Note 6 - Pledged Assets - Schedule of Financial Instruments Owned and Pledged as Collateral (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Accrued interest receivable	$ 22,868	$ 14,951
Restricted cash	11,612	28,396
Asset Pledged as Collateral [Member]
Accrued interest receivable	22,853	14,922
Restricted cash	11,612	28,396
Total	5,572,117	4,008,552
Asset Pledged as Collateral [Member] | Residential Mortgage-Backed Securities [Member] | Pass Through Certificate [Member]
Investment at fair value	5,422,450	3,868,624
Asset Pledged as Collateral [Member] | Residential Mortgage-Backed Securities [Member] | Structured Finance [Member]
Investment at fair value	15,735	16,930
Asset Pledged as Collateral [Member] | US Treasury Securities [Member]
Investment at fair value	99,467	79,680
Asset Pledged as Collateral [Member] | Repurchase Agreements [Member]
Accrued interest receivable	22,853	14,922
Restricted cash	9,172	0
Total	5,470,210	3,900,476
Asset Pledged as Collateral [Member] | Repurchase Agreements [Member] | Residential Mortgage-Backed Securities [Member] | Pass Through Certificate [Member]
Investment at fair value	5,422,450	3,868,624
Asset Pledged as Collateral [Member] | Repurchase Agreements [Member] | Residential Mortgage-Backed Securities [Member] | Structured Finance [Member]
Investment at fair value	15,735	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	2,440	28,396
Total	101,907	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	$ 99,467	$ 79,680