Allowance for Loan Losses - Change in Allowance for Loan Losses (Details) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016
Changes in the allowance for loan losses
Balance at the beginning of period	$ 37,066	$ 35,569
Provision charged to operations	7,500	8,200
Loans charged off	(10,395)	(9,505)
Recoveries of loans previously charged off	2,325	2,470
Balance at the end of period	36,496	36,734
Real estate - residential mortgage
Changes in the allowance for loan losses
Balance at the beginning of period	2,559	2,471
Provision charged to operations	(44)	(102)
Loans charged off	(6)	(80)
Recoveries of loans previously charged off	38	44
Balance at the end of period	2,547	2,333
Real estate - construction
Changes in the allowance for loan losses
Balance at the beginning of period	816	94
Provision charged to operations	(365)	292
Balance at the end of period	451	386
Commercial, financial and agricultural
Changes in the allowance for loan losses
Balance at the beginning of period	7,393	7,755
Provision charged to operations	596	(308)
Loans charged off	(154)	(35)
Recoveries of loans previously charged off	11	183
Balance at the end of period	7,846	7,595
Equity lines
Changes in the allowance for loan losses
Balance at the beginning of period	685	1,052
Provision charged to operations	22	46
Loans charged off		(55)
Balance at the end of period	707	1,043
Consumer Loan
Changes in the allowance for loan losses
Balance at the beginning of period	261	243
Provision charged to operations	(9)	72
Loans charged off	(130)	(131)
Recoveries of loans previously charged off	87	164
Balance at the end of period	209	348
Consumer Finance
Changes in the allowance for loan losses
Balance at the beginning of period	25,352	23,954
Provision charged to operations	7,300	8,200
Loans charged off	(10,105)	(9,204)
Recoveries of loans previously charged off	2,189	2,079
Balance at the end of period	$ 24,736	$ 25,029

A valuation allowance for financing receivables that are expected to be uncollectible.

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

- Definition

Amount of recovery of financing receivables doubtful of collection that were previously charged off.

+ References

+ Details

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

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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

- Definition

Amount of direct write-downs of financing receivables charged against the allowance.

+ References

+ Details

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

- Definition

Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.11)
-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

+ Details

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

- Details

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

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConstructionLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=cffi_ConsumerFinanceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: