Note 9 - Fair Value Measurements - Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Debt securities available for sale	$ 3,305,324	$ 3,395,810
Equity securities held for trading at fair value	436	0
Total investment securities	14,663	14,227
Agency Residential MBS [Member]
Debt securities available for sale	192,490	211,060
Agency Commercial MBS [Member]
Debt securities available for sale	397,164	6,966
US Government Agencies Debt Securities [Member]
Debt securities available for sale	305,192	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	51,853	62,186
Corporate Debt Securities [Member]
Debt securities available for sale	1,797,562	1,835,937
Fair Value, Recurring [Member]
Debt securities available for sale	3,305,324	3,395,810
Equity securities held for trading at fair value	436
Total investment securities	3,305,760
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Debt securities available for sale	0	4,955
Equity securities held for trading at fair value	436
Total investment securities	436
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Debt securities available for sale	3,305,324	3,390,855
Equity securities held for trading at fair value	0
Total investment securities	3,305,324
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Debt securities available for sale	0	0
Equity securities held for trading at fair value	0
Total investment securities	0
Fair Value, Recurring [Member] \| Agency Residential MBS [Member]
Debt securities available for sale	192,490	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	192,490	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	397,164	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	397,164	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	305,192	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	305,192	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	51,853	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	51,853	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	1,797,562	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	1,797,562	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	561,063	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	561,063	982,589
Fair Value, Recurring [Member] \| Collateralized Loan Obligations [Member] \| Fair Value, Inputs, Level 3 [Member]
Debt securities available for sale	$ 0	$ 0