Note 4 - Marketable Securities - Fair Value of Available for Sale Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Adjusted Cost	$ 51,948	$ 46,502
Unrealized Gains	0	0
Unrealized Losses	(2)	(8)
Fair Value	51,946	46,494
Cash and Cash Equivalents	46,905	36,566
Current Marketable Securities	5,041	9,928
Cash [Member]
Adjusted Cost	46,905	31,558
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	46,905	31,558
Cash and Cash Equivalents	46,905	31,558
Current Marketable Securities	0	0
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Adjusted Cost	5,043	4,923
Unrealized Gains	0	0
Unrealized Losses	(2)	(8)
Fair Value	5,041	4,915
Cash and Cash Equivalents	0	0
Current Marketable Securities	$ 5,041	4,915
Bank Time Deposits [Member] | Fair Value, Inputs, Level 2 [Member]
Adjusted Cost		10,021
Unrealized Gains		0
Unrealized Losses		0
Fair Value		10,021
Cash and Cash Equivalents		5,008
Current Marketable Securities		$ 5,013