Loans and Allowance for Loan Losses (Details 4) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014 NumberOfLoans	Dec. 31, 2013 NumberOfLoans
Financing Receivable, Modifications [Line Items]
Number of loans TDRs	8cofs_NumberOfLoans	7cofs_NumberOfLoans
Pre-Modification Outstanding Recorded Investment	$ 1,909	$ 1,276
Post Modification Oustanding Recorded Investment	1,909	1,276
Number of loans with payment default	8	5
Post Modification Oustanding Recorded Investment - past due for 30 days or more	1,702	673
Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of loans TDRs	1	1
Pre-Modification Outstanding Recorded Investment	32	216
Post Modification Oustanding Recorded Investment	32	216
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number of loans with payment default		1
Post Modification Oustanding Recorded Investment - past due for 30 days or more		29
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of loans TDRs	5	4
Pre-Modification Outstanding Recorded Investment	1,596	948
Post Modification Oustanding Recorded Investment	1,596	948
Number of loans with payment default	6	3
Post Modification Oustanding Recorded Investment - past due for 30 days or more	1,592	573
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of loans TDRs	2	2
Pre-Modification Outstanding Recorded Investment	281	112
Post Modification Oustanding Recorded Investment	281	112
Number of loans with payment default	2	1
Post Modification Oustanding Recorded Investment - past due for 30 days or more	$ 110	$ 71

The number of loans relating to troubled debt restructurings.

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- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 33

-URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953676-111524

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Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

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- Definition

Pre-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

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- Definition

Amount of investment related to financing receivables modified by troubled debt restructurings within the previous 12 months, for which there was a payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 34

-URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953682-111524

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