Document and Entity Information - shares	9 Months Ended
	Oct. 02, 2015	Nov. 06, 2015
Document and Entity Information [Abstract]
Entity Registrant Name	HACKETT GROUP, INC.
Entity Central Index Key	0001057379
Document Type	10-Q
Document Period End Date	Oct. 02, 2015
Amendment Flag	false
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--01-01
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		29,382,893