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Investments (Narrative) (Details) (USD $) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2015 security | Mar. 31, 2014 | Dec. 31, 2014
Schedule of Investments [Line Items] |  |  |
Credit-related net investment impairment losses | $ 0 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsAdditionsAdditionalCreditLosses | $ 0 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsAdditionsAdditionalCreditLosses | $ 0 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsAdditionsAdditionalCreditLosses
Regional community bank stocks, percent of average trading volumes (less than 0.1%) | 0.20%chco_PercentOfAverageDailyTradingVolume |  |
Number Of Pooled Trust Preferred Securities | 5 chco_NumberOfPooledTrustPreferredSecurities |  |
Pooled trust preferred securities, book value | 500,000 chco_PooledTrustPreferredSecuritiesBookValue |  |
Pooled trust preferred securities, estimated fair value | 1,700,000 chco_PooledTrustPreferredSecuritiesEstimatedFairValue |  |
Annual prepayment rate | 1.00%us-gaap_FairValueInputsPrepaymentRate |  | 1.00%us-gaap_FairValueInputsPrepaymentRate
Annual prepayments maturity | 100.00%chco_AnnualPrepaymentsMaturityPercentage |  | 100.00%chco_AnnualPrepaymentsMaturityPercentage
Additional basis points | 1.50%chco_AdditionalBasisPointsAnnualDefaultsFromBanks |  | 1.50%chco_AdditionalBasisPointsAnnualDefaultsFromBanks
Carrying value of securities pledged | 267,000,000 us-gaap_AvailableForSaleSecuritiesPledgedAsCollateral |  | 273,000,000 us-gaap_AvailableForSaleSecuritiesPledgedAsCollateral
Held-to-maturity Securities, Transferred Security, at Carrying Value |  | $ 83,400,000 us-gaap_HeldToMaturitySecuritiesTransferredSecurityAtCarryingValue |
Maximum [Member] |  |  |
Schedule of Investments [Line Items] |  |  |
Equity ownership positions in the community bank holding companies | 4.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_RangeAxis = us-gaap_MaximumMember |  |

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- Definition This item represents an increase to the cumulative amount of credit losses recognized in earnings for an other than temporary impairment (OTTI) of a debt security held for which a previous OTTI was recognized and the investor does not intend to sell the debt security and it is not more likely than not that the investor will be required to sell the debt security before recovery of its amortized cost basis. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27340-111563 + Details
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