CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net income	$ 12,111	$ 10,270
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	7,675	7,490
Amortization of deferred loan costs	269	153
Stock-based compensation	2,163	550
Excess tax benefit from stock-based compensation		(285)
Provision for bad debts	37	26
Loss (gain) on disposition of assets	4	663
Changes in operating assets and liabilities:
Receivables	928	(100)
Inventories	(94)	(17)
Prepaid expenses	612	(367)
Accounts payable	(1,439)	1,255
Accrued expenses	(2,729)	(1,282)
Income taxes	(1,235)	(1,228)
Net cash provided by operating activities	18,302	17,128
Cash flows from investing activities:
Proceeds from sale of assets	86	20
Change in construction payable	(104)	(1)
Acquisition of property and equipment	(20,449)	(14,828)
Net cash used in investing activities	(20,467)	(14,809)
Cash flows from financing activities:
Net exercise of stock options		1,428
Excess tax benefit from stock-based compensation		285
Principal payments on long-term debt		(5,900)
Net cash used in financing activities		(4,187)
Net increase (decrease) in cash	(2,165)	(1,868)
Cash and cash equivalents at beginning of period	26,383	21,164
Cash and cash equivalents at end of period	24,218	19,296
Supplemental disclosure of cash flow information
Cash paid for interest, net of amounts capitalized	209
Cash paid for income taxes	7,925	$ 6,650
Return of assets under capital lease [Abstract]
Accounts Payable	(105)
Accrued Expenses	$ (13)