Note 6 - Pledged Assets - Schedule of Financial Instruments Owned and Pledged as Collateral (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Accrued interest receivable	$ 53,880	$ 49,127
Restricted cash	86,114	58,696
Asset Pledged as Collateral [Member]
Accrued interest receivable	53,436	48,573
Restricted cash	86,114	58,696
Total	11,548,184	10,745,145
Asset Pledged as Collateral [Member] | Residential Mortgage-Backed Securities [Member] | Pass Through Certificate [Member]
Investment at fair value	11,246,597	10,489,655
Asset Pledged as Collateral [Member] | Residential Mortgage-Backed Securities [Member] | Structured Finance [Member]
Investment at fair value	12,452	13,088
Asset Pledged as Collateral [Member] | US Treasury Securities [Member]
Investment at fair value	149,585	135,133
Asset Pledged as Collateral [Member] | Repurchase Agreements [Member]
Accrued interest receivable	51,934	48,537
Restricted cash	82,612	51,171
Total	11,393,595	10,602,451
Asset Pledged as Collateral [Member] | Repurchase Agreements [Member] | Residential Mortgage-Backed Securities [Member] | Pass Through Certificate [Member]
Investment at fair value	11,246,597	10,489,655
Asset Pledged as Collateral [Member] | Repurchase Agreements [Member] | Residential Mortgage-Backed Securities [Member] | Structured Finance [Member]
Investment at fair value	12,452	13,088
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	1,502	36
Restricted cash	3,502	7,525
Total	154,589	142,694
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	$ 149,585	$ 135,133