Note 3 - Investment Securities - Credit Quality (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Held to maturity	$ 936,274	$ 306,403
AAA/AA/A [Member]
Held to maturity	682,227
BBB [Member]
Held to maturity	253,248
B- [Member]
Held to maturity	487
NR [Member]
Held to maturity	312
Agency Residential MBS [Member]
Held to maturity	112,371	148,390
Agency Residential MBS [Member] | AAA/AA/A [Member]
Held to maturity	111,837
Agency Residential MBS [Member] | BBB [Member]
Held to maturity	0
Agency Residential MBS [Member] | B- [Member]
Held to maturity	487
Agency Residential MBS [Member] | NR [Member]
Held to maturity	47
US States and Political Subdivisions Debt Securities [Member]
Held to maturity	103,749	$ 158,013
US States and Political Subdivisions Debt Securities [Member] | AAA/AA/A [Member]
Held to maturity	103,484
US States and Political Subdivisions Debt Securities [Member] | BBB [Member]
Held to maturity	0
US States and Political Subdivisions Debt Securities [Member] | B- [Member]
Held to maturity	0
US States and Political Subdivisions Debt Securities [Member] | NR [Member]
Held to maturity	265
Debt Security, Corporate, US [Member]
Held to maturity	720,154
Debt Security, Corporate, US [Member] | AAA/AA/A [Member]
Held to maturity	466,906
Debt Security, Corporate, US [Member] | BBB [Member]
Held to maturity	253,248
Debt Security, Corporate, US [Member] | B- [Member]
Held to maturity	0
Debt Security, Corporate, US [Member] | NR [Member]
Held to maturity	$ 0