Note 6 - Pledged Assets - Schedule of Financial Instruments Owned and Pledged as Collateral (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Accrued interest receivable	$ 18,988	$ 14,951
Restricted cash	15,968	28,396
Asset Pledged as Collateral [Member]
Accrued interest receivable	18,972	14,922
Restricted cash	15,968	28,396
Total	4,634,506	4,008,552
Asset Pledged as Collateral [Member] | Residential Mortgage-Backed Securities [Member] | Pass Through Certificate [Member]
Investment at fair value	4,504,465	3,868,624
Asset Pledged as Collateral [Member] | Residential Mortgage-Backed Securities [Member] | Structured Finance [Member]
Investment at fair value	16,671	16,930
Asset Pledged as Collateral [Member] | US Treasury Securities [Member]
Investment at fair value	78,430	79,680
Asset Pledged as Collateral [Member] | Repurchase Agreements [Member]
Accrued interest receivable	18,972	14,922
Restricted cash	11,185	0
Total	4,551,293	3,900,476
Asset Pledged as Collateral [Member] | Repurchase Agreements [Member] | Residential Mortgage-Backed Securities [Member] | Pass Through Certificate [Member]
Investment at fair value	4,504,465	3,868,624
Asset Pledged as Collateral [Member] | Repurchase Agreements [Member] | Residential Mortgage-Backed Securities [Member] | Structured Finance [Member]
Investment at fair value	16,671	16,930
Asset Pledged as Collateral [Member] | Repurchase Agreements [Member] | US Treasury Securities [Member]
Investment at fair value	0	0
Asset Pledged as Collateral [Member] | Derivative [Member]
Accrued interest receivable	0	0
Restricted cash	4,783	28,396
Total	83,213	108,076
Asset Pledged as Collateral [Member] | Derivative [Member] | Residential Mortgage-Backed Securities [Member] | Pass Through Certificate [Member]
Investment at fair value	0	0
Asset Pledged as Collateral [Member] | Derivative [Member] | Residential Mortgage-Backed Securities [Member] | Structured Finance [Member]
Investment at fair value	0	0
Asset Pledged as Collateral [Member] | Derivative [Member] | US Treasury Securities [Member]
Investment at fair value	$ 78,430	$ 79,680