United Security Bancshares, Inc. (Parent Company Only) Financial Information - Statements of Income (Detail) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 12 Months Ended
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2012
Sep. 30, 2012
Jun. 30, 2012
Mar. 31, 2012
Dec. 31, 2013
Dec. 31, 2012
INCOME:                    
NET INCOME $ 955 $ 904 $ 1,182 $ 886 $ 883 $ 1,179 $ 1,370 $ (1,237) $ 3,927 $ 2,195
United Security Bancshares, Inc. [Member]
                   
INCOME:                    
Dividend income, First United Security Bank                 200  
Other Income                 6  
Total income                 206  
EXPENSE:                 334 383
LOSS BEFORE EQUITY IN UNDISTRIBUTED INCOME OF SUBSIDIARIES                 (128) (383)
EQUITY IN UNDISTRIBUTED INCOME OF SUBSIDIARIES                 4,055 2,578
NET INCOME                 $ 3,927 $ 2,195