Note 10 - Derivative Financial Instruments (Details Textual) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Foreign Exchange Forward [Member]
Derivative, Notional Amount	$ 0	$ 0
Eurodollar Future [Member]
Derivative, Notional Amount	0	0
TBA and Other Forward MBS [Member] | Long [Member]
Derivative, Notional Amount	1,706,834	1,773,000
TBA and Other Forward MBS [Member] | Short [Member]
Derivative, Notional Amount	1,809,550	1,874,194
Other Extended Settlement Trade [Member] | Long [Member]
Derivative, Notional Amount		$ 1,526
Other Extended Settlement Trade [Member] | Short [Member]
Derivative, Notional Amount	$ 365