Schedule II. Condensed Financial Statements of Parent Company (Condensed Balance Sheets) (Phantom) (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Condensed Balance Sheet Statements, Captions [Line Items]
Fixed maturities, Available-for-sale securities, amortized cost	$ 1,659,760	$ 1,761,289
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)	25,015,963	25,097,408
Common stock, shares outstanding (in shares)	25,015,963	25,097,408
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)	25,015,963	25,097,408
Common stock, shares outstanding (in shares)	25,015,963	25,097,408