Note 10 - Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017
Net income	$ 42,326	$ 48,638	$ 78,354	$ 87,530
Basic (in shares)	25,004	22,822	24,671	22,785
Effect of dilutive securities (in shares)	397	201	415	220
Diluted (in shares)	25,401	23,023	25,086	23,005
Earnings Per Share:
Basic earnings per share (in dollars per share)	$ 1.69	$ 2.13	$ 3.18	$ 3.84
Diluted earnings per share (in dollars per share)	$ 1.67	$ 2.11	$ 3.12	$ 3.80