Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Total
Balance, at Dec. 27, 2014	$ 9,949	$ 980,842	$ 4,829	$ (150,857)	$ 844,763
Balance, shares at Dec. 27, 2014	33,047,807			6,149,364
Net income	$ 0	59,330	0	$ 0	59,330
Other comprehensive income (loss), net of reclassification adjustments and tax	0	0	(68)	0	(68)
Dividends paid	0	(32,278)	0	0	(32,278)
Balance, at Dec. 26, 2015	$ 9,949	1,007,894	4,761	$ (150,857)	871,747
Balance, shares at Dec. 26, 2015	33,047,807			6,149,364
Net income	$ 0	87,162	0	$ 0	87,162
Other comprehensive income (loss), net of reclassification adjustments and tax	0	0	91	0	91
Dividends paid	0	(32,278)	0	0	(32,278)
Balance, at Dec. 31, 2016	$ 9,949	1,062,778	4,852	$ (150,857)	$ 926,722
Balance, shares at Dec. 31, 2016	33,047,807			6,149,364
Treasury Stock, Shares					6,149,364
Net income	$ 0	98,414	0	$ 0	$ 98,414
Other comprehensive income (loss), net of reclassification adjustments and tax	0	0	(14)	0	(14)
Other comprehensive income tax reform adjustment	0	(1,042)	1,042	0	0
Dividends paid	0	(32,278)	0	0	(32,278)
Balance, at Dec. 30, 2017	$ 9,949	$ 1,127,872	$ 5,880	$ (150,857)	$ 992,844
Balance, shares at Dec. 30, 2017	33,047,807			6,149,364
Treasury Stock, Shares					6,149,364