Schedule II - Condensed Financial Information of Registrant (Parent Company Only) (Statements of Operations) (Details) - USD ($) $ 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
Investment loss, net of expenses									$ 18,874	$ 16,342	$ 13,969
Management fee income									3,867	4,977	5,952
Total revenues	$ 97,375	$ 97,723	$ 93,475	$ 96,948	$ 97,254	$ 97,618	$ 91,052	$ 90,028	385,521	375,952	372,402
Interest expense									4,512	4,549	3,906
Amortization of intangible assets									2,468	2,468	2,468
Loss before equity in undistributed earnings (loss) of subsidiaries and income tax benefit	(15,967)	(1,525)	(4,918)	5,838	(6,174)	7,176	1,487	5,989	(16,572)	8,478	31,886
Income tax benefit	$ (5,338)	$ 35	$ (1,568)	$ 1,852	$ (2,512)	$ 2,128	$ 421	$ 1,915	(5,019)	1,952	10,023
Net income (loss) attributable to Hallmark Financial Services, Inc.									(11,553)	6,526	21,863
Parent Company [Member]
Investment loss, net of expenses									210	70	120
Dividend income from subsidiaries									11,375	10,500	8,000
Management fee income									11,896	10,711	10,053
Total revenues									22,722	21,281	18,173
Operating expenses									10,265	9,878	10,222
Interest expense									4,512	4,549	3,906
Operating Costs and Expenses									14,777	14,427	14,128
Loss before equity in undistributed earnings (loss) of subsidiaries and income tax benefit									7,945	6,854	4,045
Income tax benefit									(947)	(1,315)	(1,273)
Income (loss) before equity in undistributed earnings of subsidiaries									8,892	8,169	5,318
Equity in undistributed share of earnings (loss) in subsidiaries									(20,445)	(1,643)	16,545
Net income (loss) attributable to Hallmark Financial Services, Inc.									(11,553)	6,526	21,863
Comprehensive income (loss)									$ (9,690)	$ 9,479	$ 11,480