Fair Value of Assets and Liabilities - Financial Assets Measured at Fair Value on Nonrecurring Basis (Details) - Nonrecurring $ in Thousands	Dec. 31, 2018 USD ($) item	Dec. 31, 2017 USD ($)
Fair value assets and liabilities - Nonrecurring Basis
Financial assets measured at fair value on a non-recurring basis	$ 348	$ 3,606
Impaired loans, net
Fair value assets and liabilities - Nonrecurring Basis
Financial assets measured at fair value on a non-recurring basis	102	3,438
Other real estate owned, net
Fair value assets and liabilities - Nonrecurring Basis
Financial assets measured at fair value on a non-recurring basis	246	168
Level 3
Fair value assets and liabilities - Nonrecurring Basis
Financial assets measured at fair value on a non-recurring basis	$ 348	3,606
Impaired loans, input | item	0.30
Loans Held-for-sale, Valuation Technique [Extensible List]	cffi:ValuationTechniqueAppraisalsMember
Loans Held-for-sale, Measurement Input [Extensible List]	us-gaap:MeasurementInputDiscountRateMember
Other Real Estate Owned, Valuation Technique [Extensible List]	cffi:ValuationTechniqueAppraisalsMember
Other Real Estate Owned, Measurement Input [Extensible List]	us-gaap:MeasurementInputDiscountRateMember
Level 3 | Minimum
Fair value assets and liabilities - Nonrecurring Basis
Other real estate owned, input | item	0.33
Level 3 | Maximum
Fair value assets and liabilities - Nonrecurring Basis
Other real estate owned, input | item	0.47
Level 3 | Impaired loans, net
Fair value assets and liabilities - Nonrecurring Basis
Financial assets measured at fair value on a non-recurring basis	$ 102	3,438
Level 3 | Other real estate owned, net
Fair value assets and liabilities - Nonrecurring Basis
Financial assets measured at fair value on a non-recurring basis	$ 246	$ 168