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Data Type:	xbrli:integerItemType
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Account Receivable Securitization, Program Fees, percentage

No definition available.

Name:	aci_AccountReceivableSecuritizationProgramFees
Namespace Prefix:	aci_
Data Type:	num:percentItemType
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Plan of Reorganization, Holder's of First Lien Creditors, Percentage

No definition available.

Name:	aci_PlanofReorganizationHoldersofFirstLienCreditorsPercentage
Namespace Prefix:	aci_
Data Type:	num:percentItemType
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The amount owed to the reporting entity by counterparties in securitized loan transactions.

No definition available.

Name:	us-gaap_AccountsReceivableFromSecuritization
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Data Type:	xbrli:monetaryItemType
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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

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Data Type:	num:percentItemType
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Contractual interest rate for funds borrowed, under the debt agreement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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

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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.

No definition available.

Name:	us-gaap_DebtInstrumentLineItems
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Data Type:	xbrli:stringItemType
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Period Type:	duration

Amount debtor-in-possession financing arranged (but not necessarily all borrowed).

No definition available.

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

- References

No definition available.

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Ratio applied to the conversion of stock split, for example but not limited to, one share converted to two or two shares converted to one.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB TOPIC 4.C)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187143-122770

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Stock Split
-URI http://asc.fasb.org/extlink&oid=6525746

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Name:	us-gaap_LongtermDebtTypeAxis=aci_A9875SeniorNotesDue2019Member
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