Financing receivable acquired with credit deterioration.

No definition available.

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Namespace Prefix:	civb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of allowance for credit loss on accounts receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=121611835&loc=d3e5074-111524

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121599878&loc=SL82895884-210446

+ Details

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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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953423-111524

+ Details

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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

+ Details

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

- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=121611835&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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953423-111524

+ Details

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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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=121593590&loc=d3e4428-111522

+ Details

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

- Details

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Balance Type:
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- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=civb_CommercialAndAgricultureMember
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Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=civb_CommercialRealEstateNonOwnerOccupiedMember
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialPortfolioSegmentMember
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=civb_RealEstateConstructionMember
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Period Type:

- Details

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

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=civb_ConsumerAndOtherMember
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Data Type:	na
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- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_UnallocatedFinancingReceivablesMember
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Allowance for Loan Losses - Ending Allocation of Allowance for Loan Losses and Loan Balances Outstanding (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses, Individually evaluated for impairment	$ 26		$ 107
Allowance for loan losses, Collectively evaluated for impairment	26,171		24,921
Allowance for loan losses, Total	26,197	$ 26,133	25,028	$ 20,420	$ 16,948	$ 14,767
Outstanding loan balances, Individually evaluated for impairment	1,478		2,666
Outstanding loan balances, Collectively evaluated for impairment	2,017,339		2,054,448
Outstanding loan balances, Total	2,019,196		2,057,502
Receivables Acquired with Deteriorated Credit Quality [Member]
Accounts Notes And Loans Receivable [Line Items]
Loan balance of loans acquired with credit deterioration	379		388
Commercial and Agriculture [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses, Individually evaluated for impairment			73
Allowance for loan losses, Collectively evaluated for impairment	2,320		2,737
Allowance for loan losses, Total	2,320	2,360	2,810	2,799	2,400	2,219
Outstanding loan balances, Individually evaluated for impairment			74
Outstanding loan balances, Collectively evaluated for impairment	328,871		409,802
Outstanding loan balances, Total	328,871		409,876
Commercial Real Estate Owner Occupied [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses, Individually evaluated for impairment	8		5
Allowance for loan losses, Collectively evaluated for impairment	4,019		4,052
Allowance for loan losses, Total	4,027	4,049	4,057	3,411	2,810	2,541
Outstanding loan balances, Individually evaluated for impairment	299		980
Outstanding loan balances, Collectively evaluated for impairment	271,368		277,433
Outstanding loan balances, Total	271,667		278,413
Commercial Real Estate Non Owner Occupied [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses, Collectively evaluated for impairment	13,546		12,451
Allowance for loan losses, Total	13,546	13,209	12,451	9,169	7,617	6,584
Outstanding loan balances, Individually evaluated for impairment	30		48
Outstanding loan balances, Collectively evaluated for impairment	762,953		705,024
Outstanding loan balances, Total	762,983		705,072
Residential Real Estate [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses, Individually evaluated for impairment	18		29
Allowance for loan losses, Collectively evaluated for impairment	2,513		2,455
Allowance for loan losses, Total	2,531	2,509	2,484	2,434	1,950	1,582
Outstanding loan balances, Individually evaluated for impairment	557		946
Outstanding loan balances, Collectively evaluated for impairment	425,795		441,254
Outstanding loan balances, Total	426,731		442,588
Residential Real Estate [Member] \| Receivables Acquired with Deteriorated Credit Quality [Member]
Accounts Notes And Loans Receivable [Line Items]
Loan balance of loans acquired with credit deterioration	379		388
Real Estate Construction [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses, Collectively evaluated for impairment	2,177		2,439
Allowance for loan losses, Total	2,177	2,902	2,439	1,844	1,606	1,250
Outstanding loan balances, Collectively evaluated for impairment	188,368		175,609
Outstanding loan balances, Total	188,368		175,609
Farm Real Estate [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses, Collectively evaluated for impairment	290		338
Allowance for loan losses, Total	290	283	338	361	310	344
Outstanding loan balances, Individually evaluated for impairment	592		618
Outstanding loan balances, Collectively evaluated for impairment	28,024		32,484
Outstanding loan balances, Total	28,616		33,102
Consumer and Other [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses, Collectively evaluated for impairment	202		209
Allowance for loan losses, Total	202	170	209	247	246	$ 247
Outstanding loan balances, Collectively evaluated for impairment	11,960		12,842
Outstanding loan balances, Total	11,960		12,842
Unallocated [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses, Collectively evaluated for impairment	1,104		240
Allowance for loan losses, Total	$ 1,104	$ 651	$ 240	$ 155	$ 9