Note 4 - Repurchase Agreements - Schedule of Repurchase Agreements (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Fair value of securities pledged, including accrued interest receivable	$ 6,723,154	$ 5,231,921
Repurchase agreement liabilities associated with these securities	$ 6,418,641	$ 5,025,543
Net weighted average borrowing rate	4.46%	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	$ 3,212,736	$ 4,850,491
Repurchase agreement liabilities associated with these securities	$ 3,068,225	$ 4,656,303
Net weighted average borrowing rate	4.46%	4.66%
Maturity 30 to 90 Days [Member]
Fair value of securities pledged, including accrued interest receivable	$ 3,376,939	$ 199,993
Repurchase agreement liabilities associated with these securities	$ 3,222,504	$ 192,338
Net weighted average borrowing rate	4.46%	4.56%
Maturity Greater than 90 Days [Member]
Fair value of securities pledged, including accrued interest receivable	$ 133,479	$ 181,437
Repurchase agreement liabilities associated with these securities	$ 127,912	$ 176,902
Net weighted average borrowing rate	4.48%	4.76%