Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Mar. 15, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2020
Entity File Number	001-11252
Entity Registrant Name	Hallmark Financial Services, Inc.
Entity Incorporation, State or Country Code	NV
Entity Tax Identification Number	87-0447375
Entity Address, Address Line One	5420 Lyndon B. Johnson Freeway, Suite 1100
Entity Address, City or Town	Dallas
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	75240
City Area Code	817
Local Phone Number	348-1600
Title of 12(b) Security	Common Stock
Trading Symbol	HALL
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
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
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 45.2
Entity Common Stock, Shares Outstanding		18,142,158
Entity Central Index Key	0000819913
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false