Document and Entity Information - USD ($)	12 Months Ended
	Sep. 30, 2019	Nov. 14, 2019	Mar. 31, 2019
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, 2019
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			$ 299,299,784
Entity Common Stock, Shares Outstanding		12,513,500
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY