Document and Entity Information - USD ($)	12 Months Ended
	Oct. 31, 2021	Dec. 23, 2021	Apr. 30, 2021
Cover [Abstract]
Entity Registrant Name	FUELCELL ENERGY, INC.
Entity Central Index Key	0000886128
Document Type	10-K
Document Period End Date	Oct. 31, 2021
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Trading Symbol	FCEL
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Security Exchange Name	NASDAQ
Current Fiscal Year End Date	--10-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity File Number	1-14204
Entity Tax Identification Number	06-0853042
Entity Common Stock, Shares Outstanding		366,672,894
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 Transition Report	false
Entity Incorporation, State or Country Code	DE
Document Annual Report	true
Entity Well-known Seasoned Issuer	Yes
ICFR Auditor Attestation Flag	true
Entity Voluntary Filers	No
Entity Public Float			$ 3,226,456,793