Note 3 - Debt Securities Available for Sale and Held to Maturity - Credit Quality (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Held to Maturity, Amortized Cost	$ 807,847	$ 819,575
AAA/AA/A [Member]
Held to Maturity, Amortized Cost	652,881
BBB+/BBB [Member]
Held to Maturity, Amortized Cost	154,544
NR [Member]
Held to Maturity, Amortized Cost	422
Agency Residential MBS [Member]
Held to Maturity, Amortized Cost	38,873	43,734
Agency Residential MBS [Member] \| AAA/AA/A [Member]
Held to Maturity, Amortized Cost	38,451
Agency Residential MBS [Member] \| BBB+/BBB [Member]
Held to Maturity, Amortized Cost	0
Agency Residential MBS [Member] \| NR [Member]
Held to Maturity, Amortized Cost	422
Agency Commercial MBS [Member]
Held to Maturity, Amortized Cost	19,329
Agency Commercial MBS [Member] \| AAA/AA/A [Member]
Held to Maturity, Amortized Cost	19,329
Agency Commercial MBS [Member] \| BBB+/BBB [Member]
Held to Maturity, Amortized Cost	0
Agency Commercial MBS [Member] \| NR [Member]
Held to Maturity, Amortized Cost	0
US States and Political Subdivisions Debt Securities [Member]
Held to Maturity, Amortized Cost	15,839	33,597
US States and Political Subdivisions Debt Securities [Member] \| AAA/AA/A [Member]
Held to Maturity, Amortized Cost	15,839
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	733,806	$ 742,244
Corporate Debt Securities [Member] \| AAA/AA/A [Member]
Held to Maturity, Amortized Cost	579,262
Corporate Debt Securities [Member] \| BBB+/BBB [Member]
Held to Maturity, Amortized Cost	154,544
Corporate Debt Securities [Member] \| NR [Member]
Held to Maturity, Amortized Cost	$ 0