Note 4 - Cash, Cash Equivalents and Restricted Cash (Details Textual) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Average Reserve Balances Required to be Maintained with Federal Bank	$ 0	$ 60
Margin Deposit Assets	30,800	34,700
Restricted Cash, Total	4,200	9,300
Bank [Member]
Margin Deposit Assets	$ 10,000	$ 11,900