Note 6 - Loans and the Allowance for Credit Losses - Amortized Cost of of the Modified Loans (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2024	Mar. 31, 2025
Modified	$ 126	$ 83,190
Loans Modified, Gross	$ 7,656,658	$ 7,587,146
Modified, percentage	0.00%	1.10%
Weighted Average Term Extension (Month)		142 months
Weighted Average Payment Reduction		$ 6
Weighted Average Interest Rate Reduction		0.10%
Extended Maturity [Member]
Modified	$ 0	$ 19,053
Payment Deferral [Member]
Modified	126	0
Contractual Interest Rate Reduction [Member]
Modified	0	63,804
Principal Forgiveness [Member]
Modified	0	333
Commercial Portfolio Segment [Member]
Modified	126	17,974
Loans Modified, Gross	$ 1,572,494	$ 1,492,920
Modified, percentage	0.01%	1.20%
Weighted Average Term Extension (Month)		6 months
Weighted Average Payment Reduction		$ 6
Commercial Portfolio Segment [Member] \| Weighted Average [Member]
Payment Deferral (Month)	3 months
Commercial Portfolio Segment [Member] \| Extended Maturity [Member]
Modified	$ 0	17,641
Commercial Portfolio Segment [Member] \| Payment Deferral [Member]
Modified	126	0
Commercial Portfolio Segment [Member] \| Contractual Interest Rate Reduction [Member]
Modified	0	0
Commercial Portfolio Segment [Member] \| Principal Forgiveness [Member]
Modified	0	333
Commercial Real Estate Portfolio Segment [Member]
Modified	0	63,804
Loans Modified, Gross	$ 5,829,950	$ 5,837,671
Modified, percentage	0.00%	1.09%
Weighted Average Interest Rate Reduction		0.10%
Commercial Real Estate Portfolio Segment [Member] \| Extended Maturity [Member]
Modified	$ 0	$ 0
Commercial Real Estate Portfolio Segment [Member] \| Payment Deferral [Member]
Modified	0	0
Commercial Real Estate Portfolio Segment [Member] \| Contractual Interest Rate Reduction [Member]
Modified	0	63,804
Commercial Real Estate Portfolio Segment [Member] \| Principal Forgiveness [Member]
Modified	0	0
Residential Portfolio Segment [Member]
Modified	0	1,412
Loans Modified, Gross	$ 254,214	$ 256,555
Modified, percentage	0.00%	0.55%
Weighted Average Term Extension (Month)		136 months
Weighted Average Payment Reduction		$ 0
Residential Portfolio Segment [Member] \| Extended Maturity [Member]
Modified	$ 0	1,412
Residential Portfolio Segment [Member] \| Payment Deferral [Member]
Modified	0	0
Residential Portfolio Segment [Member] \| Contractual Interest Rate Reduction [Member]
Modified	0	0
Residential Portfolio Segment [Member] \| Principal Forgiveness [Member]
Modified	$ 0	$ 0

The gross amount of loans modified during the period.

No definition available.

Name:	cnob_FinancingReceivableModifiedInPeriodGrossAmount
Namespace Prefix:	cnob_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Weighted average amount of decrease in payment on financing receivable modified during period for debtor experiencing financial difficulty.

+ References

No definition available.

+ Details

Name:	cnob_FinancingReceivableModifiedWeightedAverageDecreaseInPayment
Namespace Prefix:	cnob_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Percentage of financing receivable modified during period for debtor experiencing financial difficulty to total financing receivables.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationToTotalFinancingReceivablesPercent
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amortized cost of financing receivable modified during period for debtor experiencing financial difficulty.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481933/310-10-55-12A

Reference 2: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 33
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-33

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Period of payment deferral of financing receivable modified for debtor experiencing financial difficulty, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481933/310-10-55-12A

+ Details

Name:	us-gaap_FinancingReceivableModifiedPaymentDeferralPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of decrease in weighted average contractual interest rate of financing receivable modified for debtor experiencing financial difficulty.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModifiedWeightedAverageInterestRateDecreaseFromModification
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of increase in weighted average maturity of financing receivable modified for debtor experiencing financial difficulty, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModifiedWeightedAverageTermIncreaseFromModification
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_ExtendedMaturityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_PaymentDeferralMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_ContractualInterestRateReductionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_PrincipalForgivenessMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_WeightedAverageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: