Amount of cash received in conversion of shares.

No definition available.

Name:	civb_AmountOfCashReceivedInConversionOfShares
Namespace Prefix:	civb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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+ Details

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

- Definition

Face amount or stated value per share of common stock.

+ References

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+ Details

Name:	us-gaap_CommonStockParOrStatedValuePerShare
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Value of all classes of common stock held by shareholders. May be all or portion of the number of common shares authorized. These shares exclude common shares repurchased by the entity and held as treasury shares.

+ References

+ Details

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

- Definition

The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

+ References

+ Details

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

- Definition

Including the current and noncurrent portions, aggregate carrying value as of the balance sheet date of loans payable (with maturities initially due after one year or beyond the operating cycle if longer).

+ References

+ Details

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

- Definition

Per share or per unit amount of equity securities issued.

+ References

No definition available.

+ Details

Name:	us-gaap_SharesIssuedPricePerShare
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio applied to the conversion of stock split, for example but not limited to, one share converted to two or two shares converted to one.

+ References

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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

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

Subsequent Events - Additional Information (Detail)	12 Months Ended
Subsequent Events - Additional Information (Detail)	Dec. 31, 2021 USD ($)	Jan. 07, 2022 USD ($) $ / shares	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Subsequent Event [Line Items]
Assets	$ 3,011,983,000			$ 2,768,862,000
Deposits	$ 2,416,701,000			$ 2,189,398,000
Comunibanc And The Henry County Bank [Member]
Subsequent Event [Line Items]
Assets			$ 329,000,000
loans			165,000,000
Deposits			$ 276,000,000
CBI Common Shares [Member]
Subsequent Event [Line Items]
Stockholders' equity note, stock split, conversion ratio	1.1888
Amount of cash received in conversion of shares	$ 30,130
Subsequent Event [Member]
Subsequent Event [Line Items]
Common stock, value, outstanding		$ 50,200,000
Shares issued, price per share \| $ / shares		$ 60.59
Common stock, par or stated value per share \| $ / shares		$ 25.62