Note 1 - Summary of Significant Accounting Policies - Adjustments to Retained Earnings (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net sales	$ 95,001	$ 95,870	$ 82,392	$ 73,087	$ 72,450	$ 67,773	$ 65,604	$ 60,987	$ 64,686	$ 65,282	$ 64,660	$ 57,968	$ 346,350	$ 266,814	$ 252,596
Cost of goods sold													224,653	170,462	165,614
Selling and administrative expenses													96,710	70,592	65,124
Income before taxes on income													21,395	24,782	19,898
Income tax expense					5,000								4,420	9,760	$ 5,260
Adjustment to opening retained earnings	103,032				$ 83,129								103,032	$ 83,129
Accounting Standards Update 2014-09 [Member]
Net sales													42,880
Cost of goods sold													27,397
Selling and administrative expenses													706
Income before taxes on income													14,777
Income tax expense													3,532
Adjustment to opening retained earnings	$ 11,245												$ 11,245