Loans and the Allowance for Loan Losses (Details) - Loans by segment modified as troubled debt restructurings - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
ALLL [Member]
Beginning balance		$ 4,500
Additions		8,250
Transfers
Other		(12,750)
Ending balance
Recorded Investment [Member]
Beginning balance	13,818	86,629
Additions	10,378	26,325
Payoffs/paydowns	(3,098)	(2,616)
Transfers	(580)	(96,520)
Other
Ending balance	$ 20,518	$ 13,818

Balance of troubled debt allowance for loan and lease losses.

No definition available.

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Balance Type:	debit
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Additions to the balance of troubled debt allowance for loan and lease losses.

No definition available.

Name:	cnob_FinancingReceivableTroubledDebtRestructuringAdditions
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Data Type:	xbrli:monetaryItemType
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Other changes in the balance of troubled debt allowance for loan and lease losses.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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Payoffs or paydowns of troubled debt allowance for loan and lease losses.

No definition available.

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

Transfers into the balance of troubled debt allowance for loan and lease losses.

No definition available.

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

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Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_FinancialInstrumentAxis=cnob_RecordedInvestmentMember
Namespace Prefix:
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Period Type: