Consolidated Statements of Stockholders' Equity - USD ($) $ 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			65,707,000				14,208,000
Employee stock purchase plan	1,668			1,384			$ 284
Employee stock purchase plan (in shares)							(27,000)
Exercise of stock options	1,561			(141)			$ 1,702
Exercise of stock options (in shares)							166,000
Amortization of unrecognized stock-based compensation	8,710			8,710
Purchase of treasury shares	(21,957)						$ (21,957)
Purchase of treasury shares (in shares)							342,000
Foreign currency translation adjustments	145				145
Reclassification adjustment for currency translation adjustments on planned disposal of a subsidiary	601				601
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)							(406,000)
Unrealized gain (loss) on investments	347				347
Dividends and dividend equivalent rights	(33,957)			713		(34,670)
Net income	82,460					82,460
Balance at Jan. 03, 2020	350,251		$ 66	244,935	(1,760)	384,668	$ (277,658)
Balances (in shares) at Jan. 03, 2020			65,707,000				13,951,000
Employee stock purchase plan	1,791			1,536			$ 255
Employee stock purchase plan (in shares)							(24,000)
Exercise of stock options	4,940			1,996			$ 2,944
Exercise of stock options (in shares)							(284,000)
Amortization of unrecognized stock-based compensation	9,165			9,165
Purchase of treasury shares	(40,049)						$ (40,049)
Purchase of treasury shares (in shares)							636,000
Foreign currency translation adjustments	65				65
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)							(376,000)
Unrealized gain (loss) on investments	(237)				(237)
Dividends and dividend equivalent rights	(40,362)			511		(40,873)
Net income	82,552					82,552
Balance at Jan. 01, 2021	361,498		$ 66	265,328	(1,932)	421,809	$ (323,773)
Balances (in shares) at Jan. 01, 2021			65,707,000				13,903,000
Employee stock purchase plan	1,977			1,777			$ 200
Employee stock purchase plan (in shares)							(20,000)
Exercise of stock options	$ 1,134			657			$ 477
Exercise of stock options (in shares)	(48,000)	[1]					(48,000)
Amortization of unrecognized stock-based compensation	$ 9,296			9,296
Purchase of treasury shares	(7,000)						$ (7,000)
Purchase of treasury shares (in shares)							78,000
Foreign currency translation adjustments	14				14
Grant of restricted stock units to settle accrued bonus	7,637			7,637
Settlement of restricted stock units	(15,666)			(3,276)		(1,679)	$ (10,711)
Settlement of restricted stock units (in shares)							(322,000)
Unrealized gain (loss) on investments	(6)				(65)	59
Dividends and dividend equivalent rights	(43,021)					(43,021)
Net income	101,202					101,202
Balance at Dec. 31, 2021	$ 417,065		$ 66	$ 281,419	$ (1,983)	$ 478,370	$ (340,807)
Balances (in shares) at Dec. 31, 2021			65,707,000				13,591,000

[1] Does not include restricted stock or employee stock purchase plans.