Note 5 - Cash, Cash Equivalents and Restricted Cash (Details Textual) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2020
Average Reserve Balances Required to be Maintained with Federal Bank	$ 0	$ 0
Average Excess Balances Maintained With Federal Reserve Bank	1,600,000	1,600,000
Margin Deposit Assets	3,300	24,300
Restricted Cash, Total	$ 0	690
Bank [Member]
Restricted Cash, Total		$ 5,900	$ 2,200