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, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues
Investment income									$ 100,781	$ 104,609	$ 112,799
Total revenues	$ 275,956	$ 264,560	$ 255,918	$ 238,484	$ 250,452	$ 235,865	$ 232,673	$ 222,904	1,034,918	941,894	877,042
Expenses
Net income	$ 30,895	$ 19,534	$ 15,018	$ 23,679	$ 34,796	$ 325	$ 10,685	$ 13,331	89,126	59,137	76,140
Other comprehensive income (loss)
Change in unrealized appreciation on investments held by subsidiary									(28,185)	55,888	(35,489)
Change in liability for underfunded employee benefit plans									8,714	(47,685)	24,066
Other comprehensive income (loss), before tax and reclassification adjustments									(19,471)	8,203	(11,423)
Income tax effect									6,814	(2,871)	3,998
Other comprehensive income (loss), after tax, before reclassification adjustments									(12,657)	5,332	(7,425)
Reclassifications for unrealized net gains on available-for-sale securities									(4,513)	(5,085)	(6,812)
Reclassification adjustment for employee benefit costs included in expense									7,468	3,072	5,868
Total reclassification adjustments, before tax									2,955	(2,013)	(944)
Income tax effect									(1,034)	704	331
Total reclassification adjustments, after tax									1,921	(1,309)	(613)
Comprehensive income									78,390	63,160	68,102
United Fire Group, Inc. [Member]
Revenues
Investment income									25	22	23
Total revenues									25	22	23
Expenses
Other operating expenses									116	297	172
Total expenses									116	297	172
Income before income taxes									(91)	(275)	(149)
Federal income tax benefit									(42)	(107)	(49)
Net loss before equity in net income of subsidiary									(49)	(168)	(100)
Equity in net income of subsidiary									89,175	59,305	76,240
Net income									89,126	59,137	76,140
Other comprehensive income (loss)
Change in unrealized appreciation on investments held by subsidiary									(28,185)	55,888	(35,489)
Change in liability for underfunded employee benefit plans									8,714	(47,685)	24,066
Other comprehensive income (loss), before tax and reclassification adjustments									(19,471)	8,203	(11,423)
Income tax effect									6,814	(2,871)	3,998
Other comprehensive income (loss), after tax, before reclassification adjustments									(12,657)	5,332	(7,425)
Reclassifications for unrealized net gains on available-for-sale securities									(4,513)	(5,085)	(6,812)
Reclassification adjustment for employee benefit costs included in expense									7,468	3,072	5,868
Total reclassification adjustments, before tax									2,955	(2,013)	(944)
Income tax effect									(1,034)	704	331
Total reclassification adjustments, after tax									1,921	(1,309)	(613)
Comprehensive income									$ 78,390	$ 63,160	$ 68,102