Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Cash flows from operating activities:
Net income	$ 6,300	$ 10,382
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	9,324	9,023
Amortization of deferred loan costs	152	153
Stock-based compensation	576	523
Excess tax benefit from stock-based compensation	(395)
Provision (recoveries) of bad debts	34	(83)
Loss (gain) on disposal of assets	249	(22)
Changes in operating assets and liabilities:
Receivables	(745)	245
Inventories	249	112
Prepaid expenses	(458)	152
Accounts payable	(744)	7
Accrued expenses	(1,206)	(1,193)
Income taxes	770	(261)
Net cash provided by operating activities	14,106	19,038
Cash flows from investing activities:
Proceeds from sale of assets	75	22
Change in construction payable	119
Acquisition of property and equipment	(9,498)	(5,342)
Net cash used in investing activities	(9,304)	(5,320)
Cash flows from financing activities:
Net exercise of stock options	(2,461)	1,308
Excess tax benefit from stock-based compensation	395
Principal payments on long-term debt	(4,900)	(16,300)
Net cash used in financing activities	(6,966)	(14,992)
Net decrease in cash	(2,164)	(1,274)
Cash and cash equivalents at beginning of period	19,330	19,043
Cash and cash equivalents at end of period	17,166	17,769
Supplemental disclosure of cash flow information:
Cash paid for interest	447	927
Cash paid for income taxes	$ 2,850	$ 6,150