Securities Available-For-Sale (Details) - Unrealized gains on investment securities - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Securities available-for-sale
Securities available-for-sale, Amortized Cost	$ 399,418	$ 351,928
Securities available-for-sale, Gross Unrealized Gains	3,935	4,645
Securities available-for-sale, Gross Unrealized Losses	(2,837)	(3,283)
Securities available-for-sale, Fair Value	400,516	353,290
Federal Agency Obligations [Member]
Securities available-for-sale
Securities available-for-sale, Amortized Cost	55,819	52,826
Securities available-for-sale, Gross Unrealized Gains	290	282
Securities available-for-sale, Gross Unrealized Losses	(171)	(271)
Securities available-for-sale, Fair Value	55,938	52,837
Residential mortgage pass-through securities [Member]
Securities available-for-sale
Securities available-for-sale, Amortized Cost	133,517	72,922
Securities available-for-sale, Gross Unrealized Gains	668	519
Securities available-for-sale, Gross Unrealized Losses	(1,021)	(944)
Securities available-for-sale, Fair Value	133,164	72,497
Commercial mortgage pass-through securities [Member]
Securities available-for-sale
Securities available-for-sale, Amortized Cost	4,088	4,186
Securities available-for-sale, Gross Unrealized Gains	42	23
Securities available-for-sale, Gross Unrealized Losses
Securities available-for-sale, Fair Value	4,130	4,209
Obligations of U.S. states and political subdivisions [Member]
Securities available-for-sale
Securities available-for-sale, Amortized Cost	143,787	148,747
Securities available-for-sale, Gross Unrealized Gains	2,233	2,789
Securities available-for-sale, Gross Unrealized Losses	(1,044)	(931)
Securities available-for-sale, Fair Value	144,976	150,605
Trust Preferred Securities [Member]
Securities available-for-sale
Securities available-for-sale, Amortized Cost	4,576	5,575
Securities available-for-sale, Gross Unrealized Gains	122	242
Securities available-for-sale, Gross Unrealized Losses	(71)	(151)
Securities available-for-sale, Fair Value	4,627	5,666
Corporate Bonds And Notes [Member]
Securities available-for-sale
Securities available-for-sale, Amortized Cost	30,052	36,717
Securities available-for-sale, Gross Unrealized Gains	255	586
Securities available-for-sale, Gross Unrealized Losses	(219)	(375)
Securities available-for-sale, Fair Value	30,088	36,928
Asset-backed Securities [Member]
Securities available-for-sale
Securities available-for-sale, Amortized Cost	12,605	14,867
Securities available-for-sale, Gross Unrealized Gains	66	2
Securities available-for-sale, Gross Unrealized Losses	(38)	(286)
Securities available-for-sale, Fair Value	12,633	14,583
Certificates of Deposit [Member]
Securities available-for-sale
Securities available-for-sale, Amortized Cost	622	973
Securities available-for-sale, Gross Unrealized Gains	5	10
Securities available-for-sale, Gross Unrealized Losses
Securities available-for-sale, Fair Value	627	983
Equity Securities [Member]
Securities available-for-sale
Securities available-for-sale, Amortized Cost	376	376
Securities available-for-sale, Gross Unrealized Gains	254	192
Securities available-for-sale, Gross Unrealized Losses
Securities available-for-sale, Fair Value	630	568
Other Securities [Member]
Securities available-for-sale
Securities available-for-sale, Amortized Cost	13,976	14,739
Securities available-for-sale, Gross Unrealized Gains
Securities available-for-sale, Gross Unrealized Losses	(273)	(325)
Securities available-for-sale, Fair Value	$ 13,703	$ 14,414

Available for sale securities gross unrealized gain accumulated in investments.

No definition available.

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

- Definition

Available for sale securities gross unrealized loss accumulated in investments.

+ References

No definition available.

+ Details

Name:	cnob_AvailableForSaleSecuritiesGrossUnrealizedLossAccumulatedInInvestments
Namespace Prefix:	cnob_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

Name:	cnob_InvestmentSecuritiesAvailableForSaleAbstract0
Namespace Prefix:	cnob_
Data Type:	xbrli:stringItemType
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=75030427&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=82897076&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=82896770&loc=d3e26610-111562

+ Details

Name:	us-gaap_AvailableForSaleSecurities
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=cnob_FederalAgencyObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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