Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB Topic 6.L.1)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74567-122707

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544

+ Details

Name:	us-gaap_LoansAndLeasesReceivableAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of deferred interest and fee income, unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of acquired loans. Excludes amounts for loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 20
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=65890831&loc=d3e10152-111534

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5074-111524

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 30
-Section 50
-Paragraph 4
-Subparagraph (a)(4)
-URI http://asc.fasb.org/extlink&oid=25496975&loc=d3e45377-112738

+ Details

Name:	us-gaap_LoansAndLeasesReceivableDeferredIncome
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

+ Details

Name:	us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=65884687&loc=d3e4428-111522

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_LoansAndLeasesReceivableNetReportedAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=usbi_RealEstate1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=usbi_ConstructionLandDevelopmentAndOtherLandLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=usbi_FirstUnitedSecurityBankMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=usbi_AcceptanceLoanCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=usbi_SecuredBy1To4FamilyResidentialPropertiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=usbi_SecuredByMultifamilyResidentialPropertiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=usbi_SecuredByNonfarmNonresidentialPropertiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=usbi_OtherRealEstateLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=usbi_CommercialAndIndustrialLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=usbi_OtherLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Note 6 - Loans and Allowance for Loan Losses - Loan Portfolio By Reporting Segment and Portfolio Segment (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Real Estate [Member] \| Construction, Land Development and Other Land Loans [Member] \| FUSB [Member]
Total loans	$ 18,023	$ 11,827
Real Estate [Member] \| Construction, Land Development and Other Land Loans [Member] \| ALC [Member]
Total loans
Real Estate [Member] \| Construction, Land Development and Other Land Loans [Member]
Total loans	$ 18,023	$ 11,827
Real Estate [Member] \| Secured by 1-4 Family Residential Properties [Member] \| FUSB [Member]
Total loans	30,623	30,730
Real Estate [Member] \| Secured by 1-4 Family Residential Properties [Member] \| ALC [Member]
Total loans	16,265	17,233
Real Estate [Member] \| Secured by 1-4 Family Residential Properties [Member]
Total loans	46,888	47,963
Real Estate [Member] \| Secured by Multi-family Residential Properties [Member] \| FUSB [Member]
Total loans	$ 11,580	$ 11,845
Real Estate [Member] \| Secured by Multi-family Residential Properties [Member] \| ALC [Member]
Total loans
Real Estate [Member] \| Secured by Multi-family Residential Properties [Member]
Total loans	$ 11,580	$ 11,845
Real Estate [Member] \| Secured by Non-farm, Non-residential Properties [Member] \| FUSB [Member]
Total loans	$ 82,754	$ 83,883
Real Estate [Member] \| Secured by Non-farm, Non-residential Properties [Member] \| ALC [Member]
Total loans
Real Estate [Member] \| Secured by Non-farm, Non-residential Properties [Member]
Total loans	$ 82,754	$ 83,883
Real Estate [Member] \| Other Real Estate Loans [Member] \| FUSB [Member]
Total loans	$ 168	$ 115
Real Estate [Member] \| Other Real Estate Loans [Member] \| ALC [Member]
Total loans
Real Estate [Member] \| Other Real Estate Loans [Member]
Total loans	$ 168	$ 115
Commercial and Industrial Loans [Member] \| FUSB [Member]
Total loans	$ 34,568	$ 29,377
Commercial and Industrial Loans [Member] \| ALC [Member]
Total loans
Commercial and Industrial Loans [Member]
Total loans	$ 34,568	$ 29,377
Consumer Portfolio Segment [Member] \| FUSB [Member]
Total loans	6,614	7,057
Allowance for loan losses	22	28		$ 114
Consumer Portfolio Segment [Member] \| ALC [Member]
Total loans	74,669	76,131
Allowance for loan losses	2,111	2,202		$ 2,336
Consumer Portfolio Segment [Member]
Total loans	81,283	83,188
Other Loans [Member] \| FUSB [Member]
Total loans	407	379
Allowance for loan losses	$ 5	$ 14
Other Loans [Member] \| ALC [Member]
Total loans
Allowance for loan losses
Other Loans [Member]
Total loans	$ 407	$ 379
FUSB [Member]
Total loans	184,737	175,213
Less: Unearned interest, fees and deferred cost	174	149
Allowance for loan losses	1,068	1,329		$ 3,486
Net loans	183,495	173,735	$ 231,778
ALC [Member]
Total loans	90,934	93,364
Less: Unearned interest, fees and deferred cost	8,147	9,215
Allowance for loan losses	2,307	2,452		$ 2,682
Net loans	80,480	81,697	70,786
Total loans	275,671	268,577
Less: Unearned interest, fees and deferred cost	8,321	9,364
Allowance for loan losses	3,375	3,781
Net loans	$ 263,975	$ 255,432	$ 239,218