Note 4 - Repurchase Agreements and Reverse Repurchase Agreements - Schedule of Repurchase Agreements (Details) - USD ($) $ in Thousands	Sep. 30, 2026	Dec. 31, 2025
Fair value of securities pledged, including accrued interest receivable	$ 10,664,865	$ 10,551,280
Repurchase agreement liabilities associated with these securities	$ 10,361,717	$ 10,115,466
Net weighted average borrowing rate	3.99%	3.98%
Maturity Overnight [Member]
Fair value of securities pledged, including accrued interest receivable	$ 767,226	$ 0
Repurchase agreement liabilities associated with these securities	$ 741,836	$ 0
Net weighted average borrowing rate	3.99%	0.00%
Maturity 2 to 30 Days [Member]
Fair value of securities pledged, including accrued interest receivable	$ 9,118,314	$ 6,821,306
Repurchase agreement liabilities associated with these securities	$ 8,869,687	$ 6,544,072
Net weighted average borrowing rate	3.98%	4.00%
Maturity 30 to 90 Days [Member]
Fair value of securities pledged, including accrued interest receivable	$ 564,716	$ 3,445,678
Repurchase agreement liabilities associated with these securities	$ 536,986	$ 3,297,567
Net weighted average borrowing rate	4.00%	3.96%
Maturity Greater than 90 Days [Member]
Fair value of securities pledged, including accrued interest receivable	$ 214,609	$ 284,296
Repurchase agreement liabilities associated with these securities	$ 213,208	$ 273,827
Net weighted average borrowing rate	4.30%	3.92%