Basis Of Presentation	9 Months Ended
Sep. 30, 2019
Basis Of Presentation [Abstract]
Basis Of Presentation	1 - BASIS OF PRESENTATION The accounting and reporting policies of The First of Long Island Corporation (“Corporation”) reflect banking industry practice and conform to generally accepted accounting principles (“GAAP”) in the United States. In preparing the consolidated financial statements, management is required to make estimates, such as the allowance for loan losses, and assumptions that affect the reported asset and liability balances, revenue and expense amounts, and the disclosure of contingent assets and liabilities. Actual results could differ significantly from those estimates. The consolidated financial statements include the accounts of the Corporation and its wholly-owned subsidiary, The First National Bank of Long Island (“Bank”). The Bank has two wholly owned subsidiaries: FNY Service Corp. and The First of Long Island Agency, Inc. The Bank and FNY Service Corp. jointly own another subsidiary, The First of Long Island REIT, Inc., a real estate investment trust. The consolidated entity is referred to as the “Corporation” and the Bank and its subsidiaries are collectively referred to as the “Bank.” All intercompany balances and amounts have been eliminated. For further information refer to the consolidated financial statements and notes thereto included in the Corporation's Annual Report on Form 10-K for the year ended December 31, 2018. The consolidated financial information included herein as of and for the periods ended September 30, 2019 and 2018 is unaudited. However, such information reflects all adjustments which are, in the opinion of management, necessary for a fair statement of results for the interim periods. The December 31, 2018 consolidated balance sheet was derived from the Corporation's December 31, 2018 audited consolidated financial statements. When appropriate, items in the prior year financial statements are reclassified to conform to the current period presentation.

The entire disclosure for the organization, consolidation and basis of presentation of financial statements disclosure, and significant accounting policies of the reporting entity. May be provided in more than one note to the financial statements, as long as users are provided with an understanding of (1) the significant judgments and assumptions made by an enterprise in determining whether it must consolidate a VIE and/or disclose information about its involvement with a VIE, (2) the nature of restrictions on a consolidated VIE's assets reported by an enterprise in its statement of financial position, including the carrying amounts of such assets, (3) the nature of, and changes in, the risks associated with an enterprise's involvement with the VIE, and (4) how an enterprise's involvement with the VIE affects the enterprise's financial position, financial performance, and cash flows. Describes procedure if disclosures are provided in more than one note to the financial statements.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-URI http://asc.fasb.org/topic&trid=2122149

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-URI http://asc.fasb.org/topic&trid=2197479

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-URI http://asc.fasb.org/topic&trid=2122369

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-URI http://asc.fasb.org/topic&trid=2134479

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