Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2020	Sep. 28, 2019	Sep. 26, 2020	Sep. 28, 2019
Income Statement [Abstract]
Revenues	$ 337,453	$ 307,473	$ 944,980	$ 856,796
Costs and expenses:
Operating	208,510	193,137	597,963	546,931
Selling	60,203	56,921	162,287	153,854
General and administrative	19,891	19,895	60,477	57,610
Depreciation and amortization	13,825	15,319	42,553	44,121
Gain on sale of assets, net	(476)	(582)	(2,045)	(1,751)
Total costs and expenses	301,953	284,690	861,235	800,765
Income from operations	35,500	22,783	83,745	56,031
Other income (expense):
Interest expense	(1,579)	(2,018)	(5,477)	(6,597)
Interest income	1,688	94	1,885	270
Other, net	(1,499)	(1,886)	(4,550)	(6,694)
Income before income taxes	34,110	18,973	75,603	43,010
Income taxes	9,483	5,539	21,018	10,322
Net income	$ 24,627	$ 13,434	$ 54,585	$ 32,688
Net income per share:
Basic	$ 1.08	$ 0.59	$ 2.38	$ 1.43
Diluted	$ 1.03	$ 0.56	$ 2.27	$ 1.37
Weighted-average shares outstanding:
Basic	22,874	22,793	22,956	22,830
Diluted	23,854	24,002	24,002	23,927