Adoption of New Accounting Standards (Details) $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($)
ASU 2018-02 \| Early adoption
Adoption of New Accounting Standards
Reclassification from accumulated other comprehensive income to retained earnings	$ 334

Amount of increase (decrease) in accumulated other comprehensive income (AOCI) for reclassification to retained earnings of tax effect from remeasurement of deferred tax pursuant to Tax Cuts and Jobs Act of 2017.

No definition available.

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Namespace Prefix:	cffi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration