XML 66 R55.htm IDEA: XBRL DOCUMENT v3.24.1.u1

Commitments and Contingencies - Restricted Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Long-term Purchase Commitment [Line Items]
Total restricted investments	$ 38,055	$ 40,597
Workers’ compensation and black lung obligations
Long-term Purchase Commitment [Line Items]
Total restricted investments	3,279	2,514
Reclamation-related obligations
Long-term Purchase Commitment [Line Items]
Total restricted investments	30,305	33,173
Financial payments and other performance obligations
Long-term Purchase Commitment [Line Items]
Total restricted investments	$ 4,471	$ 4,910

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

X

- Definition

Investments which are not defined as or included in marketable (debt, equity, or other) securities whose use is restricted in whole or in part, generally by contractual agreements or regulatory requirements. For use in an unclassified balance sheet.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 954
-SubTopic 210
-Name Accounting Standards Codification
-Section 45
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480632/954-210-45-4

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 954
-SubTopic 210
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480602/954-210-50-2

+ Details

Name:	us-gaap_RestrictedInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

Name:	us-gaap_CollateralAxis=amr_WorkersCompensationAndBlackLungObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_CollateralAxis=amr_ReclamationRelatedObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_CollateralAxis=amr_FinancialPaymentsAndOtherPerformanceObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: