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)
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2020
USD ($)
Jun. 30, 2019
USD ($)
Jun. 30, 2020
USD ($)
Jun. 30, 2019
USD ($)
Dec. 31, 2019
USD ($)
Debt Securities, Available-for-sale, Total $ 856,128,000   $ 856,128,000   $ 759,399,000 [1]
Asset Impairment Charges, Total 3,800,000 $ 6,600,000 8,800,000 $ 8,400,000  
Real Estate Owned, Amount of Loss at Acquisition $ 1,900,000 $ 202,000 2,400,000 $ 224,000  
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate, Foreclosure     $ 287,000   $ 103,000
Minimum [Member]          
Impaired Loans, Fair Value Adjustment, Percent 0.00%   0.00%   0.00%
Real Estate Owned, Fair Value Adjustment, Percent 5.00%   5.00%   5.00%
Weighted Average [Member]          
Impaired Loans, Fair Value Adjustment, Percent 16.40%   16.40%   5.60%
Real Estate Owned, Fair Value Adjustment, Percent 11.60%   11.60%   8.00%
Maximum [Member]          
Impaired Loans, Fair Value Adjustment, Percent 50.00%   50.00%   30.00%
Real Estate Owned, Fair Value Adjustment, Percent 15.00%   15.00%   10.00%
Corporate Debt Securities [Member]          
Number of Available-for-sale Debt Securities Acquired     2    
Debt Securities, Available-for-sale, Total $ 237,358,000   $ 237,358,000   $ 160,477,000
Corporate Debt Securities [Member] | Minimum [Member]          
Debt Securities, Available-for-sale, Total 82,232,000   82,232,000   98,783,600
Corporate Debt Securities [Member] | Weighted Average [Member]          
Debt Securities, Available-for-sale, Total 110,165,400   110,165,400   112,230,500
Corporate Debt Securities [Member] | Maximum [Member]          
Debt Securities, Available-for-sale, Total $ 100,854,900   $ 100,854,900   $ 102,264,800
[1] Derived from audited financial statements.