastern U.S. Mining operations business segment to form Patriot. The spin-off included eight company-operated mines, two majority-owned joint venture mines and numerous contractor-operated mines serviced by eight coal preparation facilities, along with 1.2 billion tons of proven and probable coal reserves. On July 9, 2012, Patriot and certain of its wholly-owned subsidiaries filed voluntary petitions for reorganization under Chapter 11 of the U.S. Code in the U.S. Bankruptcy Court for the Southern District of New York. The case was subsequently moved to the U.S. Bankruptcy Court for the Eastern District of Missouri.
	On March 14, 2013, Patriot filed a motion in its bankruptcy proceeding seeking authority to reject its collective bargaining agreements under section 1113 of the Bankruptcy Code and change its obligation to pay benefits it provided to certain of its retirees pursuant to section 1114 of the Bankruptcy Code and transferring the obligation to a Voluntary Employee Benefit Association (VEBA). At the same time, Patriot also filed a declaratory judgment complaint against the Company and one of its subsidiaries seeking a declaration that Section 1(d) of the NBCWA Individual Employer Plan Liabilities Assumption Agreement dated October 22, 2007 (NBCWA Agreement) would not apply to reduce the subsidiary's healthcare benefits funding obligations if Patriot were to be successful under the bankruptcy code in changing the benefits it is required to pay to certain of its retirees under its labor agreements. On April 5, 2013, Patriot filed a motion for summary judgment with respect to the declaratory judgment complaint. After hearing both motions, the Court granted Patriot's section 1113/1114 motion and, on its own accord, granted the Company summary judgment on the declaratory judgment complaint. After the United Mine Workers of America (UMWA) appealed the Court's ruling on the section 1113/1114 motion, Patriot and the UMWA entered into new labor agreements pursuant to which the UMWA agreed to dismiss its appeal upon satisfaction of certain conditions. Patriot appealed the Court's grant of the summary judgment motion in the Company's and its subsidiary's favor, which an appellate court reversed. The Company and its subsidiary appealed the reversal to the United States Court of Appeals for the Eighth Circuit and filed a counterclaim in the declaratory judgment action against Patriot and the UMWA seeking a declaration that the subsidiary's healthcare benefits funding obligation would reduce to zero when one of Patriot's subsidiary's obligation to pay for retiree healthcare benefits reduced to zero under the terms of the new labor agreements. Patriot and the Official Committee of Unsecured Creditors of Patriot Coal Corporation issued discovery requests to the Company pursuant to Rule 2004 of the Federal Rules of Bankruptcy Procedure. In connection with the settlement discussed below, the 2004 discovery was suspended and subsequently halted permanently, and the adversary proceeding and related appeal in the Patriot bankruptcy case were voluntarily dismissed with prejudice.
	On October 4, 2013, the Company reached a preliminary agreement with Patriot and the UMWA, on behalf of itself, its represented Patriot employees (UMWA Employees) and its represented Patriot retirees (UMWA Retirees), to resolve all issues related to Patriot’s bankruptcy. On October 25, 2013, the parties entered into a definitive settlement agreement. On November 7, 2013, the bankruptcy court approved that agreement. On December 17, 2013, the bankruptcy court confirmed Patriot's plan of reorganization, and on December 18, 2013, Patriot closed on its exit financing and notified the bankruptcy court that the plan of reorganization had become effective. Upon Patriot's plan of reorganization becoming effective, the Company's settlement agreement with Patriot and the UMWA, on behalf of itself, the UMWA Employees and the UMWA Retirees, also became effective.
	Under the terms of the settlement agreement, the Company is required to provide total payments of $310.0 million to partially fund the newly established VEBA and settle all Patriot and UMWA claims involving the Patriot bankruptcy. Those payments included an initial payment of $90.0 million made in January 2014, comprised of $70.0 million paid to Patriot and $20.0 million paid to the VEBA, and subsequent payments to be paid to the VEBA of 75.0 million in 2015, $75.0 million in 2016 and $70.0 million in 2017. The Company’s and its subsidiary's obligations under the NBCWA Agreement have been deemed satisfied, and that agreement was terminated on December 18, 2013, the effective date of the settlement. Upon settlement, the Company had $260.7 million recorded in accumulated postretirement healthcare benefit obligations to Patriot on account of certain Patriot retirees under the NBCWA Agreement, with $63.2 million of actuarial losses and prior service costs related to the NBCWA Agreement obligations included in "Accumulated other comprehensive loss."
	As part of the settlement agreement, the Company provided $141.5 million of credit support to Patriot at the time the agreement became effective, of which $122.2 million remained outstanding as of December 31, 2014. At that date, $81.4 million of this credit support took the form of surety bonds issued for the benefit of Patriot beneficiaries, $22.4 million of this credit support took the form of letters of credit issued for the benefit of Patriot beneficiaries and $18.4 million of this credit support took the form of corporate guarantees to Patriot beneficiaries. A total of $50.7 million of the credit support (all in the form of surety bonds) relates to Patriot’s Coal Act obligations that the Company agreed to fund at the time of the Patriot spin-off pursuant to the Coal Act Liabilities Assumption Agreement and to Patriot’s Federal Black Lung obligations. Approximately $85.0 million of the total credit support ends in 2018. Upon settlement, the Company recorded a liability of $28.0 million related to the credit support, which was measured using unobservable Level 3 inputs under the fair value hierarchy to determine the cost to acquire such support. In spite of the subsequent reduction in credit support outstanding, the Company increased its recorded liability to $57.6 million as of December 31, 2014 due to a credit downgrade of Patriot issued by one of the major credit rating agencies in the fourth quarter of 2014.
	Per the terms of the settlement agreement, the Company also provided an extension of a coal terminaling agreement through March 2016 at a reduced price equal to the Company's estimated cost of providing the terminaling capacity.
	As of December 18, 2013, the effective date of the settlement, Patriot assumed (1) the agreements executed in connection with the Patriot spin-off, including Patriot’s indemnification obligations contained therein (subject to certain specified exceptions) and (2) all other agreements entered into by Patriot and the Company prior to the bankruptcy filing and not previously assumed, rejected, terminated or expired.
	In connection with the settlement agreement, effective as of December 18, 2013, Patriot, the UMWA, the UMWA Employees and the UMWA Retirees released the Company and its subsidiaries and affiliates and their current and former professionals, employees, advisors, officers, directors, insurers and agents (Peabody Released Parties) from all Causes of Action (as defined in the settlement agreement). In addition, Patriot included the Peabody Released Parties in the third-party release, exculpation and injunction provisions contained in the Patriot plan of reorganization to the extent permitted by law, and the UMWA did not object to any such releases.
	At the time the settlement became effective, the Company recognized settlement charges totaling $128.6 million allocated between: (1) a charge of $30.6 million related to settlement of the accumulated postretirement healthcare benefit obligations of certain Patriot retirees under the NBCWA Agreement and (2) a charge to discontinued operations of $98.0 million related to the settlement of other claims involving the Patriot bankruptcy. The allocation of the settlement was based on the construct of the negotiated settlement whereby Patriot was paid $70.0 million and provided with the credit support, recorded as a liability at its initial fair value of $28.0 million, and modified coal terminaling arrangement discussed above. A total of $240.0 million is to be paid to the VEBA through 2017 to settle the accumulated postretirement healthcare benefit obligations, of which $20.0 million was paid in January 2014. At December 31, 2014 and 2013, the Company's consolidated balance sheet reflected total liabilities of $271.8 million and $326.1 million, respectively, related to the settlement, representing the net present value of the payments due through 2017 to Patriot and the VEBA remaining at each date and the fair value of the liability related to the credit support provided to Patriot.
	On October 23, 2012, eight individual plaintiffs and the UMWA filed a putative class action lawsuit in the U.S. District Court for the Southern District of West Virginia against the Company, one of its subsidiaries and an unrelated coal company (Lowe et al. v. Peabody Holding Company, LLC, et al.). The lawsuit sought to have the court obligate the defendants to maintain certain Patriot benefit plans at their current levels and to find the defendants' actions in violation of the Employee Retirement Income Security Act of 1974. On January 7, 2013, the Company defendants filed a motion to dismiss the complaint for failure to state a claim upon which relief can be granted. The plaintiffs thereafter amended their complaint to include new allegations and name two more individuals as plaintiffs. The Company defendants updated their motion to dismiss to respond to the new allegations and filed it with the Court. On September 27, 2013, the Court granted the Company defendants' motion to dismiss, and plaintiffs appealed the dismissal to the United States Court of Appeals for the Fourth Circuit. On December 20, 2013, after the effective date of the settlement agreement discussed above, the parties filed a joint stipulation with the Court dismissing the appeal as to the Company defendants with prejudice.
	Off-Balance Sheet Arrangements
	Patriot has approximately $150 million in 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. At the time of the spin-off, Patriot indemnified the Company against any claim relating to these liabilities, including 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 definitive settlement agreement described above, which became effective upon Patriot's emergence from bankruptcy on December 18, 2013, included Patriot’s affirmance of the indemnity relating to such black lung liabilities.
	If Patriot does not pay the black lung liabilities in the future, the DOL would first look to Patriot and any related credit support for payment before asserting any claims against the Company. While Patriot has agreed to indemnify the Company against any such claims by the DOL, the Company could be responsible for those liabilities if Patriot were not able to fund such indemnification.

Summary_Quarterly_Financial_In

Summary Quarterly Financial Information	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Data [Abstract]
Summary Quarterly Financial Information (Unaudited)	Summary of Quarterly Financial Information (Unaudited)
	A summary of the unaudited quarterly results of operations for the years ended December 31, 2014 and 2013 is presented below.


		Year Ended December 31, 2014
		First Quarter			Second Quarter			Third Quarter			Fourth Quarter
		(In millions, except per share data)
	Revenues	$	1,626.80		$	1,758.00		$	1,722.90		$	1,684.50

	Operating profit (loss)	2.9			32.8			36.2			(207.0		)

	Loss from continuing operations, net of income taxes	(44.3		)	(72.0		)	(154.0		)	(478.8		)
	Net loss	(44.1		)	(71.2		)	(149.0		)	(513.0		)
	Net loss attributable to common stockholders	(48.5		)	(73.3		)	(150.6		)	(514.6		)
	Basic and diluted EPS — continuing operations(1)	$	(0.18	)	$	(0.28	)	$	(0.58	)	$	(1.79	)
	Weighted average shares used in calculating basic and diluted EPS	267.9			268			268.2			268.2


	(1)	EPS for the quarters may not sum to the amounts for the year as each period is computed on a discrete basis.
	Revenues for the second quarter of 2014 included $43.2 million of additional contract revenue, resulting from finalized pricing under a customer sales agreement. Operating loss for the fourth quarter of 2014 reflected $154.4 million of asset impairment and mine closure costs. Operating loss for the fourth quarter of 2014 also included $26.0 million of restructuring and pension settlement charges and a deferred tax asset valuation allowance charge related to an equity affiliate of $52.3 million. Operating profit for the first quarter of 2014 included a charge of $15.6 million related to an adverse judgment in an arbitration proceeding. Loss from continuing operations for the third quarter of 2014 reflected $10.6 million of interest charges related to litigation. Loss from continuing operations for the second quarter of 2014 included $1.6 million of third-party fees related to the debentures consent solicitation. Loss from continuing operations, net of income taxes for the first, second, third and fourth quarters of 2014 included benefits (expenses) related to the remeasurement of foreign income tax accounts of $1.4 million, 1.3 million, $1.2 million and $(1.2) million, respectively. Loss from continuing operations, net of income taxes for the third quarter of 2014 reflected $70.1 million write-off of a net deferred tax asset due to the repeal of the Australian Minerals and Resource Rent Tax in that period (which included $54.0 million of royalty allowance credits recognized during the first half of 2014). Loss from continuing operations, net of income taxes for the first, second, third and fourth quarters of 2014 also reflected respective increases in valuation allowance on certain Australian deferred tax assets of $42.6 million, $75.7 million, $80.6 million and $90.4 million. Loss from continuing operations, net of income taxes, for the fourth quarter of 2014 included an increase in valuation allowance on certain U.S. deferred tax assets of $280.1 million. Loss from discontinued operations, net of income taxes, for the fourth quarter of 2014 reflected a $34.1 million charge, net of tax, related to an adverse change in the fair value of credit support provided to Patriot.



		Year Ended December 31, 2013
		First Quarter			Second Quarter			Third Quarter			Fourth Quarter
		(In millions, except per share data)
	Revenues	$	1,748.00		$	1,725.30		$	1,797.60		$	1,742.80

	Operating profit (loss)	88.8			26.4			112.2			(552.2		)

	(Loss) income from continuing operations, net of income taxes	(10.3		)	101.4			24			(401.1		)

	Net (loss) income	(19.4		)	87.1			(19.1		)	(561.2		)

	Net (loss) income attributable to common stockholders	(23.4		)	90.3			(26.1		)	(565.7		)

	Basic EPS — continuing operations(1)	$	(0.05	)	$	0.39		$	0.06		$	(1.52	)

	Diluted EPS — continuing operations(1)	(0.05		)	0.39			0.06			(1.52		)

	Weighted average shares used in calculating basic EPS	266.9			266.9			267.2			267.3

	Weighted average shares used in calculating diluted EPS	266.9			267.5			267.7			267.3


	(1)	EPS for the quarters may not sum to the amounts for the year as each period is computed on a discrete basis.
	Operating profit (loss) for the fourth quarter of 2013 included $30.6 million of charges associated with the settlement of claims and litigation related to the Patriot bankruptcy reorganization. Operating profit (loss) for the second quarter of 2013 included a $20.6 million charge related to the Gulf Power litigation. Operating profit (loss) for the second and fourth quarter of 2013 reflected $21.5 million and $506.8 million, respectively, of asset impairment and mine closure costs. (Loss) income from continuing operations, net of income taxes, for the first, second and third quarters of 2013 included aggregate losses on early debt extinguishment of $0.9 million, $4.5 million and $11.5 million, respectively, related to first and second quarter voluntary debt repayments and repurchases and the third quarter execution of the 2013 Credit Facility refinancing. (Loss) income from continuing operations, net of income taxes, for the second quarter of 2013 included $6.9 million in prejudgment interest attributable to the Gulf Power litigation. (Loss) income from continuing operations, net of income taxes, for the fourth quarter of 2013 included the $11.3 million tax effect of the aforementioned settlement related to Patriot's bankruptcy reorganization. (Loss) income from continuing operations, net of income taxes, for the fourth quarter of 2013 reflected a net tax benefit of $112.8 million related to asset impairment and mine closure costs. (Loss) income from continuing operations, net of income taxes, for all quarters in 2013 included the impact of the remeasurement of non-U.S. income tax accounts, which amounted to additional tax expense of $1.6 million in the first quarter of 2013 and a tax benefit of $37.1 million, $2.6 million and $6.2 million in the second, third and fourth quarters of 2013, respectively. Net (loss) income for the fourth quarter of 2013 included $61.8 million of after-tax charges recorded in loss from discontinued operations related to the settlement agreement reached with Patriot. Net (loss) income for the third and fourth quarter of 2013 reflected $32.4 million and $42.5 million, respectively, of after-tax asset impairment and mine closure costs related to a discontinued operation.

Segment_Information

Segment Information	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Segment Information	Segment and Geographic Information
	The Company reports its operations primarily through the following reportable segments: "Western U.S. Mining," "Midwestern U.S. Mining," "Australian Mining," "Trading and Brokerage" and "Corporate and Other."
	The Company's Western U.S. Mining operations reflect the aggregation of the Powder River Basin, Southwest and Colorado mining operations. The mines in that segment are characterized by predominantly surface mining extraction processes, coal with a lower sulfur content and Btu and higher customer transportation costs (due to longer shipping distances). The Company's Midwestern U.S. Mining operations reflect the Company’s Illinois and Indiana mining operations, which are characterized by a mix of surface and underground mining extraction processes, coal with a higher sulfur content and Btu and lower customer transportation costs (due to shorter shipping distances). Geologically, Western operations mine bituminous and sub-bituminous coal deposits, and Midwestern operations mine bituminous coal deposits. The principal business of the Western and Midwestern U.S. Mining segments is the mining, preparation and sale of thermal coal, sold primarily to electric utilities in the U.S., with a portion sold into the seaborne markets.
	The Company’s Australian Mining operations consist of its mines in Queensland and New South Wales, Australia. The mines in that segment are characterized by both surface and underground extraction processes, mining various qualities of metallurgical (low-sulfur, high Btu coal) and thermal coal. The metallurgical coal qualities include hard coking coal, semi-hard coking coal, semi-soft coal and pulverized coal injection coal. The business of the Company's Australian Mining operations are primarily export focused with customers spread across several countries, while a portion of the coal is sold within Australia. Generally, revenues from individual countries vary year by year based on the demand for electricity, the demand for steel, the strength of the global economy and several other factors, including those specific to each country.
	The Company’s Trading and Brokerage segment brokers coal sales of other coal producers both as principal and agent, and trades coal and freight-related contracts. Corporate and Other, includes selling and administrative expenses, mining and export/transportation joint ventures, restructuring and pension settlement charges and activities associated with the optimization of our coal reserve and real estate holdings, the closure of inactive mining sites and certain energy-related commercial matters.
	The Company’s chief operating decision maker uses Adjusted EBITDA as the primary measure of segment profit and loss. Beginning with this report, the Company modified its definition of Adjusted EBITDA to also exclude the impact of changes in deferred tax asset valuation allowance related to equity affiliates because the Company believes that doing so is useful in comparing its 2014 results with those of prior periods. Also beginning in 2014, the Company modified its expense allocation practices to exclude restructuring and pension settlement charges from its Australian Mining, Western U.S. Mining, Midwestern U.S. Mining and Trading and Brokerage segment results because it believes such items do not reflect the core operating performance of those segments. Accordingly, such charges are now entirely reflected in the Corporate and Other segment. Segment results from prior periods have been reclassified to conform to the 2014 presentation. The Company defines Adjusted EBITDA as (loss) income from continuing operations before deducting net interest expense; income taxes; asset retirement obligation expenses, depreciation, depletion and amortization; asset impairment and mine closure costs; charges for the settlement of claims and litigation related to previously divested operations and changes in deferred tax asset valuation allowance and amortization of basis difference related to equity affiliates.
	Segment results for the year ended December 31, 2014 were as follows (assets as of December 31, 2014):


		Western				Midwestern				Australian			Trading and				Corporate				Consolidated
		U.S. Mining				U.S. Mining				Mining			Brokerage				and Other
		(Dollars in millions)
	Revenues	$	2,825.70			$	1,198.10			$	2,671.80		$	58.4			$	38.2			$	6,792.20

	Adjusted EBITDA	770.4				301.4				74.4			14.9				(347.1		)		814

	Total assets	3,431.30				667.8				6,623.90			300.7				2,167.40				13,191.10

	Property, plant, equipment and mine development, net	3,127.80				612.1				5,503.70			1.1				1,332.60				10,577.30

	Additions to property, plant, equipment and mine development	37.9				57.4				84.1			—				15				194.4

	Federal coal lease expenditures	276.7				—				—			—				—				276.7

	Loss from equity affiliates	—				—				—			—				107.6				107.6

	Segment results for the year ended December 31, 2013 were as follows (assets as of December 31, 2013):


		Western				Midwestern				Australian			Trading and				Corporate				Consolidated
		U.S. Mining				U.S. Mining				Mining			Brokerage				and Other
		(Dollars in millions)
	Revenues	$	2,669.60			$	1,335.50			$	2,904.60		$	66			$	38			$	7,013.70

	Adjusted EBITDA	698.3				428.3				316.6			(19.9		)		(376.1		)		1,047.20

	Total assets	3,307.60				716.8				7,081.20			389.6				2,638.20				14,133.40

	Property, plant, equipment and mine development, net	2,986.80				667.6				5,947.10			1.8				1,479.20				11,082.50

	Additions to property, plant, equipment and mine development	48				27.2				230.3			0.1				22.8				328.4

	Federal coal lease expenditures	276.8				—				—			—				—				276.8

	Loss from equity affiliates	—				—				—			—				40.2				40.2

	Segment results for the year ended December 31, 2012 were as follows (assets as of December 31, 2012):


		Western				Midwestern				Australian			Trading and				Corporate				Consolidated
		U.S. Mining				U.S. Mining				Mining			Brokerage				and Other
		(Dollars in millions)
	Revenues	$	2,949.30			$	1,403.70			$	3,503.60		$	199.9			$	21			$	8,077.50

	Adjusted EBITDA	832.8				427				938.9			119.7				(481.9		)		1,836.50

	Total assets	3,257.90				728.5				7,990.80			543.9				3,287.90				15,809.00

	Property, plant, equipment and mine development, net	2,896.10				707.5				6,595.50			1.6				1,601.00				11,801.70

	Additions to property, plant, equipment and mine development	121.4				74.7				743.4			0.1				46.4				986

	Federal coal lease expenditures	276.5				—				—			—				—				276.5

Loss from equity affiliates	—				—				—			—				61.2				61.2

A reconciliation of Adjusted EBITDA to consolidated loss from continuing operations, net of income taxes follows:


	Year Ended December 31,
	2014				2013				2012
	(Dollars in millions)
Total Adjusted EBITDA	$	814			$	1,047.20			$	1,836.50

Depreciation, depletion and amortization	(655.7		)		(740.3		)		(663.4		)
Asset retirement obligation expenses	(81.0		)		(66.5		)		(67.0		)
Asset impairment and mine closure costs	(154.4		)		(528.3		)		(929.0		)
Settlement charges related to the Patriot bankruptcy reorganization	—				(30.6		)		—

Change in deferred tax asset valuation allowance related to equity affiliates	(52.3		)		—				—

Amortization of basis difference related to equity affiliates	(5.7		)		(6.3		)		(4.6		)
Interest expense	(428.2		)		(425.2		)		(405.6		)
Interest income	15.4				15.7				24.5

Income tax (provision) benefit	(201.2		)		448.3				(262.3		)

Loss from continuing operations, net of income taxes	$	(749.1	)		$	(286.0	)		$	(470.9	)
The following table presents revenues as a percent of total revenue from external customers by geographic region:


	Year Ended December 31,
	2014			2013			2012
U.S.	59.5	%		61.1	%		55.4	%
Japan	9.5	%		9.8	%		12.3	%
China	6.1	%		10.2	%		6.8	%
South Korea	5.2	%		3.8	%		5.8	%
Other	19.7	%		15.1	%		19.7	%
Total	100	%		100	%		100	%
The Company attributes revenue to individual countries based on the location of the physical delivery of the coal.

Supplemental_GuarantorNonGuara

Supplemental Guarantor/Non-Guarantor Financial Information	12 Months Ended
	Dec. 31, 2014
Supplemental Guarantor Non Guarantor Financial Information [Abstract]
Supplemental Guarantor/Non-Guarantor Financial Information	Supplemental Guarantor/Non-Guarantor Financial Information
	In accordance with the indentures governing the 7.375% Senior Notes due November 2016, the 6.00% Senior Notes due November 2018, the 6.50% Senior Notes due September 2020, the 6.25% Senior Notes due November 2021 and the 7.875% Senior Notes due November 2026 (collectively the Senior Notes), certain 100% owned U.S. subsidiaries of the Company (each, a Guarantor Subsidiary) have fully and unconditionally guaranteed the Senior Notes, on a joint and several basis.The indentures governing the Senior Notes contain customary exceptions under which a guarantee of a Guarantor Subsidiary will terminate, including (1) the release or discharge of the guarantee of the Company’s 2013 Credit Facility by such Guarantor Subsidiary, except a discharge or release by or as a result of payment under such guarantee, (2) a sale or other disposition, by way of merger, consolidation or otherwise, of all of the capital stock of such Guarantor Subsidiary, and (3) the legal defeasance or discharge of the indentures. Separate financial statements and other disclosures concerning the Guarantor Subsidiaries are not presented because management believes that such information is not material to the holders of the Senior Notes. The following historical financial statement information is provided for the Guarantor/Non-Guarantor Subsidiaries.
	PEABODY ENERGY CORPORATION
	SUPPLEMENTAL CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS


		Year Ended December 31, 2014
		Parent				Guarantor				Non-Guarantor				Eliminations				Consolidated
		Company				Subsidiaries				Subsidiaries
		(Dollars in millions)
	Total revenues	$	—			$	3,964.80			$	2,902.10			$	(74.7	)		$	6,792.20

	Costs and expenses

	Operating costs and expenses (exclusive of items shown separately below)	49.6				2,927.30				2,814.70				(74.7		)		5,716.90

	Depreciation, depletion and amortization	—				310.4				345.3				—				655.7

	Asset retirement obligation expenses	—				25.3				55.7				—				81

	Selling and administrative expenses	46.8				161.1				19.2				—				227.1

	Restructuring and pension settlement charges	—				23.8				2.2				—				26

	Other operating (income) loss:

	Net gain on disposal or exchange of assets	—				(18.5		)		(22.9		)		—				(41.4		)

	Asset impairment and mine closure costs	4.7				71.1				78.6				—				154.4

	Loss from equity affiliates and investment in subsidiaries	431.1				6.6				101				(431.1		)		107.6

	Interest expense	424.7				6.4				34.6				(37.5		)		428.2

	Interest income	(15.3		)		(10.3		)		(27.3		)		37.5				(15.4		)

	(Loss) income from continuing operations before income taxes	(941.6		)		461.6				(499.0		)		431.1				(547.9		)

	Income tax (benefit) provision	(186.2		)		316.7				70.7				—				201.2

	(Loss) income from continuing operations, net of income taxes	(755.4		)		144.9				(569.7		)		431.1				(749.1		)

	(Loss) income from discontinued operations, net of income taxes	(31.6		)		(7.2		)		10.6				—				(28.2		)

	Net (loss) income	(787.0		)		137.7				(559.1		)		431.1				(777.3		)

	Less: Net income attributable to noncontrolling interests	—				—				9.7				—				9.7

	Net (loss) income attributable to common stockholders	$	(787.0	)		$	137.7			$	(568.8	)		$	431.1			$	(787.0	)

	PEABODY ENERGY CORPORATION
	SUPPLEMENTAL CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS


		Year Ended December 31, 2013
		Parent				Guarantor				Non-Guarantor				Eliminations				Consolidated
		Company				Subsidiaries				Subsidiaries
		(Dollars in millions)
	Total revenues	$	—			$	4,027.90			$	3,230.30			$	(244.5	)		$	7,013.70

	Costs and expenses

	Operating costs and expenses (exclusive of items shown separately below)	(173.6		)		3,471.70				2,675.50				(244.5		)		5,729.10

Depreciation, depletion and amortization	—				329.4				410.9				—				740.3

Asset retirement obligation expenses	—				33.3				33.2				—				66.5

Selling and administrative expenses	50.9				167.9				25.4				—				244.2

Restructuring and pension settlement charges	—				11.9				—				—				11.9

Other operating (income) loss:

Net gain on disposal or exchange of assets	—				(52.6		)		—				—				(52.6		)

Asset impairment and mine closure costs	21.5				6.5				500.3				—				528.3

Settlement charges related to the Patriot bankruptcy reorganization	30.6				—				—				—				30.6

Loss from equity affiliates and investment in subsidiaries	272.5				8.3				31.9				(272.5		)		40.2

Interest expense	420.8				244.5				169				(409.1		)		425.2

(Gain) loss from extinguishment of affiliate debt	—				(155.5		)		155.5				—				—

Interest income	(79.6		)		(311.6		)		(33.6		)		409.1				(15.7		)

Unrealized loss (gain) on derivatives	—				34				(34.0		)		—				—

(Loss) income from continuing operations before income taxes	(543.1		)		240.1				(703.8		)		272.5				(734.3		)

Income tax benefit	(92.2		)		(110.9		)		(245.2		)		—				(448.3		)

(Loss) income from continuing operations, net of income taxes	(450.9		)		351				(458.6		)		272.5				(286.0		)

Loss from discontinued operations, net of income taxes	(74.0		)		(5.6		)		(147.0		)		—				(226.6		)

Net (loss) income	(524.9		)		345.4				(605.6		)		272.5				(512.6		)

Less: Net income attributable to noncontrolling interests	—				—				12.3				—				12.3

Net (loss) income attributable to common stockholders	$	(524.9	)		$	345.4			$	(617.9	)		$	272.5			$	(524.9	)

PEABODY ENERGY CORPORATION
SUPPLEMENTAL CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS


	Year Ended December 31, 2012
	Parent				Guarantor				Non-Guarantor				Eliminations				Consolidated
	Company				Subsidiaries				Subsidiaries
	(Dollars in millions)
Total revenues	$	—			$	4,571.30			$	3,738.40			$	(232.2	)		$	8,077.50

Costs and expenses

Operating costs and expenses (exclusive of items shown separately below)	(395.2		)		3,344.10				3,216.00				(232.2		)		5,932.70

Depreciation, depletion and amortization	—				315.6				347.8				—				663.4

Asset retirement obligation expenses	—				42.9				24.1				—				67

Selling and administrative expenses	38.7				199.7				30.4				—				268.8

Other operating (income) loss:

Net gain on disposal or exchange of assets	—				(14.7		)		(2.4		)		—				(17.1		)

Asset impairment and mine closure costs	35.5				86.8				806.7				—				929

Loss from equity affiliates and investment in subsidiaries	720				12.5				48.7				(720.0		)		61.2

Interest expense	413.9				13.9				475.6				(497.8		)		405.6

Interest income	(309.8		)		(149.1		)		(63.4		)		497.8				(24.5		)

Unrealized (gain) loss on derivatives	—				(35.3		)		35.3				—				—

(Loss) income from continuing operations before income taxes	(503.1		)		754.9				(1,180.4		)		720				(208.6		)

Income tax provision	80.2				105.8				76.3				—				262.3

(Loss) income from continuing operations, net of income taxes	(583.3		)		649.1				(1,256.7		)		720				(470.9		)

Loss from discontinued operations, net of income taxes	(2.4		)		(82.2		)		(19.6		)		—				(104.2		)

Net (loss) income	(585.7		)		566.9				(1,276.3		)		720				(575.1		)

Less: Net income attributable to noncontrolling interests	—				—				10.6				—				10.6

Net (loss) income attributable to common stockholders	$	(585.7	)		$	566.9			$	(1,286.9	)		$	720			$	(585.7	)

PEABODY ENERGY CORPORATION
SUPPLEMENTAL CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME


	Year Ended December 31, 2014
	Parent				Guarantor				Non-Guarantor				Eliminations				Consolidated
	Company				Subsidiaries				Subsidiaries
	(Dollars in millions)
Net (loss) income	$	(787.0	)		$	137.7			$	(559.1	)		$	431.1			$	(777.3	)

Other comprehensive (loss) income, net of income taxes:

Net change in unrealized losses on available-for-sale securities (net of $0.5 tax benefit)
Unrealized holding losses on available-for-sale securities	(3.7		)		—				—				—				(3.7		)

Less: Reclassification for realized losses included in net (loss) income	2.9				—				—				—				2.9

Net change in unrealized losses on available-for-sale securities	(0.8		)		—				—				—				(0.8		)

Net unrealized losses on cash flow hedges (net of $54.6 tax benefit)

(Decrease) increase in fair value of cash flow hedges	(225.9		)		—				30.9				—				(195.0		)

Less: Reclassification for realized losses (gains) included in net (loss) income	31.3				—				(41.5		)		—				(10.2		)

Net unrealized losses on cash flow hedges	(194.6		)		—				(10.6		)		—				(205.2		)

Postretirement plans and workers' compensation obligations (net of $10.3 tax benefit)

Prior service credit for the period	—				11.4				—				—				11.4

Net actuarial (loss) gain for the period	—				(150.2		)		7.5				—				(142.7		)

Amortization of actuarial loss (gain) and prior service cost	—				35.5				(2.8		)		—				32.7

Postretirement plans and workers' compensation obligations	—				(103.3		)		4.7				—				(98.6		)

Foreign currency translation adjustment	—				—				(41.0		)		—				(41.0		)

Other comprehensive loss from investment in subsidiaries	(150.2		)		—				—				150.2				—

Other comprehensive loss, net of income taxes	(345.6		)		(103.3		)		(46.9		)		150.2				(345.6		)

Comprehensive (loss) income	(1,132.6		)		34.4				(606.0		)		581.3				(1,122.9		)

Less: Comprehensive income attributable to noncontrolling interests	—				—				9.7				—				9.7

Comprehensive (loss) income attributable to common stockholders	$	(1,132.6	)		$	34.4			$	(615.7	)		$	581.3			$	(1,132.6	)

PEABODY ENERGY CORPORATION
SUPPLEMENTAL CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME


	Year Ended December 31, 2013
	Parent				Guarantor				Non-Guarantor				Eliminations				Consolidated
	Company				Subsidiaries				Subsidiaries
	(Dollars in millions)
Net (loss) income	$	(524.9	)		$	345.4			$	(605.6	)		$	272.5			$	(512.6	)

Other comprehensive (loss) income, net of income taxes:

Net change in unrealized gains (losses) on available-for-sale securities (net of $0.5 tax provision)
Unrealized holding losses on available-for-sale securities	(12.2		)		—				(0.1		)		—				(12.3		)

Less: Reclassification for realized losses (gains) included in net income	13				—				(0.2		)		—				12.8

Net change in unrealized gains (losses) on available-for-sale securities	0.8				—				(0.3		)		—				0.5

Net unrealized losses on cash flow hedges (net of $300.0 tax benefit)

(Decrease) increase in fair value of cash flow hedges	(368.4		)		—				34.8				—				(333.6		)

Less: Reclassification for realized gains included in net income	(109.0		)		—				(100.6		)		—				(209.6		)

Net unrealized losses on cash flow hedges	(477.4		)		—				(65.8		)		—				(543.2		)

Postretirement plans and workers' compensation obligations (net of $121.7 tax provision)

Prior service cost for the period	—				(1.4		)		—				—				(1.4		)

Net actuarial gain for the period	—				103.8				7.1				—				110.9

Amortization of actuarial loss (gain) and prior service cost	—				95.8				(0.1		)		—				95.7

Postretirement plans and workers' compensation obligations	—				198.2				7				—				205.2

Foreign currency translation adjustment	—				—				(92.7		)		—				(92.7		)

Other comprehensive income from investment in subsidiaries	46.4				—				—				(46.4		)		—

Other comprehensive (loss) income, net of income taxes	(430.2		)		198.2				(151.8		)		(46.4		)		(430.2		)

Comprehensive (loss) income	(955.1		)		543.6				(757.4		)		226.1				(942.8		)

Less: Comprehensive income attributable to noncontrolling interests	—				—				12.3				—				12.3

Comprehensive (loss) income attributable to common stockholders	$	(955.1	)		$	543.6			$	(769.7	)		$	226.1			$	(955.1	)

PEABODY ENERGY CORPORATION
SUPPLEMENTAL CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME


	Year Ended December 31, 2012
	Parent				Guarantor				Non-Guarantor				Eliminations				Consolidated
	Company				Subsidiaries				Subsidiaries
	(Dollars in millions)
Net (loss) income	$	(585.7	)		$	566.9			$	(1,276.3	)		$	720			$	(575.1	)

Other comprehensive income, net of income taxes:
Net change in unrealized gains (losses) on available-for-sale securities (net of $4.0 tax provision)
Unrealized holding losses on available-for-sale securities	(15.5		)		—				—				—				(15.5		)

Less: Reclassification for realized losses included in net income	22.5				—				—				—				22.5

Net change in unrealized gains on available-for-sale securities	7				—				—				—				7

Net unrealized losses on cash flow hedges (net of $3.9 tax benefit)

Increase in fair value of cash flow hedges	205.9				—				144.5				—				350.4

Less: Reclassification for realized gains included in net income	(249.1		)		—				(49.5		)		—				(298.6		)

Net unrealized (losses) gains on cash flow hedges	(43.2		)		—				95				—				51.8

Postretirement plans and workers' compensation obligations (net of $43.9 tax provision)

Prior service cost for the period	—				20.1				—				—				20.1

Net actuarial (loss) gain for the period	—				(0.9		)		0.9				—				—

Amortization of actuarial loss and prior service cost	—				54.5				0.9				—				55.4

Postretirement plans and workers' compensation obligations	—				73.7				1.8				—				75.5

Foreign currency translation adjustment	—				—				19.1				—				19.1

Other comprehensive income from investment in subsidiaries	189.6				—				—				(189.6		)		—

Other comprehensive income, net of income taxes	153.4				73.7				115.9				(189.6		)		153.4

Comprehensive (loss) income	(432.3		)		640.6				(1,160.4		)		530.4				(421.7		)

Less: Comprehensive income attributable to noncontrolling interests	—				—				10.6				—				10.6

Comprehensive (loss) income attributable to common stockholders	$	(432.3	)		$	640.6			$	(1,171.0	)		$	530.4			$	(432.3	)

PEABODY ENERGY CORPORATION
SUPPLEMENTAL CONDENSED CONSOLIDATING BALANCE SHEETS


	December 31, 2014
	Parent				Guarantor				Non-Guarantor				Reclassifications/				Consolidated
	Company				Subsidiaries				Subsidiaries				Eliminations
	(Dollars in millions)
Assets

Current assets

Cash and cash equivalents	$	188.7			$	1.2			$	108.1			$	—			$	298

Accounts receivable, net	—				14.5				548.6				—				563.1

Receivables from affiliates, net	258.4				—				105.9				(364.3		)		—

Inventories	—				191.8				214.7				—				406.5

Assets from coal trading activities, net	—				53.8				3.8				—				57.6

Deferred income taxes	64.5				8.6				6.9				—				80

Other current assets	—				44.5				261.3				—				305.8

Total current assets	511.6				314.4				1,249.30				(364.3		)		1,711.00

Property, plant, equipment and mine development, net	—				5,005.20				5,572.10				—				10,577.30

Deferred income taxes	—				8.2				—				(7.5		)		0.7

Investments and other assets	10,209.40				4				621.6				(9,932.9		)		902.1

Notes receivable from affiliates, net	—				1,655.70				—				(1,655.7		)		—

Total assets	$	10,721.00			$	6,987.50			$	7,443.00			$	(11,960.4	)		$	13,191.10

Liabilities and Stockholders’ Equity

Current liabilities

Current maturities of long-term debt	$	12			$	0.1			$	9.1			$	—			$	21.2

Payables to affiliates, net	—				364.3				—				(364.3		)		—

Liabilities from coal trading activities, net	—				10.7				22				—				32.7

Accounts payable and accrued expenses	474.5				682.5				652.2				—				1,809.20

Total current liabilities	486.5				1,057.60				683.3				(364.3		)		1,863.10

Long-term debt, less current maturities	5,951.60				6.3				7.7				—				5,965.60

Deferred income taxes	90.5				—				6.1				(7.5		)		89.1

Notes payable to affiliates, net	1,033.40				—				622.3				(1,655.7		)		—

Other noncurrent liabilities	434.2				1,717.40				395.2				—				2,546.80

Total liabilities	7,996.20				2,781.30				1,714.60				(2,027.5		)		10,464.60

Peabody Energy Corporation’s stockholders’ equity	2,724.80				4,206.20				5,726.70				(9,932.9		)		2,724.80

