Note 6 - Net Income Per Share - Net Income Per Share Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	2 Months Ended	3 Months Ended		9 Months Ended
	Sep. 03, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net income	$ 31,568	$ 31,568	$ 23,642	$ 77,630	$ 53,132
Weighted-average shares outstanding, basic (in shares)		42,362	41,458	42,173	41,276
Effect of dilutive securities (in shares)		2,307	2,028	2,277	2,108
Weighted-average shares outstanding, diluted (in shares)		44,669	43,486	44,450	43,384
Earnings per share, basic (in dollars per share)		$ 0.75	$ 0.57	$ 1.84	$ 1.29
Earnings per share, diluted (in dollars per share)		$ 0.71	$ 0.54	$ 1.75	$ 1.22