Significant Accounting Policies (Policies)	6 Months Ended
Jun. 30, 2022
Accounting Policies [Abstract]
Nature of Operations [Policy Text Block]	*Nature of Operations* ConnectOne Bancorp, Inc. (the “Parent Corporation”) is incorporated under the laws of the State of New Jersey and is a registered bank holding company under the Bank Holding Company Act of 1956, as amended (the “BHCA”). The Parent Corporation’s business currently consists primarily of the operation of its wholly-owned subsidiary, ConnectOne Bank (the “Bank” and, collectively with the Parent Corporation and the Parent Corporation’s subsidiaries, the “Company”). The Bank’s subsidiaries include Union Investment Co. (a New Jersey investment company), Twin Bridge Investment Co. (a New Jersey investment company), ConnectOne Preferred Funding Corp. (a New Jersey real estate investment trust), Center Financial Group, LLC (a New Jersey financial services company), Center Advertising, Inc. (a New Jersey advertising company), Morris Property Company, LLC, (a New Jersey limited liability company), Volosin Holdings, LLC, (a New Jersey limited liability company), NJCB Spec-1, LLC (a New Jersey limited liability company), Port Jervis Holdings, LLC (a New Jersey limited liability company), BONJ Special Properties, LLC (a New Jersey limited liability company) and BoeFly, Inc. (a New Jersey financial technology company). The Bank is a community-based, full-service New Jersey-chartered commercial bank that was founded in 2005. The Bank operates from its headquarters located at 301 Sylvan Avenue in the Borough of Englewood Cliffs, Bergen County, New Jersey and through its twenty-four other banking offices. Substantially all loans are secured with various types of collateral, including business assets, consumer assets and commercial/residential real estate. Each borrower’s ability to repay its loans is dependent on the conversion of assets, cash flows generated from the borrowers’ business, real estate rental and consumer wages. The preceding unaudited consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X, and, accordingly, do not include all of the information and footnotes required by GAAP for complete financial statements. However, in the opinion of management, all adjustments (consisting only of normal recurring accruals) considered necessary for a fair presentation have been included. Operating results for the three and six months ended June 30, 2022 are not necessarily indicative of the results that may be expected for the full year ending December 31, 2022, or for any other interim period. The Company’s 2021 Annual Report on Form 10-K should be read in conjunction with these consolidated financial statements.
Basis of Accounting, Policy [Policy Text Block]	*Basis of Presentation* The consolidated financial statements have been prepared in conformity with GAAP. Some items in the prior year consolidated financial statements were reclassified to conform to current presentation. Reclassifications had no effect on prior year net income or stockholders’ equity.
Use of Estimates, Policy [Policy Text Block]	*Use of Estimates* In preparing the consolidated financial statements, management has made estimates and assumptions that affect the reported amounts of assets and liabilities as of the dates of the consolidated statements of condition and that affect the results of operations for the periods presented. Actual results could differ significantly from those estimates.
New Accounting Pronouncements, Policy [Policy Text Block]	*Risks and Uncertainties* As previously disclosed, on March 11, 2020 the World Health Organization declared the outbreak of COVID-19 as a global pandemic, which continues to impact the United States and the world. On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (CARES Act) was enacted to, among other things, provide emergency assistance for individuals, families and businesses affected by the COVID-19 pandemic. The COVID-19 pandemic has adversely affected, and continues to adversely affect economic activity globally, nationally and locally. Although economic activity began to accelerate in 2021, and the United States continues to implement a COVID-19 vaccination program, COVID-19, it’s variants and actions taken to mitigate the spread of it have had and may in the future have an adverse impact on the economies and financial markets of many countries and parts of the United States, including the New Jersey/New York metropolitan area in which the Company primarily operates. Although the Company has been able to continue operations while taking steps to ensure the safety of employees and clients, COVID-19 could impact the Company’s operations in the future. The effects of the COVID-19 pandemic may adversely affect the Company’s financial condition and results of operations in future periods. Although state and local governments have lifted many restrictions on conducting business, it is possible that restrictions could be reimposed. On July 27, 2017, the U.K. Financial Conduct Authority, which regulates London Interbank Offered Rate ("LIBOR"), announced that it will no longer persuade or compel banks to submit rates for the calculation of LIBOR to the LIBOR administration after 2021. The announcement also indicates that the continuation of LIBOR on the current basis cannot and will not be guaranteed after 2021. Consequently, although banks have continued to submit rates for the calculation of LIBOR in 2022, at this time, it is not possible to predict whether and to what extent banks will continue to provide LIBOR submissions to the LIBOR administrator or whether any additional reforms to LIBOR may be enacted in the United Kingdom or elsewhere. Similarly, banking regulators in the United States have required insured depository institutions in the United states to cease originating loans using LIBOR as a rate index as of December 31, 2021, and in March 2022 Congress adopted legislation providing for the replacement of LIBOR indexes in contracts without fall back language with the Secured Overnight Financing Rate ("SOFR"), and for the Federal Reserve to adopt regulation by September of 2022 implementing this change. Although the Bank ceased using LIBOR as an index for loans it originates, it is unclear at this time what effect these changes may have on the values of loans and liabilities held or owed by the Bank whose interest rates are tied to LIBOR. Uncertainty as to the nature of such potential changes, alternative reference rates, the elimination or replacement of LIBOR, or other reforms may adversely affect the value of, and the return on our loans, and our investment securities.

Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2022

Nature of Operations [Policy Text Block]

Nature of Operations

ConnectOne Bancorp, Inc. (the “Parent Corporation”) is incorporated under the laws of the State of New Jersey and is a registered bank holding company under the Bank Holding Company Act of 1956, as amended (the “BHCA”). The Parent Corporation’s business currently consists primarily of the operation of its wholly-owned subsidiary, ConnectOne Bank (the “Bank” and, collectively with the Parent Corporation and the Parent Corporation’s subsidiaries, the “Company”). The Bank’s subsidiaries include Union Investment Co. (a New Jersey investment company), Twin Bridge Investment Co. (a New Jersey investment company), ConnectOne Preferred Funding Corp. (a New Jersey real estate investment trust), Center Financial Group, LLC (a New Jersey financial services company), Center Advertising, Inc. (a New Jersey advertising company), Morris Property Company, LLC, (a New Jersey limited liability company), Volosin Holdings, LLC, (a New Jersey limited liability company), NJCB Spec-1, LLC (a New Jersey limited liability company), Port Jervis Holdings, LLC (a New Jersey limited liability company), BONJ Special Properties, LLC (a New Jersey limited liability company) and BoeFly, Inc. (a New Jersey financial technology company).

The Bank is a community-based, full-service New Jersey-chartered commercial bank that was founded in 2005. The Bank operates from its headquarters located at 301 Sylvan Avenue in the Borough of Englewood Cliffs, Bergen County, New Jersey and through its twenty-four other banking offices. Substantially all loans are secured with various types of collateral, including business assets, consumer assets and commercial/residential real estate. Each borrower’s ability to repay its loans is dependent on the conversion of assets, cash flows generated from the borrowers’ business, real estate rental and consumer wages.

The preceding unaudited consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X, and, accordingly, do not include all of the information and footnotes required by GAAP for complete financial statements. However, in the opinion of management, all adjustments (consisting only of normal recurring accruals) considered necessary for a fair presentation have been included. Operating results for the three and six months ended June 30, 2022 are not necessarily indicative of the results that may be expected for the full year ending December 31, 2022, or for any other interim period. The Company’s 2021 Annual Report on Form 10-K should be read in conjunction with these consolidated financial statements.

Basis of Accounting, Policy [Policy Text Block]

Basis of Presentation

The consolidated financial statements have been prepared in conformity with GAAP. Some items in the prior year consolidated financial statements were reclassified to conform to current presentation. Reclassifications had no effect on prior year net income or stockholders’ equity.

Use of Estimates, Policy [Policy Text Block]

Use of Estimates

In preparing the consolidated financial statements, management has made estimates and assumptions that affect the reported amounts of assets and liabilities as of the dates of the consolidated statements of condition and that affect the results of operations for the periods presented. Actual results could differ significantly from those estimates.

New Accounting Pronouncements, Policy [Policy Text Block]

Risks and Uncertainties

As previously disclosed, on March 11, 2020 the World Health Organization declared the outbreak of COVID-19 as a global pandemic, which continues to impact the United States and the world. On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (CARES Act) was enacted to, among other things, provide emergency assistance for individuals, families and businesses affected by the COVID-19 pandemic. The COVID-19 pandemic has adversely affected, and continues to adversely affect economic activity globally, nationally and locally. Although economic activity began to accelerate in 2021, and the United States continues to implement a COVID-19 vaccination program, COVID-19, it’s variants and actions taken to mitigate the spread of it have had and may in the future have an adverse impact on the economies and financial markets of many countries and parts of the United States, including the New Jersey/New York metropolitan area in which the Company primarily operates. Although the Company has been able to continue operations while taking steps to ensure the safety of employees and clients, COVID-19 could impact the Company’s operations in the future. The effects of the COVID-19 pandemic may adversely affect the Company’s financial condition and results of operations in future periods. Although state and local governments have lifted many restrictions on conducting business, it is possible that restrictions could be reimposed.

On July 27, 2017, the U.K. Financial Conduct Authority, which regulates London Interbank Offered Rate ("LIBOR"), announced that it will no longer persuade or compel banks to submit rates for the calculation of LIBOR to the LIBOR administration after 2021. The announcement also indicates that the continuation of LIBOR on the current basis cannot and will not be guaranteed after 2021. Consequently, although banks have continued to submit rates for the calculation of LIBOR in 2022, at this time, it is not possible to predict whether and to what extent banks will continue to provide LIBOR submissions to the LIBOR administrator or whether any additional reforms to LIBOR may be enacted in the United Kingdom or elsewhere. Similarly, banking regulators in the United States have required insured depository institutions in the United states to cease originating loans using LIBOR as a rate index as of December 31, 2021, and in March 2022 Congress adopted legislation providing for the replacement of LIBOR indexes in contracts without fall back language with the Secured Overnight Financing Rate ("SOFR"), and for the Federal Reserve to adopt regulation by September of 2022 implementing this change. Although the Bank ceased using LIBOR as an index for loans it originates, it is unclear at this time what effect these changes may have on the values of loans and liabilities held or owed by the Bank whose interest rates are tied to LIBOR. Uncertainty as to the nature of such potential changes, alternative reference rates, the elimination or replacement of LIBOR, or other reforms may adversely affect the value of, and the return on our loans, and our investment securities.