Noncontrolling interests	—				—				1.7				—				1.7

Total stockholders’ equity	2,724.80				4,206.20				5,728.40				(9,932.9		)		2,726.50

Total liabilities and stockholders’ equity	$	10,721.00			$	6,987.50			$	7,443.00			$	(11,960.4	)		$	13,191.10

PEABODY ENERGY CORPORATION
SUPPLEMENTAL CONDENSED CONSOLIDATING BALANCE SHEETS


	December 31, 2013
	Parent				Guarantor				Non-Guarantor				Reclassifications/				Consolidated
	Company				Subsidiaries				Subsidiaries				Eliminations
					(Dollars in millions)
Assets

Current assets

Cash and cash equivalents	$	300.7			$	0.3			$	143			$	—			$	444

Accounts receivable, net	1.3				—				559.1				(2.5		)		557.9

Receivables from affiliates, net	68.4				—				—				(68.4		)		—

Inventories	—				235.1				271.6				—				506.7

Assets from coal trading activities, net	—				46.7				—				(10.6		)		36.1

Deferred income taxes	—				61.9				6.4				(1.9		)		66.4

Other current assets	34.5				73.7				273.4				—				381.6

Total current assets	404.9				417.7				1,253.50				(83.4		)		1,992.70

Property, plant, equipment and mine development, net	—				5,055.70				6,026.80				—				11,082.50

Deferred income taxes	16.5				—				7.8				(16.5		)		7.8

Investments and other assets	11,394.90				8.8				762.6				(11,115.9		)		1,050.40

Notes receivable from affiliates, net	—				1,433.00				—				(1,433.0		)		—

Total assets	$	11,816.30			$	6,915.20			$	8,050.70			$	(12,648.8	)		$	14,133.40

Liabilities and Stockholders’ Equity

Current liabilities

Current maturities of long-term debt	$	12			$	0.1			$	19.6			$	—			$	31.7

Payables to affiliates, net	—				10.4				58				(68.4		)		—

Deferred income taxes	1.9				—				—				(1.9		)		—

Liabilities from coal trading activities, net	—				0.2				16.5				(10.6		)		6.1

Accounts payable and accrued expenses	360				601.4				805.1				(2.5		)		1,764.00

Total current liabilities	373.9				612.1				899.2				(83.4		)		1,801.80

Long-term debt, less current maturities	5,959.10				6.5				5.1				—				5,970.70

Deferred income taxes	—				55.9				1.5				(16.5		)		40.9

Notes payable to affiliates, net	1,032.60				—				400.4				(1,433.0		)		—

Other noncurrent liabilities	542				1,452.50				377.6				—				2,372.10

Total liabilities	7,907.60				2,127.00				1,683.80				(1,532.9		)		10,185.50

Peabody Energy Corporation’s stockholders’ equity	3,908.70				4,788.20				6,327.70				(11,115.9		)		3,908.70

Noncontrolling interests	—				—				39.2				—				39.2

Total stockholders’ equity	3,908.70				4,788.20				6,366.90				(11,115.9		)		3,947.90

Total liabilities and stockholders’ equity	$	11,816.30			$	6,915.20			$	8,050.70			$	(12,648.8	)		$	14,133.40

PEABODY ENERGY CORPORATION
SUPPLEMENTAL CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS


	Year Ended December 31, 2014
	Parent				Guarantor				Non-Guarantor				Consolidated
	Company				Subsidiaries				Subsidiaries
					(Dollars in millions)
Cash Flows From Operating Activities

Net cash (used in) provided by continuing operations	$	(369.0	)		$	776.1			$	33.9			$	441

Net cash used in discontinued operations	(73.3		)		(4.6		)		(26.5		)		(104.4		)
Net cash (used in) provided by operating activities	(442.3		)		771.5				7.4				336.6

Cash Flows From Investing Activities

Additions to property, plant, equipment and mine development	—				(108.5		)		(85.9		)		(194.4		)

Changes in accrued expenses related to capital expenditures	—				3.4				(20.0		)		(16.6		)

Federal coal lease expenditures	—				(276.7		)		—				(276.7		)

Proceeds from disposal of assets, net of notes receivable	—				105.9				97.8				203.7

Purchases of debt securities	—				—				(15.1		)		(15.1		)

Proceeds from sales and maturities of debt securities	—				—				13.5				13.5

Contributions to joint ventures	—				—				(529.8		)		(529.8		)

Distributions from joint ventures	—				—				534.2				534.2

Advances to related parties	—				—				(33.7		)		(33.7		)

Repayment of loans from related parties	—				—				5.4				5.4

Other, net	—				(4.4		)		(0.6		)		(5.0		)

Net cash used in investing activities	—				(280.3		)		(34.2		)		(314.5		)

Cash Flows From Financing Activities
Proceeds from long-term debt	—				—				1.1				1.1

Repayments of long-term debt	(12.0		)		(0.1		)		(8.9		)		(21.0		)
Payment of deferred financing costs	(10.1		)		—				—				(10.1		)

Dividends paid	(92.3		)		—				—				(92.3		)

Restricted cash for distributions to noncontrolling interest	—				—				(42.5		)		(42.5		)

Other, net	3.1				(1.7		)		(4.7		)		(3.3		)

Transactions with affiliates, net	441.6				(488.5		)		46.9				—

Net cash provided by (used in) financing activities	330.3				(490.3		)		(8.1		)		(168.1		)

Net change in cash and cash equivalents	$	(112.0	)		$	0.9			$	(34.9	)		$	(146.0	)

Cash and cash equivalents at beginning of year	300.7				0.3				143				444

Cash and cash equivalents at end of year	$	188.7			$	1.2			$	108.1			$	298

PEABODY ENERGY CORPORATION
SUPPLEMENTAL CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS


	Year Ended December 31, 2013
	Parent				Guarantor				Non-Guarantor				Consolidated
	Company				Subsidiaries				Subsidiaries
					(Dollars in millions)
Cash Flows From Operating Activities

Net cash (used in) provided by continuing operations	$	(24.3	)		$	778.7			$	25.7			$	780.1

Net cash used in discontinued operations	(20.4		)		(7.6		)		(29.7		)		(57.7		)
Net cash (used in) provided by operating activities	(44.7		)		771.1				(4.0		)		722.4

Cash Flows From Investing Activities

Additions to property, plant, equipment and mine development	—				(95.9		)		(232.5		)		(328.4		)

Changes in accrued expenses related to capital expenditures	—				(1.2		)		(119.5		)		(120.7		)

Federal coal lease expenditures	—				(276.8		)		—				(276.8		)

Proceeds from disposal of assets, net of notes receivable	—				93				85.3				178.3

Purchases of debt securities	—				—				(22.8		)		(22.8		)

Proceeds from sales and maturities of debt securities	—				—				22.9				22.9

Maturity of short-term investments	—				—				4.8				4.8

Contributions to joint ventures	—				—				(671.7		)		(671.7		)

Distributions from joint ventures	—				—				722.9				722.9

Advances to related parties	—				—				(42.1		)		(42.1		)

Repayment of loan from related parties	—				—				25.2				25.2

Other, net	—				(5.7		)		(0.1		)		(5.8		)

Net cash used in continuing operations	—				(286.6		)		(227.6		)		(514.2		)

Net cash used in discontinued operations	—				—				(1.5		)		(1.5		)

Net cash used in investing activities	—				(286.6		)		(229.1		)		(515.7		)

Cash Flows From Financing Activities
Proceeds from long-term debt	1,188.00				—				—				1,188.00

Repayments of long-term debt	(1,334.2		)		(0.2		)		(55.8		)		(1,390.2		)
Payment of deferred financing costs	(22.8		)		—				—				(22.8		)

Dividends paid	(91.7		)		—				—				(91.7		)

Other, net	4.2				(1.6		)		(7.4		)		(4.8		)

Transactions with affiliates, net	332.3				(482.7		)		150.4				—

Net cash provided by (used in) financing activities	75.8				(484.5		)		87.2				(321.5		)

Net change in cash and cash equivalents	$	31.1			$	—			$	(145.9	)		$	(114.8	)

Cash and cash equivalents at beginning of year	269.6				0.3				288.9				558.8

Cash and cash equivalents at end of year	$	300.7			$	0.3			$	143			$	444

PEABODY ENERGY CORPORATION
SUPPLEMENTAL CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS


	Year Ended December 31, 2012
	Parent				Guarantor				Non-Guarantor				Consolidated
	Company				Subsidiaries				Subsidiaries
					(Dollars in millions)
Cash Flows From Operating Activities

Net cash provided by (used in) continuing operations	$	372			$	1,390.30			$	(162.5	)		$	1,599.80

Net cash used in discontinued operations	(3.4		)		(11.6		)		(69.7		)		(84.7		)
Net cash provided by (used in) operating activities	368.6				1,378.70				(232.2		)		1,515.10

Cash Flows From Investing Activities

Additions to property, plant, equipment and mine development	—				(237.4		)		(748.6		)		(986.0		)

Changes in accrued expenses related to capital expenditures	—				3.1				101.6				104.7

Federal coal lease expenditures	—				(276.5		)		—				(276.5		)

Investment in Prairie State Energy Campus	—				(10.7		)		—				(10.7		)

Proceeds from disposal of assets, net of notes receivable	—				70.1				77.8				147.9

Purchases of debt and equity securities	—				—				(46.7		)		(46.7		)

Proceeds from sales of debt and equity securities	—				—				46.4				46.4

Purchase of short-term investments	—				—				(4.8		)		(4.8		)

Contributions to joint ventures	—				—				(824.0		)		(824.0		)

Distributions from joint ventures	—				—				823				823

Advances to related parties	—				—				(148.0		)		(148.0		)

Repayment of loans from related parties	—				—				110.8				110.8

Other, net	—				(6.2		)		—				(6.2		)

Net cash used in continuing operations	—				(457.6		)		(612.5		)		(1,070.1		)

Net cash used in discontinued operations	—				(1.1		)		(20.9		)		(22.0		)

Net cash used in investing activities	—				(458.7		)		(633.4		)		(1,092.1		)

Cash Flows From Financing Activities

Proceeds from long-term debt	—				—				0.8				0.8

Repayments of long-term debt	(379.0		)		(0.4		)		(36.4		)		(415.8		)
Payment of deferred financing costs	(6.9		)		—				—				(6.9		)

Dividends paid	(91.9		)		—				—				(91.9		)

Common stock repurchase	(99.9		)		—								(99.9		)

Excess tax benefits related to share-based compensation	8.3				—				—				8.3

Acquisition of MCG Coal Holdings Pty Ltd noncontrolling interests	—				—				(49.8		)		(49.8		)

Other, net	1				—				(9.1		)		(8.1		)

Transactions with affiliates, net	186.2				(920.1		)		733.9				—

Net cash (used in) provided by financing activities	(382.2		)		(920.5		)		639.4				(663.3		)

Net change in cash and cash equivalents	$	(13.6	)		$	(0.5	)		$	(226.2	)		$	(240.3	)
Cash and cash equivalents at beginning of year	283.2				0.8				515.1				799.1

Cash and cash equivalents at end of year	$	269.6			$	0.3			$	288.9			$	558.8

Valuation_and_Qualifying_Accou

Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2014
Valuation and Qualifying Accounts [Abstract]
VALUATION AND QUALIFYING ACCOUNTS	PEABODY ENERGY CORPORATION
	SCHEDULE II — VALUATION AND QUALIFYING ACCOUNTS



	Description		Balance at		Charged to			Deductions(1)				Other				Balance
			Beginning of Period		Costs and Expenses											at End of Period
			(Dollars in millions)
	Year Ended December 31, 2014

	Reserves deducted from asset accounts:

	Advance royalty recoupment reserve		$	9.7	$	(0.2	)	$	(1.9	)	(2)	$	—			$	7.6

	Reserve for materials and supplies		7.4		(0.1		)	(2.7		)		—				4.6

	Allowance for doubtful accounts		7.4		1.5			(1.4		)		(1.7		)	(3)	5.8

	Tax valuation allowances		1,634.10		569.4			—				(1,034.5		)	(4)	1,169.00

	Year Ended December 31, 2013

	Reserves deducted from asset accounts:

	Advance royalty recoupment reserve		$	15.3	$	0.1		$	(5.7	)	(2)	$	—			$	9.7

	Reserve for materials and supplies		16		1.7			(10.3		)		—				7.4

	Allowance for doubtful accounts		13.7		4.3			(10.1		)		(0.5		)	(3)	7.4

	Tax valuation allowances		1,481.80		(29.4		)	—				181.7			(5)	1,634.10

	Year Ended December 31, 2012

	Reserves deducted from asset accounts:

	Advance royalty recoupment reserve		$	21.3	$	2.9		$	(9.0	)	(2)	$	0.1		(6)	$	15.3

	Reserve for materials and supplies		6.5		13.7			(4.2		)		—				16

	Allowance for doubtful accounts		17		(0.5		)	(0.7		)		(2.1		)	(3)	13.7

	Tax valuation allowances		79.8		521.5			(77.0		)	(7)	957.5			(8)	1,481.80


	(1)	Reserves utilized, unless otherwise indicated.

	(2)	Deductions to advance royalty recoupment reserve represents the termination of federal and state leases.

	(3)	Represents subsequent recovery of receivable amounts previously reserved.

	(4)	Includes the write-off of valuation allowance against deferred tax assets related to the Australian Minerals and Resource Rent Tax (MRRT) due to the repeal of that legislation in 2014, along with an increase in valuation allowance during the period reflected directly in "Accumulated other comprehensive loss" and the impact of the 2014 decrease in Australian dollar exchange rates.

	(5)	Related to the MRRT, as offset by the impact of the 2013 decrease in Australian dollar exchange rates.

	(6)	Balances transferred from other accounts or reserves recorded as part of a property transaction or acquisition.

	(7)	Deductions include write-off of loss carryforwards and reversal of related valuation allowances.

	(8)	Includes changes to valuation allowances primarily related to deferred tax assets acquired in business combinations and initial deferred tax assets resulting from the MRRT implemented in Australia in 2012.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies Discussion (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation
	The consolidated financial statements include the accounts of Peabody Energy Corporation (the Company) and its affiliates. Interests in subsidiaries controlled by the Company are consolidated with any outside shareholder interests reflected as noncontrolling interests, except when the Company has an undivided interest in an unincorporated joint venture. In those cases, the Company includes its proportionate share in the assets, liabilities, revenues and expenses of the jointly controlled entities within each applicable line item of the consolidated financial statements. All intercompany transactions, profits and balances have been eliminated in consolidation. Certain amounts from prior years have been reclassified to conform with the 2014 presentation.
Description of Business	Description of Business
	The Company is engaged in the mining of thermal coal for sale primarily to electric utilities and metallurgical coal for sale to industrial customers. The Company’s mining operations are located in the United States (U.S.) and Australia, including an equity-affiliate mining operation in Australia. The Company also markets and brokers coal from other coal producers, both as principal and agent, and trades coal and freight-related contracts through trading and business offices in Australia, China, Germany, India, Indonesia, the United Kingdom and the U.S. (listed alphabetically). The Company’s other energy-related commercial activities include participating in operations of a mine-mouth coal-fueled generating plant, managing its coal reserve and real estate holdings, evaluating Btu Conversion projects and supporting the development of clean coal technologies.
Newly Adopted Accounting Standards and Accounting Standards Not Yet Implemented	Newly Adopted Accounting Standards
	Presentation of Unrecognized Tax Benefits. In July 2013, the Financial Accounting Standards Board (FASB) issued accounting guidance requiring entities to present unrecognized tax benefits as a reduction to any related deferred tax assets for net operating losses, similar tax losses or tax credit carryforwards if such settlement is required or expected in the event an uncertain tax position is disallowed. Previously effective U.S. GAAP did not provide explicit guidance on the topic. The new presentation guidance became effective for interim and annual periods beginning after December 15, 2013 (January 1, 2014 for the Company). The adoption of the guidance beginning January 1, 2014 had no material effect on the Company's results of operations, financial condition, cash flows or financial statement presentation.
	Accounting Standards Not Yet Implemented
	Going Concern. In August 2014, the FASB issued disclosure guidance that requires management to evaluate, at each annual and interim reporting period, whether substantial doubt exists about an entity's ability to continue as a going concern and, if applicable, to provide related disclosures. As outlined by that guidance, substantial doubt about an entity's ability to continue as a going concern exists when relevant conditions and events, considered in the aggregate, indicate that it is probable that an entity will be unable to meet its obligations as they become due within one year after the date that the financial statements are issued (or are available to be issued). The new guidance will be effective for annual reporting periods ending after December 15, 2016 (the year ending December 31, 2016 for the Company) and interim periods thereafter, with early adoption permitted.
	Revenue Recognition. In May 2014, the FASB issued a comprehensive revenue recognition standard that will supersede nearly all existing revenue recognition guidance under U.S. GAAP. The new standard provides a single principles-based, five-step model to be applied to all contracts with customers, which steps are to (1) identify the contract(s) with the customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract and (5) recognize revenue when each performance obligation is satisfied. More specifically, revenue will be recognized when promised goods or services are transferred to the customer in an amount that reflects the consideration expected in exchange for those goods or services. The standard also requires entities to disclose sufficient qualitative and quantitative information to enable financial statement users to understand the nature, amount, timing and uncertainty of revenues and cash flows arising from contracts with customers. The new guidance will be effective for interim and annual periods beginning after December 15, 2016 (January 1, 2017 for the Company) and the standard allows for either a full retrospective adoption or a modified retrospective adoption. The Company is in the process of evaluating the impact that the adoption of this guidance will have on its results of operations, financial condition, cash flows and financial statement presentation.
	Discontinued Operations. In April 2014, the FASB issued accounting guidance that raised the threshold for disposals to qualify as discontinued operations to a disposal of a component or group of components that is disposed of or is classified as held for sale and represents a strategic shift that has (or will have) a major effect on an entity's operations and financial results. Such a strategic shift may include the disposal of (1) a major geographical area of operations, (2) a major line of business, (3) a major equity method investment or (4) other major parts of an entity. Provided that the major strategic shift criterion is met, the new guidance does allow entities to have significant continuing involvement and continuing cash flows with the discontinued operation, unlike current U.S. GAAP. The new standard also requires additional disclosures for discontinued operations and new disclosures for individually material disposal transactions that do not meet the definition of a discontinued operation. The new guidance will apply prospectively to disposals that occur in interim and annual periods beginning on or after December 31, 2014 (January 1, 2015 for the Company). The impact to the Company's financial statements will depend on any disposal activity that occurs subsequent to adoption in 2015.
Sales and Other Revenues	Sales
	The Company’s revenue from coal sales is realized and earned when risk of loss passes to the customer. Under the typical terms of the Company’s coal supply agreements, title and risk of loss transfer to the customer at the mine or port, where coal is loaded to the transportation source(s) that serves each of the Company’s mines. The Company incurs certain “add-on” taxes and fees on coal sales. Reported coal sales include taxes and fees charged by various federal and state governmental bodies and the freight charged on destination customer contracts.
	Other Revenues
	"Other revenues" include net revenues from coal trading activities as discussed in Note 7. "Coal Trading," as well as coal sales revenues that were derived from the Company’s mining operations and sold through the Company’s coal trading business. Also included are revenues from contract termination or restructuring payments, royalties related to coal lease agreements, sales agency commissions, farm income, property and facility rentals and generation development activities. Royalty income generally results from the lease or sublease of mineral rights to third parties, with payments based upon a percentage of the selling price or an amount per ton of coal produced.
Discontinued Operations and Assets Held for Sale	Discontinued Operations and Assets Held for Sale
	The Company classifies items within discontinued operations in the consolidated financial statements when the operations and cash flows of a particular component of the Company have been (or will be) eliminated from the ongoing operations of the Company as a result of a disposal (by sale or otherwise) and the Company will no longer have any significant continuing involvement in the operation of that component. Refer to Note 3. "Discontinued Operations" for additional details related to discontinued operations.
Cash and Cash Equivalents	Cash and Cash Equivalents
	Cash and cash equivalents are stated at cost, which approximates fair value. Cash equivalents consist of highly liquid investments with original maturities of three months or less.
Inventories	Inventories
	Coal is reported as inventory at the point in time the coal is extracted from the mine. Raw coal represents coal stockpiles that may be sold in current condition or may be further processed prior to shipment to a customer. Saleable coal represents coal stockpiles which require no further processing prior to shipment to a customer.
	Coal inventory is valued at the lower of average cost or market. Coal inventory costs include labor, supplies, equipment (including depreciation thereto) and operating overhead and other related costs incurred at or on behalf of the mining location. Market represents the estimated net realizable value of the inventory, which considers the projected future sales price of the particular coal product, less applicable selling costs, and, in the case of raw coal, estimated remaining processing costs. The valuation of coal inventory is subject to several additional estimates, including those related to ground and aerial surveys used to measure quantities and processing recovery rates.
	Materials and supplies inventory is valued at the lower of average cost or market, less a reserve for obsolete or surplus items. This reserve incorporates several factors, such as anticipated usage, inventory turnover and inventory levels.
Investments in Marketable Securities	Investments in Marketable Securities
	The Company’s short-term investments in marketable securities, which are included in "Other current assets" in the consolidated balance sheets, are defined as those investments with original maturities upon purchase of greater than three months and up to one year. Long-term investments, which are included in "Investments and other assets" in the consolidated balance sheets, are defined as those investments with original maturities upon purchase of greater than one year.
	The Company classifies its investments in debt securities as either held-to-maturity or available-for-sale at the time of purchase and reevaluates such designation periodically. Such investments are classified as held-to-maturity when the Company has the intent and ability to hold the securities to maturity. Investments in debt securities not classified as held-to-maturity and investments in marketable equity securities are classified as available-for-sale. Available-for-sale securities are carried at fair value, with unrealized gains and losses, net of income taxes, generally reported in “Accumulated other comprehensive loss” in the consolidated balance sheets. Realized gains and losses, determined on a specific identification method, are included in “Interest income” in the consolidated statements of operations.
	At each reporting date, the Company performs separate evaluations of its marketable securities to determine if any unrealized losses present are other-than-temporary. Such evaluations involve the consideration of several factors, including, but not limited to, the length of time the market value has been less than cost, the financial condition and near-term prospects of the issuer of the securities and whether the Company has the positive intent and ability to hold the securities until recovery. Refer to Note 2. "Asset Impairment and Mine Closure Costs" and Note 5. "Investments" for details regarding other-than-temporary impairment losses of $4.7 million, $21.5 million and $35.5 million recognized during the years ended December 31, 2014, 2013 and 2012, respectively, related to the Company's marketable equity securities holdings.
Property, Plant, Equipment and Mine Development	Property, Plant, Equipment and Mine Development
	Property, plant, equipment and mine development are recorded at cost. Interest costs applicable to major asset additions are capitalized during the construction period. Capitalized interest in 2014, 2013 and 2012 was immaterial. Expenditures which extend the useful lives of existing plant and equipment assets are capitalized. Maintenance and repairs are charged to operating costs as incurred. Costs incurred to develop coal mines or to expand the capacity of operating mines are capitalized. Costs incurred to maintain current production capacity at a mine are charged to operating costs as incurred. Costs to acquire computer hardware and the development and/or purchase of software for internal use are capitalized and depreciated over the estimated useful lives.
	Coal reserves are recorded at cost, or at fair value in the case of nonmonetary exchanges, of reserves or business acquisitions.
	Depletion of coal reserves and amortization of advance royalties is computed using the units-of-production method utilizing only proven and probable reserves (as adjusted for recoverability factors) in the depletion base. Mine development costs are principally amortized over the estimated lives of the mines using the straight-line method. Depreciation of plant and equipment is computed using the straight-line method over the shorter of the asset's estimated useful life or the life of the mine. The estimated useful lives by category of assets are as follows:


		Years

	Building and improvements	1 to 37
	Machinery and equipment	1 to 37
	Leasehold improvements	Shorter of Useful Life or Remaining Life of Lease
Equity and Cost Method Investments	Equity and Cost Method Investments
	The Company accounts for its investments in less than majority owned corporate joint ventures under either the equity or cost method. The Company applies the equity method to investments in joint ventures when it has the ability to exercise significant influence over the operating and financial policies of the joint venture. Investments accounted for under the equity method are initially recorded at cost and any difference between the cost of the Company’s investment and the underlying equity in the net assets of the joint venture at the investment date is amortized over the lives of the related assets that gave rise to the difference. The Company’s pro-rata share of the operating results of joint ventures and basis difference amortization is reported in the consolidated statements of operations in “Loss from equity affiliates.” Similarly, the Company's pro-rata share of the cumulative foreign currency translation adjustment of its equity method investments whose functional currency is not the U.S. dollar is reported in the consolidated balance sheet as a component of "Accumulated other comprehensive loss," with periodic changes thereto reflected in the consolidated statements of comprehensive income.
	The Company monitors its equity and cost method investments for indicators that a decrease in investment value has occurred that is other than temporary. Examples of such indicators include a sustained history of operating losses and adverse changes in earnings and cash flow outlook. In the absence of quoted market prices for an investment, discounted cash flow projections are used to assess fair value, the underlying assumptions to which are generally considered unobservable Level 3 inputs under the fair value hierarchy. If the fair value of an investment is determined to be below its carrying value and that loss in fair value is deemed other than temporary, an impairment loss is recognized. No such impairment losses were recorded during the year ended December 31, 2014. Refer to Note 2. "Asset Impairment and Mine Closure Costs" and Note 5. "Investments" for details regarding other-than-temporary impairment losses of $43.2 million and $39.4 million recorded during the years ended December 31, 2013 and 2012, respectively, related to certain of the Company's equity and cost method investments.
Asset Retirement Obligations	Asset Retirement Obligations
	The Company’s asset retirement obligation (ARO) liabilities primarily consist of spending estimates for surface land reclamation and support facilities at both surface and underground mines in accordance with applicable reclamation laws in the U.S. and Australia as defined by each mining permit.
	The Company estimates its ARO liabilities for final reclamation and mine closure based upon detailed engineering calculations of the amount and timing of the future cash spending for a third party to perform the required work. Spending estimates are escalated for inflation and then discounted at the credit-adjusted, risk-free rate. The Company records an ARO asset associated with the discounted liability for final reclamation and mine closure. The obligation and corresponding asset are recognized in the period in which the liability is incurred. The ARO asset is amortized on the units-of-production method over its expected life and the ARO liability is accreted to the projected spending date. As changes in estimates occur (such as mine plan revisions, changes in estimated costs or changes in timing of the performance of reclamation activities), the revisions to the obligation and asset are recognized at the appropriate credit-adjusted, risk-free rate. The Company also recognizes an obligation for contemporaneous reclamation liabilities incurred as a result of surface mining. Contemporaneous reclamation consists primarily of grading, topsoil replacement and re-vegetation of backfilled pit areas.
Contingent Liabilities	Contingent Liabilities
	From time to time, the Company is subject to legal and environmental matters related to our continuing and discontinued operations and certain historical, non-coal producing operations. In connection with such matters, the Company is required to assess the likelihood of any adverse judgments or outcomes, as well as potential ranges of probable losses.
	A determination of the amount of reserves required for these matters is made after considerable analysis of each individual issue. The Company accrues for legal and environmental matters within "Operating costs and expenses" when it is probable that a liability has been incurred and the amount of the loss can be reasonably estimated. The Company provides disclosure surrounding loss contingencies when it believes that it is at least reasonably possible that a material loss may be incurred or an exposure to loss in excess of amounts already accrued may exist. Adjustments to contingent liabilities are made when additional information becomes available that affects the amount of estimated loss, which information may include changes in facts and circumstances, changes in interpretations of law in the relevant courts, the results of new or updated environmental remediation cost studies and the ongoing consideration of trends in environmental remediation costs.
	Accrued contingent liabilities exclude claims against third parties and are not discounted. The current portion of these accruals is included in “Accounts payables and accrued expenses” and the long-term portion is included in “Other noncurrent liabilities” in the consolidated balance sheets. In general, legal fees related to environmental remediation and litigation are charged to expense. The Company includes the interest component of any litigation-related penalties within "Interest expense" in the consolidated statements of operations.
Income Taxes	Income Taxes
	Income taxes are accounted for using a balance sheet approach. The Company accounts for deferred income taxes by applying statutory tax rates in effect at the reporting date of the balance sheet to differences between the book and tax basis of assets and liabilities. A valuation allowance is established if it is “more likely than not” that the related tax benefits will not be realized. Significant weight is given to evidence that can be objectively verified including history of tax attribute expiration and cumulative income or loss. In determining the appropriate valuation allowance, the Company considers the projected realization of tax benefits based on expected levels of future taxable income, available tax planning strategies, reversals of existing taxable temporary differences and taxable income in carryback years.
	The Company recognizes the tax benefit from uncertain tax positions only if it is “more likely than not” the tax position will be sustained on examination by the taxing authorities based on the technical merits of the position. The tax benefits recognized from such a position are measured based on the largest benefit that has a greater than fifty percent likelihood of being realized upon ultimate settlement. To the extent the Company’s assessment of such tax positions changes, the change in estimate will be recorded in the period in which the determination is made. Tax-related interest and penalties are classified as a component of income tax expense.
Postretirement Health Care and Life Insurance Benefits and Pension Plans	Postretirement Health Care and Life Insurance Benefits
	The Company accounts for postretirement benefits other than pensions by accruing the costs of benefits to be provided over the employees’ period of active service. These costs are determined on an actuarial basis. The Company’s consolidated balance sheets reflect the accumulated postretirement benefit obligations of its postretirement benefit plans. The Company accounts for changes in its postretirement benefit obligations as a settlement when an irrevocable action has been effected that relieves the Company of its actuarially-determined liability to individual plan participants and removes substantial risk surrounding the nature, amount and timing of the obligation’s funding and the assets used to effect the settlement. See Note 15. "Postretirement Health Care and Life Insurance Benefits" for information related to postretirement benefits.
	Pension Plans
	The Company sponsors non-contributory defined benefit pension plans accounted for by accruing the cost to provide the benefits over the employees’ period of active service. These costs are determined on an actuarial basis. The Company’s consolidated balance sheets reflect the funded status of the defined benefit pension plans. See Note 16. "Pension and Savings Plans" for information related to pension plans.
Restructuring Activities	Restructuring Activities
	From time to time, the Company initiates restructuring activities in connection with its repositioning efforts to appropriately align its cost structure or optimize its coal production relative to prevailing global coal industry conditions. Costs associated with restructuring actions can include early mine closures, voluntary and involuntary workforce reductions, office closures and other related activities. Costs associated with restructuring activities are recognized in the period incurred.
	Included as a component of "Restructuring and pension settlement charges" in the the Company's consolidated statements of operations for the years ended December 31, 2014 and 2013 were aggregate restructuring charges of $15.7 million and $11.9 million, respectively, primarily associated with voluntary and involuntary workforce reductions. The majority of the cash expenditures associated with the charges recognized in 2014 are expected to be paid in the first quarter of 2015.
	In 2013, the Company ceased production and commenced with the early closure of the Wilkie Creek Mine in the Surat Basin in Queensland, Australia. In 2012, we initiated two early mine closures in the U.S.: the Air Quality Mine in Indiana and Willow Lake Mine in Illinois. See Note 2. "Asset Impairment and Mine Closure Costs" and Note 3. "Discontinued Operations" for information related to those early mine closures. No mines were closed in advance of the anticipated exhaustion of reserves in 2014.
Derivatives	Derivatives
	The Company recognizes at fair value all contracts meeting the definition of a derivative as assets or liabilities in the consolidated balance sheets, with the exception of certain coal trading contracts for which the Company has elected to apply a normal purchases and normal sales exception.
	With respect to derivatives used in hedging activities, the Company assesses, both at inception and at least quarterly thereafter, whether such derivatives are highly effective at offsetting the changes in the anticipated exposure of the hedged item. The effective portion of the change in the fair value of derivatives designated as a cash flow hedge is recorded in “Accumulated other comprehensive loss” until the hedged transaction impacts reported earnings, at which time any gain or loss is reclassified to earnings. To the extent that periodic changes in the fair value of derivatives deemed highly effective exceeds such changes in the hedged item, the ineffective portion of the periodic non-cash changes are recorded in earnings in the period of the change. If the hedge ceases to qualify for hedge accounting, the Company prospectively recognizes changes in the fair value of the instrument in earnings in the period of the change. The potential for hedge ineffectiveness is present in the design of certain of the Company’s cash flow hedge relationships and is discussed in detail in Note 6. "Derivatives and Fair Value Measurements" and Note 7. "Coal Trading." Gains or losses from derivative financial instruments designated as fair value hedges are recognized immediately in earnings, along with the offsetting gain or loss related to the underlying hedged item.
	The Company’s asset and liability derivative positions are offset on a counterparty-by-counterparty basis if the contractual agreement provides for the net settlement of contracts with the counterparty in the event of default or termination of any one contract.
	Non-derivative contracts and derivative contracts for which the Company has elected to apply the normal purchases and normal sales exception are accounted for on an accrual basis.
Business Combinations	Business Combinations
	The Company accounts for business combinations using the purchase method of accounting. The purchase method requires the Company to determine the fair value of all acquired assets, including identifiable intangible assets and all assumed liabilities. The total cost of acquisitions is allocated to the underlying identifiable net assets, based on their respective estimated fair values. Determining the fair value of assets acquired and liabilities assumed requires management's judgment and the utilization of independent valuation experts, and often involves the use of significant estimates and assumptions, including assumptions with respect to future cash inflows and outflows, discount rates and asset lives, among other items.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets
	The Company evaluates its long-lived assets held and used in operations for impairment as events and changes in circumstances indicate that the carrying amount of such assets might not be recoverable. Factors that would indicate potential impairment to be present include, but are not limited to, a sustained history of operating or cash flow losses, an unfavorable change in earnings and cash flow outlook, prolonged adverse industry or economic trends and a significant adverse change in the extent or manner in which a long-lived asset is being used or in its physical condition. The Company generally does not view short-term declines in thermal and metallurgical coal prices in the markets in which it sells those products as a triggering event for conducting impairment tests because such markets have a history of price volatility. However, the Company generally does view a sustained trend of depressed coal market pricing (for example, over periods exceeding one year) as an indicator of potential impairment.
	Assets are grouped at the lowest level for which there are identifiable cash flows that are largely independent of the cash flows of other groups of assets. For its active mining operations, the Company generally groups such assets at the mine level, or the mining complex level for mines that share infrastructure, with the exception of impairment evaluations triggered by mine closures. In those cases involving mine closures, the related assets are evaluated at the individual asset level for remaining economic life based on transferability to ongoing operating sites and for use in reclamation-related activities, or for expected salvage. For its development and exploration properties and portfolio of surface land and coal reserve holdings, the Company considers several factors to determine whether to evaluate those assets individually or on a grouped basis for purposes of impairment testing. Such factors include geographic proximity to one another, the expectation of shared infrastructure upon development based on future mining plans and whether it would be most advantageous to bundle such assets in the event of sale to a third party.
	When indicators of impairment are present, the Company evaluates its long-lived assets for recoverability by comparing the estimated undiscounted cash flows expected to be generated by those assets under various assumptions to their carrying amounts. If such undiscounted cash flows indicate that the carrying value of the asset group is not recoverable, impairment losses are measured by comparing the estimated fair value of the asset group to its carrying amount. As quoted market prices are unavailable for the Company's individual mining operations, fair value is determined through the use of an expected present value technique based on the income approach, except for non-strategic coal reserves, surface lands and undeveloped coal properties excluded from the Company's long-range mine planning. In those cases, a market approach is utilized based on the most comparable market multiples available. The estimated future cash flows and underlying assumptions used to assess recoverability and, if necessary, measure the fair value of the Company's long-lived mining assets are derived from those developed in connection with the Company's planning and budgeting process. The Company believes its assumptions to be consistent with those a market participant would use for valuation purposes. The most critical assumptions underlying the Company's projections and fair value estimates include those surrounding future tons sold, coal prices for unpriced coal, production costs (including costs for labor, commodity supplies and contractors), transportation costs, foreign currency exchange rates and a risk-adjusted, after-tax cost of capital (all of which generally constitute unobservable Level 3 inputs under the fair value hierarchy), in addition to market multiples for non-strategic coal reserves, surface lands and undeveloped coal properties excluded from the Company's long-range mine planning (which generally constitute Level 2 inputs under the fair value hierarchy).
	Refer to Note 2. "Asset Impairment and Mine Closure Costs" for details regarding impairment charges related to long-lived assets of $149.7 million, $463.6 million and $833.6 million recognized during the years ended December 31, 2014, 2013 and 2012, respectively.
Fair Value	Fair Value
	For assets and liabilities that are recognized or disclosed at fair value in the consolidated financial statements, the Company defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date.
Foreign Currency	Foreign Currency
	Functional currency is determined by the primary economic environment in which an entity operates, which for the Company's foreign operations is generally the U.S. dollar because sales prices in international coal markets and the Company's sources of financing those operations is denominated in that currency. Accordingly, substantially all of the Company’s consolidated foreign subsidiaries utilize the U.S. dollar as their functional currency. Monetary assets and liabilities are remeasured at year-end exchange rates while non-monetary items are remeasured at historical rates. Income and expense accounts are remeasured at the average rates in effect during the year, except for those expenses related to balance sheet amounts that are remeasured at historical exchange rates. Gains and losses from foreign currency remeasurement related to tax balances are included as a component of "Income tax (benefit) provision," while all other remeasurement gains and losses are included in "Operating costs and expenses." The total impact of foreign currency remeasurement on the consolidated statements of operations was a net loss of $1.3 million for the year ended December 31, 2014 and a net gain of $34.1 million and $4.8 million for the years ended December 31, 2013 and 2012, respectively.
	The Company owns a 50% equity interest Middlemount Coal Pty Ltd. (Middlemount), which owns the Middlemount Mine in Queensland, Australia. Middlemount utilizes the Australian dollar as its functional currency. Accordingly, the assets and liabilities of that equity investee are translated to U.S. dollars at the year-end exchange rate and income and expense accounts are translated at the average rate in effect during the year. The Company's pro-rata share of the translation gains and losses of the equity investee are recorded as a component of "Accumulated other comprehensive loss." Australian dollar denominated shareholder loans to the Middlemount Mine, which are long term in nature, are considered part of the Company's net investment in that operation. Accordingly, foreign currency gains or losses on those loans are recorded as a component of foreign currency translation adjustment. The Company recorded foreign currency translation losses of $41.0 million and $92.7 million for the years ended December 31, 2014 and 2013, respectively, and a translation gain of $19.1 million for the year ended December 31, 2012.
Share-Based Compensation	Share-Based Compensation
	The Company accounts for share-based compensation at the grant date fair value of awards and recognizes the related expense over the service period of the awards. See Note 18. "Share-Based Compensation" for information related to share-based compensation.
Exploration and Drilling Costs	Exploration and Drilling Costs
	Exploration expenditures are charged to operating costs as incurred, including costs related to drilling and study costs incurred to convert or upgrade mineral resources to reserves.
Advance Stripping Costs	Advance Stripping Costs
	Pre-production. At existing surface operations, additional pits may be added to increase production capacity in order to meet customer requirements. These expansions may require significant capital to purchase additional equipment, expand the workforce, build or improve existing haul roads and create the initial pre-production box cut to remove overburden (that is, advance stripping costs) for new pits at existing operations. If these pits operate in a separate and distinct area of the mine, the costs associated with initially uncovering coal (that is, advance stripping costs incurred for the initial box cuts) for production are capitalized and amortized over the life of the developed pit consistent with coal industry practices.
	Post-production. Advance stripping costs related to post-production are expensed as incurred. Where new pits are routinely developed as part of a contiguous mining sequence, the Company expenses such costs as incurred. The development of a contiguous pit typically reflects the planned progression of an existing pit, thus maintaining production levels from the same mining area utilizing the same employee group and equipment.
Use of Estimates in the Preparation of the Consolidated Financial Statements	Use of Estimates in the Preparation of the Consolidated Financial Statements
	The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Derivatives_and_Fair_Value_Mea1

Derivatives and Fair Value Measurements Fair value transfer timing policy (Policies)	12 Months Ended
	Dec. 31, 2014
Fair value transfer policy [Abstract]
Fair value transfer policy [Policy Text Block]	The Company’s policy is to value all transfers between levels using the beginning of period valuation.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies Discussion (Tables)	12 Months Ended
	Dec. 31, 2014
Estimated Useful Life of Property, Plant, Equipment and Mine Development [Line Items]
Estimated useful life of plant and equipment	The estimated useful lives by category of assets are as follows:


		Years

	Building and improvements	1 to 37
	Machinery and equipment	1 to 37
	Leasehold improvements	Shorter of Useful Life or Remaining Life of Lease

Asset_Impairment_and_Mine_Clos1

Asset Impairment and Mine Closure Costs (Tables)	12 Months Ended
	Dec. 31, 2014
Asset Impairment and Mine Closure Costs [Abstract]
Details of Impairment of Long-Lived Assets Held and Used by Asset [Table Text Block]	The following costs are reflected in "Asset impairment and mine closure costs" in the consolidated statement of operations for the year ended December 31, 2014:


		Reportable Segment
		Australian		Western		Corporate		Consolidated
		Mining		U.S. Mining		and Other
		(Dollars in millions)
	Asset impairment charges:
	Long-lived assets	$	78.6	$	2.7	$	68.4	$	149.7

	Marketable securities	—		—		4.7		4.7

	Total	$	78.6	$	2.7	$	73.1	$	154.4

	The following costs are reflected in "Asset impairment and mine closure costs" in the consolidated statement of operations for the year ended December 31, 2012:


		Reportable Segment
		Australian		Western		Midwestern		Corporate		Consolidated
		Mining		U.S. Mining		U.S. Mining		and Other
		(Dollars in millions)
	Charges related to mine closures:
	Impairment of long-lived assets	$	—	$	—	$	26.9	$	—	$	26.9

	Acceleration of asset retirement obligations	—		—		7.1		—		7.1

	Employee termination benefits	—		—		6.7		—		6.7

	Other	—		—		4.3		—		4.3

	Other asset impairment charges:

	Long-lived assets	806.7		—		—		—		806.7

	Marketable securities	—		—		—		35.5		35.5

	Cost method investments	—		—		—		39.4		39.4

	Other	—		2.4		—		—		2.4

	Total	$	806.7	$	2.4	$	45	$	74.9	$	929

	The following costs are reflected in "Asset impairment and mine closure costs" in the consolidated statement of operations for the year ended December 31, 2013:


		Reportable Segment
		Australian		Corporate		Consolidated
		Mining		and Other
		(Dollars in millions)
	Asset impairment charges:
	Long-lived assets	$	390.8	$	72.8	$	463.6

	Equity method investment	—		43.2		43.2

	Marketable securities	—		21.5		21.5

	Total	$	390.8	$	137.5	$	528.3

Discontinued_Operations_Tables

Discontinued Operations Tables (Tables)	12 Months Ended
	Dec. 31, 2014
Discontinued Operations and Disposal Groups [Abstract]
Results of discontinued operations [Table Text Block]	Results from discontinued operations were as follows during the years ended December 31, 2014, 2013 and 2012:


		Year Ended December 31,
		2014			2013			2012
		(Dollars in millions)
	Loss from discontinued operations before income taxes	$	(23.8	)	$	(329.7	)	$	(163.9	)
	Income tax (provision) benefit	(4.4		)	103.1			59.7

	Loss from discontinued operations, net of income taxes	$	(28.2	)	$	(226.6	)	$	(104.2	)
Restructuring and Related Costs [Table Text Block]	The following table summarizes the changes in those liabilities for the year ended December 31, 2014:


		Contractual Liabilities			Other Exit Costs			Total
		(Dollars in millions)
	Liability balance at December 31, 2013	$	33.9		$	2.7		$	36.6

	Change in estimate	(5.0		)	(0.2		)	(5.2		)
	Cash payments	(28.4		)	(2.5		)	(30.9		)
	Foreign currency loss	0.3			—			0.3

	Liability balance at December 31, 2014	$	0.8		$	—		$	0.8

Schedule of Disposal Groups, Including Discontinued Operations, Income Statement, Balance Sheet and Additional Disclosures [Table Text Block]	Assets and liabilities classified as discontinued operations included in the Company's consolidated balance sheets were as follows:


		December 31,
		2014			2013
		(Dollars in millions)
	Assets:
	Other current assets	$	0.3		$	38.6

	Investments and other assets	16.3			47.4

	Total assets classified as discontinued operations	$	16.6		$	86


	Liabilities:
	Accounts payable and accrued expenses	$	12.5		$	133.1

	Other noncurrent liabilities	109.8			84.9

	Total liabilities classified as discontinued operations	$	122.3		$	218

Inventories_Tables

Inventories (Tables)	12 Months Ended
	Dec. 31, 2014
Inventory Disclosure [Abstract]
Inventories	Inventories as of December 31, 2014 and December 31, 2013 consisted of the following:


		December 31,
		2014		2013
		(Dollars in millions)
	Materials and supplies	$	143.6	$	166.8

	Raw coal	115		122.6

	Saleable coal	147.9		217.3

	Total	$	406.5	$	506.7

Investments_Tables

Investments (Tables)	12 Months Ended
	Dec. 31, 2014															Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]
Investments in available-for-sale securities	Investments in available-for-sale securities at December 31, 2014 were as follows:															Investments in available-for-sale securities at December 31, 2013 were as follows:


	Available-for-sale securities		Amortized Cost			Gross			Gross			Fair Value				Available-for-sale securities	Amortized Cost		Gross		Gross			Fair Value
						Unrealized			Unrealized										Unrealized		Unrealized
						Gains			Losses										Gains		Losses
			(Dollars in millions)																(Dollars in millions)
	Current:															Current:
	U.S. corporate bonds		$	11.2		$	—		$	—		$	11.2			Federal government securities	$	2.8	$	—	$	—		$	2.8

	Noncurrent:															U.S. corporate bonds	2.4		—		—			2.4
	Marketable equity securities		6.2			—			—			6.2
																Noncurrent:
	Federal government securities		32			—			—			32				Marketable equity securities	10.9		1.3		—			12.2

	U.S. corporate bonds		12.4			—			—			12.4				Federal government securities	28.8		—		(0.1		)	28.7

	Total		$	61.8		$	—		$	—		$	61.8			U.S. corporate bonds	20.8		0.1		—			20.9

																Total	$	65.7	$	1.4	$	(0.1	)	$	67

Contractual maturities for available for sale investment in debt securities	Contractual maturities for available-for-sale investments in debt securities at December 31, 2014 were as shown below. Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.


	Contractual maturities for available-for-sale securities		Cost			Fair Value
			(Dollars in millions)
	Due in one year or less		$	11.2		$	11.2

	Due in one to five years		44.4			44.4

	Total		$	55.6		$	55.6

Equity Method Investments [Table Text Block]	The table below summarizes the book value of those investments, which is reported in “Investments and other assets” in the consolidated balance sheets, and the related loss from equity affiliates:


		Book Value at December 31,						Loss from Equity
								Affiliates for the Year Ended
								December 31,
		2014			2013			2014			2013			2012
		(Dollars in millions)
	Equity interest in Middlemount Coal Pty Ltd	$	58		$	173.4		$	98.5		$	33.5		$	52.1

	Other equity method investments	7.3			6.7			9.1			6.7			9.1

	Total equity method investments	$	65.3		$	180.1		$	107.6		$	40.2		$	61.2

Derivatives_and_Fair_Value_Mea2

Derivatives and Fair Value Measurements (Tables) (Non Coal Trading [Member])	12 Months Ended
	Dec. 31, 2014
Non Coal Trading [Member]
Derivative [Line Items]
Company's foreign currency and commodity positions	Notional Amounts and Fair Value. The following summarizes the Company’s foreign currency and commodity positions at December 31, 2014:


		Notional Amount by Year of Maturity
		Total				2015				2016				2017
	Foreign Currency

	A$:US$ hedge contracts (A$ millions)	$	3,191.10			$	1,661.10			$	1,007.00			$	523

	Commodity Contracts

	Diesel fuel hedge contracts (million gallons)	201.5				103.4				67.5				30.6



		Instrument Classification by
		Cash				Fair				Economic					Fair Value
		Flow				Value				Hedge					of Net Liability
		Hedge				Hedge
															(Dollars in millions)
	Foreign Currency

	A$:US$ hedge contracts (A$ millions)	$	3,191.10			$	—			$	—				$	(410.0	)

	Commodity Contracts

	Diesel fuel hedge contracts (million gallons)	201.5				—				—					(167.1		)

Classification and amounts of pre-tax gains and losses related to the Company's non-trading hedges	The tables below show the classification and amounts of pre-tax gains and losses related to the Company’s non-coal trading hedges during the years ended December 31, 2014, 2013 and 2012:


					Year Ended December 31, 2014
			Income Statement Classification		Loss				Loss				Loss
			Losses - Realized		recognized in				reclassified				reclassified
					other				from other				from other
					comprehensive				comprehensive				comprehensive
					income on				income into				income into
					derivative				income (effective				income
					(effective portion)				portion) (1)				(ineffective
	Financial Instrument												portion)
					(Dollars in millions)
	Commodity swap contracts		Operating costs and expenses		$	(194.5	)		$	(20.6	)		$	(1.7	)
	Foreign currency forward contracts		Operating costs and expenses		(100.9		)		(27.3		)		—

	Total				$	(295.4	)		$	(47.9	)		$	(1.7	)

	(1)	Includes the reclassification from "Accumulated other comprehensive loss" into earnings of $136.9 million of previously unrecognized gains on foreign currency cash flow hedge contracts monetized in the fourth quarter of 2012.


					Year Ended December 31, 2013
			Income Statement Classification		Gain (loss)				Gain				Loss
			Gains (Losses) - Realized		recognized in				reclassified				reclassified
					other				from other				from other
					comprehensive				comprehensive				comprehensive
					income on				income into				income into
					derivative				income				income
					(effective portion)				(effective				(ineffective
	Financial Instrument								portion)				portion)
					(Dollars in millions)
	Commodity swap contracts		Operating costs and expenses		$	12.5			$	11.9			$	(0.5	)

	Foreign currency forward contracts		Operating costs and expenses		(597.8		)		162.4				—

	Total				$	(585.3	)		$	174.3			$	(0.5	)



					Year Ended December 31, 2012
			Income Statement Classification		Gain				Gain				Loss
			Gains (Losses) - Realized		recognized in				reclassified				reclassified
					other				from other				from other
					comprehensive				comprehensive				comprehensive
					income on				income into				income into
					derivative				income				income
					(effective portion)				(effective				(ineffective
	Financial Instrument								portion)				portion)
					(Dollars in millions)
	Commodity swap contracts		Operating costs and expenses		$	14.5			$	48.3			$	(4.7	)

	Foreign currency forward contracts		Operating costs and expenses		148				351.7				—

	Total				$	162.5			$	400			$	(4.7	)

Classification and amount of non-coal trading derivatives, gross and net basis	The classification and amount of non-coal trading derivative financial instruments presented on a gross and net basis as of December 31, 2014 and 2013 are presented in the tables that follow.



			Fair Value of Liabilities Presented in the Consolidated Balance Sheet as of December 31, 2014 (1)
	Financial Instrument

	Current Liabilities:
	Commodity swap contracts		$	100.1

	Foreign currency forward contracts		241

	Total		$	341.1


	Noncurrent Liabilities:
	Commodity swap contracts		$	67

	Foreign currency forward contracts		169

	Total		$	236


	(1)	All commodity swap contracts and foreign currency forward contracts were in a liability position as of December 31, 2014.



			Fair Value of Assets as of December 31, 2013
			Gross Amounts Recognized				Gross Amounts Offset in the Consolidated Balance Sheet				Net Amounts Presented in the Consolidated Balance Sheet				Derivatives Not Offset in the Consolidated Balance Sheet (1)				Net Amount
	Financial Instrument
			(Dollars in millions)
	Current Assets:
	Commodity swap contracts		$	8.7			$	(2.3	)		$	6.4			n.a.				n.a.

	Foreign currency forward contracts		—				—				—				n.a.				n.a.

	Total		$	8.7			$	(2.3	)		$	6.4			$	(5.0	)		$	1.4


	Noncurrent Assets:
	Commodity swap contracts		$	2.8			$	(0.9	)		$	1.9			n.a.				n.a.

	Foreign currency forward contracts		0.2				(0.2		)		—				n.a.				n.a.

	Total		$	3			$	(1.1	)		$	1.9			$	(1.3	)		$	0.6


	-1	Adjustments relate to the further netting of derivative contracts with a common counterparty across the Company's foreign currency, diesel fuel and explosives hedging strategy derivative contract portfolios that would be contractually enforceable in the event of default.


			Fair Value of Liabilities as of December 31, 2013
			Gross Amounts Recognized				Gross Amounts Offset in the Consolidated Balance Sheet				Net Amounts Presented in the Consolidated Balance Sheet				Derivatives Not Offset in the Consolidated Balance Sheet (1)				Net Amount
	Financial Instrument
			(Dollars in millions)
	Current Liabilities:
	Commodity swap contracts		$	3.9			$	(1.9	)		$	2			n.a.				n.a.

	Foreign currency forward contracts		211.9				—				211.9				n.a.				n.a.

	Total		$	215.8			$	(1.9	)		$	213.9			$	(5.4	)		$	208.5


	Noncurrent Liabilities:
	Commodity swap contracts		$	2.5			$	(1.3	)		$	1.2			n.a.				n.a.

Foreign currency forward contracts		261.6				(0.2		)		261.4				n.a.				n.a.

Total		$	264.1			$	(1.5	)		$	262.6			$	(0.9	)		$	261.7


-1	Adjustments relate to the further netting of derivative contracts with a common counterparty across the Company's foreign currency, diesel fuel and explosives hedging strategy derivative contract portfolios that would be contractually enforceable in the event of default.
Fair value measured on recurring basis of net financial assets and liabilities	Financial Instruments Measured on a Recurring Basis. The following tables set forth the hierarchy of the Company’s net financial asset (liability) positions for which fair value is measured on a recurring basis:


		December 31, 2014
		Level 1				Level 2				Level 3				Total
						(Dollars in millions)
	Investments in debt and equity securities	$	26.1			$	35.7			$	—			$	61.8

	Commodity swap contracts	—				(167.1		)		—				(167.1		)

	Foreign currency forward contracts	—				(410.0		)		—				(410.0		)

	Total net financial assets (liabilities)	$	26.1			$	(541.4	)		$	—			$	(515.3	)



		December 31, 2013
		Level 1				Level 2				Level 3				Total
						(Dollars in millions)
	Investments in debt and equity securities	$	28.8			$	38.2			$	—			$	67

	Commodity swap contracts	—				5.1				—				5.1

	Foreign currency forward contracts	—				(473.3		)		—				(473.3		)

	Total net financial assets (liabilities)	$	28.8			$	(430.0	)		$	—			$	(401.2	)

Carrying amounts and estimated fair values of the Company's debt	The carrying amounts and estimated fair values of the Company’s long-term debt are summarized as follows:


		December 31, 2014								December 31, 2013
		Carrying				Estimated				Carrying				Estimated
		Amount				Fair Value				Amount				Fair Value
						(Dollars in millions)
	Long-term debt	$	5,986.80			$	5,227.90			$	6,002.40			$	6,167.50

Coal_Trading_Tables

Coal Trading (Tables) (Coal Trading [Member])	12 Months Ended
	Dec. 31, 2014
Coal Trading [Member]
Coal Trading [Line Items]
Trading revenue by type of instrument	Trading revenues recognized during the years ended December 31, 2014, 2013 and 2012 were as follows:


			Year Ended December 31,
	Trading Revenue by Type of Instrument		2014				2013				2012
			(Dollars in millions)
	Commodity futures, swaps and options		$	92.3			$	183.9			$	159.9

	Physical commodity purchase/sale contracts		(33.9		)		(117.9		)		(8.1		)
	Total trading revenue		$	58.4			$	66			$	151.8

Fair value of assets and liabilities from coal trading activities and related balance sheet offsetting disclosures	The fair value of assets and liabilities from coal trading activities presented on a gross and net basis as of December 31, 2014 and 2013 is set forth below:


	Affected line item in the consolidated balance sheets		Gross Amounts of Recognized Assets (Liabilities)				Gross Amounts Offset in the Consolidated Balance Sheets				Variation margin (held) posted (1)				Net Amounts of Assets (Liabilities) Presented in the Consolidated Balance Sheets
			(Dollars in millions)
			Fair Value as of December 31, 2014
	Assets from coal trading activities, net		$	342.5			$	(248.3	)		$	(36.6	)		$	57.6

	Liabilities from coal trading activities, net		(285.0		)		248.3				4				(32.7		)

	Total, Net		$	57.5			$	—			$	(32.6	)		$	24.9


			Fair Value as of December 31, 2013
	Assets from coal trading activities, net		$	418.8			$	(324.7	)		$	(58.0	)		$	36.1

	Liabilities from coal trading activities, net		(332.7		)		324.7				1.9				(6.1		)

	Total, Net		$	86.1			$	—			$	(56.1	)		$	30


	(1)	None and $42 million of the net variation margin held at December 31, 2014 and 2013, respectively, related to cash flow hedges.
Fair value coal trading net assets (liabilities) measured on recurring basis	The following tables set forth the hierarchy of the Company’s net financial asset (liability) coal trading positions for which fair value is measured on a recurring basis as of December 31, 2014 and 2013:


		December 31, 2014
		Level 1				Level 2				Level 3				Total
		(Dollars in millions)
	Commodity futures, swaps and options	$	(0.2	)		$	32.6			$	—			$	32.4

	Physical commodity purchase/sale contracts	—				(9.6		)		2.1				(7.5		)

	Total net financial (liabilities) assets	$	(0.2	)		$	23			$	2.1			$	24.9



		December 31, 2013
		Level 1				Level 2				Level 3				Total
						(Dollars in millions)
	Commodity futures, swaps and options	$	—			$	26.4			$	—			$	26.4

	Physical commodity purchase/sale contracts	—				1.5				2.1				3.6

	Total net financial assets	$	—			$	27.9			$	2.1			$	30

Schedule of quantitative unobservable inputs, physical commodity purchase/sale contracts	The following table summarizes the quantitative unobservable inputs utilized in the Company's internally-developed valuation models for physical commodity purchase/sale contracts classified as Level 3 as of December 31, 2014:


			Range						Weighted
	Input		Low			High			Average
	Quality adjustments		8	%		12	%		9	%
	Location differentials		19	%		19	%		19	%
Change in the Company's recurring Level 3 net financial assets	The following table summarizes the changes in the Company’s recurring Level 3 net financial assets:


		Year Ended December 31,
		2014				2013				2012
		(Dollars in millions)
	Beginning of year	$	2.1			$	5.2			$	8.7

	Total gains realized/unrealized:

	Included in earnings	6.7				0.3				17.5

	Settlements	(6.7		)		(3.4		)		(21.0		)
	End of year	$	2.1			$	2.1			$	5.2

Changes in unrealized gains (losses) relating to Level 3 net financial assets	The following table summarizes the changes in net unrealized gains (losses) relating to Level 3 net financial assets held both as of the beginning and the end of the period:


		Year Ended December 31,
		2014				2013				2012
		(Dollars in millions)
	Changes in unrealized gains (losses) (1)	$	2.1			$	(0.4	)		$	4.1


	(1)	Within the consolidated statements of operations and consolidated statements of comprehensive income for the periods presented, unrealized gains and losses from Level 3 items are combined with unrealized gains and losses on positions classified in Level 1 or 2, as well as other positions that have been realized during the applicable periods.
Schedule of future realization of the Company's trading portfolio	As of December 31, 2014, the timing of the estimated future realization of the value of the Company’s trading portfolio was as follows:


			Percentage of
	Year of Expiration		Portfolio Total

	2015		77	%
	2016		19	%
	2017		3	%
	2018		1	%
			100	%

Financing_Receivables_Financin

Financing Receivables Financing Receivables (Tables)	12 Months Ended
	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block]	The Company's total financing receivables as of December 31, 2014 and 2013 consisted of the following:


	Balance Sheet Classification	December 31, 2014		December 31, 2013
		(Dollars in millions)
	Accounts receivable, net	$	—	$	0.1

	Investments and other assets	347.2		351.7

	Total financing receivables	$	347.2	$	351.8

Property_Plant_Equipment_and_M1

Property, Plant, Equipment and Mine Development (Tables)	12 Months Ended
	Dec. 31, 2014
Property, Plant, Equipment and Mine Development [Abstract]
Property, Plant and Equipment [Table Text Block]	Property, plant, equipment and mine development, net, as of December 31, 2014 and December 31, 2013 consisted of the following:


		December 31,
		2014			2013
		(Dollars in millions)
	Land and coal interests	$	11,021.10		$	11,024.10

	Buildings and improvements	1,569.10			1,525.40

	Machinery and equipment	2,685.70			2,777.50

	Less: Accumulated depreciation, depletion and amortization	(4,698.6		)	(4,244.5		)
	Total, net	$	10,577.30		$	11,082.50

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Loss from continuing operations before income taxes	Loss from continuing operations before income taxes for the years ended December 31, 2014, 2013 and 2012 consisted of the following:


		Year Ended December 31,
		2014			2013			2012
		(Dollars in millions)
	U.S.	$	268.9		$	220.6		$	1,049.10

	Non-U.S.	(816.8		)	(954.9		)	(1,257.7		)
	Total	$	(547.9	)	$	(734.3	)	$	(208.6	)
Components of income tax provision (benefit)	Total income tax provision (benefit) for the years ended December 31, 2014, 2013 and 2012 consisted of the following:


		Year Ended December 31,
		2014			2013			2012
		(Dollars in millions)
	Current:

	U.S. federal	$	27.1		$	(47.9	)	$	116.8

	Non-U.S.	(61.1		)	38.4			127.6

	State	3.3			(4.7		)	12.2

	Total current	(30.7		)	(14.2		)	256.6

	Deferred:

	U.S. federal	111			4.8			(32.7		)

	Non-U.S.	122.3			(440.3		)	28.8

	State	(1.4		)	1.4			9.6

	Total deferred	231.9			(434.1		)	5.7

	Total income tax provision (benefit)	$	201.2		$	(448.3	)	$	262.3

Reconciliation of the expected statutory federal income tax provision (benefit) to the Company's actual income tax provision	The following is a reconciliation of the expected statutory federal income tax benefit to the Company’s income tax provision (benefit) for the years ended December 31, 2014, 2013 and 2012:


		Year Ended December 31,
		2014			2013			2012
		(Dollars in millions)
	Expected income tax benefit at U.S. federal statutory rate	$	(191.7	)	$	(257.0	)	$	(73.0	)
	Changes in valuation allowance, income tax	569.4			(29.4		)	521.5

	Changes in tax reserves	(81.5		)	8.8			24.5

	Excess depletion	(65.3		)	(72.7		)	(69.4		)
	Foreign earnings repatriation	(71.4		)	—			—

	Foreign earnings provision differential	28.8			62.7			(59.6		)

	General business tax credits	(19.2		)	(18.9		)	(17.4		)
	Minerals resource rent tax, net of federal tax	16.1			(87.4		)	77.2

	Remeasurement of foreign income tax accounts	(2.7		)	(44.3		)	7.9

	State income taxes, net of federal tax benefit	(2.3		)	(0.2		)	(1.1		)
	Capital loss	—			—			(118.1		)

	Other, net	21			(9.9		)	(30.2		)

	Total income tax provision (benefit)	$	201.2		$	(448.3	)	$	262.3

Tax effects of temporary differences that give rise to significant portions of the deferred tax assets and liabilities	The tax effects of temporary differences that gave rise to significant portions of the deferred tax assets and liabilities as of December 31, 2014 and 2013 consisted of the following:


		December 31,
		2014			2013
		(Dollars in millions)
	Deferred tax assets:

	Tax credits and loss carryforwards	$	1,723.50		$	1,558.00

	Minerals resource rent tax	—			993.2

	Accrued postretirement benefit obligations	372.3			309.9

	Asset retirement obligations	167			141.6

	Employee benefits	70.7			88.5

	Payable to voluntary employee beneficiary association for certain Patriot retirees (1)	79.2			84.4

	Hedge activities	44.2			—

	Environmental contingencies	29.9			23.6

	Deferred revenue	29.1			3.2

	Financial guarantees	16.9			16.9

	Workers’ compensation obligations	6.2			10.4

	Other	50.5			31.5

	Total gross deferred tax assets	2,589.50			3,261.20

	Deferred tax liabilities:

	Property, plant, equipment and mine development, principally due to differences in depreciation, depletion and asset impairments	1,223.40			1,322.30

	Unamortized discount on Convertible Junior Subordinated Debentures	131			131.8

	Hedge activities	—			11.4

	Investments and other assets	73.4			82

	Other	1.1			46.3

	Total gross deferred tax liabilities	1,428.90			1,593.80

	Valuation allowance, income tax	(1,169.0		)	(656.4		)
	Valuation allowance, minerals resource rent tax	—			(977.7		)

	Net deferred tax (liability) asset	$	(8.4	)	$	33.3

	Deferred taxes are classified as follows:

	Current deferred income taxes	$	80		$	66.4

	Noncurrent deferred income taxes	(88.4		)	(33.1		)
	Net deferred tax (liability) asset	$	(8.4	)	$	33.3


	(1)	Refer to Note 25. "Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation" herein for additional details related to this transaction.
Summary of Income Tax Contingencies [Table Text Block]	Net unrecognized tax benefits (excluding interest and penalties) were recorded as follows in the consolidated balance sheets as of December 31, 2014 and 2013:


		December 31,
		2014			2013
		(Dollars in millions)
	Accounts payable and accrued expenses	$	—		$	20.3

	Deferred income taxes	6.2			90.3

	Other noncurrent liabilities	34.7			29.9

	Net unrecognized tax benefits	$	40.9		$	140.5

	Gross unrecognized tax benefits	$	44.5		$	143.9

Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]	A reconciliation of the beginning and ending amount of gross unrecognized tax benefits for the years ended December 31, 2014, 2013 and 2012 is as follows:


		Year Ended December 31,
		2014			2013			2012
		(Dollars in millions)
	Balance at beginning of period	$	143.9		$	122.8		$	119.6

	Additions for current year tax positions	12			6.3			17.4

	Additions for prior year tax positions	—			63.8			31.9

	Reductions for settlements with tax authorities	(111.4		)	—			(46.1		)

	Reductions for expirations of statutes of limitations	—			(49.0		)	—

	Balance at end of period	$	44.5		$	143.9		$	122.8

Summary of Companys tax (refunds) payments	The following table summarizes the Company’s income tax (refunds) payments, net for the years ended December 31, 2014, 2013 and 2012:


		Year Ended December 31,
		2014			2013			2012
		(Dollars in millions)
	U.S. — federal	$	(7.7	)	$	(0.8	)	$	63

	U.S. — state and local	(6.8		)	2.9			11.8

	Non-U.S.	(2.2		)	79.8			55.7

	Total income tax (refunds) payments, net	$	(16.7	)	$	81.9		$	130.5

Accounts_Payable_and_Accrued_E1

Accounts Payable and Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2014
Payables and Accruals [Abstract]
Accounts payable and accrued expenses	Accounts payable and accrued expenses consisted of the following:


		December 31,
		2014		2013
		(Dollars in millions)
	Trade accounts payable	$	461.7	$	483

	Commodity and foreign currency hedge contracts	341.1		213.9

	Other accrued expenses	298.8		267.3

	Accrued payroll and related benefits	268.7		248

	Accrued taxes other than income	175.3		223.5

	Payable to voluntary employee beneficiary association for certain Patriot retirees (1)	75		20

	Accrued royalties	61.5		67.1

	Accrued interest	48.4		47.9

	Asset retirement obligations	30.2		21

	Accrued environmental cleanup-related costs	19.4		18.3

	Workers’ compensation obligations	10.9		10

	Income taxes payable	3.3		3.8

	Accrued health care insurance	2.4		7.1

	Liabilities associated with discontinued operations	12.5		133.1

	Total accounts payable and accrued expenses	$	1,809.20	$	1,764.00


	-1	Refer to Note 25. "Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation" herein for additional details related to this transaction.

Debt_Tables

Debt (Tables)	12 Months Ended
Debt (Tables)	Dec. 31, 2014
Debt Disclosure [Abstract]
Long-Term Debt	The Company’s total indebtedness as of December 31, 2014 and 2013 consisted of the following:


		December 31,
		2014			2013
		(Dollars in millions)
	2013 Term Loan Facility due September 2020	$	1,175.10		$	1,185.40
	2013 Term Loan Facility due September 2020	$	1,175.10		$	1,185.40
	7.375% Senior Notes due November 2016	650			650
	7.375% Senior Notes due November 2016	650			650
	6.00% Senior Notes due November 2018	1,518.80			1,518.80
	6.00% Senior Notes due November 2018	1,518.80			1,518.80
	6.50% Senior Notes due September 2020	650			650
	6.50% Senior Notes due September 2020	650			650
	6.25% Senior Notes due November 2021	1,339.60			1,339.60
	6.25% Senior Notes due November 2021	1,339.60			1,339.60
	7.875% Senior Notes due November 2026	247.6			247.5
	7.875% Senior Notes due November 2026	247.6			247.5
	Convertible Junior Subordinated Debentures due December 2066	382.3			379.7
		382.3			379.7
	Capital lease obligations	22.2			30.5
	Capital lease obligations	22.2			30.5
	Other	1.2			0.9
	Other	1.2			0.9
	Total	$	5,986.80		$	6,002.40
	Total	$	5,986.80		$	6,002.40
Schedule of Interest Payments	Interest payments on the Senior Notes are scheduled to occur each year as follows:


	Senior Notes		Interest Payment Dates
	6.00% Senior Notes		May 15 and November 15
	6.25% Senior Notes		May 15 and November 15
	6.50% Senior Notes		March 15 and September 15
	7.375% Senior Notes		May 1 and November 1
	7.875% Senior Notes		May 1 and November 1
Carrying amount of the equity and debt components of the Debentures	The following table illustrates the carrying amount of the equity and debt components of the Debentures:


		December 31,
		2014			2013
		(Dollars in millions)
	Carrying amount of the equity component	$	215.4		$	215.4
	Carrying amount of the equity component	$	215.4		$	215.4

	Principal amount of the liability component	$	732.5		$	732.5
	Principal amount of the liability component	$	732.5		$	732.5
	Unamortized discount	(350.2		)	(352.8		)
	Net carrying amount	$	382.3		$	379.7
	Net carrying amount	$	382.3		$	379.7
Effective interest rate and the interest expense related to the Debentures	The following table illustrates the effective interest rate and the interest expense related to the Debentures:


		Year Ended December 31,
		2014			2013			2012
		(Dollars in millions)
	Effective interest rate	4.9		%	4.9		%	4.9		%
	Interest expense — contractual interest coupon	$	34.8		$	34.8		$	34.8
	Interest expense — contractual interest coupon	$	34.8		$	34.8		$	34.8
	Interest expense — amortization of debt discount	2.6			2.3			2.1
	Interest expense — amortization of debt discount	2.6			2.3			2.1
Aggregate amounts of Long term debt maturities	The aggregate amounts of long-term debt maturities (including unamortized debt discounts) subsequent to December 31, 2014, including capital lease obligations, were as follows:




	Year of Maturity		(Dollars in millions)
	2015		$	21.2
	2015		$	21.2
	2016		669
	2016		669
	2017		12.9
	2017		12.9
	2018		1,530.90
	2018		1,530.90
	2019		12.1
	2019		12.1
	2020 and thereafter		3,740.70
	2020 and thereafter		3,740.70
	Total		$	5,986.80
	Total		$	5,986.80

Leases_Leases_Tables

Leases Leases (Tables)	12 Months Ended
	Dec. 31, 2014
Operating Leased Assets [Line Items]
Leases And Royalty Future Minimum Payments [Table Text Block]	Future minimum lease and royalty payments as of December 31, 2014 are as follows:


		Capital		Operating		Coal Lease
		Leases		Leases		and
						Royalty
	Year Ending December 31,					Obligations
		(Dollars in millions)
	2015	$	9.5	$	207.2	$	284.6

	2016	6.9		196		253.3

	2017	1.4		178.9		22.3

	2018	0.5		104.3		20.5

	2019	0.5		51.3		18.2

	2020 and thereafter	10.6		64.3		29

	Total minimum lease payments	29.4		$	802	$	627.9

	Less interest	7.2

	Present value of minimum capital lease payments	$	22.2

Asset_Retirement_Obligations_T

Asset Retirement Obligations (Tables)	12 Months Ended
	Dec. 31, 2014
Asset Retirement Obligation Disclosure [Abstract]
Reconciliations of the Company's ARO liability	Reconciliations of the Company’s asset retirement obligations are as follows:


		December 31,
		2014			2013
		(Dollars in millions)
	Balance at beginning of year	$	712.8		$	687.5

	Liabilities incurred or acquired	22.7			—

	Liabilities settled or disposed	(19.7		)	(15.4		)
	Accretion expense	39.3			39.3

	Revisions to estimates	(2.6		)	1.4

	Balance at end of year	$	752.5		$	712.8

	Less: Current portion (included in "Accounts payable and accrued expenses")	30.2			21

	Noncurrent obligation (included in "Asset Retirement Obligations")	722.3			691.8

	Balance at end of year — active locations	$	676.2		$	660.8

	Balance at end of year — closed or inactive locations	$	76.3		$	52

Postretirement_Health_Care_and1

Postretirement Health Care and Life Insurance Benefits (Tables) (Postretirement Health Care and Life Insurance Benefits [Member])	12 Months Ended
	Dec. 31, 2014
Postretirement Health Care and Life Insurance Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Components of net periodic postretirement benefit cost	Net periodic postretirement benefit cost included the following components:


		Year Ended December 31,
		2014				2013				2012
		(Dollars in millions)
	Service cost for benefits earned	$	12.2			$	15.8			$	14.9

	Interest cost on accumulated postretirement benefit obligation	36.4				41.8				54.9

	Amortization of prior service cost (credit)	1.3				(1.7		)		2.5

	Amortization of actuarial loss	14.5				24.1				32.8

	Settlement related to the Patriot bankruptcy reorganization (1)	—				63.2				—

	Special termination benefits (2)	1.6				0.9				—

	Net periodic postretirement benefit cost	$	66			$	144.1			$	105.1


	-1	Refer to Note 25. "Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation" herein for additional details related to this transaction.

	-2	Reflected in "Restructuring and pension settlement charges" in the consolidated statement of operations for the year ended December 31, 2014.
Amounts recognized in accumulated other comprehensive loss	The following includes pre-tax amounts recorded in "Accumulated other comprehensive loss":


		Year Ended December 31,
		2014				2013				2012
		(Dollars in millions)
	Net actuarial loss (gain) arising during year	$	115.8			$	(24.3	)		$	(68.3	)

	Prior service credit arising during year	(18.0		)		—				(31.9		)

	Amortization:

	Actuarial loss	(14.5		)		(24.1		)		(32.8		)
	Prior service (cost) credit	(1.3		)		1.7				(2.5		)

	Settlement related to the Patriot bankruptcy reorganization: (1)
	Actuarial loss	—				(61.3		)		—

	Prior service cost	—				(1.9		)		—

	Total recorded in other comprehensive loss (income)	$	82			$	(109.9	)		$	(135.5	)


	-1	Refer to Note 25. "Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation" herein for additional details related to this transaction.
Reconciled amount of plan's funded status	The following table sets forth the plans' funded status reconciled with the amounts shown in the consolidated balance sheets:


		December 31,
		2014				2013
		(Dollars in millions)
	Change in benefit obligation:

	Accumulated postretirement benefit obligation at beginning of period	$	735.4			$	1,026.10

	Service cost	12.2				15.8

	Interest cost	36.4				41.8

	Participant contributions	2.2				2.3

	Plan changes(1)	(18.0		)		—

	Benefits paid	(46.5		)		(66.5		)
	Actuarial loss (gain) (2)	115.8				(24.3		)

	Settlement related to the Patriot bankruptcy reorganization (3)	—				(260.7		)

	Special termination benefits	1.6				0.9

	Accumulated postretirement benefit obligation at end of period	839.1				735.4

	Change in plan assets:

	Fair value of plan assets at beginning of period	—				—

	Employer contributions	44.3				64.2

	Participant contributions	2.2				2.3

	Benefits paid and administrative fees (net of Medicare Part D reimbursements)	(46.5		)		(66.5		)
	Fair value of plan assets at end of period	—				—

	Funded status at end of year	(839.1		)		(735.4		)
	Less: Current portion (included in "Accounts payable and accrued expenses")	57.2				51.4

	Noncurrent obligation (included in "Accrued postretirement benefit costs")	$	(781.9	)		$	(684.0	)

	(1)	Includes the net impact of the following plan changes: a $45.4 million reduction to the benefit obligation related to various plan changes effective January 1, 2015 for certain plan participants that are designed to bring consistency amongst the various retiree medical programs; and a $27.6 million increase to the benefit obligation resulting from a plan change effective April 1, 2014 for certain plan participants' benefits no longer funded through a Medicare Advantage Program. The plan changes will not affect participant benefits.

	(2)	During 2014, the Company reviewed its demographic assumptions (including mortality, retirements and terminations) in conjunction with the recently-issued mortality tables published by the Society of Actuaries, to select assumptions that are aligned with the Company’s experience. The updated demographic assumptions increased the December 31, 2014 benefit obligation by approximately $63 million.

	(3)	Refer to Note 25. "Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation" herein for additional details related to this transaction.
Weighted-average assumptions used to determine the benefit obligations	The weighted-average assumptions used to determine the benefit obligations as of the end of each year were as follows:


		December 31,
		2014			2013
	Discount rate	4.1	%		4.9	%
	Measurement date	December 31, 2014			December 31, 2013

	The weighted-average assumptions used to determine net periodic benefit cost during each year were as follows:


		Year Ended December 31,
		2014			2013			2012
	Discount rate	4.9	%		4.21	%		5.05	%
	Measurement date	December 31, 2013			December 31, 2012			December 31, 2011

Assumed health care cost trend rate	The following presents information about the assumed health care cost trend rate:


		Year Ended December 31,
		2014			2013
	Pre-Medicare:
	Health care cost trend rate assumed for next year	7	%		6.26	%
	Rate to which the cost trend is assumed to decline (the ultimate trend rate)	4.75	%		4.67	%
	Year that the rate reaches the ultimate trend rate	2021			2023


	Post-Medicare:
	Health care cost trend rate assumed for next year	6	%		6.26	%
	Rate to which the cost trend is assumed to decline (the ultimate trend rate)	4.75	%		4.67	%
	Year that the rate reaches the ultimate trend rate	2021			2023

Assumed health care cost trend rates, one percentage point increase	A one-percentage-point change in the assumed health care cost trend would have the following effects:


		One Percentage-				One Percentage-
		Point Increase				Point Decrease
		(Dollars in millions)
	Effect on total service and interest cost components (1)	$	4.1			$	(3.8	)

	Effect on total postretirement benefit obligation (1)	$	80.6			$	(70.3	)


	(1)	In addition to the effect on total service and interest cost components of expense, changes in trend rates would also increase or decrease the actuarial gain or loss amortization expense component. The impact on actuarial gain or loss amortization would approximate the increase or decrease in the obligation divided by 11.70 years at January 1, 2015.
Summary of estimated future benefit payments	The following benefit payments (net of retiree contributions), which reflect expected future service, as appropriate, are expected to be paid by the Company:


		Postretirement
		Benefits
		(Dollars in millions)
	2015	$	57.2

	2016	59

	2017	59.9

	2018	60.4

	2019	60.7

	Years 2020-2024	297.6

Pension_and_Savings_Plans_Tabl

Pension and Savings Plans (Tables) (Pension Plans, Defined Benefit [Member])	12 Months Ended
	Dec. 31, 2014
Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic pension cost	Net periodic pension cost included the following components:


		Year Ended December 31,
		2014				2013				2012
		(Dollars in millions)
	Service cost for benefits earned	$	2.1			$	2.2			$	2

	Interest cost on projected benefit obligation	45.4				42.2				46.7

	Expected return on plan assets	(54.3		)		(59.5		)		(63.7		)
	Amortization of prior service cost	1.3				1				1

	Amortization of net actuarial losses	30.2				65.7				48.6

	Settlement charge	8.7				—				—

	Total net periodic pension cost	$	33.4			$	51.6			$	34.6

Amounts recognized in accumulated other comprehensive loss	The following includes pre-tax amounts recorded in "Accumulated other comprehensive loss":


		Year Ended December 31,
		2014				2013				2012
		(Dollars in millions)
	Net actuarial loss (gain) arising during year	$	79.2			$	(133.8	)		$	67.6

	Prior service cost arising during year	—				2.2				—

	Amortization:

	Net actuarial loss	(30.2		)		(65.7		)		(48.6		)
	Prior service cost	(1.3		)		(1.0		)		(1.0		)
	Settlement charge	(8.7		)		—				—

	Total recorded in other comprehensive loss (income)	$	39			$	(198.3	)		$	18

Summary of change in benefit obligation, change in plan assets and funded status	The following summarizes the change in benefit obligation, change in plan assets and funded status of the Plans:


		December 31,
		2014				2013
		(Dollars in millions)
	Change in benefit obligation:

	Projected benefit obligation at beginning of period	$	947.3			$	1,058.60

	Service cost	2.1				2.2

	Interest cost	45.4				42.2

	Benefits paid	(57.2		)		(59.1		)
	Actuarial loss (gain) (1)	106.6				(98.8		)

	Plan amendments	—				2.2

	Settlement	(41.7		)		—

	Projected benefit obligation at end of period	1,002.50				947.3

	Change in plan assets:

	Fair value of plan assets at beginning of period	851.4				813.7

	Actual return on plan assets	81.7				94.5

	Employer contributions	5.6				2.3

	Benefits paid	(57.2		)		(59.1		)
	Settlement	(41.7		)		—

	Fair value of plan assets at end of period	839.8				851.4

	Funded status at end of year	$	(162.7	)		$	(95.9	)
	Amounts recognized in the consolidated balance sheets:

	Current obligation (included in "Accounts payable and accrued expenses")	$	(1.7	)		$	(1.7	)
	Noncurrent obligation (included in "Other noncurrent liabilities")	(161.0		)		(94.2		)
	Net amount recognized	$	(162.7	)		$	(95.9	)
	(1) During 2014, the Company reviewed its demographic assumptions (such as mortality, retirements and terminations) in conjunction with the recently-issued mortality tables published by the Society of Actuaries, to select assumptions that are aligned with the Company’s experience. The updated demographic assumptions increased the December 31, 2014 benefit obligation by approximately $36 million.
Weighted-average assumptions used to determine benefit obligations	The weighted-average assumptions used to determine the benefit obligations as of the end of each year were as follows:


		December 31,
		2014			2013
	Discount rate	4.15	%		4.95	%
	Measurement date	December 31, 2014			December 31, 2013

Weighted-average assumptions used to determine net periodic benefit cost	The weighted-average assumptions used to determine net periodic benefit cost during each year were as follows:


		Year Ended December 31,
		2014			2013			2012
	Discount rate	4.95	%		4.1	%		5	%
	Expected long-term return on plan assets	6.85	%		7.75	%		8	%
	Measurement date	December 31, 2013			December 31, 2012			December 31, 2011

Fair value of assets in the Master Trust by category and by fair value valuation hierarchy	The following tables present the fair value of assets in the Master Trust by asset category and by fair value hierarchy:


		December 31, 2014
		Level 1				Level 2				Level 3			Total
		(Dollars in millions)
	U.S. equity securities	$	141.7			$	48.6			$	—		$	190.3

	International equity securities	—				69.8				—			69.8

	U.S. debt securities	25.3				29.1				—			54.4

	International debt securities	—				23.5				—			23.5

	Corporate debt securities	—				447.8				—			447.8

	Short-term investments	17.5				6.3				—			23.8

	Interests in real estate	—				—				30.2			30.2

	Total assets at fair value	$	184.5			$	625.1			$	30.2		$	839.8



		December 31, 2013
		Level 1				Level 2				Level 3			Total
		(Dollars in millions)
	U.S. equity securities	$	141.8			$	54.2			$	—		$	196

	International equity securities	—				80.6				—			80.6

	U.S. debt securities	30.6				30.7				—			61.3

	International debt securities	—				21.9				—			21.9

	Corporate debt securities	—				424.3				—			424.3

	Short-term investments	23.9				13.5				—			37.4

	Interests in real estate	—				—				29.9			29.9

	Total assets at fair value	$	196.3			$	625.2			$	29.9		$	851.4

Summary of changes in the fair value of the Master Trust's Level 3 investments	The table below sets forth a summary of changes in the fair value of the Master Trust’s Level 3 investments:


		Year Ended December 31,
		2014				2013
		(Dollars in millions)
	Balance, beginning of year	$	29.9			$	27.8

	Realized gains	0.2				0.7

	Unrealized gains relating to investments still held at the reporting date	4.9				2.6

	Purchases, sales and settlements, net	(4.8		)		(1.2		)
	Balance, end of year	$	30.2			$	29.9

Summary of estimated future benefit payments	The following benefit payments, which reflect expected future service, as appropriate, are expected to be paid by the Master Trust:


		Pension Benefits
		(Dollars in millions)
	2015	$	62.2

	2016	63

	2017	63.6

	2018	64.2

	2019	64.1

	Years 2020-2024	327.7

Stockholders_Equity_Tables

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2014
Stockholders' Equity (Tables) [Abstract]
Summary of common stock activity	The following table summarizes common stock activity from January 1, 2012 to December 31, 2014:


		2014		2013		2012
		(In millions)
	Shares outstanding at the beginning of the year	270.1		268.6		271.1

	Stock options exercised	—		0.1		0.2

	Stock grants to employees	1.3		1		1.5

	Employee stock purchases	0.5		0.5		0.3

	Shares relinquished	(0.2	)	(0.1	)	(0.3	)
	Shares repurchased	—		—		(4.2	)

	Shares outstanding at the end of the year	271.7		270.1		268.6

ShareBased_Compensation_Tables

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2014
Share-based Compensation [Abstract]
Share-based compensation expense recorded in 'Selling and administrative expenses'	Share-based compensation expense and cash flow amounts were as follows:


		Year Ended December 31,
		2014				2013				2012
		(Dollars in millions)
	Share-based compensation expense - equity classified awards	$	46.1			$	50.9			$	45.4

	Share-based compensation expense - liability classified awards	0.7				—				—

	Total share-based compensation expense	46.8				50.9				45.4

	Tax benefit	17.3				18.8				16.7

	Share-based compensation expense, net of tax benefit	29.5				32.1				28.7

	Cash received upon the exercise of stock options and from employee stock purchases	5.5				7.3				9.4

	(Write-off) excess tax benefits related to share-based compensation	(8.3		)		(4.5		)		8.3

Summary of restricted stock award activity	A summary of restricted stock award activity is as follows:


		Year Ended			Weighted
		December 31,			Average
		2014			Grant-Date
					Fair Value
	Nonvested at December 31, 2013	2,493,046			$	34.6

	Granted	1,331,077			19.19

	Vested	(425,116	)		57.59

	Forfeited	(211,416	)		25.13

	Nonvested at December 31, 2014	3,187,591			$	25.63

Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block]	A summary of restricted stock unit activity is as follows:


		Year Ended			Weighted
		December 31,			Average
		2014			Grant-Date
					Fair Value
	Nonvested at December 31, 2013	287,375			$	19.5

	Granted	218,017			19.48

	Vested	(3,261	)		23.56

	Forfeited	(5,025	)		21.4

	Nonvested at December 31, 2014	497,106			$	19.44

Schedule of Share-based Compensation, Stock Options, Activity	A summary of outstanding option activity under the plans is as follows:


		Year Ended			Weighted				Weighted		Aggregate
		December 31,			Average				Average		Intrinsic
		2014			Exercise				Remaining		Value (in
					Price				Contractual		millions)
									Life
	Options Outstanding at December 31, 2013	2,295,076			$	37.32			6		$	0.5

	Granted	1,044,426			19.44

	Exercised	(44,933	)		10.22

	Forfeited	(278,556	)		36.9

	Options Outstanding at December 31, 2014	3,016,013			$	31.57			6.39		$	—

	Vested and Exercisable	1,594,695			$	40.2			4.37		$	—

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	The weighted-average fair values of the Company’s stock options and the assumptions used in applying the Black-Scholes option pricing model were as follows:


		Year Ended December 31,
		2014				2013				2012
	Weighted-average fair value	$	7.38			$	12.13			$	18.59

	Risk-free interest rate	1.7		%		0.7		%		0.9		%
	Expected option life	5 years				5 years				5 years

	Expected volatility	48.4		%		64.1		%		64		%
	Dividend yield	1.7		%		1.2		%		0.6		%
Summary of performance unit activity	A summary of performance unit activity is as follows:


		Year Ended			Weighted
		December 31,			Average
		2014			Remaining
					Contractual
					Life
	Nonvested at December 31, 2013	463,317			1.6

	Granted	644,412

	Forfeited	(206,808	)
	Vested	(150,769	)
	Nonvested at December 31, 2014	750,152			1.5

Assumptions used in the valuations for grants	The assumptions used in the valuations for grants were as follows:


		Year Ended December 31,
		2014			2013			2012
	Risk-free interest rate	0.8	%		0.4	%		0.4	%
	Expected volatility	45.3	%		47.3	%		52.8	%
	Dividend yield	1.7	%		1.4	%		0.6	%

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2014
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
After-tax components of comprehensive income (loss)	The following table sets forth the after-tax components of comprehensive (loss) income:


		Foreign				Net				Prior Service			Cash Flow			Available-For-Sale Securities			Total
		Currency				Actuarial Loss				Cost Associated			Hedges						Accumulated
		Translation				Associated with				with									Other
		Adjustment				Postretirement				Postretirement									Comprehensive
						Plans and				Plans									(Loss) Income
						Workers’
						Compensation
						Obligations
		(Dollars in millions)
	December 31, 2011	$	3.1			$	(464.9	)		$	(9.6	)	$	335.7		$	(6.7	)	$	(142.4	)

	Net change in fair value	—				—				—			350.4			(15.5		)	334.9

	Reclassification from other comprehensive income to earnings	—				53.2				2.2			(298.6		)	22.5			(220.7		)

	Current period change	19.1				—				20.1			—			—			39.2

	December 31, 2012	22.2				(411.7		)		12.7			387.5			0.3			11

	Net change in fair value	—				—				—			(333.6		)	(12.3		)	(345.9		)

	Reclassification from other comprehensive income to earnings	—				95				0.7			(209.6		)	12.8			(101.1		)

	Current period change	(92.7		)		110.9				(1.4		)	—			—			16.8

	December 31, 2013	(70.5		)		(205.8		)		12			(155.7		)	0.8			(419.2		)

	Net change in fair value	—				—				—			(195.0		)	(3.7		)	(198.7		)

	Reclassification from other comprehensive income to earnings	—				31				1.7			(10.2		)	2.9			25.4

	Current period change	(41.0		)		(142.7		)		11.4			—			—			(172.3		)

	December 31, 2014	$	(111.5	)		$	(317.5	)		$	25.1		$	(360.9	)	$	—		$	(764.8	)

Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]	The following table provides additional information regarding items reclassified out of "Accumulated other comprehensive (loss) income" into earnings during the year ended December 31, 2014:


			Year Ended December 31, 2014				Year Ended December 31, 2013
	Details about accumulated other comprehensive (loss) income components		Amount reclassified from accumulated other comprehensive (loss) income (1)				Amount reclassified from accumulated other comprehensive (loss) income (1)				Affected line item in the consolidated statement of operations
			(Dollars in millions)				(Dollars in millions)
	Net actuarial loss associated with postretirement plans and workers' compensation obligations:
	Postretirement health care and life insurance benefits		$	(14.5	)		$	(24.1	)		Operating costs and expenses
	Postretirement health care and life insurance benefits		—				(61.3		)		Settlement charges related to the Patriot bankruptcy reorganization

	Defined benefit pension plans		(24.8		)		(54.4		)		Operating costs and expenses
	Defined benefit pension plans		(8.7		)		—				Restructuring and pension settlement charges

	Defined benefit pension plans		(5.4		)		(11.3		)		Selling and administrative expenses
	Insignificant items		4.1				(1.1		)

			(49.3		)		(152.2		)		Total before income taxes
			18.3				57.2				Income tax benefit

			$	(31.0	)		$	(95.0	)		Total after income taxes

	Prior service credit (cost) associated with postretirement plans:
	Postretirement health care and life insurance benefits		$	(1.3	)		$	1.7			Operating costs and expenses

	Postretirement health care and life insurance benefits		—				(1.9		)		Settlement charges related to the Patriot bankruptcy reorganization

	Defined benefit pension plans		(1.3		)		(1.0		)		Operating costs and expenses
			(2.6		)		(1.2		)		Total before income taxes
			0.9				0.5				Income tax benefit

			$	(1.7	)		$	(0.7	)		Total after income taxes

	Cash flow hedges:
	Foreign currency forward contracts		$	(27.3	)		$	162.4			Operating costs and expenses

	Fuel and explosives commodity swaps		(22.3		)		11.4				Operating costs and expenses

	Coal trading commodity futures, swaps and options		63.9				130.6				Other revenues

	Insignificant items		(0.4		)		(0.5		)
			13.9				303.9				Total before income taxes

			(3.7		)		(94.3		)		Income tax provision
			$	10.2			$	209.6			Total after income taxes


	Available-for-sale securities:
	Debt securities		$	—			$	0.2			Interest income

	Equity securities		(4.7		)		(21.5		)		Asset impairment and mine closure costs
			(4.7		)		(21.3		)		Total before income taxes
			1.8				8.5				Income tax benefit

			$	(2.9	)		$	(12.8	)		Total after income taxes
	(1) Presented as gains (losses) in the consolidated statements of operations.

Earnings_per_Share_Tables

Earnings per Share (Tables)	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Earnings allocation method utilized in the calculation of basic and diluted EPS	The following illustrates the earnings allocation method utilized in the calculation of basic and diluted EPS:


		Year Ended December 31,
		2014			2013			2012
		(In millions, except per share amounts)
	EPS numerator:

	Loss from continuing operations, net of income taxes	$	(749.1	)	$	(286.0	)	$	(470.9	)
	Less: Net income attributable to noncontrolling interests	9.7			12.3			10.6

	Loss from continuing operations attributable to common stockholders, before allocation of earnings to participating securities	(758.8		)	(298.3		)	(481.5		)
	Less: Earnings allocated to participating securities	1			0.8			0.7

	Loss from continuing operations attributable to common	(759.8		)	(299.1		)	(482.2		)
	stockholders, after allocation of earnings to participating securities
	Loss from discontinued operations attributable to common stockholders, after allocation of earnings to participating securities	(28.2		)	(226.6		)	(104.2		)
	Net loss attributable to common stockholders, after earnings	$	(788.0	)	$	(525.7	)	$	(586.4	)
	allocated to participating securities
	EPS denominator:

	Weighted average shares outstanding — basic and diluted	268.1			267.1			268

	Basic and diluted EPS attributable to common stockholders:

	Loss from continuing operations	$	(2.83	)	$	(1.12	)	$	(1.80	)
	Loss from discontinued operations	(0.11		)	(0.85		)	(0.39		)
	Net loss attributable to common stockholders	$	(2.94	)	$	(1.97	)	$	(2.19	)

Management_Labor_Relations_Ris

Management - Labor Relations Risk Management - Labor Relations (Tables)	12 Months Ended
	Dec. 31, 2014
Risk Management Labor Relations [Abstract]
Schedule of operations with employees represented by labor unions	The following table presents the Company's active mining operations as of December 31, 2014 in which the employees are represented by organized labor unions:


	Mine		Current Agreement Expiration Date

	U. S.
	Kayenta (1)		Sep-19

	Australia
	Owner-operated mines:
	Wambo Open-Cut (2)(3)		Aug-14
	North Wambo Underground (2)(3)		Apr-15
	North Goonyella (3)		May-15
	Metropolitan (3)		Aug-15
	Millennium (3)		Oct-15
	Wilpinjong		May-16
	Coppabella (4)		Oct-16
	Moorvale (4)		Jun-17

	Contractor-operated mines:
	Burton		Dec-16

	-1	Hourly workers at the Company’s Kayenta Mine in Arizona are represented by the UMWA under the Western Surface Agreement, which is effective through September 16, 2019. This agreement covers approximately 9% of the Company’s U.S. subsidiaries’ hourly employees, who generated approximately 4% of the Company’s U.S. production during the year ended December 31, 2014.

	-2	Employees of the Company's Wambo Coal Handling and Preparation Plant facility also operate under a separate enterprise agreement. That agreement expired in October 2014 and negotiations are underway. There have been no disruptions to the operations of the plant as a result of the expiration of the agreement.

	(3)	Negotiations for the Wambo Open-Cut, North Wambo Underground, North Goonyella, Metropolitan and Millennium mines are all underway or have been scheduled and the mines continue to operate. Hourly employees of these mines comprise approximately 56% of the Company's Australian subsidiaries hourly employees, who generated approximately 42% of the Company's Australian production during the year ended December 31, 2014.

	(4)	Employees of the Company's Coppabella/Moorvale Coal Handling and Preparation Plant facility also operate under a separate enterprise agreement. That agreement expired in March 2014 and negotiations are underway. There have been no disruptions to the operations of the plant as a result of the expiration of the agreement.

Financial_Instruments_Tables

Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2014
Financial Instruments And Guarantees With Off Balance Sheet Risk Disclosure [Abstract]
Letters of credit, bank guarantees, surety bonds and corporate guarantees	As of December 31, 2014, the Company had the following financial instruments with off-balance-sheet risk:


		Reclamation		Coal Lease		Workers’		Other(1)		Total
		Obligations		Obligations		Compensation
						Obligations
		(Dollars in millions)
	Self bonding	$	1,361.40	$	—	$	—	$	—	$	1,361.40

	Surety bonds	325.2		103.8		92.3		11.4		532.7

	Bank guarantees	319.8		—		—		117.4		437.2

	Letters of credit	17.6		—		34.1		100.9		152.6

		$	2,024.00	$	103.8	$	126.4	$	229.7	$	2,483.90


	(1)	Other includes the $79.7 million in letters of credit related to Dominion Terminal Associates and the PBGC, as described below, and an additional $150.0 million in bank guarantees, letters of credit and surety bonds related to road maintenance, performance guarantees and other operations.

Summary_Quarterly_Financial_In1

Summary Quarterly Financial Information (Tables)	12 Months Ended
	Dec. 31, 2014													Dec. 31, 2013
Summary Quarterly Financial Information (Tables) [Abstract]
Summary of the unaudited quarterly results of operations	A summary of the unaudited quarterly results of operations for the years ended December 31, 2014 and 2013 is presented below.

															Year Ended December 31, 2013
		Year Ended December 31, 2014													First Quarter			Second Quarter		Third Quarter			Fourth Quarter
		First Quarter			Second Quarter			Third Quarter			Fourth Quarter				(In millions, except per share data)
		(In millions, except per share data)												Revenues	$	1,748.00		$	1,725.30	$	1,797.60		$	1,742.80
	Revenues	$	1,626.80		$	1,758.00		$	1,722.90		$	1,684.50
														Operating profit (loss)	88.8			26.4		112.2			(552.2		)
	Operating profit (loss)	2.9			32.8			36.2			(207.0		)
														(Loss) income from continuing operations, net of income taxes	(10.3		)	101.4		24			(401.1		)
	Loss from continuing operations, net of income taxes	(44.3		)	(72.0		)	(154.0		)	(478.8		)
	Net loss	(44.1		)	(71.2		)	(149.0		)	(513.0		)	Net (loss) income	(19.4		)	87.1		(19.1		)	(561.2		)
	Net loss attributable to common stockholders	(48.5		)	(73.3		)	(150.6		)	(514.6		)
	Basic and diluted EPS — continuing operations(1)	$	(0.18	)	$	(0.28	)	$	(0.58	)	$	(1.79	)	Net (loss) income attributable to common stockholders	(23.4		)	90.3		(26.1		)	(565.7		)
	Weighted average shares used in calculating basic and diluted EPS	267.9			268			268.2			268.2
														Basic EPS — continuing operations(1)	$	(0.05	)	$	0.39	$	0.06		$	(1.52	)

	(1)	EPS for the quarters may not sum to the amounts for the year as each period is computed on a discrete basis.												Diluted EPS — continuing operations(1)	(0.05		)	0.39		0.06			(1.52		)

														Weighted average shares used in calculating basic EPS	266.9			266.9		267.2			267.3

														Weighted average shares used in calculating diluted EPS	266.9			267.5		267.7			267.3


														(1)	EPS for the quarters may not sum to the amounts for the year as each period is computed on a discrete basis

Segment_Information_Tables

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Operating segment results	Segment results for the year ended December 31, 2014 were as follows (assets as of December 31, 2014):


		Western				Midwestern				Australian			Trading and			Corporate			Consolidated
		U.S. Mining				U.S. Mining				Mining			Brokerage			and Other
		(Dollars in millions)
	Revenues	$	2,825.70			$	1,198.10			$	2,671.80		$	58.4		$	38.2		$	6,792.20

	Adjusted EBITDA	770.4				301.4				74.4			14.9			(347.1		)	814

	Total assets	3,431.30				667.8				6,623.90			300.7			2,167.40			13,191.10

	Property, plant, equipment and mine development, net	3,127.80				612.1				5,503.70			1.1			1,332.60			10,577.30

	Additions to property, plant, equipment and mine development	37.9				57.4				84.1			—			15			194.4

	Federal coal lease expenditures	276.7				—				—			—			—			276.7

	Loss from equity affiliates	—				—				—			—			107.6			107.6

	Segment results for the year ended December 31, 2013 were as follows (assets as of December 31, 2013):


		Western				Midwestern				Australian			Trading and			Corporate			Consolidated
		U.S. Mining				U.S. Mining				Mining			Brokerage			and Other
		(Dollars in millions)
	Revenues	$	2,669.60			$	1,335.50			$	2,904.60		$	66		$	38		$	7,013.70

	Adjusted EBITDA	698.3				428.3				316.6			(19.9		)	(376.1		)	1,047.20

	Total assets	3,307.60				716.8				7,081.20			389.6			2,638.20			14,133.40

	Property, plant, equipment and mine development, net	2,986.80				667.6				5,947.10			1.8			1,479.20			11,082.50

	Additions to property, plant, equipment and mine development	48				27.2				230.3			0.1			22.8			328.4

	Federal coal lease expenditures	276.8				—				—			—			—			276.8

	Loss from equity affiliates	—				—				—			—			40.2			40.2

	Segment results for the year ended December 31, 2012 were as follows (assets as of December 31, 2012):


		Western				Midwestern				Australian			Trading and			Corporate			Consolidated
		U.S. Mining				U.S. Mining				Mining			Brokerage			and Other
		(Dollars in millions)
	Revenues	$	2,949.30			$	1,403.70			$	3,503.60		$	199.9		$	21		$	8,077.50

	Adjusted EBITDA	832.8				427				938.9			119.7			(481.9		)	1,836.50

	Total assets	3,257.90				728.5				7,990.80			543.9			3,287.90			15,809.00

	Property, plant, equipment and mine development, net	2,896.10				707.5				6,595.50			1.6			1,601.00			11,801.70

	Additions to property, plant, equipment and mine development	121.4				74.7				743.4			0.1			46.4			986

	Federal coal lease expenditures	276.5				—				—			—			—			276.5

	Loss from equity affiliates	—				—				—			—			61.2			61.2

Reconciliation of Adjusted EBITDA to consolidated income from continuing operations	A reconciliation of Adjusted EBITDA to consolidated loss from continuing operations, net of income taxes follows:


		Year Ended December 31,
		2014				2013				2012
		(Dollars in millions)
	Total Adjusted EBITDA	$	814			$	1,047.20			$	1,836.50

	Depreciation, depletion and amortization	(655.7		)		(740.3		)		(663.4		)
	Asset retirement obligation expenses	(81.0		)		(66.5		)		(67.0		)
	Asset impairment and mine closure costs	(154.4		)		(528.3		)		(929.0		)
	Settlement charges related to the Patriot bankruptcy reorganization	—				(30.6		)		—

	Change in deferred tax asset valuation allowance related to equity affiliates	(52.3		)		—				—

	Amortization of basis difference related to equity affiliates	(5.7		)		(6.3		)		(4.6		)
	Interest expense	(428.2		)		(425.2		)		(405.6		)
	Interest income	15.4				15.7				24.5

	Income tax (provision) benefit	(201.2		)		448.3				(262.3		)

	Loss from continuing operations, net of income taxes	$	(749.1	)		$	(286.0	)		$	(470.9	)
Revenue as a percent of total revenue from external customers by geographic region	The following table presents revenues as a percent of total revenue from external customers by geographic region:


		Year Ended December 31,
		2014			2013			2012
	U.S.	59.5	%		61.1	%		55.4	%
	Japan	9.5	%		9.8	%		12.3	%
	China	6.1	%		10.2	%		6.8	%
	South Korea	5.2	%		3.8	%		5.8	%
	Other	19.7	%		15.1	%		19.7	%
	Total	100	%		100	%		100	%

Supplemental_GuarantorNonGuara1

Supplemental Guarantor/Non-Guarantor Financial Information (Tables)	12 Months Ended
	Dec. 31, 2014
Supplemental Guarantor Non Guarantor Financial Information [Abstract]
Supplemental Consolidated Statement of Operations [Table Text Block]	PEABODY ENERGY CORPORATION
	SUPPLEMENTAL CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS


		Year Ended December 31, 2014
		Parent				Guarantor				Non-Guarantor				Eliminations				Consolidated
		Company				Subsidiaries				Subsidiaries
		(Dollars in millions)
	Total revenues	$	—			$	3,964.80			$	2,902.10			$	(74.7	)		$	6,792.20

	Costs and expenses

	Operating costs and expenses (exclusive of items shown separately below)	49.6				2,927.30				2,814.70				(74.7		)		5,716.90

	Depreciation, depletion and amortization	—				310.4				345.3				—				655.7

	Asset retirement obligation expenses	—				25.3				55.7				—				81

	Selling and administrative expenses	46.8				161.1				19.2				—				227.1

	Restructuring and pension settlement charges	—				23.8				2.2				—				26

	Other operating (income) loss:

	Net gain on disposal or exchange of assets	—				(18.5		)		(22.9		)		—				(41.4		)

	Asset impairment and mine closure costs	4.7				71.1				78.6				—				154.4

	Loss from equity affiliates and investment in subsidiaries	431.1				6.6				101				(431.1		)		107.6

	Interest expense	424.7				6.4				34.6				(37.5		)		428.2

	Interest income	(15.3		)		(10.3		)		(27.3		)		37.5				(15.4		)

	(Loss) income from continuing operations before income taxes	(941.6		)		461.6				(499.0		)		431.1				(547.9		)

	Income tax (benefit) provision	(186.2		)		316.7				70.7				—				201.2

	(Loss) income from continuing operations, net of income taxes	(755.4		)		144.9				(569.7		)		431.1				(749.1		)

	(Loss) income from discontinued operations, net of income taxes	(31.6		)		(7.2		)		10.6				—				(28.2		)

	Net (loss) income	(787.0		)		137.7				(559.1		)		431.1				(777.3		)

	Less: Net income attributable to noncontrolling interests	—				—				9.7				—				9.7

	Net (loss) income attributable to common stockholders	$	(787.0	)		$	137.7			$	(568.8	)		$	431.1			$	(787.0	)

	PEABODY ENERGY CORPORATION
	SUPPLEMENTAL CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS


		Year Ended December 31, 2013
		Parent				Guarantor				Non-Guarantor				Eliminations				Consolidated
		Company				Subsidiaries				Subsidiaries
		(Dollars in millions)
	Total revenues	$	—			$	4,027.90			$	3,230.30			$	(244.5	)		$	7,013.70

	Costs and expenses

	Operating costs and expenses (exclusive of items shown separately below)	(173.6		)		3,471.70				2,675.50				(244.5		)		5,729.10

	Depreciation, depletion and amortization	—				329.4				410.9				—				740.3

Asset retirement obligation expenses	—				33.3				33.2				—				66.5

Selling and administrative expenses	50.9				167.9				25.4				—				244.2

Restructuring and pension settlement charges	—				11.9				—				—				11.9

Other operating (income) loss:

Net gain on disposal or exchange of assets	—				(52.6		)		—				—				(52.6		)

Asset impairment and mine closure costs	21.5				6.5				500.3				—				528.3

Settlement charges related to the Patriot bankruptcy reorganization	30.6				—				—				—				30.6

Loss from equity affiliates and investment in subsidiaries	272.5				8.3				31.9				(272.5		)		40.2

Interest expense	420.8				244.5				169				(409.1		)		425.2

(Gain) loss from extinguishment of affiliate debt	—				(155.5		)		155.5				—				—

Interest income	(79.6		)		(311.6		)		(33.6		)		409.1				(15.7		)

Unrealized loss (gain) on derivatives	—				34				(34.0		)		—				—

(Loss) income from continuing operations before income taxes	(543.1		)		240.1				(703.8		)		272.5				(734.3		)

Income tax benefit	(92.2		)		(110.9		)		(245.2		)		—				(448.3		)

(Loss) income from continuing operations, net of income taxes	(450.9		)		351				(458.6		)		272.5				(286.0		)

Loss from discontinued operations, net of income taxes	(74.0		)		(5.6		)		(147.0		)		—				(226.6		)

Net (loss) income	(524.9		)		345.4				(605.6		)		272.5				(512.6		)

Less: Net income attributable to noncontrolling interests	—				—				12.3				—				12.3

Net (loss) income attributable to common stockholders	$	(524.9	)		$	345.4			$	(617.9	)		$	272.5			$	(524.9	)

PEABODY ENERGY CORPORATION
SUPPLEMENTAL CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS


	Year Ended December 31, 2012
	Parent				Guarantor				Non-Guarantor				Eliminations				Consolidated
	Company				Subsidiaries				Subsidiaries
	(Dollars in millions)
Total revenues	$	—			$	4,571.30			$	3,738.40			$	(232.2	)		$	8,077.50

Costs and expenses

Operating costs and expenses (exclusive of items shown separately below)	(395.2		)		3,344.10				3,216.00				(232.2		)		5,932.70

Depreciation, depletion and amortization	—				315.6				347.8				—				663.4

Asset retirement obligation expenses	—				42.9				24.1				—				67

Selling and administrative expenses	38.7				199.7				30.4				—				268.8

Other operating (income) loss:

Net gain on disposal or exchange of assets	—				(14.7		)		(2.4		)		—				(17.1		)

Asset impairment and mine closure costs	35.5				86.8				806.7				—				929

Loss from equity affiliates and investment in subsidiaries	720				12.5				48.7				(720.0		)		61.2

Interest expense	413.9				13.9				475.6				(497.8		)		405.6

Interest income	(309.8		)		(149.1		)		(63.4		)		497.8				(24.5		)

Unrealized (gain) loss on derivatives	—				(35.3		)		35.3				—				—

(Loss) income from continuing operations before income taxes	(503.1		)		754.9				(1,180.4		)		720				(208.6		)

Income tax provision	80.2				105.8				76.3				—				262.3

(Loss) income from continuing operations, net of income taxes	(583.3		)		649.1				(1,256.7		)		720				(470.9		)

Loss from discontinued operations, net of income taxes	(2.4		)		(82.2		)		(19.6		)		—				(104.2		)

Net (loss) income	(585.7		)		566.9				(1,276.3		)		720				(575.1		)

Less: Net income attributable to noncontrolling interests	—				—				10.6				—				10.6

Net (loss) income attributable to common stockholders	$	(585.7	)		$	566.9			$	(1,286.9	)		$	720			$	(585.7	)

SupplementalCondensedConsolidatingStatementsOfComprehensiveIncomeLoss [Table Text Block]	PEABODY ENERGY CORPORATION
	SUPPLEMENTAL CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME


		Year Ended December 31, 2014
		Parent				Guarantor				Non-Guarantor				Eliminations				Consolidated
		Company				Subsidiaries				Subsidiaries
		(Dollars in millions)
	Net (loss) income	$	(787.0	)		$	137.7			$	(559.1	)		$	431.1			$	(777.3	)

	Other comprehensive (loss) income, net of income taxes:

	Net change in unrealized losses on available-for-sale securities (net of $0.5 tax benefit)
	Unrealized holding losses on available-for-sale securities	(3.7		)		—				—				—				(3.7		)

	Less: Reclassification for realized losses included in net (loss) income	2.9				—				—				—				2.9

	Net change in unrealized losses on available-for-sale securities	(0.8		)		—				—				—				(0.8		)

	Net unrealized losses on cash flow hedges (net of $54.6 tax benefit)

	(Decrease) increase in fair value of cash flow hedges	(225.9		)		—				30.9				—				(195.0		)

	Less: Reclassification for realized losses (gains) included in net (loss) income	31.3				—				(41.5		)		—				(10.2		)

	Net unrealized losses on cash flow hedges	(194.6		)		—				(10.6		)		—				(205.2		)

	Postretirement plans and workers' compensation obligations (net of $10.3 tax benefit)

	Prior service credit for the period	—				11.4				—				—				11.4

	Net actuarial (loss) gain for the period	—				(150.2		)		7.5				—				(142.7		)

	Amortization of actuarial loss (gain) and prior service cost	—				35.5				(2.8		)		—				32.7

	Postretirement plans and workers' compensation obligations	—				(103.3		)		4.7				—				(98.6		)

	Foreign currency translation adjustment	—				—				(41.0		)		—				(41.0		)

	Other comprehensive loss from investment in subsidiaries	(150.2		)		—				—				150.2				—

	Other comprehensive loss, net of income taxes	(345.6		)		(103.3		)		(46.9		)		150.2				(345.6		)

	Comprehensive (loss) income	(1,132.6		)		34.4				(606.0		)		581.3				(1,122.9		)

	Less: Comprehensive income attributable to noncontrolling interests	—				—				9.7				—				9.7

	Comprehensive (loss) income attributable to common stockholders	$	(1,132.6	)		$	34.4			$	(615.7	)		$	581.3			$	(1,132.6	)

	PEABODY ENERGY CORPORATION
	SUPPLEMENTAL CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME


		Year Ended December 31, 2013
		Parent				Guarantor				Non-Guarantor				Eliminations				Consolidated
		Company				Subsidiaries				Subsidiaries
		(Dollars in millions)
	Net (loss) income	$	(524.9	)		$	345.4			$	(605.6	)		$	272.5			$	(512.6	)

	Other comprehensive (loss) income, net of income taxes:

	Net change in unrealized gains (losses) on available-for-sale securities (net of $0.5 tax provision)
	Unrealized holding losses on available-for-sale securities	(12.2		)		—				(0.1		)		—				(12.3		)

Less: Reclassification for realized losses (gains) included in net income	13				—				(0.2		)		—				12.8

Net change in unrealized gains (losses) on available-for-sale securities	0.8				—				(0.3		)		—				0.5

Net unrealized losses on cash flow hedges (net of $300.0 tax benefit)

(Decrease) increase in fair value of cash flow hedges	(368.4		)		—				34.8				—				(333.6		)

Less: Reclassification for realized gains included in net income	(109.0		)		—				(100.6		)		—				(209.6		)

Net unrealized losses on cash flow hedges	(477.4		)		—				(65.8		)		—				(543.2		)

Postretirement plans and workers' compensation obligations (net of $121.7 tax provision)

Prior service cost for the period	—				(1.4		)		—				—				(1.4		)

Net actuarial gain for the period	—				103.8				7.1				—				110.9

Amortization of actuarial loss (gain) and prior service cost	—				95.8				(0.1		)		—				95.7

Postretirement plans and workers' compensation obligations	—				198.2				7				—				205.2

Foreign currency translation adjustment	—				—				(92.7		)		—				(92.7		)

Other comprehensive income from investment in subsidiaries	46.4				—				—				(46.4		)		—

Other comprehensive (loss) income, net of income taxes	(430.2		)		198.2				(151.8		)		(46.4		)		(430.2		)

Comprehensive (loss) income	(955.1		)		543.6				(757.4		)		226.1				(942.8		)

Less: Comprehensive income attributable to noncontrolling interests	—				—				12.3				—				12.3

Comprehensive (loss) income attributable to common stockholders	$	(955.1	)		$	543.6			$	(769.7	)		$	226.1			$	(955.1	)

