Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues
Total revenues	$ 158,277	$ 144,435	$ 144,844
Cost of revenues
Labor and other operating expenses	99,207	96,558	94,124
Depreciation, depletion and amortization	17,394	17,391	16,340
Total cost of revenues	116,601	113,949	110,464
Gross profit	41,676	30,486	34,380
Selling, general and administrative expenses	11,500	10,484	10,153
Impairment of long-lived assets	930
Operating profit	29,246	20,002	24,227
Other expense (income)
Interest expense	244	243	241
Interest and other income, net	(1,898)	(1,809)	(957)
Total other (income) expense	(1,654)	(1,566)	(716)
Income before income tax expense (benefit)	30,900	21,568	24,943
Income tax expense (benefit)	4,844	1,883	(2,205)
Net income	$ 26,056	$ 19,685	$ 27,148
Net income per share of common stock
Basic (in dollars per share)	$ 4.64	$ 3.52	$ 4.87
Diluted (in dollars per share)	$ 4.64	$ 3.51	$ 4.86