INVESTMENT SECURITIES (Details) - Unrealized gains on investment securities (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Investment Securities Available-for-Sale:
Investment Securities Available-for-Sale, Amortized Cost	$ 281,461	$ 319,147
Investment Securities Available-for-Sale, Gross Unrealized Gains	8,596	6,960
Investment Securities Available-for-Sale, Gross Unrealized Losses	(525)	(3,037)
Investment Securities Available-for-Sale, Fair Value	289,532us-gaap_AvailableForSaleSecurities	323,070us-gaap_AvailableForSaleSecurities
Investment Securities Held-to-Maturity:
Investment Securities Held-to-Maturity, Amortized Cost	224,682	215,286
Investment Securities Held-to-Maturity, Gross Unrealized Gains	6,858	1,516
Investment Securities Held-to-Maturity, Gross Unrealized Losses	(95)	(5,844)
Investment Securities Held-to-Maturity, Fair Value	231,445	210,958
Total, Amortized Cost	506,143	534,433
Total, Gross Unrealized Gains	15,454	8,476
Total, Gross Unrealized Losses	(620)	(8,881)
Total, Fair Value	520,977cnob_TotalInvestmentSecuritiesFairValue	534,028cnob_TotalInvestmentSecuritiesFairValue
Federal Agency Obligations [Member]
Investment Securities Available-for-Sale:
Investment Securities Available-for-Sale, Amortized Cost	32,650	20,567
Investment Securities Available-for-Sale, Gross Unrealized Gains	217	29
Investment Securities Available-for-Sale, Gross Unrealized Losses	(50)	(655)
Investment Securities Available-for-Sale, Fair Value	32,817	19,941
Investment Securities Held-to-Maturity:
Investment Securities Held-to-Maturity, Amortized Cost	27,103	15,249
Investment Securities Held-to-Maturity, Gross Unrealized Gains	322	23
Investment Securities Held-to-Maturity, Gross Unrealized Losses	(28)	(389)
Investment Securities Held-to-Maturity, Fair Value	27,397	14,883
Residential Mortgage Backed Securities [Member]
Investment Securities Available-for-Sale:
Investment Securities Available-for-Sale, Amortized Cost	58,836	48,312
Investment Securities Available-for-Sale, Gross Unrealized Gains	1,531	791
Investment Securities Available-for-Sale, Gross Unrealized Losses	(11)	(229)
Investment Securities Available-for-Sale, Fair Value	60,356	48,874
Investment Securities Held-to-Maturity:
Investment Securities Held-to-Maturity, Amortized Cost	5,955	2,246
Investment Securities Held-to-Maturity, Gross Unrealized Gains	28
Investment Securities Held-to-Maturity, Gross Unrealized Losses		(64)
Investment Securities Held-to-Maturity, Fair Value	5,983	2,182
Commercial Mortgage Backed Securities [Member]
Investment Securities Available-for-Sale:
Investment Securities Available-for-Sale, Amortized Cost	3,042	7,145
Investment Securities Available-for-Sale, Gross Unrealized Gains	4	3
Investment Securities Available-for-Sale, Gross Unrealized Losses		(157)
Investment Securities Available-for-Sale, Fair Value	3,046	6,991
Investment Securities Held-to-Maturity:
Investment Securities Held-to-Maturity, Amortized Cost	4,266	4,417
Investment Securities Held-to-Maturity, Gross Unrealized Gains	50	41
Investment Securities Held-to-Maturity, Gross Unrealized Losses		(62)
Investment Securities Held-to-Maturity, Fair Value	4,316	4,396
US States and Political Subdivisions Debt Securities [Member]
Investment Securities Available-for-Sale:
Investment Securities Available-for-Sale, Amortized Cost	8,201	30,804
Investment Securities Available-for-Sale, Gross Unrealized Gains	205	711
Investment Securities Available-for-Sale, Gross Unrealized Losses		(55)
Investment Securities Available-for-Sale, Fair Value	8,406	31,460
Investment Securities Held-to-Maturity:
Investment Securities Held-to-Maturity, Amortized Cost	120,144	127,418
