Document And Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Oct. 15, 2021
Document Information [Line Items]
Entity Central Index Key	0000045919
Entity Registrant Name	HARTE HANKS INC
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	Q3
Document Fiscal Year Focus	2021
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	001-07120
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	74-1677284
Entity Address, Address Line One	2800 Wells Branch Parkway
Entity Address, City or Town	Austin
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	78728
City Area Code	512
Local Phone Number	434-1100
Title of 12(b) Security	Common Stock
Trading Symbol	HRTH
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		6,976,144