PEABODY ENERGY CORPORATION
SUPPLEMENTAL CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME


	Year Ended December 31, 2012
	Parent				Guarantor				Non-Guarantor				Eliminations				Consolidated
	Company				Subsidiaries				Subsidiaries
	(Dollars in millions)
Net (loss) income	$	(585.7	)		$	566.9			$	(1,276.3	)		$	720			$	(575.1	)

Other comprehensive income, net of income taxes:
Net change in unrealized gains (losses) on available-for-sale securities (net of $4.0 tax provision)
Unrealized holding losses on available-for-sale securities	(15.5		)		—				—				—				(15.5		)

Less: Reclassification for realized losses included in net income	22.5				—				—				—				22.5

Net change in unrealized gains on available-for-sale securities	7				—				—				—				7

Net unrealized losses on cash flow hedges (net of $3.9 tax benefit)

Increase in fair value of cash flow hedges	205.9				—				144.5				—				350.4

Less: Reclassification for realized gains included in net income	(249.1		)		—				(49.5		)		—				(298.6		)

Net unrealized (losses) gains on cash flow hedges	(43.2		)		—				95				—				51.8

Postretirement plans and workers' compensation obligations (net of $43.9 tax provision)

Prior service cost for the period	—				20.1				—				—				20.1

Net actuarial (loss) gain for the period	—				(0.9		)		0.9				—				—

Amortization of actuarial loss and prior service cost	—				54.5				0.9				—				55.4

Postretirement plans and workers' compensation obligations	—				73.7				1.8				—				75.5

Foreign currency translation adjustment	—				—				19.1				—				19.1

Other comprehensive income from investment in subsidiaries	189.6				—				—				(189.6		)		—

Other comprehensive income, net of income taxes	153.4				73.7				115.9				(189.6		)		153.4

Comprehensive (loss) income	(432.3		)		640.6				(1,160.4		)		530.4				(421.7		)

Less: Comprehensive income attributable to noncontrolling interests	—				—				10.6				—				10.6

Comprehensive (loss) income attributable to common stockholders	$	(432.3	)		$	640.6			$	(1,171.0	)		$	530.4			$	(432.3	)

Supplemental Consolidated Balance Sheets [Table Text Block]	PEABODY ENERGY CORPORATION
	SUPPLEMENTAL CONDENSED CONSOLIDATING BALANCE SHEETS


		December 31, 2014
		Parent				Guarantor				Non-Guarantor				Reclassifications/				Consolidated
		Company				Subsidiaries				Subsidiaries				Eliminations
		(Dollars in millions)
	Assets

	Current assets

	Cash and cash equivalents	$	188.7			$	1.2			$	108.1			$	—			$	298

	Accounts receivable, net	—				14.5				548.6				—				563.1

	Receivables from affiliates, net	258.4				—				105.9				(364.3		)		—

	Inventories	—				191.8				214.7				—				406.5

	Assets from coal trading activities, net	—				53.8				3.8				—				57.6

	Deferred income taxes	64.5				8.6				6.9				—				80

	Other current assets	—				44.5				261.3				—				305.8

	Total current assets	511.6				314.4				1,249.30				(364.3		)		1,711.00

	Property, plant, equipment and mine development, net	—				5,005.20				5,572.10				—				10,577.30

	Deferred income taxes	—				8.2				—				(7.5		)		0.7

	Investments and other assets	10,209.40				4				621.6				(9,932.9		)		902.1

	Notes receivable from affiliates, net	—				1,655.70				—				(1,655.7		)		—

	Total assets	$	10,721.00			$	6,987.50			$	7,443.00			$	(11,960.4	)		$	13,191.10

	Liabilities and Stockholders’ Equity

	Current liabilities

	Current maturities of long-term debt	$	12			$	0.1			$	9.1			$	—			$	21.2

	Payables to affiliates, net	—				364.3				—				(364.3		)		—

	Liabilities from coal trading activities, net	—				10.7				22				—				32.7

	Accounts payable and accrued expenses	474.5				682.5				652.2				—				1,809.20

	Total current liabilities	486.5				1,057.60				683.3				(364.3		)		1,863.10

	Long-term debt, less current maturities	5,951.60				6.3				7.7				—				5,965.60

	Deferred income taxes	90.5				—				6.1				(7.5		)		89.1

	Notes payable to affiliates, net	1,033.40				—				622.3				(1,655.7		)		—

	Other noncurrent liabilities	434.2				1,717.40				395.2				—				2,546.80

	Total liabilities	7,996.20				2,781.30				1,714.60				(2,027.5		)		10,464.60

	Peabody Energy Corporation’s stockholders’ equity	2,724.80				4,206.20				5,726.70				(9,932.9		)		2,724.80

Noncontrolling interests	—				—				1.7				—				1.7

Total stockholders’ equity	2,724.80				4,206.20				5,728.40				(9,932.9		)		2,726.50

Total liabilities and stockholders’ equity	$	10,721.00			$	6,987.50			$	7,443.00			$	(11,960.4	)		$	13,191.10

PEABODY ENERGY CORPORATION
SUPPLEMENTAL CONDENSED CONSOLIDATING BALANCE SHEETS


	December 31, 2013
	Parent				Guarantor				Non-Guarantor				Reclassifications/				Consolidated
	Company				Subsidiaries				Subsidiaries				Eliminations
					(Dollars in millions)
Assets

Current assets

Cash and cash equivalents	$	300.7			$	0.3			$	143			$	—			$	444

Accounts receivable, net	1.3				—				559.1				(2.5		)		557.9

Receivables from affiliates, net	68.4				—				—				(68.4		)		—

Inventories	—				235.1				271.6				—				506.7

Assets from coal trading activities, net	—				46.7				—				(10.6		)		36.1

Deferred income taxes	—				61.9				6.4				(1.9		)		66.4

Other current assets	34.5				73.7				273.4				—				381.6

Total current assets	404.9				417.7				1,253.50				(83.4		)		1,992.70

Property, plant, equipment and mine development, net	—				5,055.70				6,026.80				—				11,082.50

Deferred income taxes	16.5				—				7.8				(16.5		)		7.8

Investments and other assets	11,394.90				8.8				762.6				(11,115.9		)		1,050.40

Notes receivable from affiliates, net	—				1,433.00				—				(1,433.0		)		—

Total assets	$	11,816.30			$	6,915.20			$	8,050.70			$	(12,648.8	)		$	14,133.40

Liabilities and Stockholders’ Equity

Current liabilities

Current maturities of long-term debt	$	12			$	0.1			$	19.6			$	—			$	31.7

Payables to affiliates, net	—				10.4				58				(68.4		)		—

Deferred income taxes	1.9				—				—				(1.9		)		—

Liabilities from coal trading activities, net	—				0.2				16.5				(10.6		)		6.1

Accounts payable and accrued expenses	360				601.4				805.1				(2.5		)		1,764.00

Total current liabilities	373.9				612.1				899.2				(83.4		)		1,801.80

Long-term debt, less current maturities	5,959.10				6.5				5.1				—				5,970.70

Deferred income taxes	—				55.9				1.5				(16.5		)		40.9

Notes payable to affiliates, net	1,032.60				—				400.4				(1,433.0		)		—

Other noncurrent liabilities	542				1,452.50				377.6				—				2,372.10

Total liabilities	7,907.60				2,127.00				1,683.80				(1,532.9		)		10,185.50

Peabody Energy Corporation’s stockholders’ equity	3,908.70				4,788.20				6,327.70				(11,115.9		)		3,908.70

Noncontrolling interests	—				—				39.2				—				39.2

Total stockholders’ equity	3,908.70				4,788.20				6,366.90				(11,115.9		)		3,947.90

Total liabilities and stockholders’ equity	$	11,816.30			$	6,915.20			$	8,050.70			$	(12,648.8	)		$	14,133.40

Unaudited Supplemental Condensed Consolidating Statements of Cash Flows	PEABODY ENERGY CORPORATION
	SUPPLEMENTAL CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS


		Year Ended December 31, 2014
		Parent				Guarantor				Non-Guarantor				Consolidated
		Company				Subsidiaries				Subsidiaries
						(Dollars in millions)
	Cash Flows From Operating Activities

	Net cash (used in) provided by continuing operations	$	(369.0	)		$	776.1			$	33.9			$	441

	Net cash used in discontinued operations	(73.3		)		(4.6		)		(26.5		)		(104.4		)
	Net cash (used in) provided by operating activities	(442.3		)		771.5				7.4				336.6

	Cash Flows From Investing Activities

	Additions to property, plant, equipment and mine development	—				(108.5		)		(85.9		)		(194.4		)

	Changes in accrued expenses related to capital expenditures	—				3.4				(20.0		)		(16.6		)

	Federal coal lease expenditures	—				(276.7		)		—				(276.7		)

	Proceeds from disposal of assets, net of notes receivable	—				105.9				97.8				203.7

	Purchases of debt securities	—				—				(15.1		)		(15.1		)

	Proceeds from sales and maturities of debt securities	—				—				13.5				13.5

	Contributions to joint ventures	—				—				(529.8		)		(529.8		)

	Distributions from joint ventures	—				—				534.2				534.2

	Advances to related parties	—				—				(33.7		)		(33.7		)

	Repayment of loans from related parties	—				—				5.4				5.4

	Other, net	—				(4.4		)		(0.6		)		(5.0		)

	Net cash used in investing activities	—				(280.3		)		(34.2		)		(314.5		)

	Cash Flows From Financing Activities
	Proceeds from long-term debt	—				—				1.1				1.1

	Repayments of long-term debt	(12.0		)		(0.1		)		(8.9		)		(21.0		)
	Payment of deferred financing costs	(10.1		)		—				—				(10.1		)

	Dividends paid	(92.3		)		—				—				(92.3		)

	Restricted cash for distributions to noncontrolling interest	—				—				(42.5		)		(42.5		)

	Other, net	3.1				(1.7		)		(4.7		)		(3.3		)

	Transactions with affiliates, net	441.6				(488.5		)		46.9				—

	Net cash provided by (used in) financing activities	330.3				(490.3		)		(8.1		)		(168.1		)

	Net change in cash and cash equivalents	$	(112.0	)		$	0.9			$	(34.9	)		$	(146.0	)

	Cash and cash equivalents at beginning of year	300.7				0.3				143				444

	Cash and cash equivalents at end of year	$	188.7			$	1.2			$	108.1			$	298

	PEABODY ENERGY CORPORATION
SUPPLEMENTAL CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS


	Year Ended December 31, 2013
	Parent				Guarantor				Non-Guarantor				Consolidated
	Company				Subsidiaries				Subsidiaries
					(Dollars in millions)
Cash Flows From Operating Activities

Net cash (used in) provided by continuing operations	$	(24.3	)		$	778.7			$	25.7			$	780.1

Net cash used in discontinued operations	(20.4		)		(7.6		)		(29.7		)		(57.7		)
Net cash (used in) provided by operating activities	(44.7		)		771.1				(4.0		)		722.4

Cash Flows From Investing Activities

Additions to property, plant, equipment and mine development	—				(95.9		)		(232.5		)		(328.4		)

Changes in accrued expenses related to capital expenditures	—				(1.2		)		(119.5		)		(120.7		)

Federal coal lease expenditures	—				(276.8		)		—				(276.8		)

Proceeds from disposal of assets, net of notes receivable	—				93				85.3				178.3

Purchases of debt securities	—				—				(22.8		)		(22.8		)

Proceeds from sales and maturities of debt securities	—				—				22.9				22.9

Maturity of short-term investments	—				—				4.8				4.8

Contributions to joint ventures	—				—				(671.7		)		(671.7		)

Distributions from joint ventures	—				—				722.9				722.9

Advances to related parties	—				—				(42.1		)		(42.1		)

Repayment of loan from related parties	—				—				25.2				25.2

Other, net	—				(5.7		)		(0.1		)		(5.8		)

Net cash used in continuing operations	—				(286.6		)		(227.6		)		(514.2		)

Net cash used in discontinued operations	—				—				(1.5		)		(1.5		)

Net cash used in investing activities	—				(286.6		)		(229.1		)		(515.7		)

Cash Flows From Financing Activities
Proceeds from long-term debt	1,188.00				—				—				1,188.00

Repayments of long-term debt	(1,334.2		)		(0.2		)		(55.8		)		(1,390.2		)
Payment of deferred financing costs	(22.8		)		—				—				(22.8		)

Dividends paid	(91.7		)		—				—				(91.7		)

Other, net	4.2				(1.6		)		(7.4		)		(4.8		)

Transactions with affiliates, net	332.3				(482.7		)		150.4				—

Net cash provided by (used in) financing activities	75.8				(484.5		)		87.2				(321.5		)

Net change in cash and cash equivalents	$	31.1			$	—			$	(145.9	)		$	(114.8	)

Cash and cash equivalents at beginning of year	269.6				0.3				288.9				558.8

Cash and cash equivalents at end of year	$	300.7			$	0.3			$	143			$	444

PEABODY ENERGY CORPORATION
SUPPLEMENTAL CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS


	Year Ended December 31, 2012
	Parent				Guarantor				Non-Guarantor				Consolidated
	Company				Subsidiaries				Subsidiaries
					(Dollars in millions)
Cash Flows From Operating Activities

Net cash provided by (used in) continuing operations	$	372			$	1,390.30			$	(162.5	)		$	1,599.80

Net cash used in discontinued operations	(3.4		)		(11.6		)		(69.7		)		(84.7		)
Net cash provided by (used in) operating activities	368.6				1,378.70				(232.2		)		1,515.10

Cash Flows From Investing Activities

Additions to property, plant, equipment and mine development	—				(237.4		)		(748.6		)		(986.0		)

Changes in accrued expenses related to capital expenditures	—				3.1				101.6				104.7

Federal coal lease expenditures	—				(276.5		)		—				(276.5		)

Investment in Prairie State Energy Campus	—				(10.7		)		—				(10.7		)

Proceeds from disposal of assets, net of notes receivable	—				70.1				77.8				147.9

Purchases of debt and equity securities	—				—				(46.7		)		(46.7		)

Proceeds from sales of debt and equity securities	—				—				46.4				46.4

Purchase of short-term investments	—				—				(4.8		)		(4.8		)

Contributions to joint ventures	—				—				(824.0		)		(824.0		)

Distributions from joint ventures	—				—				823				823

Advances to related parties	—				—				(148.0		)		(148.0		)

Repayment of loans from related parties	—				—				110.8				110.8

Other, net	—				(6.2		)		—				(6.2		)

Net cash used in continuing operations	—				(457.6		)		(612.5		)		(1,070.1		)

Net cash used in discontinued operations	—				(1.1		)		(20.9		)		(22.0		)

Net cash used in investing activities	—				(458.7		)		(633.4		)		(1,092.1		)

Cash Flows From Financing Activities

Proceeds from long-term debt	—				—				0.8				0.8

Repayments of long-term debt	(379.0		)		(0.4		)		(36.4		)		(415.8		)
Payment of deferred financing costs	(6.9		)		—				—				(6.9		)

Dividends paid	(91.9		)		—				—				(91.9		)

Common stock repurchase	(99.9		)		—								(99.9		)

Excess tax benefits related to share-based compensation	8.3				—				—				8.3

Acquisition of MCG Coal Holdings Pty Ltd noncontrolling interests	—				—				(49.8		)		(49.8		)

Other, net	1				—				(9.1		)		(8.1		)

Transactions with affiliates, net	186.2				(920.1		)		733.9				—

Net cash (used in) provided by financing activities	(382.2		)		(920.5		)		639.4				(663.3		)

Net change in cash and cash equivalents	$	(13.6	)		$	(0.5	)		$	(226.2	)		$	(240.3	)
Cash and cash equivalents at beginning of year	283.2				0.8				515.1				799.1

Cash and cash equivalents at end of year	$	269.6			$	0.3			$	288.9			$	558.8

Valuation_and_Qualifying_Accou1

Valuation and Qualifying Accounts Schedule II (Tables)	12 Months Ended
	Dec. 31, 2014
Valuation and Qualifying Accounts Disclosure [Line Items]
Summary of Valuation Allowance [Table Text Block]	SCHEDULE II — VALUATION AND QUALIFYING ACCOUNTS



	Description		Balance at		Charged to			Deductions(1)				Other				Balance
			Beginning of Period		Costs and Expenses											at End of Period
			(Dollars in millions)
	Year Ended December 31, 2014

	Reserves deducted from asset accounts:

	Advance royalty recoupment reserve		$	9.7	$	(0.2	)	$	(1.9	)	(2)	$	—			$	7.6

	Reserve for materials and supplies		7.4		(0.1		)	(2.7		)		—				4.6

	Allowance for doubtful accounts		7.4		1.5			(1.4		)		(1.7		)	(3)	5.8

	Tax valuation allowances		1,634.10		569.4			—				(1,034.5		)	(4)	1,169.00

	Year Ended December 31, 2013

	Reserves deducted from asset accounts:

	Advance royalty recoupment reserve		$	15.3	$	0.1		$	(5.7	)	(2)	$	—			$	9.7

	Reserve for materials and supplies		16		1.7			(10.3		)		—				7.4

	Allowance for doubtful accounts		13.7		4.3			(10.1		)		(0.5		)	(3)	7.4

	Tax valuation allowances		1,481.80		(29.4		)	—				181.7			(5)	1,634.10

	Year Ended December 31, 2012

	Reserves deducted from asset accounts:

	Advance royalty recoupment reserve		$	21.3	$	2.9		$	(9.0	)	(2)	$	0.1		(6)	$	15.3

	Reserve for materials and supplies		6.5		13.7			(4.2		)		—				16

	Allowance for doubtful accounts		17		(0.5		)	(0.7		)		(2.1		)	(3)	13.7

	Tax valuation allowances		79.8		521.5			(77.0		)	(7)	957.5			(8)	1,481.80


	(1)	Reserves utilized, unless otherwise indicated.

	(2)	Deductions to advance royalty recoupment reserve represents the termination of federal and state leases.

	(3)	Represents subsequent recovery of receivable amounts previously reserved.

	(4)	Includes the write-off of valuation allowance against deferred tax assets related to the Australian Minerals and Resource Rent Tax (MRRT) due to the repeal of that legislation in 2014, along with an increase in valuation allowance during the period reflected directly in "Accumulated other comprehensive loss" and the impact of the 2014 decrease in Australian dollar exchange rates.

	(5)	Related to the MRRT, as offset by the impact of the 2013 decrease in Australian dollar exchange rates.

	(6)	Balances transferred from other accounts or reserves recorded as part of a property transaction or acquisition.

	(7)	Deductions include write-off of loss carryforwards and reversal of related valuation allowances.

	(8)	Includes changes to valuation allowances primarily related to deferred tax assets acquired in business combinations and initial deferred tax assets resulting from the MRRT implemented in Australia in 2012.

Summary_of_Significant_Account3

Summary of Significant Accounting Policies Discussion (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary of Significant Accounting Policies Discussion (Textuals) [Abstract]
Period considered to treat short-term, highly liquid investments as cash equivalents	three months or less
Other-than-temporary impairment losses on marketable securities	$4.70	$21.50	$35.50
Other-than-temporary impairment losses on equity and cost method investments	0	43.2	39.4
Recognition of tax benefits from uncertain tax positions	greater than fifty percent likelihood of being realized upon ultimate settlement
Restructuring charges for voluntary and involuntary workforce reductions	15.7	11.9
Asset impairment charges related to long-lived assets	149.7	463.6	833.6
Foreign currency remeasurement (loss) gains	-1.3	34.1	4.8
Foreign currency translation adjustment	($41)	($92.70)	$19.10
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	Shorter of Useful Life or Remaining Life of Lease
Interest In Middlemount Coal Pty Limited [Member]
Property, Plant and Equipment [Line Items]
Ownership percentage of equity method investment	50.00%
Minimum [Member] \| Buildings and improvements [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	1
Minimum [Member] \| Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	1
Maximum [Member] \| Buildings and improvements [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	37
Maximum [Member] \| Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	37

Asset_Impairment_and_Mine_Clos2

Asset Impairment and Mine Closure Costs (Details) (USD $)	3 Months Ended			12 Months Ended			3 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2012
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of long-lived assets related to mine closures						$26.90
Acceleration of asset retirement obligations						7.1
Employee termination benefits						6.7
Other charges related to mine closures						4.3
Long-lived assets				149.7	463.6	806.7
Equity method investment					43.2
Marketable securities				4.7	21.5	35.5
Cost method investments						39.4
Other asset impairment charges						2.4
Total asset impairment and mine closure costs	154.4	506.8	21.5	154.4	528.3	929
Asset realization risk	124.1			124.1
Additional asset impairment charge deemed necessary for assets at risk				0
Australian Mining [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of long-lived assets related to mine closures						0
Acceleration of asset retirement obligations						0
Employee termination benefits						0
Other charges related to mine closures						0
Long-lived assets				78.6	390.8	806.7
Equity method investment					0
Marketable securities				0	0	0
Cost method investments						0
Other asset impairment charges						0
Total asset impairment and mine closure costs				78.6	390.8	806.7
Western U.S. Mining [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of long-lived assets related to mine closures						0
Acceleration of asset retirement obligations						0
Employee termination benefits						0
Other charges related to mine closures						0
Long-lived assets				2.7		0
Marketable securities				0		0
Cost method investments						0
Other asset impairment charges						2.4
Total asset impairment and mine closure costs				2.7		2.4
Midwestern U.S. Mining [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of long-lived assets related to mine closures						26.9
Acceleration of asset retirement obligations						7.1
Employee termination benefits						6.7
Other charges related to mine closures						4.3
Long-lived assets						0
Marketable securities						0
Cost method investments						0
Other asset impairment charges						0
Total asset impairment and mine closure costs						45
Corporate and Other [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of long-lived assets related to mine closures						0
Acceleration of asset retirement obligations						0
Employee termination benefits						0
Other charges related to mine closures						0
Long-lived assets				68.4	72.8	0
Equity method investment					43.2
Marketable securities				4.7	21.5	35.5
Cost method investments						39.4
Other asset impairment charges						0
Total asset impairment and mine closure costs				73.1	137.5	74.9
Willow Lake Mine [Member] \| Midwestern U.S. Mining [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Total asset impairment and mine closure costs							45
Eastern US Coal Reserves [Member] \| Corporate and Other [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Long-lived assets					66.3
Third Party Mined Coal Reserves [Member] \| Corporate and Other [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Long-lived assets					$6.50
Middlemount Mine [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Equity method investment, ownership percentage	50.00%	50.00%		50.00%	50.00%

Discontinued_Operations_Detail

Discontinued Operations (Details) (USD $)	3 Months Ended	12 Months Ended			3 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	31-May-14
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss from discontinued operations before income taxes		($23.80)	($329.70)	($163.90)
Income tax (provision) benefit		-4.4	103.1	59.7
Loss from discontinued operations, net of income taxes		-28.2	-226.6	-104.2
Total revenues			136.5	229.1
Change in fair value of credit support provided to Patriot	34.1	34.1
Asset Retirement Obligation	752.5	752.5	712.8	687.5	712.8
Potential cash proceeds from sale of property held-for-sale						70
Impairment of long-lived assets				26.9
Other current assets	0.3	0.3	38.6		38.6
Investments and other assets	16.3	16.3	47.4		47.4
Total assets classified as discontinued operations	16.6	16.6	86		86
Accounts payable and accrued expenses	12.5	12.5	133.1		133.1
Other noncurrent liabilities	109.8	109.8	84.9		84.9
Total liabilities classified as discontinued operations	122.3	122.3	218		218
Settlement charges related to the Patriot bankruptcy reorganization [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss from disposition of discontinued operations, before income tax			98
Loss from disposition of discontinued operations, net of tax			61.8		61.8
Air Quality [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss from disposition of discontinued operations, before income tax				116.7
Loss from disposition of discontinued operations, net of tax				75
Impairment of long-lived assets				108.9
Impairment of long-lived assets to be disposed of (after tax)				68.8
Wilkie Creek [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss from disposition of discontinued operations, before income tax			167.4
Loss from disposition of discontinued operations, net of tax			117.2
Restructuring Reserve	0.8	0.8	36.6		36.6
Restructuring Reserve, Accrual Adjustment		-5.2
Restructuring and Related Cost, Incurred Cost		-30.9
Restructuring Reserve, Translation and Other Adjustment		0.3
Asset Retirement Obligation	47.5	47.5
Gain (Loss) on Contract Termination		4.6
Impairment of long-lived assets			107
Impairment of long-lived assets to be disposed of (after tax)			74.9
Contractual Liabilities [Member] \| Wilkie Creek [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Restructuring Reserve	0.8	0.8	33.9		33.9
Restructuring Reserve, Accrual Adjustment		-5
Restructuring and Related Cost, Incurred Cost		-28.4
Restructuring Reserve, Translation and Other Adjustment		0.3
Other Exit Costs [Member] \| Wilkie Creek [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Restructuring Reserve	0	0	2.7		2.7
Restructuring Reserve, Accrual Adjustment		-0.2
Restructuring and Related Cost, Incurred Cost		-2.5
Restructuring Reserve, Translation and Other Adjustment		$0

Inventories_Details

Inventories (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Inventory [Line Items]
Materials and supplies	$143.60	$166.80
Raw coal	115	122.6
Saleable coal	147.9	217.3
Total	$406.50	$506.70

Inventories_Details_Textuals_D

Inventories Details Textuals (Details) (Reserve for materials and supplies [Member], USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reserve for materials and supplies [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Materials and supplies reserves	$4.60	$7.40	$16	$6.50

Investments_Details_1

Investments (Details 1) (USD $)	12 Months Ended			3 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Jun. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$61.80	$65.70		$61.80
Available-for-sale Securities, Gross Unrealized Gain	0	1.4
Available-for-sale Securities, Gross Unrealized Loss	0	-0.1
Available-for-sale Securities	61.8	67		61.8
Proceeds from sale of available-for-sale securities	13.5	22.9	17.2
Net gains on sales and maturities	0	0.2	0.1
Proceeds from Sale and Maturity of Marketable Securities	13.5	22.9	46.4
Other-than-temporary impairment losses on marketable securities	4.7	21.5	35.5
Purchases of short-term investments	0	0	4.8
Maturity of short-term investments	0	4.8	0
Held-to-maturity securities	0	0		0
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, at cost due within one year	11.2			11.2
Available-for-sale securities, at fair value due within one year	11.2			11.2
Available-for-sale securities, at cost due in one to five years	44.4			44.4
Available-for-sale securities, at fair value due in one to five years	44.4			44.4
Available-for-sale securities, at cost	55.6			55.6
Available-for-sale securities, at fair value	55.6			55.6
Current [Member] \| Domestic Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	11.2	2.4		11.2
Available-for-sale Securities, Gross Unrealized Gain	0	0
Available-for-sale Securities, Gross Unrealized Loss	0	0
Available-for-sale Securities	11.2	2.4		11.2
Current [Member] \| US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis		2.8
Available-for-sale Securities, Gross Unrealized Gain		0
Available-for-sale Securities, Gross Unrealized Loss		0
Available-for-sale Securities		2.8
Non Current [Member] \| Domestic Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	12.4	20.8		12.4
Available-for-sale Securities, Gross Unrealized Gain	0	0.1
Available-for-sale Securities, Gross Unrealized Loss	0	0
Available-for-sale Securities	12.4	20.9		12.4
Non Current [Member] \| Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	6.2	10.9		6.2
Available-for-sale Securities, Gross Unrealized Gain	0	1.3
Available-for-sale Securities, Gross Unrealized Loss	0	0
Available-for-sale Securities	6.2	12.2		6.2
Non Current [Member] \| US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	32	28.8		32
Available-for-sale Securities, Gross Unrealized Gain	0	0
Available-for-sale Securities, Gross Unrealized Loss	0	-0.1
Available-for-sale Securities	32	28.7		32
Newcastle Coal Infrastructure Group [Domain]
Schedule of Available-for-sale Securities [Line Items]
Proceeds from Sale and Maturity of Marketable Securities			29.2
Realized losses on sale securities			0.2
NCIG Securities	0	0		0
Interest In Peabody-Winsway Resources B.V. [Member]
Schedule of Available-for-sale Securities [Line Items]
Other-than-temporary impairment losses on marketable securities				$4.70	$21.50	$35.50

Investments_Details_2

Investments (Details 2) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Equity method investments	$65.30	$180.10
Loss from equity affiliates	107.6	40.2	61.2
Other-than-temporary impairment losses on equity method investments		43.2
Middlemount Mine [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Summarized Financial Information, Revenue	165	157	118
Change in deferred tax asset valuation allowance related to equity affiliates	52.3
Equity Method Investment, Summarized Financial Information, Current Assets	27.8	30.9
Equity Method Investment, Summarized Financial Information, Noncurrent Assets	424.4	525.3
Equity Method Investment, Summarized Financial Information, Current Liabilities	382.9	365.6
Equity Method Investment, Summarized Financial Information, Noncurrent Liabilities	11.3	17.2
Interest In Middlemount Coal Pty Limited [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	58	173.4
Loss from equity affiliates	98.5	33.5	52.1
Equity method investment, ownership percentage	50.00%
Other-than-temporary impairment losses on equity method investments		43.2
Remaining unamortized difference	96.1
Other Equity Method Investments [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	7.3	6.7
Loss from equity affiliates	$9.10	$6.70	$9.10
Middlemount Mine [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	50.00%	50.00%

Derivatives_and_Fair_Value_Mea3

Derivatives and Fair Value Measurements (Details)

12 Months Ended

In Millions, unless otherwise specified

Dec. 31, 2014

Nov. 30, 2012

Dec. 31, 2014

Dec. 31, 2015

Interest rate swaps [Member]

Foreign currency forward contracts [Member]

Diesel fuel hedge contracts [Member]

Explosives hedge contracts [Member]

Scenario, Forecast [Member]

USD ($)

AUD

Cash flow hedges [Member]

Fair value hedge [Member]

Economic hedge [Member]

Previously monetized hedge contracts [Member]

USD ($)

Cash flow hedges [Member]

Fair value hedge [Member]

Economic hedge [Member]

MMbtu

Foreign currency forward contracts [Member]

Diesel fuel hedge contracts [Member]

AUD

gal

USD ($)

Company's foreign currency and commodity positions by Year of Maturity and Account Classification

Total (A$ millions)

3,191.10

1,900

2015 (A$ millions)

1,661.10

2016 (A$ millions)

1,007

2017 (A$ millions)

523

Total (gallons/MMbtu)

201,500,000

2015 (gallons)

103,400,000

2016 (gallons)

67,500,000

2017 (gallons)

30,600,000

Fair Value Net Liability

-410

-167.1

Net loss to be reclassified from accumulated other comprehensive loss to earnings over the next 12 months

$226

$100

Timing differences between the hedge settlement and the purchase transaction

Less than a day and up to a maximum of 30 days

Derivatives_and_Fair_Value_Mea4

Derivatives and Fair Value Measurements (Details 1)

12 Months Ended

In Millions, unless otherwise specified

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

USD ($)

Gains realized on previously monetized foreign currency cash flow hedges [Member]

Commodity swap contracts [Member]

Foreign currency forward contracts [Member]

USD ($)

Operating costs and expenses [Member]

AUD

Fair value hedge [Member]

Cash flow hedges [Member]

Economic hedge [Member]

Operating costs and expenses [Member]

Cash flow hedges [Member]

AUD

Cash flow hedges [Member]

USD ($)

Derivative Instruments, Gain (Loss) [Line Items]

Monetization of foreign currency hedge positions

$151.80

Derivative, Notional Amount

3,191.10

Gain (loss) recognized in other comprehensive income on derivative (effective portion)

-295.4

-585.3

162.5

-194.5

12.5

14.5

-100.9

-597.8

148

Gain (loss) reclassified from other comprehensive income into income (effective portion)

-47.9

[1]

174.3

400

-20.6

11.9

48.3

-27.3

[1]

162.4

351.7

Gain (loss) reclassified from other comprehensive income into income (ineffective portion)

-1.7

-0.5

-4.7

-1.7

-0.5

-4.7

Gain reclassified to earnings for previously monetized foreign currency forward contracts

$136.90

[1]

Includes the reclassification from "Accumulated other comprehensive loss" into earnings of $136.9 million of previously unrecognized gains on foreign currency cash flow hedge contracts monetized in the fourth quarter of 2012.

Derivatives_and_Fair_Value_Mea5

Derivatives and Fair Value Measurements (Details 2)

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Nov. 30, 2012

In Millions, unless otherwise specified

Foreign currency forward contracts [Member]

Gross amounts of recognized assets/liabilities

Gross amounts offset in the consolidated balance sheet

Net amounts presented in the consolidated balance sheet

Derivatives not offset in the consolidated balance sheet

Net amount of derivatives not offset

Previously monetized hedge contracts [Member]

AUD

USD ($)

Commodity swap contracts [Member]

Foreign currency forward contracts [Member]

USD ($)

Commodity swap contracts [Member]

Foreign currency forward contracts [Member]

USD ($)

Commodity swap contracts [Member]

Foreign currency forward contracts [Member]

USD ($)

Foreign currency forward contracts [Member]

USD ($)

AUD

Derivative [Line Items]

Derivative, Notional Amount

3,191.10

1,900

Derivative asset, current

8.7

-2.3

6.4

-5

[1]

1.4

Derivative asset, noncurrent

2.8

0.2

-1.1

-0.9

-0.2

1.9

-1.3

[1]

0.6

Derivative liability, current

215.8

3.9

211.9

-1.9

341.1

[2]

213.9

100.1

[2]

241

[2]

211.9

-5.4

[1]

208.5

Derivative liability, noncurrent

$264.10

$2.50

$261.60

($1.50)

($1.30)

($0.20)

$236

[2]

$262.60

$67

[2]

$1.20

$169

[2]

$261.40

($0.90)

[1]

$261.70

[1]

Adjustments relate to the further netting of derivative contracts with a common counterparty across the Company's foreign currency, diesel fuel and explosives hedging strategy derivative contract portfolios that would be contractually enforceable in the event of default.

[2]

All commodity swap contracts and foreign currency forward contracts were in a liability position as of December 31, 2014.

Derivatives_and_Fair_Value_Mea6

Derivatives and Fair Value Measurements (Details 3) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair value of asset (liability) positions measured on a recurring basis
Investments in debt and equity securities	$61.80	$67
Foreign currency forward contracts [Member]
Fair value of asset (liability) positions measured on a recurring basis
Derivative assets (liabilities), at fair value, net	-410
Diesel fuel hedge contracts [Member]
Fair value of asset (liability) positions measured on a recurring basis
Derivative assets (liabilities), at fair value, net	-167.1
Fair Value, Measurements, Recurring [Member]
Fair value of asset (liability) positions measured on a recurring basis
Investments in debt and equity securities	61.8	67
Total net financial assets (liabilities)	-515.3	-401.2
Fair Value, Measurements, Recurring [Member] \| Foreign currency forward contracts [Member]
Fair value of asset (liability) positions measured on a recurring basis
Derivative assets (liabilities), at fair value, net	-410	-473.3
Fair Value, Measurements, Recurring [Member] \| Commodity swap contracts [Member]
Fair value of asset (liability) positions measured on a recurring basis
Derivative assets (liabilities), at fair value, net	-167.1	5.1
Fair Value, Measurements, Recurring [Member] \| Level 1 [Member]
Fair value of asset (liability) positions measured on a recurring basis
Investments in debt and equity securities	26.1	28.8
Total net financial assets (liabilities)	26.1	28.8
Fair Value, Measurements, Recurring [Member] \| Level 1 [Member] \| Foreign currency forward contracts [Member]
Fair value of asset (liability) positions measured on a recurring basis
Derivative assets (liabilities), at fair value, net	0	0
Fair Value, Measurements, Recurring [Member] \| Level 1 [Member] \| Commodity swap contracts [Member]
Fair value of asset (liability) positions measured on a recurring basis
Derivative assets (liabilities), at fair value, net	0	0
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member]
Fair value of asset (liability) positions measured on a recurring basis
Investments in debt and equity securities	35.7	38.2
Total net financial assets (liabilities)	-541.4	-430
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member] \| Foreign currency forward contracts [Member]
Fair value of asset (liability) positions measured on a recurring basis
Derivative assets (liabilities), at fair value, net	-410	-473.3
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member] \| Commodity swap contracts [Member]
Fair value of asset (liability) positions measured on a recurring basis
Derivative assets (liabilities), at fair value, net	-167.1	5.1
Fair Value, Measurements, Recurring [Member] \| Level 3 [Member]
Fair value of asset (liability) positions measured on a recurring basis
Investments in debt and equity securities	0	0
Total net financial assets (liabilities)	0	0
Fair Value, Measurements, Recurring [Member] \| Level 3 [Member] \| Foreign currency forward contracts [Member]
Fair value of asset (liability) positions measured on a recurring basis
Derivative assets (liabilities), at fair value, net	0	0
Fair Value, Measurements, Recurring [Member] \| Level 3 [Member] \| Commodity swap contracts [Member]
Fair value of asset (liability) positions measured on a recurring basis
Derivative assets (liabilities), at fair value, net	$0	$0

Derivatives_and_Fair_Value_Mea7

Derivatives and Fair Value Measurements (Details 4) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	$0	$0
Level 1 to Level 2 transfers	0	0
Level 2 to Level 1 transfers	0	0
Long-term debt, carrying value	5,986.80	6,002.40
Carrying amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, carrying value	5,986.80	6,002.40
Estimated fair value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	$5,227.90	$6,167.50

Coal_Trading_Details

Coal Trading (Details) (Coal Trading [Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Trading revenue
Trading revenue	$58.40		$66		$151.80
Coal trading derivative instruments and balance sheet offsetting disclosures:
Assets from coal trading activities, gross amounts of recognized assets	342.5		418.8
Liabilities from coal trading activities, gross amounts of recognized liabilities	-285		-332.7
Assets and (liabilities) from coal trading activities, net amounts recognized before the application of variation margin	57.5		86.1
Gross amounts of coal trading liabilities offset against associated coal trading assets	-248.3		-324.7
Gross amounts of coal trading assets offset against associated coal trading liabilities	248.3		324.7
Net coal trading assets (liabilities) offset against associated (liabilities) assets	0		0
Variation margin held offset against assets from coal trading activities	-36.6		-58
Variation margin posted offset against liabilities from coal trading activities	4		1.9
Net variation margin (held) posted	-32.6	[1]	-56.1	[1]
Assets from coal trading activities, net	57.6		36.1
Liabilities from coal trading activities, net	-32.7		-6.1
Net assets (liabilities) from coal trading activities	24.9		30
Commodity futures, swaps and options [Member]
Trading revenue
Trading revenue	92.3		183.9		159.9
Physical commodity purchase / sale contracts [Member]
Trading revenue
Trading revenue	-33.9		-117.9		-8.1
Cash Flow Hedging [Member]
Coal trading derivative instruments and balance sheet offsetting disclosures:
Net variation margin (held) posted	$0		($42)

[1]	None and $42 million of the net variation margin held at December 31, 2014 and 2013, respectively, related to cash flow hedges.

