Schedule II. Condensed Financial Statements of Parent Company (Condensed Statement of Cash Flows) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities
Net income	$ 51,023	$ 49,904	$ 89,126
Adjustments to reconcile net income to net cash provided by operating activities
Other, net	3,378	(9,943)	(2,914)
Total adjustments	125,224	165,266	104,679
Net cash provided by operating activities	170,094	214,384	189,999
Cash flows from investing activities
Proceeds from maturity of held-to-maturity investments	150	493	105
Purchase of held-to-maturity investments	(150)	(42)	(450)
Net cash used in investing activities	(61,985)	(112,403)	(36,286)
Cash flows from financing activities
Repurchase of common stock	(29,784)	(3,746)	(2,423)
Issuance of common stock	4,828	9,922	5,496
Tax impact from issuance of common stock	0	(816)	(833)
Net cash used in financing activities	(107,549)	(97,577)	(137,837)
Net Change in Cash and Cash Equivalents	560	4,404	15,876
Cash and Cash Equivalents at Beginning of Year - Continuing Operations	89,194	89,496	66,718
Cash and Cash Equivalents at End of Year - Continuing Operations	95,562	89,194	89,496
United Fire Group, Inc.
Cash flows from operating activities
Net income	51,023	49,904	89,126
Adjustments to reconcile net income to net cash provided by operating activities
Equity in net income of subsidiary	(49,933)	(49,908)	(89,175)
Dividends received from subsidiary	40,000	24,000	22,500
Other, net	1,415	2,995	1,269
Total adjustments	(8,518)	(22,913)	(65,406)
Net cash provided by operating activities	42,505	26,991	23,720
Cash flows from investing activities
Proceeds from maturity of held-to-maturity investments	150	0	0
Purchase of held-to-maturity investments	(150)	0	0
Net cash used in investing activities	0	0	0
Cash flows from financing activities
Payment of cash dividends	(27,337)	(24,591)	(21,658)
Repurchase of common stock	(29,784)	(3,746)	(2,423)
Issuance of common stock	4,828	9,922	5,496
Tax impact from issuance of common stock	0	(816)	(833)
Net cash used in financing activities	(52,293)	(19,231)	(19,418)
Net Change in Cash and Cash Equivalents	(9,788)	7,760	4,302
Cash and Cash Equivalents at Beginning of Year - Continuing Operations	14,325	6,565	2,263
Cash and Cash Equivalents at End of Year - Continuing Operations	$ 4,537	$ 14,325	$ 6,565