Cover Page - shares	9 Months Ended
	Sep. 30, 2020	Nov. 03, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	001-36522
Entity Registrant Name	Investar Holding Corp
Entity Incorporation, State or Country Code	LA
Entity Tax Identification Number	27-1560715
Entity Address, Address Line One	10500 Coursey Boulevard
Entity Address, City or Town	Baton Rouge
Entity Address, State or Province	LA
Entity Address, Postal Zip Code	70816
City Area Code	225
Local Phone Number	227-2222
Title of 12(b) Security	Common stock, $1.00 par value per share
Trading Symbol	ISTR
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		10,622,068
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001602658
Current Fiscal Year End Date	--12-31