Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Series D Preferred Stock [Member]	Series C Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Series D Preferred Stock [Member]	Additional Paid-in Capital [Member] Series C Preferred Stock [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Deferred Compensation [Member]
Balance at at Oct. 31, 2018	$ 82,194			$ 1	$ 1,073,463			$ (990,867)	$ (403)	$ (363)	$ 363
Balance at (in shares) at Oct. 31, 2018				7,972,686
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share based compensation	987				987
Fee adjustment for common stock issuance	90				90
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans	27				27
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans, (in shares)				1,946
Series C convertible preferred stock conversions	1,974				1,974
Series C convertible preferred stock conversions, (in shares)				127,829
Series C convertible preferred stock adjustment for beneficial conversion feature	6,586				6,586
Series C convertible stock redemption value adjustments	(8,550)				(8,550)
Series D convertible preferred stock conversions	4,334				4,334
Series D convertible preferred stock conversions, (in shares)				932,144
Convertible preferred stock redemption accretion		$ (3,793)				$ (3,793)
Preferred dividends — Series B	(800)				(800)
Impact of the adoption of Topic 606	(6,654)							(6,654)
Effect of foreign currency translation	7								7
Net loss attributable to FuelCell Energy, Inc.	(17,548)							(17,548)
Balance at at Jan. 31, 2019	58,854			$ 1	1,074,318			(1,015,069)	(396)	(363)	363
Balance at (in shares) at Jan. 31, 2019				9,034,605
Balance at at Oct. 31, 2018	82,194			$ 1	1,073,463			(990,867)	(403)	(363)	363
Balance at (in shares) at Oct. 31, 2018				7,972,686
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Effect of foreign currency translation	(133)
Net loss attributable to FuelCell Energy, Inc.	(37,078)
Balance at at Apr. 30, 2019	49,835			$ 1	1,084,969			(1,034,599)	(536)	(466)	466
Balance at (in shares) at Apr. 30, 2019				13,709,330
Balance at at Jan. 31, 2019	58,854			$ 1	1,074,318			(1,015,069)	(396)	(363)	363
Balance at (in shares) at Jan. 31, 2019				9,034,605
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued, non-employee compensation	102				102
Common stock issued, non-employee compensation, (in shares)				29,454
Share based compensation	955				955
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans	(219)				(219)
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans, (in shares)				52,784
Series A warrant exchange, shares				500,000
Series C convertible preferred stock conversions	10,355				10,355
Series C convertible preferred stock conversions, (in shares)				2,127,528
Series D convertible preferred stock conversions	6,305				6,305
Series D convertible preferred stock conversions, (in shares)				1,994,413
Convertible preferred stock redemption accretion			$ (6,047)				$ (6,047)
Preferred dividends — Series B	(800)				(800)
Adjustment for deferred compensation											103
Adjustment for deferred compensation, (in shares)				(29,454)
Adjustment for deferred compensation										(103)
Effect of foreign currency translation	(140)								(140)
Net loss attributable to FuelCell Energy, Inc.	(19,530)							(19,530)
Balance at at Apr. 30, 2019	49,835			$ 1	1,084,969			(1,034,599)	(536)	(466)	466
Balance at (in shares) at Apr. 30, 2019				13,709,330
Balance at at Oct. 31, 2019	$ 75,737			$ 19	1,151,454			(1,075,089)	(647)	(466)	466
Balance at (in shares) at Oct. 31, 2019	193,608,684			193,608,684
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share based compensation	$ 488				488
Orion warrant exercises	25,994			$ 1	25,993
Orion warrant exercises, shares				9,396,320
Sale of common stock, net of fees	3,502			$ 1	3,501
Sale of common stock, net of fees (in shares)				7,938,228
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans	(6)				(6)
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans, (in shares)				2,585
Preferred dividends — Series B	(931)				(931)
Adjustment for deferred compensation											(29)
Adjustment for deferred compensation, (in shares)				20,012
Adjustment for deferred compensation										29
Effect of foreign currency translation	(49)								(49)
Net loss attributable to FuelCell Energy, Inc.	(40,151)							(40,151)
Balance at at Jan. 31, 2020	64,584			$ 21	1,180,499			(1,115,240)	(696)	(437)	437
Balance at (in shares) at Jan. 31, 2020				210,965,829
Balance at at Oct. 31, 2019	$ 75,737			$ 19	1,151,454			(1,075,089)	(647)	(466)	466
Balance at (in shares) at Oct. 31, 2019	193,608,684			193,608,684
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Effect of foreign currency translation	$ (91)
Net loss attributable to FuelCell Energy, Inc.	(54,920)
Balance at at Apr. 30, 2020	$ 49,316			$ 21	1,180,042			(1,130,009)	(738)	(437)	437
Balance at (in shares) at Apr. 30, 2020	211,052,401			211,052,401
Balance at at Jan. 31, 2020	$ 64,584			$ 21	1,180,499			(1,115,240)	(696)	(437)	437
Balance at (in shares) at Jan. 31, 2020				210,965,829
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share based compensation	375				375
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans	(32)				(32)
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans, (in shares)				86,572
Preferred dividends — Series B	(800)				(800)
Effect of foreign currency translation	(42)								(42)
Net loss attributable to FuelCell Energy, Inc.	(14,769)							(14,769)
Balance at at Apr. 30, 2020	$ 49,316			$ 21	$ 1,180,042			$ (1,130,009)	$ (738)	$ (437)	$ 437
Balance at (in shares) at Apr. 30, 2020	211,052,401			211,052,401