Note 7 - Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 27, 2015	Jun. 28, 2014	Jun. 27, 2015	Jun. 28, 2014
Net income	$ 28,684	$ 24,578	$ 48,679	$ 49,967
Basic (in shares)	22,691	22,579	22,645	22,536
Net effect of dilutive stock options and restricted share units (in shares)	144	171	165	202
Average shares - Diluted (in shares)	22,835	22,750	22,810	22,738
Net income per share (see Note 7):
Basic (in dollars per share)	$ 1.26	$ 1.09	$ 2.15	$ 2.22
Diluted (in dollars per share)	$ 1.26	$ 1.08	$ 2.13	$ 2.20