Note 6 - Loans (Details) - Allowance for Credit Losses and Recorded Investment in Financing Receivables (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2015	Dec. 31, 2014
ALLL:
Beginning balance	$ 10,820	$ 14,172
Ending balance	11,296	10,820
Charge offs	(179)	(7,319)
Recoveries	655	792
Provision		3,175
Allowance for credit losses: individually evaluated for impairment	1,532	1,556
Allowance for credit losses: collectively evaluated for impairment	9,764	9,264
Financing receivables:
Financing receivables	699,229	660,898
Financing receivables: individually evaluated for impairment	27,735	31,408
Financing receivables: collectively evaluated for impairment	671,494	629,490
Commercial Portfolio Segment [Member]
ALLL:
Beginning balance	3,552	7,057
Ending balance	3,526	3,552
Charge offs	(52)	(4,242)
Recoveries	26	582
Provision		155
Allowance for credit losses: individually evaluated for impairment	247	314
Allowance for credit losses: collectively evaluated for impairment	3,279	3,238
Financing receivables:
Financing receivables	153,044	153,957
Financing receivables: individually evaluated for impairment	4,913	6,597
Financing receivables: collectively evaluated for impairment	148,131	147,360
Commercial Real Estate Portfolio Segment [Member]
ALLL:
Beginning balance	4,825	2,784
Ending balance	5,419	4,825
Charge offs		(2,699)
Recoveries	594	1
Provision		4,739
Allowance for credit losses: individually evaluated for impairment	415	432
Allowance for credit losses: collectively evaluated for impairment	5,004	4,393
Financing receivables:
Financing receivables	391,790	360,602
Financing receivables: individually evaluated for impairment	10,229	11,753
Financing receivables: collectively evaluated for impairment	381,561	348,849
Consumer Portfolio Segment [Member]
ALLL:
Beginning balance	450	35
Ending balance	338	450
Charge offs	(112)	(2)
Provision		417
Allowance for credit losses: individually evaluated for impairment	14	15
Allowance for credit losses: collectively evaluated for impairment	324	435
Financing receivables:
Financing receivables	44,298	35,372
Financing receivables: individually evaluated for impairment	34	35
Financing receivables: collectively evaluated for impairment	44,264	35,337
Residential Portfolio Segment [Member]
ALLL:
Beginning balance	1,671	2,493
Ending balance	1,691	1,671
Charge offs	(15)	(376)
Recoveries	35	209
Provision		(655)
Allowance for credit losses: individually evaluated for impairment	856	795
Allowance for credit losses: collectively evaluated for impairment	835	876
Financing receivables:
Financing receivables	110,097	110,967
Financing receivables: individually evaluated for impairment	12,559	13,023
Financing receivables: collectively evaluated for impairment	97,538	97,944
Unallocated Financing Receivables [Member]
ALLL:
Beginning balance		1,803
Ending balance	322	322
Provision		(1,481)
Allowance for credit losses: collectively evaluated for impairment	$ 322	$ 322

Name:	boch_AlllAbstract
Namespace Prefix:	boch_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Financing receivable allowance for credit losses, provision.

+ References

No definition available.

+ Details

Name:	boch_FinancingReceivableAllowanceForCreditLossesProvision
Namespace Prefix:	boch_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	boch_FinancingReceivablesAbstract
Namespace Prefix:	boch_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

A valuation allowance for financing receivables that are expected to be uncollectible.

+ References

Reference 1: 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=35738203&loc=SL6953423-111524

+ Details

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

- Definition

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

+ References

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=35738203&loc=SL6953423-111524

+ Details

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

- Definition

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

+ References

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=35738203&loc=SL6953423-111524

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of recovery of financing receivables doubtful of collection that were previously charged off.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

-Subparagraph (c)(4)

-URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953423-111524

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of direct write-downs of financing receivables charged against the allowance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

-Subparagraph (c)(3)

-URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953423-111524

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The balance of financing receivables that were collectively evaluated for impairment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

-Subparagraph (h)

-URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953423-111524

+ Details

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

- Definition

The balance of financing receivables that were individually evaluated for impairment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

-Subparagraph (h)

-URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953423-111524

+ Details

Name:	us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

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=28367877&loc=d3e4428-111522

+ Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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