Peabody Energy (BTU) 10-Q 8 Aug 14 2014 Q2 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information Document	6 Months Ended
	Jun. 30, 2014	Aug. 01, 2014
Document and Entity Information [Abstract]	'	'
Entity Registrant Name	'PEABODY ENERGY CORP	'
Entity Central Index Key	'0001064728	'
Document Type	'10-Q	'
Document Period End Date	30-Jun-14	'
Amendment Flag	'false	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q2	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	271,464,148

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Operations (Unaudited) (USD $)	3 Months Ended		6 Months Ended
In Millions, except Per Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Revenues	'	'	'	'
Sales	$1,598.60	$1,588.60	$3,068.80	$3,165.80
Other revenues	159.4	136.7	316	307.5
Total revenues	1,758	1,725.30	3,384.80	3,473.30
Costs and expenses	'	'	'	'
Operating costs and expenses (exclusive of items shown separately below)	1,467.60	1,437.20	2,862.40	2,826.60
Depreciation, depletion and amortization	163.1	185.7	320.3	356.4
Asset retirement obligation expenses	15.9	18.3	31.5	37.3
Selling and administrative expenses	59.2	64	118.7	129.1
Other operating (income) loss:	'	'	'	'
Net gain on disposal or exchange of assets	-2.2	-43.2	-12	-45.8
Asset impairment	0	21.5	0	21.5
Loss from equity affiliates	21.6	15.4	28.2	33
Operating profit	32.8	26.4	35.7	115.2
Interest expense	105.2	110.8	208.5	212.1
Interest income	-4.4	-1.1	-8	-7
Loss from continuing operations before income taxes	-68	-83.3	-164.8	-89.9
Income tax provision (benefit)	4	-184.7	-48.5	-181
(Loss) income from continuing operations, net of income taxes	-72	101.4	-116.3	91.1
Income (loss) from discontinued operations, net of income taxes	0.8	-14.3	1	-23.4
Net (loss) income	-71.2	87.1	-115.3	67.7
Less: Net income (loss) attributable to noncontrolling interests	2.1	-3.2	6.5	0.8
Net (loss) income attributable to common stockholders	($73.30)	$90.30	($121.80)	$66.90
(Loss) income from continuing operations:	'	'	'	'
Basic (loss) income per share	($0.28)	$0.39	($0.46)	$0.34
Diluted (loss) income per share	($0.28)	$0.39	($0.46)	$0.33
Net (loss) income attributable to common stockholders:	'	'	'	'
Basic (loss) income per share	($0.27)	$0.33	($0.46)	$0.25
Diluted (loss) income per share	($0.27)	$0.33	($0.46)	$0.25
Dividends declared per share	$0.09	$0.09	$0.17	$0.17

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Current assets	'	'
Cash and cash equivalents	$498.40	$444
Accounts receivable, net of allowance for doubtful accounts of $5.8 at June 30, 2014 and $7.4 at December 31, 2013	447.1	557.9
Inventories	548.4	506.7
Assets from coal trading activities, net	50.8	36.1
Deferred income taxes	67.2	66.4
Other current assets	265.9	381.6
Total current assets	1,877.80	1,992.70
Property, plant, equipment and mine development, net	10,700.50	11,082.50
Deferred income taxes	82.1	7.8
Investments and other assets	1,031.80	1,050.40
Total assets	13,692.20	14,133.40
Current liabilities	'	'
Current maturities of long-term debt	20.8	31.7
Deferred income taxes	7.5	0
Liabilities from coal trading activities, net	14.4	6.1
Accounts payable and accrued expenses	1,462	1,737.70
Total current liabilities	1,504.70	1,775.50
Long-term debt, less current maturities	5,973.20	5,970.70
Deferred income taxes	59.5	40.9
Asset retirement obligations	721.2	712.8
Accrued postretirement benefit costs	713	684
Other noncurrent liabilities	716.2	1,001.60
Total liabilities	9,687.80	10,185.50
Stockholders' equity	'	'
Additional paid-in capital	2,361.70	2,340
Treasury stock, at cost — 13.9 shares as of June 30, 2014 and 13.8 shares as of December 31, 2013	-466.9	-464.7
Retained earnings	2,281.90	2,449.80
Accumulated other comprehensive loss	-218.8	-419.2
Peabody Energy Corporation stockholders' equity	3,960.80	3,908.70
Noncontrolling interests	43.6	39.2
Total stockholders' equity	4,004.40	3,947.90
Total liabilities and stockholders' equity	13,692.20	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_Com

Consolidated Statements of Comprehensive Income (Unaudited) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Net (loss) income	($71.20)	$87.10	($115.30)	$67.70
Net change in unrealized holding gains (losses) on available-for-sale securities (net of respective tax provision (benefits) of $0.3, $3.7, ($0.8) and ($0.1))	'	'	'	'
Unrealized holding gains (losses) on available-for-sale securities	0.5	-7.6	-1.3	-13.8
Less: Reclassification for realized losses included in net (loss) income	0	13.6	0	13.5
Net change in unrealized gains (losses) on available-for-sale securities	0.5	6	-1.3	-0.3
Net unrealized gains (losses) on cash flow hedges (net of respective tax provision (benefits) of $37.2, ($217.1), $106.1 and ($228.0))	'	'	'	'
Increase (decrease) in fair value of cash flow hedges	67.9	-339	184.1	-270.3
Less: Reclassification for realized gains included in net (loss) income	-10.6	-38.3	-5	-115.4
Net unrealized gains (losses) on cash flow hedges	57.3	-377.3	179.1	-385.7
Postretirement plans and workers' compensation obligations (net of respective tax provision (benefit) of $4.0, $8.4, ($2.2) and $16.7	'	'	'	'
Prior service cost for the period	0	0	-17.4	0
Amortization of actuarial loss and prior service cost included in net (loss) income	6.8	14.2	13.6	28.4
Postretirement plans and workers' compensation obligations	6.8	14.2	-3.8	28.4
Foreign currency translation adjustment	9.9	-74.5	26.4	-73.4
Other comprehensive income (loss), net of income taxes	74.5	-431.6	200.4	-431
Comprehensive income (loss)	3.3	-344.5	85.1	-363.3
Less: Net income (loss) attributable to noncontrolling interests	2.1	-3.2	6.5	0.8
Comprehensive income (loss) attributable to common stockholders	$1.20	($341.30)	$78.60	($364.10)

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, except Share data, unless otherwise specified
Current assets	'	'
Allowance for doubtful accounts	$5.80	$7.40
Stockholders' equity	'	'
Treasury Stock, shares	13,900,000	13,800,000
Preferred Stock [Member]	'	'
Stockholders' equity	'	'
Preferred Stock, par value per share	$0.01	$0.01
Preferred Stock, shares authorized	10,000,000	10,000,000
Preferred Stock, shares issued	0	0
Preferred Stock, shares outstanding	0	0
Perpetual Preferred Stock [Member]	'	'
Stockholders' equity	'	'
Preferred Stock, shares authorized	800,000	800,000
Preferred Stock, shares issued	0	0
Preferred Stock, shares outstanding	0	0
Series Common Stock [Member]	'	'
Stockholders' equity	'	'
Common Stock, par value per share	$0.01	$0.01
Common Stock, shares authorized	40,000,000	40,000,000
Common Stock, shares issued	0	0
Common Stock, shares outstanding	0	0
Common Stock [Member]	'	'
Stockholders' equity	'	'
Common Stock, par value per share	$0.01	$0.01
Common Stock, shares authorized	800,000,000	800,000,000
Common Stock, shares issued	285,400,000	283,900,000
Common Stock, shares outstanding	271,500,000	270,100,000

Unaudited_Condensed_Consolidat

Unaudited Condensed Consolidated Statements of Comprehensive Income (Parenthetical) (Parentheticals) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Net change in unrealized holding gains (losses) on available-for-sale securities, tax benefits	$0.30	$3.70	($0.80)	($0.10)
Net unrealized gains (losses) on cash flow hedges, tax provision (benefit)	37.2	-217.1	106.1	-228
Amortization of actuarial loss and prior service cost for postretirement plans and workers' compensation obligations, tax provision (benefit)	$4	$8.40	($2.20)	$16.70

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $)	6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
Cash Flows From Operating Activities	'	'
Net (loss) income	($115.30)	$67.70
(Income) loss from discontinued operations, net of income taxes	-1	23.4
(Loss) income from continuing operations, net of income taxes	-116.3	91.1
Adjustments to reconcile (loss) income from continuing operations, net of income taxes to net cash provided by operating activities:	'	'
Depreciation, depletion and amortization	320.3	356.4
Noncash interest expense	11.7	11.1
Deferred income taxes	-113.9	-205.3
Share-based compensation	24	28.6
Asset impairment	0	21.5
Net gain on disposal or exchange of assets	-12	-45.8
Loss from equity affiliates	28.2	33
Gains on previously monetized foreign currency hedge positions	-74.8	0
Changes in current assets and liabilities:	'	'
Accounts receivable	99.8	-7.8
Change in receivable from accounts receivable securitization program	10	50
Inventories	-41.7	-33.4
Net assets from coal trading activities	-19.1	6
Other current assets	-1.7	13.6
Accounts payable and accrued expenses	13.2	-0.7
Asset retirement obligations	19.5	26.3
Accrued postretirement benefit costs	9.3	8.8
Accrued pension costs	9.9	25
Other, net	-9.3	-12.5
Net cash provided by continuing operations	157.1	365.9
Net cash used in discontinued operations	-81.8	-34.5
Net cash provided by operating activities	75.3	331.4
Cash Flows From Investing Activities	'	'
Additions to property, plant, equipment and mine development	-64.7	-166.5
Changes in accrued expenses related to capital expenditures	-17.5	-102.6
Proceeds from disposal of assets, net of notes receivable	139.2	123.9
Purchases of debt securities	-4.2	-9.7
Proceeds from sales and maturities of debt securities	5	17
Proceeds from the maturity of short-term investments	0	4.8
Contributions to joint ventures	-271.3	-323.8
Distributions from joint ventures	269	372.1
Advances to related parties	-12.3	-35.7
Repayments of loans from related parties	2.2	18.2
Other, net	-2	-3.6
Net cash provided by (used in) continuing operations	43.4	-105.9
Net cash provided by (used in) discontinued operations	5	-0.3
Net cash provided by (used in) investing activities	48.4	-106.2
Cash Flows From Financing Activities	'	'
Repayments of long-term debt	-10.4	-215.6
Payment of debt issuance costs	-10.1	0
Dividends paid	-46.1	-45.9
Other, net	-2.7	-4.6
Net cash used in financing activities	-69.3	-266.1
Net change in cash and cash equivalents	54.4	-40.9
Cash and cash equivalents at beginning of period	444	558.8
Cash and cash equivalents at end of period	$498.40	$517.90

Consolidated_Statements_of_Cha

Consolidated Statements of Changes in Stockholders' Equity (Unaudited) (USD $)	3 Months Ended	6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2014	Dec. 31, 2013
Net (loss) income	($71.20)	($115.30)	'
Net (loss) income attributable to common stockholders	-73.3	-121.8	'
Less: Net income (loss) attributable to noncontrolling interests	2.1	6.5	'
Net change in unrealized losses on available-for-sale securities (net of $0.8 tax benefit)	0.5	-1.3	'
Net unrealized gains on cash flow hedges	57.3	179.1	'
Postretirement plans and workers’ compensation obligations (net of $2.2 tax benefit)	6.8	-3.8	'
Foreign currency translation adjustment	9.9	26.4	'
Dividends paid	'	-46.1	'
Share-based compensation	'	24	'
Write-off of excess tax benefits related to share-based compensation	'	-5.3	'
Stock options exercised	'	0.5	'
Employee stock purchases	'	2.6	'
Repurchase of employee common stock relinquished for tax withholding	'	-2.2	'
Distributions to noncontrolling interests	'	-2.1	'
Ending Balance	4,004.40	4,004.40	3,947.90
Common Stock	'	'	'
Dividends paid	'	0	'
Share-based compensation	'	0.1	'
Ending Balance	2.9	2.9	2.8
Additional Paid-in Capital	'	'	'
Dividends paid	'	0	'
Share-based compensation	'	23.9	'
Write-off of excess tax benefits related to share-based compensation	'	-5.3	'
Stock options exercised	'	0.5	'
Employee stock purchases	'	2.6	'
Ending Balance	2,361.70	2,361.70	2,340
Treasury Stock	'	'	'
Dividends paid	'	0	'
Repurchase of employee common stock relinquished for tax withholding	'	-2.2	'
Ending Balance	-466.9	-466.9	-464.7
Retained Earnings	'	'	'
Net (loss) income attributable to common stockholders	'	-121.8	'
Dividends paid	'	-46.1	'
Ending Balance	2,281.90	2,281.90	2,449.80
Accumulated Other Comprehensive Loss	'	'	'
Net change in unrealized losses on available-for-sale securities (net of $0.8 tax benefit)	'	-1.3	'
Net unrealized gains on cash flow hedges	'	179.1	'
Postretirement plans and workers’ compensation obligations (net of $2.2 tax benefit)	'	-3.8	'
Foreign currency translation adjustment	'	26.4	'
Dividends paid	'	0	'
Ending Balance	-218.8	-218.8	-419.2
Noncontrolling Interests	'	'	'
Less: Net income (loss) attributable to noncontrolling interests	'	6.5	'
Dividends paid	'	0	'
Distributions to noncontrolling interests	'	-2.1	'
Ending Balance	$43.60	$43.60	$39.20

Consolidated_Statements_of_Cha1

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Net change in unrealized holding losses on available-for-sale securities, tax benefit	$0.30	$3.70	($0.80)	($0.10)
Net unrealized gains on cash flow hedges, tax provision	37.2	-217.1	106.1	-228
Postretirement plans and workers' compensation obligations, tax benefit	$4	$8.40	($2.20)	$16.70

Basis_of_Presentation

Basis of Presentation	6 Months Ended
	Jun. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Basis of Presentation	'
	Basis of Presentation
	The condensed consolidated financial statements include the accounts of Peabody Energy Corporation (the Company) and its affiliates. Interests in subsidiaries controlled by the Company are consolidated and any outside shareholder interests are 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 unaudited condensed consolidated financial statements.  All intercompany transactions, profits and balances have been eliminated in consolidation. Certain prior year amounts have been reclassified to conform with the 2014 presentation.
	The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (U.S. GAAP) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements and should be read in conjunction with the consolidated financial statements and notes thereto included in the Company's Annual Report on Form 10-K for the year ended December 31, 2013. In the opinion of management, these financial statements reflect all normal, recurring adjustments necessary for a fair presentation. Balance sheet information presented herein as of December 31, 2013 has been derived from the Company’s audited consolidated balance sheet at that date. The Company's results of operations for the three and six months ended June 30, 2014 are not necessarily indicative of the results that may be expected for future quarters or for the year ending December 31, 2014.
	The Company classifies items within discontinued operations in the unaudited condensed 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.

Newly_Adopted_Accounting_Stand

Newly Adopted Accounting Standards and Accounting Standards Not Yet Implemented	6 Months Ended
	Jun. 30, 2014
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]	'
Newly Adopted Accounting Standards and Accounting Standards Not Yet Implemented	'
	Newly Adopted Accounting Standards and Accounting Standards Not Yet Implemented
	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, which the Company applied prospectively beginning January 1, 2014, had no material effect on the Company's results of operations, financial condition, cash flows or 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), with early adoption permitted for disposals or new classifications of assets as held for sale that have not been reported in previously issued financial statements. The impact to the Company will be dependent on any disposal activity that occurs subsequent to the adoption date.
	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 has just begun 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.

Asset_Realization_Notes

Asset Realization (Notes)	6 Months Ended
	Jun. 30, 2014
Asset Realization	'
Asset Realization	'
	Asset Realization
	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. As a result of various unfavorable conditions, including but not limited to sustained trends of weakness in U.S. and international seaborne coal market pricing and certain asset-specific factors, the Company recognized aggregate impairment charges of $528.3 million and $910.9 million during the years ended December 31, 2013 and 2012, respectively. For additional information surrounding those charges, refer to Note 2. "Asset Impairment and Mine Closures Costs" to the consolidated financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2013.
	The Company generally does not view short-term declines subsequent to previous impairment assessments in thermal and metallurgical coal prices in the markets in which it sells its products as an indicator of impairment, such as the decline in benchmark pricing for seaborne metallurgical and thermal coal that occurred during the six months ended June 30, 2014. However, the Company generally does view a sustained trend of adverse changes in coal market pricing (for example, over periods exceeding one year) as an indicator of potential impairment and, because of the volatile and cyclical nature of U.S. and international seaborne coal markets, it is reasonably possible that such prices may not improve or decrease further 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 mines in Australia with comparatively shorter remaining lives and mining-related investments, which assets had an aggregate carrying value of $227.4 million as of June 30, 2014. The Company conducted a review of those assets for recoverability as of June 30, 2014 and determined that no impairment charge was necessary as of that date.

Discontinued_Operations

Discontinued Operations	6 Months Ended
	Jun. 30, 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 operations.
	Summarized Results of Discontinued Operations
	Results from discontinued operations were as follows during the three and six months ended June 30, 2014 and 2013:
		Three Months Ended June 30,						Six Months Ended June 30,
		2014			2013			2014			2013
		(Dollars in millions)
	Income (loss) from discontinued operations before income taxes	$	1.2		$	(16.1	)	$	1.1		$	(32.7	)
	Income tax provision (benefit)	0.4			(1.8		)	0.1			(9.3		)
	Income (loss) from discontinued operations, net of income taxes	$	0.8		$	(14.3	)	$	1		$	(23.4	)
	There were no significant revenues from discontinued operations during the three and six months ended June 30, 2014. Total revenues associated with discontinued operations amounted to $35.6 million and $67.7 million during the three and six months ended June 30, 2013, respectively.
	Assets and Liabilities of Discontinued Operations
	The carrying amounts of assets and liabilities classified as discontinued operations included in the Company's condensed consolidated balance sheets were as follows:
		June 30, 2014			December 31, 2013
		(Dollars in millions)
	Assets:
	Other current assets	$	2.4		$	38.6
	Investments and other assets	20.8			47.4
	Total assets classified as discontinued operations	$	23.2		$	86
	Liabilities:
	Accounts payable and accrued expenses	$	42.3		$	127.8
	Other noncurrent liabilities	86.7			90.2
	Total liabilities classified as discontinued operations	$	129		$	218
	Settlement Agreement with Patriot and the UMWA. Pursuant to the definitive settlement agreement reached in 2013 with Patriot Coal Corporation and certain of its wholly owned subsidiaries (Patriot) and the United Mine Workers of America (UMWA) on behalf of itself, its represented Patriot employees and its represented Patriot retirees, the Company remitted a payment of $70 million to Patriot in January 2014. Refer to Note 18. "Commitments and Contingencies" for additional details surrounding that settlement agreement.
	Wilkie Creek Mine. In December 2013, the Company ceased production and commenced the reclamation of the Wilkie Creek Mine in Queensland, Australia and correspondingly accrued for potential port and rail take-or-pay contractual liabilities and certain other exit costs at that time. The following table summarizes the changes in those liabilities for the six months ended June 30, 2014:
		Accrued Take-or-Pay Liabilities			Other Exit Costs			Total
		(Dollars in millions)
	Liability balance at December 31, 2013	$	33.9		$	2.7		$	36.6
	Change in estimate	—			(0.2		)	(0.2		)
	Cash payments	(6.3		)	(2.4		)	(8.7		)
	Foreign currency remeasurement expense	1.6			—			1.6
	Liability balance at June 30, 2014	$	29.2		$	0.1		$	29.3
	In addition to the closure-related liabilities detailed above, the Company's unaudited condensed consolidated balance sheet at June 30, 2014 included $48.0 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.

Investments

Investments	6 Months Ended
	Jun. 30, 2014
Investments, Debt and Equity Securities [Abstract]	'
Investments	'
	Investments
	Investments in available-for-sale securities at June 30, 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	$	8.9	$	—	$	—		$	8.9
	Noncurrent:
	Marketable equity securities	10.9		—		(0.9		)	10
	Federal government securities	29.3		—		—			29.3
	U.S. corporate bonds	15.4		0.1		—			15.5
	Total	$	64.5	$	0.1	$	(0.9	)	$	63.7
	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 short-term investments are defined as those investments with remaining maturities, at the time of purchase, of greater than three months and up to one year and are included in "Other current assets" in the condensed consolidated balance sheets. Long-term investments are defined as those investments with remaining maturities of greater than one year and are included in "Investments and other assets" in the condensed consolidated balance sheets. The Company’s investments in marketable equity securities consist of an investment in Winsway Coking Coal Holdings Limited (Winsway). Those equity securities are included in "Investments and other assets" in the condensed consolidated balance sheets.
	Contractual maturities for available-for-sale investments in debt securities at June 30, 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 debt securities	Cost		Fair Value
		(Dollars in millions)
	Due in one year or less	$	8.9	$	8.9
	Due in one to five years	44.7		44.8
	Total	$	53.6	$	53.7
	Proceeds from sales and maturities of debt securities shown in the tables above amounted to $4.6 million and $4.1 million for the three months ended June 30, 2014 and 2013, respectively, and $5.0 million and $17.0 million for the six months ended June 30, 2014 and 2013, respectively. The Company realized net gains of less than $0.1 million during the three and six months ended June 30, 2014 and 2013 associated with those sales and maturities using the specific identification method. Purchases of debt securities shown in the tables above amounted to $2.2 million and $5.1 million for the three months ended June 30, 2014, and 2013, respectively, and $4.2 million and $9.7 million for the six months ended June 30, 2014 and 2013, respectively.
	The Company also recognized proceeds of $4.8 million from the maturity of time deposits denominated in Chinese Renminbi during the three and six months ended June 30, 2013. The Company did not have any held-to-maturity investments as of June 30, 2014 or December 31, 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. After evaluating the length of time market value has been less than cost and the financial conditions and near-term prospects of Winsway, the Company deemed the unrealized loss incurred during the three and six months ended June 30, 2014 associated with its investment in Winsway equity securities to be temporary and the change during the period to be generally consistent with the trend of equity securities across the coal mining industry. The Company has the ability to hold the securities until recovery and has no current intention to divest the securities. Accordingly, the Company did not recognize other-than-temporary losses on its investments during the three and six months ended June 30, 2014. The Company recognized an other-than-temporary asset impairment charge of $21.5 million during the three and six months ended June 30, 2013, which was triggered by a second quarter 2013 downgrade of Winsway's credit rating and the duration and severity of the market losses incurred at that time, thereby resetting the cost basis of the Company's investment.

Inventories

Inventories	6 Months Ended
	Jun. 30, 2014
Inventory Disclosure [Abstract]	'
Inventories	'
	Inventories
	Inventories as of June 30, 2014 and December 31, 2013 consisted of the following:
		June 30, 2014		December 31, 2013
		(Dollars in millions)
	Materials and supplies	$	166.3	$	166.8
	Raw coal	141.5		122.6
	Saleable coal	240.6		217.3
	Total	$	548.4	$	506.7
	Materials and supplies inventories presented above have been shown net of reserves of $4.7 million and $7.4 million as of June 30, 2014 and December 31, 2013, respectively.

