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v3.20.4

Leases - Textual (Details) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 USD ($)
Operating Leased Assets [Line Items] |
Lease obligation, assumed amount recoverable from third parties | $ 0.0
Maximum |
Operating Leased Assets [Line Items] |
Operating and finance leases remaining lease term | 21 years
Minimum |
Operating Leased Assets [Line Items] |
Operating and finance leases remaining lease term | 1 year

X
- Definition Lease Obligation, Assumed Amount Recoverable from Third Parties + References No definition available. + Details
Name: | btu_LeaseObligationAssumedAmountRecoverablefromThirdParties
Namespace Prefix: | btu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Operating and Finance Leases Remaining Lease Term + References No definition available. + Details
Name: | btu_OperatingandFinanceLeasesRemainingLeaseTerm
Namespace Prefix: | btu_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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_OperatingLeasedAssetsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |