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. 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
Net income	$ 0	98,414	0	$ 0	98,414
Other comprehensive income (loss), net of reclassification adjustments and tax	0	0	(14)	0	(14)
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
Cumulative effect of accounting principle adoption	$ 0	(1,042)	1,042	$ 0	0
Net income	0	62,738	0	0	62,738
Other comprehensive income (loss), net of reclassification adjustments and tax	0	0	(137)	0	(137)
Dividends paid	0	(32,546)	0	0	(32,546)
Balance, at Dec. 29, 2018	$ 9,949	1,163,545	262	$ (150,857)	1,022,899
Balance, shares at Dec. 29, 2018	33,047,807			6,149,364
Cumulative effect of accounting principle adoption	$ 0	5,481	(5,481)	$ 0	0
Net income	0	67,983	0	0	67,983
Other comprehensive income (loss), net of reclassification adjustments and tax	0	0	1,218	0	1,218
Dividends paid	0	(33,354)	0	0	(33,354)
Balance, at Dec. 28, 2019	$ 9,949	$ 1,198,173	$ 1,480	$ (150,857)	$ 1,058,745
Balance, shares at Dec. 28, 2019	33,047,807			6,149,364