Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues	$ 845,678	$ 821,904	$ 789,911
Costs and expenses:
Operating	541,486	528,899	508,677
Selling	152,106	144,234	140,027
General and administrative	61,789	59,798	54,970
Depreciation	47,284	44,677	40,970
Amortization of intangible assets	2,306	2,214	2,070
Gain on sale of assets, net	(4,664)	(2,026)	(806)
Costs and expenses	800,307	777,796	745,908
Income from operations	45,371	44,108	44,003
Other income (expense):
Interest expense	(4,393)	(3,355)	(2,948)
Interest income	255	249	295
Other	(3,989)	(5,744)	(3,050)
Income before income taxes	37,244	35,258	38,300
Income taxes	14,960	13,460	15,131
Net income	$ 22,284	$ 21,798	$ 23,169
Share data:
Earnings per share--basic	$ 1.70	$ 1.62	$ 1.68
Earnings per share--diluted	$ 1.64	$ 1.56	$ 1.63
Weighted-average shares outstanding:
Basic	13,106,020	13,465,449	13,821,223
Diluted	13,623,677	13,977,290	14,238,276
Dividends declared per share	$ 0.200	$ 0.200	$ 0.185