CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net income	$ 31,816	$ 34,098	$ 25,538
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	14,875	14,617	15,132
Amortization of deferred loan costs	538	538	538
Stock-based compensation	8,203	5,468	7,091
Provisions for bad debts	189	93	103
Loss on disposition of assets		12	4
Deferred income taxes	1,344	(483)	3,810
Changes in operating assets and liabilities:
Receivables	1,093	92	(1,992)
Income taxes	94	1,729	(1,600)
Inventories	(3,043)	(357)	(238)
Prepaid expenses	(730)	(896)	(125)
Right of use asset, net	14
Accounts payable	5,855	2,998	(431)
Accrued expenses	2,998	847	1,624
Net cash provided by operating activities	63,246	58,756	49,454
Cash flows from investing activities:
Proceeds from sale of assets	72		86
Change in construction payable	(9,624)	11,329	3,218
Acquisition of property and equipment	(125,367)	(137,074)	(49,990)
Net cash used in investing activities	(134,919)	(125,745)	(46,686)
Cash flows from financing activities:
Principal payments on long-term debt	(3,750)
Long-term debt borrowings	105,500	68,300
Net cash provided by financing activities	101,750	68,300
Change in cash and cash equivalents	30,077	1,311	2,768
Cash and cash equivalents at beginning of period	30,462	29,151	26,383
Cash and cash equivalents at end of period	60,539	30,462	29,151
Supplemental disclosure of cash flow information:
Cash paid for interest, net of amounts capitalized		186	426
Cash paid for income taxes	$ 6,322	7,305	11,950
Accounts payable			(105)
Accrued expenses			$ (13)
Accrued expenses - adjustment to beginning retained earnings for accounting changes in accordance with the new revenue recognition standard		$ 4,858