Note 4 - Fair Value Measurements - Fair Value of Assets and Liabilities Measured On Recurring Basis (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Cash and cash equivalents	$ 20,933	$ 25,028
Restricted cash equivalents	25	25
Restricted cash equivalents	25	25
Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents	20,933	25,028
Restricted cash equivalents	25	25
Restricted cash equivalents	25	25
Fair Value, Inputs, Level 2 [Member]
Cash and cash equivalents
Restricted cash equivalents
Restricted cash equivalents
Fair Value, Inputs, Level 3 [Member]
Cash and cash equivalents
Restricted cash equivalents
Restricted cash equivalents