Loans and Allowance for Loan Losses (Details Textual) $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($) Loan	Dec. 31, 2016 USD ($) Loan	Dec. 31, 2015 USD ($)
Receivables [Abstract]
Period after which loans considered nonperforming	90 days
Loans in process of foreclosure	$ 378
Gross income on nonaccrual loans	57	$ 160	$ 293
Actual interest on nonaccrual loans	$ 16	$ 41	$ 26
Number of loans modified as TDRs \| Loan	0	0
Number of loans approved as TDRs, subsequently defaulted \| Loan		0

Actual interest included in income on nonaccrual loans.

No definition available.

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Namespace Prefix:	cldb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Gross income that should have been recorded in income on nonaccrual loans.

+ References

No definition available.

+ Details

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Namespace Prefix:	cldb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Minimum period after which loans to be considered non performing.

+ References

No definition available.

+ Details

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Namespace Prefix:	cldb_
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Balance Type:	na
Period Type:	duration

- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

+ Details

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and for which there was a payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953682-111524

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Recorded investment of consumer mortgage loan receivables secured by residential real estate properties for which formal foreclosure proceedings are in process.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 35
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL49126937-111524

+ Details

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

- References

No definition available.

+ Details

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