Quarterly report pursuant to Section 13 or 15(d)

Note 11 - Fair Value Measurement (Details Textual)

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Note 11 - Fair Value Measurement (Details Textual) - USD ($)
3 Months Ended 12 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Dec. 31, 2020
Asset Impairment Charges, Total $ 2,000,000.0 $ 5,000,000.0  
Real Estate Owned, Amount of Loss at Acquisition 432,000 $ 563,000  
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate, Foreclosure 150,000   $ 209,000
Mortgage Loans in Process of Foreclosure, Amount 928,000   0
Liabilities, Total 11,616,889,000   10,939,802,000 [1]
Securities (Assets) [Member]      
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3 6,200,000    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases 4,100,000    
Fair Value, Recurring [Member]      
Liabilities, Total $ 0   $ 0
Minimum [Member]      
Impaired Loans, Fair Value Adjustment, Percent 0.00%   0.00%
Real Estate Owned, Fair Value Adjustment, Percent 5.00%   5.00%
Maximum [Member]      
Impaired Loans, Fair Value Adjustment, Percent 64.00%   56.00%
Real Estate Owned, Fair Value Adjustment, Percent 25.00%   27.00%
Weighted Average [Member]      
Impaired Loans, Fair Value Adjustment, Percent 25.60%   22.30%
Real Estate Owned, Fair Value Adjustment, Percent 15.90%   12.50%
[1] derived from audited financial statements.