Note 4 - Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Total liabilities	$ 16,800	$ 14,200
Money market funds	108,859	137,340
Total assets	108,859	137,340
Contingent consideration liability	16,800	14,200
Fair Value, Inputs, Level 1 [Member]
Total liabilities
Money market funds	108,859	137,340
Total assets	108,859	137,340
Contingent consideration liability
Fair Value, Inputs, Level 2 [Member]
Total liabilities
Money market funds
Total assets
Contingent consideration liability
Fair Value, Inputs, Level 3 [Member]
Total liabilities	16,800	14,200
Money market funds
Total assets
Contingent consideration liability	$ 16,800	$ 14,200