Note 6 - Pledged Assets - Schedule of Financial Instruments Owned and Pledged as Collateral (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Accrued interest receivable	$ 23,044	$ 14,951
Restricted cash	25,723	28,396
Asset Pledged as Collateral [Member]
Accrued interest receivable	22,852	14,922
Restricted cash	25,723	28,396
Total	5,358,194	4,008,552
Asset Pledged as Collateral [Member] | Residential Mortgage-Backed Securities [Member] | Pass Through Certificate [Member]
Investment at fair value	5,193,570	3,868,624
Asset Pledged as Collateral [Member] | Residential Mortgage-Backed Securities [Member] | Structured Finance [Member]
Investment at fair value	15,498	16,930
Asset Pledged as Collateral [Member] | US Treasury Securities [Member]
Investment at fair value	100,551	79,680
Asset Pledged as Collateral [Member] | Repurchase Agreements [Member]
Accrued interest receivable	22,852	14,922
Restricted cash	22,818
Total	5,254,738	3,900,476
Asset Pledged as Collateral [Member] | Repurchase Agreements [Member] | Residential Mortgage-Backed Securities [Member] | Pass Through Certificate [Member]
Investment at fair value	5,193,570	3,868,624
Asset Pledged as Collateral [Member] | Repurchase Agreements [Member] | Residential Mortgage-Backed Securities [Member] | Structured Finance [Member]
Investment at fair value	15,498	16,930
Asset Pledged as Collateral [Member] | Derivative [Member]
Restricted cash	2,905	28,396
Total	103,456	108,076
Asset Pledged as Collateral [Member] | Derivative [Member] | US Treasury Securities [Member]
Investment at fair value	$ 100,551	$ 79,680