Note 6 - Pledged Assets - Schedule of Financial Instruments Owned and Pledged as Collateral (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Accrued interest receivable	$ 31,518	$ 23,044
Restricted cash	3,703	25,723
Asset Pledged as Collateral [Member]
Accrued interest receivable	31,326	22,852
Restricted cash	3,703	25,723
Total	6,848,601	5,358,194
Asset Pledged as Collateral [Member] | Residential Mortgage-Backed Securities [Member] | Pass Through Certificate [Member]
Investment at fair value	6,677,907	5,193,570
Asset Pledged as Collateral [Member] | Residential Mortgage-Backed Securities [Member] | Structured Finance [Member]
Investment at fair value	15,084	15,498
Asset Pledged as Collateral [Member] | US Treasury Securities [Member]
Investment at fair value	120,581	100,551
Asset Pledged as Collateral [Member] | Repurchase Agreements [Member]
Accrued interest receivable	30,163	22,852
Restricted cash	2,812	22,818
Total	6,725,966	5,254,738
Asset Pledged as Collateral [Member] | Repurchase Agreements [Member] | Residential Mortgage-Backed Securities [Member] | Pass Through Certificate [Member]
Investment at fair value	6,677,907	5,193,570
Asset Pledged as Collateral [Member] | Repurchase Agreements [Member] | Residential Mortgage-Backed Securities [Member] | Structured Finance [Member]
Investment at fair value	15,084	15,498
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	1,163	0
Restricted cash	891	2,905
Total	122,635	103,456
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	$ 120,581	$ 100,551