Commitments (Details 2) - USD ($)	6 Months Ended
Jun. 30, 2016	Dec. 31, 2015
Customer interest rate swap, Maturing in 2020
Derivative [Line Items]
Maturity	2020
Notional Amount	$ 2,637,000	$ 2,680,000
Interest Rate Paid	1 Mo. Libor + Margin
Interest Rate Received	Fixed
Fair Value	$ 110,000	35,000
Customer interest rate swap, Maturing in 2025
Derivative [Line Items]
Maturity	2025
Notional Amount	$ 5,787,000	5,921,000
Interest Rate Paid	1 Mo. Libor + Margin
Interest Rate Received	Fixed
Fair Value	$ 423,000	136,000
Customer interest rate swap, Maturing in 2026
Derivative [Line Items]
Maturity	2026
Notional Amount	$ 2,233,000
Interest Rate Paid	1 Mo. Libor + Margin
Interest Rate Received	Fixed
Fair Value	$ 106,000
Customer interest rate swap
Derivative [Line Items]
Notional Amount	10,657,000	8,601,000
Fair Value	$ 639,000	171,000
Third party interest rate swap, Maturing in 2020
Derivative [Line Items]
Maturity	2020
Notional Amount	$ 2,637,000	2,680,000
Interest Rate Paid	Fixed
Interest Rate Received	1 Mo. Libor + Margin
Fair Value	$ (110,000)	(35,000)
Third party interest rate swap, Maturing in 2025
Derivative [Line Items]
Maturity	2025
Notional Amount	$ 5,787,000	5,921,000
Interest Rate Paid	Fixed
Interest Rate Received	1 Mo. Libor + Margin
Fair Value	$ (423,000)	(136,000)
Third party interest rate swap, Maturing in 2026
Derivative [Line Items]
Maturity	2026
Notional Amount	$ 2,233,000
Interest Rate Paid	Fixed
Interest Rate Received	1 Mo. Libor + Margin
Fair Value	$ (106,000)
Third party interest rate swap
Derivative [Line Items]
Notional Amount	10,657,000	8,601,000
Fair Value	$ (639,000)	$ (171,000)

Derivative maturity year.

No definition available.

Name:	cldb_DerivativeMaturityYear
Namespace Prefix:	cldb_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

Derivative type of interest rate received on swap.

+ References

No definition available.

+ Details

Name:	cldb_DerivativeTypeOfInterestRateReceivedOnSwap
Namespace Prefix:	cldb_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

+ Details

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

When the derivative or group of derivatives presented is a swap, the type of interest rate (fixed, variable, stepped, etc.) paid on the swap.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column A
-Footnote 1

+ Details

Name:	invest_DerivativeTypeOfInterestRatePaidOnSwap
Namespace Prefix:	invest_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

Fair value as of the balance sheet date of all derivatives not designated as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

+ Details

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

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cldb_CustomerInterestRateSwapMaturingIn2020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cldb_CustomerInterestRateSwapMaturingIn2025Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cldb_CustomerInterestRateSwapMaturingIn2026Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cldb_CustomerInterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cldb_ThirdPartyInterestRateSwapMaturingIn2020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cldb_ThirdPartyInterestRateSwapMaturingIn2025Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cldb_ThirdPartyInterestRateSwapMaturingIn2026Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cldb_ThirdPartyInterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: