XML 90 R77.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Commitments and Contingencies - Contingencies (Details) - 3 months ended Mar. 31, 2018 $ in Millions, $ in Millions | AUD ($) defendant | USD ($)
--- | --- | ---
Monto Coal Pty Limited |  |
Loss Contingency [Abstract] |  |
Ownership Percentage In Subsidiaries |  | 51.00%
Number of defendants | defendant | 3 |
Minimum | Monto Coal Pty Limited |  |
Loss Contingency [Abstract] |  |
Damages sought, value | $ 15.6 |
Maximum | Monto Coal Pty Limited |  |
Loss Contingency [Abstract] |  |
Damages sought, value | $ 1,800.0 |
Berenergy Corporation vs. the Company | Berenergy |  |
Loss Contingency [Abstract] |  |
Loss contingency accrual |  | $ 13.1

X
- Definition Ownership Percentage In subsidiaries. + References No definition available. + Details
Name: | btu_OwnershipPercentageInSubsidiaries
Namespace Prefix: | btu_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_LossContingencyAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of loss contingency liability. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349 + Details
Name: | us-gaap_LossContingencyAccrualAtCarryingValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The value (monetary amount) of the award the plaintiff seeks in the legal matter. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14557-108349 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349 + Details
Name: | us-gaap_LossContingencyDamagesSoughtValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Number of defendants named in a legal action. + References No definition available. + Details
Name: | us-gaap_LossContingencyNumberOfDefendants
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_LossContingenciesByNatureOfContingencyAxis=btu_MontoCoalPtyLimitedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LitigationCaseAxis=btu_BerenergyCorporationvs.theCompanyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=btu_BerenergyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |