Fair Value of Assets and Liabilities (Details 7) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2016	Dec. 31, 2015
Significant unobservable inputs for assets and liabilities measured at fair value on a recurring and nonrecurring basis
Total debt securities, Fair Value	$ 163,614	$ 153,901
Minimum
Significant unobservable inputs for assets and liabilities measured at fair value on a recurring and nonrecurring basis
Fair value input discount rate	9.06%
Maximum
Significant unobservable inputs for assets and liabilities measured at fair value on a recurring and nonrecurring basis
Fair value input discount rate	14.01%
Trust preferred securities
Significant unobservable inputs for assets and liabilities measured at fair value on a recurring and nonrecurring basis
Total debt securities, Fair Value	$ 715	$ 778
Trust preferred securities \| Minimum
Significant unobservable inputs for assets and liabilities measured at fair value on a recurring and nonrecurring basis
Fair value input discount rate	9.06%	10.26%
Trust preferred securities \| Maximum
Significant unobservable inputs for assets and liabilities measured at fair value on a recurring and nonrecurring basis
Fair value input discount rate	14.01%	14.12%
Trust preferred securities \| Discounted Cash Flow
Significant unobservable inputs for assets and liabilities measured at fair value on a recurring and nonrecurring basis
Total debt securities, Fair Value	$ 715	$ 778
Impaired Loans \| Minimum
Significant unobservable inputs for assets and liabilities measured at fair value on a recurring and nonrecurring basis
Appraisal Adjustments	0.00%	0.00%
Liquidation Expenses	0.00%	0.00%
Impaired Loans \| Maximum
Significant unobservable inputs for assets and liabilities measured at fair value on a recurring and nonrecurring basis
Appraisal Adjustments	73.00%	53.00%
Liquidation Expenses	75.00%	43.00%
Impaired Loans \| Weighted average
Significant unobservable inputs for assets and liabilities measured at fair value on a recurring and nonrecurring basis
Appraisal Adjustments	31.00%	29.00%
Liquidation Expenses	6.00%	5.00%
Impaired Loans \| Appraisal Of Collateral
Significant unobservable inputs for assets and liabilities measured at fair value on a recurring and nonrecurring basis
Total debt securities, Fair Value	$ 6,866	$ 8,800
Other Real Estate Owned
Significant unobservable inputs for assets and liabilities measured at fair value on a recurring and nonrecurring basis
Appraisal Adjustments	0.00%	0.00%
Other Real Estate Owned \| Appraisal Of Collateral
Significant unobservable inputs for assets and liabilities measured at fair value on a recurring and nonrecurring basis
Total debt securities, Fair Value	$ 58	$ 61

Fair value liquidation expenses.

No definition available.

Name:	cldb_FairValueLiquidationExpenses
Namespace Prefix:	cldb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26610-111562

+ Details

Name:	us-gaap_AvailableForSaleSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of adjustment to the observed price for a similar asset or liability when an identical transaction does not exist, used as an input to measure fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueInputsComparabilityAdjustments
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

+ References

+ Details

Name:	us-gaap_FairValueInputsDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=cldb_TrustPreferredSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ValuationTechniqueAxis=cldb_DiscountedCashFlowMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=cldb_ImpairedLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_WeightedAverageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ValuationTechniqueAxis=cldb_AppraisalOfCollateralMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=cldb_OtherRealEstateOwnedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: