Investment Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Summary of investment securities
Available-for-sale Securities, Amortized Cost	$ 154,124	$ 161,703
Available-for-sale Securities, Gross Unrealized Gains	1,687	2,135
Available-for-sale Securities, Gross Unrealized Losses	1,910	1,591
Available-for-sale securities, Fair Value	153,901	162,247
U.S.Treasury securities
Summary of investment securities
Available-for-sale Securities, Amortized Cost		100
Available-for-sale Securities, Gross Unrealized Gains		1
Available-for-sale securities, Fair Value		101
U.S. Government agencies and corporations
Summary of investment securities
Available-for-sale Securities, Amortized Cost	12,555	8,640
Available-for-sale Securities, Gross Unrealized Gains	136	88
Available-for-sale Securities, Gross Unrealized Losses	68	80
Available-for-sale securities, Fair Value	12,623	8,648
Obligations of states and political subdivisions
Summary of investment securities
Available-for-sale Securities, Amortized Cost	50,139	48,547
Available-for-sale Securities, Gross Unrealized Gains	1,386	1,667
Available-for-sale Securities, Gross Unrealized Losses	120	123
Available-for-sale securities, Fair Value	51,405	50,091
U.S. Government-sponsored mortgage-backed securities
Summary of investment securities
Available-for-sale Securities, Amortized Cost	70,193	85,675
Available-for-sale Securities, Gross Unrealized Gains	165	353
Available-for-sale Securities, Gross Unrealized Losses	679	441
Available-for-sale securities, Fair Value	69,679	85,587
U.S. Government-sponsored collateralized mortgage obligations
Summary of investment securities
Available-for-sale Securities, Amortized Cost	13,665	14,030
Available-for-sale Securities, Gross Unrealized Gains		26
Available-for-sale Securities, Gross Unrealized Losses	135	64
Available-for-sale securities, Fair Value	13,530	13,992
U.S. Government-guaranteed small business administration pools
Summary of investment securities
Available-for-sale Securities, Amortized Cost	2,883
Available-for-sale Securities, Gross Unrealized Losses	46
Available-for-sale securities, Fair Value	2,837
Trust preferred securities
Summary of investment securities
Available-for-sale Securities, Amortized Cost	1,640	1,662
Available-for-sale Securities, Gross Unrealized Losses	862	883
Available-for-sale securities, Fair Value	778	779
Total debt securities
Summary of investment securities
Available-for-sale Securities, Amortized Cost	151,075	158,654
Available-for-sale Securities, Gross Unrealized Gains	1,687	2,135
Available-for-sale Securities, Gross Unrealized Losses	1,910	1,591
Available-for-sale securities, Fair Value	150,852	159,198
Federal Home Loan Bank (FHLB) stock
Summary of investment securities
Available-for-sale Securities, Amortized Cost	2,823	2,823
Available-for-sale securities, Fair Value	2,823	2,823
Federal Reserve Bank (FRB) stock
Summary of investment securities
Available-for-sale Securities, Amortized Cost	226	226
Available-for-sale securities, Fair Value	226	226
Total regulatory stock
Summary of investment securities
Available-for-sale Securities, Amortized Cost	3,049	3,049
Available-for-sale securities, Fair Value	$ 3,049	$ 3,049

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

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=51813488&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=27724398&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=49167202&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_AvailableForSaleSecuritiesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

+ Details

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

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=cldb_USGovernmentGuaranteedSmallBusinessAdministrationPoolsMember
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_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_DebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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