Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock Common Class A	Common Stock Common Class B	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment
Balance at Dec. 28, 2019	$ 735,636		$ 94	$ 27	$ 571,784	$ (1,669)	$ 165,400
Balance (in shares) at Dec. 28, 2019			9,371,000	2,673,000
Net income	18,234						18,234
Stock options exercised and restricted shares activities	1,858				1,858
Stock options exercised and restricted shares activities (in shares)			38,000
Stock-based compensation expense	2,566				2,566
Conversion from Class B to Class A			$ 2	$ (2)
Conversion from Class B to Class A (in shares)			150,000	(150,000)
Foreign currency translation adjustment	(58)					(58)
Balance at Mar. 28, 2020	758,236		$ 96	$ 25	576,208	(1,727)	183,634
Balance (in shares) at Mar. 28, 2020			9,559,000	2,523,000
Balance at Dec. 26, 2020	956,967	$ (54)	$ 100	$ 22	599,737	(252)	357,360	$ (54)
Balance (in shares) at Dec. 26, 2020			10,005,000	2,178,000
Net income	65,565						65,565
Stock options exercised and restricted shares activities	$ 1,269		$ 1		1,268
Stock options exercised and restricted shares activities (in shares)	31,020		48,000
Stock-based compensation expense	$ 4,957				4,957
Accounting Standards Update [Extensible List]		ASU 2019-12						ASU 2019-12
Foreign currency translation adjustment	20					20
Balance at Mar. 27, 2021	$ 1,028,724		$ 101	$ 22	$ 605,962	$ (232)	$ 422,871
Balance (in shares) at Mar. 27, 2021			10,053,000	2,178,000