Quarterly report [Sections 13 or 15(d)]

Note 12 - Fair Value Measurement - Financial Assets and Financial Liabilities Carried at Fair Value on a Recurring Basis (Details)

v3.26.1
Note 12 - Fair Value Measurement - Financial Assets and Financial Liabilities Carried at Fair Value on a Recurring Basis (Details) - USD ($)
$ in Thousands
Mar. 31, 2026
Dec. 31, 2025
Available for sale, fair value $ 1,037,151 $ 1,068,825 [1]
US Treasury Securities [Member]    
Available for sale, fair value 471,693 522,923
Collateralized Mortgage-Backed Securities [Member]    
Available for sale, fair value 123,160 133,304
US States and Political Subdivisions Debt Securities [Member]    
Available for sale, fair value 9,822 9,809
Corporate Debt Securities [Member]    
Available for sale, fair value 432,476 402,789
Fair Value, Recurring [Member]    
Available for sale, fair value 1,037,151 1,068,825
Total assets at fair value 1,037,151 1,068,825
Fair Value, Recurring [Member] | US Treasury Securities [Member]    
Available for sale, fair value 471,693 522,923
Fair Value, Recurring [Member] | Collateralized Mortgage-Backed Securities [Member]    
Available for sale, fair value 123,160 133,304
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]    
Available for sale, fair value 9,822 9,809
Fair Value, Recurring [Member] | Corporate Debt Securities [Member]    
Available for sale, fair value 432,476 402,789
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]    
Available for sale, fair value 471,693 522,923
Total assets at fair value 471,693 522,923
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | US Treasury Securities [Member]    
Available for sale, fair value 471,693 522,923
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Collateralized Mortgage-Backed Securities [Member]    
Available for sale, fair value 0 0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]    
Available for sale, fair value 0 0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Corporate Debt Securities [Member]    
Available for sale, fair value 0 0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member]    
Available for sale, fair value 565,458 545,902
Total assets at fair value 565,458 545,902
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | US Treasury Securities [Member]    
Available for sale, fair value 0 0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Collateralized Mortgage-Backed Securities [Member]    
Available for sale, fair value 123,160 133,304
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]    
Available for sale, fair value 9,822 9,809
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Corporate Debt Securities [Member]    
Available for sale, fair value 432,476 402,789
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]    
Available for sale, fair value 0 0
Total assets at fair value 0 0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | US Treasury Securities [Member]    
Available for sale, fair value 0 0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Collateralized Mortgage-Backed Securities [Member]    
Available for sale, fair value 0 0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]    
Available for sale, fair value 0 0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Corporate Debt Securities [Member]    
Available for sale, fair value $ 0 $ 0
[1] Derived from audited financial statements.