Note 4 - Repurchase Agreements - Schedule of Repurchase Agreements (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Fair value of securities pledged, including accrued interest receivable	$ 6,975,384	$ 5,231,921
Repurchase agreement liabilities associated with these securities	$ 6,655,879	$ 5,025,543
Net weighted average borrowing rate	4.48%	4.66%
Maturity Overnight [Member]
Fair 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 value of securities pledged, including accrued interest receivable	$ 4,885,495	$ 4,850,491
Repurchase agreement liabilities associated with these securities	$ 4,657,644	$ 4,656,303
Net weighted average borrowing rate	4.48%	4.66%
Maturity 30 to 90 Days [Member]
Fair value of securities pledged, including accrued interest receivable	$ 1,864,628	$ 199,993
Repurchase agreement liabilities associated with these securities	$ 1,781,505	$ 192,338
Net weighted average borrowing rate	4.48%	4.56%
Maturity Greater than 90 Days [Member]
Fair value of securities pledged, including accrued interest receivable	$ 225,261	$ 181,437
Repurchase agreement liabilities associated with these securities	$ 216,730	$ 176,902
Net weighted average borrowing rate	4.53%	4.76%