Note 9 - Fair Value Measurements - Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands		Sep. 30, 2022		Dec. 31, 2021
Investment securities available for sale		$ 4,376,331		$ 4,638,855
Agency Residential MBS [Member]
Investment securities available for sale		296,689		411,726
US Government-sponsored Enterprises Debt Securities [Member]
Investment securities available for sale		272,525
US Government Agencies Debt Securities [Member]
Investment securities available for sale				119
US States and Political Subdivisions Debt Securities [Member]
Investment securities available for sale		80,987		93,920
Debt Security, Corporate, US [Member]
Investment securities available for sale		2,138,508		2,746,735
Collateralized Loan Obligations [Member]
Investment securities available for sale		1,587,622		1,386,355
Fair Value, Recurring [Member]
Investment securities available for sale		4,376,331		4,638,855
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Investment securities available for sale		0		0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Investment securities available for sale		4,376,331		4,638,855
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Investment securities available for sale		0	[1]	0	[2]
Fair Value, Recurring [Member] | Agency Residential MBS [Member]
Investment securities available for sale		296,689		411,726
Fair Value, Recurring [Member] | Agency Residential MBS [Member] | Fair Value, Inputs, Level 1 [Member]
Investment securities available for sale		0		0
Fair Value, Recurring [Member] | Agency Residential MBS [Member] | Fair Value, Inputs, Level 2 [Member]
Investment securities available for sale		296,689		411,726
Fair Value, Recurring [Member] | Agency Residential MBS [Member] | Fair Value, Inputs, Level 3 [Member]
Investment securities available for sale		0		0	[2]
Fair Value, Recurring [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Investment securities available for sale		272,525
Fair Value, Recurring [Member] | US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Investment securities available for sale		0
Fair Value, Recurring [Member] | US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Investment securities available for sale		272,525
Fair Value, Recurring [Member] | US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Investment securities available for sale		0
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member]
Investment securities available for sale				119
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Investment securities available for sale				0
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Investment securities available for sale				119
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Investment securities available for sale	[2]			0
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]
Investment securities available for sale		80,987		93,920
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Investment securities available for sale		0		0
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Investment securities available for sale		80,987		93,920
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Investment securities available for sale		0	[1]	0	[2]
Fair Value, Recurring [Member] | Debt Security, Corporate, US [Member]
Investment securities available for sale		2,138,508		2,746,735
Fair Value, Recurring [Member] | Debt Security, Corporate, US [Member] | Fair Value, Inputs, Level 1 [Member]
Investment securities available for sale		0		0
Fair Value, Recurring [Member] | Debt Security, Corporate, US [Member] | Fair Value, Inputs, Level 2 [Member]
Investment securities available for sale		2,138,508		2,746,735
Fair Value, Recurring [Member] | Debt Security, Corporate, US [Member] | Fair Value, Inputs, Level 3 [Member]
Investment securities available for sale		0	[1]	0	[2]
Fair Value, Recurring [Member] | Collateralized Loan Obligations [Member]
Investment securities available for sale		1,587,622		1,386,355
Fair Value, Recurring [Member] | Collateralized Loan Obligations [Member] | Fair Value, Inputs, Level 1 [Member]
Investment securities available for sale		0		0
Fair Value, Recurring [Member] | Collateralized Loan Obligations [Member] | Fair Value, Inputs, Level 2 [Member]
Investment securities available for sale		1,587,622		1,386,355
Fair Value, Recurring [Member] | Collateralized Loan Obligations [Member] | Fair Value, Inputs, Level 3 [Member]
Investment securities available for sale		$ 0	[1]	$ 0	[2]

[1] There were no transfers in to or out of level 3 during the six months ended June 30, 2022.

[2] There were no transfers in to or out of level 3 during the year ended December 31, 2021.