Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2021	Aug. 04, 2021
Cover page.
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2021
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Document Transition Report	false
Entity File Number	000-20908
Entity Registrant Name	PREMIER FINANCIAL BANCORP, INC.
Entity Central Index Key	0000887919
Entity Incorporation, State or Country Code	KY
Entity Tax Identification Number	61-1206757
Entity Address, Address Line One	2883 Fifth Avenue
Entity Address, City or Town	Huntington
Entity Address, State or Province	WV
Entity Address, Postal Zip Code	25702
City Area Code	304
Local Phone Number	525-1600
Title of 12(b) Security	Common Stock, no par value
Trading Symbol	PFBI
Security Exchange Name	NASDAQ
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		14,805,095