Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Apr. 01, 2017
Income Statement [Abstract]
Revenues	$ 208,651	$ 192,813
Costs and expenses:
Operating	144,623	133,659
Selling	39,657	35,534
General and administrative	17,718	16,400
Depreciation and amortization	13,121	12,190
Gain on sale of assets, net	(802)	(975)
Costs and expenses	214,317	196,808
Loss from operations	(5,666)	(3,995)
Other income (expense):
Interest expense	(1,401)	(1,257)
Interest income	78	70
Other, net	(1,662)	(1,139)
Loss before income taxes	(8,651)	(6,321)
Income tax benefits	(2,024)	(2,434)
Net loss	$ (6,627)	$ (3,887)
Net income per share:
Net loss per share--basic and diluted	$ (0.26)	$ (0.15)
Weighted-average shares outstanding:
Weighted-average shares outstanding--basic and diluted	25,418	25,175
Basic	25,418	25,175
Diluted	26,476	26,216
Dividends declared per share	$ 0.025	$ 0.025