Concentration of Credit Risk (Details) $ in Millions	Dec. 31, 2020 USD ($)
Note to Financial Statements
Lending Limit to Single Borrower	$ 110.0
Largest Aggregate Amount of Loans to Single Borrower	$ 87.8

Largest aggregate amount of loans to a single borrower.

No definition available.

Name:	ffic_LargestAggregateAmountOfLoansToSingleBorrower
Namespace Prefix:	ffic_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant