Note 10 - Derivative Financial Instruments - Statement of Operations Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative net gain (loss)	$ 5,324	$ 6,526	$ 6,200
Foreign Exchange Forward [Member] | Principal Transactions and Other Income [Member]
Derivative net gain (loss)		51	87
Other Extended Settlement Trade [Member] | Principal Transactions and Other Income [Member]
Derivative net gain (loss)		(70)	60
TBA and Other Forward MBS [Member] | Net Trading [Member]
Derivative net gain (loss)	5,219	6,545	6,053
Derivatives, Publicity Traded Options [Member] | Other Investments Sold, Not Yet Purchased [Member]
Derivative net gain (loss)	$ 105