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VARIABLE INTEREST ENTITIES - WKY CoalPlay (Details) - WKY CoalPlay $ in Millions | 6 Months Ended
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Jun. 30, 2020 USD ($)
Variable Interest Entities |
Payments | $ 10.8
Percentage of internal rate of return on purchase price, if leased reserves acquired | 7.00%

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- Definition Amount paid during the period for minimum royalty obligations. + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Percentage of internal rate of return provided to the counterparty in the purchase price under the option to acquire the leased coal reserves. + References No definition available. + Details
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Namespace Prefix: | arlp_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- 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
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Period Type: | duration

X
- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |