Debt Instrument, Basis Spread on Variable Rate, Increase (Decrease)

No definition available.

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ 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 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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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

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- 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

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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

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

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

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=hcc_CitibankMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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Data Type:	na
Balance Type:
Period Type:

- Details

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- Details

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- Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=hcc_SeniorSecuredNotesDue2024Member
Namespace Prefix:
Data Type:	na
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Period Type:

Debt - ABL Facility (Details) - USD ($)	Jan. 23, 2017	Nov. 02, 2017	Oct. 03, 2017	Sep. 30, 2017	Apr. 01, 2016
Citibank \| Revolving Credit Agreement
Line of Credit Facility [Line Items]
Aggregate lender commitment	$ 100,000,000.0				$ 50,000,000
Interest rate margins	100.00%
Citibank \| Revolving Credit Agreement \| Successor
Line of Credit Facility [Line Items]
Remaining borrowing capacity				$ 100,000,000
Subsequent Event \| Citibank \| Revolving Credit Agreement
Line of Credit Facility [Line Items]
Aggregate lender commitment			$ 500,000,000.0
Subsequent Event \| Senior Notes \| Senior Secured Notes Due 2024
Line of Credit Facility [Line Items]
Aggregate lender commitment		$ 350,000,000.0
Stated interest rate		8.00%