Note 3 - Repurchase Agreements (Details Textual) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Securities Sold under Agreements to Repurchase, Total	$ 3,378,445	$ 6,244,106
Restricted Cash and Cash Equivalents, Current, Total	31,568	65,299
Repurchase Agreement Counterparty, Amount at Risk	149,800
Asset Pledged as Collateral [Member]
Restricted Cash and Cash Equivalents, Current, Total	31,568	65,299
Asset Pledged as Collateral [Member] | Repurchase Agreements [Member]
Restricted Cash and Cash Equivalents, Current, Total	13,341	$ 57,264
Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Securities Sold under Agreements to Repurchase, Total	$ 190,300