Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Nov. 29, 2018	Mar. 29, 2018
Document And Entity Information [Abstract]
Entity Registrant Name	EMCORE CORP
Entity Central Index Key	0000808326
Document Type	10-K
Document Period End Date	Sep. 30, 2018
Document Fiscal Period Focus	Q4
Document Fiscal Year Focus	2018
Current Fiscal Year End Date	--09-30
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Amendment Flag	false
Entity Common Stock, Shares Outstanding		27,607,194
Entity Shell Company	false
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 132.2