Debt Instrument, Amortization Payments, Quarterly Amount

No definition available.

Name:	aci_DebtInstrumentAmortizationPaymentsQuarterlyAmount
Namespace Prefix:	aci_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Debt Instrument, Covenant Compliance, Liquidity Compliance, Amount

+ References

No definition available.

+ Details

Name:	aci_DebtInstrumentCovenantComplianceLiquidityComplianceAmount
Namespace Prefix:	aci_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Debt Instrument, Covenants, Default to Indebtedness, Minimum

+ References

No definition available.

+ Details

Name:	aci_DebtInstrumentCovenantsDefaulttoIndebtednessMinimum
Namespace Prefix:	aci_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Debt Instrument, Covenants, Default to Surety, Reclamation or Similar Bond, Minimum

+ References

No definition available.

+ Details

Name:	aci_DebtInstrumentCovenantsDefaulttoSuretyReclamationorSimilarBondMinimum
Namespace Prefix:	aci_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Debt Instrument, Covenants, Default to Uninsured Judgment, Minimum

+ References

No definition available.

+ Details

Name:	aci_DebtInstrumentCovenantsDefaulttoUninsuredJudgmentMinimum
Namespace Prefix:	aci_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Debt Instrument, Covenants, Pre-Payment, Cash Proceeds of Debt and Other Non-Ordinary Sales or Dispositions, Percent

+ References

No definition available.

+ Details

Name:	aci_DebtInstrumentCovenantsPrePaymentCashProceedsofDebtandOtherNonOrdinarySalesorDispositionsPercent
Namespace Prefix:	aci_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Covenants, Uninsured Losses or Proceedings Against, Minimum

+ References

No definition available.

+ Details

Name:	aci_DebtInstrumentCovenantsUninsuredLossesorProceedingsAgainstMinimum
Namespace Prefix:	aci_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Debt Instrument, Guarantees, Equity Interest of Domestic Subsidiaries, Percent

+ References

No definition available.

+ Details

Name:	aci_DebtInstrumentGuaranteesEquityInterestofDomesticSubsidiariesPercent
Namespace Prefix:	aci_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt Instrument, Guarantees, Equity Interest of Foreign Subsidiaries, Percent

+ References

No definition available.

+ Details

Name:	aci_DebtInstrumentGuaranteesEquityInterestofForeignSubsidiariesPercent
Namespace Prefix:	aci_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt Instrument, Paid-in-Kind Interest, Accrual Rate, Percent

+ References

No definition available.

+ Details

Name:	aci_DebtInstrumentPaidinKindInterestAccrualRatePercent
Namespace Prefix:	aci_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Securitization Agreement, Liquidity Covenant, Amount

+ References

No definition available.

+ Details

Name:	aci_SecuritizationAgreementLiquidityCovenantAmount
Namespace Prefix:	aci_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Securitization Agreement, Liquidity Covenant, Compliance Terms, Period

+ References

No definition available.

+ Details

Name:	aci_SecuritizationAgreementLiquidityCovenantComplianceTermsPeriod
Namespace Prefix:	aci_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Securitization Agreement, Term

+ References

No definition available.

+ Details

Name:	aci_SecuritizationAgreementTerm
Namespace Prefix:	aci_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount owed to the reporting entity by counterparties in securitized loan transactions.

+ References

No definition available.

+ Details

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

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of assets pledged to secure a debt instrument.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

+ Details

Name:	us-gaap_DebtInstrumentCollateralAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(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

- Details

Name:	us-gaap_StatementScenarioAxis=us-gaap_SuccessorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

Debt and Financing Arrangements (Successor Company Debt) (Details) - USD ($)	Oct. 05, 2016	Dec. 31, 2016	Jan. 13, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Letters of credit outstanding				$ 21,300,000
Successor [Member]
Debt Instrument [Line Items]
Securitized accounts receivable			$ 200,000,000
Term of securitization agreement	3 years
Securitization agreement liquidity covenant amount	$ 175,000,000
Number of consecutive days under liquidity threshold	60 days
Successor [Member] \| Senior Notes [Member] \| New First Lien Debt Facility [Member]
Debt Instrument [Line Items]
Maximum amount of Debtors' liquidity	$ 300,000,000
Quarterly principal amortization payments	$ 816,250
Accrual of PIK interest (percent)	1.00%
Amount of voting equity interests of domestic subsidiaries guaranteed (percent)	100.00%
Amount of voting equity interests of foreign owned subsidiaries guaranteed (percent)	65.00%
Net cash proceeds of from debt issuances and other non-ordinary sales or dispositions (percent)	100.00%
Default to indebtedness	$ 35,000,000
Default to surety, reclamation or similar bond	50,000,000
Default to uninsured judgment	35,000,000
Uninsured losses or proceedings against	$ 35,000,000
Term of instrument	5 years
Successor [Member] \| Senior Notes [Member] \| New First Lien Debt Facility [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate (percent)	9.00%
Successor [Member] \| Senior Notes [Member] \| New First Lien Debt Facility [Member] \| LIBOR [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Basis spread on variable rate (percent)	1.00%
Successor [Member] \| Senior Notes [Member] \| New First Lien Debt Facility [Member] \| Base Rate [Member]
Debt Instrument [Line Items]
Basis spread on variable rate (percent)	8.00%
Successor [Member] \| Line of Credit [Member] \| Extended Securitization Facility [Member]
Debt Instrument [Line Items]
Letters of credit outstanding		$ 154,000,000
Borrowing base		83,400,000
Cash collateral		71,000,000
Remaining availability		$ 0