Summary of Significant Accounting Policies (Details) shares in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2023 USD ($) security	Sep. 30, 2023 USD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($) security	Sep. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Dec. 31, 2023 USD ($) security item shares	Dec. 31, 2022 USD ($) security shares	Dec. 31, 2021 USD ($) shares	Dec. 31, 2020 USD ($)
Other real estate owned	$ 0				$ 0				$ 0	$ 0
Restricted Cash and Cash Equivalents	47,900,000				66,300,000				47,900,000	66,300,000
ACL for held-to-maturity securities	$ 1,087,000				$ 1,100,000				$ 1,087,000	$ 1,100,000	$ 862,000	$ 907,000
Number of securities in portfolio | security	4				4				4	4
Interest-bearing Deposits in Banks and Other Financial Institutions	$ 145,300,000				$ 121,900,000				$ 145,300,000	$ 121,900,000
Interest Income, Securities, Operating, Tax Exempt									1,500,000	1,700,000
Goodwill, Impairment Loss									0	0	0
Goodwill, Ending Balance	17,636,000				17,636,000				17,636,000	17,636,000
Financing Receivable Purchase									166,300,000	275,700,000	262,100,000
(Benefit) provision for loans	998,000	$ 596,000	$ 1,416,000	$ 7,508,000	(12,000)	$ 2,145,000	$ 1,590,000	$ 1,358,000
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group, Ending Balance	$ 0				$ 0				0	0
Other than temporary impairment losses investments									0	0
Advertising Expense									$ 2,100,000	3,100,000	2,500,000
Maximum remaining term	40 months								40 months
Number of business units | item									3
Purchase of bank owned life insurance									$ 0	$ 0	$ 25,000,000
Securities similar to commercial owner occupied loan
Number of securities in portfolio | security	2				2				2	2
Flushing Financial Capital Trust II
Capital Securities, Value Issued									$ 60,000,000.0
Common Securities With Voting Rights, Value , Issued									$ 1,900,000
Percentage Of Ownership Interest In Common Securities Of Trust									100.00%
Employee Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount | shares									0	0	0
Bank Premises and Equipment [Member] | Minimum
Property, Plant and Equipment, Useful Life	3 years								3 years
Bank Premises and Equipment [Member] | Maximum
Property, Plant and Equipment, Useful Life	10 years								10 years
Consumer Portfolio Segment [Member]
Mortgage loans in process of foreclosure, amount	$ 4,800,000				$ 5,200,000				$ 4,800,000	$ 5,200,000
Loans Receivable [Member]
Interest Receivable	$ 45,000,000.0				$ 34,500,000				$ 45,000,000.0	$ 34,500,000