Debt Issuance Cost.

No definition available.

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

- Definition

Floating interest rate on subordinated debentures.

+ References

No definition available.

+ Details

Name:	cnob_FloatingInterestRateOnSubordinatedDebentures
Namespace Prefix:	cnob_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage rate added to LIBOR.

+ References

No definition available.

+ Details

Name:	cnob_PercentageRateAddedToLibor
Namespace Prefix:	cnob_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Cutstom Element.

+ References

No definition available.

+ Details

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

- Definition

Value of subordinated debentures received by Trust.

+ References

No definition available.

+ Details

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

- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentDescriptionOfVariableRateBasis
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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

- Definition

The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585

+ Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=cnob_FixedToFloatingRateSubordinatedNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cnob_SubordinatedDebtFromTrustMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Subordinated Debentures (Details) - USD ($) $ in Thousands		1 Months Ended	6 Months Ended	9 Months Ended
Subordinated Debentures (Details) - USD ($) $ in Thousands	Jan. 11, 2018	Jun. 30, 2015	Jun. 30, 2019	Sep. 30, 2019	Sep. 30, 2018
Subordinated Debentures (Details) [Line Items]
Proceeds from Issuance of Debt				$ 1,286
Debt Instrument, Term			1 year 1 month 6 days
Fixed-to-floating Rate Subordinated Notes [Member]
Subordinated Debentures (Details) [Line Items]
Percentage Rate Added to Libor	2.84%
Proceeds from Issuance of Debt	$ 75,000	$ 50,000
Debt Instrument, Term		5 years
Debt Instrument, Maturity Date	Feb. 01, 2023	Jul. 01, 2025
Debt Instrument, Interest Rate, Stated Percentage	5.20%	5.75%
Debt Instrument, Description of Variable Rate Basis	three-month LIBOR rate plus 284 basis points	three month LIBOR rate plus 393 basis points
Debt Issuance Cost	$ 1,217			136
Subordinated Debt from Trust [Member]
Subordinated Debentures (Details) [Line Items]
Value of subordinated debentures received by Trust				$ 50,000
Percentage Rate Added to Libor				2.85%
Floating interest rate on subordinated debentures				5.12%
Proceeds from Issuance of Debt				$ 5,200
Debt Instrument, Maturity Date				Jan. 23, 2034