Document and Entity Information - shares	9 Months Ended
	Jun. 30, 2018	Jul. 30, 2018
Document And Entity Information [Abstract]
Entity Registrant Name	EMCORE CORP
Entity Central Index Key	0000808326
Document Type	10-Q
Document Period End Date	Jun. 30, 2018
Document Fiscal Period Focus	Q3
Document Fiscal Year Focus	2018
Current Fiscal Year End Date	--09-30
Entity Filer Category	Accelerated Filer
Amendment Flag	false
Entity Common Stock, Shares Outstanding		27,493,846