Note 2 - Fair Value Measurement - Financial Assets on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Inputs, Level 2 [Member]
Total Cash and cash equivalents	$ 0	$ 0
Fair Value, Measurements, Recurring [Member]
Total Cash and cash equivalents	30,657	6,663
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Total Cash and cash equivalents	30,657	6,663
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Total Cash and cash equivalents