Earnings Per Share (Schedule of Earnings Per Share, Basic and Diluted) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator for both basic and diluted earnings per share:
Net income (loss) attributable to Hallmark Financial Services, Inc.									$ (11,553)	$ 6,526	$ 21,863
Denominator, basic shares									18,343	18,780	19,211
Effect of dilutive securities:
Stock-based compensation awards										161	194
Denominator, diluted shares									18,343	18,941	19,405
Basic earnings per share: (in dollars per share)	$ (0.59)	$ (0.09)	$ (0.18)	$ 0.21	$ (0.20)	$ 0.27	$ 0.06	$ 0.21	$ (0.63)	$ 0.35	$ 1.14
Diluted earnings per share: (in dollars per share)	$ (0.59)	$ (0.09)	$ (0.18)	$ 0.21	$ (0.20)	$ 0.27	$ 0.06	$ 0.21	$ (0.63)	$ 0.34	$ 1.13