Comprehensive Income (Details) - Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
COMPREHENSIVE INCOME (Details) - Comprehensive Income (Loss) [Line Items]
Sale of securities available-for-sale Net gains on sale of securities available-for-sale	$ (1,780)	$ 224	$ (6,799)	$ 913
Sale of securities available-for-sale Income tax expense	445	(88)	1,737	(356)
Total reclassification	(1,140)	76	(3,974)	(365)
Amounts Reclassified from Accumulated Other Comprehensive Income/(Loss) [Member]
COMPREHENSIVE INCOME (Details) - Comprehensive Income (Loss) [Line Items]
Sale of securities available-for-sale Net gains on sale of securities available-for-sale				1,596
Sale of securities available-for-sale Income tax expense				(579)
Sale of securities available-for-sale				1,017
Amortization of pension plan net actuarial losses Salaries and employee benefits	(91)	103	(182)	(206)
Amortization of pension plan net actuarial losses Income tax benefit	25	42	50	84
Amortization of pension plan net actuarial losses	(66)	(61)	(132)	(122)
Total reclassification	$ (66)	$ (61)	$ (132)	$ 895

Cutstom Element.

No definition available.

Name:	cnob_COMPREHENSIVEINCOMEDetailsComprehensiveIncomeLossLineItems
Namespace Prefix:	cnob_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Other comprehensive income pension plan actuarial (gains) losses before tax.

+ References

No definition available.

+ Details

Name:	cnob_OtherComprehensiveIncomePensionPlanActuarialGainsLossesBeforeTax
Namespace Prefix:	cnob_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Cutstom Element.

+ References

No definition available.

+ Details

Name:	cnob_OtherComprehensiveIncomePensionPlanActuarialGainsLossesNetOfTax
Namespace Prefix:	cnob_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Cutstom Element.

+ References

No definition available.

+ Details

Name:	cnob_OtherComprehensiveIncomePensionPlanActuarialGainsLossesTax
Namespace Prefix:	cnob_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Cutstom Element.

+ References

No definition available.

+ Details

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

- Definition

Amount after tax and reclassification adjustments of other comprehensive income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669619-108580

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 55
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=109228884&loc=d3e1436-108581

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1B
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669625-108580

+ Details

Name:	us-gaap_OtherComprehensiveIncomeLossNetOfTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount before tax and reclassification adjustments of unrealized holding gain (loss) on available-for-sale securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=114867106&loc=d3e637-108580

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27357-111563

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669646-108580

+ Details

Name:	us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of tax expense (benefit) before reclassification adjustments of unrealized holding gain (loss) on available-for-sale securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=114867106&loc=d3e640-108580

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669646-108580

+ Details

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

- Details

Name:	us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis=us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: