Schedule II. Condensed Financial Statements of Parent Company (Condensed Statement of Income and Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues
Investment income									$ 60,414	$ 52,894	$ 51,190
Total revenues	$ 293,374	$ 298,055	$ 304,197	$ 305,539	$ 252,062	$ 291,910	$ 275,399	$ 250,795	1,201,165	1,070,166	1,052,737
Expenses
Net income									14,820	27,650	51,023
Other comprehensive income (loss)
Change in unrealized appreciation on investments held by subsidiary									70,127	(50,985)	72,251
Change in liability for underfunded employee benefit plans of subsidiary									(20,924)	25,513	(26,122)
Other comprehensive income (loss), before tax and reclassification adjustments									49,203	(25,472)	46,129
Income tax effect									(10,334)	5,349	(17,540)
Reclassification adjustment for net realized (gains) losses included in income									1,521	784	(6,390)
Reclassification adjustment for employee benefit costs included in expense									4,497	6,642	5,408
Total reclassification adjustments, before tax									6,018	7,426	(982)
Income tax effect									(1,263)	(1,559)	344
Comprehensive income									58,444	13,394	78,974
United Fire Group, Inc.
Revenues
Investment income									295	396	133
Total revenues									295	396	133
Expenses
Other operating expenses									86	95	103
Total expenses									86	95	103
Income (loss) before income taxes and equity in net income of subsidiary									209	301	30
Federal income tax expense (benefit)									44	(1,165)	(1,060)
Net income before equity in net income of subsidiary									165	1,466	1,090
Equity in net income of subsidiary									14,655	26,184	49,933
Net income									14,820	27,650	51,023
Other comprehensive income (loss)
Change in unrealized appreciation on investments held by subsidiary									70,127	(50,985)	72,251
Change in liability for underfunded employee benefit plans of subsidiary									(20,924)	25,513	(26,122)
Other comprehensive income (loss), before tax and reclassification adjustments									49,203	(25,472)	46,129
Income tax effect									(10,334)	5,349	(17,540)
Other comprehensive income (loss), after tax, before reclassification adjustments									38,869	(20,123)	28,589
Reclassification adjustment for net realized (gains) losses included in income									1,521	784	(6,390)
Reclassification adjustment for employee benefit costs included in expense									4,497	6,642	5,408
Total reclassification adjustments, before tax									6,018	7,426	(982)
Income tax effect									(1,263)	(1,559)	344
Total reclassification adjustments, after tax									4,755	5,867	(638)
Comprehensive income									$ 58,444	$ 13,394	$ 78,974