XML 120 R140.htm IDEA: XBRL DOCUMENT
v3.19.3.a.u2

Pension and Savings Plans Fair Value of Assets in the Master Trust by Asset (Details) - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Apr. 01, 2017 | Dec. 31, 2016
--- | --- | --- | --- | --- | ---
Corporate bonds |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | $ 598.3 | $ 466.1 |  |  |
U.S. government securities |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 154.9 | 198.9 |  |  |
International government securities |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 18.2 | 12.4 |  |  |
Mortgage Backed Securities, Other |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 3.4 |  |  |  |
Commercial Paper |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period |  | 2.1 |  |  |
Cash funds |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 33.2 | 38.4 |  |  |
Real estate interests |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 4.1 | 6.2 |  |  |
Private mutual funds |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 43.1 | 40.7 |  |  |
Level 1 |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 169.1 | 219.9 |  |  |
Level 1 | Corporate bonds |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 0.0 | 0.0 |  |  |
Level 1 | U.S. government securities |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 135.9 | 181.5 |  |  |
Level 1 | International government securities |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 0.0 | 0.0 |  |  |
Level 1 | Mortgage Backed Securities, Other |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 0.0 |  |  |  |
Level 1 | Commercial Paper |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period |  | 0.0 |  |  |
Level 1 | Cash funds |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 33.2 | 38.4 |  |  |
Level 1 | Real estate interests |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 0.0 | 0.0 |  |  |
Level 2 |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 638.9 | 498.0 |  |  |
Level 2 | Corporate bonds |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 598.3 | 466.1 |  |  |
Level 2 | U.S. government securities |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 19.0 | 17.4 |  |  |
Level 2 | International government securities |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 18.2 | 12.4 |  |  |
Level 2 | Mortgage Backed Securities, Other |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 3.4 |  |  |  |
Level 2 | Commercial Paper |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period |  | 2.1 |  |  |
Level 2 | Cash funds |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 0.0 | 0.0 |  |  |
Level 2 | Real estate interests |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 0.0 | 0.0 |  |  |
Level 3 |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 4.1 | 6.2 | $ 11.8 | $ 13.8 | $ 14.1
Level 3 | Corporate bonds |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 0.0 | 0.0 |  |  |
Level 3 | U.S. government securities |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 0.0 | 0.0 |  |  |
Level 3 | International government securities |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 0.0 | 0.0 |  |  |
Level 3 | Mortgage Backed Securities, Other |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 0.0 |  |  |  |
Level 3 | Commercial Paper |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period |  | 0.0 |  |  |
Level 3 | Cash funds |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 0.0 | 0.0 |  |  |
Level 3 | Real estate interests |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 4.1 | 6.2 |  |  |
Pension Plans, Defined Benefit |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | 855.2 | 764.8 | $ 776.6 |  |
Fair Value Pension Plan Assets |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets at end of period | $ 812.1 | $ 724.1 |  |  |

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 6: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_USTreasuryAndGovernmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_MortgageBackedSecuritiesOtherMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_CommercialPaperMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_ShortTermInvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_RealEstateInvestmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_PrivateEquityFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=btu_FairValuePensionPlanAssetsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |