Note 4 - Repurchase Agreements (Details Textual) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Securities Sold under Agreements to Repurchase	$ 4,426,947	$ 3,378,445
Restricted Cash and Cash Equivalents, Current	119,614	31,568
Repurchase Agreement Counterparty, Amount at Risk	207,600
Asset Pledged as Collateral [Member]
Restricted Cash and Cash Equivalents, Current	119,614	31,568
Asset Pledged as Collateral [Member] | Repurchase Agreements [Member]
Restricted Cash and Cash Equivalents, Current	113,347	13,341
Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Securities Sold under Agreements to Repurchase	$ 52,500	$ 190,300