Derivatives_and_Fair_Value_Mea

Derivatives and Fair Value Measurements	6 Months Ended
	Jun. 30, 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), 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 and Explosives 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 and explosives purchases.
	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 results 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 June 30, 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 June 30, 2014:
		Notional Amount by Year of Maturity
		Total				2014				2015				2016				2017
	Foreign Currency
	A$:US$ hedge contracts (A$ millions)	$	4,082.10			$	935			$	1,645.10			$	997			$	505
	Commodity Contracts
	Diesel fuel hedge contracts (million gallons)	208.5				52.2				85.5				53.3				17.5
	U.S. explosives hedge contracts (million MMBtu)	0.3				0.3				—				—				—
		Instrument Classification by
		Cash Flow				Fair Value				Economic					Fair Value Net Asset (Liability)
		Hedge				Hedge				Hedge
															(Dollars in millions)
	Foreign Currency
	A$:US$ hedge contracts (A$ millions)	$	4,082.10			$	—			$	—				$	(109.6	)
	Commodity Contracts
	Diesel fuel hedge contracts (million gallons)	208.5				—				—					16
	U.S. explosives hedge contracts (million MMBtu)	0.3				—				—					(0.2		)
	Based on the net fair value of the Company’s non-coal trading commodity contract hedge positions held in “Accumulated other comprehensive loss” at June 30, 2014, the Company expects to reclassify an unrealized net gain associated with the Company's diesel fuel hedge programs of approximately $9 million and an unrealized net loss associated with the Company's explosives hedge programs of approximately $0.2 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 and realized gains related to foreign currency cash flow hedge contracts monetized in the fourth quarter of 2012 held in "Accumulated other comprehensive loss" at June 30, 2014, the net gain expected to be reclassified from comprehensive income to earnings over the next twelve months associated with that hedge program is approximately $15 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 the realized underlying transactions.
	Hedge Ineffectiveness. The Company assesses, both at inception and at least quarterly thereafter, whether the derivatives used in hedging activities are highly effective at offsetting the changes in the anticipated cash flows of the hedged item. The effective portion of the change in the fair value 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.
	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 future explosives purchases are based on natural gas, which is the primary price component of explosives. However, a small measure of ineffectiveness exists as the contractual purchase price includes manufacturing fees that are subject to periodic adjustments. In addition, other fees, such as storage and transportation surcharges, can result in ineffectiveness, but have historically changed infrequently and comprise a small portion of the total explosives cost.
	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 three and six months ended June 30, 2014 and 2013:
					Three Months Ended June 30, 2014
	Financial Instrument		Income Statement		Gain recognized in income on non-designated derivatives				Gain recognized in other comprehensive income on derivatives				(Loss) gain reclassified from other comprehensive income into income				Gain reclassified from other comprehensive income into income
			Classification Gains (Losses) -						(effective portion) (1)				(effective portion) (1)				(ineffective portion)
			Realized
					(Dollars in millions)
	Commodity swaps and options		Operating costs and expenses		$	—			$	17.7			$	(0.1	)		$	1
	Foreign currency forward contracts		Operating costs and expenses		—				134.7				6.3				—
	Total				$	—			$	152.4			$	6.2			$	1
					Three Months Ended June 30, 2013
	Financial Instrument		Income Statement		Gain recognized in income on non-designated derivatives				Loss recognized in other comprehensive income on derivatives				Gain reclassified from other comprehensive income into income				Gain reclassified from other comprehensive income into income
			Classification Gains (Losses) -						(effective portion)				(effective portion)				(ineffective portion)
			Realized
					(Dollars in millions)
	Commodity swaps and options		Operating costs and expenses		$	—			$	(25.0	)		$	0.5			$	0.1
	Foreign currency forward contracts		Operating costs and expenses		—				(492.6		)		62.1				—
	Total				$	—			$	(517.6	)		$	62.6			$	0.1
	(1)	Includes the reclassification from "Accumulated other comprehensive loss" into earnings of $33.9 million of previously unrecognized gains on foreign currency cash flow hedge contracts monetized in the fourth quarter of 2012.
					Six Months Ended June 30, 2014
	Financial Instrument		Income Statement		Gain recognized in income on non-designated derivatives				Gain recognized in other comprehensive income on derivatives				Loss reclassified from other comprehensive income into income				Gain reclassified from other comprehensive income into income
			Classification Gains (Losses) -						(effective portion) (1)				(effective portion) (1)				(ineffective portion)
			Realized
					(Dollars in millions)
	Commodity swaps and options		Operating costs and expenses		$	—			$	9.2			$	(2.3	)		$	0.8
	Foreign currency forward contracts		Operating costs and expenses		—				351.2				(12.5		)		—
	Total				$	—			$	360.4			$	(14.8	)		$	0.8
					Six Months Ended June 30, 2013
	Financial Instrument		Income Statement		Gain recognized in income on non-designated derivatives				Loss recognized in other comprehensive income on derivatives				Gain reclassified from other comprehensive income into income				Gain reclassified from other comprehensive income into income
			Classification Gains (Losses) -						(effective portion)				(effective portion)				(ineffective portion)
			Realized
					(Dollars in millions)
	Commodity swaps and options		Operating costs and expenses		$	—			$	(19.1	)		$	7.2			$	0.3
	Foreign currency forward contracts		Operating costs and expenses		—				(453.9		)		147.2				—
	Total				$	—			$	(473.0	)		$	154.4			$	0.3
	(1)	Includes the reclassification from "Accumulated other comprehensive loss" into earnings of $74.8 million of previously unrecognized gains on foreign currency cash flow hedge contracts monetized in the fourth quarter of 2012.
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 unaudited condensed consolidated statements of cash flows during the period of settlement for those instruments.
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, diesel fuel and explosives 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 June 30, 2014 and December 31, 2013 are presented in the tables that follow.
		Fair Value of Assets as of June 30, 2014
Financial Instrument		Gross Amounts Recognized				Gross Amounts Offset in the Condensed Consolidated Balance Sheet				Net Amounts Presented in the Condensed Consolidated Balance Sheet				Derivatives Not Offset in the Condensed Consolidated Balance Sheet (1)				Net Amount
		(Dollars in millions)
Current Assets:
Commodity swap contracts		$	9.7			$	(0.7	)		$	9			n.a.				n.a.
Foreign currency forward contracts		11.6				(10.2		)		1.4				n.a.				n.a.
Total		$	21.3			$	(10.9	)		$	10.4			$	(7.5	)		$	2.9
Noncurrent Assets:
Commodity swap contracts		$	8			$	(0.5	)		$	7.5			n.a.				n.a.
Foreign currency forward contracts		17.4				(16.6		)		0.8				n.a.				n.a.
Total		$	25.4			$	(17.1	)		$	8.3			$	(5.4	)		$	2.9
(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 June 30, 2014
Financial Instrument		Gross Amounts Recognized				Gross Amounts Offset in the Condensed Consolidated Balance Sheet				Net Amounts Presented in the Condensed Consolidated Balance Sheet				Derivatives Not Offset in the Condensed Consolidated Balance Sheet (1)				Net Amount
		(Dollars in millions)
Current Liabilities:
Commodity swap contracts		$	1.4			$	(0.8	)		$	0.6			n.a.				n.a.
Foreign currency forward contracts		76.4				(12.9		)		63.5				n.a.				n.a.
Total		$	77.8			$	(13.7	)		$	64.1			$	(7.4	)		$	56.7
Noncurrent Liabilities:
Commodity swap contracts		$	0.5			$	(0.4	)		$	0.1			n.a.				n.a.
Foreign currency forward contracts		62.2				(13.9		)		48.3				n.a.				n.a.
Total		$	62.7			$	(14.3	)		$	48.4			$	(5.5	)		$	42.9
(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 Assets as of December 31, 2013
Financial Instrument		Gross Amounts Recognized				Gross Amounts Offset in the Condensed Consolidated Balance Sheet				Net Amounts Presented in the Condensed Consolidated Balance Sheet				Derivatives Not Offset in the Condensed Consolidated Balance Sheet (1)				Net Amount
		(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
Financial Instrument		Gross Amounts Recognized				Gross Amounts Offset in the Condensed Consolidated Balance Sheet				Net Amounts Presented in the Condensed Consolidated Balance Sheet				Derivatives Not Offset in the Condensed Consolidated Balance Sheet (1)				Net Amount
		(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 8. "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:
	June 30, 2014
	Level 1				Level 2				Level 3				Total
	(Dollars in millions)
Investments in debt and equity securities	$	27.2			$	36.5			$	—			$	63.7
Commodity swaps and options	—				15.8				—				15.8
Foreign currency cash flow hedge contracts	—				(109.6		)		—				(109.6		)
Total net financial assets (liabilities)	$	27.2			$	(57.3	)		$	—			$	(30.1	)
	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 swaps and options	—				5.1				—				5.1
Foreign currency cash flow hedge 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 three and six months ended June 30, 2014 or 2013 for its non-coal trading positions. The Company’s policy is to value 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 June 30, 2014 and December 31, 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:
	June 30, 2014								December 31, 2013
	Carrying				Estimated				Carrying				Estimated
	Amount				Fair Value				Amount				Fair Value
	(Dollars in millions)
Long-term debt	$	5,994.00			$	6,055.20			$	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 continuous 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	6 Months Ended
	Jun. 30, 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 unaudited condensed 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 three and six months ended June 30, 2014 and 2013 were as follows:
			Three Months Ended								Six Months Ended
			June 30,								June 30,
	Trading Revenues by Type of Instrument		2014				2013				2014				2013
			(Dollars in millions)
	Commodity futures, swaps and options		$	22.7			$	34.9			$	58.3			$	85.9
	Physical commodity purchase/sale contracts		(12.4		)		(38.3		)		(27.0		)		(63.4		)
	Total trading revenues		$	10.3			$	(3.4	)		$	31.3			$	22.5
	Risk Management
	Hedge Ineffectiveness. The Company assesses, both at inception and at least quarterly thereafter, whether the derivatives used in cash flow hedging activities are highly effective at offsetting the changes in the anticipated cash flows of the hedged item. The effective portion of the change in the fair value is recorded in “Accumulated other comprehensive loss” until the hedged transaction impacts reported earnings, at which time those gains and losses are reclassified to earnings. To the extent that periodic changes in the fair value of a derivative exceeds the changes in the expected future cash flows of the hedged item to which it has been designated, the ineffective portion is recorded in earnings in the period of the change. If the hedge ceases to qualify for hedge accounting, the Company prospectively recognizes the changes in fair value of the instrument in earnings in the period of the change.
	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 $47.9 million and $62.9 million as of June 30, 2014 and December 31, 2013, respectively. Based on the net fair value of the Company’s coal trading positions held in “Accumulated other comprehensive loss” at June 30, 2014, unrealized gains to be reclassified from comprehensive income to earnings over the next 12 months are expected to be approximately $35 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 unaudited condensed consolidated statements of operations.
	Forecasted Transactions No Longer Probable. During the six months ended June 30, 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 over-the-counter (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 condensed 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 June 30, 2014 and December 31, 2013 is set forth below:
	Affected line item in the condensed consolidated balance sheets		Gross Amounts of Recognized Assets (Liabilities)				Gross Amounts Offset in the Condensed Consolidated Balance Sheets				Variation margin (held) posted (1)				Net Amounts of Assets (Liabilities) Presented in the Condensed Consolidated Balance Sheets
			(Dollars in millions)
			Fair Value as of June 30, 2014
	Assets from coal trading activities, net		$	430.2			$	(345.4	)		$	(34.0	)		$	50.8
	Liabilities from coal trading activities, net		(359.8		)		345.4				—				(14.4		)
	Total, Net		$	70.4			$	—			$	(34.0	)		$	36.4
			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)	Approximately $15 million and $42 million of the net variation margin held at June 30, 2014 and December 31, 2013, respectively, related to cash flow hedges.
	See Note 7. "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 June 30, 2014 and December 31, 2013:
		June 30, 2014
		Level 1				Level 2				Level 3				Total
		(Dollars in millions)
	Commodity futures, swaps and options	$	—			$	37.7			$	—			$	37.7
	Physical commodity purchase/sale contracts	—				(3.9		)		2.6				(1.3		)
	Total net financial assets	$	—			$	33.8			$	2.6			$	36.4
		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 June 30, 2014:
			Range						Weighted
	Input		Low			High			Average
	Quality adjustments		1	%		8	%		7	%
	Location differentials		17	%		64	%		37	%
	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:
			Three Months Ended								Six Months Ended
			June 30,								June 30,
			2014				2013				2014				2013
			(Dollars in millions)
	Beginning of period		$	2.2			$	1.4			$	2.1			$	5.2
	Total net gains (losses) realized/unrealized:
Included in earnings		1.5				(0.3		)		3.3				(4.4		)
Settlements		(1.1		)		0.2				(2.8		)		0.5
End of period		$	2.6			$	1.3			$	2.6			$	1.3
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:
		Three Months Ended								Six Months Ended
		June 30,								June 30,
		2014				2013				2014				2013
		(Dollars in millions)
Changes in net unrealized gains (losses) (1)		$	1.2			$	(2.8	)		$	0.3			$	(2.6	)
(1)	Within the unaudited condensed consolidated statements of operations and unaudited condensed 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 in its coal trading positions between Level 1 and Level 2 during the three and six months ended June 30, 2014 or 2013. There were no transfers in or out of Level 3 during the three and six months ended June 30, 2014 or 2013. The Company’s policy is to value transfers between levels using the beginning of period valuation.
As of June 30, 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
2014		68	%
2015		19	%
2016		10	%
2017		2	%
2018		1	%
		100	%
Credit and Nonperformance Risk. 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 and steel producers. 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, 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.
At June 30, 2014, 94% of the Company’s credit exposure related to coal trading activities was with investment grade counterparties, while 2% was with non-investment grade counterparties and 4% 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 June 30, 2014 and December 31, 2013, would have amounted to collateral postings to counterparties of approximately $15 million and $7 million, respectively. As of June 30, 2014 and December 31, 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. In recent months, two 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 June 30, 2014 and December 31, 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 June 30, 2014 or December 31, 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 June 30, 2014 and December 31, 2013, the Company held net variation margin of $34.0 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 June 30, 2014 and December 31, 2013, the Company had posted initial margin of $17.1 million and $19.6 million, respectively, which is reflected in “Other current assets” in the condensed consolidated balance sheets. The Company also had posted $2.0 million and $1.0 million of margin in excess of the exchange-required variation and initial margin discussed above as of June 30, 2014 and December 31, 2013, respectively.

Financing_Receivables

Financing Receivables	6 Months Ended
	Jun. 30, 2014
Financing Receivables [Abstract]	'
Financing Receivables [Text Block]	'
	Financing Receivables
	The Company's total financing receivables as of June 30, 2014 and December 31, 2013 consisted of the following:
	Balance Sheet Classification	June 30, 2014		December 31, 2013
		(Dollars in millions)
	Accounts receivable, net	$	0.1	$	0.1
	Investments and other assets	378.2		351.7
	Total financing receivables	$	378.3	$	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 June 30, 2014.
	Codrilla Mine Project. In 2011, a wholly owned subsidiary of PEA-PCI, then Macarthur Coal Limited, completed the sale of its 85% interest in the Codrilla Mine Project to participants of the Coppabella Moorvale Joint Venture (CMJV) where PEA-PCI sold down its interest in the Codrilla project to the CMJV (Codrilla sell down) so that, following the completion of the sale, ownership of the Codrilla Mine Project reflected the existing ownership of the Coppabella and Moorvale mines with PEA-PCI retaining a 73.3% ownership. Prior to the acquisition of PEA-PCI by the Company, consideration of $15.0 million Australian dollars was received by PEA-PCI upon completion of the Codrilla sell down, representing 20% of the agreed price. Two installments, for which the Company held non-interest-bearing receivables, are due upon the completion of certain milestones. The first installment, with 40% due on the granting of the related mining lease, was received in 2012. The final 40% 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 unaudited condensed consolidated statements of operations for the three and six months ended June 30, 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 condensed consolidated balance sheets, which balance totaled $30.9 million and $28.5 million at June 30, 2014 and December 31, 2013, respectively.
	Middlemount Mine. The Company periodically makes loans to the Middlemount Mine joint venture (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 condensed consolidated balance sheets and the unaudited condensed 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 $1.2 million and $2.0 million during the three months ended June 30, 2014 and 2013, respectively, and $2.6 million and $3.4 million during the six months ended June 30, 2014 and 2013, respectively. Interest income under a full accrual basis would have resulted in additional interest income of $1.4 million and $1.7 million during the three months ended June 30, 2014 and 2013, respectively, and $3.1 million and $3.3 million during the six months ended June 30, 2014 and 2013, respectively. The carrying value of these loans of $347.3 million and $323.2 million was reflected in "Investments and other assets" in the condensed consolidated balance sheets as of June 30, 2014 and December 31, 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)	6 Months Ended
	Jun. 30, 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 June 30, 2014 and December 31, 2013 consisted of the following:
		30-Jun-14			December 31, 2013
		(Dollars in millions)
	Land and coal interests	$	10,957.60		$	11,024.10
	Buildings and improvements	1,553.20			1,525.40
	Machinery and equipment	2,663.30			2,777.50
	Less: Accumulated depreciation, depletion and amortization	(4,473.6		)	(4,244.5		)
	Total, net	$	10,700.50		$	11,082.50

Income_Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2014
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	Income Taxes
	The Company's tax expense of $4.0 million and tax benefit of $184.7 million for the three months ended June 30, 2014 and 2013, respectively, include remeasurement benefit of $1.3 million and $37.1 million related to foreign tax accounts, respectively. The Company's tax benefit of $48.5 million and $181.0 million for the six months ended June 30, 2014 and 2013, respectively, include remeasurement benefit of $2.7 million and $35.5 million related to foreign tax accounts, respectively. The effective tax rate before remeasurement is based on the Company's estimated full year effective tax rate made up of the expected statutory tax expense more than offset by reductions from percentage depletion, foreign rate differential and Australian minerals resource rent tax. For the three and six months ended June 30, 2014, the Company recorded a valuation allowance on certain Australian deferred tax assets not considered more likely than not to be realized amounting to $75.7 million and $124.7 million, respectively. For the three months ended June 30, 2013, the Company released a portion of its valuation allowance on U.S. capital loss carryforwards amounting to $25.5 million due to a change in expected realization upon sale of non-strategic U.S. coal reserves and surface lands.
	During the three and six months ended June 30, 2014, the Company decreased its net unrecognized tax benefits, interest and penalties by $19.5 million and $48.4 million, respectively, due to amended returns filed and settlement of intercompany financing transactions on the 2004 through 2012 Australian Taxation Office (ATO) audit. During the six months ended June 30, 2014, the U.S. Internal Revenue Service (IRS) added the 2011 through 2013 tax years to the 2009 through 2010 audit due to amended returns filed for capital and net operating loss carrybacks. The Company believes during the next twelve months it is reasonably possible for a $25.0 million decrease in its net unrecognized tax benefits due to potential audit settlements.

Longterm_Debt_Notes

Long-term Debt (Notes)	6 Months Ended
	Jun. 30, 2014
Debt Disclosure [Abstract]	'
Debt Disclosure [Text Block]	'
	Long-term Debt
	The Company’s total indebtedness as of June 30, 2014 and December 31, 2013 consisted of the following:
		June 30, 2014		December 31, 2013
		(Dollars in millions)
	2013 Term Loan Facility due September 2020	$	1,180.30	$	1,185.40
	7.375% Senior Notes due November 2016	650		650
	6.00% Senior Notes due November 2018	1,518.80		1,518.80
	6.50% Senior Notes due September 2020	650		650
	6.25% Senior Notes due November 2021	1,339.60		1,339.60
	7.875% Senior Notes due November 2026	247.6		247.5
	Convertible Junior Subordinated Debentures due December 2066	381		379.7
	Capital lease obligations	26.4		30.5
	Other	0.3		0.9
	Total long-term debt	$	5,994.00	$	6,002.40
	The carrying amounts of the Convertible Junior Subordinated Debentures due December 2066 (the Debentures), the 2013 Term Loan Facility due September 2020 and the 7.875% Senior Notes due December 2026 have been presented above net of the respective unamortized original issue discounts.
	Debentures Consent Solicitation
	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 unaudited condensed consolidated statements of operations for the three and six months ended June 30, 2014.
	Voluntary Debt Prepayments
	During the six months ended June 30, 2013, the Company voluntarily prepaid $167.0 million in aggregate principal amount of its previous term loan facility with existing cash on hand. Additionally, the Company repurchased $32.4 million of certain Australian private placement bonds with existing cash on hand during the six months ended June 30, 2013. In connection with the foregoing, the Company recognized losses on debt extinguishment of $4.5 million and $5.4 million during the three and six months ended June 30, 2013, respectively, which were classified in "Interest expense" in the unaudited condensed consolidated statements of operations for those periods. During the three and six months ended June 30, 2014, the Company made no debt payments in excess of its scheduled maturities.

Pension_and_Postretirement_Ben

Pension and Postretirement Benefit Costs	6 Months Ended
	Jun. 30, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]	'
Compensation and Employee Benefit Plans [Text Block]	'
	Pension and Postretirement Benefit Costs
	Net periodic pension cost included the following components:
		Three Months Ended June 30,						Six Months Ended June 30,
		2014			2013			2014			2013
		(Dollars in millions)
	Service cost for benefits earned	$	0.5		$	0.5		$	1		$	1.1
	Interest cost on projected benefit obligation	11.3			10.5			22.7			21.1
	Expected return on plan assets	(13.5		)	(14.8		)	(27.1		)	(29.7		)
	Amortization of prior service cost and net actuarial loss	7.8			16.7			15.7			33.3
	Net periodic pension cost	$	6.1		$	12.9		$	12.3		$	25.8
	Annual contributions to the 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%). The Company currently expects its qualified plans to be at or above the Pension Protection Act thresholds and will therefore avoid benefit restrictions and at-risk penalties for 2014. During the three and six months ended June 30, 2014, the Company contributed $1.6 million and $2.4 million, respectively, to its pension plans. The Company expects to contribute approximately $13 million to its pension plans in 2014 to meet minimum funding requirements for its qualified plans and benefit payments for its non-qualified plans.
	Net periodic postretirement benefit cost included the following components:
		Three Months Ended June 30,						Six Months Ended June 30,
		2014			2013			2014			2013
		(Dollars in millions)
	Service cost for benefits earned	$	3		$	3.9		$	6.1		$	7.8
	Interest cost on accumulated postretirement benefit obligation	9.1			10.4			18.2			20.9
	Amortization of prior service cost and net actuarial loss, and special termination benefits	4			7.1			7.9			12.7
	Net periodic postretirement benefit cost	$	16.1		$	21.4		$	32.2		$	41.4
	During the six months ended June 30, 2014, the Company increased its accumulated postretirement benefit obligation (included in “Accrued postretirement benefit costs”) by $27.6 million, with an offsetting pre-tax prior service cost adjustment recorded directly to “Accumulated other comprehensive loss.” The adjustment was a result of a plan change effective April 1, 2014 for certain plan participants' benefits no longer funded through a Medicare Advantage Program. The plan change will not affect participant benefits, although it is expected to increase future employer contributions including an additional $2.0 million of Company contributions for the year ending December 31, 2014.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Loss Accumulated Other Comprehensive Loss	6 Months Ended
	Jun. 30, 2014
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]	'
Accumulated Other Comprehensive Income (Loss)	'
	Accumulated Other Comprehensive Loss
	The following table below sets forth the after-tax components of accumulated other comprehensive loss and changes thereto recorded during the six months ended June 30, 2014:
		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, 2013	$	(70.5	)		$	(205.8	)		$	12		$	(155.7	)	$	0.8		$	(419.2	)
	Net change in fair value	—				—				—			184.1			(1.3		)	182.8
	Reclassification from other comprehensive income to earnings	—				12.7				0.9			(5.0		)	—			8.6
	Current period change	26.4				—				(17.4		)	—			—			9
	June 30, 2014	$	(44.1	)		$	(193.1	)		$	(4.5	)	$	23.4		$	(0.5	)	$	(218.8	)
	The following tables provide additional information regarding items reclassified out of "Accumulated other comprehensive loss" into earnings during the three and six months ended June 30, 2014 and 2013:
			Amount reclassified from accumulated other comprehensive loss (1)
	Details about accumulated other comprehensive income (loss) components		Three Months Ended June 30, 2014				Three Months Ended June 30, 2013				Affected line item in the condensed consolidated statement of operations
			(Dollars in millions)
	Net actuarial loss associated with postretirement plans and workers compensation obligations:
	Postretirement health care and life insurance benefits		$	(3.6	)		$	(6.0	)		Operating costs and expenses
	Defined benefit pension plans		(6.2		)		(13.6		)		Operating costs and expenses
	Defined benefit pension plans		(1.3		)		(2.8		)		Selling and administrative expenses
	Insignificant items		1				(0.3		)
			(10.1		)		(22.7		)		Total before income taxes
			3.8				8.4				Income tax benefit
			$	(6.3	)		$	(14.3	)		Total after income taxes
	Prior service cost associated with postretirement plans:
	Postretirement health care and life insurance benefits		$	(0.4	)		$	0.4			Operating costs and expenses
	Defined benefit pension plans		(0.3		)		(0.3		)		Operating costs and expenses
			(0.7		)		0.1				Total before income taxes
			0.2				—				Income tax benefit
			$	(0.5	)		$	0.1			Total after income taxes
	Cash flow hedges:
	Foreign currency cash flow hedge contracts		$	6.3			$	62.1			Operating costs and expenses
	Fuel and explosives commodity swaps		0.9				0.6				Operating costs and expenses
	Coal trading commodity futures, swaps and options		3				0.4				Other revenues
	Insignificant items		—				(0.2		)
			10.2				62.9				Total before income taxes
			0.4				(24.6		)		Income tax benefit (provision)
			$	10.6			$	38.3			Total after income taxes
	Available-for-sale securities:
	Equity securities		$	—			$	(21.5	)		Asset impairment
			—				7.9				Income tax benefit
			$	—			$	(13.6	)		Total after income taxes
	(1)	Presented as gains (losses) in the unaudited condensed consolidated statements of operations.
			Amount reclassified from accumulated other comprehensive loss (1)
	Details about accumulated other comprehensive income (loss) components		Six Months Ended June 30, 2014				Six Months Ended June 30, 2013				Affected line item in the condensed consolidated statement of operations
			(Dollars in millions)
	Net actuarial loss associated with postretirement plans and workers compensation obligations:
	Postretirement health care and life insurance benefits		$	(7.2	)		$	(12.0	)		Operating costs and expenses
	Defined benefit pension plans		(12.4		)		(27.2		)		Operating costs and expenses
	Defined benefit pension plans		(2.7		)		(5.6		)		Selling and administrative expenses
	Insignificant items		2				(0.6		)
			(20.3		)		(45.4		)		Total before income taxes
			7.6				16.8				Income tax benefit
			$	(12.7	)		$	(28.6	)		Total after income taxes
	Prior service cost associated with postretirement plans:
	Postretirement health care and life insurance benefits		$	(0.7	)		$	0.8			Operating costs and expenses
	Defined benefit pension plans		(0.6		)		(0.5		)		Operating costs and expenses
			(1.3		)		0.3				Total before income taxes
			0.4				(0.1		)		Income tax benefit (provision)
		$	(0.9	)		$	0.2			Total after income taxes
Cash flow hedges:
Foreign currency cash flow hedge contracts		$	(12.5	)		$	147.2			Operating costs and expenses
Fuel and explosives commodity swaps		(1.5		)		7.5				Operating costs and expenses
Coal trading commodity futures, swaps and options		20.8				25.7				Other revenues
Insignificant items		(0.1		)		(0.3		)
		6.7				180.1				Total before income taxes
		(1.7		)		(64.7		)		Income tax provision
		$	5			$	115.4			Total after income taxes
Available-for-sale securities:
Debt securities		$	—			$	0.1			Interest income
Equity securities		—				(21.5		)		Asset impairment
		—				(21.4		)		Total before income taxes
		—				7.9				Income tax benefit
		$	—			$	(13.5	)		Total after income taxes
(1)	Presented as gains (losses) in the unaudited condensed consolidated statements of operations.

Resource_Management_and_Other_

Resource Management and Other Commercial Events (Notes)	6 Months Ended
	Jun. 30, 2014
Resource Management, Acquisitions and Other Commercial Events [Abstract]	'
Resource Management And Other Commercial Events [Text Block]	'
	Resource Management and Other Commercial Events
	Coal Supply Agreement
	During April 2014, the Company finalized pricing under a sales agreement for one of its Western U.S. Mining segment customers. As a result of that agreement, during the three and six months ended June 30, 2014 the Company recognized additional contract revenue totaling $43.2 million and $33.5 million, respectively, and additional sales-related expenses totaling $8.2 million and $6.4 million, respectively, and will realize higher prices for coal supplied pursuant to that agreement in 2014.
	Divestitures
	In January 2014, the Company sold a non-strategic exploration tenement asset in Australia in exchange for cash proceeds of $62.6 million.  The Company had previously recorded an impairment charge in December 2013 to write down the carrying value of that asset to its fair value. Accordingly, there was no gain or loss recognized on the disposal during the six months ended June 30, 2014.
	In June 2013, the Company sold non-strategic coal reserves and surface lands located in Kentucky in exchange for cash proceeds of $35.0 million and short-term notes receivable totaling $35.0 million, which were subsequently collected in December 2013. The Company recognized a gain on sale of $40.3 million related to the transaction, which was classified in "Net gain on disposal or exchange of assets" in the unaudited condensed consolidated statements of operations for the three and six months ended June 30, 2013.

Earnings_per_Share_EPS

Earnings per Share (EPS)	6 Months Ended
	Jun. 30, 2014
Earnings Per Share [Abstract]	'
Earnings per Share (EPS)	'
	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 to the consolidated financial statements in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013.
	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 to the consolidated financial statements in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013. 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 stock options and restricted stock awards of approximately 3.1 million and 3.3 million for the three months ended June 30, 2014 and 2013, respectively, and 4.4 million and 3.3 million for the six months ended June 30, 2014 and 2013, 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:
			Three Months Ended June 30,						Six Months Ended June 30,
			2014			2013			2014			2013
			(Dollars in millions, except per share data)
	EPS numerator:
	(Loss) income from continuing operations, net of income taxes		$	(72.0	)	$	101.4		$	(116.3	)	$	91.1
	Less: Net income (loss) attributable to noncontrolling interests		2.1			(3.2		)	6.5			0.8
	(Loss) income from continuing operations attributable to common stockholders, before allocation of earnings to participating securities		(74.1		)	104.6			(122.8		)	90.3
	Less: Earnings allocated to participating securities		0.3			0.7			0.5			0.2
	(Loss) income from continuing operations attributable to common stockholders, after allocation of earnings to participating securities (1)		(74.4		)	103.9			(123.3		)	90.1
	Income (loss) from discontinued operations, net of income taxes		0.8			(14.3		)	1			(23.4		)
	Less: Loss from discontinued operations allocated to participating securities		—			(0.1		)	—			(0.2		)
	Income (loss) from discontinued operations attributable to common stockholders, after allocation of earnings to participating securities (1)		0.8			(14.2		)	1			(23.2		)
	Net (loss) income attributable to common stockholders, after earnings allocated to participating securities (1)		$	(73.6	)	$	89.7		$	(122.3	)	$	66.9
	EPS denominator:
	Weighted average shares outstanding — basic		268			266.9			267.9			266.9
	Impact of dilutive securities		—			0.6			—			0.5
	Weighted average shares outstanding — diluted		268			267.5			267.9			267.4
	Basic EPS attributable to common stockholders:
	(Loss) income from continuing operations		$	(0.28	)	$	0.39		$	(0.46	)	$	0.34
	Income (loss) from discontinued operations		0.01			(0.06		)	—			(0.09		)
	Net (loss) income attributable to common stockholders		$	(0.27	)	$	0.33		$	(0.46	)	$	0.25
	Diluted EPS attributable to common stockholders:
	(Loss) income from continuing operations		$	(0.28	)	$	0.39		$	(0.46	)	$	0.33
	Income (loss) from discontinued operations		0.01			(0.06		)	—			(0.08		)
	Net (loss) income attributable to common stockholders		$	(0.27	)	$	0.33		$	(0.46	)	$	0.25
	-1	The reallocation adjustment for participating securities to arrive at the numerator used to calculate diluted EPS was less than $0.1 million for the three and six months ended June 30, 2013.

Financial_Instruments_and_Guar

Financial Instruments and Guarantees with Off-Balance-Sheet Risk	6 Months Ended
	Jun. 30, 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, most of which are not reflected in the accompanying condensed 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. Management does not expect any material losses to result from these guarantees or off-balance-sheet instruments.
	Financial Instruments with Off-Balance Sheet Risk
	As of June 30, 2014, the Company had the following financial instruments with off-balance sheet risk:
		Reclamation		Lease		Workers’		Other(1)		Total
		Obligations		Obligations		Compensation
						Obligations
		(Dollars in millions)
	Self bonding	$	1,366.30	$	—	$	—	$	—	$	1,366.30
	Surety bonds	328.1		105.1		98.1		11		542.3
	Bank guarantees	276.5		—		—		140.8		417.3
	Letters of credit	17.6		—		34.1		85.6		137.3
		$	1,988.50	$	105.1	$	132.2	$	237.4	$	2,463.20
	(1)	Other includes the $79.7 million in letters of credit related to Dominion Terminal Associates and TXU Europe Limited described below and an additional $157.7 million in bank guarantees, letters of credit and surety bonds related to collateral for 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 June 30, 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 June 30, 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 June 30, 2014, one of the Company's wholly-owned captive insurance subsidiaries was party to a letter of credit arrangement for $22.5 million in relation to certain of its workers' compensation and other insurance-related obligations whereby that subsidiary has pledged $32.1 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.
	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 June 30, 2014, the Company had $94.6 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 revolving credit facility portion of the Company’s Credit Facility, effectively managing its overall borrowing costs and providing an additional source of 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 six months ended June 30, 2014, the Company received total consideration of $2,108.5 million related to accounts receivable sold under the securitization program, including $1,403.1 million of cash up front from the sale of the receivables, an additional $575.1 million of cash upon the collection of the underlying receivables and $130.3 million that had not been collected at June 30, 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 $110.0 million and $100.0 million at June 30, 2014 and December 31, 2013, respectively.
	The securitization activity has been reflected in the unaudited condensed consolidated statements of cash flows as an operating activity because both the cash received from the Conduits upon sale of the receivables as well as the cash received from the Conduits upon the ultimate collection of the 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 $0.4 million for each of the three months ended June 30, 2014 and 2013, and $0.8 million and $0.7 million for the six months ended June 30, 2014 and 2013, respectively.
	Patriot Bankruptcy Reorganization
	As part of the definitive settlement agreement reached in 2013 with Patriot and the UMWA, which agreement is discussed in Note 18. "Commitments and Contingencies," the Company has provided $135.7 million of credit support to Patriot. Approximately $100 million of this credit support ends in 2018.  As of June 30, 2014, $81.4 million of this credit support took the form of surety bonds issued for the benefit of Patriot beneficiaries; $31.9 million of this credit support took the form of corporate guarantees to Patriot beneficiaries; and $22.4 million of this credit support took the form of letters of credit issued for the benefit of Patriot beneficiaries. Those surety bonds and letters of credit are included in the financial instruments with off-balance sheet risk table, while the corporate guarantees are not. 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.
	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 reached in 2013, 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.
	Other
	Included in "Other noncurrent liabilities" in the Company's condensed consolidated balance sheets as of June 30, 2014 and December 31, 2013 is a liability of $45.6 million related to reclamation, bonding and mine closure commitments 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	6 Months Ended
	Jun. 30, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	Commitments and Contingencies
	Commitments
	Unconditional Purchase Obligations
	As of June 30, 2014, purchase commitments for capital expenditures were $74.8 million, all of which are obligated within the next 12 months.
	There were no other material changes to the Company’s commitments from the information provided in Note 24 to the consolidated financial statements in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013.
	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 in the Supreme Court of New South Wales, Australia, against Wambo alleging that it was entitled to certain dividend payments from Wambo (subject to limited exceptions) and requested payment of those dividends for periods from 2009 to 2012.
	On March 25, 2013, the Supreme Court issued a judgment in favor of Sumiseki's position that it was entitled to dividend payments (subject to limited exceptions), thus requiring Wambo to pay dividends to it for the periods in question. The Supreme Court issued finalized orders on May 3, 2013, including the final calculation of amounts due for dividends during the periods from 2009 to 2012 totaling $29.6 million plus interest of $5.8 million. Amounts of the finalized orders are presented in U.S. dollars at foreign currency exchange rates in effect at June 30, 2014.
	In parallel to Wambo filing an appeal of the Supreme Court's decision to the New South Wales Court of Appeal, a stay was ordered to the Supreme Court judgment. In accordance with the terms of the stay, Wambo posted the requisite security of $49.6 million, which amount includes the calculated potential amounts due for 2013, with the court in the form of cash payment into an interest bearing trust account jointly operated by the parties. Because the Supreme Court's order allows for the substitution of that posted cash payment with a bank guarantee from an Australian bank or another form of acceptable security, those funds remain readily available to the Company and have therefore been reflected in "Cash and cash equivalents" in the unaudited condensed consolidated balance sheet as of June 30, 2014. Based on information currently available, the Company believes that its subsidiary should be successful in the appeals process, and therefore, has not declared any dividends and continues to reflect the previously allocated earnings to "Noncontrolling interests" in the unaudited condensed consolidated balance sheet as of June 30, 2014. If the Supreme Court's ruling is upheld, the Company believes the claims are likely to be finalized without a material adverse effect on its financial condition, results of operations or cash flows.
	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 unaudited condensed consolidated statement of operations for the six months ended June 30, 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.
	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 seeks damages of $113.1 million Australian dollars, plus interest and costs.  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 unaudited condensed consolidated statements of operations for the three and six months ended June 30, 2013.
	Claims, Litigation and Settlements Relating to Indemnities or Historical Operations
	Environmental Claims and Litigation 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 eight 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 $60.6 million as of June 30, 2014 and $63.8 million as of December 31, 2013, $15.2 million and $18.3 million of which was reflected as a current liability, respectively, in the condensed 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 condensed 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.
	Settlement Agreement with Patriot and the UMWA. In 2012, Patriot Coal Corporation and certain of its wholly owned subsidiaries (Patriot) filed voluntary petitions for reorganization under Chapter 11 of the U.S. Bankruptcy Code. In 2013, the Company entered into a definitive settlement agreement with Patriot and the United Mine Workers of America (UMWA), on behalf of itself, its represented Patriot employees and its represented Patriot retirees, to resolve all disputed issues related to Patriot’s bankruptcy.
	In connection with the settlement agreement with Patriot and the UMWA, which became effective on December 18, 2013, the Company is required to provide total payments of $310 million, payable over four years through 2017, to partially fund the newly established voluntary employee beneficiary association (VEBA) and settle all Patriot and UMWA claims involving the Patriot bankruptcy. Those payments included an initial payment of $90 million made in January 2014, comprised of $70 million paid to Patriot and $20 million paid to the VEBA, and subsequent payments to be paid to the VEBA of $75 million in 2015, $75 million in 2016 and $70 million in 2017.
	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.

Segment_Information

Segment Information	6 Months Ended
	Jun. 30, 2014
Segment Reporting [Abstract]	'
Segment Information	'
	Segment Information
	The Company reports its results of operations primarily through the following reportable segments: “Australian Mining," “Western U.S. Mining,” “Midwestern U.S. Mining,” “Trading and Brokerage” and “Corporate and Other.” The Company’s chief operating decision maker uses Adjusted EBITDA as the primary measure of segment profit and loss. 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 amortization of basis difference related to equity affiliates.
	Reportable segment results were as follows:
		Three Months Ended June 30,						Six Months Ended June 30,
		2014			2013			2014			2013
		(Dollars in millions)
	Revenues:
	Australian Mining	$	707.4		$	744.8		$	1,319.20		$	1,482.80
	Western U.S. Mining	726.6			640.9			1,408.60			1,281.00
	Midwestern U.S. Mining	304.6			330			607.6			666.7
	Trading and Brokerage	10.3			(3.4		)	31.3			22.5
	Corporate and Other	9.1			13			18.1			20.3
	Total	$	1,758.00		$	1,725.30		$	3,384.80		$	3,473.30
	Adjusted EBITDA:
	Australian Mining	$	12.2		$	112.5		$	14		$	212.9
	Western U.S. Mining	222			154.9			395.9			315.4
	Midwestern U.S. Mining	69.9			106.8			148.6			219.1
	Trading and Brokerage	6.3			(41.0		)	4.4			(25.0		)
	Corporate and Other	(97.3		)	(78.9		)	(172.9		)	(188.0		)
	Total	$	213.1		$	254.3		$	390		$	534.4
	A reconciliation of Adjusted EBITDA to consolidated (loss) income from continuing operations, net of income taxes follows:
		Three Months Ended June 30,						Six Months Ended June 30,
		2014			2013			2014			2013
		(Dollars in millions)
	Adjusted EBITDA	$	213.1		$	254.3		$	390		$	534.4
	Depreciation, depletion and amortization	(163.1		)	(185.7		)	(320.3		)	(356.4		)
	Asset impairment	—			(21.5		)	—			(21.5		)
	Amortization of basis difference related to equity affiliates	(1.3		)	(2.4		)	(2.5		)	(4.0		)
	Asset retirement obligation expenses	(15.9		)	(18.3		)	(31.5		)	(37.3		)
	Interest expense	(105.2		)	(110.8		)	(208.5		)	(212.1		)
	Interest income	4.4			1.1			8			7
	Income tax (provision) benefit	(4.0		)	184.7			48.5			181
	(Loss) income from continuing operations, net of income taxes	$	(72.0	)	$	101.4		$	(116.3	)	$	91.1

Supplemental_GuarantorNonGuara

Supplemental Guarantor/Non-Guarantor Financial Information	6 Months Ended
	Jun. 30, 2014															Jun. 30, 2013
Supplemental Guarantor Non Guarantor Financial Information [Abstract]	'															'
Supplemental Guarantor Non Guarantor Financial Information Disclosure [Text Block]	'															'
	Supplemental Guarantor/Non-Guarantor Financial Information															Unaudited Supplemental Condensed Consolidating Statements of Operations
	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 (a) the release or discharge of the guarantee of the Company’s Credit Agreement by such Guarantor Subsidiary, except a discharge or release by or as a result of payment under such guarantee, (b) a sale or other disposition, by way of merger, consolidation or otherwise, of all of the capital stock of such Guarantor Subsidiary, and (c) 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.
	Unaudited Supplemental Condensed Consolidating Balance Sheets
																	Three Months Ended June 30, 2014
																	Parent			Guarantor			Non-Guarantor			Eliminations			Consolidated
		June 30, 2014															Company			Subsidiaries			Subsidiaries
		Parent			Guarantor			Non-Guarantor			Reclassifications/			Consolidated			(Dollars in millions)
		Company			Subsidiaries			Subsidiaries			Eliminations					Total revenues	$	—		$	1,005.00		$	774.9		$	(21.9	)	$	1,758.00
		(Dollars in millions)
	Assets															Costs and expenses
	Current assets															Operating costs and expenses (exclusive of items shown separately below)	(7.3		)	741.2			755.6			(21.9		)	1,467.60
	Cash and cash equivalents	$	323.6		$	0.2		$	174.6		$	—		$	498.4
																Depreciation, depletion and amortization	—			76.2			86.9			—			163.1
	Accounts receivable, net	0.3			—			447.1			(0.3		)	447.1
																Asset retirement obligation expenses	—			7			8.9			—			15.9
	Receivables from affiliates, net	369.2			—			—			(369.2		)	—
																Selling and administrative expenses	11			42.8			5.4			—			59.2
	Inventories	—			217.6			330.8			—			548.4
																Other operating (income) loss:
	Assets from coal trading activities, net	—			46.1			4.7			—			50.8		Net (gain) loss on disposal or exchange of assets	—			(2.3		)	0.1			—			(2.2		)
	Deferred income taxes	24			36			7.2			—			67.2		Loss (income) from equity affiliates and investment in subsidiaries	4.4			2.1			19.5			(4.4		)	21.6
	Other current assets	11.1			17.2			237.6			—			265.9		Interest expense	107.2			1.7			1.7			(5.4		)	105.2
	Total current assets	728.2			317.1			1,202.00			(369.5		)	1,877.80		Interest income	(0.1		)	(2.1		)	(7.6		)	5.4			(4.4		)
	Property, plant, equipment and mine development, net	—			4,904.60			5,795.90			—			10,700.50		(Loss) income from continuing operations before income taxes	(115.2		)	138.4			(95.6		)	4.4			(68.0		)
	Deferred income taxes	—			—			79.4			2.7			82.1		Income tax (benefit) provision	(41.0		)	41			4			—			4
	Investments and other assets	10,704.60			8.5			742.9			(10,424.2		)	1,031.80		(Loss) income from continuing operations, net of income taxes	(74.2		)	97.4			(99.6		)	4.4			(72.0		)
	Notes receivable from affiliates, net	—			1,546.80			—			(1,546.8		)	—		Income (loss) from discontinued operations, net of income taxes	0.9			(0.5		)	0.4			—			0.8
	Total assets	$	11,432.80		$	6,777.00		$	7,820.20		$	(12,337.8	)	$	13,692.20	Net (loss) income	(73.3		)	96.9			(99.2		)	4.4			(71.2		)
	Liabilities and Stockholders’ Equity															Less: Net income attributable to noncontrolling interests	—			—			2.1			—			2.1
	Current liabilities
	Current maturities of long-term debt	$	12		$	0.1		$	8.7		$	—		$	20.8	Net (loss) income attributable to common stockholders	$	(73.3	)	$	96.9		$	(101.3	)	$	4.4		$	(73.3	)
	Payables to affiliates, net	—			296.5			72.7			(369.2		)	—		Unaudited Supplemental Condensed Consolidating Statements of Comprehensive Income
	Deferred income taxes	—			—			7.5			—			7.5
																	Three Months Ended June 30, 2014
	Liabilities from coal trading activities, net	—			4.8			9.6			—			14.4			Parent			Guarantor			Non-Guarantor			Eliminations			Consolidated
																	Company			Subsidiaries			Subsidiaries
	Accounts payable and accrued expenses	194.2			580.9			687.2			(0.3		)	1,462.00			(Dollars in millions)
																Net (loss) income	$	(73.3	)	$	96.9		$	(99.2	)	$	4.4		$	(71.2	)
	Total current liabilities	206.2			882.3			785.7			(369.5		)	1,504.70
																Other comprehensive income (loss), net of income taxes	74.5			(7.5		)	2.6			4.9			74.5
	Long-term debt, less current maturities	5,955.30			6.4			11.5			—			5,973.20
																Comprehensive income (loss)	1.2			89.4			(96.6		)	9.3			3.3
	Deferred income taxes	22.4			34.4			—			2.7			59.5
																Less: Comprehensive income attributable to noncontrolling interests	—			—			2.1			—			2.1
	Notes payable to affiliates, net	1,078.10			—			468.7			(1,546.8		)	—
																Comprehensive income (loss) attributable to common stockholders	$	1.2		$	89.4		$	(98.7	)	$	9.3		$	1.2
	Other noncurrent liabilities	210			1,555.00			385.4			—			2,150.40
																Unaudited Supplemental Condensed Consolidating Statements of Operations
	Total liabilities	7,472.00			2,478.10			1,651.30			(1,913.6		)	9,687.80
	Peabody Energy Corporation stockholders’ equity	3,960.80			4,298.90			6,125.30			(10,424.2		)	3,960.80			Three Months Ended June 30, 2013
																	Parent			Guarantor			Non-Guarantor			Eliminations			Consolidated
	Noncontrolling interests	—			—			43.6			—			43.6			Company			Subsidiaries			Subsidiaries
																	(Dollars in millions)
	Total stockholders’ equity	3,960.80			4,298.90			6,168.90			(10,424.2		)	4,004.40		Total revenues	$	—		$	972.5		$	818.8		$	(66.0	)	$	1,725.30
	Total liabilities and stockholders’ equity	$	11,432.80		$	6,777.00		$	7,820.20		$	(12,337.8	)	$	13,692.20	Costs and expenses
																Operating costs and expenses (exclusive of items shown separately below)	(62.8		)	823			743			(66.0		)	1,437.20
	Supplemental Condensed Consolidating Balance Sheets															Depreciation, depletion and amortization	—			85.5			100.2			—			185.7
																Asset retirement obligation expenses	—			10.2			8.1			—			18.3
		December 31, 2013
		Parent			Guarantor			Non-Guarantor			Reclassifications/			Consolidated		Selling and administrative expenses	14.6			44.3			5.1			—			64
		Company			Subsidiaries			Subsidiaries			Eliminations
		(Dollars in millions)														Other operating (income) loss:
	Assets															Net gain on disposal or exchange of assets	—			(43.0		)	(0.2		)	—			(43.2		)
Current assets
Cash and cash equivalents	$	300.7		$	0.3		$	143		$	—		$	444	Asset impairment	21.5			—			—			—			21.5
Accounts receivable, net	1.3			—			559.1			(2.5		)	557.9		(Income) loss from equity affiliates and investment in subsidiaries	(174.4		)	4.5			10.9			174.4			15.4
Receivables from affiliates, net	68.4			—			—			(68.4		)	—		Interest expense	101.3			8.7			95.4			(94.6		)	110.8
Inventories	—			235.1			271.6			—			506.7		Interest income	(0.1		)	(90.5		)	(5.1		)	94.6			(1.1		)
Assets from coal trading activities, net	—			46.7			—			(10.6		)	36.1		Unrealized loss (gain) on derivatives	—			502.6			(502.6		)	—			—
Deferred income taxes	—			61.9			6.4			(1.9		)	66.4		Income (loss) from continuing operations before income taxes	99.9			(372.8		)	364			(174.4		)	(83.3		)
Other current assets	34.5			73.7			273.4			—			381.6		Income tax provision (benefit)	5.8			(193.1		)	2.6			—			(184.7		)
Total current assets	404.9			417.7			1,253.50			(83.4		)	1,992.70		Income (loss) from continuing operations, net of income taxes	94.1			(179.7		)	361.4			(174.4		)	101.4
Property, plant, equipment and mine development, net	—			5,055.70			6,026.80			—			11,082.50		Loss from discontinued operations, net of income taxes	(3.8		)	(1.0		)	(9.5		)	—			(14.3		)
Deferred income taxes	16.5			—			7.8			(16.5		)	7.8		Net income (loss)	90.3			(180.7		)	351.9			(174.4		)	87.1
Investments and other assets	11,394.90			8.8			762.6			(11,115.9		)	1,050.40		Less: Net loss attributable to noncontrolling interests	—			—			(3.2		)	—			(3.2		)
Notes receivable from affiliates, net	—			1,478.60			—			(1,478.6		)	—		Net income (loss) attributable to common stockholders	$	90.3		$	(180.7	)	$	355.1		$	(174.4	)	$	90.3
Total assets	$	11,816.30		$	6,960.80		$	8,050.70		$	(12,694.4	)	$	14,133.40	Unaudited Supplemental Condensed Consolidating Statements of Comprehensive Income
Liabilities and Stockholders’ Equity
Current liabilities																Three Months Ended June 30, 2013
Current maturities of long-term debt	$	12		$	0.1		$	19.6		$	—		$	31.7		Parent			Guarantor			Non-Guarantor			Eliminations			Consolidated
																Company			Subsidiaries			Subsidiaries
Payables to affiliates, net	—			10.4			58			(68.4		)	—			(Dollars in millions)
															Net income (loss)	$	90.3		$	(180.7	)	$	351.9		$	(174.4	)	$	87.1
Deferred income taxes	1.9			—			—			(1.9		)	—
															Other comprehensive (loss) income, net of income taxes	(431.6		)	51			(49.9		)	(1.1		)	(431.6		)
Liabilities from coal trading activities, net	—			0.2			16.5			(10.6		)	6.1
															Comprehensive (loss) income	(341.3		)	(129.7		)	302			(175.5		)	(344.5		)
Accounts payable and accrued expenses	360			577.7			802.5			(2.5		)	1,737.70
															Less: Comprehensive loss attributable to noncontrolling interests	—			—			(3.2		)	—			(3.2		)
Total current liabilities	373.9			588.4			896.6			(83.4		)	1,775.50
															Comprehensive (loss) income attributable to common stockholders	$	(341.3	)	$	(129.7	)	$	305.2		$	(175.5	)	$	(341.3	)
Long-term debt, less current maturities	5,959.10			6.5			5.1			—			5,970.70
															Unaudited Supplemental Condensed Consolidating Statements of Operations
Deferred income taxes	—			55.9			1.5			(16.5		)	40.9
Notes payable to affiliates, net	1,078.20			—			400.4			(1,478.6		)	—			Six Months Ended June 30, 2014
																Parent			Guarantor			Non-Guarantor			Eliminations			Consolidated
Other noncurrent liabilities	496.4			1,521.80			380.2			—			2,398.40			Company			Subsidiaries			Subsidiaries
																(Dollars in millions)
Total liabilities	7,907.60			2,172.60			1,683.80			(1,578.5		)	10,185.50		Total revenues	$	—		$	1,981.40		$	1,446.20		$	(42.8	)	$	3,384.80
Peabody Energy Corporation stockholders’ equity	3,908.70			4,788.20			6,327.70			(11,115.9		)	3,908.70		Costs and expenses
															Operating costs and expenses (exclusive of items shown separately below)	13.9			1,468.00			1,423.30			(42.8		)	2,862.40
Noncontrolling interests	—			—			39.2			—			39.2
															Depreciation, depletion and amortization	—			153.4			166.9			—			320.3
Total stockholders’ equity	3,908.70			4,788.20			6,366.90			(11,115.9		)	3,947.90
															Asset retirement obligation expenses	—			15.6			15.9			—			31.5
Total liabilities and stockholders’ equity	$	11,816.30		$	6,960.80		$	8,050.70		$	(12,694.4	)	$	14,133.40
															Selling and administrative expenses	24.6			84.1			10			—			118.7
Unaudited Supplemental Condensed Consolidating Statements of Cash Flows
															Other operating (income) loss:
															Net gain on disposal or exchange of assets	—			(11.9		)	(0.1		)	—			(12.0		)
	Six Months Ended June 30, 2014
	Parent			Guarantor			Non-Guarantor			Consolidated					(Income) loss from equity affiliates and investment in subsidiaries	(35.2		)	2.7			25.5			35.2			28.2
	Company			Subsidiaries			Subsidiaries
	(Dollars in millions)														Interest expense	212.9			3.3			3.1			(10.8		)	208.5
Cash Flows From Operating Activities
Net cash (used in) provided by continuing operations	$	(112.4	)	$	330.3		$	(60.8	)	$	157.1				Interest income	(0.2		)	(4.5		)	(14.1		)	10.8			(8.0		)
Net cash used in discontinued operations	(72.9		)	(1.4		)	(7.5		)	(81.8		)			(Loss) income from continuing operations before income taxes	(216.0		)	270.7			(184.3		)	(35.2		)	(164.8		)
Net cash (used in) provided by operating activities	(185.3		)	328.9			(68.3		)	75.3
															Income tax (benefit) provision	(93.0		)	65.8			(21.3		)	—			(48.5		)
Cash Flows From Investing Activities
Additions to property, plant, equipment and mine development	—			(32.1		)	(32.6		)	(64.7		)			(Loss) income from continuing operations, net of income taxes	(123.0		)	204.9			(163.0		)	(35.2		)	(116.3		)
Changes in accrued expenses related to capital expenditures	—			(1.3		)	(16.2		)	(17.5		)			Income (loss) from discontinued operations, net of income taxes	1.2			(1.2		)	1			—			1
Proceeds from disposal of assets, net of notes receivable	—			50.9			88.3			139.2					Net (loss) income	(121.8		)	203.7			(162.0		)	(35.2		)	(115.3		)
Purchases of debt securities	—			—			(4.2		)	(4.2		)			Less: Net income attributable to noncontrolling interests	—			—			6.5			—			6.5
Proceeds from sales and maturities of debt securities	—			—			5			5					Net (loss) income attributable to common stockholders	$	(121.8	)	$	203.7		$	(168.5	)	$	(35.2	)	$	(121.8	)
Contributions to joint ventures	—			—			(271.3		)	(271.3		)			Unaudited Supplemental Condensed Consolidating Statements of Comprehensive Income
Distributions from joint ventures	—			—			269			269
																Six Months Ended June 30, 2014
Advances to related parties	—			—			(12.3		)	(12.3		)				Parent			Guarantor			Non-Guarantor			Eliminations			Consolidated
																Company			Subsidiaries			Subsidiaries
Repayments of loans from related parties	—			—			2.2			2.2						(Dollars in millions)
															Net (loss) income	$	(121.8	)	$	203.7		$	(162.0	)	$	(35.2	)	$	(115.3	)
Other, net	—			(1.7		)	(0.3		)	(2.0		)
															Other comprehensive income (loss), net of income taxes	200.4			2.4			(15.9		)	13.5			200.4
Net cash provided by continuing operations	—			15.8			27.6			43.4
															Comprehensive income (loss)	78.6			206.1			(177.9		)	(21.7		)	85.1
Net cash provided by discontinued operations	—			—			5			5
															Less: Comprehensive income attributable to noncontrolling interests	—			—			6.5			—			6.5
Net cash provided by investing activities	—			15.8			32.6			48.4
															Comprehensive income (loss) attributable to common stockholders	$	78.6		$	206.1		$	(184.4	)	$	(21.7	)	$	78.6
Cash Flows From Financing Activities
Repayments of long-term debt	(6.0		)	—			(4.4		)	(10.4		)			Unaudited Supplemental Condensed Consolidating Statements of Operations
Payment of debt issuance costs	(10.1		)	—			—			(10.1		)
																Six Months Ended June 30, 2013
Dividends paid	(46.1		)	—			—			(46.1		)				Parent			Guarantor			Non-Guarantor			Eliminations			Consolidated
																Company			Subsidiaries			Subsidiaries
Other, net	1			(1.7		)	(2.0		)	(2.7		)				(Dollars in millions)
															Total revenues	$	—		$	1,987.10		$	1,615.00		$	(128.8	)	$	3,473.30
Transactions with affiliates, net	269.4			(343.1		)	73.7			—
															Costs and expenses
Net cash provided by (used in) financing activities	208.2			(344.8		)	67.3			(69.3		)			Operating costs and expenses (exclusive of items shown separately below)	(154.5		)	1,523.90			1,586.00			(128.8		)	2,826.60
Net change in cash and cash equivalents	22.9			(0.1		)	31.6			54.4					Depreciation, depletion and amortization	—			165.1			191.3			—			356.4
Cash and cash equivalents at beginning of period	300.7			0.3			143			444					Asset retirement obligation expenses	—			21.8			15.5			—			37.3
Cash and cash equivalents at end of period	$	323.6		$	0.2		$	174.6		$	498.4				Selling and administrative expenses	23.8			91.7			13.6			—			129.1
Unaudited Supplemental Condensed Consolidating Statements of Cash Flows															Other operating (income) loss:
															Net gain on disposal or exchange of assets	—			(45.8		)	—			—			(45.8		)
	Six Months Ended June 30, 2013														Asset impairment	21.5			—			—			—			21.5
	Parent			Guarantor			Non-Guarantor			Consolidated
	Company			Subsidiaries			Subsidiaries								(Income) loss from equity affiliates and investment in subsidiaries	(89.6		)	8.4			24.6			89.6			33
	(Dollars in millions)
Cash Flows From Operating Activities															Interest expense	203.2			11			205.9			(208.0		)	212.1
Net cash provided by (used in) continuing operations	$	114.5		$	496.5		$	(245.1	)	$	365.9
															Interest income	(68.2		)	(125.4		)	(21.4		)	208			(7.0		)
Net cash (used in) provided by discontinued operations	(8.1		)	0.5			(26.9		)	(34.5		)
															Unrealized loss (gain) on derivatives	—			461.6			(461.6		)	—			—
Net cash provided by (used in) operating activities	106.4			497			(272.0		)	331.4
															Income (loss) from continuing operations before income taxes	63.8			(125.2		)	61.1			(89.6		)	(89.9		)
Cash Flows From Investing Activities
Additions to property, plant, equipment and mine development	—			(45.1		)	(121.4		)	(166.5		)			Income tax benefit	(9.5		)	(85.2		)	(86.3		)	—			(181.0		)
Changes in accrued expenses related to capital expenditures	—			(2.4		)	(100.2		)	(102.6		)			Income (loss) from continuing operations, net of income taxes	73.3			(40.0		)	147.4			(89.6		)	91.1
Proceeds from disposal of assets, net of notes receivable	—			42.1			81.8			123.9					Loss from discontinued operations, net of income taxes	(6.4		)	(2.5		)	(14.5		)	—			(23.4		)
Purchases of debt securities	—			—			(9.7		)	(9.7		)			Net income (loss)	66.9			(42.5		)	132.9			(89.6		)	67.7
Proceeds from sales and maturities of debt securities	—			—			17			17					Less: Net income attributable to noncontrolling interests	—			—			0.8			—			0.8
Proceeds from the maturity of short-term investments	—			—			4.8			4.8					Net income (loss) attributable to common stockholders	$	66.9		$	(42.5	)	$	132.1		$	(89.6	)	$	66.9
Contributions to joint ventures	—			—			(323.8		)	(323.8		)			Unaudited Supplemental Condensed Consolidating Statements of Comprehensive Income
Distributions from joint ventures	—			—			372.1			372.1
																Six Months Ended June 30, 2013
Advances to related parties	—			—			(35.7		)	(35.7		)				Parent			Guarantor			Non-Guarantor			Eliminations			Consolidated
																Company			Subsidiaries			Subsidiaries
Repayments of loans from related parties	—			—			18.2			18.2						(Dollars in millions)
															Net income (loss)	$	66.9		$	(42.5	)	$	132.9		$	(89.6	)	$	67.7
Other, net	—			(3.4		)	(0.2		)	(3.6		)
															Other comprehensive (loss) income, net of income taxes	(431.0		)	28.5			(64.1		)	35.6			(431.0		)
Net cash used in continuing operations	—			(8.8		)	(97.1		)	(105.9		)
															Comprehensive (loss) income	(364.1		)	(14.0		)	68.8			(54.0		)	(363.3		)
Net cash used in discontinued operations	—			—			(0.3		)	(0.3		)
															Less: Comprehensive income attributable to noncontrolling interests	—			—			0.8			—			0.8
Net cash used in investing activities	—			(8.8		)	(97.4		)	(106.2		)
															Comprehensive (loss) income attributable to common stockholders	$	(364.1	)	$	(14.0	)	$	68		$	(54.0	)	$	(364.1	)
Cash Flows From Financing Activities
Repayments of long-term debt	(167.0		)	(0.1		)	(48.5		)	(215.6		)
Dividends paid	(45.9		)	—			—			(45.9		)
Other, net	0.9			(5.2		)	(0.3		)	(4.6		)
Transactions with affiliates, net	169.8			(483.0		)	313.2			—
Net cash (used in) provided by financing activities	(42.2		)	(488.3		)	264.4			(266.1		)
Net change in cash and cash equivalents	64.2			(0.1		)	(105.0		)	(40.9		)
Cash and cash equivalents at beginning of period	269.6			0.3			288.9			558.8
Cash and cash equivalents at end of period	$	333.8		$	0.2		$	183.9		$	517.9

Derivatives_and_Fair_Value_Mea1

Derivatives and Fair Value Measurements Fair value transfer timing policy (Policies)	6 Months Ended
	Jun. 30, 2014
Fair value transfer policy [Abstract]	'
Fair Value Transfer, Policy [Policy Text Block]	'
	The Company’s policy is to value transfers between levels using the beginning of period valuation.

Discontinued_Operations_Tables

Discontinued Operations (Tables)	6 Months Ended
	Jun. 30, 2014
Discontinued Operations and Disposal Groups [Abstract]	'
Results of discontinued operations [Table Text Block]	'
	Results from discontinued operations were as follows during the three and six months ended June 30, 2014 and 2013:
		Three Months Ended June 30,						Six Months Ended June 30,
		2014			2013			2014			2013
		(Dollars in millions)
	Income (loss) from discontinued operations before income taxes	$	1.2		$	(16.1	)	$	1.1		$	(32.7	)
	Income tax provision (benefit)	0.4			(1.8		)	0.1			(9.3		)
	Income (loss) from discontinued operations, net of income taxes	$	0.8		$	(14.3	)	$	1		$	(23.4	)
Assets and Liabilities of Discontinued Operations [Table Text Block]	'
	The carrying amounts of assets and liabilities classified as discontinued operations included in the Company's condensed consolidated balance sheets were as follows:
		June 30, 2014			December 31, 2013
		(Dollars in millions)
	Assets:
	Other current assets	$	2.4		$	38.6
	Investments and other assets	20.8			47.4
	Total assets classified as discontinued operations	$	23.2		$	86
	Liabilities:
	Accounts payable and accrued expenses	$	42.3		$	127.8
	Other noncurrent liabilities	86.7			90.2
	Total liabilities classified as discontinued operations	$	129		$	218
Restructuring and Related Costs [Table Text Block]	'
	The following table summarizes the changes in those liabilities for the six months ended June 30, 2014:
		Accrued Take-or-Pay Liabilities			Other Exit Costs			Total
		(Dollars in millions)
	Liability balance at December 31, 2013	$	33.9		$	2.7		$	36.6
	Change in estimate	—			(0.2		)	(0.2		)
	Cash payments	(6.3		)	(2.4		)	(8.7		)
	Foreign currency remeasurement expense	1.6			—			1.6
	Liability balance at June 30, 2014	$	29.2		$	0.1		$	29.3

Investments_Tables

Investments (Tables)	6 Months Ended
	Jun. 30, 2014
Investments, Debt and Equity Securities [Abstract]	'
Investments in available-for-sale securities	'
	Investments in available-for-sale securities at June 30, 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	$	8.9	$	—	$	—		$	8.9
	Noncurrent:
	Marketable equity securities	10.9		—		(0.9		)	10
	Federal government securities	29.3		—		—			29.3
	U.S. corporate bonds	15.4		0.1		—			15.5
	Total	$	64.5	$	0.1	$	(0.9	)	$	63.7
	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
Contractual maturities for available for sale investment in debt securities	'
	Contractual maturities for available-for-sale investments in debt securities at June 30, 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 debt securities	Cost		Fair Value
		(Dollars in millions)
	Due in one year or less	$	8.9	$	8.9
	Due in one to five years	44.7		44.8
	Total	$	53.6	$	53.7

Inventories_Tables

Inventories (Tables)	6 Months Ended
	Jun. 30, 2014
Inventory Disclosure [Abstract]	'
Inventories	'
	Inventories as of June 30, 2014 and December 31, 2013 consisted of the following:
		June 30, 2014		December 31, 2013
		(Dollars in millions)
	Materials and supplies	$	166.3	$	166.8
	Raw coal	141.5		122.6
	Saleable coal	240.6		217.3
	Total	$	548.4	$	506.7

Derivatives_and_Fair_Value_Mea2

Derivatives and Fair Value Measurements (Tables) (Non Coal Trading [Member])	6 Months Ended
	Jun. 30, 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 June 30, 2014:
		Notional Amount by Year of Maturity
		Total				2014				2015				2016				2017
	Foreign Currency
	A$:US$ hedge contracts (A$ millions)	$	4,082.10			$	935			$	1,645.10			$	997			$	505
	Commodity Contracts
	Diesel fuel hedge contracts (million gallons)	208.5				52.2				85.5				53.3				17.5
	U.S. explosives hedge contracts (million MMBtu)	0.3				0.3				—				—				—
		Instrument Classification by
		Cash Flow				Fair Value				Economic					Fair Value Net Asset (Liability)
		Hedge				Hedge				Hedge
															(Dollars in millions)
	Foreign Currency
	A$:US$ hedge contracts (A$ millions)	$	4,082.10			$	—			$	—				$	(109.6	)
	Commodity Contracts
	Diesel fuel hedge contracts (million gallons)	208.5				—				—					16
	U.S. explosives hedge contracts (million MMBtu)	0.3				—				—					(0.2		)
Classification and amounts of pre-tax gains and losses related to the Company's non coal-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 three and six months ended June 30, 2014 and 2013:
					Three Months Ended June 30, 2014
	Financial Instrument		Income Statement		Gain recognized in income on non-designated derivatives				Gain recognized in other comprehensive income on derivatives				(Loss) gain reclassified from other comprehensive income into income				Gain reclassified from other comprehensive income into income
			Classification Gains (Losses) -						(effective portion) (1)				(effective portion) (1)				(ineffective portion)
			Realized
					(Dollars in millions)
	Commodity swaps and options		Operating costs and expenses		$	—			$	17.7			$	(0.1	)		$	1
	Foreign currency forward contracts		Operating costs and expenses		—				134.7				6.3				—
	Total				$	—			$	152.4			$	6.2			$	1
					Three Months Ended June 30, 2013
	Financial Instrument		Income Statement		Gain recognized in income on non-designated derivatives				Loss recognized in other comprehensive income on derivatives				Gain reclassified from other comprehensive income into income				Gain reclassified from other comprehensive income into income
			Classification Gains (Losses) -						(effective portion)				(effective portion)				(ineffective portion)
			Realized
					(Dollars in millions)
	Commodity swaps and options		Operating costs and expenses		$	—			$	(25.0	)		$	0.5			$	0.1
	Foreign currency forward contracts		Operating costs and expenses		—				(492.6		)		62.1				—
	Total				$	—			$	(517.6	)		$	62.6			$	0.1
	(1)	Includes the reclassification from "Accumulated other comprehensive loss" into earnings of $33.9 million of previously unrecognized gains on foreign currency cash flow hedge contracts monetized in the fourth quarter of 2012.
					Six Months Ended June 30, 2014
	Financial Instrument		Income Statement		Gain recognized in income on non-designated derivatives				Gain recognized in other comprehensive income on derivatives				Loss reclassified from other comprehensive income into income				Gain reclassified from other comprehensive income into income
			Classification Gains (Losses) -						(effective portion) (1)				(effective portion) (1)				(ineffective portion)
			Realized
					(Dollars in millions)
	Commodity swaps and options		Operating costs and expenses		$	—			$	9.2			$	(2.3	)		$	0.8
	Foreign currency forward contracts		Operating costs and expenses		—				351.2				(12.5		)		—
	Total				$	—			$	360.4			$	(14.8	)		$	0.8
					Six Months Ended June 30, 2013
	Financial Instrument		Income Statement		Gain recognized in income on non-designated derivatives				Loss recognized in other comprehensive income on derivatives				Gain reclassified from other comprehensive income into income				Gain reclassified from other comprehensive income into income
			Classification Gains (Losses) -						(effective portion)				(effective portion)				(ineffective portion)
			Realized
					(Dollars in millions)
	Commodity swaps and options		Operating costs and expenses		$	—			$	(19.1	)		$	7.2			$	0.3
	Foreign currency forward contracts		Operating costs and expenses		—				(453.9		)		147.2				—
	Total				$	—			$	(473.0	)		$	154.4			$	0.3
	(1)	Includes the reclassification from "Accumulated other comprehensive loss" into earnings of $74.8 million of previously unrecognized gains on foreign currency cash flow hedge contracts monetized in the fourth quarter of 2012.
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 June 30, 2014 and December 31, 2013 are presented in the tables that follow.
			Fair Value of Assets as of June 30, 2014
	Financial Instrument		Gross Amounts Recognized				Gross Amounts Offset in the Condensed Consolidated Balance Sheet				Net Amounts Presented in the Condensed Consolidated Balance Sheet				Derivatives Not Offset in the Condensed Consolidated Balance Sheet (1)				Net Amount
			(Dollars in millions)
	Current Assets:
	Commodity swap contracts		$	9.7			$	(0.7	)		$	9			n.a.				n.a.
	Foreign currency forward contracts		11.6				(10.2		)		1.4				n.a.				n.a.
	Total		$	21.3			$	(10.9	)		$	10.4			$	(7.5	)		$	2.9
	Noncurrent Assets:
	Commodity swap contracts		$	8			$	(0.5	)		$	7.5			n.a.				n.a.
	Foreign currency forward contracts		17.4				(16.6		)		0.8				n.a.				n.a.
	Total		$	25.4			$	(17.1	)		$	8.3			$	(5.4	)		$	2.9
	(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 June 30, 2014
	Financial Instrument		Gross Amounts Recognized				Gross Amounts Offset in the Condensed Consolidated Balance Sheet				Net Amounts Presented in the Condensed Consolidated Balance Sheet				Derivatives Not Offset in the Condensed Consolidated Balance Sheet (1)				Net Amount
			(Dollars in millions)
	Current Liabilities:
	Commodity swap contracts		$	1.4			$	(0.8	)		$	0.6			n.a.				n.a.
	Foreign currency forward contracts		76.4				(12.9		)		63.5				n.a.				n.a.
	Total		$	77.8			$	(13.7	)		$	64.1			$	(7.4	)		$	56.7
	Noncurrent Liabilities:
	Commodity swap contracts		$	0.5			$	(0.4	)		$	0.1			n.a.				n.a.
	Foreign currency forward contracts		62.2				(13.9		)		48.3				n.a.				n.a.
	Total		$	62.7			$	(14.3	)		$	48.4			$	(5.5	)		$	42.9
	(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 Assets as of December 31, 2013
	Financial Instrument		Gross Amounts Recognized				Gross Amounts Offset in the Condensed Consolidated Balance Sheet				Net Amounts Presented in the Condensed Consolidated Balance Sheet				Derivatives Not Offset in the Condensed Consolidated Balance Sheet (1)				Net Amount
			(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
	Financial Instrument		Gross Amounts Recognized				Gross Amounts Offset in the Condensed Consolidated Balance Sheet				Net Amounts Presented in the Condensed Consolidated Balance Sheet				Derivatives Not Offset in the Condensed Consolidated Balance Sheet (1)				Net Amount
			(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 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:
		June 30, 2014
		Level 1				Level 2				Level 3				Total
		(Dollars in millions)
	Investments in debt and equity securities	$	27.2			$	36.5			$	—			$	63.7
	Commodity swaps and options	—				15.8				—				15.8
	Foreign currency cash flow hedge contracts	—				(109.6		)		—				(109.6		)
	Total net financial assets (liabilities)	$	27.2			$	(57.3	)		$	—			$	(30.1	)
		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 swaps and options	—				5.1				—				5.1
	Foreign currency cash flow hedge 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:
		June 30, 2014								December 31, 2013
		Carrying				Estimated				Carrying				Estimated
		Amount				Fair Value				Amount				Fair Value
		(Dollars in millions)
	Long-term debt	$	5,994.00			$	6,055.20			$	6,002.40			$	6,167.50

Coal_Trading_Tables

Coal Trading (Tables) (Coal Trading [Member])	6 Months Ended
	Jun. 30, 2014
Coal Trading [Member]	'
Coal Trading [Line Items]	'
Trading revenue by type of instrument	'
	Trading revenues recognized during the three and six months ended June 30, 2014 and 2013 were as follows:
			Three Months Ended								Six Months Ended
			June 30,								June 30,
	Trading Revenues by Type of Instrument		2014				2013				2014				2013
			(Dollars in millions)
	Commodity futures, swaps and options		$	22.7			$	34.9			$	58.3			$	85.9
	Physical commodity purchase/sale contracts		(12.4		)		(38.3		)		(27.0		)		(63.4		)
	Total trading revenues		$	10.3			$	(3.4	)		$	31.3			$	22.5
Fair value of assets and liabilities from coal trading activities and related balance sheet offsetting	'
	The fair value of assets and liabilities from coal trading activities presented on a gross and net basis as of June 30, 2014 and December 31, 2013 is set forth below:
	Affected line item in the condensed consolidated balance sheets		Gross Amounts of Recognized Assets (Liabilities)				Gross Amounts Offset in the Condensed Consolidated Balance Sheets				Variation margin (held) posted (1)				Net Amounts of Assets (Liabilities) Presented in the Condensed Consolidated Balance Sheets
			(Dollars in millions)
			Fair Value as of June 30, 2014
	Assets from coal trading activities, net		$	430.2			$	(345.4	)		$	(34.0	)		$	50.8
	Liabilities from coal trading activities, net		(359.8		)		345.4				—				(14.4		)
	Total, Net		$	70.4			$	—			$	(34.0	)		$	36.4
			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)	Approximately $15 million and $42 million of the net variation margin held at June 30, 2014 and December 31, 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 June 30, 2014 and December 31, 2013:
		June 30, 2014
		Level 1				Level 2				Level 3				Total
		(Dollars in millions)
	Commodity futures, swaps and options	$	—			$	37.7			$	—			$	37.7
	Physical commodity purchase/sale contracts	—				(3.9		)		2.6				(1.3		)
	Total net financial assets	$	—			$	33.8			$	2.6			$	36.4
		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 June 30, 2014:
			Range						Weighted
	Input		Low			High			Average
	Quality adjustments		1	%		8	%		7	%
	Location differentials		17	%		64	%		37	%
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:
			Three Months Ended								Six Months Ended
			June 30,								June 30,
			2014				2013				2014				2013
			(Dollars in millions)
	Beginning of period		$	2.2			$	1.4			$	2.1			$	5.2
	Total net gains (losses) realized/unrealized:
	Included in earnings		1.5				(0.3		)		3.3				(4.4		)
	Settlements		(1.1		)		0.2				(2.8		)		0.5
	End of period		$	2.6			$	1.3			$	2.6			$	1.3
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:
			Three Months Ended								Six Months Ended
			June 30,								June 30,
			2014				2013				2014				2013
			(Dollars in millions)
	Changes in net unrealized gains (losses) (1)		$	1.2			$	(2.8	)		$	0.3			$	(2.6	)
	(1)	Within the unaudited condensed consolidated statements of operations and unaudited condensed 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 June 30, 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
	2014		68	%
	2015		19	%
	2016		10	%
	2017		2	%
	2018		1	%
			100	%

Financing_Receivables_Tables

Financing Receivables (Tables)	6 Months Ended
	Jun. 30, 2014
Financing Receivables [Abstract]	'
Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block]	'
	The Company's total financing receivables as of June 30, 2014 and December 31, 2013 consisted of the following:
	Balance Sheet Classification	June 30, 2014		December 31, 2013
		(Dollars in millions)
	Accounts receivable, net	$	0.1	$	0.1
	Investments and other assets	378.2		351.7
	Total financing receivables	$	378.3	$	351.8

Property_Plant_Equipment_and_M1

Property, Plant, Equipment and Mine Development (Tables)	6 Months Ended
	Jun. 30, 2014
Property, Plant, Equipment and Mine Development, Net [Line Items]	'
Property, Plant and Equipment [Table Text Block]	'
	Property, plant, equipment and mine development, net, as of June 30, 2014 and December 31, 2013 consisted of the following:
		30-Jun-14			December 31, 2013
		(Dollars in millions)
	Land and coal interests	$	10,957.60		$	11,024.10
	Buildings and improvements	1,553.20			1,525.40
	Machinery and equipment	2,663.30			2,777.50
	Less: Accumulated depreciation, depletion and amortization	(4,473.6		)	(4,244.5		)
	Total, net	$	10,700.50		$	11,082.50

Longterm_Debt_Tables

Long-term Debt (Tables)	6 Months Ended
	Jun. 30, 2014
Debt Disclosure [Abstract]	'
Schedule of Long-term Debt Instruments [Table Text Block]	'
	The Company’s total indebtedness as of June 30, 2014 and December 31, 2013 consisted of the following:
		June 30, 2014		December 31, 2013
		(Dollars in millions)
	2013 Term Loan Facility due September 2020	$	1,180.30	$	1,185.40
	7.375% Senior Notes due November 2016	650		650
	6.00% Senior Notes due November 2018	1,518.80		1,518.80
	6.50% Senior Notes due September 2020	650		650
	6.25% Senior Notes due November 2021	1,339.60		1,339.60
	7.875% Senior Notes due November 2026	247.6		247.5
	Convertible Junior Subordinated Debentures due December 2066	381		379.7
	Capital lease obligations	26.4		30.5
	Other	0.3		0.9
	Total long-term debt	$	5,994.00	$	6,002.40

Pension_and_Postretirement_Ben1

Pension and Postretirement Benefit Costs (Tables)	6 Months Ended
	Jun. 30, 2014
Pension Plan, Defined Benefit [Member]	'
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]	'
Schedule of Net Benefit Costs [Table Text Block]	'
	Net periodic pension cost included the following components:
		Three Months Ended June 30,						Six Months Ended June 30,
		2014			2013			2014			2013
		(Dollars in millions)
	Service cost for benefits earned	$	0.5		$	0.5		$	1		$	1.1
	Interest cost on projected benefit obligation	11.3			10.5			22.7			21.1
	Expected return on plan assets	(13.5		)	(14.8		)	(27.1		)	(29.7		)
	Amortization of prior service cost and net actuarial loss	7.8			16.7			15.7			33.3
	Net periodic pension cost	$	6.1		$	12.9		$	12.3		$	25.8
Other Postretirement Benefit Plan, Defined Benefit [Member]	'
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]	'
Schedule of Net Benefit Costs [Table Text Block]	'
	Net periodic postretirement benefit cost included the following components:
		Three Months Ended June 30,						Six Months Ended June 30,
		2014			2013			2014			2013
		(Dollars in millions)
	Service cost for benefits earned	$	3		$	3.9		$	6.1		$	7.8
	Interest cost on accumulated postretirement benefit obligation	9.1			10.4			18.2			20.9
	Amortization of prior service cost and net actuarial loss, and special termination benefits	4			7.1			7.9			12.7
	Net periodic postretirement benefit cost	$	16.1		$	21.4		$	32.2		$	41.4

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Loss Accumulated Other Comprehensive Loss (Tables)	6 Months Ended
	Jun. 30, 2014
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]	'
After-tax components of comprehensive Income (loss)	'
	The following table below sets forth the after-tax components of accumulated other comprehensive loss and changes thereto recorded during the six months ended June 30, 2014:
		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, 2013	$	(70.5	)		$	(205.8	)		$	12		$	(155.7	)	$	0.8		$	(419.2	)
	Net change in fair value	—				—				—			184.1			(1.3		)	182.8
	Reclassification from other comprehensive income to earnings	—				12.7				0.9			(5.0		)	—			8.6
	Current period change	26.4				—				(17.4		)	—			—			9
	June 30, 2014	$	(44.1	)		$	(193.1	)		$	(4.5	)	$	23.4		$	(0.5	)	$	(218.8	)
Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]	'
	The following tables provide additional information regarding items reclassified out of "Accumulated other comprehensive loss" into earnings during the three and six months ended June 30, 2014 and 2013:
			Amount reclassified from accumulated other comprehensive loss (1)
	Details about accumulated other comprehensive income (loss) components		Three Months Ended June 30, 2014				Three Months Ended June 30, 2013				Affected line item in the condensed consolidated statement of operations
			(Dollars in millions)
	Net actuarial loss associated with postretirement plans and workers compensation obligations:
	Postretirement health care and life insurance benefits		$	(3.6	)		$	(6.0	)		Operating costs and expenses
	Defined benefit pension plans		(6.2		)		(13.6		)		Operating costs and expenses
	Defined benefit pension plans		(1.3		)		(2.8		)		Selling and administrative expenses
	Insignificant items		1				(0.3		)
			(10.1		)		(22.7		)		Total before income taxes
			3.8				8.4				Income tax benefit
			$	(6.3	)		$	(14.3	)		Total after income taxes
	Prior service cost associated with postretirement plans:
	Postretirement health care and life insurance benefits		$	(0.4	)		$	0.4			Operating costs and expenses
	Defined benefit pension plans		(0.3		)		(0.3		)		Operating costs and expenses
			(0.7		)		0.1				Total before income taxes
			0.2				—				Income tax benefit
			$	(0.5	)		$	0.1			Total after income taxes
	Cash flow hedges:
	Foreign currency cash flow hedge contracts		$	6.3			$	62.1			Operating costs and expenses
	Fuel and explosives commodity swaps		0.9				0.6				Operating costs and expenses
	Coal trading commodity futures, swaps and options		3				0.4				Other revenues
	Insignificant items		—				(0.2		)
			10.2				62.9				Total before income taxes
			0.4				(24.6		)		Income tax benefit (provision)
			$	10.6			$	38.3			Total after income taxes
	Available-for-sale securities:
	Equity securities		$	—			$	(21.5	)		Asset impairment
			—				7.9				Income tax benefit
			$	—			$	(13.6	)		Total after income taxes
	(1)	Presented as gains (losses) in the unaudited condensed consolidated statements of operations.
			Amount reclassified from accumulated other comprehensive loss (1)
	Details about accumulated other comprehensive income (loss) components		Six Months Ended June 30, 2014				Six Months Ended June 30, 2013				Affected line item in the condensed consolidated statement of operations
			(Dollars in millions)
	Net actuarial loss associated with postretirement plans and workers compensation obligations:
	Postretirement health care and life insurance benefits		$	(7.2	)		$	(12.0	)		Operating costs and expenses
	Defined benefit pension plans		(12.4		)		(27.2		)		Operating costs and expenses
	Defined benefit pension plans		(2.7		)		(5.6		)		Selling and administrative expenses
	Insignificant items		2				(0.6		)
			(20.3		)		(45.4		)		Total before income taxes
			7.6				16.8				Income tax benefit
			$	(12.7	)		$	(28.6	)		Total after income taxes
	Prior service cost associated with postretirement plans:
	Postretirement health care and life insurance benefits		$	(0.7	)		$	0.8			Operating costs and expenses
	Defined benefit pension plans		(0.6		)		(0.5		)		Operating costs and expenses
			(1.3		)		0.3				Total before income taxes
			0.4				(0.1		)		Income tax benefit (provision)
			$	(0.9	)		$	0.2			Total after income taxes
	Cash flow hedges:
	Foreign currency cash flow hedge contracts		$	(12.5	)		$	147.2			Operating costs and expenses
	Fuel and explosives commodity swaps		(1.5		)		7.5				Operating costs and expenses
	Coal trading commodity futures, swaps and options		20.8				25.7				Other revenues
	Insignificant items		(0.1		)		(0.3		)
			6.7				180.1				Total before income taxes
			(1.7		)		(64.7		)		Income tax provision
			$	5			$	115.4			Total after income taxes
	Available-for-sale securities:
	Debt securities		$	—			$	0.1			Interest income
	Equity securities		—				(21.5		)		Asset impairment
			—				(21.4		)		Total before income taxes
			—				7.9				Income tax benefit
			$	—			$	(13.5	)		Total after income taxes
	(1)	Presented as gains (losses) in the unaudited condensed consolidated statements of operations.

Earnings_per_Share_EPS_Tables

Earnings per Share (EPS) (Tables)	6 Months Ended
	Jun. 30, 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:
			Three Months Ended June 30,						Six Months Ended June 30,
			2014			2013			2014			2013
			(Dollars in millions, except per share data)
	EPS numerator:
	(Loss) income from continuing operations, net of income taxes		$	(72.0	)	$	101.4		$	(116.3	)	$	91.1
	Less: Net income (loss) attributable to noncontrolling interests		2.1			(3.2		)	6.5			0.8
	(Loss) income from continuing operations attributable to common stockholders, before allocation of earnings to participating securities		(74.1		)	104.6			(122.8		)	90.3
	Less: Earnings allocated to participating securities		0.3			0.7			0.5			0.2
	(Loss) income from continuing operations attributable to common stockholders, after allocation of earnings to participating securities (1)		(74.4		)	103.9			(123.3		)	90.1
	Income (loss) from discontinued operations, net of income taxes		0.8			(14.3		)	1			(23.4		)
	Less: Loss from discontinued operations allocated to participating securities		—			(0.1		)	—			(0.2		)
	Income (loss) from discontinued operations attributable to common stockholders, after allocation of earnings to participating securities (1)		0.8			(14.2		)	1			(23.2		)
	Net (loss) income attributable to common stockholders, after earnings allocated to participating securities (1)		$	(73.6	)	$	89.7		$	(122.3	)	$	66.9
	EPS denominator:
	Weighted average shares outstanding — basic		268			266.9			267.9			266.9
	Impact of dilutive securities		—			0.6			—			0.5
	Weighted average shares outstanding — diluted		268			267.5			267.9			267.4
	Basic EPS attributable to common stockholders:
	(Loss) income from continuing operations		$	(0.28	)	$	0.39		$	(0.46	)	$	0.34
	Income (loss) from discontinued operations		0.01			(0.06		)	—			(0.09		)
	Net (loss) income attributable to common stockholders		$	(0.27	)	$	0.33		$	(0.46	)	$	0.25
	Diluted EPS attributable to common stockholders:
	(Loss) income from continuing operations		$	(0.28	)	$	0.39		$	(0.46	)	$	0.33
	Income (loss) from discontinued operations		0.01			(0.06		)	—			(0.08		)
	Net (loss) income attributable to common stockholders		$	(0.27	)	$	0.33		$	(0.46	)	$	0.25
	-1	The reallocation adjustment for participating securities to arrive at the numerator used to calculate diluted EPS was less than $0.1 million for the three and six months ended June 30, 2013.

Financial_Instruments_and_Guar1

Financial Instruments and Guarantees with Off-Balance-Sheet Risk (Tables)	6 Months Ended
	Jun. 30, 2014
Financial Instruments And Guarantees With Off Balance Sheet Risk Disclosure [Abstract]	'
Financial instruments with off-balance sheet risk:	'
	As of June 30, 2014, the Company had the following financial instruments with off-balance sheet risk:
		Reclamation		Lease		Workers’		Other(1)		Total
		Obligations		Obligations		Compensation
						Obligations
		(Dollars in millions)
	Self bonding	$	1,366.30	$	—	$	—	$	—	$	1,366.30
	Surety bonds	328.1		105.1		98.1		11		542.3
	Bank guarantees	276.5		—		—		140.8		417.3
	Letters of credit	17.6		—		34.1		85.6		137.3
		$	1,988.50	$	105.1	$	132.2	$	237.4	$	2,463.20
	(1)	Other includes the $79.7 million in letters of credit related to Dominion Terminal Associates and TXU Europe Limited described below and an additional $157.7 million in bank guarantees, letters of credit and surety bonds related to collateral for road maintenance, performance guarantees and other operations.

Segment_Information_Tables

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2014
Segment Reporting [Abstract]	'
Reportable segment results	'
	Reportable segment results were as follows:
		Three Months Ended June 30,						Six Months Ended June 30,
		2014			2013			2014			2013
		(Dollars in millions)
	Revenues:
	Australian Mining	$	707.4		$	744.8		$	1,319.20		$	1,482.80
	Western U.S. Mining	726.6			640.9			1,408.60			1,281.00
	Midwestern U.S. Mining	304.6			330			607.6			666.7
	Trading and Brokerage	10.3			(3.4		)	31.3			22.5
	Corporate and Other	9.1			13			18.1			20.3
	Total	$	1,758.00		$	1,725.30		$	3,384.80		$	3,473.30
	Adjusted EBITDA:
	Australian Mining	$	12.2		$	112.5		$	14		$	212.9
	Western U.S. Mining	222			154.9			395.9			315.4
	Midwestern U.S. Mining	69.9			106.8			148.6			219.1
	Trading and Brokerage	6.3			(41.0		)	4.4			(25.0		)
	Corporate and Other	(97.3		)	(78.9		)	(172.9		)	(188.0		)
	Total	$	213.1		$	254.3		$	390		$	534.4
Reconciliation of Adjusted EBITDA to consolidated (loss) income from continuing operations, net of income taxes	'
	A reconciliation of Adjusted EBITDA to consolidated (loss) income from continuing operations, net of income taxes follows:
		Three Months Ended June 30,						Six Months Ended June 30,
		2014			2013			2014			2013
		(Dollars in millions)
	Adjusted EBITDA	$	213.1		$	254.3		$	390		$	534.4
	Depreciation, depletion and amortization	(163.1		)	(185.7		)	(320.3		)	(356.4		)
	Asset impairment	—			(21.5		)	—			(21.5		)
	Amortization of basis difference related to equity affiliates	(1.3		)	(2.4		)	(2.5		)	(4.0		)
	Asset retirement obligation expenses	(15.9		)	(18.3		)	(31.5		)	(37.3		)
	Interest expense	(105.2		)	(110.8		)	(208.5		)	(212.1		)
	Interest income	4.4			1.1			8			7
	Income tax (provision) benefit	(4.0		)	184.7			48.5			181
	(Loss) income from continuing operations, net of income taxes	$	(72.0	)	$	101.4		$	(116.3	)	$	91.1

Supplemental_GuarantorNonGuara1

Supplemental Guarantor/Non-Guarantor Financial Information (Tables)	6 Months Ended
	Jun. 30, 2014																Jun. 30, 2013
Supplemental Consolidated Statements Of Operations [Table Text Block]	'																'
	Unaudited Supplemental Condensed Consolidating Statements of Operations																Unaudited Supplemental Condensed Consolidating Statements of Operations
		Three Months Ended June 30, 2014																Six Months Ended June 30, 2013
		Parent			Guarantor			Non-Guarantor			Eliminations			Consolidated				Parent			Guarantor			Non-Guarantor			Eliminations			Consolidated
		Company			Subsidiaries			Subsidiaries										Company			Subsidiaries			Subsidiaries
		(Dollars in millions)																(Dollars in millions)
	Total revenues	$	—		$	1,005.00		$	774.9		$	(21.9	)	$	1,758.00		Total revenues	$	—		$	1,987.10		$	1,615.00		$	(128.8	)	$	3,473.30
	Costs and expenses																Costs and expenses
	Operating costs and expenses (exclusive of items shown separately below)	(7.3		)	741.2			755.6			(21.9		)	1,467.60			Operating costs and expenses (exclusive of items shown separately below)	(154.5		)	1,523.90			1,586.00			(128.8		)	2,826.60
	Depreciation, depletion and amortization	—			76.2			86.9			—			163.1			Depreciation, depletion and amortization	—			165.1			191.3			—			356.4
	Asset retirement obligation expenses	—			7			8.9			—			15.9			Asset retirement obligation expenses	—			21.8			15.5			—			37.3
	Selling and administrative expenses	11			42.8			5.4			—			59.2			Selling and administrative expenses	23.8			91.7			13.6			—			129.1
	Other operating (income) loss:																Other operating (income) loss:
	Net (gain) loss on disposal or exchange of assets	—			(2.3		)	0.1			—			(2.2		)	Net gain on disposal or exchange of assets	—			(45.8		)	—			—			(45.8		)
	Loss (income) from equity affiliates and investment in subsidiaries	4.4			2.1			19.5			(4.4		)	21.6			Asset impairment	21.5			—			—			—			21.5
	Interest expense	107.2			1.7			1.7			(5.4		)	105.2			(Income) loss from equity affiliates and investment in subsidiaries	(89.6		)	8.4			24.6			89.6			33
	Interest income	(0.1		)	(2.1		)	(7.6		)	5.4			(4.4		)	Interest expense	203.2			11			205.9			(208.0		)	212.1
	(Loss) income from continuing operations before income taxes	(115.2		)	138.4			(95.6		)	4.4			(68.0		)	Interest income	(68.2		)	(125.4		)	(21.4		)	208			(7.0		)
	Income tax (benefit) provision	(41.0		)	41			4			—			4			Unrealized loss (gain) on derivatives	—			461.6			(461.6		)	—			—
	(Loss) income from continuing operations, net of income taxes	(74.2		)	97.4			(99.6		)	4.4			(72.0		)	Income (loss) from continuing operations before income taxes	63.8			(125.2		)	61.1			(89.6		)	(89.9		)
	Income (loss) from discontinued operations, net of income taxes	0.9			(0.5		)	0.4			—			0.8			Income tax benefit	(9.5		)	(85.2		)	(86.3		)	—			(181.0		)
	Net (loss) income	(73.3		)	96.9			(99.2		)	4.4			(71.2		)	Income (loss) from continuing operations, net of income taxes	73.3			(40.0		)	147.4			(89.6		)	91.1
	Less: Net income attributable to noncontrolling interests	—			—			2.1			—			2.1			Loss from discontinued operations, net of income taxes	(6.4		)	(2.5		)	(14.5		)	—			(23.4		)
	Net (loss) income attributable to common stockholders	$	(73.3	)	$	96.9		$	(101.3	)	$	4.4		$	(73.3	)	Net income (loss)	66.9			(42.5		)	132.9			(89.6		)	67.7
	Unaudited Supplemental Condensed Consolidating Statements of Operations																Less: Net income attributable to noncontrolling interests	—			—			0.8			—			0.8
																	Net income (loss) attributable to common stockholders	$	66.9		$	(42.5	)	$	132.1		$	(89.6	)	$	66.9
		Six Months Ended June 30, 2014
		Parent			Guarantor			Non-Guarantor			Eliminations			Consolidated
		Company			Subsidiaries			Subsidiaries
		(Dollars in millions)
	Total revenues	$	—		$	1,981.40		$	1,446.20		$	(42.8	)	$	3,384.80
	Costs and expenses
	Operating costs and expenses (exclusive of items shown separately below)	13.9			1,468.00			1,423.30			(42.8		)	2,862.40
	Depreciation, depletion and amortization	—			153.4			166.9			—			320.3
	Asset retirement obligation expenses	—			15.6			15.9			—			31.5
	Selling and administrative expenses	24.6			84.1			10			—			118.7
	Other operating (income) loss:
	Net gain on disposal or exchange of assets	—			(11.9		)	(0.1		)	—			(12.0		)
	(Income) loss from equity affiliates and investment in subsidiaries	(35.2		)	2.7			25.5			35.2			28.2
	Interest expense	212.9			3.3			3.1			(10.8		)	208.5
	Interest income	(0.2		)	(4.5		)	(14.1		)	10.8			(8.0		)
	(Loss) income from continuing operations before income taxes	(216.0		)	270.7			(184.3		)	(35.2		)	(164.8		)
	Income tax (benefit) provision	(93.0		)	65.8			(21.3		)	—			(48.5		)
	(Loss) income from continuing operations, net of income taxes	(123.0		)	204.9			(163.0		)	(35.2		)	(116.3		)
	Income (loss) from discontinued operations, net of income taxes	1.2			(1.2		)	1			—			1
	Net (loss) income	(121.8		)	203.7			(162.0		)	(35.2		)	(115.3		)
	Less: Net income attributable to noncontrolling interests	—			—			6.5			—			6.5
	Net (loss) income attributable to common stockholders	$	(121.8	)	$	203.7		$	(168.5	)	$	(35.2	)	$	(121.8	)
	Unaudited Supplemental Condensed Consolidating Statements of Operations
		Three Months Ended June 30, 2013
		Parent			Guarantor			Non-Guarantor			Eliminations			Consolidated
		Company			Subsidiaries			Subsidiaries
		(Dollars in millions)
	Total revenues	$	—		$	972.5		$	818.8		$	(66.0	)	$	1,725.30
	Costs and expenses
	Operating costs and expenses (exclusive of items shown separately below)	(62.8		)	823			743			(66.0		)	1,437.20
	Depreciation, depletion and amortization	—			85.5			100.2			—			185.7
	Asset retirement obligation expenses	—			10.2			8.1			—			18.3
	Selling and administrative expenses	14.6			44.3			5.1			—			64
	Other operating (income) loss:
	Net gain on disposal or exchange of assets	—			(43.0		)	(0.2		)	—			(43.2		)
	Asset impairment	21.5			—			—			—			21.5
	(Income) loss from equity affiliates and investment in subsidiaries	(174.4		)	4.5			10.9			174.4			15.4
	Interest expense	101.3			8.7			95.4			(94.6		)	110.8
Interest income	(0.1		)	(90.5		)	(5.1		)	94.6			(1.1		)
Unrealized loss (gain) on derivatives	—			502.6			(502.6		)	—			—
Income (loss) from continuing operations before income taxes	99.9			(372.8		)	364			(174.4		)	(83.3		)
Income tax provision (benefit)	5.8			(193.1		)	2.6			—			(184.7		)
Income (loss) from continuing operations, net of income taxes	94.1			(179.7		)	361.4			(174.4		)	101.4
Loss from discontinued operations, net of income taxes	(3.8		)	(1.0		)	(9.5		)	—			(14.3		)
Net income (loss)	90.3			(180.7		)	351.9			(174.4		)	87.1
Less: Net loss attributable to noncontrolling interests	—			—			(3.2		)	—			(3.2		)
Net income (loss) attributable to common stockholders	$	90.3		$	(180.7	)	$	355.1		$	(174.4	)	$	90.3
SupplementalCondensedConsolidatingStatementsOfComprehensiveIncomeLoss [Table Text Block]	'																'
	Unaudited Supplemental Condensed Consolidating Statements of Comprehensive Income
		Three Months Ended June 30, 2013
		Parent			Guarantor			Non-Guarantor			Eliminations			Consolidated
		Company			Subsidiaries			Subsidiaries
		(Dollars in millions)
	Net income (loss)	$	90.3		$	(180.7	)	$	351.9		$	(174.4	)	$	87.1
	Other comprehensive (loss) income, net of income taxes	(431.6		)	51			(49.9		)	(1.1		)	(431.6		)
	Comprehensive (loss) income	(341.3		)	(129.7		)	302			(175.5		)	(344.5		)
	Less: Comprehensive loss attributable to noncontrolling interests	—			—			(3.2		)	—			(3.2		)
	Comprehensive (loss) income attributable to common stockholders	$	(341.3	)	$	(129.7	)	$	305.2		$	(175.5	)	$	(341.3	)
	Unaudited Supplemental Condensed Consolidating Statements of Comprehensive Income
		Six Months Ended June 30, 2014
		Parent			Guarantor			Non-Guarantor			Eliminations			Consolidated
		Company			Subsidiaries			Subsidiaries
		(Dollars in millions)
	Net (loss) income	$	(121.8	)	$	203.7		$	(162.0	)	$	(35.2	)	$	(115.3	)
	Other comprehensive income (loss), net of income taxes	200.4			2.4			(15.9		)	13.5			200.4
	Comprehensive income (loss)	78.6			206.1			(177.9		)	(21.7		)	85.1
	Less: Comprehensive income attributable to noncontrolling interests	—			—			6.5			—			6.5
	Comprehensive income (loss) attributable to common stockholders	$	78.6		$	206.1		$	(184.4	)	$	(21.7	)	$	78.6
	Unaudited Supplemental Condensed Consolidating Statements of Comprehensive Income
		Three Months Ended June 30, 2014
		Parent			Guarantor			Non-Guarantor			Eliminations			Consolidated
		Company			Subsidiaries			Subsidiaries
		(Dollars in millions)
	Net (loss) income	$	(73.3	)	$	96.9		$	(99.2	)	$	4.4		$	(71.2	)
	Other comprehensive income (loss), net of income taxes	74.5			(7.5		)	2.6			4.9			74.5
	Comprehensive income (loss)	1.2			89.4			(96.6		)	9.3			3.3
	Less: Comprehensive income attributable to noncontrolling interests	—			—			2.1			—			2.1
	Comprehensive income (loss) attributable to common stockholders	$	1.2		$	89.4		$	(98.7	)	$	9.3		$	1.2
	Unaudited Supplemental Condensed Consolidating Statements of Comprehensive Income
		Six Months Ended June 30, 2013
		Parent			Guarantor			Non-Guarantor			Eliminations			Consolidated
		Company			Subsidiaries			Subsidiaries
		(Dollars in millions)
	Net income (loss)	$	66.9		$	(42.5	)	$	132.9		$	(89.6	)	$	67.7
	Other comprehensive (loss) income, net of income taxes	(431.0		)	28.5			(64.1		)	35.6			(431.0		)
	Comprehensive (loss) income	(364.1		)	(14.0		)	68.8			(54.0		)	(363.3		)
	Less: Comprehensive income attributable to noncontrolling interests	—			—			0.8			—			0.8
	Comprehensive (loss) income attributable to common stockholders	$	(364.1	)	$	(14.0	)	$	68		$	(54.0	)	$	(364.1	)
Supplemental Consolidated Balance Sheets [Table Text Block]	'																'
	Unaudited Supplemental Condensed Consolidating Balance Sheets
		June 30, 2014
		Parent			Guarantor			Non-Guarantor			Reclassifications/			Consolidated
		Company			Subsidiaries			Subsidiaries			Eliminations
		(Dollars in millions)
	Assets
	Current assets
	Cash and cash equivalents	$	323.6		$	0.2		$	174.6		$	—		$	498.4
	Accounts receivable, net	0.3			—			447.1			(0.3		)	447.1
	Receivables from affiliates, net	369.2			—			—			(369.2		)	—
	Inventories	—			217.6			330.8			—			548.4
	Assets from coal trading activities, net	—			46.1			4.7			—			50.8
	Deferred income taxes	24			36			7.2			—			67.2
	Other current assets	11.1			17.2			237.6			—			265.9
	Total current assets	728.2			317.1			1,202.00			(369.5		)	1,877.80
	Property, plant, equipment and mine development, net	—			4,904.60			5,795.90			—			10,700.50
	Deferred income taxes	—			—			79.4			2.7			82.1
	Investments and other assets	10,704.60			8.5			742.9			(10,424.2		)	1,031.80
	Notes receivable from affiliates, net	—			1,546.80			—			(1,546.8		)	—
	Total assets	$	11,432.80		$	6,777.00		$	7,820.20		$	(12,337.8	)	$	13,692.20
	Liabilities and Stockholders’ Equity
	Current liabilities
	Current maturities of long-term debt	$	12		$	0.1		$	8.7		$	—		$	20.8
	Payables to affiliates, net	—			296.5			72.7			(369.2		)	—
	Deferred income taxes	—			—			7.5			—			7.5
	Liabilities from coal trading activities, net	—			4.8			9.6			—			14.4
	Accounts payable and accrued expenses	194.2			580.9			687.2			(0.3		)	1,462.00
	Total current liabilities	206.2			882.3			785.7			(369.5		)	1,504.70
	Long-term debt, less current maturities	5,955.30			6.4			11.5			—			5,973.20
	Deferred income taxes	22.4			34.4			—			2.7			59.5
	Notes payable to affiliates, net	1,078.10			—			468.7			(1,546.8		)	—
	Other noncurrent liabilities	210			1,555.00			385.4			—			2,150.40
	Total liabilities	7,472.00			2,478.10			1,651.30			(1,913.6		)	9,687.80
	Peabody Energy Corporation stockholders’ equity	3,960.80			4,298.90			6,125.30			(10,424.2		)	3,960.80
	Noncontrolling interests	—			—			43.6			—			43.6
	Total stockholders’ equity	3,960.80			4,298.90			6,168.90			(10,424.2		)	4,004.40
	Total liabilities and stockholders’ equity	$	11,432.80		$	6,777.00		$	7,820.20		$	(12,337.8	)	$	13,692.20
	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	—			1,478.60			—			(1,478.6		)	—
	Total assets	$	11,816.30		$	6,960.80		$	8,050.70		$	(12,694.4	)	$	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			577.7			802.5			(2.5		)	1,737.70
Total current liabilities	373.9			588.4			896.6			(83.4		)	1,775.50
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	1,078.20			—			400.4			(1,478.6		)	—
Other noncurrent liabilities	496.4			1,521.80			380.2			—			2,398.40
Total liabilities	7,907.60			2,172.60			1,683.80			(1,578.5		)	10,185.50
Peabody Energy Corporation 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		$	6,960.80		$	8,050.70		$	(12,694.4	)	$	14,133.40
Supplemental Consolidated Statements Of Cash Flows [Table Text Block]	'																'
	Unaudited Supplemental Condensed Consolidating Statements of Cash Flows
		Six Months Ended June 30, 2013
		Parent			Guarantor			Non-Guarantor			Consolidated
		Company			Subsidiaries			Subsidiaries
		(Dollars in millions)
	Cash Flows From Operating Activities
	Net cash provided by (used in) continuing operations	$	114.5		$	496.5		$	(245.1	)	$	365.9
	Net cash (used in) provided by discontinued operations	(8.1		)	0.5			(26.9		)	(34.5		)
	Net cash provided by (used in) operating activities	106.4			497			(272.0		)	331.4
	Cash Flows From Investing Activities
	Additions to property, plant, equipment and mine development	—			(45.1		)	(121.4		)	(166.5		)
	Changes in accrued expenses related to capital expenditures	—			(2.4		)	(100.2		)	(102.6		)
	Proceeds from disposal of assets, net of notes receivable	—			42.1			81.8			123.9
	Purchases of debt securities	—			—			(9.7		)	(9.7		)
	Proceeds from sales and maturities of debt securities	—			—			17			17
	Proceeds from the maturity of short-term investments	—			—			4.8			4.8
	Contributions to joint ventures	—			—			(323.8		)	(323.8		)
	Distributions from joint ventures	—			—			372.1			372.1
	Advances to related parties	—			—			(35.7		)	(35.7		)
	Repayments of loans from related parties	—			—			18.2			18.2
	Other, net	—			(3.4		)	(0.2		)	(3.6		)
	Net cash used in continuing operations	—			(8.8		)	(97.1		)	(105.9		)
	Net cash used in discontinued operations	—			—			(0.3		)	(0.3		)
	Net cash used in investing activities	—			(8.8		)	(97.4		)	(106.2		)
	Cash Flows From Financing Activities
	Repayments of long-term debt	(167.0		)	(0.1		)	(48.5		)	(215.6		)
	Dividends paid	(45.9		)	—			—			(45.9		)
	Other, net	0.9			(5.2		)	(0.3		)	(4.6		)
	Transactions with affiliates, net	169.8			(483.0		)	313.2			—
	Net cash (used in) provided by financing activities	(42.2		)	(488.3		)	264.4			(266.1		)
	Net change in cash and cash equivalents	64.2			(0.1		)	(105.0		)	(40.9		)
	Cash and cash equivalents at beginning of period	269.6			0.3			288.9			558.8
	Cash and cash equivalents at end of period	$	333.8		$	0.2		$	183.9		$	517.9
	Unaudited Supplemental Condensed Consolidating Statements of Cash Flows
		Six Months Ended June 30, 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	$	(112.4	)	$	330.3		$	(60.8	)	$	157.1
	Net cash used in discontinued operations	(72.9		)	(1.4		)	(7.5		)	(81.8		)
	Net cash (used in) provided by operating activities	(185.3		)	328.9			(68.3		)	75.3
	Cash Flows From Investing Activities
	Additions to property, plant, equipment and mine development	—			(32.1		)	(32.6		)	(64.7		)
	Changes in accrued expenses related to capital expenditures	—			(1.3		)	(16.2		)	(17.5		)
	Proceeds from disposal of assets, net of notes receivable	—			50.9			88.3			139.2
	Purchases of debt securities	—			—			(4.2		)	(4.2		)
	Proceeds from sales and maturities of debt securities	—			—			5			5
	Contributions to joint ventures	—			—			(271.3		)	(271.3		)
	Distributions from joint ventures	—			—			269			269
	Advances to related parties	—			—			(12.3		)	(12.3		)
	Repayments of loans from related parties	—			—			2.2			2.2
	Other, net	—			(1.7		)	(0.3		)	(2.0		)
	Net cash provided by continuing operations	—			15.8			27.6			43.4
	Net cash provided by discontinued operations	—			—			5			5
	Net cash provided by investing activities	—			15.8			32.6			48.4
	Cash Flows From Financing Activities
	Repayments of long-term debt	(6.0		)	—			(4.4		)	(10.4		)
	Payment of debt issuance costs	(10.1		)	—			—			(10.1		)
	Dividends paid	(46.1		)	—			—			(46.1		)
	Other, net	1			(1.7		)	(2.0		)	(2.7		)
	Transactions with affiliates, net	269.4			(343.1		)	73.7			—
	Net cash provided by (used in) financing activities	208.2			(344.8		)	67.3			(69.3		)
Net change in cash and cash equivalents	22.9			(0.1		)	31.6			54.4
Cash and cash equivalents at beginning of period	300.7			0.3			143			444
Cash and cash equivalents at end of period	$	323.6		$	0.2		$	174.6		$	498.4

