Note 4 - Fair Value Measurements - Change in Fair Value of Contingent Consideration Liability (Details) - Contingent Consideration Liability [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Balance at beginning of period
Contingent consideration liability established in connection with the acquisition of Ambrell	4,123
Fair value adjustment	6,976
Transfer of contingent consideration liability to 2017 earnout payable	(5,355)
Balance at end of period	$ 5,744