Cares act, additional amount of loan funded to replenishment.

No definition available.

Name:	civb_CaresActAdditionalAmountOfLoanFundedToReplenishment
Namespace Prefix:	civb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Cares act, initial amount of loan funded.

+ References

No definition available.

+ Details

Name:	civb_CaresActInitialAmountOfLoanFunded
Namespace Prefix:	civb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Financing receivable modification, percentage of post modification recorded investment performing in accordance with terms.

+ References

No definition available.

+ Details

Name:	civb_FinancingReceivableModificationPercentageOfPostModificationRecordedInvestmentPerformingInAccordanceWithTerms
Namespace Prefix:	civb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Loans and leases receivable amount approved.

+ References

No definition available.

+ Details

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

- Definition

Number of loans approved.

+ References

No definition available.

+ Details

Name:	civb_NumberOfLoansApproved
Namespace Prefix:	civb_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsNumberOfContracts2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after troubled debt restructuring, of modified financing receivable.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis=civb_PaycheckProtectionProgramLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Subsequent Events - Additional Information (Detail) $ in Thousands		3 Months Ended
	May 05, 2020 USD ($) Loan	Mar. 31, 2019 USD ($) Contract	Apr. 24, 2020 USD ($)	Apr. 16, 2020 USD ($)
Subsequent Event [Line Items]
Number of loans modified \| Contract		1
Loan modifications amount		$ 382
Subsequent Event [Member]
Subsequent Event [Line Items]
Number of loans modified \| Loan	653
Loan modifications amount	$ 357,549
Percentage of loan modifications performing in accordance with terms	100.00%
Paycheck Protection Program Loans [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Initial amount of loan funded				$ 349,000,000
Additional round of funding			$ 310,000,000
Number of loans approved \| Loan	2,139
Total loans approved	$ 262,100