Investment Securities Held-to-Maturity, Gross Unrealized Gains	4,512	1,303
Investment Securities Held-to-Maturity, Gross Unrealized Losses	(60)	(3,688)
Investment Securities Held-to-Maturity, Fair Value	124,596	125,033
Trust Preferred Securities [Member]
Investment Securities Available-for-Sale:
Investment Securities Available-for-Sale, Amortized Cost	16,086	19,763
Investment Securities Available-for-Sale, Gross Unrealized Gains	489	150
Investment Securities Available-for-Sale, Gross Unrealized Losses	(269)	(510)
Investment Securities Available-for-Sale, Fair Value	16,306	19,403
Corporate Bonds and Notes [Member]
Investment Securities Available-for-Sale:
Investment Securities Available-for-Sale, Amortized Cost	119,838	154,182
Investment Securities Available-for-Sale, Gross Unrealized Gains	5,950	4,930
Investment Securities Available-for-Sale, Gross Unrealized Losses	(11)	(482)
Investment Securities Available-for-Sale, Fair Value	125,777	158,630
Investment Securities Held-to-Maturity:
Investment Securities Held-to-Maturity, Amortized Cost	38,950	37,900
Investment Securities Held-to-Maturity, Gross Unrealized Gains	1,026	149
Investment Securities Held-to-Maturity, Gross Unrealized Losses	(7)	(622)
Investment Securities Held-to-Maturity, Fair Value	39,969	37,427
Asset-backed Securities [Member]
Investment Securities Available-for-Sale:
Investment Securities Available-for-Sale, Amortized Cost	27,393	15,733
Investment Securities Available-for-Sale, Gross Unrealized Gains	140	246
Investment Securities Available-for-Sale, Gross Unrealized Losses	(31)
Investment Securities Available-for-Sale, Fair Value	27,502	15,979
Certificate of Deposit [Member]
Investment Securities Available-for-Sale:
Investment Securities Available-for-Sale, Amortized Cost	2,098	2,250
Investment Securities Available-for-Sale, Gross Unrealized Gains	27	32
Investment Securities Available-for-Sale, Gross Unrealized Losses	(2)	(20)
Investment Securities Available-for-Sale, Fair Value	2,123	2,262
Equity Securities [Member]
Investment Securities Available-for-Sale:
Investment Securities Available-for-Sale, Amortized Cost	376	376
Investment Securities Available-for-Sale, Gross Unrealized Losses	(69)	(89)
Investment Securities Available-for-Sale, Fair Value	307	287
Other Securities [Member]
Investment Securities Available-for-Sale:
Investment Securities Available-for-Sale, Amortized Cost	12,941	5,671
Investment Securities Available-for-Sale, Gross Unrealized Gains	33	68
Investment Securities Available-for-Sale, Gross Unrealized Losses	(82)	(15)
Investment Securities Available-for-Sale, Fair Value	12,892	5,724
US Treasury Securities [Member]
Investment Securities Available-for-Sale:
Investment Securities Available-for-Sale, Amortized Cost		14,344
Investment Securities Available-for-Sale, Gross Unrealized Losses		(825)
Investment Securities Available-for-Sale, Fair Value		13,519
Investment Securities Held-to-Maturity:
Investment Securities Held-to-Maturity, Amortized Cost	28,264	28,056
Investment Securities Held-to-Maturity, Gross Unrealized Gains	920
Investment Securities Held-to-Maturity, Gross Unrealized Losses		(1,019)
Investment Securities Held-to-Maturity, Fair Value	$ 29,184	$ 27,037

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Held to maturity securities accumulated unrecognized holding gain.

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Total investment securities, amortized cost.

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Total investment securities, fair value.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount before other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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