Note 8 - Business Combinations (Details Textual)	Sep. 04, 2024 shares
Merger Consideration [Member]
Business Acquisition, Equity Interests Issued Or Issuable, Share, Exchange Per Share (in shares)	0.5175

Represents the number of stock issuable or issued as a result of the merger agreement.

No definition available.

Name:	flic_BusinessAcquisitionEquityInterestsIssuedOrIssuableShareExchangePerShare
Namespace Prefix:	flic_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant