Note 3 - Repurchase Agreements - Schedule of Repurchase Agreements (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Fair market value of securities pledged, including accrued interest receivable	$ 3,524,059	$ 6,525,175
Repurchase agreement liabilities associated with these securities	$ 3,378,445	$ 6,244,106
Net weighted average borrowing rate	4.44%	0.15%
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	$ 2,496,769	$ 4,624,396
Repurchase agreement liabilities associated with these securities	$ 2,404,329	$ 4,403,182
Net weighted average borrowing rate	4.43%	0.15%
Maturity 30 to 90 Days [Member]
Fair market value of securities pledged, including accrued interest receivable	$ 884,632	$ 1,848,080
Repurchase agreement liabilities associated with these securities	$ 837,299	$ 1,789,327
Net weighted average borrowing rate	4.51%	0.13%
Maturity Greater than 90 Days [Member]
Fair market value of securities pledged, including accrued interest receivable	$ 142,658	$ 52,699
Repurchase agreement liabilities associated with these securities	$ 136,817	$ 51,597
Net weighted average borrowing rate	4.15%	0.15%