Note 5 - Derivative and Other Hedging Instruments - Schedule of Derivative Instruments Gain (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Gains on derivative instruments	$ 45,237	$ 452,476	$ 26,492
Treasury Note Future [Member] | Short [Member]
Gains on derivative instruments	32,650	206,907	(1,026)
Interest Rate Swap [Member]
Gains on derivative instruments	19,657	167,641	23,398
Payer Swaptions [Member] | Short [Member]
Gains on derivative instruments	(8,734)	152,365	(2,580)
Payer Swaptions [Member] | Long [Member]
Gains on derivative instruments	4,113	(81,050)	9,062
Interest Rate Cap [Member]
Gains on derivative instruments	(219)	919	0
Interest Rate Floor [Member] | Short [Member]
Gains on derivative instruments	1,785	0	2,765
Interest Rate Floor [Member] | Long [Member]
Gains on derivative instruments	(525)	0	0
TBA Contracts [Member] | Short [Member]
Gains on derivative instruments	1,370	4,494	3,432
TBA Contracts [Member] | Long [Member]
Gains on derivative instruments	$ (4,860)	$ 1,200	$ (8,559)