Note 3 - Repurchase Agreements - Schedule of Repurchase Agreements (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Fair market value of securities pledged, including accrued interest receivable	$ 3,959,022	$ 3,524,059
Repurchase agreement liabilities associated with these securities	$ 3,769,437	$ 3,378,445
Net weighted average borrowing rate	4.90%	4.44%
Maturity Overnight [Member]
Fair market value of securities pledged, including accrued interest receivable	$ 0	$ 0
Repurchase agreement liabilities associated with these securities	$ 0	$ 0
Net weighted average borrowing rate	0.00%	0.00%
Maturity 2 to 30 Days [Member]
Fair market value of securities pledged, including accrued interest receivable	$ 2,760,937	$ 2,496,769
Repurchase agreement liabilities associated with these securities	$ 2,632,522	$ 2,404,329
Net weighted average borrowing rate	4.88%	4.43%
Maturity 30 to 90 Days [Member]
Fair market value of securities pledged, including accrued interest receivable	$ 1,070,036	$ 884,632
Repurchase agreement liabilities associated with these securities	$ 1,017,354	$ 837,299
Net weighted average borrowing rate	4.96%	4.51%
Maturity Greater than 90 Days [Member]
Fair market value of securities pledged, including accrued interest receivable	$ 128,049	$ 142,658
Repurchase agreement liabilities associated with these securities	$ 119,561	$ 136,817
Net weighted average borrowing rate	4.70%	4.15%