Subsequent Events - Additional Information (Details)									3 Months Ended						9 Months Ended
	Sep. 04, 2019 USD ($)	Aug. 15, 2019 USD ($)	Aug. 13, 2019 USD ($) MW	Aug. 08, 2019 USD ($) $ / shares MW	Aug. 08, 2019 USD ($) $ / shares shares	Jun. 28, 2019	May 15, 2019 USD ($)	Dec. 21, 2018 USD ($)	Jul. 31, 2019 USD ($) shares	Apr. 30, 2019 USD ($)	Jan. 31, 2019 USD ($)	Jul. 31, 2018 USD ($) shares	Apr. 30, 2018 USD ($)	Jan. 31, 2018 USD ($)	Jul. 31, 2019 USD ($)	Jul. 31, 2018 USD ($)	Aug. 12, 2019 USD ($)	Oct. 31, 2018 USD ($)
Subsequent Event [Line Items]
Dividends declared										$ 800,000	$ 800,000	$ 800,000	$ 800,000	$ 800,000
Sale of common stock, net of fees									$ 16,199,000			$ 6,745,000
Common Stock [Member]
Subsequent Event [Line Items]
Sale of common stock, net of fees (in shares) | shares									43,997,807			435,329
Sale of common stock, net of fees									$ 3,000
Series B Cumulative Convertible Perpetual Preferred Stock [Member]
Subsequent Event [Line Items]
Dividends declared							$ 0		810,000			$ 800,000			$ 2,410,000	$ 2,400,000
Dividends payment date							May 15, 2019
Aggregate amount of dividend payment							$ 800,000
Preferred stock, dividend rate, percentage							5.00%								5.00%	5.00%
Preferred stock failed to pay dividend payments multiplier percentage							0.0625%
Dividends payable									810,000						$ 810,000
Subsequent Event [Member] | Series B Cumulative Convertible Perpetual Preferred Stock [Member]
Subsequent Event [Line Items]
Dividends declared		$ 0
Dividends payment date		Aug. 15, 2019
Aggregate amount of dividend payment		$ 800,000
Preferred stock, dividend rate, percentage		5.00%
Preferred stock failed to pay dividend payments multiplier percentage		0.0625%
Dividends payable		$ 830,000
B. Riley FBR, Inc and Oppenheimer & Co. Inc. [Member] | Subsequent Event [Member] | Sales Agreement [Member] | Common Stock [Member]
Subsequent Event [Line Items]
Sale of common stock, net of fees (in shares) | shares					7,500,000
Average sale of stock price per share | $ / shares				$ 0.31	$ 0.31
Gross proceeds from sale of common stock					$ 2,400,000
Sales commissions paid to agent					70,000
Net proceeds on sales agreement					$ 2,300,000
Sale of common stock, net of fees	$ 27,100,000
B. Riley FBR, Inc and Oppenheimer & Co. Inc. [Member] | Subsequent Event [Member] | Sales Agreement [Member] | Common Stock [Member] | Maximum [Member]
Subsequent Event [Line Items]
Stock to be sold during period value new issues	$ 22,900,000
NRG Energy, Inc. [Member]
Subsequent Event [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity																		$ 40,000,000
NRG Energy, Inc. [Member] | Six Amendment [Member] | Central CA Fuel Cell 2, LLC [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Accrued interest				$ 300,000
NRG Energy, Inc. [Member] | Six Amendment [Member] | Tulare BioMAT [Member] | California [Member] | Central CA Fuel Cell 2, LLC [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Capacity of plant | MW				2.8
Generate Lending Construction Loan Agreement [Member] | Generate Lending, LLC [Member]
Subsequent Event [Line Items]
Line of credit facility, optional call right notice period															10 days
Line of credit facility, optional call right															Pursuant to the terms of the Generate Agreement, Generate Lending had an optional call right which, if exercised, was required to be noticed during the ten day period beginning on June 20, 2019 and ending on (and including) June 30, 2019 (as amended or modified from time to time, the “Call Right”). If Generate Lending had exercised its Call Right during that period, all of the Working Capital Loans (as described elsewhere herein) (in an amount equal to $10,000,000), together with all accrued and unpaid interest thereon, would have been due and payable in their entirety, without penalty or premium, prior to September 30, 2019.
Line of credit facility, optional call right beginning date															Jun. 20, 2019
Line of credit facility, optional call right ending date															Jun. 30, 2019
Line of credit facility, optional call right amount									$ 10,000,000						$ 10,000,000
Generate Lending Construction Loan Agreement [Member] | FuelCell Energy Finance II, LLC [Member] | Generate Lending, LLC [Member]
Subsequent Event [Line Items]
Liquidation damages amount								$ 650,000
Generate Lending Construction Loan Agreement [Member] | First Generate Amendment [Member] | FuelCell Energy Finance II, LLC [Member] | Generate Lending, LLC [Member]
Subsequent Event [Line Items]
Line of credit facility, optional call right notice period						10 days
Line of credit facility, optional call right						On June 28, 2019, FCEF II, Generate Lending, and various project company guarantors entered into the First Amendment to the Generate Agreement (the “First Generate Amendment”). Under the First Generate Amendment, the Call Right was modified to give Generate Lending the right to exercise the Call Right, requiring payment of all Working Capital Loans and all accrued and unpaid interest thereon on September 30, 2019, during the ten day period beginning on August 1, 2019 and ending on (and including) August 11, 2019. Concurrently with the execution of the First Generate Amendment, the Company, FCEF II and Generate Lending entered into the First Amendment to the Right to Finance Agreement, which provided that, if Generate Lending exercised its Call Right, the Right to Finance Agreement (as amended) would terminate.
Line of credit facility, optional call right beginning date						Aug. 01, 2019
Line of credit facility, optional call right ending date						Aug. 11, 2019
Generate Lending Construction Loan Agreement [Member] | Second Generate Amendment [Member] | Subsequent Event [Member] | FuelCell Energy Finance II, LLC [Member] | Generate Lending, LLC [Member]
Subsequent Event [Line Items]
Power and generate period of working capital loans			3 days
Generate Lending Construction Loan Agreement [Member] | Second Generate Amendment [Member] | Brookhaven, New York [Member] | Subsequent Event [Member] | FuelCell Energy Finance II, LLC [Member] | Generate Lending, LLC [Member]
Subsequent Event [Line Items]
Capacity of plant | MW			7.4
Fifth Third Bank Construction Loan Agreement [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			$ 23,000,000														$ 18,000,000