Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating Activities:
Net income	$ 11,387	$ 10,575
Noncash items included in net income:
Depreciation and amortization	20,087	17,243
Other, net	5,411	1,701
Changes in operating assets and liabilities, net	(12,757)	(12,563)
Net cash provided by operating activities	24,128	16,956
Investing Activities:
Acquisition of property and equipment	(88,388)	(53,995)
Proceeds from disposal of property and equipment	607	367
Net cash used in investing activities	(87,781)	(53,628)
Financing Activities:
Repayment of revolving credit agreement	(15,441)	(26,738)
Borrowing of revolving credit agreement	80,624	65,564
Proceeds from stock option exercises	1,288
Shares withheld for taxes	(1,211)	(650)
Repayment of capital leases	(2,435)	(1,390)
Net cash provided by financing activities	62,825	36,786
Net Increase (Decrease) in Cash and Cash Equivalents	(828)	114
Cash and cash equivalents, beginning of period	1,539	124
Cash and cash equivalents, end of period	711	238
Non Cash Investing Activities
Equipment financed with capital leases	$ 20,369	$ 10,032