Note 4 - Supplemental Cash Flow Information (Details Textual) - USD ($) $ in Thousands		3 Months Ended
	Jan. 01, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Income Taxes Paid		$ 400	$ 100
Interest Paid, Including Capitalized Interest, Operating and Investing Activities, Total		$ 200	$ 100
Company Stock Received in Lieu of Cash Stock Options Exercised		5,863	16,500
Stock Issued During Period, Shares, New Issues		20,234	41,544
Contract with Customer, Asset, Net, Current, Total	$ 43,300	$ 47,098
Increase (Decrease) in Inventories, Total		$ (3,742)	$ 1,078
Accounting Standards Update 2014-09 [Member]
Increase (Decrease) in Inventories, Total	(24,900)
Increase (Decrease) in Accounts Payable, Total	2,600
Increase (Decrease) in Other Current Liabilities	1,100
Increase (Decrease) in Deferred Income Taxes	$ (3,500)