Coal_Trading_Details_1

Coal Trading (Details 1) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2015
Coal Trading (Textuals) [Abstract]
Fair value hierarchy transfers from Level 1 to Level 2	$0		$0
Fair value hierarchy transfers from Level 2 to Level 1	0		0
Coal Trading [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Fair Value, Amount Offset Against Collateral, Net	32.6	[1]	56.1	[1]
Changes in the Company's recurring Level 3 net financial assets
Beginning of year	2.1		5.2		8.7
Total gains (realized/unrealized):
Included in earnings	6.7		0.3		17.5
Settlements	-6.7		-3.4		-21
End of year	2.1		2.1		5.2
Changes in unrealized gains (losses) relating to Level 3 net financial assets held both at the beginning and the end of the period
Changes in unrealized gains (losses)	2.1	[2]	-0.4	[2]	4.1	[2]
Schedule of future realization of trading portfolio
2015	77.00%
2016	19.00%
2017	3.00%
2018	1.00%
Percentage of trading portfolio expiration, total	100.00%
Coal Trading (Textuals) [Abstract]
Cash flow hedge derivative instrument assets at fair value	44.3		62.9
Gain on discontinuation of cash flow hedge due to forecasted transaction probable of not occurring	2
Fair value hierarchy transfers from Level 1 to Level 2	0		0		0
Fair value hierarchy transfers from Level 2 to Level 1	0		0		0
Fair value hierarchy transfers into (out of) Level 3	0		0		0
Fair Value, Measurements, Recurring [Member] \| Coal Trading [Member]
Fair value coal trading net assets (liabilities) measured on recurring basis
Commodity futures, swaps and options	32.4		26.4
Physical commodity purchase/sale contracts	-7.5		3.6
Total net financial assets (liabilities)	24.9		30
Fair Value, Measurements, Recurring [Member] \| Level 1 [Member] \| Coal Trading [Member]
Fair value coal trading net assets (liabilities) measured on recurring basis
Commodity futures, swaps and options	-0.2		0
Physical commodity purchase/sale contracts	0		0
Total net financial assets (liabilities)	-0.2		0
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member] \| Coal Trading [Member]
Fair value coal trading net assets (liabilities) measured on recurring basis
Commodity futures, swaps and options	32.6		26.4
Physical commodity purchase/sale contracts	-9.6		1.5
Total net financial assets (liabilities)	23		27.9
Fair Value, Measurements, Recurring [Member] \| Level 3 [Member] \| Coal Trading [Member]
Fair value coal trading net assets (liabilities) measured on recurring basis
Commodity futures, swaps and options	0		0
Physical commodity purchase/sale contracts	2.1		2.1
Total net financial assets (liabilities)	2.1		2.1
Cash Flow Hedging [Member] \| Coal Trading [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Fair Value, Amount Offset Against Collateral, Net	0		42
Minimum [Member] \| Coal Trading [Member]
Coal Trading (Textuals) [Abstract]
Quality adjustment Level 3 unobservable inputs as percentage of overall valuation	8.00%
Location differentials Level 3 unobservable input as percentage of overall valuation	19.00%
Maximum [Member] \| Coal Trading [Member]
Coal Trading (Textuals) [Abstract]
Quality adjustment Level 3 unobservable inputs as percentage of overall valuation	12.00%
Location differentials Level 3 unobservable input as percentage of overall valuation	19.00%
Weighted Average [Member] \| Coal Trading [Member]
Coal Trading (Textuals) [Abstract]
Quality adjustment Level 3 unobservable inputs as percentage of overall valuation	9.00%
Location differentials Level 3 unobservable input as percentage of overall valuation	19.00%
Scenario, Forecast [Member] \| Coal Trading [Member]
Coal Trading (Textuals) [Abstract]
Expected amount of gains to be realized over the next 12 months in accumulated other comprehensive loss							$45

[1]	None and $42 million of the net variation margin held at December 31, 2014 and 2013, respectively, related to cash flow hedges.
[2]	Within the consolidated statements of operations and consolidated statements of comprehensive income for the periods presented, unrealized gains and losses from LevelB 3 items are combined with unrealized gains and losses on positions classified in LevelB 1 or 2, as well as other positions that have been realized during the applicable periods.

Coal_Trading_Details_2

Coal Trading (Details 2) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
	credit_rating_notch		Dec. 31, 2013
Concentration Risk [Line Items]
Number of major credit rating agencies that adjusted corporate credit rating	3
Severity of credit rating downgrade	1
Coal Trading [Member]
Concentration Risk [Line Items]
Potential collateralization that may be requested by counterparties related to material adverse event	31		$7
Margin posted to counterparties related to material adverse event	0		0
Additional potential collateral requirements for a credit downgrade	0		0
Margin posted to counterparties related to credit rating	0		0
Net variation margin held	-32.6	[1]	-56.1	[1]
Initial margin posted	15.2		19.6
Margin in excess of the exchange-required variation and initial margin	6.1		$1
External Credit Rating, Investment Grade [Member] \| Credit Concentration Risk [Member] \| Coal Trading Positions [Member] \| Coal Trading [Member]
Concentration Risk [Line Items]
Credit concentration risk percentage	75.00%
External Credit Rating, Non Investment Grade [Member] \| Credit Concentration Risk [Member] \| Coal Trading Positions [Member] \| Coal Trading [Member]
Concentration Risk [Line Items]
Credit concentration risk percentage	10.00%
Non Rated [Member] \| Credit Concentration Risk [Member] \| Coal Trading Positions [Member] \| Coal Trading [Member]
Concentration Risk [Line Items]
Credit concentration risk percentage	15.00%

[1]	None and $42 million of the net variation margin held at December 31, 2014 and 2013, respectively, related to cash flow hedges.

Financing_Receivables_Details

Financing Receivables (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	$15.40	$15.70	$24.50
Middlemount Mine [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equity method investment, ownership percentage	50.00%
Basis spread over Australian Bank Bill Swap Reference Rate	3.50%
Interest income	4.8	6.4
Additional interest income under a full accrual basis	6.4	5.8
Codrilla Mine Project [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of ownership before selldown				85.00%
Percentage of agreed sale price as final installment payment due	40.00%
Adjustment to discounted value of note receivable		1.6
Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, net	0	0.1
Investments and other assets	347.2	351.7
Total financing receivables	347.2	351.8
Financing Receivable [Member] \| Middlemount Mine [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investments and other assets	319.6	323.2
Financing Receivable [Member] \| Codrilla Mine Project [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investments and other assets	$27.60	$28.50
Middlemount Mine [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equity method investment, ownership percentage	50.00%	50.00%
Coppabella, Moorvale, and Codrilla Mines [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of undivided interests acquired				73.30%

Property_Plant_Equipment_and_M2

Property, Plant, Equipment and Mine Development (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant, Equipment and Mine Development[Line Items]
Land and coal interests	$11,021,100,000	$11,024,100,000
Buildings and improvements	1,569,100,000	1,525,400,000
Machinery and equipment	2,685,700,000	2,777,500,000
Less: accumulated depreciation, depletion and amortization	-4,698,600,000	-4,244,500,000
Total, net	10,577,300,000	11,082,500,000	11,801,700,000
Coal reserves	6,200,000,000	6,300,000,000
Acquired interest in mineral rights	1,300,000,000	1,300,000,000
Mineral rights and advanced royalties	5,000,000,000	5,100,000,000
Coal reserves not subject to depletion	2,100,000,000	2,300,000,000
Coal reserves held by fee ownership [Member]
Property, Plant, Equipment and Mine Development[Line Items]
Coal reserves	$1,200,000,000	$1,200,000,000

Income_Taxes_Details

Income Taxes (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Loss from continuing operations before income taxes
U.S.	$268.90	$220.60	$1,049.10
Non-U.S.	-816.8	-954.9	-1,257.70
Loss from continuing operations before income taxes	($547.90)	($734.30)	($208.60)

Income_Taxes_Details_1

Income Taxes (Details 1) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current:
U.S. federal	$27.10	($47.90)	$116.80
Non-U.S.	-61.1	38.4	127.6
State	3.3	-4.7	12.2
Total current	-30.7	-14.2	256.6
Deferred:
U.S. federal	111	4.8	-32.7
Non-U.S.	122.3	-440.3	28.8
State	-1.4	1.4	9.6
Total deferred	231.9	-434.1	5.7
Total income tax provision (benefit)	$201.20	($448.30)	$262.30

Income_Taxes_Details_2

Income Taxes (Details 2) (USD $)	3 Months Ended								12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of the expected statutory federal income tax provision to the Company's actual income tax provision
Expected income tax benefit at U.S. federal statutory rate									($191.70)	($257)	($73)
Changes in valuation allowance, income tax									569.4	-29.4	521.5
Changes in tax reserves									-81.5	8.8	24.5
Excess depletion									-65.3	-72.7	-69.4
Foreign earnings repatriation									-71.4	0	0
Foreign earnings provision differential									28.8	62.7	-59.6
General business tax credits									-19.2	-18.9	-17.4
Minerals resource rent tax, net of federal tax									16.1	-87.4	77.2
Remeasurement of foreign income tax accounts	1.2	-1.2	-1.3	-1.4	-6.2	-2.6	-37.1	1.6	-2.7	-44.3	7.9
State income taxes, net of federal tax benefit									-2.3	-0.2	-1.1
Capital loss									0	0	-118.1
Other, net									21	-9.9	-30.2
Total income tax provision (benefit)									$201.20	($448.30)	$262.30

Income_Taxes_Details_3

Income Taxes (Details 3) (USD $)	Dec. 31, 2014		Dec. 31, 2013
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Deferred tax assets:
Tax credits and loss carryforwards	$1,723.50		$1,558
Minerals resource rent tax	0		993.2
Accrued postretirement benefit obligations	372.3		309.9
Asset retirement obligations	167		141.6
Employee benefits	70.7		88.5
Payable to voluntary employee beneficiary association for certain Patriot retirees	79.2	[1]	84.4	[1]
Hedge activities	44.2		0
Environmental contingencies	29.9		23.6
Deferred revenue	29.1		3.2
Financial guarantees	16.9		16.9
Workers' compensation obligations	6.2		10.4
Other	50.5		31.5
Total gross deferred tax assets	2,589.50		3,261.20
Deferred tax liabilities:
Property, plant, equipment and mine development, principally due to differences in depreciation, depletion and asset impairments	1,223.40		1,322.30
Unamortized discount on Convertible Junior Subordinated Debentures	131		131.8
Hedge activities	0		11.4
Investments and other assets	73.4		82
Other	1.1		46.3
Total gross deferred tax liabilities	1,428.90		1,593.80
Valuation allowance, income tax	-1,169		-656.4
Valuation allowance, mineral resource rent tax	0		-977.7
Net deferred tax (liability) asset	-8.4		33.3
Deferred taxes are classified as follows:
Current deferred income taxes	80		66.4
Noncurrent deferred income taxes	-88.4		-33.1
Net deferred tax (liability) asset	($8.40)		$33.30

[1]	Refer to Note 25. "Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation" herein for additional details related to this transaction.

Income_Taxes_Details_4

Income Taxes (Details 4) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of the beginning and ending amount of gross unrecognized tax benefits
Balance at beginning of period	$143.90	$122.80	$119.60
Additions for current year tax positions	12	6.3	17.4
Additions for prior year tax positions	0	63.8	31.9
Reductions for settlements with tax authorities	-111.4	0	-46.1
Reductions for expirations of statutes of limitations	0	-49	0
Balance at end of period	$44.50	$143.90	$122.80

Income_Taxes_Details_5

Income Taxes (Details 5) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary of Company's tax payments
Tax payments	($16.70)	$81.90	$130.50
Domestic Tax Authority [Member]
Summary of Company's tax payments
Tax payments	-7.7	-0.8	63
State and Local Jurisdiction [Member]
Summary of Company's tax payments
Tax payments	-6.8	2.9	11.8
Foreign Tax Authority [Member]
Summary of Company's tax payments
Tax payments	($2.20)	$79.80	$55.70

Income_Taxes_Details_Textuals

Income Taxes (Details Textuals) (USD $)	12 Months Ended			3 Months Ended				6 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2014	Dec. 31, 2015
Income Taxes (Textuals) [Abstract]
Alternative minimum tax credits	$290.30			$290.30
Foreign tax credits	147.9			147.9
General business credits	89.9			89.9
State net operating loss carryforwards	41			41
Foreign loss carryforwards included in Company's tax credits and loss carryforwards	1,103.30			1,103.30
Valuation allowance reserve for U.S. capital losses, state NOLs, foreign NOLs and certain foreign deferred tax assets	-1,169	-656.4		-1,169
Minerals resource rent tax, net of federal tax	16.1	-87.4	77.2
MRRT market value allowance deferred tax asset	993.2			993.2
Valuation allowance, minerals resource rent tax	0	-977.7		0
Change in unrecognized tax benefit	99.4
Net unrecognized tax benefits	40.9	140.5		40.9
Accrued interest related to unrecognized tax benefits included in income tax provision	-8	-36	21.2
Accrued interest related to uncertain tax positions	3.4	11.4		3.4
Valuation allowance minerals resource rent tax	977.7			977.7
Undistributed Earnings of Foreign Subsidiaries	0			0
Australia Deferred Tax Assets [Member]
Income Taxes (Textuals) [Abstract]
Valuation Allowance, Deferred Tax Asset, Change in Amount	289.3			90.4	80.6	75.7	42.6
US Deferred Tax Assets [Member]
Income Taxes (Textuals) [Abstract]
Capital loss	51.1			51.1
Valuation Allowance, Deferred Tax Asset, Change in Amount	351.2			280.1
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	280.1
Other Comprehensive Income (Loss), Tax	71.1
Australian Minerals and Resource Rent Tax [Member]
Income Taxes (Textuals) [Abstract]
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability					70.1			54
Scenario, Forecast [Member]
Income Taxes (Textuals) [Abstract]
Tax adjustments, settlements, and unusual provisions									$28.60

Income_Taxes_Details_6

Income Taxes (Details 6) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Accounts payables and accrued expenses	$0	$20.30
Deferred income taxes	6.2	90.3
Other noncurrent liabilities	34.7	29.9
Net unrecognized tax benefits	40.9	140.5
Gross unrecognized tax benefits	$44.50	$143.90	$122.80	$119.60

Accounts_Payable_and_Accrued_E2

Accounts Payable and Accrued Expenses (Details) (USD $)	Dec. 31, 2014		Dec. 31, 2013
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Accounts payable and accrued expenses [Line Items]
Trade accounts payable	$461.70		$483
Commodity and foreign currency hedge contracts	341.1		213.9
Other accrued expenses	298.8		267.3
Accrued payroll and related benefits	268.7		248
Accrued taxes other than income	175.3		223.5
Payable to voluntary employee beneficiary association for certain Patriot retirees	75	[1]	20	[1]
Accrued royalties	61.5		67.1
Accrued interest	48.4		47.9
Asset Retirement Obligation, Current	30.2		21
Accrued environmental cleanup-related costs	19.4		18.3
Workers' compensation obligations	10.9		10
Income taxes payable	3.3		3.8
Accrued health care insurance	2.4		7.1
Liabilities associated with discontinued operations	12.5		133.1
Total accounts payable and accrued expenses	$1,809.20		$1,764

[1]	Refer to Note 25. "Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation" herein for additional details related to this transaction.

Debt_Debt_Schedule_Details

Debt Debt Schedule (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Sep. 24, 2013
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Sep. 24, 2013
Debt Instrument [Line Items]
Capital lease obligations	$22.20	$30.50
Other long-term debt	1.2	0.9
Debt and capital lease obligations	5,986.80	6,002.40
Term Loan Facility [Member]
Debt Instrument [Line Items]
Long-term Debt			301.8
2011 Term Loan Facility [Member]
Debt Instrument [Line Items]
Long-term Debt			862.5
2013 Term Loan Facility [Member]
Debt Instrument [Line Items]
Long-term Debt	1,175.10	1,185.40
7.375% Senior Notes Member
Debt Instrument [Line Items]
Long-term Debt	650	650
6.00% Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate - percentage	6.00%
Long-term Debt	1,518.80	1,518.80
6.50% Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt	650	650
6.25% Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate - percentage	6.25%
Long-term Debt	1,339.60	1,339.60
7.875% Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate - percentage	7.88%
Long-term Debt	247.6	247.5
Convertible Junior Subordinated Debentures [Member]
Debt Instrument [Line Items]
Long-term Debt	$382.30	$379.70

Debt_Credit_Agreement_Details

Debt Credit Agreement (Details) (USD $)	12 Months Ended
Debt Credit Agreement (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 24, 2013	Feb. 05, 2015
Line of Credit Facility [Line Items]
Proceeds from long-term debt	$1,100,000	$1,188,000,000	$800,000
Letters of credit outstanding				94,700,000
2011 Term Loan Facility [Member]
Line of Credit Facility [Line Items]
Previous term loan facility balance				862,500,000
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	1,650,000,000
Long-term debt, percentage bearing variable interest, percentage rate	2.25%
Capitalized debt issuance costs				18,300,000
Line of credit facility, dividend restrictions	500
Line of credit facility annual dividend threshold	27.5
Letters of credit outstanding	114,900,000
Line of credit facility, remaining borrowing capacity	1,535,100,000
Interest rate at end of period	2.42%
Line of credit facility general restricted payments	100
Term Loan Facility [Member]
Line of Credit Facility [Line Items]
Previous term loan facility balance				301,800,000
Write-off of debt issuance costs	11,500,000
2013 Term Loan Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	1,200,000,000
Proceeds from long-term debt	1,190,000,000
Debt instrument, unamortized discount	12,000,000
Previous term loan facility balance	1,175,100,000	1,185,400,000
Capitalized debt issuance costs				10,100,000
Term loan facility percentage of periodic repayment	0.25%
Loan prepayment threshold for certain asset sale net proceeds	500
Domestic unrestricted subsidiary or domestic joint venture percentage	50.00%
Aggregate net proceeds from domestic unrestricted subsidiaries or domestic joint venture	200
Interest rate at end of period	4.25%
2013 Credit Facility [Member]
Line of Credit Facility [Line Items]
Percent of company stock pledged				65.00%
Fronting fee as a percentage of the face amount of each letter of credit	0.13%
6.00% Senior Notes [Member]
Line of Credit Facility [Line Items]
Previous term loan facility balance	$1,518,800,000	$1,518,800,000
Stated interest rate - percentage	6.00%
Maximum [Member] \| Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Maximum line of credit commitment fee percent	0.50%
Letter of credit fee as a percentage of the undrawn amount of each letter of credit, higher range	2.50%
Minimum [Member] \| Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Maximum line of credit commitment fee percent	0.38%
Letter of credit fee as a percentage of the undrawn amount of each letter of credit, higher range	1.75%
Base Rate [Member] \| Maximum [Member] \| 2013 Credit Facility [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	1.50%
Base Rate [Member] \| Minimum [Member] \| 2013 Credit Facility [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	0.75%
Eurocurrency Rate [Member] \| Maximum [Member] \| 2013 Credit Facility [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	2.50%
Eurocurrency Rate [Member] \| Minimum [Member] \| 2013 Credit Facility [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	1.75%
Eurocurrency Rate [Member] \| 2013 Term Loan Facility [Member]
Line of Credit Facility [Line Items]
Minimum interest rate	1.00%
Long-term debt, percentage bearing variable interest, percentage rate	3.25%
Base Rate [Member] \| 2013 Term Loan Facility [Member]
Line of Credit Facility [Line Items]
Minimum interest rate	2.00%
Long-term debt, percentage bearing variable interest, percentage rate	2.25%
Subsequent Event [Member] \| 2013 Credit Facility [Member]
Line of Credit Facility [Line Items]
Percentage of Equity Interests of Foreign Subsidiaries					65.00%

Debt_Debt_Maturities_Details

Debt Debt Maturities (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Line of Credit Facility [Line Items]
Long-term debt maturities, 2015	$21.20
Long-term debt maturities, 2016	669
Long-term debt maturities, 2017	12.9
Long-term debt maturities, 2018	1,530.90
Long-term debt maturities, 2019	12.1
Long-term debt maturities, 2020 and thereafter	3,740.70
Debt and capital lease obligations	5,986.80	6,002.40
Interest paid	404.4	388.2	396.1
Unamortized discount (premium), net	88.7
Unamortized debt issuance expense which will be amortized to interest expense over the next five years	$62.40

Debt_Senior_Notes_Details

Debt Senior Notes (Details) (USD $)	3 Months Ended			12 Months Ended		3 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Jun. 30, 2012	Dec. 31, 2012	Nov. 15, 2011
Debt Instrument [Line Items]
Redemption price of senior notes as percentage of principal amount plus a make whole premium and any accrued unpaid interest to the redemption date				100.00%
Redemption price of senior notes - percentage				101.00%
Gains (Losses) on extinguishment of debt	($11.50)	($4.50)	($0.90)		$0
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Other Borrowings				0
6.00% Senior Notes [Member]
Debt Instrument [Line Items]
Face amount of senior notes								1,600
Stated interest rate - percentage				6.00%
Repayments of long-term debt						81.2
6.25% Senior Notes [Member]
Debt Instrument [Line Items]
Face amount of senior notes								1,500
Stated interest rate - percentage				6.25%
Repayments of long-term debt						160.4
Senior Notes Six and Seven [Member]
Debt Instrument [Line Items]
Gains (Losses) on extinguishment of debt						0.6	2.8
Write-off of debt issuance costs						$3.40

Debt_Convertible_Debentures_De

Debt Convertible Debentures (Details) (USD $)	12 Months Ended			1 Months Ended	3 Months Ended
Debt Convertible Debentures (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jun. 30, 2014	Mar. 31, 2015	Jun. 30, 2014	Nov. 15, 2011
Debt Instrument [Line Items]
Aggregate principal amount of debentures outstanding	$732,500,000
Payments of Debt Issuance Costs	10,100,000	22,800,000	6,900,000
Convertible Junior Subordinated Debentures [Member]
Debt Instrument [Line Items]
Aggregate principal outstanding of convertible junior subordinated debentures	732,500,000
Debt instrument periodic payment interest rate	4.75%
Convertible debt condition one for debt conversion	140.00%
Conversion ratio					17.4967
Redemption price, percentage	100.00%
Debt conversion, original debt amount					1,000
Conversion price	$74.30
Stock price trigger	$80.02
Current conversion amount per principal amount of debentures	57.15
Period of redemption of debentures	at least 20 out of the 30 consecutive trading days immediately prior to the date on which notice of redemption is given
Convertible debt conversion period description	130.00%
Maximum percentage of the Company's net cash proceeds from the sale of its common stock and rights to acquire common stock which can be used for repayment of debt	400.00%
Carrying amount of equity component	215,400,000	215,400,000
Aggregate principal amount of debentures outstanding	732,500,000	732,500,000
Debt instrument, unamortized discount	-350,200,000	-352,800,000
Net carrying amount	382,300,000	379,700,000
Interest rate	4.90%	4.90%	4.90%
Interest expense - contractual interest coupon	34,800,000	34,800,000	34,800,000
Amortization of debt discount	2,600,000	2,300,000	2,100,000
Remaining discount amortization period	27 years
Payments of Debt Issuance Costs				10,100,000
Refinancing charges classified as interest expense	1,600,000					1,600,000
7.875% Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate - percentage	7.88%
Face amount of senior notes							250,000,000
Minimum [Member] \| Convertible Junior Subordinated Debentures [Member]
Debt Instrument [Line Items]
Number of days percentage closing common stock price exceeds conversion price condition to convert debentures	20
Maximum [Member] \| Convertible Junior Subordinated Debentures [Member]
Debt Instrument [Line Items]
Number of days percentage closing common stock price exceeds conversion price condition to convert debentures	30
Amount Per Principal Amount [Member] \| Convertible Junior Subordinated Debentures [Member]
Debt Instrument [Line Items]
Payments of Debt Issuance Costs				15
Principal Amount [Member] \| Convertible Junior Subordinated Debentures [Member]
Debt Instrument [Line Items]
Payments of Debt Issuance Costs				$1,000

Debt_Capital_Leases_Details

Debt Capital Leases (Details) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified	Dec. 31, 2014
Debt Disclosure [Abstract]
Equity affiliate receivable and payable right of offset	$38

Leases_Details

Leases (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Future minimum lease and royalty payments
Capital Leases, 2015	$9.50
Capital Leases, 2016	6.9
Capital Leases, 2017	1.4
Capital Leases, 2018	0.5
Capital Leases, 2019	0.5
Capital Leases, 2020 and Thereafter	10.6
Capital Leases, Total minimum lease payments	29.4
Capital Leases, Less interest	7.2
Capital Leases, Present value of minimum capital lease payments	22.2
Operating Leases, 2015	207.2
Operating Leases, 2016	196
Operating Leases, 2017	178.9
Operating Leases, 2018	104.3
Operating Leases, 2019	51.3
Operating Leases, 2020 and thereafter	64.3
Operating Leases, Total minimum lease payments	802
Coal Lease and Royalty Obligation, 2015	284.6
Coal Lease and Royalty Obligation, 2016	253.3
Coal Lease and Royalty Obligation, 2017	22.3
Coal Lease and Royalty Obligation, 2018	20.5
Coal Lease and Royalty Obligation, 2019	18.2
Coal Lease and Royalty Obligation, 2020 and Thereafter	29
Coal Lease and Royalty Obligation, Total minimum lease payments	627.9
Leases (Textuals)
Rental expense under operating leases	306	305.9	247.5
Contingent lease expense	0	0
Property, plant, equipment and mine development assets, gross value under capital leases	175.1	175.1
Accumulated depreciation of property, plant, equipment and mine development assets under capital leases	138.4	111.3
Total royalty expenses on coal reserve leases	507.8	546	637.5
Initial lease term for federal leases	ten years
Minimum annual production on federal leases	1.00%
Monthly royalty percentage on federal leases for coal sales using surface mining methods	12.50%
Monthly royalty percentage on federal leases for coal production using underground mining methods	8.00%
Period to redetermine royalty rates on leased coal reserves in Arizona	every ten years
Initial term of mining leases in Australia	up to 21 years
Company's lease obligations secured by outstanding surety bonds	$103.80

Asset_Retirement_Obligations_D

Asset Retirement Obligations (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation	$752.50	$712.80	$687.50
Asset Retirement Obligation, Current	30.2	21
Asset Retirement Obligation, Liabilities Incurred	22.7	0
Liabilities settled or disposed	-19.7	-15.4
Accretion expense	39.3	39.3
Revision to estimates	-2.6	1.4
Asset retirement obligations	722.3	691.8
Balance at end of year b active locations	676.2	660.8
Balance at end of year b closed or inactive locations	76.3	52
Credit adjusted, risk-free interest rates	6.82%	6.44%	6.28%
Surety bonds and bank guarantees outstanding to secure reclamation obligations or activities	645	568.4
Amount of reclamation self-bonding in certain states in which the company qualifies	1,361.40	1,365.10
Letters of credit in support of reclamation obligations or activities	17.6	17.6
Eastern US Coal Reserves [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Liabilities Incurred	$22.20

Postretirement_Health_Care_and2

Postretirement Health Care and Life Insurance Benefits (Details) (USD $)	3 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Components of net periodic postretirement benefit cost
Settlement related to the Patriot bankruptcy reorganization	$30.60	$0		$30.60		$0
Postretirement Health Care and Life Insurance Benefits [Member]
Components of net periodic postretirement benefit cost
Service cost for benefits earned		12.2		15.8		14.9
Interest cost on accumulated postretirement benefit obligation		36.4		41.8		54.9
Amortization of prior service cost (credit)		1.3		-1.7		2.5
Amortization of actuarial loss		14.5		24.1		32.8
Settlement related to the Patriot bankruptcy reorganization		0	[1]	63.2	[1]	0	[1]
Special termination benefits		1.6	[2]	0.9	[2]	0	[2]
Total net periodic postretirement or pension cost		$66		$144.10		$105.10

[1]	Refer to Note 25. "Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation" herein for additional details related to this transaction
[2]	Reflected in "Restructuring and pension settlement charges" in the consolidated statement of operations for the year ended December 31, 2014.

Postretirement_Health_Care_and3

Postretirement Health Care and Life Insurance Benefits (Details 1) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Estimated prior service cost that will be amortized from accumulated other comprehensive (income) loss	($11.40)		$1.40		($20.10)
Postretirement Health Care and Life Insurance Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of actuarial gains and losses amortized	0.00%
Amortization period - future working lifetime of active employees	11.7		11.96
Amounts recognized in accumulated other comprehensive loss
Net actuarial loss (gain) arising during year	115.8		-24.3		-68.3
Prior service credit arising during year	-18		0		-31.9
Amortization:
Actuarial loss	-14.5		-24.1		-32.8
Prior service (cost) credit	-1.3		1.7		-2.5
Settlement related to the Patriot bankruptcy reorganization
Actuarial loss	0	[1]	-61.3	[1]	0	[1]
Prior service cost	0	[1]	-1.9	[1]	0	[1]
Total recorded in other comprehensive loss (income)	82		-109.9		-135.5
Scenario, Forecast [Member] \| Postretirement Health Care and Life Insurance Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated net actuarial loss that will be amortized from accumulated other comprehensive (income) loss							24.9
Estimated prior service cost that will be amortized from accumulated other comprehensive (income) loss							$6.80

[1]	Refer to Note 25. "Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation" herein for additional details related to this transaction.

Postretirement_Health_Care_and4

Postretirement Health Care and Life Insurance Benefits (Details 2) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Increase (Decrease) in Postretirement Obligations	$9.60		$17		$38.90
Postretirement Health Care and Life Insurance Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Increase (Decrease) in Postretirement Obligations	27.6
Reconciled amount of plans funded status
Projected benefit obligation at beginning of period	735.4		1,026.10
Service cost	12.2		15.8		14.9
Interest cost	36.4		41.8		54.9
Participant contributions	2.2		2.3
Plan changes	-18	[1]	0	[1]
Benefits paid	-46.5		-66.5
Actuarial loss (gain)	115.8	[2]	-24.3	[2]
Settlement charges related to the Patriot bankruptcy reorganization	0	[3]	-260.7	[3]
Special termination benefits	1.6	[4]	0.9	[4]	0	[4]
Projected benefit obligation at end of period	839.1		735.4		1,026.10
Fair value of plan assets at beginning of period	0		0
Employer contributions	44.3		64.2
Participant contributions	2.2		2.3
Benefits paid and administrative fees (net of Medicare Part D reimbursements)	-46.5		-66.5
Fair value of plan assets at end of period	0		0		0
Funded status at end of year	-839.1		-735.4
Less current portion (included in Accounts payable and accrued expenses)	57.2		51.4
Noncurrent obligation (included in Accrued postretirement benefit costs)	-781.9		-684
Demographic Assumptions Change [Member]
Defined Benefit Plan Disclosure [Line Items]
Increase (Decrease) in Postretirement Obligations	63
Postretirement plan change [Member]
Defined Benefit Plan Disclosure [Line Items]
Increase (Decrease) in Postretirement Obligations	($45.40)

[1]	Includes the net impact of the following plan changes: a $45.4 million reduction to the benefit obligation related to various plan changes effective January 1, 2015 for certain plan participants that are designed to bring consistency amongst the various retiree medical programs; and a $27.6 million increase to the benefit obligation resulting from a plan change effective April 1, 2014 for certain plan participants' benefits no longer funded through a Medicare Advantage Program. The plan changes will not affect participant benefits.
[2]	During 2014, the Company reviewed its demographic assumptions (including mortality, retirements and terminations) in conjunction with the recently-issued mortality tables published by the Society of Actuaries, to select assumptions that are aligned with the Companybs experience. The updated demographic assumptions increased the December 31, 2014 benefit obligation by approximately $63 million
[3]	Refer to Note 25. "Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation" herein for additional details related to this transaction.
[4]	Reflected in "Restructuring and pension settlement charges" in the consolidated statement of operations for the year ended December 31, 2014.

Postretirement_Health_Care_and5

Postretirement Health Care and Life Insurance Benefits (Details 3) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Postretirement Health Care and Life Insurance Benefits [Member]
Weighted-average assumptions used to determine benefit obligations
Discount rate	4.10%		4.90%
Measurement date	31-Dec-14		31-Dec-13
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate	4.90%		4.21%	5.05%
Measurement date	31-Dec-13		31-Dec-12	31-Dec-11
Assumed health care cost trend rates, One percentage point increase
One Percentage-Point Increase Effect on total service and interest cost components	$4.10	[1]
One Percentage-Point Decrease Effect on total service and interest cost component	-3.8	[1]
One Percentage-Point Increase Effect on total postretirement benefit obligation	80.6	[1]
One Percentage-Point Decrease Effect on total postretirement benefit obligation	($70.30)	[1]
Pre-Medicare [Member]
Assumed health care cost trend rate
Health care cost trend rate assumed for next year	7.00%		6.26%
Rate to which the cost trend is assumed to decline (the ultimate trend rate)	4.75%		4.67%
Year that the rate reaches the ultimate trend rate	2021		2023
Post-Medicare [Member]
Assumed health care cost trend rate
Health care cost trend rate assumed for next year	6.00%		6.26%
Rate to which the cost trend is assumed to decline (the ultimate trend rate)	4.75%		4.67%
Year that the rate reaches the ultimate trend rate	2021		2023

[1]	In addition to the effect on total service and interest cost components of expense, changes in trend rates would also increase or decrease the actuarial gain or loss amortization expense component. The impact on actuarial gain or loss amortization would approximate the increase or decrease in the obligation divided by 11.70B years at January 1, 2015.

Postretirement_Health_Care_and6

Postretirement Health Care and Life Insurance Benefits (Details 4) (Postretirement Health Care and Life Insurance Benefits [Member], USD $)	Dec. 31, 2014
In Millions, unless otherwise specified	Dec. 31, 2014
Postretirement Health Care and Life Insurance Benefits [Member]
Estimated Future Benefit Payments
Postretirement Benefits, 2015	$57.20
Postretirement Benefits, 2016	59
Postretirement Benefits, 2017	59.9
Postretirement Benefits, 2018	60.4
Postretirement Benefits, 2019	60.7
Postretirement Benefits, Years 2020-2024	$297.60

Pension_and_Savings_Plans_Deta

Pension and Savings Plans (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Components of net periodic pension costs
Settlement Charge	$28.30	$51.80	$32.40
Pension Plans, Defined Benefit [Member]
Components of net periodic pension costs
Service cost for benefits earned	2.1	2.2	2
Interest cost on projected benefit obligation	45.4	42.2	46.7
Expected return on plan assets	-54.3	-59.5	-63.7
Amortization of prior service cost	1.3	1	1
Amortization of actuarial losses	30.2	65.7	48.6
Settlement Charge	8.7	0	0
Total net periodic postretirement or pension cost	$33.40	$51.60	$34.60

Pension_and_Savings_Plans_Deta1

Pension and Savings Plans (Details 1) (Pension Plan, Defined Benefit [Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Plan, Defined Benefit [Member]
Amounts recognized in accumulated other comprehensive loss
Net actuarial loss (gain) arising during year	$79.20	($133.80)	$67.60
Prior service cost arising during year	0	2.2	0
Amortization:
Net actuarial loss	-30.2	-65.7	-48.6
Prior service cost	-1.3	-1	-1
Settlement Charge	8.7	0	0
Total recorded in other comprehensive loss (income)	$39	($198.30)	$18

Pension_and_Savings_Plans_Deta2

Pension and Savings Plans (Details 2) (Pension Plan, Defined Benefit [Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Increase (Decrease) in Pension Plan Obligations	$36
Change in benefit obligation:
Projected benefit obligation at beginning of period	947.3		1,058.60
Service cost	2.1		2.2		2
Interest cost	45.4		42.2		46.7
Benefits paid	-57.2		-59.1
Actuarial loss (gain)	106.6	[1]	-98.8	[1]
Plan amendments	0		2.2
Settlement	-41.7		0
Projected benefit obligation at end of period	1,002.50		947.3		1,058.60
Fair value of plan assets at beginning of period	851.4		813.7
Actual return on plan assets	81.7		94.5
Employer contributions	5.6		2.3
Fair value of plan assets at end of period	839.8		851.4		813.7
Funded status at end of year	-162.7		-95.9
Amounts recognized in the consolidated balance sheets:
Current obligation (included in Accounts payable and accrued expenses)	-1.7		-1.7
Noncurrent obligation (included in Other noncurrent liabilities)	-161		-94.2
Net amount recognized	($162.70)		($95.90)

[1]	During 2014, the Company reviewed its demographic assumptions (such as mortality, retirements and terminations) in conjunction with the recently-issued mortality tables published by the Society of Actuaries, to select assumptions that are aligned with the Companybs experience. The updated demographic assumptions increased the December 31, 2014 benefit obligation by approximately $36 million.

