Note 9 - Fair Value Measurements - Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Debt securities available for sale	$ 3,236,049	$ 3,395,810
Agency Residential MBS [Member]
Debt securities available for sale	204,342	211,060
Agency Commercial MBS [Member]
Debt securities available for sale	46,502	6,966
US Government Agencies Debt Securities [Member]
Debt securities available for sale	299,722	292,117
US Treasury Securities [Member]
Debt securities available for sale		4,955
US States and Political Subdivisions Debt Securities [Member]
Debt securities available for sale	60,581	62,186
Corporate Debt Securities [Member]
Debt securities available for sale	1,802,791	1,835,937
Fair Value, Recurring [Member]
Debt securities available for sale	3,236,049	3,395,810
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Debt securities available for sale	0	4,955
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Debt securities available for sale	3,236,049	3,390,855
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Debt securities available for sale	0	0
Fair Value, Recurring [Member] \| Agency Residential MBS [Member]
Debt securities available for sale	204,342	211,060
Fair Value, Recurring [Member] \| Agency Residential MBS [Member] \| Fair Value, Inputs, Level 1 [Member]
Debt securities available for sale	0	0
Fair Value, Recurring [Member] \| Agency Residential MBS [Member] \| Fair Value, Inputs, Level 2 [Member]
Debt securities available for sale	204,342	211,060
Fair Value, Recurring [Member] \| Agency Residential MBS [Member] \| Fair Value, Inputs, Level 3 [Member]
Debt securities available for sale	0	0
Fair Value, Recurring [Member] \| Agency Commercial MBS [Member]
Debt securities available for sale	46,502	6,966
Fair Value, Recurring [Member] \| Agency Commercial MBS [Member] \| Fair Value, Inputs, Level 1 [Member]
Debt securities available for sale	0	0
Fair Value, Recurring [Member] \| Agency Commercial MBS [Member] \| Fair Value, Inputs, Level 2 [Member]
Debt securities available for sale	46,502	6,966
Fair Value, Recurring [Member] \| Agency Commercial MBS [Member] \| Fair Value, Inputs, Level 3 [Member]
Debt securities available for sale	0	0
Fair Value, Recurring [Member] \| US Government Agencies Debt Securities [Member]
Debt securities available for sale	299,722	292,117
Fair Value, Recurring [Member] \| US Government Agencies Debt Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Debt securities available for sale	0	0
Fair Value, Recurring [Member] \| US Government Agencies Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Debt securities available for sale	299,722	292,117
Fair Value, Recurring [Member] \| US Government Agencies Debt Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Debt securities available for sale	0	0
Fair Value, Recurring [Member] \| US Treasury Securities [Member]
Debt securities available for sale		4,955
Fair Value, Recurring [Member] \| US Treasury Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Debt securities available for sale		4,955
Fair Value, Recurring [Member] \| US Treasury Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Debt securities available for sale		0
Fair Value, Recurring [Member] \| US Treasury Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Debt securities available for sale		0
Fair Value, Recurring [Member] \| US States and Political Subdivisions Debt Securities [Member]
Debt securities available for sale	60,581	62,186
Fair Value, Recurring [Member] \| US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Debt securities available for sale	0	0
Fair Value, Recurring [Member] \| US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Debt securities available for sale	60,581	62,186
Fair Value, Recurring [Member] \| US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Debt securities available for sale	0	0
Fair Value, Recurring [Member] \| Corporate Debt Securities [Member]
Debt securities available for sale	1,802,791	1,835,937
Fair Value, Recurring [Member] \| Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Debt securities available for sale	0	0
Fair Value, Recurring [Member] \| Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Debt securities available for sale	1,802,791	1,835,937
Fair Value, Recurring [Member] \| Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Debt securities available for sale	0	0
Fair Value, Recurring [Member] \| Collateralized Loan Obligations [Member]
Debt securities available for sale	822,111	982,589
Fair Value, Recurring [Member] \| Collateralized Loan Obligations [Member] \| Fair Value, Inputs, Level 1 [Member]
Debt securities available for sale	0	0
Fair Value, Recurring [Member] \| Collateralized Loan Obligations [Member] \| Fair Value, Inputs, Level 2 [Member]
Debt securities available for sale	822,111	982,589
Fair Value, Recurring [Member] \| Collateralized Loan Obligations [Member] \| Fair Value, Inputs, Level 3 [Member]
Debt securities available for sale	$ 0	$ 0