Document and Entity Information - shares	3 Months Ended
	Jan. 31, 2021	Mar. 12, 2021
Cover [Abstract]
Entity Registrant Name	FUELCELL ENERGY, INC.
Entity Central Index Key	0000886128
Document Type	10-Q
Document Period End Date	Jan. 31, 2021
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Trading Symbol	FCEL
Title of 12(b) Security	Common stock, par value $0.0001 per share
Security Exchange Name	NASDAQ
Current Fiscal Year End Date	--10-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity File Number	1-14204
Entity Tax Identification Number	06-0853042
Entity Common Stock, Shares Outstanding		322,429,123
Entity Address, State or Province	CT
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity Address, Address Line One	3 Great Pasture Road
Entity Address, City or Town	Danbury
Entity Address, Postal Zip Code	06810
City Area Code	203
Local Phone Number	825-6000
Document Quarterly Report	true
Document Transition Report	false
Entity Incorporation, State or Country Code	DE