Income Taxes (Schedule of Deferred Tax Assets and Deferred Tax Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Asset
Allowance for possible losses on loans	7,397	$ 7,564
Pension and other benefits	4,018	3,900
Net unrealized losses on derivative instruments	3,200	1,369
Net unrealized losses on postretirement plans	1,165	992
Deferred compensation and benefits	945	963
Purchase accounting and deposit premium	329cac_DeferredTaxAssetDepositPremiums	321cac_DeferredTaxAssetDepositPremiums
Net unrealized losses on AFS securities	172	4,288
Allowance for OREO valuation	107	59
Allowance for OTTI of investments	71	71
Other	1,313us-gaap_DeferredTaxAssetsOther	695us-gaap_DeferredTaxAssetsOther
Total	18,717us-gaap_DeferredTaxAssetsGross	20,222us-gaap_DeferredTaxAssetsGross
Liability
Depreciation	1,910	1,765
Deferred loan origination fees	1,581	1,390
Prepaid expenses	620	766
MSRs	172	254
Total	4,283us-gaap_DeferredIncomeTaxLiabilities	$ 4,175us-gaap_DeferredIncomeTaxLiabilities
Minimum [Member]
Income Tax Contingency [Line Items]
Open tax years	2011
Maximum [Member]
Income Tax Contingency [Line Items]
Open tax years	2013

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from unrealized losses on available-for-sale securities.

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Amount of deferred tax liability attributable to taxable temporary differences from mortgage servicing rights.

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Amount of deferred tax consequences attributable to taxable temporary differences derived from prepaid expenses.

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Amount of deferred tax liability attributable to taxable temporary differences from property, plant, and equipment.

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Tax year that remains open to examination under enacted tax laws, in CCYY format.

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