Loans - Impaired Loans (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2019	Dec. 31, 2018
Impaired loans
Impaired loans, troubled debt restructurings	$ 4,450	$ 5,450
Impaired loans, Unpaid Principal Balance	4,776	5,928
Impaired loans, Recorded Investment in Loans without Specific Reserve	1,307	2,842
Impaired loans, Recorded Investment in Loans with Specific Reserve	3,331	2,935,000
Impaired loans, Related Allowance	459	428
Impaired loans, Average Balance	4,750	6,099
Impaired loans, Interest Income Recognized	109	276
Real estate - residential mortgage
Impaired loans
Impaired loans, Unpaid Principal Balance	2,824	3,057
Impaired loans, Recorded Investment in Loans without Specific Reserve	1,264	1,288
Impaired loans, Recorded Investment in Loans with Specific Reserve	1,463	1,677,000
Impaired loans, Related Allowance	81	92
Impaired loans, Average Balance	2,798	3,056
Impaired loans, Interest Income Recognized	66	142
Commercial, financial and agricultural \| Commercial real estate lending
Impaired loans
Impaired loans, Unpaid Principal Balance	1,596	2,468
Impaired loans, Recorded Investment in Loans without Specific Reserve	13	1,498
Impaired loans, Recorded Investment in Loans with Specific Reserve	1,556	927,000
Impaired loans, Related Allowance	70	10
Impaired loans, Average Balance	1,608	2,653
Impaired loans, Interest Income Recognized	42	132
Commercial, financial and agricultural \| Commercial business lending
Impaired loans
Impaired loans, Unpaid Principal Balance		33
Impaired loans, Recorded Investment in Loans without Specific Reserve		25
Impaired loans, Average Balance		26
Equity lines
Impaired loans
Impaired loans, Unpaid Principal Balance	225	365
Impaired loans, Recorded Investment in Loans without Specific Reserve	30	31
Impaired loans, Recorded Investment in Loans with Specific Reserve	187	326,000
Impaired loans, Related Allowance	187	326
Impaired loans, Average Balance	218	359
Impaired loans, Interest Income Recognized	1	2
Consumer
Impaired loans
Impaired loans, Unpaid Principal Balance	131	5
Impaired loans, Recorded Investment in Loans with Specific Reserve	125	5,000
Impaired loans, Related Allowance	121
Impaired loans, Average Balance	$ 126	$ 5

Financing Receivables Impaired Troubled Debt Restructuring Amount

No definition available.

Name:	cffi_FinancingReceivablesImpairedTroubledDebtRestructuringAmount
Namespace Prefix:	cffi_
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

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

- Definition

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5258-111524

+ Details

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

- Definition

Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

+ References

+ Details

Name:	us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of allowance for credit losses related to recorded investment.

+ References

+ Details

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

- Definition

Amount of unpaid principal balance of impaired financing receivables with related allowance for credit losses and without related allowance for credit losses.

+ References

+ Details

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

- Definition

Amount of investment in impaired financing receivables for which there is no related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953550-111524

+ Details

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

- Definition

Amount of investment in impaired financing receivables for which there is a related allowance for credit losses.

+ References

+ Details

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

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=us-gaap_ResidentialMortgageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=cffi_CommercialFinancialAndAgriculturalLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=cffi_CommercialRealEstateLendingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CommercialLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=us-gaap_HomeEquityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=cffi_ConsumerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: