Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues	$ 1,024,791	$ 915,958	$ 845,678
Costs and expenses:
Operating	665,388	587,333	541,486
Selling	184,388	167,934	152,106
General and administrative	67,462	59,403	58,293
Depreciation	54,914	50,702	47,284
Amortization of intangible assets	2,055	2,384	2,306
Gain on sale of assets, net	(5,106)	(3,989)	(4,664)
Costs and expenses	969,101	863,767	796,811
Income from operations	55,690	52,191	48,867
Other income (expense):
Interest expense	(7,039)	(4,886)	(4,393)
Interest income	350	292	255
Other	(11,505)	(9,603)	(7,485)
Income before income taxes	37,496	37,994	37,244
Income taxes	9,519	15,874	14,960
Net income	$ 27,977	$ 22,120	$ 22,284
Share data:
Earnings per share--basic	$ 1.15	$ 0.87	$ 0.85
Earnings per share--diluted	$ 1.10	$ 0.83	$ 0.82
Weighted-average shares outstanding:
Basic	24,388,738	25,557,468	26,212,040
Diluted	25,480,618	26,697,062	27,247,354
Dividends declared per share	$ 0.100	$ 0.100	$ 0.100