Note 3 - Loans Receivable (Details Textual)		3 Months Ended		6 Months Ended		12 Months Ended
		Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)	Mar. 31, 2022 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Financing Receivable, before Allowance for Credit Loss, Total		$ 1,276,560,000		$ 1,276,560,000		$ 1,205,785,000
Loans and Leases Receivable, Related Parties, Ending Balance		2,700,000		2,700,000		2,500,000
Loans and Leases Receivable, Related Parties, Past Due or Impaired		0		0		0
Financing Receivable, Nonaccrual		7,493,000		7,493,000		5,574,000
Financing Receivable, Allowance for Credit Loss, Ending Balance		17,271,000	$ 17,410,000	$ 17,271,000	$ 17,410,000	$ 15,778,000	$ 16,905,000	$ 17,782,000	$ 18,823,000
Period of Time Sales of Real Estate Owned Fair Value is Based (Year)				2 years
Minimum Amount of Potential Loan Exposure to be Reviewed by Credit Management Personnel		$ 1,000,000		$ 1,000,000
Minimum Number of Consecutive Contractual Payments Received Prior to Consideration for a Return to Accrual Status		6		6
Financing Receivable, Modifications, Number of Contracts		0	0	7		7
Financing Receivable, Troubled Debt Restructuring		$ 2,045,000		$ 2,045,000		$ 3,989,000
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts		0	0	0	0
Unfunded Loan Commitment [Member]
Financing Receivable, Allowance for Credit Loss, Ending Balance		$ 1,000,000.0		$ 1,000,000.0
One to Four Family [Member]
Financing Receivable, Modifications, Number of Contracts				2	1
Financing Receivable, Troubled Debt Restructuring		424,000	$ 575,000	$ 424,000	$ 575,000
One to Four Family [Member] | Residential Portfolio Segment [Member]
Financing Receivable, before Allowance for Credit Loss, Total		312,657,000		312,657,000		300,523,000
Financing Receivable, Nonaccrual		7,404,000		7,404,000		5,420,000
Financing Receivable, Allowance for Credit Loss, Ending Balance		4,629,000	$ 4,025,000	$ 4,629,000	$ 4,025,000	$ 3,963,000	$ 4,415,000	$ 4,596,000	$ 5,459,000
Financing Receivable, Modifications, Number of Contracts				7		5
Financing Receivable, Troubled Debt Restructuring		2,045,000		$ 2,045,000		$ 1,670,000
Mortgage Loans in Process of Foreclosure, Amount		2,200,000		2,200,000		1,400,000
Financial Asset, 1 to 59 Days Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Total	[1]	1,269,000		1,269,000		643,000
Financing Receivable, Nonaccrual		49,000		49,000		43,000
Financial Asset, 1 to 59 Days Past Due [Member] | One to Four Family [Member] | Residential Portfolio Segment [Member]
Financing Receivable, before Allowance for Credit Loss, Total	[1]	1,269,000		1,269,000		622,000
Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Total	[2]	170,000		170,000		2,051,000
Financing Receivable, Nonaccrual		0		0		347,000
Financial Asset, 60 to 89 Days Past Due [Member] | One to Four Family [Member] | Residential Portfolio Segment [Member]
Financing Receivable, before Allowance for Credit Loss, Total	[2]	170,000		170,000		2,028,000
Financial Asset, Not Past Due [Member]
Financing Receivable, before Allowance for Credit Loss, Total	[3]	1,268,888,000		1,268,888,000		1,198,723,000
Financing Receivable, Nonaccrual		1,200,000		1,200,000		816,000
Financial Asset, Not Past Due [Member] | One to Four Family [Member] | Residential Portfolio Segment [Member]
Financing Receivable, before Allowance for Credit Loss, Total	[3]	305,053,000		305,053,000		293,659,000
Federal Home Loan Bank of Chicago [Member]
Federal Home Loan Bank, Advance, Total		275,000,000.0		275,000,000.0		475,000,000.0
Asset Pledged as Collateral [Member] | Federal Home Loan Bank Advances [Member]
Financing Receivable, before Allowance for Credit Loss, Total		$ 776,400,000		$ 776,400,000		$ 886,700,000

[1] Includes $600,000 and $43,000 at March 31, 2022 and December 31, 2021, respectively, which are on non-accrual status.

[2] Includes $ - and $347,000 at March 31, 2022 and December 31, 2021, respectively, which are on non-accrual status.

[3] Includes $666,000 and $816,000 at March 31, 2022 and December 31, 2021, respectively, which are on non-accrual status.