Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock Common Class A	Common Stock Common Class B	Additional Paid-in Capital	Accumulated Other Comprehensive (Loss) Income, net of tax	Retained Earnings
Balance (in shares) at Dec. 27, 2014		9,452,000	3,617,000
Balance at Dec. 27, 2014	$ 436,140	$ 95	$ 36	$ 224,909	$ (1,133)	$ 212,233
Net income	98,414					98,414
Stock options exercised and restricted shares activities, including tax benefit (in shares)		303,000
Stock options exercised and restricted shares activities, including tax benefit	58,525	$ 3		58,522
Stock-based compensation expense	$ 6,665			6,665
Repurchase of Class A Common Stock (in shares)	(616,747)	(616,000)
Repurchase of Class A Common Stock	$ (138,705)	$ (6)				(138,699)
Conversion from Class B to Class A (in shares)		250,000	(250,000)
Conversion from Class B to Class A		$ 2	$ (2)
Defined benefit plans liability adjustment, net of tax	204				204
Currency translation adjustment	(22)				(22)
Balance (in shares) at Dec. 26, 2015		9,389,000	3,367,000
Balance at Dec. 26, 2015	461,221	$ 94	$ 34	290,096	(951)	171,948
Net income	87,349					87,349
Stock options exercised and restricted shares activities, including tax benefit (in shares)		557,000
Stock options exercised and restricted shares activities, including tax benefit	53,674	$ 5		53,669
Stock-based compensation expense	$ 6,148			6,148
Repurchase of Class A Common Stock (in shares)	(944,876)	(945,000)
Repurchase of Class A Common Stock	$ (161,658)	$ (9)				(161,649)
Conversion from Class B to Class A (in shares)		170,000	(170,000)
Conversion from Class B to Class A		$ 2	$ (2)
Defined benefit plans liability adjustment, net of tax	(53)				(53)
Currency translation adjustment	(99)				(99)
Balance (in shares) at Dec. 31, 2016		9,171,000	3,197,000
Balance at Dec. 31, 2016	446,582	$ 92	$ 32	349,913	(1,103)	97,648
Net income	$ 99,049					99,049
Stock options exercised and restricted shares activities, including tax benefit (in shares)	194,401	217,000
Stock options exercised and restricted shares activities, including tax benefit	$ 16,363	$ 2		16,361
Stock-based compensation expense	$ 6,316			6,316
Repurchase of Class A Common Stock (in shares)	(963,790)	(964,000)
Repurchase of Class A Common Stock	$ (144,602)	$ (10)				(144,592)
Conversion from Class B to Class A (in shares)		179,000	(179,000)
Conversion from Class B to Class A		$ 2	$ (2)
Defined benefit plans liability adjustment, net of tax	(202)				(202)
Currency translation adjustment	17				17
Balance (in shares) at Dec. 30, 2017		8,603,000	3,018,000
Balance at Dec. 30, 2017	$ 423,523	$ 86	$ 30	$ 372,590	$ (1,288)	$ 52,105