Note 6 - Offsetting Assets and Liabilities - Offsetting Liabilities (Details) - Liability [Member] - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Gross amount, recognized	$ 4,214,592	$ 3,385,606
Gross Amount, offset	0	0
Net Amount	4,214,592	3,385,606
Gross Amount, not recognized	(4,171,128)	(3,365,104)
Gross amount, not offset	(30,607)	(14,520)
Net amount, after deduction	12,857	5,982
Repurchase Agreements [Member]
Gross amount, recognized	4,201,717	3,378,445
Gross Amount, offset	0	0
Net Amount	4,201,717	3,378,445
Gross Amount, not recognized	(4,171,128)	(3,365,104)
Gross amount, not offset	(30,589)	(13,341)
Net amount, after deduction	0	0
Payer Swaptions [Member]
Gross amount, recognized	10,284	5,982
Gross Amount, offset	0	0
Net Amount	10,284	5,982
Gross Amount, not recognized	0	0
Gross amount, not offset	0	0
Net amount, after deduction	10,284	5,982
Interest Rate Floor [Member]
Gross amount, recognized	2,573
Gross Amount, offset	0
Net Amount	2,573
Gross Amount, not recognized	0
Gross amount, not offset	0
Net amount, after deduction	2,573
TBA Contracts [Member]
Gross amount, recognized	18	1,179
Gross Amount, offset	0	0
Net Amount	18	1,179
Gross Amount, not recognized	0	0
Gross amount, not offset	(18)	(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