Represents the ratio of cash flow to interest expense.

No definition available.

Name:	arlp_CashFlowToInterestExpenseRatioActual
Namespace Prefix:	arlp_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the period over which the ratios required under the terms of the debt agreement are calculated.

+ References

No definition available.

+ Details

Name:	arlp_DebtArrangementsPeriodOverWhichRatiosAreCalculated
Namespace Prefix:	arlp_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the minimum cash flow to interest expense ratio required under the terms of the debt agreement.

+ References

No definition available.

+ Details

Name:	arlp_DebtInstrumentCovenantsCashFlowToInterestExpenseRatio
Namespace Prefix:	arlp_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the maximum debt to cash flow ratio required under the terms of the debt agreement.

+ References

No definition available.

+ Details

Name:	arlp_DebtInstrumentCovenantsDebtToCashFlowRatio
Namespace Prefix:	arlp_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the fixed charge coverage ratio, after distributions, required under the terms of the debt agreement.

+ References

No definition available.

+ Details

Name:	arlp_DebtInstrumentCovenantsFixedChargeCoverageRatio
Namespace Prefix:	arlp_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of variable interest rate benchmarks allowed under terms of debt instrument.

+ References

No definition available.

+ Details

Name:	arlp_DebtInstrumentNumberOfVariableRateBenchmarks
Namespace Prefix:	arlp_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the ratio of debt to cash flow.

+ References

No definition available.

+ Details

Name:	arlp_DebtToCashFlowRatioActual
Namespace Prefix:	arlp_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6036836-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

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

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash outflow paid to third parties in connection with debt origination, which will be amortized over the remaining maturity period of the associated long-term debt.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

+ Details

Name:	us-gaap_PaymentsOfDebtIssuanceCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_DebtInstrumentAxis=arlp_CreditAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_EurodollarMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=arlp_LendersProvidingExtensionCommitmentApril2017Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=arlp_CreditAgreementFirstLienRequirementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_StandbyLettersOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=arlp_SwinglineSubfacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=arlp_FourthAmendedAndRestatedCreditAgreementMember
Namespace Prefix:
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LONG-TERM DEBT - Credit Facility (Details) $ in Thousands		3 Months Ended
LONG-TERM DEBT - Credit Facility (Details) $ in Thousands	Mar. 09, 2020 USD ($) item	Mar. 31, 2020 USD ($)	Jan. 27, 2017 USD ($)
Long-Term Debt
Debt issuance costs incurred		$ 5,758
Credit Agreement
Long-Term Debt
Maximum borrowing capacity	$ 537,750
Number of benchmarks \| item	3
ARLP debt arrangements requirements, fixed charge coverage ratio		1.0
ARLP debt arrangements requirements, debt to cash flow ratio	2.5
ARLP debt arrangements requirements, cash flow to interest expense ratio	3.0
Actual debt to cash flow ratio for trailing twelve months		1.58
Credit Agreement \| Eurodollar Rate
Long-Term Debt
Effective interest rate (as a percent)		3.50%
Credit Agreement \| Extended Commitment to May 23, 2021
Long-Term Debt
Maximum borrowing capacity	$ 459,500
Credit Agreement \| Credit Agreement, first lien
Long-Term Debt
ARLP debt arrangements requirements, debt to cash flow ratio	1.5
Revolving credit facility
Long-Term Debt
Line of credit facility, available for borrowing		$ 228,500
Annual commitment fee percentage, undrawn portion		0.35%
ARLP debt arrangements requirements, period over which the ratios are required to be maintained	12 months
Actual cash flow to interest expense ratio for trailing twelve months		10.82
Revolving credit facility \| Credit Agreement, first lien
Long-Term Debt
Actual debt to cash flow ratio for trailing twelve months		0.81
Letters of credit subfacility
Long-Term Debt
Maximum borrowing capacity	$ 125,000
Letters of credit outstanding		$ 9,300
Swingline subfacility
Long-Term Debt
Maximum borrowing capacity	$ 15,000
Fourth Amended and Restated Credit Agreement
Long-Term Debt
Maximum borrowing capacity			$ 494,750