Note 3 - Investment Securities - Credit Quality (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Held to Maturity, Amortized Cost	$ 834,440	$ 844,635
AAA/AA/A [Member]
Held to Maturity, Amortized Cost	651,256
BBB+/BBB [Member]
Held to Maturity, Amortized Cost	182,729
NR [Member]
Held to Maturity, Amortized Cost	455
Agency Residential MBS [Member]
Held to Maturity, Amortized Cost	49,878	57,927
Agency Residential MBS [Member] \| AAA/AA/A [Member]
Held to Maturity, Amortized Cost	49,423
Agency Residential MBS [Member] \| BBB+/BBB [Member]
Held to Maturity, Amortized Cost	0
Agency Residential MBS [Member] \| NR [Member]
Held to Maturity, Amortized Cost	455
US States and Political Subdivisions Debt Securities [Member]
Held to Maturity, Amortized Cost	45,716	51,261
US States and Political Subdivisions Debt Securities [Member] \| AAA/AA/A [Member]
Held to Maturity, Amortized Cost	45,716
US States and Political Subdivisions Debt Securities [Member] \| BBB+/BBB [Member]
Held to Maturity, Amortized Cost	0
US States and Political Subdivisions Debt Securities [Member] \| NR [Member]
Held to Maturity, Amortized Cost	0
Corporate Debt Securities [Member]
Held to Maturity, Amortized Cost	738,846	$ 735,447
Corporate Debt Securities [Member] \| AAA/AA/A [Member]
Held to Maturity, Amortized Cost	556,117
Corporate Debt Securities [Member] \| BBB+/BBB [Member]
Held to Maturity, Amortized Cost	182,729
Corporate Debt Securities [Member] \| NR [Member]
Held to Maturity, Amortized Cost	$ 0