Note 2 - Cash, Cash Equivalents and Restricted Cash (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Average Reserve Balances Required to be Maintained with Federal Bank	$ 0	$ 60
Average Excess Balances Maintained With Federal Reserve Bank	1,609,700	874,800
Margin Deposit Assets	24,300	34,700
Restricted Cash, Total	689,900	9,300
Bank [Member]
Restricted Cash, Total	$ 5,900	$ 11,900