Document and Entity Information - USD ($)	12 Months Ended
	Sep. 30, 2017	Nov. 16, 2017	Mar. 31, 2017
Document and Entity Information
Entity Registrant Name	HAYNES INTERNATIONAL INC
Entity Central Index Key	0000858655
Document Type	10-K
Document Period End Date	Sep. 30, 2017
Amendment Flag	false
Current Fiscal Year End Date	--09-30
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 339,017,581
Entity Common Stock, Shares Outstanding		12,509,757
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY