Note 15 - Guarantees, Commitments and Contingencies (Details Textual) - USD ($)	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Securities Committed to Purchase Amount	$ 2,000,000		$ 0
Credit Losses Associated With Derivative Contracts	0	$ 0
Securities Committed to Sell Amount	$ 0		$ 0

Credit losses associated with derivative contracts.

No definition available.

Name:	usbi_CreditLossesAssociatedWithDerivativeContracts
Namespace Prefix:	usbi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration