United Security Bancshares, Inc. (Parent Company Only) Financial Information - Statements of Cash Flows (Detail) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 12 Months Ended
Dec. 31, 2013
Mar. 31, 2013
Dec. 31, 2012
Mar. 31, 2012
Dec. 31, 2013
Dec. 31, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:            
Net income $ 955 $ 886 $ 883 $ (1,237) $ 3,927 $ 2,195
Adjustments to reconcile net income to net cash provided by operating activities:            
Decrease in other assets         1,588 429
(Increase) decrease in other liabilities         2,095 937
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS         (6,406) 1,330
CASH AND CASH EQUIVALENTS, beginning of year   54,126   52,796 54,126 52,796
CASH AND CASH EQUIVALENTS, end of year 47,720   54,126   47,720 54,126
United Security Bancshares, Inc. [Member]
           
CASH FLOWS FROM OPERATING ACTIVITIES:            
Net income         3,927 2,195
Adjustments to reconcile net income to net cash provided by operating activities:            
Distributions in excess of undistributed income (loss) of subsidiaries         (4,055) (2,578)
Decrease in other assets         131 110
(Increase) decrease in other liabilities         (13) 65
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS         (10) (208)
CASH AND CASH EQUIVALENTS, beginning of year   83   291 83 291
CASH AND CASH EQUIVALENTS, end of year $ 73   $ 83   $ 73 $ 83