Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Deferred Compensation [Member]	Noncontrolling Interest In Subsidiaries [Member]
Balance at at Oct. 31, 2015	$ 94,754	$ 3	$ 934,488	$ (838,673)	$ (509)	$ (78)	$ 78	$ (555)
Balance at (in shares) at Oct. 31, 2015		25,964,710
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Sale of common stock, prepaid warrants and warrants, public offering	34,736		34,736
Sale of common stock, prepaid warrants and warrants, public offering, in shares		1,474,000
Exercise of prepaid warrants, in shares		1,100,000
Sale of common stock	36,056	$ 1	36,055
Sale of common stock (in shares)		6,023,372
Common stock issued, non-employee compensation	157		157
Common stock issued, non-employee compensation, in shares		24,379
Share based compensation	3,425		3,425
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans		587,963
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans	(286)		(286)
Noncontrolling interest in subsidiaries	(251)							(251)
Purchase of noncontrolling shares of subsidiary	(3)		(809)					$ 806
Preferred dividends - Series B	(3,200)		(3,200)
Adjustment for deferred compensation							101
Adjustment for deferred compensation						(101)
Effect of foreign currency translation	(35)				(35)
Net loss attributable to FuelCell Energy, Inc.	(50,957)			(50,957)
Balance at at Oct. 31, 2016	114,396	$ 4	1,004,566	(889,630)	(544)	(179)	179
Balance at (in shares) at Oct. 31, 2016		35,174,424
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Sale of common stock, warrants and public offering	13,884	$ 1	13,883
Sale of common stock, warrants and public offering, in shares		12,000,000
Exercise of prepaid warrants and warrants	12,722	$ 1	12,721
Exercise of prepaid warrants and warrants. in shares		13,660,926
Sale of common stock	12,431	$ 1	12,430
Sale of common stock (in shares)		7,245,430
Common stock issued, non-employee compensation	129		129
Common stock issued, non-employee compensation, in shares		86,001
Share based compensation	4,585		4,585
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans		1,284,673
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans	(84)		(84)
Series C convertible preferred stock conversions	167		167
Series C convertible preferred stock conversions, shares		108,696
Noncontrolling interest in subsidiaries	0
Preferred dividends - Series B	(3,200)		(3,200)
Adjustment for deferred compensation							101
Adjustment for deferred compensation						(101)
Effect of foreign currency translation	129				129
Net loss attributable to FuelCell Energy, Inc.	(53,903)			(53,903)
Adjustment for deferred compensation (in shares)		(67,334)
Balance at at Oct. 31, 2017	$ 101,256	$ 7	1,045,197	(943,533)	(415)	(280)	280
Balance at (in shares) at Oct. 31, 2017	69,492,816	69,492,816
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Sale of common stock	$ 7,129	$ 1	7,128
Sale of common stock (in shares)		5,715,180
Exercise of warrants	3,326		3,326
Exercise of warrants, in shares		2,595,710
Common stock issued, non-employee compensation	282		282
Common stock issued, non-employee compensation, in shares		158,708
Share based compensation	3,238		3,238
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans		(178,950)
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans	(660)		(660)
Series C convertible preferred stock conversions	20,220	$ 2	20,218
Series C convertible preferred stock conversions, shares		17,956,413
Noncontrolling interest in subsidiaries	0
Preferred dividends - Series B	(3,200)		(3,200)
Series D Preferred stock redemption accretion	(2,075)		(2,075)
Adjustment for deferred compensation							83
Adjustment for deferred compensation						(83)
Effect of foreign currency translation	12				12
Net loss attributable to FuelCell Energy, Inc.	(47,334)			(47,334)
Adjustment for deferred compensation (in shares)		(67,640)
Balance at at Oct. 31, 2018	$ 82,194	$ 10	$ 1,073,454	$ (990,867)	$ (403)	$ (363)	$ 363
Balance at (in shares) at Oct. 31, 2018	95,672,237	95,672,237