United Security Bancshares, Inc. (Parent Company Only) Financial Information - Statements of Cash Flows (Detail) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net income	$ 3,549,000us-gaap_ProfitLoss	$ 3,927,000us-gaap_ProfitLoss
Adjustments to reconcile net income to net cash provided by operating activities:
Net cash provided by (used in) operating activities	8,563,000	10,923,000
Cash flows from financing activities:
Dividends paid	(181,000)us-gaap_PaymentsOfDividends	0us-gaap_PaymentsOfDividends
Net cash used in financing activities	(1,596,000)	838,000
Decrease in cash	(13,554,000)	(6,406,000)
Cash and cash equivalents, beginning of period	47,720,000	54,126,000
Cash and cash equivalents, end of period	34,166,000	47,720,000
United Security Bancshares, Inc. [Member]
Cash flows from operating activities:
Net income	3,549,000	3,927,000
Adjustments to reconcile net income to net cash provided by operating activities:
Distributions in excess of undistributed income (loss) of subsidiaries	(3,539,000)	(4,055,000)
Change in other assets and liabilities	162,000	118,000
Net cash provided by (used in) operating activities	172,000	(10,000)
Cash flows from financing activities:
Dividends paid	(181,000)
Net cash used in financing activities	(181,000)
Decrease in cash	(9,000)	(10,000)
Cash and cash equivalents, beginning of period	73,000	83,000
Cash and cash equivalents, end of period	$ 64,000	$ 73,000

Distributions in excess of undistributed income (loss) of subsidiaries.

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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