Document and Entity Information - shares	9 Months Ended
	Jul. 31, 2017	Sep. 06, 2017
Document And Entity Information [Abstract]
Entity Registrant Name	FUELCELL ENERGY INC
Entity Central Index Key	0000886128
Document Type	10-Q
Document Period End Date	Jul. 31, 2017
Amendment Flag	false
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q3
Trading Symbol	FCEL
Current Fiscal Year End Date	--10-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		61,485,741