Pension_and_Savings_Plans_Deta3

Pension and Savings Plans (Details 3) (Pension Plan, Defined Benefit [Member])	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Plan, Defined Benefit [Member]
Weighted-average assumptions used to determine benefit obligations
Discount rate		4.15%	4.95%
Measurement date		31-Dec-14	31-Dec-13
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate		4.95%	4.10%	5.00%
Expected long-term return on plan assets	6.25%	6.85%	7.75%	8.00%
Measurement date		31-Dec-13	31-Dec-12	31-Dec-11

Pension_and_Savings_Plans_Deta4

Pension and Savings Plans (Details 4) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Level 1 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	$184.50	$196.30
Level 2 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	625.1	625.2
Level 3 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	30.2	29.9
U.S. equity securities
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	190.3	196
U.S. equity securities \| Level 1 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	141.7	141.8
U.S. equity securities \| Level 2 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	48.6	54.2
U.S. equity securities \| Level 3 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
International equity securities
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	69.8	80.6
International equity securities \| Level 1 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
International equity securities \| Level 2 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	69.8	80.6
International equity securities \| Level 3 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
U.S. debt securities
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	54.4	61.3
U.S. debt securities \| Level 1 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	25.3	30.6
U.S. debt securities \| Level 2 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	29.1	30.7
U.S. debt securities \| Level 3 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
International debt securities
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	23.5	21.9
International debt securities \| Level 1 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
International debt securities \| Level 2 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	23.5	21.9
International debt securities \| Level 3 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
Corporate debt securities
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	447.8	424.3
Corporate debt securities \| Level 1 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
Corporate debt securities \| Level 2 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	447.8	424.3
Corporate debt securities \| Level 3 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
Short-term investments
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	23.8	37.4
Short-term investments \| Level 1 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	17.5	23.9
Short-term investments \| Level 2 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	6.3	13.5
Short-term investments \| Level 3 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
Interests in real estate
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	30.2	29.9
Interests in real estate \| Level 1 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
Interests in real estate \| Level 2 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
Interests in real estate \| Level 3 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	30.2	29.9	27.8
Pension Plans, Defined Benefit [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	$839.80	$851.40	$813.70

Pension_and_Savings_Plans_Deta5

Pension and Savings Plans (Details 5) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Real Estate Investment [Member]
Assets Held At Reporting Date:
Fair value of plan assets at end of period	$30.20	$29.90
Level 3 [Member]
Assets Held At Reporting Date:
Fair value of plan assets at end of period	30.2	29.9
Level 3 [Member] \| Real Estate Investment [Member]
Summary of changes in the fair value of the Master Trust's investments
Fair value of plan assets at beginning of period	29.9	27.8
Assets Held At Reporting Date:
Realized gains	0.2	0.7
Unrealized gains relatng to investments still held at the reporting date	4.9	2.6
Purchases, sales and settlements, net	-4.8	-1.2
Fair value of plan assets at end of period	$30.20	$29.90

Pension_and_Savings_Plans_Deta6

Pension and Savings Plans (Details 6) (Pension Plan, Defined Benefit [Member], USD $)	Dec. 31, 2014
In Millions, unless otherwise specified	Dec. 31, 2014
Pension Plan, Defined Benefit [Member]
Estimated Future Benefit Payments
2015	$62.20
2016	63
2017	63.6
2018	64.2
2019	64.1
Years 2020-2024	$327.70

Pension_and_Savings_Plans_Deta7

Pension and Savings Plans (Details Textuals) (USD $)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	Dec. 31, 2015	years	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Estimated prior service cost that will be amortized from accumulated other comprehensive loss		($11,400,000)	$1,400,000	($20,100,000)
Settlement Charge		28,300,000	51,800,000	32,400,000
Defined Contribution Plans [Abstract]
Number of 401(k) plans		3
Paid discretionary contributions to defined contribution pension plans, company match		44,700,000	46,400,000	51,100,000
Additional discretionary contributions to defined contribution pension plans, performance feature		18,300,000	16,500,000	22,500,000
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Settlements, Benefit Obligation		41,700,000
Actuarial gains and losses amortization corridor, percentage		5.00%
Period of amortization (in years)		5
Estimated net actuarial loss that will be amortized from accumulated other comprehensive loss	39,600,000
Estimated prior service cost that will be amortized from accumulated other comprehensive loss	1,000,000
Expected rate of return on plan assets	6.25%	6.85%	7.75%	8.00%
Accumulated benefit obligation for pension plans		1,002,500,000	947,300,000
Minimum funded percentage defined by the Pension Protection Act of 2006		80.00%
Pension and Other Postretirement Benefit Contributions		3,900,000
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	4,800,000
Settlement Charge		8,700,000	0	0
Other Pension Plan, Postretirement or Supplemental Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefit Contributions		$1,700,000
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocations for assets of Master Trust		35.00%	35.00%
Fixed Income Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocations for assets of Master Trust		65.00%	65.00%
Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocations for assets of Master Trust		4.00%	4.00%

Stockholders_Equity_Details

Stockholders' Equity (Details)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary of common stock activity
Shares outstanding at the beginning of the year	270.1	268.6	271.1
Stock options exercised	0	0.1	0.2
Stock grants to employees	1.3	1	1.5
Employee stock purchases	0.5	0.5	0.3
Shares relinquished	-0.2	-0.1	-0.3
Shares repurchased	0	0	-4.2
Shares outstanding at the end of the year	271.7	270.1	268.6

Stockholders_Equity_Details_Te

Stockholders' Equity (Details Textuals) (USD $)	3 Months Ended	12 Months Ended					60 Months Ended
In Millions, except Per Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2008	Dec. 31, 2006	Dec. 31, 2017	Dec. 31, 2011
Schedule Of Stock By Class (Textuals) [Abstract]
Common Stock, shares authorized		800
Preferred Stock, par value		$0.01
Common Stock, par value		$0.01
Number of votes entitled for common stock holders		one vote per share
Aggregate principal amount of debentures outstanding		$732.50
Liquidation preference of perpetual preferred stock, per share		$1,000
Perpetual Preferred Stock annual cumulative dividend rate		3.09%
DefinedIntervalInYearstoPayDividendsonPerpetualPreferredStock							five
ElectedMembersToServeOnCompanysBoardOfDirectors		two
Period for payment of dividend on perpetual preferred stock		10
NumberOfFailedAmountOfDividendsOnPreferredStock		six
Authorized amount for common stock repurchase		1,000
Treasury Stock, shares		14	13.8
Cost of shares repurchased		299.6			199.8	99.8
Amount available for repurchase of shares under share repurchase program		700.4
Maximum amount that can be authorized for repurchase of common stock outside the share repurchase program		100
Stock Repurchased During Period, Shares		0	0	4.2
Common stock repurchase	$99.90	$0	$0	$99.90
Shares relinquished		0.2	0.1	0.3
Common Stock, shares outstanding		271.7	270.1	268.6				271.1
Common Stock [Member]
Schedule Of Stock By Class (Textuals) [Abstract]
Common Stock, shares authorized		800	800
Common Stock, par value		$0.01	$0.01
Common Stock, shares outstanding		271.7	270.1
Preferred Stock [Member]
Schedule Of Stock By Class (Textuals) [Abstract]
Preferred Stock, par value		$0.01	$0.01
Preferred Stock, shares outstanding		0	0
Preferred Stock, shares authorized		10	10
Series Common Stock [Member]
Schedule Of Stock By Class (Textuals) [Abstract]
Common Stock, shares authorized		40	40
Common Stock, par value		$0.01	$0.01
Common Stock, shares outstanding		0	0
Perpetual Preferred Stock Member
Schedule Of Stock By Class (Textuals) [Abstract]
Preferred Stock, shares outstanding		0	0
Preferred Stock, shares authorized		0.8	0.8
Treasury Stock [Member]
Schedule Of Stock By Class (Textuals) [Abstract]
Treasury Stock, shares		7.7

ShareBased_Compensation_Detail

Share-Based Compensation (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$46.80	$50.90	$45.40
Tax benefit	17.3	18.8	16.7
Share-based compensation expense, net of tax benefit	29.5	32.1	28.7
Cash received upon the exercise of stock options and from employee stock purchases	5.5	7.3	9.4
(Write-off) excess tax benefits related to share-based compensation	-8.3	-4.5	8.3
Equity Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	46.1	50.9	45.4
Other Liabilities [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$0.70	$0	$0

ShareBased_Compensation_Detail1

Share-Based Compensation (Details 1) (USD $)	12 Months Ended
Share-Based Compensation (Details 1) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Restricted Stock Units (RSUs) [Member]
Summary of restricted stock award activity
Nonvested, Beginning of Period	287,375
Granted	218,017
Vested	-3,261
Forfeited	-5,025
Nonvested, End of Period	497,106
Weighted Average Grant-Date Fair Value, Beginning of Period	19.5
Weighted Average Grant-Date Fair Value, Granted	19.48
Weighted Average Grant Date Fair Value, Vested	23.56
Weighted Average Grant Date Fair Value, Forfeited	21.4
Weighted Average Grant-Date Fair Value, End of Period	19.44
Restricted Stock [Member]
Summary of restricted stock award activity
Nonvested, Beginning of Period	2,493,046
Granted	1,331,077
Vested	-425,116
Forfeited	-211,416
Nonvested, End of Period	3,187,591
Weighted Average Grant-Date Fair Value, Beginning of Period	34.6
Weighted Average Grant-Date Fair Value, Granted	19.19
Weighted Average Grant Date Fair Value, Vested	57.59
Weighted Average Grant Date Fair Value, Forfeited	25.13
Weighted Average Grant-Date Fair Value, End of Period	25.63
Performance unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	1 year 6 months	1 year 7 months 6 days
Summary of restricted stock award activity
Nonvested, Beginning of Period	463,317
Granted	644,412
Vested	-150,769
Forfeited	-206,808
Nonvested, End of Period	750,152	463,317

ShareBased_Compensation_Detail2

Share-Based Compensation (Details 2) (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Share-based Compensation, Stock Options, Activity
Granted	1,300,000	1,000,000	1,500,000
Exercised	0	-100,000	-200,000
Stock Options [Member]
Schedule of Share-based Compensation, Stock Options, Activity
Options outstanding, Beginning Balance	2,295,076
Granted	1,044,426
Exercised	-44,933
Forfeited	-278,556
Options outstanding, Ending Balance	3,016,013	2,295,076
Options Vested and Exercisable	1,594,695
Weighted Average Exercise Price, Beginning of Period	37.32
Weighted Average Exercise Price, Granted	19.44
Weighted Average Exercise Price, Exercised	10.22
Weighted Average Exercise Price, Forfeited	36.9
Weighted Average Exercise Price, End of Period	31.57	37.32
Options Vested and Exercisable, Weighted Average Exercise Price	40.2
Weighted Average Remaining Contractual Life, Beginning of Period	6 years 4 months 21 days	6 years 0 months 0 days
Options Vested and Exercisable, Weighted Average Remaining Contractual Life	4 years 4 months 13 days
Aggregate Intrinsic Value, End of Period	0	0.5
Options Vested and Exercisable, Aggregate Intrinsic Value	0

ShareBased_Compensation_Detail3

Share-Based Compensation (Details 3) (USD $)	12 Months Ended
Share-Based Compensation (Details 3) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average fair value	$7.38	$12.13	$18.59
Expected option life	5 years	5 years	5 years
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.70%	0.70%	0.90%
Expected volatility	48.40%	64.10%	64.00%
Dividend yield	1.70%	1.20%	0.60%

ShareBased_Compensation_Detail4

Share-Based Compensation (Details 5) (Performance unit [Member])	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Performance unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Risk-free interest rate	0.80%	0.40%	0.40%
Expected volatility	45.30%	47.30%	52.80%
Dividend yield	1.70%	1.40%	0.60%

ShareBased_Compensation_Detail5

Share-Based Compensation (Details Textuals) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	years	Dec. 31, 2013	Dec. 31, 2012
Share-Based Compensation Textuals [Abstract]
Common stock available for grant	6,800,000
Share-based Compensation Arrangement by Share-based Payment Award, Description	2
Number of Shares Authorized	14,000,000
Unrecognized compensation cost related to nonvested awards net of tax Total	$25,400,000
Unrecognized compensation cost period for recognition, years	3 years
Unrecognized compensation cost period for recognition, weighted-average, years	0.7
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	10 years
Total intrinsic value of options exercised	400,000	900,000	4,200,000
Maximum employee Contribution to employee stock purchase plans based on compensation, percentage	15.00%
Maximum employee Contribution to employee stock purchase plans based on compensation, amount	25,000
Common stock discount under employee stock purchase plans	15.00%
Employee Stock Purchase Plans,Fair value estimation	estimated by adding the fair value of 0.15 of one share of stock to the fair value of 0.85 of an option on one share of stock
Shares purchased under the ESPP plans	500,000	500,000	300,000
U.S Employees [Member]
Share-Based Compensation Textuals [Abstract]
Number of Shares Authorized	5,000,000
Australian Employees [Member]
Share-Based Compensation Textuals [Abstract]
Number of Shares Authorized	1,000,000
Employee Stock [Member]
Share-Based Compensation Textuals [Abstract]
Number of Shares Authorized	6,000,000
Deferred Stock Units [Member]
Share-Based Compensation Textuals [Abstract]
Vesting period of performance units	1 year
Restricted Stock Awards [Member]
Share-Based Compensation Textuals [Abstract]
Vesting period of performance units	3 years
Restricted Stock [Member]
Share-Based Compensation Textuals [Abstract]
Total fair value of restricted stock awards granted	25,500,000	29,200,000	44,400,000
Total fair value of restricted stock awards vested	24,500,000	13,200,000	19,900,000
Restricted Stock Units (RSUs) [Member]
Share-Based Compensation Textuals [Abstract]
Vesting period of performance units	5 years
Total fair value of restricted stock awards granted	4,200,000	7,600,000
Total fair value of restricted stock awards vested	100,000	100,000
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate	1.70%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate	48.10%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate	1.60%
Vesting Period [Domain]
Share-Based Compensation Textuals [Abstract]
Vesting period of performance units	3 years
Cliff Vest [Domain]
Share-Based Compensation Textuals [Abstract]
Vesting period of performance units	3 years
Performance unit [Member]
Share-Based Compensation Textuals [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Description	three
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate	0.80%	0.40%	0.40%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate	45.30%	47.30%	52.80%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate	1.70%	1.40%	0.60%
Number of outstanding units vested	150,769
Aggregate intrinsic value	$200,000
Conversion price per share	$7.98

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Income (Loss) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Other Comprehensive Income, Available-For-Sale Securities, Net Unamortized (Gain) Loss Arising During Period, Net of Tax	$0		$0	$0
After-tax components of comprehensive income (loss)
Foreign Currency Translation Adjustment, Beginning Balance	-70.5		22.2	3.1
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	0		0	0
Reclassification from other comprehensive income to earnings	0		0	0
Foreign currency translation adjustment	-41		-92.7	19.1
Foreign Currency Translation Adjustment, Ending Balance	-111.5		-70.5	22.2
Accumulated Other Comprehensive Income Loss Acturial Loss Associated With Postretirement Plans And Workers Compensation Obligation Net Of Tax	-317.5		-205.8	-411.7	-464.9
Other Comprehensive Income (Loss), Postretirement Plans and Workers' Compensation Obligations, Period Increase Decrease, Net of Tax	0		0	0
Reclassification from other comprehensive income to earnings	31		95	53.2
Current period change	-142.7		110.9	0
Prior Service Cost Associated with Postretirement Plans, Beginning Balance	12		12.7	-9.6
Other Comprehensive Income (Loss), Prior Service Cost Associated with Postretirement Plans, Period Increase Decrease, Net of Tax	0		0	0
Reclassification from other comprehensive income to earnings	1.7		0.7	2.2
Current period change	11.4		-1.4	20.1
Prior Service Cost Associated with Postretirement Plans, Ending Balance	25.1		12	12.7
Cash Flow Hedges, Beginning Balance	-155.7		387.5	335.7
Increase in fair value of cash flow hedges, net of tax	-195		-333.6	350.4
Reclassification from other comprehensive income to earnings	-10.2		-209.6	-298.6
Current Period Change	0		0	0
Cash Flow Hedges, Ending Balance	-360.9		-155.7	387.5
Available-For-Sale Securities Adjustment, Beginning Balance	0.8		0.3	-6.7
Unrealized holding losses on available-for-sale securities	-3.7		-12.3	-15.5
Reclassification from other comprehensive income to earnings	2.9		12.8	22.5
Available-For-Sale Securities Adjustment, Ending Balance	0		0.8	0.3
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance	-764.8		-419.2	11	-142.4
Accumulated Other Comprehensive Loss Net Change in Fair Value of Cash Flow Hedges and Available for Sale Securities	-198.7		-345.9	334.9
Total Accumulated Other Comprehensive Income (Loss), Reclassification	25.4		-101.1	-220.7
Total Accumulated Other Comprehensive Income (Loss), Current period change net of tax	-172.3		16.8	39.2
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	-764.8		-419.2	11	-142.4
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax [Abstract]
Cash flow hedges	-47.9	[1]	174.3	400
Available-for-sale securities before income taxes	-4.7		-21.3
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax	1.8		8.5
Net actuarial loss associated with postretirement health care and life insurance benefits operating costs and expenses [Member]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax [Abstract]
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	14.5		24.1
Settlement charges related to the Patriot bankruptcy reorganization [Member]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax [Abstract]
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	0		61.3
Net actuarial loss defined benefit pension plans operating costs and expenses [Member]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax [Abstract]
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	24.8		54.4
Net actuarial loss defined benefit pension plans restructuring and pension settlement charges [Member]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax [Abstract]
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	8.7		0
Net actuarial loss defined benefit pension plans selling and administrative expenses [Member]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax [Abstract]
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	5.4		11.3
Net actuarial loss insignificant items [Member]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax [Abstract]
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	-4.1		1.1
Net actuarial loss associated with postretirement plans and workers compensation obligations total before income taxes [Member]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax [Abstract]
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	49.3		152.2
Net income tax benefit actuarial loss [Member]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax [Abstract]
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	-18.3		-57.2
Prior service cost associated with postretirement health care and life insurance benefits operating costs and expenses [Member]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax [Abstract]
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	1.3		-1.7
Settlement charges related to the Patriot bankruptcy reorganization prior service cost [Member]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax [Abstract]
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	0		1.9
Prior service cost defined benefit pension plans operating costs and expenses [Member]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax [Abstract]
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	1.3		1
Prior service cost associated with postretirement plans before income taxes (provision) [Member]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax [Abstract]
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	2.6		1.2
Prior service costs associated with postretirement plans income tax benefit [Member]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax [Abstract]
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	0.9		0.5
Cash flow hedges foreign currency cash flow hedge contracts operating costs and expenses [Member]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax [Abstract]
Cash flow hedges	27.3		-162.4
Cash flow hedges fuel and explosives commodity swaps operating costs and expenses [Member]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax [Abstract]
Cash flow hedges	22.3		-11.4
Cash flow hedges coal trading and commodity futures, swaps and options other revenues [Member]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax [Abstract]
Cash flow hedges	-63.9		-130.6
Cash flow hedges insignificant items [Member]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax [Abstract]
Cash flow hedges	0.4		0.5
Cash flow hedges total before income taxes [Member]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax [Abstract]
Cash flow hedges	-13.9		-303.9
Cash flows hedges income tax provision [Member]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax [Abstract]
Cash flow hedges	-3.7		-94.3
Available-for-sale securities debt securities interest income [Member]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax [Abstract]
Available-for-sale securities before income taxes	0		0.2
Available-for-sale securities equity securities asset impairment and mine closure costs [Member]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax [Abstract]
Available-for-sale securities before income taxes	($4.70)		($21.50)

[1]	Includes the reclassification from "Accumulated other comprehensive loss" into earnings of $136.9 million of previously unrecognized gains on foreign currency cash flow hedge contracts monetized in the fourth quarter of 2012.

Resource_Management_Acquisitio1

Resource Management, Acquisitions and Other Commercial Events (Details) (USD $)	12 Months Ended			1 Months Ended	3 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2014	Jun. 30, 2014	Feb. 03, 2012
OtherCommercialEvents [Line Items]
Proceeds from sale of nonstrategic assets	$203.70	$178.30	$147.90
Interest in unincorporated joint venture project	50.00%
Noncontrolling interest, decrease from purchase of interests			-49.8
MCGH [Member]
OtherCommercialEvents [Line Items]
Equity interest, converted from receivable, per court ruling						90.00%
Business combinations, recognized identifiable assets acquired and liabilities assumed, noncontrolling interest						39
Noncontrolling interest, decrease from purchase of interests			49.8
Decrease in APIC due to MCGH NCI purchases			10.8
Nonstrategic Australian mining tenement [Member]
OtherCommercialEvents [Line Items]
Proceeds from sale of nonstrategic assets				62.6
Gain (loss) on sale of nonstrategic asset	0
Nonstrategic Kentucky Coal Reserves And Surface Lands [Member]
OtherCommercialEvents [Line Items]
Proceeds from sale of nonstrategic assets	29.6	70
Gain (loss) on sale of nonstrategic asset	13.6	40.3
Western U.S. Mining Segment Customer [Member]
OtherCommercialEvents [Line Items]
Sales-related expenses	6.4
Positive Outcome of Litigation [Member] \| Western U.S. Mining Segment Customer [Member]
OtherCommercialEvents [Line Items]
Contract revenue	$33.50				$43.20

Earnings_per_Share_Details

Earnings per Share (Details) (USD $)	3 Months Ended																12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings per Share (EPS) (Textuals) [Abstract]
Antidilutive shares excluded from EPS calculation																	3.2	2.3	1.2
EPS numerator:
Loss from continuing operations, net of income taxes	($478.80)		($154)		($72)		($44.30)		($401.10)		$24		$101.40		($10.30)		($749.10)	($286)	($470.90)
Less: Net income attributable to noncontrolling interests																	9.7	12.3	10.6
Loss from continuing operations attributable to common stockholders, before allocation of earnings to participating securities																	-758.8	-298.3	-481.5
Less: Earnings allocated to participating securities																	1	0.8	0.7
Loss from continuing operations attributable to common stockholders, after allocation of earnings to participating securities																	-759.8	-299.1	-482.2
Loss from discontinued operations, net of income taxes																	-28.2	-226.6	-104.2
Loss from discontinued operations attributable to common stockholders, after allocation of earnings to participating securities																	-28.2	-226.6	-104.2
Net loss attributable to common stockholders, after earnings allocated to participating securities																	($788)	($525.70)	($586.40)
EPS denominator:
Weighted average shares outstanding - basic	268.2		268.2		268		267.9		267.3		267.2		266.9		266.9		268.1	267.1	268
Weighted average shares outstanding - diluted									267.3		267.7		267.5		266.9		268.1	267.1	268
Basic EPS attributable to common stockholders:
Loss from continuing operations	($1.79)	[1]	($0.58)	[1]	($0.28)	[1]	($0.18)	[1]	($1.52)	[2]	$0.06	[2]	$0.39	[2]	($0.05)	[2]	($2.83)	($1.12)	($1.80)
Loss from discontinued operations																	($0.11)	($0.85)	($0.39)
Net loss attributable to common stockholders																	($2.94)	($1.97)	($2.19)
Diluted EPS attributable to common stockholders:
Loss from continuing operations									($1.52)	[2]	$0.06	[2]	$0.39	[2]	($0.05)	[2]	($2.83)	($1.12)	($1.80)
Loss from discontinued operations																	($0.11)	($0.85)	($0.39)
Net loss attributable to common stockholders																	($2.94)	($1.97)	($2.19)

[1]	EPS for the quarters may not sum to the amounts for the year as each period is computed on a discrete basis.
[2]	EPS for the quarters may not sum to the amounts for the year as each period is computed on a discrete basis

Management_Labor_Relations_Lab

Management - Labor Relations Labor Relations (Details)	12 Months Ended
Management - Labor Relations Labor Relations (Details)	Dec. 31, 2014
Concentration Risk [Line Items]
Entity Number of Employees	8,300
Entity Number Of Hourly Employees	6,000
Percentage of hourly employees represented by organized labor unions	39.00%
Percentage Of Coal Production Generated By Hourly Employees Represented By Organized Labor Unions	20.00%
Number of US Mines Represented by Unions	1
Percentage Of Australian Hourly Employees Under Contract Negotiations	56.00%
Percentage Of Coal Production Generated By Australian Hourly Employees Under Contract Negotiation	42.00%
United Mine Workers of America [Member]
Concentration Risk [Line Items]
Percentage of hourly employees represented by organized labor unions	9.00%
Percentage Of Coal Production Generated By Hourly Employees	4.00%

Financial_Instruments_Details

Financial Instruments (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012	Sep. 24, 2013
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	$2,483.90
Financial Instruments and Guarantees with Off-Balance-Sheet Risk (Textuals) [Abstract]
Letters of credit outstanding					94.7
Amount in bank guarantees, letters of credit and surety bonds related to road maintenance, performance guarantees and other operations	150
DTA Lease Term	30
Letter of credit arrangement for workers compensation	22.7
Collateral for letter of credit related to workers compensation	32.6
Credit support to Patriot	122.2		141.5
Maximum capacity of the securitization program	275
Amount available under the securitization program	204
Total consideration received by Company related to accounts receivable sold under securitization program	4,257.20
Cash up front from sale of receivables	2,775.50
Additional cash upon collection of underlying receivables	1,272.30
Non collected receivables	209.4
Reduction in accounts receivable as a result of securitization activity	30		100
Expense associated with securitization transactions	1.5		1.5	2
DTA and PBGC [Member]
Financial Instruments and Guarantees with Off-Balance-Sheet Risk (Textuals) [Abstract]
Letters of credit outstanding	79.7
Dominion Terminal Associates Partnership [Member]
Financial Instruments and Guarantees with Off-Balance-Sheet Risk (Textuals) [Abstract]
Ownership percentage of equity method investment	37.50%
Number of letters of credit supporting reimbursement obligation	4
Maximum reimbursement obligation to commercial bank	42.7
Pension Plans Agreement With PBG and TXU Europe [Member]
Financial Instruments and Guarantees with Off-Balance-Sheet Risk (Textuals) [Abstract]
Defined benefit pension plans requiring special contributions	2
Letter of credit maintained by the Company in favor of the PBGC	37
Guarantee in place from TXU Europe Limited	110
Reclamation Obligations [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	2,024
Coal Lease Obligations [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	103.8
Workers' Compensation Obligations [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	126.4
Other [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	229.7	[1]
Performance Guarantee [Member]
Financial Instruments and Guarantees with Off-Balance-Sheet Risk (Textuals) [Abstract]
Liability for reclamation and bonding guarantee	44.7		45.6
Self bonding [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	1,361.40
Self bonding [Member] \| Reclamation Obligations [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	1,361.40
Self bonding [Member] \| Coal Lease Obligations [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	0
Self bonding [Member] \| Workers' Compensation Obligations [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	0
Self bonding [Member] \| Other [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	0	[1]
Surety Bond [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	532.7
Financial Instruments and Guarantees with Off-Balance-Sheet Risk (Textuals) [Abstract]
Credit support to Patriot	81.4
Surety Bond [Member] \| Reclamation Obligations [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	325.2
Surety Bond [Member] \| Coal Lease Obligations [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	103.8
Surety Bond [Member] \| Workers' Compensation Obligations [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	92.3
Surety Bond [Member] \| Other [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	11.4	[1]
Bank Guarantees [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	437.2
Bank Guarantees [Member] \| Reclamation Obligations [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	319.8
Bank Guarantees [Member] \| Coal Lease Obligations [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	0
Bank Guarantees [Member] \| Workers' Compensation Obligations [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	0
Bank Guarantees [Member] \| Other [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	117.4	[1]
Letters of credit [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	152.6
Financial Instruments and Guarantees with Off-Balance-Sheet Risk (Textuals) [Abstract]
Credit support to Patriot	22.4
Letters of credit [Member] \| Reclamation Obligations [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	17.6
Letters of credit [Member] \| Coal Lease Obligations [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	0
Letters of credit [Member] \| Workers' Compensation Obligations [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	34.1
Letters of credit [Member] \| Other [Member]
Guarantee Obligations [Line Items]
Financial instruments with off balance sheet risk	100.9	[1]
Corporate Guarantees [Member]
Financial Instruments and Guarantees with Off-Balance-Sheet Risk (Textuals) [Abstract]
Credit support to Patriot	$18.40

[1]	Other includes the $79.7 million in letters of credit related to Dominion Terminal Associates and the PBGC, as described below, and an additional $150.0 million in bank guarantees, letters of credit and surety bonds related to road maintenance, performance guarantees and other operations.

Commitments_and_Contingencies_

Commitments and Contingencies (Details 1) (USD $)

3 Months Ended

10 Months Ended

12 Months Ended

264 Months Ended

312 Months Ended

12 Months Ended

Sep. 30, 2012

Jun. 30, 2012

Sep. 30, 2011

Nov. 01, 2015

Dec. 31, 2015

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2032

Dec. 31, 2040

Dec. 31, 2016

Jul. 31, 2011

Long-term Purchase Commitment [Line Items]

Take Or Pay Arrangement Terms Years (Maximum)

Take-or-pay obligations

$2,827,200,000

Take Or Pay Obligations Due In One Year

329,500,000

Leased coal reserves adjacent to NARM

1,100,000,000

Weighted average bid price per mineable ton

1.1

Annual payments on coal reserves 2012 to 2016

247,900,000

Number Of Tons Of Coal In Which Company Was Named Winning Bidder Adjacent to Caballo

220,000,000

Bid Price Per Mineable Ton

0.95

Annual Coal Reserve Payments Pursuant To Belle Ayr North Lease

42,100,000

Number Of Tons Of Coal In Which Company Was Named Winning Bidder In The Powder River Basin

130,000,000

Bid Price Per Mineable Ton In The Powder River Basin

1.1

Annual Coal Reserve Payments Pursuant To Caballo West Lease

28,600,000

Reimbursement for the difference in the federal coal lease payments made in 2011

13,500,000

number of annual true up payments

Annual true up payments for the excess of the $1.10 bid price versus $0.95 under the transferred lease

3,900,000

Aggregate received from Alpha for the reimbursement payment and first true up payment

21,300,000

Remaining annual true up payments due from Alpha on November 1 of each of the years from 2012 through 2015

Federal Coal Lease Term Years

Capital Additions [Member]

Long-term Purchase Commitment [Line Items]

Purchase commitments for capital expenditures

42,700,000

Scenario, Forecast [Member]

Long-term Purchase Commitment [Line Items]

Annual payments on coal reserves 2012 to 2016

247,900,000

Annual Coal Reserve Payments Pursuant To Belle Ayr North Lease

42,100,000

Annual Coal Reserve Payments Pursuant To Caballo West Lease

28,600,000

Annual true up payments for the excess of the $1.10 bid price versus $0.95 under the transferred lease

$3,900,000

Commitments_and_Contingencies_1

Commitments and Contingencies (Details 2)

3 Months Ended

12 Months Ended

In Millions, unless otherwise specified

Sep. 30, 2014

Mar. 31, 2014

Dec. 31, 2014

Mar. 18, 2014

Dec. 31, 2013

Jan. 19, 2012

Sep. 30, 2011

Dec. 31, 2007

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

USD ($)

Gulf Power Company Litigation [Member]

Oklahoma Lead Litigation [Member]

Monto Coal Pty Limited [Member]

Wilkie Creek [Member]

Prarie State Energy Campus [Member]

USD ($)

AUD

sites

Loss Contingency [Abstract]

Ownership Percentage In Subsidiaries

51.00%

Damages sought

1,193.20

113.1

Class B Shareholders Claim for Dividends Payable and Related Interest

50.1

Damages awarded by the arbitrator to Eagle on some of Eagles claims

23.4

Estimated loss associated with Eagle Mining arbitration

7.8

Additional charge recorded as a result of the damages awarded to Eagle in arbitration

-10.6

-15.6

15.6

Tons Shipped Subject To Contract Pricing Arbitration

4,800,000

Pricing rebate provided in settlement of contract pricing arbitration

68.7

Alleged shortage of past and future coal shipments under a coal supply agreement, tons

5,000,000

Litigation Settlement Damages Awarded to Plaintiff

20.6

Litigation Settlement, Prejudgement Interest

6.9

Charge recorded for settlement damages

20.6

Charge recorded for prejudgement interest

6.9

Number of national priority list sites based on the Superfund Amendments and Reauthorization Act of 1986 at which Gold Fields or the former affiliate, has been named a potentially responsible party (PRP)

Number of additional national priority list sites in which claims were asserted

Total number of national priority list sites

Reduced number of national priority list sites due to completion of work, transfer or regulatory inactivity

Undiscounted environmental clean-up liabilities, total

69.4

63.8

Undiscounted environmental clean-up liabilities, current

$19.40

$18.30

$19.40

$18.30

Capacity Of New Electricity Generation Project

1,600

Undivided Interest Percent Of New Electricity Generation Project

5.06%

Matters_Related_to_the_Bankrup1

Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation (Patriot) (Details) (USD $)

1 Months Ended

3 Months Ended

12 Months Ended

60 Months Ended

In Millions, unless otherwise specified

Jan. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Dec. 31, 2017

Dec. 18, 2013

Oct. 23, 2012

Oct. 31, 2007

plaintiffs

Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation (Patriot) [Line Items]

Number of company operated mines included in Patriot Spin-off

Number of majority owned JV mines included in the Patriot spin-off

Number of coal preparation facilities servicing contractor-operatedines included in the Patriot spin-off

Proven and probable coal reserves related to Patriot

1,200,000,000

Initial Payment based on the construct of the negotiated settlement

$90

Amount recorded in accumulated postretirement healthcare benefit obligations to Patriot

260.7

NBCWA obligations included in Accumulated other comprehensive loss

63.2

Credit support to Patriot

141.5

122.2

141.5

Fair value of credit support to Patriot

57.6

Credit support to Patriot ending after five years

Credit support in the form of surety bonds related to Patriots Coal Act obligations

50.7

Total settlement charges

128.6

Settlement charges related to accumulated postretirement healthcare benefit obligations of certain Patriot retirees under the NBCWA Agreement

30.6

Charge related to settlement of other claims involving the Patriot bankruptcy

Payment to Patriot based on the construct of the negotiated settlement

Payment to the VEBA based on the construct of the negotiated settlement

Payments to the VEBA to settle the accumulated postretirement healthcare benefit obligations

240

Total liabilities related to the Patriot settlement

326.1

271.8

326.1

Number of individual plaintiffs involved in class action lawsuit

Potential exposure from Patriot bankruptcy

150

Scenario, Forecast [Member]

Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation (Patriot) [Line Items]

Funding of the newly established VEBA

310

Payment to the VEBA based on the construct of the negotiated settlement

Surety Bond [Member]

Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation (Patriot) [Line Items]

Credit support to Patriot

81.4

Standby Letters of Credit [Member]

Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation (Patriot) [Line Items]

Credit support to Patriot

22.4

Corporate Guarantees [Member]

Matters Related to the Bankruptcy Reorganization of Patriot Coal Corporation (Patriot) [Line Items]

Credit support to Patriot

$18.40

Summary_Quarterly_Financial_In2

Summary Quarterly Financial Information (Details) (USD $)	3 Months Ended																12 Months Ended			6 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jun. 30, 2014
Summary of the unaudited quarterly results of operations
Revenues	$1,684.50		$1,722.90		$1,758		$1,626.80		$1,742.80		$1,797.60		$1,725.30		$1,748		$6,792.20	$7,013.70	$8,077.50
Operating profit (loss)	-207		36.2		32.8		2.9		-552.2		112.2		26.4		88.8		-135.1	-324.8	172.5
Loss from continuing operations, net of income taxes	-478.8		-154		-72		-44.3		-401.1		24		101.4		-10.3		-749.1	-286	-470.9
Net loss	-513		-149		-71.2		-44.1		-561.2		-19.1		87.1		-19.4		-777.3	-512.6	-575.1
Net loss attributable to common stockholders	-514.6		-150.6		-73.3		-48.5		-565.7		-26.1		90.3		-23.4		-787	-524.9	-585.7
Basic and diluted EPS b continuing operations(1)	($1.79)	[1]	($0.58)	[1]	($0.28)	[1]	($0.18)	[1]	($1.52)	[2]	$0.06	[2]	$0.39	[2]	($0.05)	[2]	($2.83)	($1.12)	($1.80)
Diluted EPS b continuing operations(1)									($1.52)	[2]	$0.06	[2]	$0.39	[2]	($0.05)	[2]	($2.83)	($1.12)	($1.80)
Weighted average shares used in calculating basic and diluted EPS	268.2		268.2		268		267.9		267.3		267.2		266.9		266.9		268.1	267.1	268
Weighted average shares used in calculating diluted EPS									267.3		267.7		267.5		266.9		268.1	267.1	268
Summary Quarterly Financial Information (Textuals) [Abstract]
Additional charge recorded as a result of the damages awarded to Eagle in arbitration			10.6				15.6										-15.6
Remeasurement of foreign taxes	-1.2		1.2		1.3		1.4		6.2		2.6		37.1		-1.6		2.7	44.3	-7.9
Settlement charges related to the Patriot bankruptcy reorganization									30.6								0	30.6	0
Asset impairment and mine closure costs	154.4								506.8				21.5				154.4	528.3	929
Losses on extinguishment of debt											11.5		4.5		0.9			0
Tax benefit related to the settlement charges related to the Patriot bankruptcy reorganization									11.3
Net tax benefit from asset impairment and mine closure costs									112.8
Restructuring and pension settlement charges	26																26	11.9	0
Change in fair value of credit support provided to Patriot	34.1																34.1
Wilkie Creek [Domain]
Summary Quarterly Financial Information (Textuals) [Abstract]
Loss related to a discontinued operation									42.5		32.4
Air Quality [Member]
Summary Quarterly Financial Information (Textuals) [Abstract]
Loss related to a discontinued operation																			75
Settlement charges related to the Patriot bankruptcy reorganization [Member]
Summary Quarterly Financial Information (Textuals) [Abstract]
Loss related to a discontinued operation									61.8									61.8
Australia Deferred Tax Assets [Member]
Summary Quarterly Financial Information (Textuals) [Abstract]
Change in valuation allowance against loss carryforwards	90.4		80.6		75.7		42.6										289.3
Australian Mining [Member]
Summary of the unaudited quarterly results of operations
Revenues																	2,671.80	2,904.60	3,503.60
Summary Quarterly Financial Information (Textuals) [Abstract]
Asset impairment and mine closure costs																	78.6	390.8	806.7
US Deferred Tax Assets [Member]
Summary Quarterly Financial Information (Textuals) [Abstract]
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability																	280.1
Change in valuation allowance against loss carryforwards	280.1																351.2
Gulf Power Company Litigation [Member]
Summary Quarterly Financial Information (Textuals) [Abstract]
Litigation settlement													20.6
Prejudgment interest													6.9
Australian Minerals and Resource Rent Tax [Member]
Summary Quarterly Financial Information (Textuals) [Abstract]
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability			70.1																	54
Junior Subordinated Debt [Member]
Summary Quarterly Financial Information (Textuals) [Abstract]
Refinancing charges classified as interest expense					1.6												1.6
Western U.S. Mining Segment Customer [Member] \| Positive Outcome of Litigation [Member]
Summary Quarterly Financial Information (Textuals) [Abstract]
Contracts Revenue					43.2												33.5
Interest In Middlemount Coal Pty Limited [Member]
Summary Quarterly Financial Information (Textuals) [Abstract]
Change in valuation allowance against loss carryforwards	($52.30)

[1]	EPS for the quarters may not sum to the amounts for the year as each period is computed on a discrete basis.
[2]	EPS for the quarters may not sum to the amounts for the year as each period is computed on a discrete basis

