Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 03, 2015	Sep. 27, 2014	Oct. 03, 2015	Sep. 27, 2014
Income Statement [Abstract]
Revenues	$ 224,981	$ 216,604	$ 624,046	$ 587,174
Costs and expenses:
Operating	143,173	138,991	400,372	378,505
Selling	40,086	37,179	107,656	102,051
General and administrative	13,480	12,407	42,146	39,211
Depreciation and amortization	12,169	11,071	34,437	31,439
Gain on sale of assets, net	(104)	(188)	(553)	(266)
Costs and expenses	208,804	199,460	584,058	550,940
Income from operations	16,177	17,144	39,988	36,234
Other income (expense):
Interest expense	(827)	(676)	(2,517)	(2,101)
Interest income	85	56	207	201
Other, net	(2,068)	(1,112)	(3,776)	(2,417)
Income before income taxes	13,367	15,412	33,902	31,917
Income taxes	5,193	5,755	13,324	12,225
Net income	$ 8,174	$ 9,657	$ 20,578	$ 19,692
Net income per share:
Basic	$ 0.58	$ 0.72	$ 1.53	$ 1.43
Diluted	$ 0.55	$ 0.69	$ 1.47	$ 1.39
Weighted-average shares outstanding:
Basic	14,144	13,428	13,442	13,745
Diluted	14,785	13,899	13,962	14,167
Dividends declared per share	$ 0.05	$ 0.05	$ 0.15	$ 0.14