Business Segments - Narratives (Details)	3 Months Ended
Mar. 31, 2025 item segment
Business Segments
Number of principal business segments \| segment	3
Mortgage Banking
Business Segments
Number of intersegment lines of credit \| item	2
Mortgage Banking \| FHLB Advances \| Minimum
Business Segments
Variable rate, spread (as a percent)	0.50%
Mortgage Banking \| FHLB Advances \| Maximum
Business Segments
Variable rate, spread (as a percent)	1.75%
Consumer Finance
Business Segments
Floor variable rate (as a percent)	0.035%
Ceiling rate (as a percent)	0.06%
Consumer Finance \| Minimum
Business Segments
Fixed rate (as a percent)	0.038%
Consumer Finance \| Maximum
Business Segments
Fixed rate (as a percent)	0.04%
Consumer Finance \| One-month Term Secured Overnight Financing Rate (SOFR) \| Minimum
Business Segments
Variable rate, spread (as a percent)	2.115%

Percentage of ceiling on borrowings from another operating segment of the reporting entity.

No definition available.

Name:	cffi_InterSegmentInterestDebtInstrumentCeilingPercent
Namespace Prefix:	cffi_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on borrowing from another operating segment of the reporting entity.

+ References

No definition available.

+ Details

Name:	cffi_IntersegmentInterestDebtInstrumentBasisSpreadOnVariableRate
Namespace Prefix:	cffi_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Floor variable rate of borrowing from another operating segment of the reporting entity.

+ References

No definition available.

+ Details

Name:	cffi_IntersegmentInterestDebtInstrumentFloorVariableRate
Namespace Prefix:	cffi_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of intersegment lines of credit.

+ References

No definition available.

+ Details

Name:	cffi_NumberOfIntersegmentLinesOfCredit
Namespace Prefix:	cffi_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22)(a)(1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- 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

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 49
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-49

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-18

+ Details

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

- 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

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

- Details

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

- Details

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

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=cffi_ConsumerFinanceSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=cffi_OneMonthTermSecuredOvernightFinancingRateSofrMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: