Note 7 - Offsetting Assets and Liabilities - Offsetting Liabilities (Details) - Liability [Member] - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Gross amount, recognized	$ 4,429,678	$ 3,385,606
Gross Amount, offset	0	0
Net Amount	4,429,678	3,385,606
Gross Amount, not recognized	(4,313,600)	(3,365,104)
Gross amount, not offset	(115,108)	(14,520)
Net amount, after deduction	970	5,982
Repurchase Agreements [Member]
Gross amount, recognized	4,426,947	3,378,445
Gross Amount, offset	0	0
Net Amount	4,426,947	3,378,445
Gross Amount, not recognized	(4,313,600)	(3,365,104)
Gross amount, not offset	(113,347)	(13,341)
Net amount, after deduction	0	0
Payer Swaptions [Member]
Gross amount, recognized	0	5,982
Gross Amount, offset	0	0
Net Amount	0	5,982
Gross Amount, not recognized	0	0
Gross amount, not offset	0	0
Net amount, after deduction	0	5,982
Interest Rate Floor [Member]
Gross amount, recognized	2,500
Gross Amount, offset	0
Net Amount	2,500
Gross Amount, not recognized	0
Gross amount, not offset	(1,530)
Net amount, after deduction	970
TBA Contracts [Member]
Gross amount, recognized	231	1,179
Gross Amount, offset	0	0
Net Amount	231	1,179
Gross Amount, not recognized	0	0
Gross amount, not offset	(231)	(1,179)
Net amount, after deduction	$ 0	0
Interest Rate Swap [Member]
Gross amount, recognized		0
Gross Amount, offset		0
Net Amount		0
Gross Amount, not recognized		0
Gross amount, not offset		0
Net amount, after deduction		$ 0