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Stock Based Compensation (Details 1) (USD $) | 12 Months Ended
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Dec. 31, 2014
Stock Options - Exercise Price $13.50 [Member] |
Weighted Average Exercise Price of Options outstanding, ending | $ 13.50 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = cofs_StockOptions1Member
Number of Options outstanding, ending | 7,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber / us-gaap_AwardTypeAxis = cofs_StockOptions1Member
Number of Options exercisable | 7,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / us-gaap_AwardTypeAxis = cofs_StockOptions1Member
Weighted average remaining contractual life of options outstanding and exercisable | 3 years 2 months 23 days
Stock Options - Exercise Price $17.95 [Member] |
Weighted Average Exercise Price of Options outstanding, ending | $ 17.95 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = cofs_StockOptions4Member
Number of Options outstanding, ending | 8,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber / us-gaap_AwardTypeAxis = cofs_StockOptions4Member
Number of Options exercisable | 8,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / us-gaap_AwardTypeAxis = cofs_StockOptions4Member
Weighted average remaining contractual life of options outstanding and exercisable | 2 years 19 days
Stock Options - Exercise Price $18.85 [Member] |
Weighted Average Exercise Price of Options outstanding, ending | $ 18.85 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = cofs_StockOptions5Member
Number of Options outstanding, ending | 5,250 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber / us-gaap_AwardTypeAxis = cofs_StockOptions5Member
Number of Options exercisable | 5,250 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / us-gaap_AwardTypeAxis = cofs_StockOptions5Member
Weighted average remaining contractual life of options outstanding and exercisable | 1 year 19 days

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- Definition The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Number of options outstanding, including both vested and non-vested options. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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