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	372		302			$ 70
Employee stock purchase plan (in shares)						(7)
Amortization of unrecognized stock-based compensation	3,663		3,663
Foreign currency translation adjustments	117			117
Grant of restricted stock units to settle accrued bonus	7,947		7,947
Settlement of restricted stock units	(11,194)		(860)		(5,146)	$ (5,188)
Settlement of restricted stock units (in shares)						(395)
Unrealized gain (loss) on investments	154			154
Dividends and dividend equivalent rights	(8,503)		581		(9,084)
Net income	22,712				22,712
Balance at Mar. 29, 2019	329,177	$ 66	238,916	(2,582)	350,506	$ (257,729)
Balances (in shares) at Mar. 29, 2019		65,707				13,806
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	403
Net income	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 Mar. 29, 2019	329,177	$ 66	238,916	(2,582)	350,506	$ (257,729)
Balances (in shares) at Mar. 29, 2019		65,707				13,806
Employee stock purchase plan	473		385			$ 88
Employee stock purchase plan (in shares)						(8)
Amortization of unrecognized stock-based compensation	1,685		1,685
Foreign currency translation adjustments	(241)			(241)
Settlement of restricted stock units	11		(101)			$ 112
Settlement of restricted stock units (in shares)						(10)
Unrealized gain (loss) on investments	249			249
Dividends and dividend equivalent rights	(8,496)		45		(8,541)
Net income	20,994				20,994
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 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	473		400			$ 73
Employee stock purchase plan (in shares)						(7)
Exercise of stock options	672		64			$ 608
Exercise of stock options (in shares)						(60)
Amortization of unrecognized stock-based compensation	4,095		4,095
Purchase of treasury stock	(40,049)					$ (40,049)
Purchase of treasury stock (in shares)						636
Foreign currency translation adjustments	(1,673)			(1,673)
Grant of restricted stock units to settle accrued bonus	8,645		8,645
Settlement of restricted stock units	(15,112)		(1,261)		(4,538)	$ (9,313)
Settlement of restricted stock units (in shares)						(359)
Unrealized gain (loss) on investments	168			168
Dividends and dividend equivalent rights	(10,255)		511		(10,766)
Net income	26,282				26,282
Balance at Apr. 03, 2020	323,497	$ 66	257,389	(3,265)	395,646	$ (326,339)
Balances (in shares) at Apr. 03, 2020		65,707				14,161
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	(43)
Net income	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 Apr. 03, 2020	323,497	$ 66	257,389	(3,265)	395,646	$ (326,339)
Balances (in shares) at Apr. 03, 2020		65,707				14,161
Employee stock purchase plan	432		374			$ 58
Employee stock purchase plan (in shares)						(6)
Exercise of stock options	956		390			$ 566
Exercise of stock options (in shares)						(54)
Amortization of unrecognized stock-based compensation	1,663		1,663
Foreign currency translation adjustments	71			71
Settlement of restricted stock units	(151)		(199)			$ 48
Settlement of restricted stock units (in shares)						(17)
Unrealized gain (loss) on investments	(211)			(211)
Dividends and dividend equivalent rights	(10,036)				(10,036)
Net income	16,346				16,346
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