Schedule II. Condensed Financial Statements of Parent Company (Condensed Balance Sheet) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assets
Fixed maturities, held-to-maturity, at amortized cost (fair value $150 in 2017 and $150 in 2016)	$ 150	$ 150
Cash and cash equivalents	95,562	89,194	$ 89,496	$ 66,718
Federal income tax receivable	6,031	14,285
Accrued investment income	13,841	13,617
Total assets	4,183,431	4,054,758
Liabilities and stockholders' equity
Liabilities	3,210,058	3,112,874
Stockholders' equity
Common stock, $0.001 par value, authorized 75,000,000 shares; 24,916,806 and 25,429,769 issued and outstanding in 2017 and 2016, respectively	25	25
Additional paid-in capital	196,334	216,482
Retained earnings	608,700	616,322
Accumulated other comprehensive income, net of tax	168,314	109,055
Total stockholders' equity	973,373	941,884	878,897	817,415
Total liabilities and stockholders' equity	4,183,431	4,054,758
United Fire Group, Inc.
Assets
Fixed maturities, held-to-maturity, at amortized cost (fair value $150 in 2017 and $150 in 2016)	150	150
Investment in subsidiary	967,590	925,887
Cash and cash equivalents	4,537	14,325	$ 6,565	$ 2,263
Federal income tax receivable	1,095	1,521
Accrued investment income	1	1
Total assets	973,373	941,884
Liabilities and stockholders' equity
Liabilities	0	0
Stockholders' equity
Common stock, $0.001 par value, authorized 75,000,000 shares; 24,916,806 and 25,429,769 issued and outstanding in 2017 and 2016, respectively	25	25
Additional paid-in capital	196,334	216,482
Retained earnings	608,700	616,322
Accumulated other comprehensive income, net of tax	168,314	109,055
Total stockholders' equity	973,373	941,884
Total liabilities and stockholders' equity	$ 973,373	$ 941,884