Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Oct. 31, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	FUEL TECH, INC.
Document Type	10-Q
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding		24,132,910
Amendment Flag	false
Entity Central Index Key	0000846913
Entity Filer Category	Smaller Reporting Company
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus (Q1,Q2,Q3,FY)	Q3