Segment_Information_Details

Segment Information (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating segment results
Revenues	$1,684.50	$1,722.90	$1,758	$1,626.80	$1,742.80	$1,797.60	$1,725.30	$1,748	$6,792.20	$7,013.70	$8,077.50
Adjusted EBITDA									814	1,047.20	1,836.50
Total assets	13,191.10				14,133.40				13,191.10	14,133.40	15,809
Property, plant, equipment and mine development, net	10,577.30				11,082.50				10,577.30	11,082.50	11,801.70
Additions to property, plant, equipment, and mine development									194.4	328.4	986
Federal coal lease expenditures									276.7	276.8	276.5
Loss from equity affiliates									107.6	40.2	61.2
Reconciliation Of Adjusted EBITDA To Consolidated Loss From Continuing Operations [Abstract]
Adjusted EBITDA									814	1,047.20	1,836.50
Depreciation, depletion and amortization									-655.7	-740.3	-663.4
Asset retirement obligation expenses									-81	-66.5	-67
Asset impairment and mine closure costs	-154.4				-506.8		-21.5		-154.4	-528.3	-929
Settlement charges related to the Patriot bankruptcy reorganization					-30.6				0	-30.6	0
Amortization of basis related to equity affiliates									-5.7	-6.3	-4.6
Interest expense									-428.2	-425.2	-405.6
Interest income									15.4	15.7	24.5
Income tax (provision) benefit									-201.2	448.3	-262.3
Loss from continuing operations, net of income taxes	-478.8	-154	-72	-44.3	-401.1	24	101.4	-10.3	-749.1	-286	-470.9
Revenue from external customers by geographic region
Revenue percentage									100.00%	100.00%	100.00%
U.S. [Member]
Revenue from external customers by geographic region
Revenue percentage									59.50%	61.10%	55.40%
Japan [Member]
Revenue from external customers by geographic region
Revenue percentage									9.50%	9.80%	12.30%
China [Member]
Revenue from external customers by geographic region
Revenue percentage									6.10%	10.20%	6.80%
South Korea [Member]
Revenue from external customers by geographic region
Revenue percentage									5.20%	3.80%	5.80%
Other [Member]
Revenue from external customers by geographic region
Revenue percentage									19.70%	15.10%	19.70%
Western U.S. Mining [Member]
Operating segment results
Revenues									2,825.70	2,669.60	2,949.30
Adjusted EBITDA									770.4	698.3	832.8
Total assets	3,431.30				3,307.60				3,431.30	3,307.60	3,257.90
Property, plant, equipment and mine development, net	3,127.80				2,986.80				3,127.80	2,986.80	2,896.10
Additions to property, plant, equipment, and mine development									37.9	48	121.4
Federal coal lease expenditures									276.7	276.8	276.5
Loss from equity affiliates									0	0	0
Reconciliation Of Adjusted EBITDA To Consolidated Loss From Continuing Operations [Abstract]
Adjusted EBITDA									770.4	698.3	832.8
Asset impairment and mine closure costs									-2.7		-2.4
Midwestern U.S. Mining [Member]
Operating segment results
Revenues									1,198.10	1,335.50	1,403.70
Adjusted EBITDA									301.4	428.3	427
Total assets	667.8				716.8				667.8	716.8	728.5
Property, plant, equipment and mine development, net	612.1				667.6				612.1	667.6	707.5
Additions to property, plant, equipment, and mine development									57.4	27.2	74.7
Federal coal lease expenditures									0	0	0
Loss from equity affiliates									0	0	0
Reconciliation Of Adjusted EBITDA To Consolidated Loss From Continuing Operations [Abstract]
Adjusted EBITDA									301.4	428.3	427
Asset impairment and mine closure costs											-45
Australian Mining [Member]
Operating segment results
Revenues									2,671.80	2,904.60	3,503.60
Adjusted EBITDA									74.4	316.6	938.9
Total assets	6,623.90				7,081.20				6,623.90	7,081.20	7,990.80
Property, plant, equipment and mine development, net	5,503.70				5,947.10				5,503.70	5,947.10	6,595.50
Additions to property, plant, equipment, and mine development									84.1	230.3	743.4
Federal coal lease expenditures									0	0	0
Loss from equity affiliates									0	0	0
Reconciliation Of Adjusted EBITDA To Consolidated Loss From Continuing Operations [Abstract]
Adjusted EBITDA									74.4	316.6	938.9
Asset impairment and mine closure costs									-78.6	-390.8	-806.7
Trading and Brokerage [Member]
Operating segment results
Revenues									58.4	66	199.9
Adjusted EBITDA									14.9	-19.9	119.7
Total assets	300.7				389.6				300.7	389.6	543.9
Property, plant, equipment and mine development, net	1.1				1.8				1.1	1.8	1.6
Additions to property, plant, equipment, and mine development									0	0.1	0.1
Federal coal lease expenditures									0	0	0
Loss from equity affiliates									0	0	0
Reconciliation Of Adjusted EBITDA To Consolidated Loss From Continuing Operations [Abstract]
Adjusted EBITDA									14.9	-19.9	119.7
Corporate and Other [Member]
Operating segment results
Revenues									38.2	38	21
Adjusted EBITDA									-347.1	-376.1	-481.9
Total assets	2,167.40				2,638.20				2,167.40	2,638.20	3,287.90
Property, plant, equipment and mine development, net	1,332.60				1,479.20				1,332.60	1,479.20	1,601
Additions to property, plant, equipment, and mine development									15	22.8	46.4
Federal coal lease expenditures									0	0	0
Loss from equity affiliates									107.6	40.2	61.2
Reconciliation Of Adjusted EBITDA To Consolidated Loss From Continuing Operations [Abstract]
Adjusted EBITDA									-347.1	-376.1	-481.9
Asset impairment and mine closure costs									-73.1	-137.5	-74.9
Middlemount Mine [Member]
Reconciliation Of Adjusted EBITDA To Consolidated Loss From Continuing Operations [Abstract]
Change in valuation allowance against loss carryforwards									($52.30)	$0	$0

Supplemental_GuarantorNonGuara2

Supplemental Guarantor/Non-Guarantor Financial Information (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Audited Supplemental Condensed Consolidated Statements of Operations
Total revenues	$1,684.50	$1,722.90	$1,758	$1,626.80	$1,742.80	$1,797.60	$1,725.30	$1,748	$6,792.20	$7,013.70	$8,077.50
Costs and expenses
Operating costs and expenses (exclusive of items shown separately below)									5,716.90	5,729.10	5,932.70
Depreciation, depletion and amortization									655.7	740.3	663.4
Asset retirement obligation expenses									81	66.5	67
Selling and administrative expenses									227.1	244.2	268.8
Restructuring and pension settlement charges	26								26	11.9	0
Other operating (income) loss:
Net gain on disposal or exchange of assets									-41.4	-52.6	-17.1
Asset impairment and mine closure costs	154.4				506.8		21.5		154.4	528.3	929
Settlement charges related to the Patriot bankruptcy reorganization					30.6				0	30.6	0
Loss from equity affiliates and investment in subsidiaries									107.6	40.2	61.2
Interest expense									428.2	425.2	405.6
(Gain) loss from extinguishment of affiliate debt						11.5	4.5	0.9		0
Interest income									-15.4	-15.7	-24.5
Unrealized loss (gain) on derivatives										0	0
(Loss) income from continuing operations before income taxes									-547.9	-734.3	-208.6
Income tax provision (benefit)									201.2	-448.3	262.3
(Loss) income from continuing operations, net of income taxes	-478.8	-154	-72	-44.3	-401.1	24	101.4	-10.3	-749.1	-286	-470.9
(Loss) income from discontinued operations, net of income taxes									-28.2	-226.6	-104.2
Net (loss) income	-513	-149	-71.2	-44.1	-561.2	-19.1	87.1	-19.4	-777.3	-512.6	-575.1
Less: Net income attributable to noncontrolling interests									9.7	12.3	10.6
Net (loss) income attributable to common stockholders	-514.6	-150.6	-73.3	-48.5	-565.7	-26.1	90.3	-23.4	-787	-524.9	-585.7
Parent Company [Member]
Audited Supplemental Condensed Consolidated Statements of Operations
Total revenues									0	0	0
Costs and expenses
Operating costs and expenses (exclusive of items shown separately below)									49.6	-173.6	-395.2
Depreciation, depletion and amortization									0	0	0
Asset retirement obligation expenses									0	0	0
Selling and administrative expenses									46.8	50.9	38.7
Restructuring and pension settlement charges									0	0
Other operating (income) loss:
Net gain on disposal or exchange of assets									0	0	0
Asset impairment and mine closure costs									4.7	21.5	35.5
Settlement charges related to the Patriot bankruptcy reorganization										30.6
Loss from equity affiliates and investment in subsidiaries									431.1	272.5	720
Interest expense									424.7	420.8	413.9
(Gain) loss from extinguishment of affiliate debt										0
Interest income									-15.3	-79.6	-309.8
Unrealized loss (gain) on derivatives										0	0
(Loss) income from continuing operations before income taxes									-941.6	-543.1	-503.1
Income tax provision (benefit)									-186.2	-92.2	80.2
(Loss) income from continuing operations, net of income taxes									-755.4	-450.9	-583.3
(Loss) income from discontinued operations, net of income taxes									-31.6	-74	-2.4
Net (loss) income									-787	-524.9	-585.7
Less: Net income attributable to noncontrolling interests									0	0	0
Net (loss) income attributable to common stockholders									-787	-524.9	-585.7
Guarantor Subsidiaries [Member]
Audited Supplemental Condensed Consolidated Statements of Operations
Total revenues									3,964.80	4,027.90	4,571.30
Costs and expenses
Operating costs and expenses (exclusive of items shown separately below)									2,927.30	3,471.70	3,344.10
Depreciation, depletion and amortization									310.4	329.4	315.6
Asset retirement obligation expenses									25.3	33.3	42.9
Selling and administrative expenses									161.1	167.9	199.7
Restructuring and pension settlement charges									23.8	11.9
Other operating (income) loss:
Net gain on disposal or exchange of assets									-18.5	-52.6	-14.7
Asset impairment and mine closure costs									71.1	6.5	86.8
Settlement charges related to the Patriot bankruptcy reorganization										0
Loss from equity affiliates and investment in subsidiaries									6.6	8.3	12.5
Interest expense									6.4	244.5	13.9
(Gain) loss from extinguishment of affiliate debt										-155.5
Interest income									-10.3	-311.6	-149.1
Unrealized loss (gain) on derivatives										34	-35.3
(Loss) income from continuing operations before income taxes									461.6	240.1	754.9
Income tax provision (benefit)									316.7	-110.9	105.8
(Loss) income from continuing operations, net of income taxes									144.9	351	649.1
(Loss) income from discontinued operations, net of income taxes									-7.2	-5.6	-82.2
Net (loss) income									137.7	345.4	566.9
Less: Net income attributable to noncontrolling interests									0	0	0
Net (loss) income attributable to common stockholders									137.7	345.4	566.9
Non-Guarantor Subsidiaries [Member]
Audited Supplemental Condensed Consolidated Statements of Operations
Total revenues									2,902.10	3,230.30	3,738.40
Costs and expenses
Operating costs and expenses (exclusive of items shown separately below)									2,814.70	2,675.50	3,216
Depreciation, depletion and amortization									345.3	410.9	347.8
Asset retirement obligation expenses									55.7	33.2	24.1
Selling and administrative expenses									19.2	25.4	30.4
Restructuring and pension settlement charges									2.2	0
Other operating (income) loss:
Net gain on disposal or exchange of assets									-22.9	0	-2.4
Asset impairment and mine closure costs									78.6	500.3	806.7
Settlement charges related to the Patriot bankruptcy reorganization										0
Loss from equity affiliates and investment in subsidiaries									101	31.9	48.7
Interest expense									34.6	169	475.6
(Gain) loss from extinguishment of affiliate debt										155.5
Interest income									-27.3	-33.6	-63.4
Unrealized loss (gain) on derivatives										-34	35.3
(Loss) income from continuing operations before income taxes									-499	-703.8	-1,180.40
Income tax provision (benefit)									70.7	-245.2	76.3
(Loss) income from continuing operations, net of income taxes									-569.7	-458.6	-1,256.70
(Loss) income from discontinued operations, net of income taxes									10.6	-147	-19.6
Net (loss) income									-559.1	-605.6	-1,276.30
Less: Net income attributable to noncontrolling interests									9.7	12.3	10.6
Net (loss) income attributable to common stockholders									-568.8	-617.9	-1,286.90
Eliminations [Member]
Audited Supplemental Condensed Consolidated Statements of Operations
Total revenues									-74.7	-244.5	-232.2
Costs and expenses
Operating costs and expenses (exclusive of items shown separately below)									-74.7	-244.5	-232.2
Depreciation, depletion and amortization									0	0	0
Asset retirement obligation expenses									0	0	0
Selling and administrative expenses									0	0	0
Restructuring and pension settlement charges									0	0
Other operating (income) loss:
Net gain on disposal or exchange of assets									0	0	0
Asset impairment and mine closure costs									0	0	0
Settlement charges related to the Patriot bankruptcy reorganization										0
Loss from equity affiliates and investment in subsidiaries									-431.1	-272.5	-720
Interest expense									-37.5	-409.1	-497.8
(Gain) loss from extinguishment of affiliate debt										0
Interest income									37.5	409.1	497.8
Unrealized loss (gain) on derivatives										0	0
(Loss) income from continuing operations before income taxes									431.1	272.5	720
Income tax provision (benefit)									0	0	0
(Loss) income from continuing operations, net of income taxes									431.1	272.5	720
(Loss) income from discontinued operations, net of income taxes									0	0	0
Net (loss) income									431.1	272.5	720
Less: Net income attributable to noncontrolling interests									0	0	0
Net (loss) income attributable to common stockholders									$431.10	$272.50	$720

Supplemental_GuarantorNonGuara3

Supplemental Guarantor/Non-Guarantor Financial Information (Details 1) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Financial Statements, Captions [Line Items]
Acquisition of MCG Coal Holdings Pty Ltd noncontrolling interests	$0	$0	$49.80
Current assets
Cash and cash equivalents	298	444	558.8	799.1
Accounts receivable, net	563.1	557.9
Receivables from affiliates, net	0	0
Inventories	406.5	506.7
Assets from coal trading activities, net	57.6	36.1
Deferred income taxes	80	66.4
Other current assets	305.8	381.6
Total current assets	1,711	1,992.70
Property, plant, equipment and mine development, net	10,577.30	11,082.50	11,801.70
Deferred income taxes	0.7	7.8
Investments and other assets	902.1	1,050.40
Notes receivable from affiliates, net	0	0
Total assets	13,191.10	14,133.40	15,809
Current liabilities
Current maturities of long-term debt	21.2	31.7
Payables to affiliates, net	0	0
Deferred income taxes		0
Liabilities from coal trading activities, net	32.7	6.1
Accounts payable and accrued expenses	1,809.20	1,764
Total current liabilities	1,863.10	1,801.80
Long-term debt, less current maturities	5,965.60	5,970.70
Deferred income taxes	89.1	40.9
Notes payable to affiliates, net	0	0
Other noncurrent liabilities	2,546.80	2,372.10
Total liabilities	10,464.60	10,185.50
Peabody Energy Corporation's stockholders' equity	2,724.80	3,908.70
Noncontrolling interests	1.7	39.2
Total stockholders' equity	2,726.50	3,947.90	4,938.80	5,515.80
Total liabilities and stockholders' equity	13,191.10	14,133.40
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Acquisition of MCG Coal Holdings Pty Ltd noncontrolling interests			0
Current assets
Cash and cash equivalents	188.7	300.7	269.6	283.2
Accounts receivable, net	0	1.3
Receivables from affiliates, net	258.4	68.4
Inventories	0	0
Assets from coal trading activities, net	0	0
Deferred income taxes	64.5	0
Other current assets	0	34.5
Total current assets	511.6	404.9
Property, plant, equipment and mine development, net	0	0
Deferred income taxes	0	16.5
Investments and other assets	10,209.40	11,394.90
Notes receivable from affiliates, net	0	0
Total assets	10,721	11,816.30
Current liabilities
Current maturities of long-term debt	12	12
Payables to affiliates, net	0	0
Deferred income taxes		1.9
Liabilities from coal trading activities, net	0	0
Accounts payable and accrued expenses	474.5	360
Total current liabilities	486.5	373.9
Long-term debt, less current maturities	5,951.60	5,959.10
Deferred income taxes	90.5	0
Notes payable to affiliates, net	1,033.40	1,032.60
Other noncurrent liabilities	434.2	542
Total liabilities	7,996.20	7,907.60
Peabody Energy Corporation's stockholders' equity	2,724.80	3,908.70
Noncontrolling interests	0	0
Total stockholders' equity	2,724.80	3,908.70
Total liabilities and stockholders' equity	10,721	11,816.30
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Acquisition of MCG Coal Holdings Pty Ltd noncontrolling interests			0
Current assets
Cash and cash equivalents	1.2	0.3	0.3	0.8
Accounts receivable, net	14.5	0
Receivables from affiliates, net	0	0
Inventories	191.8	235.1
Assets from coal trading activities, net	53.8	46.7
Deferred income taxes	8.6	61.9
Other current assets	44.5	73.7
Total current assets	314.4	417.7
Property, plant, equipment and mine development, net	5,005.20	5,055.70
Deferred income taxes	8.2	0
Investments and other assets	4	8.8
Notes receivable from affiliates, net	1,655.70	1,433
Total assets	6,987.50	6,915.20
Current liabilities
Current maturities of long-term debt	0.1	0.1
Payables to affiliates, net	364.3	10.4
Deferred income taxes		0
Liabilities from coal trading activities, net	10.7	0.2
Accounts payable and accrued expenses	682.5	601.4
Total current liabilities	1,057.60	612.1
Long-term debt, less current maturities	6.3	6.5
Deferred income taxes	0	55.9
Notes payable to affiliates, net	0	0
Other noncurrent liabilities	1,717.40	1,452.50
Total liabilities	2,781.30	2,127
Peabody Energy Corporation's stockholders' equity	4,206.20	4,788.20
Noncontrolling interests	0	0
Total stockholders' equity	4,206.20	4,788.20
Total liabilities and stockholders' equity	6,987.50	6,915.20
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Acquisition of MCG Coal Holdings Pty Ltd noncontrolling interests			-49.8
Current assets
Cash and cash equivalents	108.1	143	288.9	515.1
Accounts receivable, net	548.6	559.1
Receivables from affiliates, net	105.9	0
Inventories	214.7	271.6
Assets from coal trading activities, net	3.8	0
Deferred income taxes	6.9	6.4
Other current assets	261.3	273.4
Total current assets	1,249.30	1,253.50
Property, plant, equipment and mine development, net	5,572.10	6,026.80
Deferred income taxes	0	7.8
Investments and other assets	621.6	762.6
Notes receivable from affiliates, net	0	0
Total assets	7,443	8,050.70
Current liabilities
Current maturities of long-term debt	9.1	19.6
Payables to affiliates, net	0	58
Deferred income taxes		0
Liabilities from coal trading activities, net	22	16.5
Accounts payable and accrued expenses	652.2	805.1
Total current liabilities	683.3	899.2
Long-term debt, less current maturities	7.7	5.1
Deferred income taxes	6.1	1.5
Notes payable to affiliates, net	622.3	400.4
Other noncurrent liabilities	395.2	377.6
Total liabilities	1,714.60	1,683.80
Peabody Energy Corporation's stockholders' equity	5,726.70	6,327.70
Noncontrolling interests	1.7	39.2
Total stockholders' equity	5,728.40	6,366.90
Total liabilities and stockholders' equity	7,443	8,050.70
Eliminations [Member]
Current assets
Cash and cash equivalents	0	0
Accounts receivable, net	0	-2.5
Receivables from affiliates, net	-364.3	-68.4
Inventories	0	0
Assets from coal trading activities, net	0	-10.6
Deferred income taxes	0	-1.9
Other current assets	0	0
Total current assets	-364.3	-83.4
Property, plant, equipment and mine development, net	0	0
Deferred income taxes	-7.5	-16.5
Investments and other assets	-9,932.90	-11,115.90
Notes receivable from affiliates, net	-1,655.70	-1,433
Total assets	-11,960.40	-12,648.80
Current liabilities
Current maturities of long-term debt	0	0
Payables to affiliates, net	-364.3	-68.4
Deferred income taxes		-1.9
Liabilities from coal trading activities, net	0	-10.6
Accounts payable and accrued expenses	0	-2.5
Total current liabilities	-364.3	-83.4
Long-term debt, less current maturities	0	0
Deferred income taxes	-7.5	-16.5
Notes payable to affiliates, net	-1,655.70	-1,433
Other noncurrent liabilities	0	0
Total liabilities	-2,027.50	-1,532.90
Peabody Energy Corporation's stockholders' equity	-9,932.90	-11,115.90
Noncontrolling interests	0	0
Total stockholders' equity	-9,932.90	-11,115.90
Total liabilities and stockholders' equity	($11,960.40)	($12,648.80)

Supplemental_GuarantorNonGuara4

Supplemental Guarantor/Non-Guarantor Financial Information (Details 2) (USD $)	3 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash Flows From Operating Activities
Net cash (used in) provided by continuing operations		$441,000,000	$780,100,000	$1,599,800,000
Net cash used in discontinued operations		-104,400,000	-57,700,000	-84,700,000
Net cash (used in) provided by operating activities		336,600,000	722,400,000	1,515,100,000
Cash Flows From Investing Activities
Additions to property, plant, equipment and mine development		-194,400,000	-328,400,000	-986,000,000
Changes in accrued expenses related to capital expenditures		-16,600,000	-120,700,000	104,700,000
Federal coal lease expenditures		276,700,000	276,800,000	276,500,000
Investment in Prairie State Energy Campus		0	0	-10,700,000
Proceeds from disposal of assets, net of notes receivable		203,700,000	178,300,000	147,900,000
Purchases of debt and equity securities		-15,100,000	-22,800,000	-46,700,000
Proceeds from sales and maturities of debt and equity securities		13,500,000	22,900,000	46,400,000
Purchases of short-term investments		0	0	-4,800,000
Maturity of short-term investments		0	4,800,000	0
Contributions to joint ventures		-529,800,000	-671,700,000	-824,000,000
Distributions from joint ventures		534,200,000	722,900,000	823,000,000
Advances to related parties		-33,700,000	-42,100,000	-148,000,000
Repayment of loans from related parties		5,400,000	25,200,000	110,800,000
Other, net		-5,000,000	-5,800,000	-6,200,000
Net cash used in continuing operations		-314,500,000	-514,200,000	-1,070,100,000
Net cash used in discontinued operations		0	-1,500,000	-22,000,000
Net cash used in investing activities		-314,500,000	-515,700,000	-1,092,100,000
Cash Flows From Financing Activities
Proceeds from long-term debt		1,100,000	1,188,000,000	800,000
Repayments of long-term debt		-21,000,000	-1,390,200,000	-415,800,000
Payment of deferred financing costs		-10,100,000	-22,800,000	-6,900,000
Dividends paid		-92,300,000	-91,700,000	-91,900,000
Restricted cash for distributions to noncontrolling interests		-42,500,000	0	0
Common stock repurchase	-99,900,000	0	0	-99,900,000
Excess tax benefit related to share-based compensation		0	0	8,300,000
Acquisition of MCG Coal Holdings Pty Ltd noncontrolling interests		0	0	49,800,000
Other, net		-3,300,000	-4,800,000	-8,100,000
Transactions with affiliates, net		0	0	0
Net cash provided by (used in) financing activities		-168,100,000	-321,500,000	-663,300,000
Net change in cash and cash equivalents		-146,000,000	-114,800,000	-240,300,000
Cash and cash equivalents at beginning of year		444,000,000	558,800,000	799,100,000
Cash and cash equivalents at end of year		298,000,000	444,000,000	558,800,000
Parent Company [Member]
Cash Flows From Operating Activities
Net cash (used in) provided by continuing operations		-369,000,000	-24,300,000	372,000,000
Net cash used in discontinued operations		-73,300,000	-20,400,000	-3,400,000
Net cash (used in) provided by operating activities		-442,300,000	-44,700,000	368,600,000
Cash Flows From Investing Activities
Additions to property, plant, equipment and mine development		0	0	0
Changes in accrued expenses related to capital expenditures		0	0	0
Federal coal lease expenditures		0	0	0
Investment in Prairie State Energy Campus				0
Proceeds from disposal of assets, net of notes receivable		0	0	0
Purchases of debt and equity securities		0	0	0
Proceeds from sales and maturities of debt and equity securities		0	0	0
Purchases of short-term investments				0
Maturity of short-term investments			0
Contributions to joint ventures		0	0	0
Distributions from joint ventures		0	0	0
Advances to related parties		0	0	0
Repayment of loans from related parties		0	0	0
Other, net		0	0	0
Net cash used in continuing operations			0	0
Net cash used in discontinued operations			0	0
Net cash used in investing activities		0	0	0
Cash Flows From Financing Activities
Proceeds from long-term debt		0	1,188,000,000	0
Repayments of long-term debt		-12,000,000	-1,334,200,000	-379,000,000
Payment of deferred financing costs		-10,100,000	-22,800,000	-6,900,000
Dividends paid		-92,300,000	-91,700,000	-91,900,000
Restricted cash for distributions to noncontrolling interests		0
Common stock repurchase				-99,900,000
Excess tax benefit related to share-based compensation				8,300,000
Acquisition of MCG Coal Holdings Pty Ltd noncontrolling interests				0
Other, net		3,100,000	4,200,000	1,000,000
Transactions with affiliates, net		441,600,000	332,300,000	186,200,000
Net cash provided by (used in) financing activities		330,300,000	75,800,000	-382,200,000
Net change in cash and cash equivalents		-112,000,000	31,100,000	-13,600,000
Cash and cash equivalents at beginning of year		300,700,000	269,600,000	283,200,000
Cash and cash equivalents at end of year		188,700,000	300,700,000	269,600,000
Guarantor Subsidiaries [Member]
Cash Flows From Operating Activities
Net cash (used in) provided by continuing operations		776,100,000	778,700,000	1,390,300,000
Net cash used in discontinued operations		-4,600,000	-7,600,000	-11,600,000
Net cash (used in) provided by operating activities		771,500,000	771,100,000	1,378,700,000
Cash Flows From Investing Activities
Additions to property, plant, equipment and mine development		-108,500,000	-95,900,000	-237,400,000
Changes in accrued expenses related to capital expenditures		3,400,000	-1,200,000	3,100,000
Federal coal lease expenditures		-276,700,000	-276,800,000	-276,500,000
Investment in Prairie State Energy Campus				-10,700,000
Proceeds from disposal of assets, net of notes receivable		105,900,000	93,000,000	70,100,000
Purchases of debt and equity securities		0	0	0
Proceeds from sales and maturities of debt and equity securities		0	0	0
Purchases of short-term investments				0
Maturity of short-term investments			0
Contributions to joint ventures		0	0	0
Distributions from joint ventures		0	0	0
Advances to related parties		0	0	0
Repayment of loans from related parties		0	0	0
Other, net		-4,400,000	-5,700,000	-6,200,000
Net cash used in continuing operations			-286,600,000	-457,600,000
Net cash used in discontinued operations			0	-1,100,000
Net cash used in investing activities		-280,300,000	-286,600,000	-458,700,000
Cash Flows From Financing Activities
Proceeds from long-term debt		0	0	0
Repayments of long-term debt		-100,000	-200,000	-400,000
Payment of deferred financing costs		0	0	0
Dividends paid		0	0	0
Restricted cash for distributions to noncontrolling interests		0
Common stock repurchase				0
Excess tax benefit related to share-based compensation				0
Acquisition of MCG Coal Holdings Pty Ltd noncontrolling interests				0
Other, net		-1,700,000	-1,600,000	0
Transactions with affiliates, net		-488,500,000	-482,700,000	-920,100,000
Net cash provided by (used in) financing activities		-490,300,000	-484,500,000	-920,500,000
Net change in cash and cash equivalents		900,000	0	-500,000
Cash and cash equivalents at beginning of year		300,000	300,000	800,000
Cash and cash equivalents at end of year		1,200,000	300,000	300,000
Non-Guarantor Subsidiaries [Member]
Cash Flows From Operating Activities
Net cash (used in) provided by continuing operations		33,900,000	25,700,000	-162,500,000
Net cash used in discontinued operations		-26,500,000	-29,700,000	-69,700,000
Net cash (used in) provided by operating activities		7,400,000	-4,000,000	-232,200,000
Cash Flows From Investing Activities
Additions to property, plant, equipment and mine development		-85,900,000	-232,500,000	-748,600,000
Changes in accrued expenses related to capital expenditures		-20,000,000	-119,500,000	101,600,000
Federal coal lease expenditures		0	0	0
Investment in Prairie State Energy Campus				0
Proceeds from disposal of assets, net of notes receivable		97,800,000	85,300,000	77,800,000
Purchases of debt and equity securities		-15,100,000	-22,800,000	-46,700,000
Proceeds from sales and maturities of debt and equity securities		13,500,000	22,900,000	46,400,000
Purchases of short-term investments				-4,800,000
Maturity of short-term investments			4,800,000
Contributions to joint ventures		-529,800,000	-671,700,000	-824,000,000
Distributions from joint ventures		534,200,000	722,900,000	823,000,000
Advances to related parties		-33,700,000	-42,100,000	-148,000,000
Repayment of loans from related parties		5,400,000	25,200,000	110,800,000
Other, net		-600,000	-100,000	0
Net cash used in continuing operations			-227,600,000	-612,500,000
Net cash used in discontinued operations			-1,500,000	-20,900,000
Net cash used in investing activities		-34,200,000	-229,100,000	-633,400,000
Cash Flows From Financing Activities
Proceeds from long-term debt		1,100,000	0	800,000
Repayments of long-term debt		-8,900,000	-55,800,000	-36,400,000
Payment of deferred financing costs		0	0	0
Dividends paid		0	0	0
Restricted cash for distributions to noncontrolling interests		-42,500,000
Common stock repurchase
Excess tax benefit related to share-based compensation				0
Acquisition of MCG Coal Holdings Pty Ltd noncontrolling interests				-49,800,000
Other, net		-4,700,000	-7,400,000	-9,100,000
Transactions with affiliates, net		46,900,000	150,400,000	733,900,000
Net cash provided by (used in) financing activities		-8,100,000	87,200,000	639,400,000
Net change in cash and cash equivalents		-34,900,000	-145,900,000	-226,200,000
Cash and cash equivalents at beginning of year		143,000,000	288,900,000	515,100,000
Cash and cash equivalents at end of year		$108,100,000	$143,000,000	$288,900,000

Supplemental_GuarantorNonGuara5

Supplemental Guarantor/Non-Guarantor Financial Information Supplemental Guarantor/Non-Guarantor Financial Information (Details 3) (USD $)	3 Months Ended								12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Net (loss) income	($513)	($149)	($71.20)	($44.10)	($561.20)	($19.10)	$87.10	($19.40)	($777.30)	($512.60)	($575.10)
Unrealized holding losses on available-for-sale securities									-3.7	-12.3	-15.5
Reclassification for realized losses included in net (loss) income									-2.9	-12.8	-22.5
Net change in unrealized (losses) gains on available-for-sale securities									-0.8	0.5	7
(Decrease) increase in fair value of cash flow hedges									-195	-333.6	350.4
Reclassification for realized gains (losses) included in net (loss) income									10.2	209.6	298.6
Net unrealized (losses) gains on cash flow hedges									-205.2	-543.2	51.8
Prior service credit (cost) for the period									11.4	-1.4	20.1
Net actuarial (loss) gain for the period									-142.7	110.9	0
Amortization of actuarial loss and prior service cost included in net (loss) income									32.7	95.7	55.4
Postretirement plans and workers' compensation obligations									-98.6	205.2	75.5
Foreign currency translation adjustment									-41	-92.7	19.1
Other comprehensive loss from investment in subsidiaries									0	0	0
Other comprehensive (loss) income, net of income taxes									-345.6	-430.2	153.4
Comprehensive loss									-1,122.90	-942.8	-421.7
Less: Comprehensive income attributable to noncontrolling interests									9.7	12.3	10.6
Comprehensive loss attributable to common stockholders									-1,132.60	-955.1	-432.3
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Net (loss) income									-787	-524.9	-585.7
Unrealized holding losses on available-for-sale securities									-3.7	-12.2	-15.5
Reclassification for realized losses included in net (loss) income									-2.9	-13	-22.5
Net change in unrealized (losses) gains on available-for-sale securities									-0.8	0.8	7
(Decrease) increase in fair value of cash flow hedges									-225.9	-368.4	205.9
Reclassification for realized gains (losses) included in net (loss) income									-31.3	109	249.1
Net unrealized (losses) gains on cash flow hedges									-194.6	-477.4	-43.2
Prior service credit (cost) for the period									0	0	0
Net actuarial (loss) gain for the period									0	0	0
Amortization of actuarial loss and prior service cost included in net (loss) income									0	0	0
Postretirement plans and workers' compensation obligations									0	0	0
Foreign currency translation adjustment									0	0	0
Other comprehensive loss from investment in subsidiaries									-150.2	46.4	189.6
Other comprehensive (loss) income, net of income taxes									-345.6	-430.2	153.4
Comprehensive loss									-1,132.60	-955.1	-432.3
Less: Comprehensive income attributable to noncontrolling interests									0	0	0
Comprehensive loss attributable to common stockholders									-1,132.60	-955.1	-432.3
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net (loss) income									137.7	345.4	566.9
Unrealized holding losses on available-for-sale securities									0	0	0
Reclassification for realized losses included in net (loss) income									0	0	0
Net change in unrealized (losses) gains on available-for-sale securities									0	0	0
(Decrease) increase in fair value of cash flow hedges									0	0	0
Reclassification for realized gains (losses) included in net (loss) income									0	0	0
Net unrealized (losses) gains on cash flow hedges									0	0	0
Prior service credit (cost) for the period									11.4	-1.4	20.1
Net actuarial (loss) gain for the period									-150.2	103.8	-0.9
Amortization of actuarial loss and prior service cost included in net (loss) income									35.5	95.8	54.5
Postretirement plans and workers' compensation obligations									-103.3	198.2	73.7
Foreign currency translation adjustment									0	0	0
Other comprehensive loss from investment in subsidiaries									0	0	0
Other comprehensive (loss) income, net of income taxes									-103.3	198.2	73.7
Comprehensive loss									34.4	543.6	640.6
Less: Comprehensive income attributable to noncontrolling interests									0	0	0
Comprehensive loss attributable to common stockholders									34.4	543.6	640.6
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net (loss) income									-559.1	-605.6	-1,276.30
Unrealized holding losses on available-for-sale securities									0	-0.1	0
Reclassification for realized losses included in net (loss) income									0	0.2	0
Net change in unrealized (losses) gains on available-for-sale securities									0	-0.3	0
(Decrease) increase in fair value of cash flow hedges									30.9	34.8	144.5
Reclassification for realized gains (losses) included in net (loss) income									41.5	100.6	49.5
Net unrealized (losses) gains on cash flow hedges									-10.6	-65.8	95
Prior service credit (cost) for the period									0	0	0
Net actuarial (loss) gain for the period									7.5	7.1	0.9
Amortization of actuarial loss and prior service cost included in net (loss) income									-2.8	-0.1	0.9
Postretirement plans and workers' compensation obligations									4.7	7	1.8
Foreign currency translation adjustment									-41	-92.7	19.1
Other comprehensive loss from investment in subsidiaries									0	0	0
Other comprehensive (loss) income, net of income taxes									-46.9	-151.8	115.9
Comprehensive loss									-606	-757.4	-1,160.40
Less: Comprehensive income attributable to noncontrolling interests									9.7	12.3	10.6
Comprehensive loss attributable to common stockholders									-615.7	-769.7	-1,171
Consolidation, Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net (loss) income									431.1	272.5	720
Unrealized holding losses on available-for-sale securities									0	0	0
Reclassification for realized losses included in net (loss) income									0	0	0
Net change in unrealized (losses) gains on available-for-sale securities									0	0	0
(Decrease) increase in fair value of cash flow hedges									0	0	0
Reclassification for realized gains (losses) included in net (loss) income									0	0	0
Net unrealized (losses) gains on cash flow hedges									0	0	0
Prior service credit (cost) for the period									0	0	0
Net actuarial (loss) gain for the period									0	0	0
Amortization of actuarial loss and prior service cost included in net (loss) income									0	0	0
Postretirement plans and workers' compensation obligations									0	0	0
Foreign currency translation adjustment									0	0	0
Other comprehensive loss from investment in subsidiaries									150.2	-46.4	-189.6
Other comprehensive (loss) income, net of income taxes									150.2	-46.4	-189.6
Comprehensive loss									581.3	226.1	530.4
Less: Comprehensive income attributable to noncontrolling interests									0	0	0
Comprehensive loss attributable to common stockholders									$581.30	$226.10	$530.40

Supplemental_GuarantorNonGuara6

Supplemental Guarantor/Non-Guarantor Financial Information (Details Textuals)	12 Months Ended
	Dec. 31, 2014
Guarantor/Non-Guarantor [Line Items]
Percent of ownership of certain U.S. subsidiaries that fully and unconditionally guarantee the Senior Notes	100.00%
7.375% Senior Notes Member
Guarantor/Non-Guarantor [Line Items]
Stated interest rate - percentage	7.38%
6.00% Senior Notes [Member]
Guarantor/Non-Guarantor [Line Items]
Stated interest rate - percentage	6.00%
6.50% Senior Notes [Member]
Guarantor/Non-Guarantor [Line Items]
Stated interest rate - percentage	6.50%
6.25% Senior Notes [Member]
Guarantor/Non-Guarantor [Line Items]
Stated interest rate - percentage	6.25%
7.875% Senior Notes [Member]
Guarantor/Non-Guarantor [Line Items]
Stated interest rate - percentage	7.88%

Valuation_and_Qualifying_Accou2

Valuation and Qualifying Accounts (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Advance royalty recoupment reserve [Member]
Valuation and Qualifying Accounts
Balance at Beginning of Period	$9.70		$15.30		$21.30
Charged to Costs and Expenses	-0.2		0.1		2.9
Deductions	-1.9	[1],[2]	-5.7	[1],[2]	-9	[1],[2]
Other	0		0		0.1	[3]
Balance at End of Period	7.6		9.7		15.3
Reserve for materials and supplies [Member]
Valuation and Qualifying Accounts
Balance at Beginning of Period	7.4		16		6.5
Charged to Costs and Expenses	-0.1		1.7		13.7
Deductions	-2.7	[1]	-10.3	[1]	-4.2	[1]
Other	0		0		0
Balance at End of Period	4.6		7.4		16
Allowance for doubtful accounts [Member]
Valuation and Qualifying Accounts
Balance at Beginning of Period	7.4		13.7		17
Charged to Costs and Expenses	1.5		4.3		-0.5
Deductions	-1.4	[1]	-10.1	[1]	-0.7	[1]
Other	-1.7	[4]	-0.5	[4]	-2.1	[4]
Balance at End of Period	5.8		7.4		13.7
Tax valuation allowances [Member]
Valuation and Qualifying Accounts
Balance at Beginning of Period	1,634.10		1,481.80		79.8
Charged to Costs and Expenses	569.4		-29.4		521.5
Deductions	0	[1]	0	[1]	-77	[1],[5]
Other	-1,034.50	[6]	181.7	[7]	957.5	[8]
Balance at End of Period	$1,169		$1,634.10		$1,481.80

[1]	Reserves utilized, unless otherwise indicated.
[2]	Deductions to advance royalty recoupment reserve represents the termination of federal and state leases.
[3]	Balances transferred from other accounts or reserves recorded as part of a property transaction or acquisition.
[4]	Represents subsequent recovery of receivable amounts previously reserved.
[5]	Deductions include write-off of loss carryforwards and reversal of related valuation allowances.
[6]	Includes the write-off of valuation allowance against deferred tax assets related to the Australian Minerals and Resource Rent Tax (MRRT) due to the repeal of that legislation in 2014, along with an increase in valuation allowance during the period reflected directly in "Accumulated other comprehensive loss" and the impact of the 2014 decrease in Australian dollar exchange rates.
[7]	Related to the MRRT, as offset by the impact of the 2013 decrease in Australian dollar exchange rates.
[8]	Includes changes to valuation allowances primarily related to deferred tax assets acquired in business combinations and initial deferred tax assets resulting from the MRRT implemented in Australia in 2012.