Regulatory Requirements and Restrictions - New minimum capital ratios (Details)	Dec. 31, 2017	Dec. 31, 2016
Regulatory Requirements and Restrictions
Capital conservation buffer requirement	1.25%	0.625%

The capital conservation buffer is designed to ensure that capital buffers are built up outside periods of stress which can be drawn down as losses are incurred.

No definition available.

Name:	cffi_RegulatoryCapitalConservationBufferPercentage
Namespace Prefix:	cffi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant