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.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
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

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_DebtInstrumentAxis=hayn_OverdraftFacilityHaynesInternationalLtdMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

Debt - Overdraft Facilities (Details) - Sep. 30, 2018 € in Thousands, £ in Thousands, SFr in Thousands, $ in Thousands	EUR (€)	GBP (£)	CHF (SFr)	USD ($)
Haynes International Ltd. overdraft facility
Debt and long-term obligations
Maximum borrowing capacity		£ 1,700		$ 2,215
Available borrowing capacity		£ 1,700		2,215
Haynes International S.A.R.L. overdraft facility
Debt and long-term obligations
Maximum borrowing capacity	€ 240			278
Available borrowing capacity	€ 240			278
Haynes International AG overdraft facility
Debt and long-term obligations
Maximum borrowing capacity			SFr 400	407
Available borrowing capacity			SFr 400	$ 407