Changes in tax reserves.

No definition available.

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- Definition

Minerals resource rent tax benefit (expense)

+ References

No definition available.

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- Definition

Re-measurement of foreign taxes.

+ References

No definition available.

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- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(h))

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph h

-Article 4

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Income Tax Expense (or Benefit)

-URI http://asc.fasb.org/extlink&oid=6515339

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 9

-Subparagraph (a),(b)

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- Definition

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- Definition

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-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph h

-Subparagraph 1

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- Definition

The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-Number 210

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- Definition

+ References

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- Definition

Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax exempt income, equity in earnings (loss) of an unconsolidated subsidiary, minority noncontrolling interest income (loss), tax holiday, disposition of a business, disposition of an asset, repatriation of foreign earnings, repatriation of foreign earnings jobs creation act of 2004, increase (decrease) in enacted tax rate, prior year income taxes, increase (decrease) in deferred tax asset valuation allowance, and other adjustments.

+ References

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- Definition

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-Number 210

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Income Taxes (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of the expected statutory federal income tax provision to the Company's actual income tax provision
Expected income tax benefit at U.S. federal statutory rate									$ (191.7)	$ (257.0)	$ (73.0)
Changes in valuation allowance, income tax									569.4	(29.4)	521.5
Changes in tax reserves									(81.5)btu_ChangesInTaxReserves	8.8btu_ChangesInTaxReserves	24.5btu_ChangesInTaxReserves
Excess depletion									(65.3)	(72.7)	(69.4)
Foreign earnings repatriation									(71.4)	0	0
Foreign earnings provision differential									28.8	62.7	(59.6)
General business tax credits									(19.2)	(18.9)	(17.4)
Minerals resource rent tax, net of federal tax									16.1	(87.4)	77.2
Remeasurement of foreign income tax accounts	1.2btu_RemeasurementOfForeignTaxes	(1.2)btu_RemeasurementOfForeignTaxes	(1.3)btu_RemeasurementOfForeignTaxes	(1.4)btu_RemeasurementOfForeignTaxes	(6.2)btu_RemeasurementOfForeignTaxes	(2.6)btu_RemeasurementOfForeignTaxes	(37.1)btu_RemeasurementOfForeignTaxes	1.6btu_RemeasurementOfForeignTaxes	(2.7)btu_RemeasurementOfForeignTaxes	(44.3)btu_RemeasurementOfForeignTaxes	7.9btu_RemeasurementOfForeignTaxes
State income taxes, net of federal tax benefit									(2.3)	(0.2)	(1.1)
Capital loss									0	0	(118.1)
Other, net									21.0	(9.9)	(30.2)
Total income tax provision (benefit)									$ 201.2us-gaap_IncomeTaxExpenseBenefit	$ (448.3)us-gaap_IncomeTaxExpenseBenefit	$ 262.3us-gaap_IncomeTaxExpenseBenefit