Note 6 - Offsetting Assets and Liabilities - Offsetting Liabilities (Details) - Liability [Member] - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Gross amount, recognized	$ 3,789,019	$ 3,385,606
Gross Amount, offset	0	0
Net Amount	3,789,019	3,385,606
Gross Amount, not recognized	(3,751,365)	(3,365,104)
Gross amount, not offset	(27,191)	(14,520)
Net amount, after deduction	10,463	5,982
Repurchase Agreements [Member]
Gross amount, recognized	3,769,437	3,378,445
Gross Amount, offset	0	0
Net Amount	3,769,437	3,378,445
Gross Amount, not recognized	(3,751,365)	(3,365,104)
Gross amount, not offset	(18,072)	(13,341)
Net amount, after deduction	0	0
Payer Swaptions [Member]
Gross amount, recognized	8,528	5,982
Gross Amount, offset	0	0
Net Amount	8,528	5,982
Gross Amount, not recognized	0	0
Gross amount, not offset	0	0
Net amount, after deduction	8,528	5,982
TBA Contracts [Member]
Gross amount, recognized	11,054	1,179
Gross Amount, offset	0	0
Net Amount	11,054	1,179
Gross Amount, not recognized	0	0
Gross amount, not offset	(9,119)	(1,179)
Net amount, after deduction	$ 1,935	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