Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional paid-in capital [Member]	Accumulated other comprehensive income (loss) [Member]	Retained earnings [Member]	Treasury Stock [Member]
Balance at Dec. 28, 2018	$ 313,909	$ 66	$ 227,283	$ (2,853)	$ 342,024	$ (252,611)
Balances (in shares) at Dec. 28, 2018		65,707				14,208
Employee stock purchase plan	845		687			$ 158
Employee stock purchase plan (in shares)						(15)
Amortization of unrecognized stock-based compensation	5,348		5,348
Foreign currency translation adjustments	(124)			(124)
Grant of restricted stock units to settle accrued bonus	7,947		7,947
Settlement of restricted stock units	(11,183)		(961)		(5,146)	$ (5,076)
Settlement of restricted stock units (in shares)						(405)
Unrealized gain (loss) on investments	403			403
Dividends and dividend equivalent rights	(16,999)		626		(17,625)
Net income	43,706				43,706
Balance at Jun. 28, 2019	343,852	$ 66	240,930	(2,574)	362,959	$ (257,529)
Balances (in shares) at Jun. 28, 2019		65,707				13,788
Balance at Dec. 28, 2018	313,909	$ 66	227,283	(2,853)	342,024	$ (252,611)
Balances (in shares) at Dec. 28, 2018		65,707				14,208
Unrealized gain (loss) on investments	373
Net income	63,339
Balance at Sep. 27, 2019	357,279	$ 66	242,756	(3,137)	374,033	$ (256,439)
Balances (in shares) at Sep. 27, 2019		65,707				13,682
Balance at Jun. 28, 2019	343,852	$ 66	240,930	(2,574)	362,959	$ (257,529)
Balances (in shares) at Jun. 28, 2019		65,707				13,788
Employee stock purchase plan	389		328			$ 61
Employee stock purchase plan (in shares)						(6)
Exercise of stock options	735		(294)			$ 1,029
Exercise of stock options (in shares)						(100)
Amortization of unrecognized stock-based compensation	1,748		1,748
Foreign currency translation adjustments	(533)			(533)
Unrealized gain (loss) on investments	(30)			(30)
Dividends and dividend equivalent rights	(8,515)		44		(8,559)
Net income	19,633				19,633
Balance at Sep. 27, 2019	357,279	$ 66	242,756	(3,137)	374,033	$ (256,439)
Balances (in shares) at Sep. 27, 2019		65,707				13,682
Balance at Jan. 03, 2020	350,251	$ 66	244,935	(1,760)	384,668	$ (277,658)
Balances (in shares) at Jan. 03, 2020		65,707				13,951
Employee stock purchase plan	905		774			$ 131
Employee stock purchase plan (in shares)						(13)
Exercise of stock options	1,628		454			$ 1,174
Exercise of stock options (in shares)						(114)
Amortization of unrecognized stock-based compensation	5,758		5,758
Purchase of treasury stock	(40,049)					$ (40,049)
Purchase of treasury stock (in shares)						636
Foreign currency translation adjustments	(1,602)			(1,602)
Grant of restricted stock units to settle accrued bonus	8,645		8,645
Settlement of restricted stock units	(15,263)		(1,460)		(4,538)	$ (9,265)
Settlement of restricted stock units (in shares)						(376)
Unrealized gain (loss) on investments	(43)			(43)
Dividends and dividend equivalent rights	(20,291)		511		(20,802)
Net income	42,628				42,628
Balance at Jul. 03, 2020	332,567	$ 66	259,617	(3,405)	401,956	$ (325,667)
Balances (in shares) at Jul. 03, 2020		65,707				14,084
Balance at Jan. 03, 2020	350,251	$ 66	244,935	(1,760)	384,668	$ (277,658)
Balances (in shares) at Jan. 03, 2020		65,707				13,951
Unrealized gain (loss) on investments	(172)
Net income	60,712
Balance at Oct. 02, 2020	343,197	$ 66	261,713	(2,984)	409,995	$ (325,593)
Balances (in shares) at Oct. 02, 2020		65,707				14,077
Balance at Jul. 03, 2020	332,567	$ 66	259,617	(3,405)	401,956	$ (325,667)
Balances (in shares) at Jul. 03, 2020		65,707				14,084
Employee stock purchase plan	479		405			$ 74
Employee stock purchase plan (in shares)						(7)
Amortization of unrecognized stock-based compensation	1,691		1,691
Foreign currency translation adjustments	550			550
Unrealized gain (loss) on investments	(129)			(129)
Dividends and dividend equivalent rights	(10,045)				(10,045)
Net income	18,084				18,084
Balance at Oct. 02, 2020	$ 343,197	$ 66	$ 261,713	$ (2,984)	$ 409,995	$ (325,593)
Balances (in shares) at Oct. 02, 2020		65,707				14,077