Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	May 09, 2018
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		24,167,679
Amendment Flag	false
Entity Central Index Key	0000846913
Entity Filer Category	Smaller Reporting Company
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus (Q1,Q2,Q3,FY)	Q1