Note 2 - Fair Value Measurement - Financial Assets on Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Contingent consideration - business combinations	$ 0	$ 0
Fair Value, Inputs, Level 2 [Member]
Total cash and cash equivalents	0	0
Fair Value, Inputs, Level 3 [Member]
Total cash and cash equivalents	0	0
Fair Value, Recurring [Member]
Total cash and cash equivalents	19,617	30,657
Contingent consideration - business combinations	1,931
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Total cash and cash equivalents	19,617	30,657
Contingent consideration - business combinations
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Total cash and cash equivalents
Contingent consideration - business combinations
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Total cash and cash equivalents
Contingent consideration - business combinations	$ 1,931