Asset_Realization_Details

Asset Realization (Details) (USD $)	3 Months Ended	6 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2014	Dec. 31, 2013	Dec. 31, 2012
Asset Realization	'	'	'	'
Asset impairment charges	$0	$0	$528.30	$910.90
Asset realization risk	$227.40	$227.40	'	'

Discontinued_Operations_Detail

Discontinued Operations (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jan. 31, 2014	Dec. 31, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'	'	'
Income (loss) from discontinued operations before income taxes	$1.20	($16.10)	$1.10	($32.70)	'	'
Income tax provision (benefit)	0.4	-1.8	0.1	-9.3	'	'
Income (loss) from discontinued operations, net of income taxes	0.8	-14.3	1	-23.4	'	'
Total revenues associated with discontinued operations	0	35.6	0	67.7	'	'
Other current assets	2.4	'	2.4	'	'	38.6
Investments and other assets	20.8	'	20.8	'	'	47.4
Total assets classified as discontinued operations	23.2	'	23.2	'	'	86
Accounts payable and accrued expenses	42.3	'	42.3	'	'	127.8
Other noncurrent liabilities	86.7	'	86.7	'	'	90.2
Total liabilities classified as discontinued operations	129	'	129	'	'	218
Payment to Patriot based on the construct of the negotiated settlement	'	'	'	'	70	'
Asset retirement obligation	721.2	'	721.2	'	'	712.8
Proceeds from sale of property held-for-sale	70	'	70	'	'	'
Wilkie Creek [Member]	'	'	'	'	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'	'	'
Liability balance	29.3	'	29.3	'	'	36.6
Change in estimate	'	'	-0.2	'	'	'
Cash payments	'	'	-8.7	'	'	'
Foreign currency remeasurement expense	'	'	1.6	'	'	'
Asset retirement obligation	48	'	48	'	'	'
Wilkie Creek [Member] | Other Exit Costs [Domain]	'	'	'	'	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'	'	'
Liability balance	0.1	'	0.1	'	'	2.7
Change in estimate	'	'	-0.2	'	'	'
Cash payments	'	'	-2.4	'	'	'
Foreign currency remeasurement expense	'	'	0	'	'	'
Wilkie Creek [Member] | Accrued Take or Pay Liabilities [Domain]	'	'	'	'	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'	'	'
Liability balance	29.2	'	29.2	'	'	33.9
Change in estimate	'	'	0	'	'	'
Cash payments	'	'	-6.3	'	'	'
Foreign currency remeasurement expense	'	'	$1.60	'	'	'

Investments_Details

Investments (Details) (USD $)	6 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Investments in available-for-sale securities	'	'
Amortized Cost	$64.50	$65.70
Gross Unrealized Gains	0.1	1.4
Gross Unrealized Losses	-0.9	-0.1
Current [Member] | Federal government securities [Member]	'	'
Investments in available-for-sale securities	'	'
Amortized Cost	'	2.8
Gross Unrealized Gains	'	0
Gross Unrealized Losses	'	0
Fair Value	'	2.8
Current [Member] | U.S. corporate bonds [Member]	'	'
Investments in available-for-sale securities	'	'
Amortized Cost	8.9	2.4
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	8.9	2.4
Noncurrent [Member] | Marketable equity securities [Member]	'	'
Investments in available-for-sale securities	'	'
Amortized Cost	10.9	10.9
Gross Unrealized Gains	0	1.3
Gross Unrealized Losses	-0.9	0
Fair Value	10	12.2
Noncurrent [Member] | Federal government securities [Member]	'	'
Investments in available-for-sale securities	'	'
Amortized Cost	29.3	28.8
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	-0.1
Fair Value	29.3	28.7
Noncurrent [Member] | U.S. corporate bonds [Member]	'	'
Investments in available-for-sale securities	'	'
Amortized Cost	15.4	20.8
Gross Unrealized Gains	0.1	0.1
Gross Unrealized Losses	0	0
Fair Value	15.5	20.9
Fair Value, Measurements, Recurring [Member]	'	'
Investments in available-for-sale securities	'	'
Fair Value	$63.70	$67

Investments_Details_1

Investments (Details 1) (Debt Securities [Member], USD $)	Jun. 30, 2014
In Millions, unless otherwise specified
Debt Securities [Member]	'
Contractual maturities for available-for-sale securities	'
Due in one year or less, Cost	$8.90
Due in one to five years, Cost	44.7
Total Cost	53.6
Due in one year or less, Fair Value	8.9
Due in one to five years, Fair Value	44.8
Total Fair Value	$53.70

Investments_Details_Textuals

Investments (Details Textuals) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Investments [Abstract]	'	'	'	'	'
Long Term Investments Maturity Period Description	'	'	'Greater than one year	'Greater than one year	'
Short Term Investments Maturity Period Description	'	'	'Greater than three months and up to one year	'Greater than three months and up to one year	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'
Proceeds from sales and maturities of debt securities	$4.60	$4.10	$5	$17	'
Payments to acquire available-for-sale securities, debt	2.2	5.1	4.2	9.7	'
Proceeds from the maturity of short-term investments	'	4.8	0	4.8	'
Available-for-sale securities, gross realized gains less than	0.1	0.1	0.1	0.1	'
Other-than-temporary impairment losses on investments	0	21.5	0	21.5	'
Held-to-maturity investments	$0	'	$0	'	$0

Inventories_Details

Inventories (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Inventories [Line Items]	'	'
Materials and supplies	$166.30	$166.80
Raw coal	141.5	122.6
Saleable coal	240.6	217.3
Total	$548.40	$506.70

Inventories_Details_Textuals_D

Inventories Details Textuals (Details) (Reserve for materials and supplies [Member], USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Reserve for materials and supplies [Member]	'	'
Valuation and Qualifying Accounts Disclosure [Line Items]	'	'
Inventory reserves	$4.70	$7.40

Derivatives_and_Fair_Value_Mea3

Derivatives and Fair Value Measurements (Details)

6 Months Ended

12 Months Ended

In Millions, unless otherwise specified

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2015

Jun. 30, 2015

Jun. 30, 2015

Interest Rate Swap [Member]

Foreign Currency Forward Contract [Member]

Foreign Currency Forward Contract [Member]

Foreign Currency Forward Contract [Member]

Foreign Currency Forward Contract [Member]

Foreign Currency Forward Contract [Member]

Diesel fuel hedge contracts [Member]

Diesel fuel hedge contracts [Member]

Diesel fuel hedge contracts [Member]

Diesel fuel hedge contracts [Member]

Explosives Hedge Contracts Member

Explosives Hedge Contracts Member

Explosives Hedge Contracts Member

Explosives Hedge Contracts Member

Scenario, Forecast [Member]

Scenario, Forecast [Member]

Scenario, Forecast [Member]

USD ($)

USD ($)

AUD

Fair value hedge [Member]

Cash flow hedges [Member]

Economic hedge [Member]

USD ($)

Fair value hedge [Member]

Cash flow hedges [Member]

Economic hedge [Member]

USD ($)

Fair value hedge [Member]

Cash flow hedges [Member]

Economic hedge [Member]

Foreign Currency Forward Contract [Member]

Diesel fuel hedge contracts [Member]

Explosives Hedge Contracts Member

AUD

AUD

AUD

gal

gal

gal

gal

MMbtu

MMbtu

MMbtu

MMbtu

USD ($)

USD ($)

USD ($)

Company's foreign currency and commodity positions by Year of Maturity and Account Classification

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total (A$ millions)

'

$0

'

4,082.10

0

4,082.10

0

'

'

'

'

'

'

'

'

'

'

'

2014 (A$ millions)

'

'

'

935

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2015 (A$ millions)

'

'

'

1,645.10

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2016 (A$ millions)

'

'

'

997

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2017 (A$ millions)

'

'

'

505

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total (gallons/MMbtu)

'

'

'

'

'

'

'

208,500,000

0

208,500,000

0

300,000

0

300,000

0

'

'

'

2014 (gallons/MMbtu)

'

'

'

'

'

'

'

52,200,000

'

'

'

300,000

'

'

'

'

'

'

2015 (gallons/MMbtu)

'

'

'

'

'

'

'

85,500,000

'

'

'

0

'

'

'

'

'

'

2016 (gallons/MMbtu)

'

'

'

'

'

'

'

53,300,000

'

'

'

0

'

'

'

'

'

'

2017 (gallons/MMbtu)

'

'

'

'

'

'

'

17,500,000

'

'

'

0

'

'

'

'

'

'

Fair Value Net Asset (Liability)

'

'

-109.6

'

'

'

'

16

'

'

'

-0.2

'

'

'

'

'

'

Gains (losses) to be reclassified from accumulated other comprehensive (loss) income to earnings over the next 12 months

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$15

$9

($0.20)

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) (USD $)	3 Months Ended			6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014		Jun. 30, 2013	Jun. 30, 2014		Jun. 30, 2013
Gains realized on previously monetized foreign currency cash flow hedges [Member]	'		'	'		'
Derivative Instruments, Gain (Loss) [Line Items]	'		'	'		'
Foreign currency cash flow hedge gains reclassified to earnings	$33.90		'	$74.80		'
Operating costs and expenses [Member] | Not Designated as Hedging Instrument [Member]	'		'	'		'
Derivative Instruments, Gain (Loss) [Line Items]	'		'	'		'
Gain recognized in income on non-designated derivatives	0		0	0		0
Operating costs and expenses [Member] | Cash flow hedges [Member]	'		'	'		'
Derivative Instruments, Gain (Loss) [Line Items]	'		'	'		'
Gain (loss) recognized in other comprehensive income on derivative (effective portion)	152.4	[1]	-517.6	360.4	[2]	-473
(Loss) gain reclassified from other comprehensive income into income (effective portion)	6.2	[1]	62.6	-14.8	[2]	154.4
Gain reclassified from other comprehensive income into income (ineffective portion)	1		0.1	0.8		0.3
Foreign Currency Forward Contract [Member] | Operating costs and expenses [Member] | Not Designated as Hedging Instrument [Member]	'		'	'		'
Derivative Instruments, Gain (Loss) [Line Items]	'		'	'		'
Gain recognized in income on non-designated derivatives	0		0	0		0
Foreign Currency Forward Contract [Member] | Operating costs and expenses [Member] | Cash flow hedges [Member]	'		'	'		'
Derivative Instruments, Gain (Loss) [Line Items]	'		'	'		'
Gain (loss) recognized in other comprehensive income on derivative (effective portion)	134.7	[1]	-492.6	351.2	[2]	-453.9
(Loss) gain reclassified from other comprehensive income into income (effective portion)	6.3	[1]	62.1	-12.5	[2]	147.2
Gain reclassified from other comprehensive income into income (ineffective portion)	0		0	0		0
Commodity swap contracts [Member] | Operating costs and expenses [Member] | Not Designated as Hedging Instrument [Member]	'		'	'		'
Derivative Instruments, Gain (Loss) [Line Items]	'		'	'		'
Gain recognized in income on non-designated derivatives	0		0	0		0
Commodity swap contracts [Member] | Operating costs and expenses [Member] | Cash flow hedges [Member]	'		'	'		'
Derivative Instruments, Gain (Loss) [Line Items]	'		'	'		'
Gain (loss) recognized in other comprehensive income on derivative (effective portion)	17.7		-25	9.2		-19.1
(Loss) gain reclassified from other comprehensive income into income (effective portion)	-0.1		0.5	-2.3		7.2
Gain reclassified from other comprehensive income into income (ineffective portion)	$1		$0.10	$0.80		$0.30
[1]	Includes the reclassification from "Accumulated other comprehensive loss" into earnings of $33.9 million of previously unrecognized gains on foreign currency cash flow hedge contracts monetized in the fourth quarter of 2012.
[2]	Includes the reclassification from "Accumulated other comprehensive loss" into earnings of $74.8 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) (USD $)	Jun. 30, 2014		Dec. 31, 2013
In Millions, unless otherwise specified
Gross amounts of recognized assets/liabilities [Member]	'		'
Derivative [Line Items]	'		'
Derivative assets, current	$21.30		$8.70
Derivative liabilities, current	77.8		215.8
Derivative assets, noncurrent	25.4		3
Derivative liabilities, noncurrent	62.7		264.1
Gross amounts of recognized assets/liabilities [Member] | Commodity swap contracts [Member]	'		'
Derivative [Line Items]	'		'
Derivative assets, current	9.7		8.7
Derivative liabilities, current	1.4		3.9
Derivative assets, noncurrent	8		2.8
Derivative liabilities, noncurrent	0.5		2.5
Gross amounts of recognized assets/liabilities [Member] | Foreign Currency Forward Contract [Member]	'		'
Derivative [Line Items]	'		'
Derivative assets, current	11.6		0
Derivative liabilities, current	76.4		211.9
Derivative assets, noncurrent	17.4		0.2
Derivative liabilities, noncurrent	62.2		261.6
Gross amounts offset in the condensed consolidated balance sheet [Member]	'		'
Derivative [Line Items]	'		'
Derivative assets, current	-10.9		-2.3
Derivative liabilities, current	-13.7		-1.9
Derivative assets, noncurrent	-17.1		-1.1
Derivative liabilities, noncurrent	-14.3		-1.5
Gross amounts offset in the condensed consolidated balance sheet [Member] | Commodity swap contracts [Member]	'		'
Derivative [Line Items]	'		'
Derivative assets, current	-0.7		-2.3
Derivative liabilities, current	-0.8		-1.9
Derivative assets, noncurrent	-0.5		-0.9
Derivative liabilities, noncurrent	-0.4		-1.3
Gross amounts offset in the condensed consolidated balance sheet [Member] | Foreign Currency Forward Contract [Member]	'		'
Derivative [Line Items]	'		'
Derivative assets, current	-10.2		0
Derivative liabilities, current	-12.9		0
Derivative assets, noncurrent	-16.6		-0.2
Derivative liabilities, noncurrent	-13.9		-0.2
Net amounts presented in the condensed consolidated balance sheet [Member]	'		'
Derivative [Line Items]	'		'
Derivative assets, current	10.4		6.4
Derivative liabilities, current	64.1		213.9
Derivative assets, noncurrent	8.3		1.9
Derivative liabilities, noncurrent	48.4		262.6
Net amounts presented in the condensed consolidated balance sheet [Member] | Commodity swap contracts [Member]	'		'
Derivative [Line Items]	'		'
Derivative assets, current	9		6.4
Derivative liabilities, current	0.6		2
Derivative assets, noncurrent	7.5		1.9
Derivative liabilities, noncurrent	0.1		1.2
Net amounts presented in the condensed consolidated balance sheet [Member] | Foreign Currency Forward Contract [Member]	'		'
Derivative [Line Items]	'		'
Derivative assets, current	1.4		0
Derivative liabilities, current	63.5		211.9
Derivative assets, noncurrent	0.8		0
Derivative liabilities, noncurrent	48.3		261.4
Derivatives not offset in the condensed consolidated balance sheet [Member]	'		'
Derivative [Line Items]	'		'
Derivative assets, current	-7.5	[1]	-5	[1]
Derivative liabilities, current	-7.4	[1]	-5.4	[1]
Derivative assets, noncurrent	-5.4	[1]	-1.3	[1]
Derivative liabilities, noncurrent	-5.5	[1]	-0.9	[1]
Net amount of derivatives not offset [Member]	'		'
Derivative [Line Items]	'		'
Derivative assets, current	2.9		1.4
Derivative liabilities, current	56.7		208.5
Derivative assets, noncurrent	2.9		0.6
Derivative liabilities, noncurrent	$42.90		$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.

Derivatives_and_Fair_Value_Mea6

Derivatives and Fair Value Measurements (Details 3) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Foreign currency cash flow hedge contract [Member]	'	'
Fair value of financial asset (liability) positions measured on a recurring basis	'	'
Derivative assets (liabilities), at fair value, net	($109.60)	'
Explosives Hedge Contracts Member	'	'
Fair value of financial asset (liability) positions measured on a recurring basis	'	'
Derivative assets (liabilities), at fair value, net	-0.2	'
Diesel Fuel Hedge Contracts [Member]	'	'
Fair value of financial asset (liability) positions measured on a recurring basis	'	'
Derivative assets (liabilities), at fair value, net	16	'
Fair Value, Measurements, Recurring [Member]	'	'
Fair value of financial asset (liability) positions measured on a recurring basis	'	'
Investments in debt and equity securities	63.7	67
Total net financial assets (liabilities)	-30.1	-401.2
Fair Value, Measurements, Recurring [Member] | Foreign currency cash flow hedge contract [Member]	'	'
Fair value of financial asset (liability) positions measured on a recurring basis	'	'
Derivative assets (liabilities), at fair value, net	-109.6	-473.3
Fair Value, Measurements, Recurring [Member] | Commodity swaps and options [Member]	'	'
Fair value of financial asset (liability) positions measured on a recurring basis	'	'
Derivative assets (liabilities), at fair value, net	15.8	5.1
Fair Value, Measurements, Recurring [Member] | Level 1[Member]	'	'
Fair value of financial asset (liability) positions measured on a recurring basis	'	'
Investments in debt and equity securities	27.2	28.8
Total net financial assets (liabilities)	27.2	28.8
Fair Value, Measurements, Recurring [Member] | Level 1[Member] | Foreign currency cash flow hedge contract [Member]	'	'
Fair value of financial 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 swaps and options [Member]	'	'
Fair value of financial 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 financial asset (liability) positions measured on a recurring basis	'	'
Investments in debt and equity securities	36.5	38.2
Total net financial assets (liabilities)	-57.3	-430
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Foreign currency cash flow hedge contract [Member]	'	'
Fair value of financial asset (liability) positions measured on a recurring basis	'	'
Derivative assets (liabilities), at fair value, net	-109.6	-473.3
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Commodity swaps and options [Member]	'	'
Fair value of financial asset (liability) positions measured on a recurring basis	'	'
Derivative assets (liabilities), at fair value, net	15.8	5.1
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]	'	'
Fair value of financial 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 cash flow hedge contract [Member]	'	'
Fair value of financial 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 swaps and options [Member]	'	'
Fair value of financial 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 $)	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified			Carrying value	Carrying value	Estimated fair value	Estimated fair value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'	'	'	'	'
Level 1 to Level 2 transfers	$0	$0	'	'	'	'
Level 2 to Level 1 transfers	0	0	'	'	'	'
Long-term debt, carrying value	'	'	5,994	6,002.40	'	'
Long-term debt, fair value	'	'	'	'	$6,055.20	$6,167.50

Coal_Trading_Details

Coal Trading (Details) (Coal Trading [Member], USD $)	3 Months Ended			6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014		Jun. 30, 2013	Jun. 30, 2014		Jun. 30, 2013	Dec. 31, 2013
Trading Revenues by Type of Instrument [Line Items]	'		'	'		'	'
Trading revenues	$10.30		($3.40)	$31.30		$22.50	'
Coal trading derivative instruments and balance sheet offsetting disclosures:	'		'	'		'	'
Assets from coal trading activities, gross amounts of recognized assets	430.2		'	430.2		'	418.8
Liabilities from coal trading activities, gross amounts of recognized liabilities	-359.8		'	-359.8		'	-332.7
Net coal trading assets (liabilities), gross amounts of recognized assets (liabilities)	70.4		'	70.4		'	86.1
Gross amounts of coal trading liabilities offset against associated coal trading assets	-345.4		'	-345.4		'	-324.7
Gross amounts of coal trading assets offset against associated coal trading liabilities	345.4		'	345.4		'	324.7
Net coal trading (liabilities) assets offset against associated assets (liabilities)	0		'	0		'	0
Variation margin held offset against assets from coal trading activities	-34		'	-34		'	-58
Variation margin posted offset against liabilities from coal trading activities	0		'	0		'	1.9
Net variation margin held	-34	[1]	'	-34	[1]	'	-56.1	[1]
Assets from coal trading activities, net	50.8		'	50.8		'	36.1
Liabilities from coal trading activities, net	-14.4		'	-14.4		'	-6.1
Net assets from coal trading activities	36.4		'	36.4		'	30
Commodity futures, swaps and options [Member]	'		'	'		'	'
Trading Revenues by Type of Instrument [Line Items]	'		'	'		'	'
Trading revenues	22.7		34.9	58.3		85.9	'
Physical commodity purchase / sale contracts [Member]	'		'	'		'	'
Trading Revenues by Type of Instrument [Line Items]	'		'	'		'	'
Trading revenues	-12.4		-38.3	-27		-63.4	'
Cash Flow Hedging [Member]	'		'	'		'	'
Coal trading derivative instruments and balance sheet offsetting disclosures:	'		'	'		'	'
Net variation margin held	$15		'	$15		'	$42
[1]	Approximately $15 million and $42 million of the net variation margin held at June 30, 2014 and December 31, 2013, respectively, related to cash flow hedges.

Coal_Trading_Details_1

Coal Trading (Details 1) (USD $)

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2015

In Millions, unless otherwise specified

Coal Trading [Member]

Coal Trading [Member]

Coal Trading [Member]

Coal Trading [Member]

Coal Trading [Member]

Fair Value, Measurements, Recurring [Member]

Fair Value, Measurements, Recurring [Member]

Level 1[Member]

Level 1[Member]

Level 2 [Member]

Level 2 [Member]

Level 3 [Member]

Level 3 [Member]

Minimum [Member]

Maximum [Member]

Weighted Average [Member]

Scenario, Forecast [Member]

Coal Trading [Member]

Coal Trading [Member]

Fair Value, Measurements, Recurring [Member]

Fair Value, Measurements, Recurring [Member]

Fair Value, Measurements, Recurring [Member]

Fair Value, Measurements, Recurring [Member]

Fair Value, Measurements, Recurring [Member]

Fair Value, Measurements, Recurring [Member]

Coal Trading [Member]

Coal Trading [Member]

Coal Trading [Member]

Coal Trading [Member]

Coal Trading [Member]

Coal Trading [Member]

Coal Trading [Member]

Coal Trading [Member]

Coal Trading [Member]

Coal Trading [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimate of Time to Transfer

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'12 months

Fair value coal trading net assets (liabilities) measured on recurring basis:

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Commodity futures, swaps and options

'

'

'

'

'

'

'

$37.70

$26.40

$0

$0

$37.70

$26.40

$0

$0

'

'

'

'

Physical commodity purchase/sale contracts

'

'

'

'

'

'

'

-1.3

3.6

0

0

-3.9

1.5

2.6

2.1

'

'

'

'

Total net financial assets

'

'

'

'

'

'

'

36.4

30

0

0

33.8

27.9

2.6

2.1

'

'

'

'

Coal Trading (Textuals) [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Assets from coal trading activities designated as cash flow hedges at fair value before the application of variation margin

'

'

47.9

'

47.9

'

62.9

'

'

'

'

'

'

'

'

'

'

'

'

Expected amount of gains to be realized over the next 12 months in accumulated other comprehensive income

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

35

Gain on discontinuation of cash flow hedge due to forecasted transaction no longer probable

'

'

'

'

2

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Level 1 to Level 2 transfers

0

0

0

0

0

0

'

'

'

'

'

'

'

'

'

'

'

'

'

Level 2 to Level 1 transfers

0

0

0

0

0

0

'

'

'

'

'

'

'

'

'

'

'

'

'

Level 3 transfers in and out, net

'

'

0

0

0

0

'

'

'

'

'

'

'

'

'

'

'

'

'

Summary of quantitative unobservable inputs related to coal trading Level 3 fair value measurements:

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Quality adjustment Level 3 unobservable input as percentage of overall valuation

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1.00%

8.00%

7.00%

'

Location differentials Level 3 unobservable input as percentage of overall valuation

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

17.00%

64.00%

37.00%

'

Changes in the Company's recurring Level 3 net financial assets

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Beginning of period

'

'

2.2

1.4

2.1

5.2

'

'

'

'

'

'

'

'

'

'

'

'

'

Total net gains (losses) realized/unrealized:

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Included in earnings

'

'

1.5

-0.3

3.3

-4.4

'

'

'

'

'

'

'

'

'

'

'

'

'

Settlements

'

'

-1.1

0.2

-2.8

0.5

'

'

'

'

'

'

'

'

'

'

'

'

'

End of period

'

'

2.6

1.3

2.6

1.3

'

'

'

'

'

'

'

'

'

'

'

'

'

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:

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Changes in net unrealized gains (losses)

'

'

$1.20

[1]

($2.80)

[1]

$0.30

[1]

($2.60)

[1]

'

'

'

'

'

'

'

'

'

'

'

'

'

Estimated timing of future realization of coal trading portfolio by year of expiration:

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2014

'

'

68.00%

'

68.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2015

'

'

19.00%

'

19.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2016

'

'

10.00%

'

10.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2017

'

'

2.00%

'

2.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2018

'

'

1.00%

'

1.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of trading portfolio expiration, total

'

'

100.00%

'

100.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

[1]

Within the unaudited condensed consolidated statements of operations and unaudited condensed 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

Coal_Trading_Details_2

Coal Trading (Details 2) (USD $)	3 Months Ended					6 Months Ended
In Millions, unless otherwise specified	Jul. 31, 2014	Jun. 30, 2014		Dec. 31, 2013		Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2014
	credit_rating_notch	Coal Trading [Member]		Coal Trading [Member]		External Credit Rating, Investment Grade [Member]	External Credit Rating, Non Investment Grade [Member]	Non Rated [Member]
						Credit Concentration Risk [Member]	Credit Concentration Risk [Member]	Credit Concentration Risk [Member]
						Coal Trading Positions [Member]	Coal Trading Positions [Member]	Coal Trading Positions [Member]
						Coal Trading [Member]	Coal Trading [Member]	Coal Trading [Member]
Concentration Risk [Line Items]	'	'		'		'	'	'
Credit exposure related to coal trading activities by credit grade, percentage	'	'		'		94.00%	2.00%	4.00%
Potential collateralization that may be requested by counterparties due to a material adverse event	'	$15		$7		'	'	'
Margin posted to counterparties related to material adverse event	'	0		0		'	'	'
Number of major credit rating agencies that adjusted corporate credit rating	2	'		'		'	'	'
Total number of major credit rating agencies in period that rating was adjusted	3	'		'		'	'	'
Severity of credit rating downgrade	1	'		'		'	'	'
Additional potential collateral requirements for a credit downgrade	'	0		0		'	'	'
Margin posted to counterparties related to credit rating	'	0		0		'	'	'
Net variation margin held	'	-34	[1]	-56.1	[1]	'	'	'
Initial margin posted	'	17.1		19.6		'	'	'
Margin posted in excess of the exchange-required variation and initial margin	'	$2		$1		'	'	'
[1]	Approximately $15 million and $42 million of the net variation margin held at June 30, 2014 and December 31, 2013, respectively, related to cash flow hedges.

Financing_Receivables_Details

Financing Receivables (Details)

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

12 Months Ended

In Millions, unless otherwise specified

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2013

Sep. 30, 2012

Jun. 30, 2013

Dec. 31, 2011

Jun. 30, 2014

Oct. 23, 2011

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Oct. 23, 2011

USD ($)

USD ($)

USD ($)

USD ($)

Middlemount Mine [Member]

Middlemount Mine [Member]

Middlemount Mine [Member]

Middlemount Mine [Member]

Codrilla Mine Project [Member]

Codrilla Mine Project [Member]

Codrilla Mine Project [Member]

Codrilla Mine Project [Member]

Codrilla Mine Project [Member]

Codrilla Mine Project [Member]

Financing Receivable [Member]

Financing Receivable [Member]

Financing Receivable [Member]

Financing Receivable [Member]

Financing Receivable [Member]

Financing Receivable [Member]

Coppabella, Moorvale, and Codrilla Mines [Member]

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

AUD

USD ($)

USD ($)

Middlemount Mine [Member]

Middlemount Mine [Member]

Codrilla Mine Project [Member]

Codrilla Mine Project [Member]

USD ($)

USD ($)

USD ($)

USD ($)

Accounts, Notes, Loans and Financing Receivable [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Accounts receivable, net

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$0.10

$0.10

'

'

'

'

'

Investments and other assets

'

'

'

'

'

'

'

'

'

'

'

'

'

'

378.2

351.7

347.3

323.2

30.9

28.5

'

Total financing receivables

'

'

'

'

'

'

'

'

'

'

'

'

'

'

378.3

351.8

'

'

'

'

'

Percentage of ownership before selldown

'

'

'

'

'

'

'

'

'

'

'

85.00%

'

'

'

'

'

'

'

'

'

Percentage of undivided interests acquired

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

73.30%

Consideration received by company upon completion of sell down

'

'

'

'

'

'

'

'

'

'

'

'

'

15

'

'

'

'

'

'

'

Percentage of agreed sale price as consideration upon selldown completion

'

'

'

'

'

'

'

'

'

'

'

'

'

20.00%

'

'

'

'

'

'

'

Business acquistion percentage of agreed sales price first installment payment received

'

'

'

'

'

'

'

'

'

40.00%

'

'

'

'

'

'

'

'

'

'

'

Percentage of agreed sale price as final installment payment due

'

'

'

'

'

'

'

'

'

'

'

'

40.00%

'

'

'

'

'

'

'

'

Adjustment to discounted value of note receivable

'

'

'

'

'

'

'

'

1.6

'

1.6

'

'

'

'

'

'

'

'

'

'

Equity method investment, ownership percentage

'

'

'

'

50.00%

'

50.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Basis spread over Australian Bank Bill Swap Reference Rate

'

'

'

'

'

'

3.50%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest income

4.4

1.1

8

7

1.2

2

2.6

3.4

'

'

'

'

'

'

'

'

'

'

'

'

'

Additional interest income under a full accrual basis

'

'

'

'

$1.40

$1.70

$3.10

$3.30

'

'

'

'

'

'

'

'

'

'

'

'

'

Property_Plant_Equipment_and_M2

Property, Plant, Equipment and Mine Development (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Property, Plant, Equipment and Mine Development, Net [Line Items]	'	'
Land and coal interests	$10,957.60	$11,024.10
Buildings and improvements	1,553.20	1,525.40
Machinery and equipment	2,663.30	2,777.50
Less: Accumulated depreciation, depletion and amortization	-4,473.60	-4,244.50
Total, net	$10,700.50	$11,082.50

Income_Taxes_Details_Textuals_

Income Taxes Details Textuals (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Income Tax Provision (Benefit) [Line Items]	'	'	'	'
Income tax expense (benefit)	$4	($184.70)	($48.50)	($181)
Remeasurement benefit related to foreign income tax accounts	-1.3	-37.1	-2.7	-35.5
ATO Assessment of Australian Tax Returns [Member]	'	'	'	'
Income Tax Provision (Benefit) [Line Items]	'	'	'	'
Decrease in unrecognized tax benefits	19.5	'	48.4	'
Reasonably possible decrease in net unrecognized tax benefits due to potential audit settlements	25	'	25	'
Australia Deferred Tax Assets [Member]	'	'	'	'
Income Tax Provision (Benefit) [Line Items]	'	'	'	'
Valuation allowance, deferred tax asset, change in amount	-75.7	'	-124.7	'
U.S. Capital Loss Carryforwards [Member]	'	'	'	'
Income Tax Provision (Benefit) [Line Items]	'	'	'	'
Valuation allowance, deferred tax asset, change in amount	'	($25.50)	'	'

Longterm_Debt_Details

Long-term Debt (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Debt Instrument [Line Items]	'	'
Capital lease obligations	$26.40	$30.50
Other	0.3	0.9
2013 Term Loan Facility due September 2020	'	'
Debt Instrument [Line Items]	'	'
Long-term debt	1,180.30	1,185.40
7.375% Senior Notes due November 2016	'	'
Debt Instrument [Line Items]	'	'
Long-term debt	650	650
6.00% Senior Notes due November 2018	'	'
Debt Instrument [Line Items]	'	'
Long-term debt	1,518.80	1,518.80
6.50% Senior Notes due September 2020	'	'
Debt Instrument [Line Items]	'	'
Long-term debt	650	650
6.25% Senior Notes due November 2021	'	'
Debt Instrument [Line Items]	'	'
Long-term debt	1,339.60	1,339.60
7.875% Senior Notes due November 2026	'	'
Debt Instrument [Line Items]	'	'
Long-term debt	247.6	247.5
Convertible Junior Subordinated Debentures due December 2066	'	'
Debt Instrument [Line Items]	'	'
Long-term debt	381	379.7
Carrying value	'	'
Debt Instrument [Line Items]	'	'
Total long-term debt	$5,994	$6,002.40

Longterm_Debt_Textuals_Details

Long-term Debt Textuals (Details) (USD $)

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

7.875% Senior Notes due November 2026

Junior Subordinated Debt [Member]

Junior Subordinated Debt [Member]

Australian Bonds [Member]

Term Loan & 2011 Term Loan [Member]

Voluntary Loan Repayments [Member]

Voluntary Loan Repayments [Member]

Amount Per Principal Amount [Member]

Principal Amount [Member]

Junior Subordinated Debt [Member]

Junior Subordinated Debt [Member]

Debt Instrument [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

Stated interest rate - percentage

'

'

'

7.88%

'

'

'

'

'

'

'

'

Payments of consent fees

'

$10,100,000

$0

'

$10,100,000

'

'

'

'

'

$15

$1,000

Third party fees classified in interest expense

'

'

'

'

1,600,000

1,600,000

'

'

'

'

'

'

Repayments of long-term debt

'

10,400,000

215,600,000

'

'

'

32,400,000

167,000,000

0

0

'

'

Loss on debt extinguishment

$4,500,000

'

$5,400,000

'

'

'

'

'

'

'

'

'

Pension_and_Postretirement_Ben2

Pension and Postretirement Benefit Costs (Details) (USD $)	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2014	Dec. 31, 2014
	Pension Plans, Defined Benefit [Member]	Pension Plans, Defined Benefit [Member]	Pension Plans, Defined Benefit [Member]	Pension Plans, Defined Benefit [Member]	Other Postretirement Benefit Plan, Defined Benefit [Member]	Other Postretirement Benefit Plan, Defined Benefit [Member]	Other Postretirement Benefit Plan, Defined Benefit [Member]	Other Postretirement Benefit Plan, Defined Benefit [Member]	Scenario, Forecast [Member]	Scenario, Forecast [Member]
									Pension Plans, Defined Benefit [Member]	Other Postretirement Benefit Plan, Defined Benefit [Member]
Components of net periodic benefit cost	'	'	'	'	'	'	'	'	'	'
Service cost for benefits earned	$0.50	$0.50	$1	$1.10	$3	$3.90	$6.10	$7.80	'	'
Interest cost on projected or accumulated benefit obligation	11.3	10.5	22.7	21.1	9.1	10.4	18.2	20.9	'	'
Expected return on plan assets	-13.5	-14.8	-27.1	-29.7	'	'	'	'	'	'
Amortization of prior service cost and net actuarial loss	7.8	16.7	15.7	33.3	4	7.1	7.9	12.7	'	'
Net periodic benefit cost	6.1	12.9	12.3	25.8	16.1	21.4	32.2	41.4	'	'
Funding threshhold	80.00%	'	80.00%	'	'	'	'	'	'	'
Employer contributions to pension plan	1.6	'	2.4	'	'	'	'	'	'	'
Estimated contribution in 2014 to pension plan	'	'	'	'	'	'	'	'	13	'
Increase in accumulated postretirement benefit obligation, before tax	'	'	'	'	'	'	27.6	'	'	'
Defined benefit plans estimated additional incremental contributions in 2014	'	'	'	'	'	'	'	'	'	$2

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Loss (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Accumulated other comprehensive income [Line Items]	'	'	'	'	'
Foreign Currency Translation Adjustment	($44.10)	'	($44.10)	'	($70.50)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	'	'	0	'	'
Reclassification from other comprehensive income to earnings	'	'	0	'	'
Current period change	9.9	-74.5	26.4	-73.4	'
Net actuarial loss associated with postretirement plans and workers' compensation obligations	-193.1	'	-193.1	'	-205.8
Other Comprehensive Income (Loss), Postretirement Plans and Workers' Compensation Obligations, Period Increase Decrease, Net of Tax	'	'	0	'	'
Reclassification from other comprehensive income to earnings	6.3	14.3	12.7	28.6	'
Current period change	'	'	0	'	'
Prior service cost associated with postretirement plans	-4.5	'	-4.5	'	12
Net change in fair value	'	'	0	'	'
Reclassification from other comprehensive income to earnings	0.5	-0.1	0.9	-0.2	'
Current period change	0	0	-17.4	0	'
Cash flow hedges	23.4	'	23.4	'	-155.7
Net change in fair value	67.9	-339	184.1	-270.3	'
Reclassification from other comprehensive income to earnings	-10.6	-38.3	-5	-115.4	'
Current period change	'	'	0	'	'
Available-for-sale securities	-0.5	'	-0.5	'	0.8
Net change in fair value	0.5	-7.6	-1.3	-13.8	'
Reclassification from other comprehensive income to earnings	0	13.6	0	13.5	'
Current period charge	'	'	0	'	'
Total Accumulated Other Comprehensive (Loss) Income	-218.8	'	-218.8	'	-419.2
Net change in fair value	'	'	182.8	'	'
Reclassification from other comprehensive income to earnings	'	'	8.6	'	'
Current period change	'	'	9	'	'
Net actuarial loss postretirement health care and life insurance benefits operating costs and expenses [Member]	'	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	-3.6	-6	-7.2	-12	'
Net actuarial loss defined benefit pension plans operating costs and expenses [Member]	'	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	-6.2	-13.6	-12.4	-27.2	'
Net actuarial loss defined benefit pension plans selling and administrative expenses [Member]	'	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	-1.3	-2.8	-2.7	-5.6	'
Net actuarial loss insignificant items [Member]	'	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	1	-0.3	2	-0.6	'
Net actuarial loss associated with postretirement plans total before income taxes [Member]	'	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	-10.1	-22.7	-20.3	-45.4	'
Net actuarial (loss) gain associated with postretirement plans and workers compensation obligations income tax benefit [Member]	'	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	3.8	8.4	7.6	16.8	'
Prior service cost postretirement plans postretirement health care and life insurance benefits operating costs and expenses [Member]	'	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	-0.4	0.4	-0.7	0.8	'
Prior service cost defined benefit pension plans operating costs and expenses [Member]	'	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	-0.3	-0.3	-0.6	-0.5	'
Prior service cost associated with postretirement plans total before income taxes [Member]	'	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	-0.7	0.1	-1.3	0.3	'
Prior service cost associated with postretirement plans income tax benefit (provision) [Member]	'	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Net actuarial loss and prior service cost associated with postretirement plans and workers compensation obligations	0.2	0	0.4	-0.1	'
Cash flow hedges foreign currency cash flow hedge contracts operating costs and expenses [Member]	'	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Cash flow hedges	6.3	62.1	-12.5	147.2	'
Cash flow hedges fuel and explosives commodity swaps operating costs and expenses [Member]	'	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Cash flow hedges	0.9	0.6	-1.5	7.5	'
Cash flow hedges coal trading commodity futures, swaps and options other revenues [Member]	'	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Cash flow hedges	3	0.4	20.8	25.7	'
Cash flow hedges insignificant items [Member]	'	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Cash flow hedges	0	-0.2	-0.1	-0.3	'
Cash flow hedges total before income taxes [Member]	'	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Cash flow hedges	10.2	62.9	6.7	180.1	'
Cash flow hedges income tax benefit (provision) [Member]	'	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Cash flow hedges	0.4	-24.6	-1.7	-64.7	'
Available-for-sale securities debt securities interest income [Member]	'	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Available-for-sale securities	'	'	0	0.1	'
Available-for-sale securities equity securities asset impairment [Domain]	'	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Available-for-sale securities	0	-21.5	0	-21.5	'
Total Before Income Taxes Availabile for Sale Securities [Domain]	'	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Available-for-sale securities	'	'	0	-21.4	'
Income Tax Benefit/Provision Available for Sale Securities [Domain]	'	'	'	'	'
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'
Available-for-sale securities	$0	$7.90	$0	$7.90	'

Resource_Management_and_Other_1

Resource Management and Other Commercial Events (Details) (USD $)

6 Months Ended

1 Months Ended

6 Months Ended

1 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

In Millions, unless otherwise specified

Jun. 30, 2014

Jun. 30, 2013

Jan. 31, 2014

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2013

Jun. 30, 2013

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Nonstrategic Australian mining tenement

Nonstrategic Australian mining tenement

Nonstrategic Kentucky coal reserves and surface lands

Nonstrategic Kentucky coal reserves and surface lands

Nonstrategic Kentucky coal reserves and surface lands

Nonstrategic Kentucky coal reserves and surface lands

Western U.S. Mining segment customer

Western U.S. Mining segment customer

Positive Outcome of Litigation [Member]

Positive Outcome of Litigation [Member]

Western U.S. Mining segment customer

Western U.S. Mining segment customer

Other Commercial Events [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

Contract revenue

'

'

'

'

'

'

'

'

'

'

$43.20

$33.50

Sales and production taxes and royalties

'

'

'

'

'

'

'

'

8.2

6.4

'

'

Proceeds from sale of nonstrategic assets

139.2

123.9

62.6

'

35

35

'

'

'

'

'

'

Notes receivable from sale of nonstrategic coal reserves

'

'

'

'

'

35

35

35

'

'

'

'

Gain (loss) on sale of nonstrategic asset

'

'

'

$0

'

'

$40.30

$40.30

'

'

'

'

Earnings_per_Share_EPS_Details

Earnings per Share (EPS) (Details) (USD $)	3 Months Ended			6 Months Ended
In Millions, except Per Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013		Jun. 30, 2014	Jun. 30, 2013
Earnings per Share (EPS) (Textuals) [Abstract]	'	'		'	'
Antidilutive shares excluded from EPS calculation	3.1	3.3		4.4	3.3
EPS numerator:	'	'		'	'
(Loss) income from continuing operations, net of income taxes	($72)	$101.40		($116.30)	$91.10
Less: Net income (loss) attributable to noncontrolling interests	2.1	-3.2		6.5	0.8
(Loss) income from continuing operations attributable to common stockholders, before allocation of earnings to participating securities	-74.1	104.6		-122.8	90.3
Less: Earnings allocated to participating securities	0.3	0.7		0.5	0.2
(Loss) income from continuing operations attributable to common stockholders, after allocation of earnings to participating securities	-74.4	103.9	[1]	-123.3	90.1	[1]
Income (loss) from discontinued operations, net of income taxes	0.8	-14.3		1	-23.4
Less: Loss from discontinued operations allocated to participating securities	0	-0.1		0	-0.2
Income (loss) from discontinued operations attributable to common stockholders, after earnings allocated to participating securities	0.8	-14.2	[1]	1	-23.2	[1]
Net (loss) income attributable to common stockholders, after earnings allocated to participating securities	-73.6	89.7	[1]	-122.3	66.9	[1]
EPS denominator:	'	'		'	'
Weighted average shares outstanding - basic	268	266.9		267.9	266.9
Impact of dilutive securities	0	0.6		0	0.5
Weighted average shares outstanding - diluted	268	267.5		267.9	267.4
Basic EPS attributable to common stockholders:	'	'		'	'
(Loss) income from continuing operations	($0.28)	$0.39		($0.46)	$0.34
Income (loss) from discontinued operations	$0.01	($0.06)		$0	($0.09)
Net (loss) income attributable to common stockholders	($0.27)	$0.33		($0.46)	$0.25
Diluted EPS attributable to common stockholders:	'	'		'	'
(Loss) income from continuing operations	($0.28)	$0.39		($0.46)	$0.33
Income (loss) from discontinued operations	$0.01	($0.06)		$0	($0.08)
Net (loss) income attributable to common stockholders	($0.27)	$0.33		($0.46)	$0.25
Reallocation adjustment for participatory securities	'	$0.10		'	$0.10
[1]	The reallocation adjustment for participating securities to arrive at the numerator used to calculate diluted EPS was less than $0.1 million for the three and six months ended June 30, 2013.

Financial_Instruments_and_Guar2

Financial Instruments and Guarantees with Off-Balance-Sheet Risk (Details) (USD $)	3 Months Ended			6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014		Jun. 30, 2013	Jun. 30, 2014		Jun. 30, 2013	Dec. 31, 2013
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	$2,463.20		'	$2,463.20		'	'
Amount in bank guarantees, letters of credit and surety bonds related to collateral for road maintenance, performance guarantees and other operations	157.7		'	157.7		'	'
Financial Instruments Guarantees with Off-Balance-Sheet Risk and Other Guarantees (Textuals) [Abstract]	'		'	'		'	'
Letter of credit arrangement for workers compensation	22.5		'	22.5		'	'
Collateral for letter of credit related to workers compensation	32.1		'	32.1		'	'
Maximum capacity of the securitization program	275		'	275		'	'
Amount available under the securitization program	94.6		'	94.6		'	'
Total consideration received by Company related to accounts receivable sold under securitization program	'		'	2,108.50		'	'
Cash up front from sale of receivables	'		'	1,403.10		'	'
Additional cash upon collection of underlying receivables	'		'	575.1		'	'
Non-collected receivables	130.3		'	130.3		'	'
Reduction to accounts receivable from securitization	110		'	110		'	100
Expense associated with securitization transactions	0.4		0.4	0.8		0.7	'
Credit support to Patriot	135.7		'	135.7		'	'
Credit support to Patriot ending in 2018	100		'	100		'	'
Credit support in the form of surety bonds related to Patriots Coal Act obligations	50.7		'	50.7		'	'
Potential exposure from Patriot bankruptcy	150		'	150		'	'
Liability for reclamation and bonding commitments provided on behalf of third-party coal producer	45.6		'	45.6		'	45.6
DTA and PBGC	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Letters of credit outstanding, amount	79.7		'	79.7		'	'
Dominion Terminal Associates Partnership	'		'	'		'	'
Financial Instruments Guarantees with Off-Balance-Sheet Risk and Other Guarantees (Textuals) [Abstract]	'		'	'		'	'
Ownership Percentage in DTA	37.50%		'	37.50%		'	'
DTA lease term	30		'	30		'	'
Number of letters of credit supporting reimbursement obligation	'		'	4		'	'
Maximum reimbursement obligation to commercial bank related to Dominion Terminals Associates	42.7		'	42.7		'	'
Pension Plans Agreement With PBGC and TXU Europe	'		'	'		'	'
Financial Instruments Guarantees with Off-Balance-Sheet Risk and Other Guarantees (Textuals) [Abstract]	'		'	'		'	'
Defined benefit pension plans requiring special contributions	2		'	2		'	'
Letter of credit maintained by the Company in favor of the PBGC	37		'	37		'	'
Guarantee in place from TXU Europe Limited	110		'	110		'	'
Reclamation Obligations	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	1,988.50		'	1,988.50		'	'
Lease Obligations	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	105.1		'	105.1		'	'
Workers' Compensation Obligations	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	132.2		'	132.2		'	'
Other	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	237.4	[1]	'	237.4	[1]	'	'
Surety bond	'		'	'		'	'
Financial Instruments Guarantees with Off-Balance-Sheet Risk and Other Guarantees (Textuals) [Abstract]	'		'	'		'	'
Credit support to Patriot	81.4		'	81.4		'	'
Corporate Guarantees [Member]	'		'	'		'	'
Financial Instruments Guarantees with Off-Balance-Sheet Risk and Other Guarantees (Textuals) [Abstract]	'		'	'		'	'
Credit support to Patriot	31.9		'	31.9		'	'
Self bonding	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	1,366.30		'	1,366.30		'	'
Self bonding | Reclamation Obligations	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	1,366.30		'	1,366.30		'	'
Self bonding | Lease Obligations	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	0		'	0		'	'
Self bonding | Workers' Compensation Obligations	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	0		'	0		'	'
Self bonding | Other	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	0	[1]	'	0	[1]	'	'
Surety bonds	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	542.3		'	542.3		'	'
Surety bonds | Reclamation Obligations	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	328.1		'	328.1		'	'
Surety bonds | Lease Obligations	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	105.1		'	105.1		'	'
Surety bonds | Workers' Compensation Obligations	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	98.1		'	98.1		'	'
Surety bonds | Other	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	11	[1]	'	11	[1]	'	'
Bank guarantees	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	417.3		'	417.3		'	'
Bank guarantees | Reclamation Obligations	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	276.5		'	276.5		'	'
Bank guarantees | Lease Obligations	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	0		'	0		'	'
Bank guarantees | Workers' Compensation Obligations	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	0		'	0		'	'
Bank guarantees | Other	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	140.8	[1]	'	140.8	[1]	'	'
Letters of credit	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	137.3		'	137.3		'	'
Financial Instruments Guarantees with Off-Balance-Sheet Risk and Other Guarantees (Textuals) [Abstract]	'		'	'		'	'
Credit support to Patriot	22.4		'	22.4		'	'
Letters of credit | Reclamation Obligations	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	17.6		'	17.6		'	'
Letters of credit | Lease Obligations	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	0		'	0		'	'
Letters of credit | Workers' Compensation Obligations	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	34.1		'	34.1		'	'
Letters of credit | Other	'		'	'		'	'
Guarantee Obligations [Line Items]	'		'	'		'	'
Guarantor obligations, current carrying value	$85.60	[1]	'	$85.60	[1]	'	'
[1]	Other includes the $79.7 million in letters of credit related to Dominion Terminal Associates and TXU Europe Limited described below and an additional $157.7 million in bank guarantees, letters of credit and surety bonds related to collateral for road maintenance, performance guarantees and other operations.

Commitments_and_Contingencies_

Commitments and Contingencies (Details 1) (Capital Addition Purchase Commitments [Member], USD $)	Jun. 30, 2014
In Millions, unless otherwise specified
Capital Addition Purchase Commitments [Member]	'
Long-term Purchase Commitment [Line Items]	'
Purchase commitments for capital expenditures	$74.80

Commitments_and_Contingencies_1

Commitments and Contingencies (Details 2)

1 Months Ended

3 Months Ended

6 Months Ended

6 Months Ended

6 Months Ended

12 Months Ended

48 Months Ended

In Millions, unless otherwise specified

Jan. 31, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Mar. 18, 2014

Dec. 31, 2013

Sep. 30, 2011

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jan. 19, 2012

Dec. 31, 2007

Jun. 30, 2014

Dec. 31, 2013

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Dec. 31, 2017

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

Prarie State Energy Campus [Member]

Monto Coal Pty Limited [Member]

Wilkie Creek [Member]

Gulf Power Company Litigation [Member]

Gulf Power Company Litigation [Member]

Oklahoma Lead Litigation [Member]

Oklahoma Lead Litigation [Member]

Scenario, Forecast [Member]

Scenario, Forecast [Member]

Scenario, Forecast [Member]

Scenario, Forecast [Member]

mW

AUD

USD ($)

USD ($)

T

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

sites

Loss Contingency [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Ownership percentage in subsidiaries

'

'

'

'

'

'

'

'

51.00%

'

'

'

'

'

'

'

'

'

Damages sought

'

'

'

'

'

'

'

'

1,193.20

$113.10

'

'

'

'

'

'

'

'

Class B shareholders claim for unpaid dividends

'

'

29.6

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest on Class B shareholders claim for unpaid dividends

'

'

5.8

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Requisite security filed with the court

'

'

49.6

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Damages awarded by the arbitrator to Eagle on some of Eagle's 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

'

'

15.6

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Damages sought for alleged past and future tonnage shortfalls

'

'

'

'

'

'

'

'

'

'

'

5,000,000

'

'

'

'

'

'

Litigation settlement damages awarded to plaintiff

'

'

'

'

'

'

20.6

'

'

'

'

'

'

'

'

'

'

'

Prejudgement interest

'

'

'

'

'

'

'

'

'

'

6.9

'

'

'

'

'

'

'

Charge recorded for settlement damages

'

20.6

'

20.6

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Charge recorded for prejudgement interest

'

6.9

'

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)

'

'

'

'

'

'

'

'

'

'

'

'

5

'

'

'

'

'

Number of additional national priority list sites in which CERCLA claims were asserted

'

'

'

'

'

'

'

'

'

'

'

'

13

'

'

'

'

'

Total number of national priority list sites

'

'

'

'

'

'

'

'

'

'

'

'

18

'

'

'

'

'

Reduced number of national priority list sites due to completion of work, transfer or regulatory inactivity

'

'

'

'

'

'

'

'

'

'

'

'

8

'

'

'

'

'

Undiscounted environmental clean-up liabilities, total

'

'

'

'

'

'

'

'

'

'

'

'

60.6

63.8

'

'

'

'

Undiscounted environmental clean-up liabilities, current

'

'

'

'

'

'

'

'

'

'

'

'

15.2

18.3

'

'

'

'

Funding of the newly established VEBA

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

310

Initial payment based on the construct of the negotiated settlement

90

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Payment to Patriot based on the construct of the negotiated settlement

70

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Payment to the VEBA based on the construct of the negotiated settlement

$20

'

'

'

'

'

'

'

'

'

'

'

'

'

$70

$75

$75

'

Capacity of new electricity generation project

'

'

'

'

'

'

'

1,600

'

'

'

'

'

'

'

'

'

'

Undivided interest percent of new electricity generation project

'

'

'

'

'

'

'

5.06%

'

'

'

'

'

'

'

'

'

'

Segment_Information_Details

Segment Information (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Operating segment results	'	'	'	'
Revenues	$1,758	$1,725.30	$3,384.80	$3,473.30
Adjusted EBITDA	213.1	254.3	390	534.4
Reconciliation Of Adjusted EBITDA To Consolidated (Loss) Income From Continuing Operations, Net of Income Taxes [Abstract]	'	'	'	'
Depreciation, depletion and amortization	-163.1	-185.7	-320.3	-356.4
Asset impairment	0	-21.5	0	-21.5
Amortization of basis difference related to equity affiliates	-1.3	-2.4	-2.5	-4
Asset retirement obligation expenses	-15.9	-18.3	-31.5	-37.3
Interest expense	-105.2	-110.8	-208.5	-212.1
Interest income	4.4	1.1	8	7
Income tax (provision) benefit	-4	184.7	48.5	181
(Loss) income from continuing operations, net of income taxes	-72	101.4	-116.3	91.1
Australian Mining [Member]	'	'	'	'
Operating segment results	'	'	'	'
Revenues	707.4	744.8	1,319.20	1,482.80
Adjusted EBITDA	12.2	112.5	14	212.9
Western U.S. Mining [Member]	'	'	'	'
Operating segment results	'	'	'	'
Revenues	726.6	640.9	1,408.60	1,281
Adjusted EBITDA	222	154.9	395.9	315.4
Midwestern U.S. Mining [Member]	'	'	'	'
Operating segment results	'	'	'	'
Revenues	304.6	330	607.6	666.7
Adjusted EBITDA	69.9	106.8	148.6	219.1
Trading and Brokerage [Member]	'	'	'	'
Operating segment results	'	'	'	'
Revenues	10.3	-3.4	31.3	22.5
Adjusted EBITDA	6.3	-41	4.4	-25
Corporate and Other [Member]	'	'	'	'
Operating segment results	'	'	'	'
Revenues	9.1	13	18.1	20.3
Adjusted EBITDA	($97.30)	($78.90)	($172.90)	($188)

Supplemental_GuarantorNonGuara2

Supplemental Guarantor/Non-Guarantor Financial Information (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Total revenues	$1,758	$1,725.30	$3,384.80	$3,473.30
Operating costs and expenses (exclusive of items shown separately below)	1,467.60	1,437.20	2,862.40	2,826.60
Depreciation, depletion and amortization	163.1	185.7	320.3	356.4
Asset retirement obligation expenses	15.9	18.3	31.5	37.3
Selling and administrative expenses	59.2	64	118.7	129.1
Other operating (income) loss:	'	'	'	'
Net (gain) loss on disposal or exchange of assets	-2.2	-43.2	-12	-45.8
Asset impairment	0	21.5	0	21.5
Loss (income) from equity affiliates and investment in subsidiaries	21.6	15.4	28.2	33
Interest expense	105.2	110.8	208.5	212.1
Interest income	-4.4	-1.1	-8	-7
Unrealized loss (gain) on derivatives	'	0	'	0
(Loss) income from continuing operations before income taxes	-68	-83.3	-164.8	-89.9
Income tax provision (benefit)	4	-184.7	-48.5	-181
(Loss) income from continuing operations, net of income taxes	-72	101.4	-116.3	91.1
Income (loss) from discontinued operations, net of income taxes	0.8	-14.3	1	-23.4
Net (loss) income	-71.2	87.1	-115.3	67.7
Less: Net income (loss) attributable to noncontrolling interests	2.1	-3.2	6.5	0.8
Net (loss) income attributable to common stockholders	-73.3	90.3	-121.8	66.9
Other comprehensive income (loss), net of income taxes	74.5	-431.6	200.4	-431
Comprehensive income (loss)	3.3	-344.5	85.1	-363.3
Less: Comprehensive income attributable to noncontrolling interests	2.1	-3.2	6.5	0.8
Comprehensive income (loss) attributable to common stockholders	1.2	-341.3	78.6	-364.1
Parent Company [Member]	'	'	'	'
Total revenues	0	0	0	0
Operating costs and expenses (exclusive of items shown separately below)	-7.3	-62.8	13.9	-154.5
Depreciation, depletion and amortization	0	0	0	0
Asset retirement obligation expenses	0	0	0	0
Selling and administrative expenses	11	14.6	24.6	23.8
Other operating (income) loss:	'	'	'	'
Net (gain) loss on disposal or exchange of assets	0	0	0	0
Asset impairment	'	21.5	'	21.5
Loss (income) from equity affiliates and investment in subsidiaries	4.4	-174.4	-35.2	-89.6
Interest expense	107.2	101.3	212.9	203.2
Interest income	-0.1	-0.1	-0.2	-68.2
Unrealized loss (gain) on derivatives	'	0	'	0
(Loss) income from continuing operations before income taxes	-115.2	99.9	-216	63.8
Income tax provision (benefit)	-41	5.8	-93	-9.5
(Loss) income from continuing operations, net of income taxes	-74.2	94.1	-123	73.3
Income (loss) from discontinued operations, net of income taxes	0.9	-3.8	1.2	-6.4
Net (loss) income	-73.3	90.3	-121.8	66.9
Less: Net income (loss) attributable to noncontrolling interests	0	0	0	0
Net (loss) income attributable to common stockholders	-73.3	90.3	-121.8	66.9
Other comprehensive income (loss), net of income taxes	74.5	-431.6	200.4	-431
Comprehensive income (loss)	1.2	-341.3	78.6	-364.1
Less: Comprehensive income attributable to noncontrolling interests	0	0	0	0
Comprehensive income (loss) attributable to common stockholders	1.2	-341.3	78.6	-364.1
Guarantor Subsidiaries [Member]	'	'	'	'
Total revenues	1,005	972.5	1,981.40	1,987.10
Operating costs and expenses (exclusive of items shown separately below)	741.2	823	1,468	1,523.90
Depreciation, depletion and amortization	76.2	85.5	153.4	165.1
Asset retirement obligation expenses	7	10.2	15.6	21.8
Selling and administrative expenses	42.8	44.3	84.1	91.7
Other operating (income) loss:	'	'	'	'
Net (gain) loss on disposal or exchange of assets	-2.3	-43	-11.9	-45.8
Asset impairment	'	0	'	0
Loss (income) from equity affiliates and investment in subsidiaries	2.1	4.5	2.7	8.4
Interest expense	1.7	8.7	3.3	11
Interest income	-2.1	-90.5	-4.5	-125.4
Unrealized loss (gain) on derivatives	'	502.6	'	461.6
(Loss) income from continuing operations before income taxes	138.4	-372.8	270.7	-125.2
Income tax provision (benefit)	41	-193.1	65.8	-85.2
(Loss) income from continuing operations, net of income taxes	97.4	-179.7	204.9	-40
Income (loss) from discontinued operations, net of income taxes	-0.5	-1	-1.2	-2.5
Net (loss) income	96.9	-180.7	203.7	-42.5
Less: Net income (loss) attributable to noncontrolling interests	0	0	0	0
Net (loss) income attributable to common stockholders	96.9	-180.7	203.7	-42.5
Other comprehensive income (loss), net of income taxes	-7.5	51	2.4	28.5
Comprehensive income (loss)	89.4	-129.7	206.1	-14
Less: Comprehensive income attributable to noncontrolling interests	0	0	0	0
Comprehensive income (loss) attributable to common stockholders	89.4	-129.7	206.1	-14
Non-Guarantor Subsidiaries [Member]	'	'	'	'
Total revenues	774.9	818.8	1,446.20	1,615
Operating costs and expenses (exclusive of items shown separately below)	755.6	743	1,423.30	1,586
Depreciation, depletion and amortization	86.9	100.2	166.9	191.3
Asset retirement obligation expenses	8.9	8.1	15.9	15.5
Selling and administrative expenses	5.4	5.1	10	13.6
Other operating (income) loss:	'	'	'	'
Net (gain) loss on disposal or exchange of assets	0.1	-0.2	-0.1	0
Asset impairment	'	0	'	0
Loss (income) from equity affiliates and investment in subsidiaries	19.5	10.9	25.5	24.6
Interest expense	1.7	95.4	3.1	205.9
Interest income	-7.6	-5.1	-14.1	-21.4
Unrealized loss (gain) on derivatives	'	-502.6	'	-461.6
(Loss) income from continuing operations before income taxes	-95.6	364	-184.3	61.1
Income tax provision (benefit)	4	2.6	-21.3	-86.3
(Loss) income from continuing operations, net of income taxes	-99.6	361.4	-163	147.4
Income (loss) from discontinued operations, net of income taxes	0.4	-9.5	1	-14.5
Net (loss) income	-99.2	351.9	-162	132.9
Less: Net income (loss) attributable to noncontrolling interests	2.1	-3.2	6.5	0.8
Net (loss) income attributable to common stockholders	-101.3	355.1	-168.5	132.1
Other comprehensive income (loss), net of income taxes	2.6	-49.9	-15.9	-64.1
Comprehensive income (loss)	-96.6	302	-177.9	68.8
Less: Comprehensive income attributable to noncontrolling interests	2.1	-3.2	6.5	0.8
Comprehensive income (loss) attributable to common stockholders	-98.7	305.2	-184.4	68
Eliminations [Member]	'	'	'	'
Total revenues	-21.9	-66	-42.8	-128.8
Operating costs and expenses (exclusive of items shown separately below)	-21.9	-66	-42.8	-128.8
Depreciation, depletion and amortization	0	0	0	0
Asset retirement obligation expenses	0	0	0	0
Selling and administrative expenses	0	0	0	0
Other operating (income) loss:	'	'	'	'
Net (gain) loss on disposal or exchange of assets	0	0	0	0
Asset impairment	'	0	'	0
Loss (income) from equity affiliates and investment in subsidiaries	-4.4	174.4	35.2	89.6
Interest expense	-5.4	-94.6	-10.8	-208
Interest income	5.4	94.6	10.8	208
Unrealized loss (gain) on derivatives	'	0	'	0
(Loss) income from continuing operations before income taxes	4.4	-174.4	-35.2	-89.6
Income tax provision (benefit)	0	0	0	0
(Loss) income from continuing operations, net of income taxes	4.4	-174.4	-35.2	-89.6
Income (loss) from discontinued operations, net of income taxes	0	0	0	0
Net (loss) income	4.4	-174.4	-35.2	-89.6
Less: Net income (loss) attributable to noncontrolling interests	0	0	0	0
Net (loss) income attributable to common stockholders	4.4	-174.4	-35.2	-89.6
Other comprehensive income (loss), net of income taxes	4.9	-1.1	13.5	35.6
Comprehensive income (loss)	9.3	-175.5	-21.7	-54
Less: Comprehensive income attributable to noncontrolling interests	0	0	0	0
Comprehensive income (loss) attributable to common stockholders	$9.30	($175.50)	($21.70)	($54)

Supplemental_GuarantorNonGuara3

Supplemental Guarantor/Non-Guarantor Financial Information (Details 1) (USD $)	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Current assets	'	'	'	'
Cash and cash equivalents	$498.40	$444	$517.90	$558.80
Accounts receivable, net	447.1	557.9	'	'
Receivables from affiliates, net	0	0	'	'
Inventories	548.4	506.7	'	'
Assets from coal trading activities, net	50.8	36.1	'	'
Deferred income taxes	67.2	66.4	'	'
Other current assets	265.9	381.6	'	'
Total current assets	1,877.80	1,992.70	'	'
Property, plant, equipment and mine development, net	10,700.50	11,082.50	'	'
Deferred income taxes	82.1	7.8	'	'
Investments and other assets	1,031.80	1,050.40	'	'
Notes receivable from affiliates, net	0	0	'	'
Total assets	13,692.20	14,133.40	'	'
Current liabilities	'	'	'	'
Current maturities of long-term debt	20.8	31.7	'	'
Payables to affiliates, net	0	0	'	'
Deferred income taxes	7.5	0	'	'
Liabilities from coal trading activities, net	14.4	6.1	'	'
Accounts payable and accrued expenses	1,462	1,737.70	'	'
Total current liabilities	1,504.70	1,775.50	'	'
Long-term debt, less current maturities	5,973.20	5,970.70	'	'
Deferred income taxes	59.5	40.9	'	'
Notes payable to affiliates, net	0	0	'	'
Other noncurrent liabilities	2,150.40	2,398.40	'	'
Total liabilities	9,687.80	10,185.50	'	'
Peabody Energy Corporation stockholders' equity	3,960.80	3,908.70	'	'
Noncontrolling interests	43.6	39.2	'	'
Total stockholders' equity	4,004.40	3,947.90	'	'
Total liabilities and stockholders' equity	13,692.20	14,133.40	'	'
Parent Company [Member]	'	'	'	'
Current assets	'	'	'	'
Cash and cash equivalents	323.6	300.7	333.8	269.6
Accounts receivable, net	0.3	1.3	'	'
Receivables from affiliates, net	369.2	68.4	'	'
Inventories	0	0	'	'
Assets from coal trading activities, net	0	0	'	'
Deferred income taxes	24	0	'	'
Other current assets	11.1	34.5	'	'
Total current assets	728.2	404.9	'	'
Property, plant, equipment and mine development, net	0	0	'	'
Deferred income taxes	0	16.5	'	'
Investments and other assets	10,704.60	11,394.90	'	'
Notes receivable from affiliates, net	0	0	'	'
Total assets	11,432.80	11,816.30	'	'
Current liabilities	'	'	'	'
Current maturities of long-term debt	12	12	'	'
Payables to affiliates, net	0	0	'	'
Deferred income taxes	0	1.9	'	'
Liabilities from coal trading activities, net	0	0	'	'
Accounts payable and accrued expenses	194.2	360	'	'
Total current liabilities	206.2	373.9	'	'
Long-term debt, less current maturities	5,955.30	5,959.10	'	'
Deferred income taxes	22.4	0	'	'
Notes payable to affiliates, net	1,078.10	1,078.20	'	'
Other noncurrent liabilities	210	496.4	'	'
Total liabilities	7,472	7,907.60	'	'
Peabody Energy Corporation stockholders' equity	3,960.80	3,908.70	'	'
Noncontrolling interests	0	0	'	'
Total stockholders' equity	3,960.80	3,908.70	'	'
Total liabilities and stockholders' equity	11,432.80	11,816.30	'	'
Guarantor Subsidiaries [Member]	'	'	'	'
Current assets	'	'	'	'
Cash and cash equivalents	0.2	0.3	0.2	0.3
Accounts receivable, net	0	0	'	'
Receivables from affiliates, net	0	0	'	'
Inventories	217.6	235.1	'	'
Assets from coal trading activities, net	46.1	46.7	'	'
Deferred income taxes	36	61.9	'	'
Other current assets	17.2	73.7	'	'
Total current assets	317.1	417.7	'	'
Property, plant, equipment and mine development, net	4,904.60	5,055.70	'	'
Deferred income taxes	0	0	'	'
Investments and other assets	8.5	8.8	'	'
Notes receivable from affiliates, net	1,546.80	1,478.60	'	'
Total assets	6,777	6,960.80	'	'
Current liabilities	'	'	'	'
Current maturities of long-term debt	0.1	0.1	'	'
Payables to affiliates, net	296.5	10.4	'	'
Deferred income taxes	0	0	'	'
Liabilities from coal trading activities, net	4.8	0.2	'	'
Accounts payable and accrued expenses	580.9	577.7	'	'
Total current liabilities	882.3	588.4	'	'
Long-term debt, less current maturities	6.4	6.5	'	'
Deferred income taxes	34.4	55.9	'	'
Notes payable to affiliates, net	0	0	'	'
Other noncurrent liabilities	1,555	1,521.80	'	'
Total liabilities	2,478.10	2,172.60	'	'
Peabody Energy Corporation stockholders' equity	4,298.90	4,788.20	'	'
Noncontrolling interests	0	0	'	'
Total stockholders' equity	4,298.90	4,788.20	'	'
Total liabilities and stockholders' equity	6,777	6,960.80	'	'
Non-Guarantor Subsidiaries [Member]	'	'	'	'
Current assets	'	'	'	'
Cash and cash equivalents	174.6	143	183.9	288.9
Accounts receivable, net	447.1	559.1	'	'
Receivables from affiliates, net	0	0	'	'
Inventories	330.8	271.6	'	'
Assets from coal trading activities, net	4.7	0	'	'
Deferred income taxes	7.2	6.4	'	'
Other current assets	237.6	273.4	'	'
Total current assets	1,202	1,253.50	'	'
Property, plant, equipment and mine development, net	5,795.90	6,026.80	'	'
Deferred income taxes	79.4	7.8	'	'
Investments and other assets	742.9	762.6	'	'
Notes receivable from affiliates, net	0	0	'	'
Total assets	7,820.20	8,050.70	'	'
Current liabilities	'	'	'	'
Current maturities of long-term debt	8.7	19.6	'	'
Payables to affiliates, net	72.7	58	'	'
Deferred income taxes	7.5	0	'	'
Liabilities from coal trading activities, net	9.6	16.5	'	'
Accounts payable and accrued expenses	687.2	802.5	'	'
Total current liabilities	785.7	896.6	'	'
Long-term debt, less current maturities	11.5	5.1	'	'
Deferred income taxes	0	1.5	'	'
Notes payable to affiliates, net	468.7	400.4	'	'
Other noncurrent liabilities	385.4	380.2	'	'
Total liabilities	1,651.30	1,683.80	'	'
Peabody Energy Corporation stockholders' equity	6,125.30	6,327.70	'	'
Noncontrolling interests	43.6	39.2	'	'
Total stockholders' equity	6,168.90	6,366.90	'	'
Total liabilities and stockholders' equity	7,820.20	8,050.70	'	'
Reclassifications/Eliminations [Member]	'	'	'	'
Current assets	'	'	'	'
Cash and cash equivalents	0	0	'	'
Accounts receivable, net	-0.3	-2.5	'	'
Receivables from affiliates, net	-369.2	-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	-369.5	-83.4	'	'
Property, plant, equipment and mine development, net	0	0	'	'
Deferred income taxes	2.7	-16.5	'	'
Investments and other assets	-10,424.20	-11,115.90	'	'
Notes receivable from affiliates, net	-1,546.80	-1,478.60	'	'
Total assets	-12,337.80	-12,694.40	'	'
Current liabilities	'	'	'	'
Current maturities of long-term debt	0	0	'	'
Payables to affiliates, net	-369.2	-68.4	'	'
Deferred income taxes	0	-1.9	'	'
Liabilities from coal trading activities, net	0	-10.6	'	'
Accounts payable and accrued expenses	-0.3	-2.5	'	'
Total current liabilities	-369.5	-83.4	'	'
Long-term debt, less current maturities	0	0	'	'
Deferred income taxes	2.7	-16.5	'	'
Notes payable to affiliates, net	-1,546.80	-1,478.60	'	'
Other noncurrent liabilities	0	0	'	'
Total liabilities	-1,913.60	-1,578.50	'	'
Peabody Energy Corporation stockholders' equity	-10,424.20	-11,115.90	'	'
Noncontrolling interests	0	0	'	'
Total stockholders' equity	-10,424.20	-11,115.90	'	'
Total liabilities and stockholders' equity	($12,337.80)	($12,694.40)	'	'

Supplemental_GuarantorNonGuara4

Supplemental Guarantor/Non-Guarantor Financial Information (Details 2) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Cash Flows From Operating Activities	'	'	'
Net cash (used in) provided by continuing operations	'	$157,100,000	$365,900,000
Net cash (used in) provided by discontinued operations	'	-81,800,000	-34,500,000
Net cash (used in) provided by operating activities	'	75,300,000	331,400,000
Cash Flows From Investing Activities	'	'	'
Additions to property, plant, equipment and mine development	'	-64,700,000	-166,500,000
Changes in accrued expenses related to capital expenditures	'	-17,500,000	-102,600,000
Proceeds from disposal of assets, net of notes receivable	'	139,200,000	123,900,000
Purchases of debt securities	'	-4,200,000	-9,700,000
Proceeds from sales and maturities of debt securities	'	5,000,000	17,000,000
Proceeds from the maturity of short-term investments	4,800,000	0	4,800,000
Contributions to joint ventures	'	-271,300,000	-323,800,000
Distributions from joint ventures	'	269,000,000	372,100,000
Advances to related parties	'	-12,300,000	-35,700,000
Repayments of loans from related parties	'	2,200,000	18,200,000
Other, net	'	-2,000,000	-3,600,000
Net cash provided by (used in) continuing operations	'	43,400,000	-105,900,000
Net cash provided by (used in) discontinued operations	'	5,000,000	-300,000
Net cash provided by (used in) investing activities	'	48,400,000	-106,200,000
Cash Flows From Financing Activities	'	'	'
Repayments of long-term debt	'	-10,400,000	-215,600,000
Payment of debt issuance costs	'	-10,100,000	0
Dividends paid	'	-46,100,000	-45,900,000
Other, net	'	-2,700,000	-4,600,000
Transactions with affiliates, net	'	0	0
Net cash provided by (used in) financing activities	'	-69,300,000	-266,100,000
Net change in cash and cash equivalents	'	54,400,000	-40,900,000
Cash and cash equivalents at beginning of period	'	444,000,000	558,800,000
Cash and cash equivalents at end of period	517,900,000	498,400,000	517,900,000
Parent Company [Member]	'	'	'
Cash Flows From Operating Activities	'	'	'
Net cash (used in) provided by continuing operations	'	-112,400,000	114,500,000
Net cash (used in) provided by discontinued operations	'	-72,900,000	-8,100,000
Net cash (used in) provided by operating activities	'	-185,300,000	106,400,000
Cash Flows From Investing Activities	'	'	'
Additions to property, plant, equipment and mine development	'	0	0
Changes in accrued expenses related to capital expenditures	'	0	0
Proceeds from disposal of assets, net of notes receivable	'	0	0
Purchases of debt securities	'	0	0
Proceeds from sales and maturities of debt securities	'	0	0
Proceeds from the maturity of short-term investments	'	'	0
Contributions to joint ventures	'	0	0
Distributions from joint ventures	'	0	0
Advances to related parties	'	0	0
Repayments of loans from related parties	'	0	0
Other, net	'	0	0
Net cash provided by (used in) continuing operations	'	0	0
Net cash provided by (used in) discontinued operations	'	0	0
Net cash provided by (used in) investing activities	'	0	0
Cash Flows From Financing Activities	'	'	'
Repayments of long-term debt	'	-6,000,000	-167,000,000
Payment of debt issuance costs	'	-10,100,000	'
Dividends paid	'	-46,100,000	-45,900,000
Other, net	'	1,000,000	900,000
Transactions with affiliates, net	'	269,400,000	169,800,000
Net cash provided by (used in) financing activities	'	208,200,000	-42,200,000
Net change in cash and cash equivalents	'	22,900,000	64,200,000
Cash and cash equivalents at beginning of period	'	300,700,000	269,600,000
Cash and cash equivalents at end of period	333,800,000	323,600,000	333,800,000
Guarantor Subsidiaries [Member]	'	'	'
Cash Flows From Operating Activities	'	'	'
Net cash (used in) provided by continuing operations	'	330,300,000	496,500,000
Net cash (used in) provided by discontinued operations	'	-1,400,000	500,000
Net cash (used in) provided by operating activities	'	328,900,000	497,000,000
Cash Flows From Investing Activities	'	'	'
Additions to property, plant, equipment and mine development	'	-32,100,000	-45,100,000
Changes in accrued expenses related to capital expenditures	'	-1,300,000	-2,400,000
Proceeds from disposal of assets, net of notes receivable	'	50,900,000	42,100,000
Purchases of debt securities	'	0	0
Proceeds from sales and maturities of debt securities	'	0	0
Proceeds from the maturity of short-term investments	'	'	0
Contributions to joint ventures	'	0	0
Distributions from joint ventures	'	0	0
Advances to related parties	'	0	0
Repayments of loans from related parties	'	0	0
Other, net	'	-1,700,000	-3,400,000
Net cash provided by (used in) continuing operations	'	15,800,000	-8,800,000
Net cash provided by (used in) discontinued operations	'	0	0
Net cash provided by (used in) investing activities	'	15,800,000	-8,800,000
Cash Flows From Financing Activities	'	'	'
Repayments of long-term debt	'	0	-100,000
Payment of debt issuance costs	'	0	'
Dividends paid	'	0	0
Other, net	'	-1,700,000	-5,200,000
Transactions with affiliates, net	'	-343,100,000	-483,000,000
Net cash provided by (used in) financing activities	'	-344,800,000	-488,300,000
Net change in cash and cash equivalents	'	-100,000	-100,000
Cash and cash equivalents at beginning of period	'	300,000	300,000
Cash and cash equivalents at end of period	200,000	200,000	200,000
Non-Guarantor Subsidiaries [Member]	'	'	'
Cash Flows From Operating Activities	'	'	'
Net cash (used in) provided by continuing operations	'	-60,800,000	-245,100,000
Net cash (used in) provided by discontinued operations	'	-7,500,000	-26,900,000
Net cash (used in) provided by operating activities	'	-68,300,000	-272,000,000
Cash Flows From Investing Activities	'	'	'
Additions to property, plant, equipment and mine development	'	-32,600,000	-121,400,000
Changes in accrued expenses related to capital expenditures	'	-16,200,000	-100,200,000
Proceeds from disposal of assets, net of notes receivable	'	88,300,000	81,800,000
Purchases of debt securities	'	-4,200,000	-9,700,000
Proceeds from sales and maturities of debt securities	'	5,000,000	17,000,000
Proceeds from the maturity of short-term investments	'	'	4,800,000
Contributions to joint ventures	'	-271,300,000	-323,800,000
Distributions from joint ventures	'	269,000,000	372,100,000
Advances to related parties	'	-12,300,000	-35,700,000
Repayments of loans from related parties	'	2,200,000	18,200,000
Other, net	'	-300,000	-200,000
Net cash provided by (used in) continuing operations	'	27,600,000	-97,100,000
Net cash provided by (used in) discontinued operations	'	5,000,000	-300,000
Net cash provided by (used in) investing activities	'	32,600,000	-97,400,000
Cash Flows From Financing Activities	'	'	'
Repayments of long-term debt	'	-4,400,000	-48,500,000
Payment of debt issuance costs	'	0	'
Dividends paid	'	0	0
Other, net	'	-2,000,000	-300,000
Transactions with affiliates, net	'	73,700,000	313,200,000
Net cash provided by (used in) financing activities	'	67,300,000	264,400,000
Net change in cash and cash equivalents	'	31,600,000	-105,000,000
Cash and cash equivalents at beginning of period	'	143,000,000	288,900,000
Cash and cash equivalents at end of period	$183,900,000	$174,600,000	$183,900,000

Supplemental_GuarantorNonGuara5

Supplemental Guarantor/Non-Guarantor Financial Information Textuals (Details)	3 Months Ended
	Jun. 30, 2014
Percent of ownership of certain U.S. subsidiaries that fully and unconditionally guarantee the Senior Notes	100.00%
7.375% Senior Notes due November 2016	'
Stated interest rate - percentage	7.38%
6.00% Senior Notes due November 2018	'
Stated interest rate - percentage	6.00%
6.50% Senior Notes due September 2020	'
Stated interest rate - percentage	6.50%
6.25% Senior Notes due November 2021	'
Stated interest rate - percentage	6.25%
7.875% Senior Notes due November 2026	'
Stated interest rate - percentage	7.88%