Schedule II. Condensed Financial Statements of Parent Company (Condensed Balance Sheets) (Parenthetical) (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Condensed Balance Sheet Statements, Captions [Line Items]
Fixed maturities, Available-for-sale securities, amortized cost	$ 1,720,291	$ 1,659,760
Common stock, par value per share (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	75,000,000	75,000,000
Common stock, shares issued (in shares)	25,055,479	25,015,963
Common stock, shares outstanding (in shares)	25,055,479	25,015,963
United Fire Group, Inc.
Condensed Balance Sheet Statements, Captions [Line Items]
Fixed maturities, Available-for-sale securities, amortized cost	$ 150	$ 150
Common stock, par value per share (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	75,000,000	75,000,000
Common stock, shares issued (in shares)	25,055,479	25,015,963
Common stock, shares outstanding (in shares)	25,055,479	25,015,963