Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 27, 2020	Jun. 29, 2019	Jun. 27, 2020	Jun. 29, 2019
Income Statement [Abstract]
Revenues	$ 319,247	$ 301,434	$ 607,527	$ 549,323
Costs and expenses:
Operating	191,060	187,778	389,453	353,794
Selling	51,972	50,629	102,084	96,933
General and administrative	19,044	18,671	40,586	37,715
Depreciation and amortization	14,124	14,590	28,728	28,802
Gain on sale of assets, net	(1,264)	(516)	(1,569)	(1,169)
Total costs and expenses	274,936	271,152	559,282	516,075
Income from operations	44,311	30,282	48,245	33,248
Other income (expense):
Interest expense	(1,952)	(2,428)	(3,898)	(4,579)
Interest income	96	93	197	176
Other, net	(1,152)	(3,153)	(3,051)	(4,808)
Income before income taxes	41,303	24,794	41,493	24,037
Income taxes	11,518	5,047	11,535	4,783
Net income	$ 29,785	$ 19,747	$ 29,958	$ 19,254
Net income per share:
Basic	$ 1.31	$ 0.86	$ 1.30	$ 0.83
Diluted	$ 1.24	$ 0.82	$ 1.24	$ 0.80
Weighted-average shares outstanding:
Basic	22,807	22,915	22,997	23,139
Diluted	23,983	24,051	24,077	24,180