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)

v3.25.2
Note 12 - Fair Value Measurement - Financial Assets and Financial Liabilities Carried at Fair Value on a Recurring Basis (Details) - USD ($)
$ in Thousands
Jun. 30, 2025
Dec. 31, 2024
Available for sale, fair value $ 1,227,851 $ 1,161,400 [1]
US Treasury Securities [Member]    
Available for sale, fair value 701,482 617,486
Collateralized Mortgage-Backed Securities [Member]    
Available for sale, fair value 178,151 219,274
US States and Political Subdivisions Debt Securities [Member]    
Available for sale, fair value 9,639 9,517
Corporate Debt Securities [Member]    
Available for sale, fair value 338,579 315,123
Fair Value, Recurring [Member]    
Available for sale, fair value 1,227,851 1,161,400
Total assets at fair value 1,227,851 1,161,400
Fair Value, Recurring [Member] | US Treasury Securities [Member]    
Available for sale, fair value 701,482 617,486
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member]    
Available for sale, fair value   0
Fair Value, Recurring [Member] | Collateralized Mortgage-Backed Securities [Member]    
Available for sale, fair value 178,151 219,274
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]    
Available for sale, fair value 9,639 9,517
Fair Value, Recurring [Member] | Corporate Debt Securities [Member]    
Available for sale, fair value 338,579 315,123
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]    
Available for sale, fair value 701,482 617,486
Total assets at fair value 701,482 617,486
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | US Treasury Securities [Member]    
Available for sale, fair value 701,482 617,486
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member]    
Available for sale, fair value   0
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 526,369 543,914
Total assets at fair value 526,369 543,914
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] | US Government Agencies Debt Securities [Member]    
Available for sale, fair value   0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Collateralized Mortgage-Backed Securities [Member]    
Available for sale, fair value 178,151 219,274
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]    
Available for sale, fair value 9,639 9,517
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Corporate Debt Securities [Member]    
Available for sale, fair value 338,579 315,123
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] | US Government Agencies Debt Securities [Member]    
Available for sale, fair value   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.