Note 3 - Repurchase Agreements (Details Textual) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Securities Sold under Agreements to Repurchase	$ 3,769,437	$ 3,378,445
Restricted Cash and Cash Equivalents, Current	42,738	31,568
Repurchase Agreement Counterparty, Amount at Risk	193,200
Asset Pledged as Collateral [Member]
Restricted Cash and Cash Equivalents, Current	42,738	31,568
Asset Pledged as Collateral [Member] | Repurchase Agreements [Member]
Restricted Cash and Cash Equivalents, Current	18,072	13,341
Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Securities Sold under Agreements to Repurchase	$ 255,200	$ 190,300