Loans and Allowance for Loan Losses (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015 NumberOfLoans	Mar. 31, 2014 NumberOfLoans
Financing Receivable, Modifications [Line Items]
Number of loans TDRs	4cofs_NumberOfLoans	4cofs_NumberOfLoans
Pre-Modification Outstanding Recorded Investment	$ 780	$ 529
Post Modification Oustanding Recorded Investment	780	538
Number of loans with payment default	3	3
Post Modification Oustanding Recorded Investment - past due for 30 days or more	615	680
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of loans TDRs	3	3
Pre-Modification Outstanding Recorded Investment	669	440
Post Modification Oustanding Recorded Investment	669	448
Number of loans with payment default	3	3
Post Modification Oustanding Recorded Investment - past due for 30 days or more	615	680
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of loans TDRs	1	1
Pre-Modification Outstanding Recorded Investment	111	89
Post Modification Oustanding Recorded Investment	$ 111	$ 89

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=49124121&loc=SL6953676-111524

+ Details

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- Definition

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

+ References

+ Details

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- Definition

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

+ References

+ Details

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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=49124121&loc=SL6953682-111524

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