Document and Entity Information	9 Months Ended
	Sep. 30, 2013	Nov. 07, 2013
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2013
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q3
Entity Registrant Name	FORRESTER RESEARCH, INC.
Entity Central Index Key	0001023313
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		19,753,000