Note 4 - Repurchase Agreements and Reverse Purchase Agreements - Schedule of Repurchase Agreements (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Fair value of securities pledged, including accrued interest receivable	$ 11,499,165	$ 10,551,280
Repurchase agreement liabilities associated with these securities	$ 11,086,915	$ 10,115,466
Net weighted average borrowing rate	3.77%	3.98%
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	$ 7,522,852	$ 6,821,306
Repurchase agreement liabilities associated with these securities	$ 7,254,945	$ 6,544,072
Net weighted average borrowing rate	3.77%	4.00%
Maturity 30 to 90 Days [Member]
Fair value of securities pledged, including accrued interest receivable	$ 3,876,650	$ 3,445,678
Repurchase agreement liabilities associated with these securities	$ 3,750,480	$ 3,297,567
Net weighted average borrowing rate	3.78%	3.96%
Maturity Greater than 90 Days [Member]
Fair value of securities pledged, including accrued interest receivable	$ 99,663	$ 284,296
Repurchase agreement liabilities associated with these securities	$ 81,490	$ 273,827
Net weighted average borrowing rate	3.80%	3.92%