Number of days for demand deposits with financial institutions to be considered cash and cash equivalent.

No definition available.

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Namespace Prefix:	civb_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Par value of Federal Home Loan Bank Stock.

+ References

No definition available.

+ Details

Name:	civb_FederalHomeLoanBankCapitalStockParValue
Namespace Prefix:	civb_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Minimum balance requirement to perform detailed loan review.

+ References

No definition available.

+ Details

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

- Definition

New accounting pronouncement or change in accounting principle cumulative effect of change in retained earnings and accumulated other comprehensive income.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage of impact on assets due to new accounting standard updates.

+ References

No definition available.

+ Details

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

- Definition

Percentage of impact on liabilities due to new accounting standard updates.

+ References

No definition available.

+ Details

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

- Definition

Percentage of insurance commission revenue of total revenue.

+ References

No definition available.

+ Details

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

- Definition

Represents the number of days past due for loans and leases to be considered nonaccrual.

+ References

No definition available.

+ Details

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Namespace Prefix:	civb_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of days secured residential real estate loans are past due to receive an assessment of value.

+ References

No definition available.

+ Details

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Namespace Prefix:	civb_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of days unsecured loans are past due to recognize charge off.

+ References

No definition available.

+ Details

Name:	civb_PeriodPastDueLoanChargedOff
Namespace Prefix:	civb_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of days all other loans are past due to recognize an impairment.

+ References

No definition available.

+ Details

Name:	civb_PeriodPastDueLoanChargedToNetRealizableValue
Namespace Prefix:	civb_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Significant Accounting Policies [Line Items]

+ References

No definition available.

+ Details

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Namespace Prefix:	civb_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

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

- Details

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- Details

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- Details

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- Details

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- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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Namespace Prefix:
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- Details

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Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017 USD ($) Segment $ / shares	Dec. 31, 2016	Dec. 31, 2015
Significant Accounting Policies [Line Items]
Allowance for loan losses related to commercial, commercial real estate and farm real estate loans	$ 750,000
Number of days reaching which loans are considered for nonaccrual status	90 days
Federal Home Loan Bank par value \| $ / shares	$ 100
Number of operating segments \| Segment	1
ASU 2018-02 [Member]
Significant Accounting Policies [Line Items]
Cumulative effect adjustment between retained earnings and accumulated other comprehensive income	$ 199,000
Unsecured Debt [Member]
Significant Accounting Policies [Line Items]
Retail loans past due charge off period	90 days
Secured Debt [Member]
Significant Accounting Policies [Line Items]
Residential real estate loans past due assessment of value period	180 days
Other Debt [Member]
Significant Accounting Policies [Line Items]
Loans past due charged down to the net realizable value period	90 days
Maximum [Member]
Significant Accounting Policies [Line Items]
Percentage of insurance commission revenue of total revenue	1.00%	1.00%	1.00%
Original maturities for cash and cash equivalents	90 days
Estimated useful life of intangible assets	12 years
Percentage of increase on assets due to new accounting standard updates	1.00%
Percentage of increase on liabilities due to new accounting standard updates	1.00%
Maximum [Member] \| Furniture and Equipment [Member]
Significant Accounting Policies [Line Items]
Estimated useful life of asset	7 years
Maximum [Member] \| Buildings and Improvements [Member]
Significant Accounting Policies [Line Items]
Estimated useful life of asset	50 years
Maximum [Member] \| WSP [Member]
Significant Accounting Policies [Line Items]
Percentage of insurance commission revenue of total revenue	1.00%	1.00%	1.00%
Maximum [Member] \| CIVB Risk Management, Inc. [Member]
Significant Accounting Policies [Line Items]
Percentage of insurance commission revenue of total revenue	1.00%
Minimum [Member]
Significant Accounting Policies [Line Items]
Estimated useful life of intangible assets	5 years
Minimum [Member] \| Furniture and Equipment [Member]
Significant Accounting Policies [Line Items]
Estimated useful life of asset	3 years
Minimum [Member] \| Buildings and Improvements [Member]
Significant Accounting Policies [Line Items]
Estimated useful life of asset	7 years