Debt Financing	9 Months Ended
Sep. 30, 2018
Debt Disclosure [Abstract]
Debt Financing	Debt Financing On June 16, 2017, the Company amended its existing U.S. Domestic credit facility with JPM Chase to extend the maturity date to June 28, 2019. There are no financial covenants set forth in this amendment to the Facility. The amount of credit available to the Company under the Facility is $5,000 and will remain as such until the Maturity Date of the Facility on June 28, 2019. During the entire period of the Facility the Company must maintain sufficient cash balances in a segregated deposit account equal to the amount of the Facility and has fully pledged such cash as collateral to the bank to support the credit available to the Company under the Facility. As of September 30, 2018 and December 31, 2017, there were no outstanding borrowings on the credit facility. On January 10, 2018, the Company amended its existing U.S. Domestic credit facility with JPM Chase to increase the credit available under the Facility by $500 to $5,500 from the effective date of the amendment to August 31, 2018. On September 17, 2018, the Company amended its existing U.S. Domestic credit facility with JPM Chase to increase the credit available under the Facility by $500 to $5,500 from the effective date of the amendment to December 31, 2018. On October 19, 2018, the Company amended its existing U.S. Domestic credit facility with JPM Chase to increase the credit available under the Facility by $500 to $5,500 from the effective date of the amendment through the maturity date of June 28, 2019. The Company must maintain an additional $500 in a segregated deposit account and has fully pledged such incremental cash as collateral to the bank to support the credit available to the Company through the maturity date of June 28, 2019. There were no other modifications to the terms of the Facility from the amendment of the facility on June 16, 2017. At September 30, 2018 and December 31, 2017, the Company had outstanding standby letters of credit and bank guarantees totaling approximately $5,053 and $3,004, respectively, under the Facility in connection with contracts in process. Fuel Tech is committed to reimbursing the issuing bank for any payments made by the bank under these instruments. The Company pays a commitment fee of 0.25% per year on the unused portion of the revolving credit facility. At September 30, 2018 and December 31, 2017, approximately $447 and $1,996 was available for future borrowings under the Facility. On June 29, 2018, Beijing Fuel Tech Environmental Technologies Company, Ltd. (Beijing Fuel Tech), a wholly-owned subsidiary of Fuel Tech, entered into a new revolving credit facility (the China Facility) agreement with JPM Chase for RMB 5.25 million (approximately $765), which expires on June 30, 2019. The current facility for Beijing Fuel Tech is also secured by cash held by the Company of $1,020 in a separate restricted use designated JPM Chase deposit account. The Company intends to renew the China Facility at its maturity. The facility is unsecured, bears interest at a rate of 140% of the People’s Bank of China (PBOC) Base Rate, and is guaranteed by Fuel Tech. Beijing Fuel Tech can use this facility for cash advances and bank guarantees. As of September 30, 2018 and December 31, 2017, Beijing Fuel Tech had no cash borrowings under the China Facility. On October 19, 2018, Beijing Fuel Tech amended its existing revolving credit facility (the China Facility) agreement with JPM Chase to reduce the credit available to RMB 2.625 million (approximately $383), which expires on June 30, 2019. The facility for Beijing Fuel Tech is also secured by cash held by the Company of $520 in a separate restricted use designated JPM Chase deposit account. At September 30, 2018 and December 31, 2017, the Company had outstanding standby letters of credit and bank guarantees totaling approximately $0 and $246, respectively, on its Beijing Fuel Tech revolving credit facility in connection with contracts in process. At September 30, 2018 and December 31, 2017, approximately $765 and $753 was available for future borrowings. In the event of default on either the domestic facility or the China facility, the cross default feature in each allows the lending bank to accelerate the payments of any amounts outstanding and may, under certain circumstances, allow the bank to cancel the facility. If the Company were unable to obtain a waiver for a breach of covenant and the bank accelerated the payment of any outstanding amounts, such acceleration may cause the Company’s cash position to deteriorate or, if cash on hand were insufficient to satisfy the payment due, may require the Company to obtain alternate financing to satisfy the accelerated payment.

Debt Financing

On June 16, 2017, the Company amended its existing U.S. Domestic credit facility with JPM Chase to extend the maturity date to June 28, 2019. There are no financial covenants set forth in this amendment to the Facility. The amount of credit available to the Company under the Facility is $5,000 and will remain as such until the Maturity Date of the Facility on June 28, 2019. During the entire period of the Facility the Company must maintain sufficient cash balances in a segregated deposit account equal to the amount of the Facility and has fully pledged such cash as collateral to the bank to support the credit available to the Company under the Facility. As of September 30, 2018 and December 31, 2017, there were no outstanding borrowings on the credit facility.

On January 10, 2018, the Company amended its existing U.S. Domestic credit facility with JPM Chase to increase the credit available under the Facility by $500 to $5,500 from the effective date of the amendment to August 31, 2018. On September 17, 2018, the Company amended its existing U.S. Domestic credit facility with JPM Chase to increase the credit available under the Facility by $500 to $5,500 from the effective date of the amendment to December 31, 2018. On October 19, 2018, the Company amended its existing U.S. Domestic credit facility with JPM Chase to increase the credit available under the Facility by $500 to $5,500 from the effective date of the amendment through the maturity date of June 28, 2019. The Company must maintain an additional $500 in a segregated deposit account and has fully pledged such incremental cash as collateral to the bank to support the credit available to the Company through the maturity date of June 28, 2019. There were no other modifications to the terms of the Facility from the amendment of the facility on June 16, 2017.

At September 30, 2018 and December 31, 2017, the Company had outstanding standby letters of credit and bank guarantees totaling approximately $5,053 and $3,004, respectively, under the Facility in connection with contracts in process. Fuel Tech is committed to reimbursing the issuing bank for any payments made by the bank under these instruments. The Company pays a commitment fee of 0.25% per year on the unused portion of the revolving credit facility. At September 30, 2018 and December 31, 2017, approximately $447 and $1,996 was available for future borrowings under the Facility.

On June 29, 2018, Beijing Fuel Tech Environmental Technologies Company, Ltd. (Beijing Fuel Tech), a wholly-owned subsidiary of Fuel Tech, entered into a new revolving credit facility (the China Facility) agreement with JPM Chase for RMB 5.25 million (approximately $765), which expires on June 30, 2019. The current facility for Beijing Fuel Tech is also secured by cash held by the Company of $1,020 in a separate restricted use designated JPM Chase deposit account. The Company intends to renew the China Facility at its maturity. The facility is unsecured, bears interest at a rate of 140% of the People’s Bank of China (PBOC) Base Rate, and is guaranteed by Fuel Tech. Beijing Fuel Tech can use this facility for cash advances and bank guarantees. As of September 30, 2018 and December 31, 2017, Beijing Fuel Tech had no cash borrowings under the China Facility.

On October 19, 2018, Beijing Fuel Tech amended its existing revolving credit facility (the China Facility) agreement with JPM Chase to reduce the credit available to RMB 2.625 million (approximately $383), which expires on June 30, 2019. The facility for Beijing Fuel Tech is also secured by cash held by the Company of $520 in a separate restricted use designated JPM Chase deposit account.

At September 30, 2018 and December 31, 2017, the Company had outstanding standby letters of credit and bank guarantees totaling approximately $0 and $246, respectively, on its Beijing Fuel Tech revolving credit facility in connection with contracts in process. At September 30, 2018 and December 31, 2017, approximately $765 and $753 was available for future borrowings.

In the event of default on either the domestic facility or the China facility, the cross default feature in each allows the lending bank to accelerate the payments of any amounts outstanding and may, under certain circumstances, allow the bank to cancel the facility. If the Company were unable to obtain a waiver for a breach of covenant and the bank accelerated the payment of any outstanding amounts, such acceleration may cause the Company’s cash position to deteriorate or, if cash on hand were insufficient to satisfy the payment due, may require the Company to obtain alternate financing to satisfy the accelerated payment.