BASIS OF PRESENTATION (Policies)	3 Months Ended
BASIS OF PRESENTATION (Policies)	Mar. 31, 2014
BASIS OF PRESENTATION [Abstract]
Basis of Presentation	The accompanying unaudited condensed consolidated financial statements of First Northern Community Bancorp (the “Company”) have been prepared in accordance with accounting principles generally accepted in the United States of America (GAAP) for interim financial information and with the instructions to Form 10-Q and Articles 9 and 10 of Regulation S-X. Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. The results of operations for any interim period are not necessarily indicative of results expected for the full year. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013 as filed with the Securities and Exchange Commission. The preparation of financial statements in conformity with GAAP also requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expense during the reporting period. Actual results could differ from those estimates. All material intercompany balances and transactions have been eliminated in consolidation.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements: In February 2013, FASB issued ASU 2013-04, Obligations Resulting from Joint and Several Liability Arrangements for Which the Total Amount of the Obligation Is Fixed at the Reporting Date, which provides guidance for the recognition, measurement, and disclosure of obligations resulting from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date. Examples of obligations within the scope of this guidance include debt arrangements, other contractual obligations, and settled litigation and judicial rulings. This guidance is effective for interim and annual periods beginning on January 1, 2014 and must be retroactively applied to prior periods presented. Early adoption is permitted. Adoption of the new guidance did not have a significant impact on the Company’s consolidated financial statements. In July 2013, FASB issued ASU 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists. The amendments in this ASU provide that an unrecognized tax benefit, or a portion thereof, should be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward, except to the extent that a net operating loss carryforward, a similar tax loss, or a tax credit carryforward is not available at the reporting date to settle any additional income taxes that would result from disallowance of a tax position, or the tax law does not require the entity to use, and the entity does not intend to use, the deferred tax asset for such purpose, then the unrecognized tax benefit should be presented as a liability. The amendments are effective for fiscal years, and interim periods within those years, beginning after December 15, 2013. Early adoption and retrospective application is permitted. Adoption of the new guidance did not have a significant impact on the Company’s consolidated financial statements. In January 2014, FASB issued ASU 2014-01, Investments – Equity Method and Joint Ventures. The amendments in this ASU permit reporting entities to make an accounting policy election to account for their investments in qualified affordable housing projects using the proportional amortization method if certain conditions are met. Disclosures for a change in accounting principle are required upon transition. The amendments should be applied retrospectively to all periods presented. A reporting entity that uses the effective yield method to account for its investments in qualified affordable housing projects before the date of adoption may continue to apply the effective yield method for those preexisting investments. The amendments in this ASU are effective for public business entities for annual periods and interim periods within those annual periods, beginning after December 15, 2014. Early adoption is permitted. The Company does not expect the adoption of this update to have a significant impact on its consolidated financial statements. In January 2014, FASB issued ASU 2014-04, Receivables – Troubled Debt Restructurings by Creditors. The amendments in this ASU clarify that an in substance repossession or foreclosure occurs, and a creditor is considered to have received physical possession of residential real estate property collateralizing a consumer mortgage loan, upon either (1) the creditor obtaining legal title to the residential real estate property upon completion of a foreclosure or (2) the borrower conveying all interest in the residential real estate property to the creditor to satisfy that loan through completion of a deed in lieu of foreclosure or through a similar legal agreement. Additionally, the amendments require interim and annual disclosure of both (1) the amount of foreclosed residential real estate property held by the creditor and (2) the recorded investment in consumer mortgage loans collateralized by residential real estate property that are in the process of foreclosure according to local requirements of the applicable jurisdiction. The amendments in this ASU are effective for public business entities for annual periods, and interim periods within those annual periods, beginning after December 15, 2014. An entity can elect to adopt the amendments in this ASU using either a modified retrospective transition method or a prospective transition method. Early adoption is permitted. The Company does not expect the adoption of this update to have a significant impact on its consolidated financial statements. In January, 2014, FASB issued ASU 2014-05, Service Concession Arrangements. The amendments specify that an operating entity should not account for a service concession arrangement that is within the scope of this ASU as a lease in accordance with Topic 840. An operating entity should refer to other Topics as applicable to account for various aspects of a service concession arrangement. The amendments also specify that the infrastructure used in a service concession arrangement should not be recognized as property, plant, and equipment of the operating entity. The amendments in this ASU should be applied on a modified retrospective basis to service concession arrangements that exist at the beginning of an entity’s fiscal year of adoption. The modified retrospective approach requires the cumulative effect of applying this ASU to arrangements existing at the beginning of the period of adoption to be recognized as an adjustment to the opening retained earnings balance for the annual period of adoption. The amendments are effective for a public business entity for annual periods, and interim periods within those annual periods, beginning after December 15, 2014. The Company does not expect the adoption of this update to have a significant impact on its consolidated financial statements.
Reclassifications	Reclassifications Certain reclassifications have been made to prior period balances in order to conform to the current year presentation.